zeph_config/migrate/

mod.rs

// SPDX-FileCopyrightText: 2026 Andrei G <bug-ops>
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Config migration: add missing parameters from the canonical reference as commented-out entries.
//!
//! The canonical reference is the checked-in `config/default.toml` file embedded at compile time.
//! Missing sections and keys are added as `# key = default_value` comments so users can discover
//! and enable them without hunting through documentation.

use toml_edit::{Array, DocumentMut, Item, Table, Value};

/// Canonical section ordering for top-level keys in the output document.
static CANONICAL_ORDER: &[&str] = &[
    "agent",
    "llm",
    "skills",
    "memory",
    "index",
    "tools",
    "mcp",
    "telegram",
    "discord",
    "slack",
    "a2a",
    "acp",
    "gateway",
    "metrics",
    "daemon",
    "scheduler",
    "orchestration",
    "classifiers",
    "security",
    "vault",
    "timeouts",
    "cost",
    "debug",
    "logging",
    "notifications",
    "tui",
    "agents",
    "experiments",
    "lsp",
    "telemetry",
    "session",
];

/// Error type for migration failures.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum MigrateError {
    /// Failed to parse the user's config.
    #[error("failed to parse input config: {0}")]
    Parse(#[from] toml_edit::TomlError),
    /// Failed to parse the embedded reference config (should never happen in practice).
    #[error("failed to parse reference config: {0}")]
    Reference(toml_edit::TomlError),
    /// The document structure is inconsistent (e.g. `[llm.stt].model` exists but `[llm]` table
    /// cannot be obtained as a mutable table — can happen when `[llm]` is absent or not a table).
    #[error("migration failed: invalid TOML structure — {0}")]
    InvalidStructure(&'static str),
}

/// Result of a migration operation.
#[derive(Debug)]
pub struct MigrationResult {
    /// The migrated TOML document as a string.
    pub output: String,
    /// Number of top-level keys or sub-keys modified (added or removed) during migration.
    pub changed_count: usize,
    /// Names of top-level sections that were modified (added or removed).
    pub sections_changed: Vec<String>,
}

/// Migrates a user config by adding missing parameters as commented-out entries.
///
/// The canonical reference is embedded from `config/default.toml` at compile time.
/// User values are never modified; only missing keys are appended as comments.
pub struct ConfigMigrator {
    reference_src: &'static str,
}

impl Default for ConfigMigrator {
    fn default() -> Self {
        Self::new()
    }
}

impl ConfigMigrator {
    /// Create a new migrator using the embedded canonical reference config.
    #[must_use]
    pub fn new() -> Self {
        Self {
            reference_src: include_str!("../../config/default.toml"),
        }
    }

    /// Migrate `user_toml`: add missing parameters from the reference as commented-out entries.
    ///
    /// # Errors
    ///
    /// Returns `MigrateError::Parse` if the user's TOML is invalid.
    /// Returns `MigrateError::Reference` if the embedded reference TOML cannot be parsed.
    ///
    /// # Panics
    ///
    /// Never panics in practice; `.expect("checked")` is unreachable because `is_table()` is
    /// verified on the same `ref_item` immediately before calling `as_table()`.
    pub fn migrate(&self, user_toml: &str) -> Result<MigrationResult, MigrateError> {
        let reference_doc = self
            .reference_src
            .parse::<DocumentMut>()
            .map_err(MigrateError::Reference)?;
        let mut user_doc = user_toml.parse::<DocumentMut>()?;

        let mut changed_count = 0usize;
        let mut sections_changed: Vec<String> = Vec::new();
        // Collected scalar/sub-table comment lines to insert after rendering.
        // Each entry: (section_key, comment_line).
        let mut pending_comments: Vec<(String, String)> = Vec::new();

        // Walk the reference top-level keys.
        for (key, ref_item) in reference_doc.as_table() {
            if ref_item.is_table() {
                let ref_table = ref_item.as_table().expect("is_table checked above");
                if user_doc.contains_key(key) {
                    // Section exists — merge missing sub-keys.
                    if let Some(user_table) = user_doc.get_mut(key).and_then(Item::as_table_mut) {
                        let (n, comments) =
                            merge_table_commented(user_table, ref_table, key, user_toml);
                        changed_count += n;
                        pending_comments.extend(comments);
                    }
                } else {
                    // Entire section is missing — record for textual append after rendering.
                    // Idempotency: skip if a commented block for this section was already appended.
                    if user_toml.contains(&format!("# [{key}]")) {
                        continue;
                    }
                    let commented = commented_table_block(key, ref_table);
                    if !commented.is_empty() {
                        sections_changed.push(key.to_owned());
                    }
                    changed_count += 1;
                }
            } else {
                // Top-level scalar/array key.
                if !user_doc.contains_key(key) {
                    let raw = format_commented_item(key, ref_item);
                    if !raw.is_empty() {
                        sections_changed.push(format!("__scalar__{key}"));
                        changed_count += 1;
                    }
                }
            }
        }

        // Render the user doc as-is first.
        let user_str = user_doc.to_string();

        // Insert collected scalar/sub-table comment lines via raw text operations.
        // This avoids toml_edit decor roundtrip loss — guards check the rendered string.
        let mut output = user_str;
        for (section_key, comment_line) in &pending_comments {
            if !section_body(&output, section_key).contains(comment_line.trim()) {
                output = insert_after_section(&output, section_key, comment_line);
            }
        }

        // Append missing sections as raw commented text at the end.
        for key in &sections_changed {
            if let Some(scalar_key) = key.strip_prefix("__scalar__") {
                if let Some(ref_item) = reference_doc.get(scalar_key) {
                    let raw = format_commented_item(scalar_key, ref_item);
                    if !raw.is_empty() {
                        output.push('\n');
                        output.push_str(&raw);
                        output.push('\n');
                    }
                }
            } else if let Some(ref_table) = reference_doc.get(key.as_str()).and_then(Item::as_table)
            {
                let block = commented_table_block(key, ref_table);
                if !block.is_empty() {
                    output.push('\n');
                    output.push_str(&block);
                }
            }
        }

        // Reorder top-level sections by canonical order.
        output = reorder_sections(&output, CANONICAL_ORDER);

        // Resolve sections_changed to only real section names (not scalars).
        let sections_changed_clean: Vec<String> = sections_changed
            .into_iter()
            .filter(|k| !k.starts_with("__scalar__"))
            .collect();

        Ok(MigrationResult {
            output,
            changed_count,
            sections_changed: sections_changed_clean,
        })
    }
}

/// Merge missing keys from `ref_table` into `user_table` as commented-out entries.
///
/// Returns `(count, comment_lines)` where `comment_lines` is a list of
/// `(section_key, comment_line)` pairs to be inserted into the rendered output.
/// Using raw-string insertion avoids `toml_edit` decor roundtrip loss.
fn merge_table_commented(
    user_table: &mut Table,
    ref_table: &Table,
    section_key: &str,
    user_toml: &str,
) -> (usize, Vec<(String, String)>) {
    let mut count = 0usize;
    let mut comments: Vec<(String, String)> = Vec::new();
    for (key, ref_item) in ref_table {
        if ref_item.is_table() {
            if user_table.contains_key(key) {
                let pair = (
                    user_table.get_mut(key).and_then(Item::as_table_mut),
                    ref_item.as_table(),
                );
                if let (Some(user_sub_table), Some(ref_sub_table)) = pair {
                    let sub_key = format!("{section_key}.{key}");
                    let (n, c) =
                        merge_table_commented(user_sub_table, ref_sub_table, &sub_key, user_toml);
                    count += n;
                    comments.extend(c);
                }
            } else if let Some(ref_sub_table) = ref_item.as_table() {
                // Sub-table missing from user config — collect as raw commented block.
                let dotted = format!("{section_key}.{key}");
                let marker = format!("# [{dotted}]");
                if !user_toml.contains(&marker) {
                    let block = commented_table_block(&dotted, ref_sub_table);
                    if !block.is_empty() {
                        comments.push((section_key.to_owned(), format!("\n{block}")));
                        count += 1;
                    }
                }
            }
        } else if ref_item.is_array_of_tables() {
            // Never inject array-of-tables entries — they are user-defined.
        } else {
            // Scalar/array value — check if already present (as value or as comment).
            if !user_table.contains_key(key) {
                let raw_value = ref_item
                    .as_value()
                    .map(value_to_toml_string)
                    .unwrap_or_default();
                if !raw_value.is_empty() {
                    let comment_line = format!("# {key} = {raw_value}\n");
                    // Scope the guard to the target section body so that an identical key
                    // name in another section does not suppress this insertion.
                    if !section_body(user_toml, section_key).contains(comment_line.trim()) {
                        comments.push((section_key.to_owned(), comment_line));
                        count += 1;
                    }
                }
            }
        }
    }
    (count, comments)
}

/// Return the body of `[section]` in `doc` — the text between the section header line
/// and the next top-level `[...]` header (or end of document).
///
/// Used to scope idempotency guards to a single section so that a comment present in
/// one section does not suppress insertion into a different section with the same key name.
fn section_body<'a>(doc: &'a str, section: &str) -> &'a str {
    let header = format!("[{section}]");
    let Some(section_start) = doc.find(&header) else {
        return "";
    };
    let body_start = section_start + header.len();
    let body_end = doc[body_start..]
        .find("\n[")
        .map_or(doc.len(), |r| body_start + r);
    &doc[body_start..body_end]
}

/// Insert `text` after the last line belonging to `[section_name]` and before the next
/// top-level `[section]` header (or at the end of the file if no such header follows).
///
/// This is a purely textual operation: it does not parse TOML, making it immune to
/// `toml_edit` decor round-trip loss.
fn insert_after_section(raw: &str, section_name: &str, text: &str) -> String {
    let header = format!("[{section_name}]");
    let Some(section_start) = raw.find(&header) else {
        return format!("{raw}{text}");
    };
    // Find the next top-level section `[...]` after `section_start`.
    let search_from = section_start + header.len();
    // Look for `\n[` which signals a new top-level section.
    let insert_pos = raw[search_from..]
        .find("\n[")
        .map_or(raw.len(), |rel| search_from + rel + 1);
    let mut out = String::with_capacity(raw.len() + text.len());
    out.push_str(&raw[..insert_pos]);
    out.push_str(text);
    out.push_str(&raw[insert_pos..]);
    out
}

/// Format a reference item as a commented TOML line: `# key = value`.
fn format_commented_item(key: &str, item: &Item) -> String {
    if let Some(val) = item.as_value() {
        let raw = value_to_toml_string(val);
        if !raw.is_empty() {
            return format!("# {key} = {raw}\n");
        }
    }
    String::new()
}

/// Render a table as a commented-out TOML block with arbitrary nesting depth.
///
/// `section_name` is the full dotted path (e.g. `security.content_isolation`).
/// Returns an empty string if the table has no renderable content.
fn commented_table_block(section_name: &str, table: &Table) -> String {
    use std::fmt::Write as _;

    let mut lines = format!("# [{section_name}]\n");

    for (key, item) in table {
        if item.is_table() {
            if let Some(sub_table) = item.as_table() {
                let sub_name = format!("{section_name}.{key}");
                let sub_block = commented_table_block(&sub_name, sub_table);
                if !sub_block.is_empty() {
                    lines.push('\n');
                    lines.push_str(&sub_block);
                }
            }
        } else if item.is_array_of_tables() {
            // Skip — user configures these manually (e.g. `[[mcp.servers]]`).
        } else if let Some(val) = item.as_value() {
            let raw = value_to_toml_string(val);
            if !raw.is_empty() {
                let _ = writeln!(lines, "# {key} = {raw}");
            }
        }
    }

    // Return empty if we only wrote the section header with no content.
    if lines.trim() == format!("[{section_name}]") {
        return String::new();
    }
    lines
}

/// Convert a `toml_edit::Value` to its TOML string representation.
fn value_to_toml_string(val: &Value) -> String {
    match val {
        Value::String(s) => {
            let inner = s.value();
            format!("\"{inner}\"")
        }
        Value::Integer(i) => i.value().to_string(),
        Value::Float(f) => {
            let v = f.value();
            // Use representation that round-trips exactly.
            if v.fract() == 0.0 {
                format!("{v:.1}")
            } else {
                format!("{v}")
            }
        }
        Value::Boolean(b) => b.value().to_string(),
        Value::Array(arr) => format_array(arr),
        Value::InlineTable(t) => {
            let pairs: Vec<String> = t
                .iter()
                .map(|(k, v)| format!("{k} = {}", value_to_toml_string(v)))
                .collect();
            format!("{{ {} }}", pairs.join(", "))
        }
        Value::Datetime(dt) => dt.value().to_string(),
    }
}

fn format_array(arr: &Array) -> String {
    if arr.is_empty() {
        return "[]".to_owned();
    }
    let items: Vec<String> = arr.iter().map(value_to_toml_string).collect();
    format!("[{}]", items.join(", "))
}

/// Reorder top-level sections of a TOML document string by the canonical order.
///
/// Sections not in the canonical list are placed at the end, preserving their relative order.
/// This operates on the raw string rather than the parsed document to preserve comments that
/// would otherwise be dropped by `toml_edit`'s round-trip.
fn reorder_sections(toml_str: &str, canonical_order: &[&str]) -> String {
    let sections = split_into_sections(toml_str);
    if sections.is_empty() {
        return toml_str.to_owned();
    }

    // Each entry is (header, content). Empty header = preamble block.
    let preamble_block = sections
        .iter()
        .find(|(h, _)| h.is_empty())
        .map_or("", |(_, c)| c.as_str());

    let section_map: Vec<(&str, &str)> = sections
        .iter()
        .filter(|(h, _)| !h.is_empty())
        .map(|(h, c)| (h.as_str(), c.as_str()))
        .collect();

    let mut out = String::new();
    if !preamble_block.is_empty() {
        out.push_str(preamble_block);
    }

    let mut emitted: Vec<bool> = vec![false; section_map.len()];

    for &canon in canonical_order {
        for (idx, &(header, content)) in section_map.iter().enumerate() {
            let section_name = extract_section_name(header);
            let top_level = section_name
                .split('.')
                .next()
                .unwrap_or("")
                .trim_start_matches('#')
                .trim();
            if top_level == canon && !emitted[idx] {
                out.push_str(content);
                emitted[idx] = true;
            }
        }
    }

    // Append sections not in canonical order.
    for (idx, &(_, content)) in section_map.iter().enumerate() {
        if !emitted[idx] {
            out.push_str(content);
        }
    }

    out
}

/// Extract the section name from a section header line (e.g. `[agent]` → `agent`).
fn extract_section_name(header: &str) -> &str {
    // Strip leading `# ` for commented headers.
    let trimmed = header.trim().trim_start_matches("# ");
    // Strip `[` and `]`.
    if trimmed.starts_with('[') && trimmed.contains(']') {
        let inner = &trimmed[1..];
        if let Some(end) = inner.find(']') {
            return &inner[..end];
        }
    }
    trimmed
}

/// Split a TOML string into `(header_line, full_block)` pairs.
///
/// The first element may have an empty header representing the preamble.
fn split_into_sections(toml_str: &str) -> Vec<(String, String)> {
    let mut sections: Vec<(String, String)> = Vec::new();
    let mut current_header = String::new();
    let mut current_content = String::new();

    for line in toml_str.lines() {
        let trimmed = line.trim();
        if is_top_level_section_header(trimmed) {
            sections.push((current_header.clone(), current_content.clone()));
            trimmed.clone_into(&mut current_header);
            line.clone_into(&mut current_content);
            current_content.push('\n');
        } else {
            current_content.push_str(line);
            current_content.push('\n');
        }
    }

    // Push the last section.
    if !current_header.is_empty() || !current_content.is_empty() {
        sections.push((current_header, current_content));
    }

    sections
}

/// Determine if a line is a real (non-commented) top-level section header.
///
/// Top-level means `[name]` with no dots. Commented headers like `# [name]`
/// are NOT treated as section boundaries — they are migrator-generated hints.
fn is_top_level_section_header(line: &str) -> bool {
    if line.starts_with('[')
        && !line.starts_with("[[")
        && let Some(end) = line.find(']')
    {
        return !line[1..end].contains('.');
    }
    false
}

#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_ollama_provider(
    llm: &toml_edit::Table,
    model: &Option<String>,
    base_url: &Option<String>,
    embedding_model: &Option<String>,
) -> Vec<String> {
    let mut block = "[[llm.providers]]\ntype = \"ollama\"\n".to_owned();
    if let Some(m) = model {
        block.push_str(&format!("model = \"{m}\"\n"));
    }
    if let Some(em) = embedding_model {
        block.push_str(&format!("embedding_model = \"{em}\"\n"));
    }
    if let Some(u) = base_url {
        block.push_str(&format!("base_url = \"{u}\"\n"));
    }
    let _ = llm; // not needed for simple ollama case
    vec![block]
}

#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_claude_provider(llm: &toml_edit::Table, model: &Option<String>) -> Vec<String> {
    let mut block = "[[llm.providers]]\ntype = \"claude\"\n".to_owned();
    if let Some(cloud) = llm.get("cloud").and_then(toml_edit::Item::as_table) {
        if let Some(m) = cloud.get("model").and_then(toml_edit::Item::as_str) {
            block.push_str(&format!("model = \"{m}\"\n"));
        }
        if let Some(t) = cloud
            .get("max_tokens")
            .and_then(toml_edit::Item::as_integer)
        {
            block.push_str(&format!("max_tokens = {t}\n"));
        }
        if cloud
            .get("server_compaction")
            .and_then(toml_edit::Item::as_bool)
            == Some(true)
        {
            block.push_str("server_compaction = true\n");
        }
        if cloud
            .get("enable_extended_context")
            .and_then(toml_edit::Item::as_bool)
            == Some(true)
        {
            block.push_str("enable_extended_context = true\n");
        }
        if let Some(thinking) = cloud.get("thinking").and_then(toml_edit::Item::as_table) {
            let pairs: Vec<String> = thinking.iter().map(|(k, v)| format!("{k} = {v}")).collect();
            block.push_str(&format!("thinking = {{ {} }}\n", pairs.join(", ")));
        }
        if let Some(v) = cloud
            .get("prompt_cache_ttl")
            .and_then(toml_edit::Item::as_str)
        {
            if v != "ephemeral" {
                block.push_str(&format!("prompt_cache_ttl = \"{v}\"\n"));
            }
        }
    } else if let Some(m) = model {
        block.push_str(&format!("model = \"{m}\"\n"));
    }
    vec![block]
}

#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_openai_provider(llm: &toml_edit::Table, model: &Option<String>) -> Vec<String> {
    let mut block = "[[llm.providers]]\ntype = \"openai\"\n".to_owned();
    if let Some(openai) = llm.get("openai").and_then(toml_edit::Item::as_table) {
        copy_str_field(openai, "model", &mut block);
        copy_str_field(openai, "base_url", &mut block);
        copy_int_field(openai, "max_tokens", &mut block);
        copy_str_field(openai, "embedding_model", &mut block);
        copy_str_field(openai, "reasoning_effort", &mut block);
    } else if let Some(m) = model {
        block.push_str(&format!("model = \"{m}\"\n"));
    }
    vec![block]
}

#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_gemini_provider(llm: &toml_edit::Table, model: &Option<String>) -> Vec<String> {
    let mut block = "[[llm.providers]]\ntype = \"gemini\"\n".to_owned();
    if let Some(gemini) = llm.get("gemini").and_then(toml_edit::Item::as_table) {
        copy_str_field(gemini, "model", &mut block);
        copy_int_field(gemini, "max_tokens", &mut block);
        copy_str_field(gemini, "base_url", &mut block);
        copy_str_field(gemini, "embedding_model", &mut block);
        copy_str_field(gemini, "thinking_level", &mut block);
        copy_int_field(gemini, "thinking_budget", &mut block);
        if let Some(v) = gemini
            .get("include_thoughts")
            .and_then(toml_edit::Item::as_bool)
        {
            block.push_str(&format!("include_thoughts = {v}\n"));
        }
    } else if let Some(m) = model {
        block.push_str(&format!("model = \"{m}\"\n"));
    }
    vec![block]
}

#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_compatible_provider(llm: &toml_edit::Table) -> Vec<String> {
    let mut blocks = Vec::new();
    if let Some(compat_arr) = llm
        .get("compatible")
        .and_then(toml_edit::Item::as_array_of_tables)
    {
        for entry in compat_arr {
            let mut block = "[[llm.providers]]\ntype = \"compatible\"\n".to_owned();
            copy_str_field(entry, "name", &mut block);
            copy_str_field(entry, "base_url", &mut block);
            copy_str_field(entry, "model", &mut block);
            copy_int_field(entry, "max_tokens", &mut block);
            copy_str_field(entry, "embedding_model", &mut block);
            blocks.push(block);
        }
    }
    blocks
}

// Returns (provider_blocks, routing)
#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_orchestrator_provider(
    llm: &toml_edit::Table,
    model: &Option<String>,
    base_url: &Option<String>,
    embedding_model: &Option<String>,
) -> (Vec<String>, Option<String>) {
    let mut blocks = Vec::new();
    let routing = None;
    if let Some(orch) = llm.get("orchestrator").and_then(toml_edit::Item::as_table) {
        let default_name = orch
            .get("default")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("")
            .to_owned();
        let embed_name = orch
            .get("embed")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("")
            .to_owned();
        if let Some(providers) = orch.get("providers").and_then(toml_edit::Item::as_table) {
            for (name, pcfg_item) in providers {
                let Some(pcfg) = pcfg_item.as_table() else {
                    continue;
                };
                let ptype = pcfg
                    .get("type")
                    .and_then(toml_edit::Item::as_str)
                    .unwrap_or("ollama");
                let mut block =
                    format!("[[llm.providers]]\nname = \"{name}\"\ntype = \"{ptype}\"\n");
                if name == default_name {
                    block.push_str("default = true\n");
                }
                if name == embed_name {
                    block.push_str("embed = true\n");
                }
                copy_str_field(pcfg, "model", &mut block);
                copy_str_field(pcfg, "base_url", &mut block);
                copy_str_field(pcfg, "embedding_model", &mut block);
                if ptype == "claude" && !pcfg.contains_key("model") {
                    if let Some(cloud) = llm.get("cloud").and_then(toml_edit::Item::as_table) {
                        copy_str_field(cloud, "model", &mut block);
                        copy_int_field(cloud, "max_tokens", &mut block);
                    }
                }
                if ptype == "openai" && !pcfg.contains_key("model") {
                    if let Some(openai) = llm.get("openai").and_then(toml_edit::Item::as_table) {
                        copy_str_field(openai, "model", &mut block);
                        copy_str_field(openai, "base_url", &mut block);
                        copy_int_field(openai, "max_tokens", &mut block);
                        copy_str_field(openai, "embedding_model", &mut block);
                    }
                }
                if ptype == "ollama" && !pcfg.contains_key("base_url") {
                    if let Some(u) = base_url {
                        block.push_str(&format!("base_url = \"{u}\"\n"));
                    }
                }
                if ptype == "ollama" && !pcfg.contains_key("model") {
                    if let Some(m) = model {
                        block.push_str(&format!("model = \"{m}\"\n"));
                    }
                }
                if ptype == "ollama" && !pcfg.contains_key("embedding_model") {
                    if let Some(em) = embedding_model {
                        block.push_str(&format!("embedding_model = \"{em}\"\n"));
                    }
                }
                blocks.push(block);
            }
        }
    }
    (blocks, routing)
}

// Returns (provider_blocks, routing)
#[allow(clippy::format_push_string, clippy::collapsible_if, clippy::ref_option)]
fn migrate_router_provider(
    llm: &toml_edit::Table,
    model: &Option<String>,
    base_url: &Option<String>,
    embedding_model: &Option<String>,
) -> (Vec<String>, Option<String>) {
    let mut blocks = Vec::new();
    let mut routing = None;
    if let Some(router) = llm.get("router").and_then(toml_edit::Item::as_table) {
        let strategy = router
            .get("strategy")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("ema");
        routing = Some(strategy.to_owned());
        if let Some(chain) = router.get("chain").and_then(toml_edit::Item::as_array) {
            for item in chain {
                let name = item.as_str().unwrap_or_default();
                let ptype = infer_provider_type(name, llm);
                let mut block =
                    format!("[[llm.providers]]\nname = \"{name}\"\ntype = \"{ptype}\"\n");
                match ptype {
                    "claude" => {
                        if let Some(cloud) = llm.get("cloud").and_then(toml_edit::Item::as_table) {
                            copy_str_field(cloud, "model", &mut block);
                            copy_int_field(cloud, "max_tokens", &mut block);
                        }
                    }
                    "openai" => {
                        if let Some(openai) = llm.get("openai").and_then(toml_edit::Item::as_table)
                        {
                            copy_str_field(openai, "model", &mut block);
                            copy_str_field(openai, "base_url", &mut block);
                            copy_int_field(openai, "max_tokens", &mut block);
                            copy_str_field(openai, "embedding_model", &mut block);
                        } else {
                            if let Some(m) = model {
                                block.push_str(&format!("model = \"{m}\"\n"));
                            }
                            if let Some(u) = base_url {
                                block.push_str(&format!("base_url = \"{u}\"\n"));
                            }
                        }
                    }
                    "ollama" => {
                        if let Some(m) = model {
                            block.push_str(&format!("model = \"{m}\"\n"));
                        }
                        if let Some(em) = embedding_model {
                            block.push_str(&format!("embedding_model = \"{em}\"\n"));
                        }
                        if let Some(u) = base_url {
                            block.push_str(&format!("base_url = \"{u}\"\n"));
                        }
                    }
                    _ => {
                        if let Some(m) = model {
                            block.push_str(&format!("model = \"{m}\"\n"));
                        }
                    }
                }
                blocks.push(block);
            }
        }
    }
    (blocks, routing)
}

/// Migrate a TOML config string from the old `[llm]` format (with `provider`, `[llm.cloud]`,
/// `[llm.openai]`, `[llm.orchestrator]`, `[llm.router]` sections) to the new
/// `[[llm.providers]]` array format.
///
/// If the config does not contain legacy LLM keys, it is returned unchanged.
/// Removes `routing = "task"` and `[llm.routes]` block lines from a raw TOML string.
///
/// Used as a pre-pass before `migrate_llm_to_providers` when the removed variant is detected.
fn strip_task_routing_keys(toml_src: &str) -> String {
    let mut in_routes_block = false;
    let mut out = Vec::new();
    for line in toml_src.lines() {
        let trimmed = line.trim();
        if trimmed == "[llm.routes]" {
            in_routes_block = true;
            continue;
        }
        if in_routes_block {
            // Exit the routes block when we hit the next section header.
            if trimmed.starts_with('[') {
                in_routes_block = false;
            } else {
                continue;
            }
        }
        // Strip bare `routing = "task"` assignment.
        if trimmed.starts_with("routing") && trimmed.contains("\"task\"") {
            continue;
        }
        out.push(line);
    }
    out.join("\n")
}

/// Creates a `.bak` backup at `backup_path` before writing.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the input TOML is invalid.
#[allow(
    clippy::too_many_lines,
    clippy::format_push_string,
    clippy::manual_let_else,
    clippy::op_ref,
    clippy::collapsible_if
)]
pub fn migrate_llm_to_providers(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    // Detect whether this is a legacy-format config.
    let llm = match doc.get("llm").and_then(toml_edit::Item::as_table) {
        Some(t) => t,
        None => {
            // No [llm] section at all — nothing to migrate.
            return Ok(MigrationResult {
                output: toml_src.to_owned(),
                changed_count: 0,
                sections_changed: Vec::new(),
            });
        }
    };

    // Pre-check: `routing = "task"` was removed as unimplemented (#3248).
    // Detect on the input document before any block transforms.
    if llm.get("routing").and_then(toml_edit::Item::as_str) == Some("task") {
        let routes_count = llm
            .get("routes")
            .and_then(toml_edit::Item::as_table)
            .map_or(0, toml_edit::Table::len);
        let msg = format!(
            "routing = \"task\" is no longer supported and has been removed (#3248). \
             {routes_count} route(s) in [llm.routes] will be dropped. \
             Falling back to default single-provider routing."
        );
        tracing::warn!("{msg}");
        eprintln!("WARNING: {msg}");
        // Strip the removed keys and re-run migration on the cleaned source.
        let cleaned = strip_task_routing_keys(toml_src);
        return migrate_llm_to_providers(&cleaned);
    }

    let has_provider_field = llm.contains_key("provider");
    let has_cloud = llm.contains_key("cloud");
    let has_openai = llm.contains_key("openai");
    let has_gemini = llm.contains_key("gemini");
    let has_orchestrator = llm.contains_key("orchestrator");
    let has_router = llm.contains_key("router");
    let has_providers = llm.contains_key("providers");

    if !has_provider_field
        && !has_cloud
        && !has_openai
        && !has_orchestrator
        && !has_router
        && !has_gemini
    {
        // Already in new format (or empty).
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    if has_providers {
        // Mixed format — refuse to migrate, let the caller handle the error.
        return Err(MigrateError::Parse(
            "cannot migrate: [[llm.providers]] already exists alongside legacy keys"
                .parse::<toml_edit::DocumentMut>()
                .unwrap_err(),
        ));
    }

    // Build new [[llm.providers]] entries from legacy sections.
    let provider_str = llm
        .get("provider")
        .and_then(toml_edit::Item::as_str)
        .unwrap_or("ollama");
    let base_url = llm
        .get("base_url")
        .and_then(toml_edit::Item::as_str)
        .map(str::to_owned);
    let model = llm
        .get("model")
        .and_then(toml_edit::Item::as_str)
        .map(str::to_owned);
    let embedding_model = llm
        .get("embedding_model")
        .and_then(toml_edit::Item::as_str)
        .map(str::to_owned);

    // Collect provider entries as inline TOML strings.
    let mut provider_blocks: Vec<String> = Vec::new();
    let mut routing: Option<String> = None;

    match provider_str {
        "ollama" => {
            provider_blocks.extend(migrate_ollama_provider(
                llm,
                &model,
                &base_url,
                &embedding_model,
            ));
        }
        "claude" => {
            provider_blocks.extend(migrate_claude_provider(llm, &model));
        }
        "openai" => {
            provider_blocks.extend(migrate_openai_provider(llm, &model));
        }
        "gemini" => {
            provider_blocks.extend(migrate_gemini_provider(llm, &model));
        }
        "compatible" => {
            provider_blocks.extend(migrate_compatible_provider(llm));
        }
        "orchestrator" => {
            let (blocks, r) =
                migrate_orchestrator_provider(llm, &model, &base_url, &embedding_model);
            provider_blocks.extend(blocks);
            routing = r;
        }
        "router" => {
            let (blocks, r) = migrate_router_provider(llm, &model, &base_url, &embedding_model);
            provider_blocks.extend(blocks);
            routing = r;
        }
        other => {
            let mut block = format!("[[llm.providers]]\ntype = \"{other}\"\n");
            if let Some(ref m) = model {
                block.push_str(&format!("model = \"{m}\"\n"));
            }
            provider_blocks.push(block);
        }
    }

    if provider_blocks.is_empty() {
        // Nothing to convert; return as-is.
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Build the replacement [llm] section.
    let mut new_llm = "[llm]\n".to_owned();
    if let Some(ref r) = routing {
        new_llm.push_str(&format!("routing = \"{r}\"\n"));
    }
    // Carry over cross-cutting LLM settings.
    for key in &[
        "response_cache_enabled",
        "response_cache_ttl_secs",
        "semantic_cache_enabled",
        "semantic_cache_threshold",
        "semantic_cache_max_candidates",
        "summary_model",
        "instruction_file",
    ] {
        if let Some(val) = llm.get(key) {
            if let Some(v) = val.as_value() {
                let raw = value_to_toml_string(v);
                if !raw.is_empty() {
                    new_llm.push_str(&format!("{key} = {raw}\n"));
                }
            }
        }
    }
    new_llm.push('\n');

    for block in &provider_blocks {
        new_llm.push_str(block);
        new_llm.push('\n');
    }

    // Remove old [llm] section and all its sub-sections from the source,
    // then prepend the new section.
    let output = replace_llm_section(toml_src, &new_llm);

    Ok(MigrationResult {
        output,
        changed_count: provider_blocks.len(),
        sections_changed: vec!["llm.providers".to_owned()],
    })
}

/// Infer provider type from a name used in router chain.
fn infer_provider_type<'a>(name: &str, llm: &'a toml_edit::Table) -> &'a str {
    match name {
        "claude" => "claude",
        "openai" => "openai",
        "gemini" => "gemini",
        "ollama" => "ollama",
        "candle" => "candle",
        _ => {
            // Check if there's a compatible entry with this name.
            if llm.contains_key("compatible") {
                "compatible"
            } else if llm.contains_key("openai") {
                "openai"
            } else {
                "ollama"
            }
        }
    }
}

fn copy_str_field(table: &toml_edit::Table, key: &str, out: &mut String) {
    use std::fmt::Write as _;
    if let Some(v) = table.get(key).and_then(toml_edit::Item::as_str) {
        let _ = writeln!(out, "{key} = \"{v}\"");
    }
}

fn copy_int_field(table: &toml_edit::Table, key: &str, out: &mut String) {
    use std::fmt::Write as _;
    if let Some(v) = table.get(key).and_then(toml_edit::Item::as_integer) {
        let _ = writeln!(out, "{key} = {v}");
    }
}

/// Replace the entire [llm] section (including all [llm.*] sub-sections and
/// [[llm.*]] array-of-table entries) with `new_llm_section`.
fn replace_llm_section(toml_str: &str, new_llm_section: &str) -> String {
    let mut out = String::new();
    let mut in_llm = false;
    let mut skip_until_next_top = false;

    for line in toml_str.lines() {
        let trimmed = line.trim();

        // Check if this is a top-level section header [something] or [[something]].
        let is_top_section = (trimmed.starts_with('[') && !trimmed.starts_with("[["))
            && trimmed.ends_with(']')
            && !trimmed[1..trimmed.len() - 1].contains('.');
        let is_top_aot = trimmed.starts_with("[[")
            && trimmed.ends_with("]]")
            && !trimmed[2..trimmed.len() - 2].contains('.');
        let is_llm_sub = (trimmed.starts_with("[llm") || trimmed.starts_with("[[llm"))
            && (trimmed.contains(']'));

        if is_llm_sub || (in_llm && !is_top_section && !is_top_aot) {
            in_llm = true;
            skip_until_next_top = true;
            continue;
        }

        if is_top_section || is_top_aot {
            if skip_until_next_top {
                // Emit the new LLM section before the next top-level section.
                out.push_str(new_llm_section);
                skip_until_next_top = false;
            }
            in_llm = false;
        }

        if !skip_until_next_top {
            out.push_str(line);
            out.push('\n');
        }
    }

    // If [llm] was the last section, append now.
    if skip_until_next_top {
        out.push_str(new_llm_section);
    }

    out
}

/// Fields extracted from `[llm.stt]` that drive the migration decision.
struct SttFields {
    model: Option<String>,
    base_url: Option<String>,
    provider_hint: String,
}

/// Extract migration-relevant fields from `[llm.stt]` in the parsed document.
fn extract_stt_fields(doc: &toml_edit::DocumentMut) -> SttFields {
    let stt_table = doc
        .get("llm")
        .and_then(toml_edit::Item::as_table)
        .and_then(|llm| llm.get("stt"))
        .and_then(toml_edit::Item::as_table);

    let model = stt_table
        .and_then(|stt| stt.get("model"))
        .and_then(toml_edit::Item::as_str)
        .map(ToOwned::to_owned);

    let base_url = stt_table
        .and_then(|stt| stt.get("base_url"))
        .and_then(toml_edit::Item::as_str)
        .map(ToOwned::to_owned);

    let provider_hint = stt_table
        .and_then(|stt| stt.get("provider"))
        .and_then(toml_edit::Item::as_str)
        .map(ToOwned::to_owned)
        .unwrap_or_default();

    SttFields {
        model,
        base_url,
        provider_hint,
    }
}

/// Find the index of the first `[[llm.providers]]` entry that matches `target_type` or
/// `provider_hint`, giving priority to explicit name/type matches over type-only matches.
fn find_matching_provider_index(
    doc: &toml_edit::DocumentMut,
    target_type: &str,
    provider_hint: &str,
) -> Option<usize> {
    let providers = doc
        .get("llm")
        .and_then(toml_edit::Item::as_table)
        .and_then(|llm| llm.get("providers"))
        .and_then(toml_edit::Item::as_array_of_tables)?;

    providers.iter().enumerate().find_map(|(i, t)| {
        let name = t
            .get("name")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("");
        let ptype = t
            .get("type")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("");
        // Match by explicit name hint or by type when hint is a legacy backend string.
        let name_match =
            !provider_hint.is_empty() && (name == provider_hint || ptype == provider_hint);
        let type_match = ptype == target_type;
        if name_match || type_match {
            Some(i)
        } else {
            None
        }
    })
}

/// Attach `stt_model` (and optionally `base_url`) to an existing `[[llm.providers]]` entry
/// at `idx`. Ensures the entry has an explicit `name` (W2 guard) and returns that name.
fn attach_stt_to_existing_provider(
    doc: &mut toml_edit::DocumentMut,
    idx: usize,
    stt_model: &str,
    stt_base_url: Option<&str>,
) -> Result<String, MigrateError> {
    let llm_mut = doc
        .get_mut("llm")
        .and_then(toml_edit::Item::as_table_mut)
        .ok_or(MigrateError::InvalidStructure(
            "[llm] table not accessible for mutation",
        ))?;
    let providers_mut = llm_mut
        .get_mut("providers")
        .and_then(toml_edit::Item::as_array_of_tables_mut)
        .ok_or(MigrateError::InvalidStructure(
            "[[llm.providers]] array not accessible for mutation",
        ))?;
    let entry = providers_mut
        .iter_mut()
        .nth(idx)
        .ok_or(MigrateError::InvalidStructure(
            "[[llm.providers]] entry index out of range during mutation",
        ))?;

    // W2: ensure explicit name.
    let existing_name = entry
        .get("name")
        .and_then(toml_edit::Item::as_str)
        .map(ToOwned::to_owned);
    let entry_name = existing_name.unwrap_or_else(|| {
        let t = entry
            .get("type")
            .and_then(toml_edit::Item::as_str)
            .unwrap_or("openai");
        format!("{t}-stt")
    });
    entry.insert("name", toml_edit::value(entry_name.clone()));
    entry.insert("stt_model", toml_edit::value(stt_model));
    if let Some(url) = stt_base_url
        && entry.get("base_url").is_none()
    {
        entry.insert("base_url", toml_edit::value(url));
    }
    Ok(entry_name)
}

/// Append a new `[[llm.providers]]` entry carrying `stt_model`, creating the array if absent.
/// Returns the name assigned to the new entry.
fn append_new_stt_provider(
    doc: &mut toml_edit::DocumentMut,
    target_type: &str,
    stt_model: &str,
    stt_base_url: Option<&str>,
) -> Result<String, MigrateError> {
    let new_name = if target_type == "candle" {
        "local-whisper".to_owned()
    } else {
        "openai-stt".to_owned()
    };
    let mut new_entry = toml_edit::Table::new();
    new_entry.insert("name", toml_edit::value(new_name.clone()));
    new_entry.insert("type", toml_edit::value(target_type));
    new_entry.insert("stt_model", toml_edit::value(stt_model));
    if let Some(url) = stt_base_url {
        new_entry.insert("base_url", toml_edit::value(url));
    }
    let llm_mut = doc
        .get_mut("llm")
        .and_then(toml_edit::Item::as_table_mut)
        .ok_or(MigrateError::InvalidStructure(
            "[llm] table not accessible for mutation",
        ))?;
    if let Some(item) = llm_mut.get_mut("providers") {
        if let Some(arr) = item.as_array_of_tables_mut() {
            arr.push(new_entry);
        }
    } else {
        let mut arr = toml_edit::ArrayOfTables::new();
        arr.push(new_entry);
        llm_mut.insert("providers", toml_edit::Item::ArrayOfTables(arr));
    }
    Ok(new_name)
}

/// Update `[llm.stt]`: set `provider` to `resolved_provider_name` and strip `model`/`base_url`.
fn rewrite_stt_section(doc: &mut toml_edit::DocumentMut, resolved_provider_name: &str) {
    if let Some(stt_table) = doc
        .get_mut("llm")
        .and_then(toml_edit::Item::as_table_mut)
        .and_then(|llm| llm.get_mut("stt"))
        .and_then(toml_edit::Item::as_table_mut)
    {
        stt_table.insert("provider", toml_edit::value(resolved_provider_name));
        stt_table.remove("model");
        stt_table.remove("base_url");
    }
}

/// Migrate an old `[llm.stt]` section (with `model` / `base_url` fields) to the new format
/// where those fields live on a `[[llm.providers]]` entry via `stt_model`.
///
/// Transformations:
/// - `[llm.stt].model` → `stt_model` on the matching or new `[[llm.providers]]` entry
/// - `[llm.stt].base_url` → `base_url` on that entry (skipped when already present)
/// - `[llm.stt].provider` is updated to the provider name; the entry is assigned an explicit
///   `name` when it lacked one (W2 guard).
/// - Old `model` and `base_url` keys are stripped from `[llm.stt]`.
///
/// If `[llm.stt]` is absent or already uses the new format (no `model` / `base_url`), the
/// input is returned unchanged.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the input TOML is invalid.
/// Returns `MigrateError::InvalidStructure` if `[llm.stt].model` is present but the `[llm]`
/// key is absent or not a table, making mutation impossible.
pub fn migrate_stt_to_provider(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    let stt = extract_stt_fields(&doc);

    // Nothing to migrate if [llm.stt] does not exist or already lacks the old fields.
    if stt.model.is_none() && stt.base_url.is_none() {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let stt_model = stt.model.unwrap_or_else(|| "whisper-1".to_owned());

    // Determine the target provider type based on provider hint.
    let target_type = match stt.provider_hint.as_str() {
        "candle-whisper" | "candle" => "candle",
        _ => "openai",
    };

    let resolved_name = match find_matching_provider_index(&doc, target_type, &stt.provider_hint) {
        Some(idx) => {
            attach_stt_to_existing_provider(&mut doc, idx, &stt_model, stt.base_url.as_deref())?
        }
        None => {
            append_new_stt_provider(&mut doc, target_type, &stt_model, stt.base_url.as_deref())?
        }
    };

    rewrite_stt_section(&mut doc, &resolved_name);

    Ok(MigrationResult {
        output: doc.to_string(),
        changed_count: 1,
        sections_changed: vec!["llm.providers.stt_model".to_owned()],
    })
}

/// Migrate `[orchestration] planner_model` to `planner_provider`.
///
/// The namespaces differ: `planner_model` held a raw model name (e.g. `"gpt-4o"`),
/// while `planner_provider` must reference a `[[llm.providers]]` `name` field. A migrated
/// value would cause a silent `warn!` from `build_planner_provider()` when resolution fails,
/// so the old value is commented out and a warning is emitted.
///
/// If `planner_model` is absent, the input is returned unchanged.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the input TOML is invalid.
pub fn migrate_planner_model_to_provider(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    let old_value = doc
        .get("orchestration")
        .and_then(toml_edit::Item::as_table)
        .and_then(|t| t.get("planner_model"))
        .and_then(toml_edit::Item::as_value)
        .and_then(toml_edit::Value::as_str)
        .map(ToOwned::to_owned);

    let Some(old_model) = old_value else {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    };

    // Remove the old key via text substitution to preserve surrounding comments/formatting.
    // We rebuild the section comment in the output rather than using toml_edit mutations,
    // following the same line-oriented approach used elsewhere in this file.
    let commented_out = format!(
        "# planner_provider = \"{old_model}\"  \
         # MIGRATED: was planner_model; update to a [[llm.providers]] name"
    );

    let orch_table = doc
        .get_mut("orchestration")
        .and_then(toml_edit::Item::as_table_mut)
        .ok_or(MigrateError::InvalidStructure(
            "[orchestration] is not a table",
        ))?;
    orch_table.remove("planner_model");
    let decor = orch_table.decor_mut();
    let existing_suffix = decor.suffix().and_then(|s| s.as_str()).unwrap_or("");
    // Append the commented-out entry as a trailing comment on the section.
    let new_suffix = if existing_suffix.trim().is_empty() {
        format!("\n{commented_out}\n")
    } else {
        format!("{existing_suffix}\n{commented_out}\n")
    };
    decor.set_suffix(new_suffix);

    eprintln!(
        "Migration warning: [orchestration].planner_model has been renamed to planner_provider \
         and its value commented out. `planner_provider` must reference a [[llm.providers]] \
         `name` field, not a raw model name. Update or remove the commented line."
    );

    Ok(MigrationResult {
        output: doc.to_string(),
        changed_count: 1,
        sections_changed: vec!["orchestration.planner_provider".to_owned()],
    })
}

/// Migrate `[[mcp.servers]]` entries to add `trust_level = "trusted"` for any entry
/// that lacks an explicit `trust_level`.
///
/// Before this PR all config-defined servers skipped SSRF validation (equivalent to
/// `trust_level = "trusted"`). Without migration, upgrading to the new default
/// (`Untrusted`) would silently break remote servers on private networks.
///
/// This function adds `trust_level = "trusted"` only to entries that are missing the
/// field, preserving entries that already have it set.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_mcp_trust_levels(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    let mut added = 0usize;

    let Some(mcp) = doc.get_mut("mcp").and_then(toml_edit::Item::as_table_mut) else {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    };

    let Some(servers) = mcp
        .get_mut("servers")
        .and_then(toml_edit::Item::as_array_of_tables_mut)
    else {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    };

    for entry in servers.iter_mut() {
        if !entry.contains_key("trust_level") {
            entry.insert(
                "trust_level",
                toml_edit::value(toml_edit::Value::from("trusted")),
            );
            added += 1;
        }
    }

    if added > 0 {
        eprintln!(
            "Migration: added trust_level = \"trusted\" to {added} [[mcp.servers]] \
             entr{} (preserving previous SSRF-skip behavior). \
             Review and adjust trust levels as needed.",
            if added == 1 { "y" } else { "ies" }
        );
    }

    Ok(MigrationResult {
        output: doc.to_string(),
        changed_count: added,
        sections_changed: if added > 0 {
            vec!["mcp.servers.trust_level".to_owned()]
        } else {
            Vec::new()
        },
    })
}

/// Migrate `[agent].max_tool_retries` → `[tools.retry].max_attempts` and
/// `[agent].max_retry_duration_secs` → `[tools.retry].budget_secs`.
///
/// Old fields are preserved (not removed) to avoid breaking configs that rely on them
/// until they are officially deprecated in a future release. The new `[tools.retry]` section
/// is added if missing, populated with the migrated values.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML is invalid.
pub fn migrate_agent_retry_to_tools_retry(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    let max_retries = doc
        .get("agent")
        .and_then(toml_edit::Item::as_table)
        .and_then(|t| t.get("max_tool_retries"))
        .and_then(toml_edit::Item::as_value)
        .and_then(toml_edit::Value::as_integer)
        .map(i64::cast_unsigned);

    let budget_secs = doc
        .get("agent")
        .and_then(toml_edit::Item::as_table)
        .and_then(|t| t.get("max_retry_duration_secs"))
        .and_then(toml_edit::Item::as_value)
        .and_then(toml_edit::Value::as_integer)
        .map(i64::cast_unsigned);

    if max_retries.is_none() && budget_secs.is_none() {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Ensure [tools.retry] section exists.
    if !doc.contains_key("tools") {
        doc.insert("tools", toml_edit::Item::Table(toml_edit::Table::new()));
    }
    let tools_table = doc
        .get_mut("tools")
        .and_then(toml_edit::Item::as_table_mut)
        .ok_or(MigrateError::InvalidStructure("[tools] is not a table"))?;

    if !tools_table.contains_key("retry") {
        tools_table.insert("retry", toml_edit::Item::Table(toml_edit::Table::new()));
    }
    let retry_table = tools_table
        .get_mut("retry")
        .and_then(toml_edit::Item::as_table_mut)
        .ok_or(MigrateError::InvalidStructure(
            "[tools.retry] is not a table",
        ))?;

    let mut changed_count = 0usize;

    if let Some(retries) = max_retries
        && !retry_table.contains_key("max_attempts")
    {
        retry_table.insert(
            "max_attempts",
            toml_edit::value(i64::try_from(retries).unwrap_or(2)),
        );
        changed_count += 1;
    }

    if let Some(secs) = budget_secs
        && !retry_table.contains_key("budget_secs")
    {
        retry_table.insert(
            "budget_secs",
            toml_edit::value(i64::try_from(secs).unwrap_or(30)),
        );
        changed_count += 1;
    }

    if changed_count > 0 {
        eprintln!(
            "Migration: [agent].max_tool_retries / max_retry_duration_secs migrated to \
             [tools.retry].max_attempts / budget_secs. Old fields preserved for compatibility."
        );
    }

    Ok(MigrationResult {
        output: doc.to_string(),
        changed_count,
        sections_changed: if changed_count > 0 {
            vec!["tools.retry".to_owned()]
        } else {
            Vec::new()
        },
    })
}

/// Add a commented-out `database_url = ""` entry under `[memory]` if absent.
///
/// If the `[memory]` section does not exist it is created. This migration surfaces the
/// `PostgreSQL` URL option for users upgrading from a pre-postgres config file.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_database_url(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("database_url") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    // Ensure [memory] section exists (created if absent so the comment has context).
    if !doc.contains_key("memory") {
        doc.insert("memory", toml_edit::Item::Table(toml_edit::Table::new()));
    }

    let comment = "\n# PostgreSQL connection URL (used when binary is compiled with --features postgres).\n\
         # Leave empty and store the actual URL in the vault:\n\
         #   zeph vault set ZEPH_DATABASE_URL \"postgres://user:pass@localhost:5432/zeph\"\n\
         # database_url = \"\"\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.database_url".to_owned()],
    })
}

/// No-op migration for `[tools.shell]` transactional fields added in #2414.
///
/// All 5 new fields have `#[serde(default)]` so existing configs parse without changes.
/// This step adds them as commented-out hints in `[tools.shell]` if not already present.
///
/// # Errors
///
/// Returns `MigrateError` if the TOML cannot be parsed or `[tools.shell]` is malformed.
pub fn migrate_shell_transactional(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("transactional") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    let tools_shell_exists = doc
        .get("tools")
        .and_then(toml_edit::Item::as_table)
        .is_some_and(|t| t.contains_key("shell"));
    if !tools_shell_exists {
        // No [tools.shell] section — nothing to annotate; new configs will get defaults.
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Transactional shell: snapshot files before write commands, rollback on failure.\n\
         # transactional = false\n\
         # transaction_scope = []          # glob patterns; empty = all extracted paths\n\
         # auto_rollback = false           # rollback when exit code >= 2\n\
         # auto_rollback_exit_codes = []   # explicit exit codes; overrides >= 2 heuristic\n\
         # snapshot_required = false       # abort if snapshot fails (default: warn and proceed)\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["tools.shell.transactional".to_owned()],
    })
}

/// Migration step: add `budget_hint_enabled` as a commented-out entry under `[agent]` if absent.
///
/// # Errors
///
/// Returns an error if the config cannot be parsed or the `[agent]` section is malformed.
pub fn migrate_agent_budget_hint(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("budget_hint_enabled") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    if !doc.contains_key("agent") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Inject <budget> XML into the system prompt so the LLM can self-regulate (#2267).\n\
         # budget_hint_enabled = true\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["agent.budget_hint_enabled".to_owned()],
    })
}

/// Add a commented-out `[memory.forgetting]` section if absent (#2397).
///
/// All forgetting fields have `#[serde(default)]` so existing configs parse without changes.
/// This step surfaces the new section for users upgrading from older configs.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_forgetting_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("[memory.forgetting]") || toml_src.contains("# [memory.forgetting]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    if !doc.contains_key("memory") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# SleepGate forgetting sweep (#2397). Disabled by default.\n\
         # [memory.forgetting]\n\
         # enabled = false\n\
         # decay_rate = 0.1                   # per-sweep importance decay\n\
         # forgetting_floor = 0.05            # prune below this score\n\
         # sweep_interval_secs = 7200         # run every 2 hours\n\
         # sweep_batch_size = 500\n\
         # protect_recent_hours = 24\n\
         # protect_min_access_count = 3\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.forgetting".to_owned()],
    })
}

/// Strip any existing `[memory.compression.predictor]` section from the config (#3251).
///
/// The compression predictor feature was removed. This migration cleans up both active
/// and commented-out sections that previous `--migrate-config` runs may have injected.
/// # Errors
///
/// This function is a pure string operation and always returns `Ok`. The `Result`
/// return type is kept for API consistency with other migration functions.
pub fn migrate_compression_predictor_config(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    // Strip any [memory.compression.predictor] section (active or commented-out) that
    // prior migrate-config runs may have injected. The feature is removed (#3251).
    let has_active = toml_src.contains("[memory.compression.predictor]");
    let has_commented = toml_src.contains("# [memory.compression.predictor]");
    if !has_active && !has_commented {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Remove lines that belong to the section header variants and their key lines.
    // A line belongs to the section when the section header has been seen and the
    // line is not a new `[section]` header (excluding the predictor header itself).
    let mut output_lines: Vec<&str> = Vec::new();
    let mut in_predictor = false;
    for line in toml_src.lines() {
        let trimmed = line.trim();
        // Detect active or commented-out section header.
        if trimmed == "[memory.compression.predictor]"
            || trimmed == "# [memory.compression.predictor]"
        {
            in_predictor = true;
            continue;
        }
        // Any new `[section]` header (not commented-out) ends the predictor block.
        if in_predictor && trimmed.starts_with('[') && !trimmed.starts_with("# [") {
            in_predictor = false;
        }
        if !in_predictor {
            output_lines.push(line);
        }
    }
    // Preserve trailing newline if original had one.
    let mut output = output_lines.join("\n");
    if toml_src.ends_with('\n') {
        output.push('\n');
    }

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.compression.predictor".to_owned()],
    })
}

/// Add a commented-out `[memory.microcompact]` block if absent (#2699).
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_microcompact_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("[memory.microcompact]") || toml_src.contains("# [memory.microcompact]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    if !doc.contains_key("memory") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Time-based microcompact (#2699). Strips stale low-value tool outputs after idle.\n\
         # [memory.microcompact]\n\
         # enabled = false\n\
         # gap_threshold_minutes = 60   # idle gap before clearing stale outputs\n\
         # keep_recent = 3              # always keep this many recent outputs intact\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.microcompact".to_owned()],
    })
}

/// Add a commented-out `[memory.autodream]` block if absent (#2697).
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_autodream_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: comments are invisible to toml_edit, so check the raw source.
    if toml_src.contains("[memory.autodream]") || toml_src.contains("# [memory.autodream]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    if !doc.contains_key("memory") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# autoDream background memory consolidation (#2697). Disabled by default.\n\
         # [memory.autodream]\n\
         # enabled = false\n\
         # min_sessions = 5             # sessions since last consolidation\n\
         # min_hours = 8                # hours since last consolidation\n\
         # consolidation_provider = \"\" # provider name from [[llm.providers]]; empty = primary\n\
         # max_iterations = 5\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.autodream".to_owned()],
    })
}

/// Add a commented-out `[magic_docs]` block if absent (#2702).
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_magic_docs_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    use toml_edit::{Item, Table};

    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    if doc.contains_key("magic_docs") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    doc.insert("magic_docs", Item::Table(Table::new()));
    let comment = "# MagicDocs auto-maintained markdown (#2702). Disabled by default.\n\
         # [magic_docs]\n\
         # enabled = false\n\
         # min_turns_between_updates = 10\n\
         # update_provider = \"\"         # provider name from [[llm.providers]]; empty = primary\n\
         # max_iterations = 3\n";
    // Remove the just-inserted empty table and replace with a comment.
    doc.remove("magic_docs");
    // Append as a trailing comment on the document root.
    let raw = doc.to_string();
    let output = format!("{raw}\n{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["magic_docs".to_owned()],
    })
}

/// Add a commented-out `[telemetry]` block if the section is absent (#2846).
///
/// Existing configs that were written before the `telemetry` section was introduced will have
/// the block appended as comments so users can discover and enable it without manual hunting.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if `toml_src` is not valid TOML.
pub fn migrate_telemetry_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    if doc.contains_key("telemetry") || toml_src.contains("# [telemetry]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n\
         # Profiling and distributed tracing (requires --features profiling). All\n\
         # instrumentation points are zero-overhead when the feature is absent.\n\
         # [telemetry]\n\
         # enabled = false\n\
         # backend = \"local\"        # \"local\" (Chrome JSON), \"otlp\", or \"pyroscope\"\n\
         # trace_dir = \".local/traces\"\n\
         # include_args = false\n\
         # service_name = \"zeph-agent\"\n\
         # sample_rate = 1.0\n\
         # otel_filter = \"info\"     # base EnvFilter for OTLP layer; noisy-crate exclusions always appended\n";

    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["telemetry".to_owned()],
    })
}

/// Add a commented-out `[agent.supervisor]` block if the sub-table is absent (#2883).
///
/// Appended as comments under `[agent]` so users can discover and tune supervisor limits
/// without manual hunting. Safe to call on configs that already have the section.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if `toml_src` is not valid TOML.
pub fn migrate_supervisor_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: skip if already present (either as real section or commented-out block).
    if toml_src.contains("[agent.supervisor]") || toml_src.contains("# [agent.supervisor]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    // Only inject the comment block when an [agent] section is already present so we don't
    // pollute configs that have no [agent] at all.
    if !doc.contains_key("agent") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n\
         # Background task supervisor tuning (optional — defaults shown, #2883).\n\
         # [agent.supervisor]\n\
         # enrichment_limit = 4\n\
         # telemetry_limit = 8\n\
         # abort_enrichment_on_turn = false\n";

    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["agent.supervisor".to_owned()],
    })
}

/// Add a commented-out `otel_filter` entry under `[telemetry]` if the key is absent (#2997).
///
/// When `[telemetry]` exists but lacks `otel_filter`, appends the key as a comment so users
/// can discover it without manual hunting. Safe to call when the key is already present
/// (real or commented-out).
///
/// # Errors
///
/// Returns `MigrateError::Parse` if `toml_src` is not valid TOML.
pub fn migrate_otel_filter(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: skip if key already present (real or commented-out).
    if toml_src.contains("otel_filter") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    // Only inject when [telemetry] section exists; otherwise the field will be added
    // by migrate_telemetry_config which already includes it in the commented block.
    if !doc.contains_key("telemetry") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Base EnvFilter for the OTLP tracing layer. Noisy-crate exclusions \
        (tonic=warn etc.) are always appended (#2997).\n\
        # otel_filter = \"info\"\n";
    let raw = doc.to_string();
    // Insert within [telemetry] so the comment stays adjacent to its section.
    let output = insert_after_section(&raw, "telemetry", comment);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["telemetry.otel_filter".to_owned()],
    })
}

/// Adds a commented-out `[tools.egress]` section to configs that predate egress logging (#3058).
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML source cannot be parsed.
pub fn migrate_egress_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("[tools.egress]") || toml_src.contains("tools.egress") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Egress network logging — records outbound HTTP requests to the audit log\n\
        # with per-hop correlation IDs, response metadata, and block reasons (#3058).\n\
        # [tools.egress]\n\
        # enabled = true           # set to false to disable all egress event recording\n\
        # log_blocked = true       # record scheme/domain/SSRF-blocked requests\n\
        # log_response_bytes = true\n\
        # log_hosts_to_tui = true\n";

    let mut output = toml_src.to_owned();
    output.push_str(comment);
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["tools.egress".to_owned()],
    })
}

/// Adds a commented-out `[security.vigil]` section to configs that predate VIGIL (#3058).
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML source cannot be parsed.
pub fn migrate_vigil_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("[security.vigil]") || toml_src.contains("security.vigil") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# VIGIL verify-before-commit intent-anchoring gate (#3058).\n\
        # Runs a regex tripwire on every tool output before it enters LLM context.\n\
        # [security.vigil]\n\
        # enabled = true          # master switch; false bypasses VIGIL entirely\n\
        # strict_mode = false     # true: block (replace with sentinel); false: truncate+annotate\n\
        # sanitize_max_chars = 2048\n\
        # extra_patterns = []     # operator-supplied additional injection patterns (max 64)\n\
        # exempt_tools = [\"memory_search\", \"read_overflow\", \"load_skill\", \"schedule_deferred\"]\n";

    let mut output = toml_src.to_owned();
    output.push_str(comment);
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["security.vigil".to_owned()],
    })
}

/// Adds a commented-out `[tools.sandbox]` section to configs that predate the
/// OS subprocess sandbox wizard (#3070). Also referenced by #3077.
///
/// Idempotent: if the section (or a dotted-key form under `[tools]`) is already
/// present, OR if the commented-out block was already appended by a prior run,
/// the input is returned unchanged. Uses `toml_edit` parsing to avoid false
/// positives from comments that mention `tools.sandbox`.
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML source cannot be parsed.
pub fn migrate_sandbox_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let doc: DocumentMut = toml_src.parse()?;
    let already_present = doc
        .get("tools")
        .and_then(|t| t.as_table())
        .and_then(|t| t.get("sandbox"))
        .is_some();
    // Secondary guard: commented-out block appended by a prior run of this
    // function is not a real TOML key, so toml_edit would not detect it above.
    if already_present || toml_src.contains("# [tools.sandbox]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# OS-level subprocess sandbox for shell commands (#3070).\n\
        # macOS: sandbox-exec (Seatbelt); Linux: bwrap + Landlock + seccomp (requires `sandbox` feature).\n\
        # Applies ONLY to subprocess executors — in-process tools are unaffected.\n\
        # [tools.sandbox]\n\
        # enabled = false                 # set to true to wrap shell commands\n\
        # profile = \"workspace\"          # \"workspace\" | \"read-only\" | \"network-allow-all\" | \"off\"\n\
        # backend = \"auto\"               # \"auto\" | \"seatbelt\" | \"landlock-bwrap\" | \"noop\"\n\
        # strict = true                   # fail startup if sandbox init fails (fail-closed)\n\
        # allow_read = []                 # additional read-allowed absolute paths\n\
        # allow_write = []                # additional write-allowed absolute paths\n";

    let mut output = toml_src.to_owned();
    output.push_str(comment);
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["tools.sandbox".to_owned()],
    })
}

/// Insert `denied_domains` and `fail_if_unavailable` into an existing `[tools.sandbox]`
/// section when those keys are absent (#3294).
///
/// Idempotent: if either key is already present (active or commented), the function is a no-op.
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML document cannot be parsed.
pub fn migrate_sandbox_egress_filter(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Only inject when [tools.sandbox] already exists.
    if !toml_src.contains("[tools.sandbox]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let already_has_denied =
        toml_src.contains("denied_domains") || toml_src.contains("# denied_domains");
    let already_has_fail =
        toml_src.contains("fail_if_unavailable") || toml_src.contains("# fail_if_unavailable");

    if already_has_denied && already_has_fail {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let mut comment = String::new();
    if !already_has_denied {
        comment.push_str(
            "# denied_domains = []       \
             # hostnames denied egress from sandboxed processes (\"pastebin.com\", \"*.evil.com\")\n",
        );
    }
    if !already_has_fail {
        comment.push_str(
            "# fail_if_unavailable = false  \
             # abort startup when no effective OS sandbox is available\n",
        );
    }

    let output = toml_src.replacen(
        "[tools.sandbox]\n",
        &format!("[tools.sandbox]\n{comment}"),
        1,
    );
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["tools.sandbox.denied_domains".to_owned()],
    })
}

/// Add a commented-out `persistence_enabled` key under `[orchestration]` when absent (#3107).
///
/// Existing configs that omit this key pick up `true` via `#[serde(default)]`, so this
/// migration is informational — it surfaces the new option without changing behaviour.
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML document cannot be parsed.
pub fn migrate_orchestration_persistence(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Skip if the key is already present (active or commented).
    if toml_src.contains("persistence_enabled") || toml_src.contains("# persistence_enabled") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Only inject under an existing [orchestration] section.
    if !toml_src.contains("[orchestration]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Insert the commented key right after the `[orchestration]` header line.
    let comment = "# persistence_enabled = true  \
        # persist task graphs to SQLite after each tick; enables `/plan resume <id>` (#3107)\n";
    let output = toml_src.replacen(
        "[orchestration]\n",
        &format!("[orchestration]\n{comment}"),
        1,
    );
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["orchestration.persistence_enabled".to_owned()],
    })
}

/// Add commented-out `[session.recap]` block if absent (#3064).
///
/// All recap fields have `#[serde(default)]` so existing configs parse without changes.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_session_recap_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: check both active and commented forms.
    if toml_src.contains("[session.recap]") || toml_src.contains("# [session.recap]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [session.recap] — show a recap when resuming a conversation (#3064).\n\
         # [session.recap]\n\
         # on_resume = true\n\
         # max_tokens = 200\n\
         # provider = \"\"\n\
         # max_input_messages = 20\n";
    let raw = toml_src.parse::<toml_edit::DocumentMut>()?.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["session.recap".to_owned()],
    })
}

/// Add commented-out MCP elicitation keys to `[mcp]` section if absent (#3141).
///
/// All elicitation fields have `#[serde(default)]` so existing configs parse without changes.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_mcp_elicitation_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: check for any elicitation key presence.
    if toml_src.contains("elicitation_enabled") || toml_src.contains("# elicitation_enabled") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Only inject under an existing [mcp] section.
    if !toml_src.contains("[mcp]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Guard against configs that have `[mcp]` but with Windows line endings or at EOF.
    if !toml_src.contains("[mcp]\n") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "# elicitation_enabled = false          \
        # opt-in: servers may request user input mid-task (#3141)\n\
        # elicitation_timeout = 120            # seconds to wait for user response\n\
        # elicitation_queue_capacity = 16      # beyond this limit requests are auto-declined\n\
        # elicitation_warn_sensitive_fields = true  # warn before prompting for password/token/etc.\n";
    let output = toml_src.replacen("[mcp]\n", &format!("[mcp]\n{comment}"), 1);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["mcp.elicitation".to_owned()],
    })
}

/// Add a commented-out `max_connect_attempts` key under `[mcp]` if absent (#3568).
///
/// This key was introduced alongside the MCP startup auto-retry feature. All prior
/// configs omit it and get the default value of `3`. This migration surfaces the key
/// as a comment so users can discover and tune it.
///
/// # Errors
///
/// Returns `Ok` with unchanged output when the key is already present or `[mcp]` is absent.
pub fn migrate_mcp_max_connect_attempts(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("max_connect_attempts") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    if !toml_src.contains("[mcp]\n") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "# max_connect_attempts = 3  \
        # startup retry count per server (1 = no retry, 1..=10, backoff: 500ms/1s/2s/...)\n";
    let output = toml_src.replacen("[mcp]\n", &format!("[mcp]\n{comment}"), 1);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["mcp".to_owned()],
    })
}

/// Add commented-out `startup_retry_backoff_ms` and `tool_timeout_secs` keys under `[mcp]`
/// if absent (#4004).
///
/// Both keys have `#[serde(default)]` and require no user action; this migration surfaces them
/// so operators can discover and tune the new retry and per-call timeout settings.
///
/// # Errors
///
/// Returns `Ok` with unchanged output when either key is already present or `[mcp]` is absent.
pub fn migrate_mcp_retry_and_tool_timeout(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    let has_backoff = toml_src.contains("startup_retry_backoff_ms");
    let has_timeout = toml_src.contains("tool_timeout_secs");

    if (has_backoff && has_timeout) || !toml_src.contains("[mcp]\n") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let mut output = toml_src.to_owned();
    let mut changed = false;

    if !has_backoff {
        let comment = "# startup_retry_backoff_ms = 1000  \
            # base backoff ms between startup retries (doubles per attempt, cap 8000 ms)\n";
        output = output.replacen("[mcp]\n", &format!("[mcp]\n{comment}"), 1);
        changed = true;
    }

    if !has_timeout {
        let comment = "# tool_timeout_secs = 60  \
            # per-call timeout for tools/call requests; when absent, per-server timeout is used\n";
        output = output.replacen("[mcp]\n", &format!("[mcp]\n{comment}"), 1);
        changed = true;
    }

    if changed {
        Ok(MigrationResult {
            output,
            changed_count: 1,
            sections_changed: vec!["mcp".to_owned()],
        })
    } else {
        Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        })
    }
}

/// Add a commented-out `[quality]` block if the config lacks it (#3228).
///
/// Introduced alongside the MARCH self-check pipeline (#3226). All `QualityConfig`
/// fields have `#[serde(default)]` so existing configs parse without changes; this
/// migration only surfaces the section so users can discover and enable it.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the
/// migration function convention for use in chained pipelines.
pub fn migrate_quality_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Idempotency: line-anchored check avoids false-positives on [quality.foo] subtables.
    if toml_src
        .lines()
        .any(|l| l.trim() == "[quality]" || l.trim() == "# [quality]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [quality] — MARCH Proposer+Checker self-check pipeline (#3226, #3228).\n\
         # [quality]\n\
         # self_check = false                    # enable post-response self-check\n\
         # trigger = \"has_retrieval\"             # has_retrieval | always | manual\n\
         # latency_budget_ms = 4000              # hard ceiling for the whole pipeline\n\
         # proposer_provider = \"\"                # optional: provider name from [[llm.providers]]\n\
         # checker_provider = \"\"                 # optional: provider name from [[llm.providers]]\n\
         # min_evidence = 0.6                    # 0.0..1.0; below → flag assertion\n\
         # async_run = false                     # true = fire-and-forget (non-blocking)\n\
         # per_call_timeout_ms = 2000            # per-LLM-call timeout\n\
         # max_assertions = 12                   # maximum assertions extracted from one response\n\
         # max_response_chars = 8000             # skip pipeline when response exceeds this\n\
         # cache_disabled_for_checker = true     # suppress prompt-cache on Checker provider\n\
         # flag_marker = \"[verify]\"              # marker appended when assertions are flagged\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["quality".to_owned()],
    })
}

/// Add a commented-out `[acp.subagents]` block if the config lacks it (#3304).
///
/// Introduced alongside the ACP sub-agent delegation feature (#3289). All `AcpSubagentsConfig`
/// fields have `#[serde(default)]` so existing configs parse without changes; this migration
/// only surfaces the section so users can discover and enable it.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the
/// migration function convention for use in chained pipelines.
pub fn migrate_acp_subagents_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[acp.subagents]" || l.trim() == "# [acp.subagents]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [acp.subagents] — sub-agent delegation via ACP protocol (#3289).\n\
         # [acp.subagents]\n\
         # enabled = false\n\
         #\n\
         # [[acp.subagents.presets]]\n\
         # name = \"inner\"                         # identifier used in /subagent commands\n\
         # command = \"cargo run --quiet -- --acp\" # shell command to spawn the sub-agent\n\
         # # cwd = \"/path/to/agent\"              # optional working directory\n\
         # # handshake_timeout_secs = 30          # initialize+session/new timeout\n\
         # # prompt_timeout_secs = 600            # single round-trip timeout\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["acp.subagents".to_owned()],
    })
}

/// Add a commented-out `[[hooks.permission_denied]]` block if the config lacks it (#3309).
///
/// Introduced alongside the reactive env hooks and MCP tool dispatch feature (#3303).
/// All hook arrays have `#[serde(default)]` so existing configs parse without changes;
/// this migration surfaces the section for discoverability.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the
/// migration function convention for use in chained pipelines.
pub fn migrate_hooks_permission_denied_config(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    if toml_src.lines().any(|l| {
        l.trim() == "[[hooks.permission_denied]]" || l.trim() == "# [[hooks.permission_denied]]"
    }) {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [[hooks.permission_denied]] — hook fired when a tool call is denied (#3303).\n\
         # Available env vars: ZEPH_TOOL, ZEPH_DENY_REASON, ZEPH_TOOL_INPUT_JSON.\n\
         # [[hooks.permission_denied]]\n\
         # [hooks.permission_denied.action]\n\
         # type = \"command\"\n\
         # command = \"echo denied: $ZEPH_TOOL\"\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["hooks.permission_denied".to_owned()],
    })
}

/// Add commented-out `[memory.graph]` retrieval strategy options if the config lacks them (#3317).
///
/// Introduced alongside the multi-strategy graph retrieval and experience memory feature (#3311).
/// All `MemoryGraphConfig` fields have `#[serde(default)]` so existing configs parse without
/// changes; this migration surfaces the new options for discoverability.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the
/// migration function convention for use in chained pipelines.
pub fn migrate_memory_graph_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("retrieval_strategy")
        || toml_src.contains("[memory.graph.beam_search]")
        || toml_src.contains("# [memory.graph.beam_search]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [memory.graph] retrieval strategy options (#3311).\n\
         # retrieval_strategy = \"synapse\"    # synapse | bfs | astar | watercircles | beam_search | hybrid\n\
         #\n\
         # [memory.graph.beam_search]        # active when retrieval_strategy = \"beam_search\"\n\
         # beam_width = 10                   # top-K candidates kept per hop\n\
         #\n\
         # [memory.graph.watercircles]       # active when retrieval_strategy = \"watercircles\"\n\
         # ring_limit = 0                    # max facts per ring; 0 = auto\n\
         #\n\
         # [memory.graph.experience]         # experience memory recording\n\
         # enabled = false\n\
         # evolution_sweep_enabled = false\n\
         # confidence_prune_threshold = 0.1  # prune edges below this threshold\n\
         # evolution_sweep_interval = 50     # turns between sweeps\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.graph.retrieval".to_owned()],
    })
}

/// Add a commented-out `[scheduler.daemon]` block if the config lacks it (#3332).
///
/// Introduced alongside the `zeph serve` daemon mode (#3332). All `DaemonConfig` fields
/// have defaults so existing configs parse without changes; this migration surfaces the
/// section so users can discover and configure the daemon process.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the
/// migration function convention for use in chained pipelines.
pub fn migrate_scheduler_daemon_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[scheduler.daemon]" || l.trim() == "# [scheduler.daemon]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [scheduler.daemon] — daemon process config for `zeph serve` (#3332).\n\
         # [scheduler.daemon]\n\
         # pid_file = \"/tmp/zeph-scheduler.pid\"   # PID file path (must be on a local filesystem)\n\
         # log_file = \"/tmp/zeph-scheduler.log\"   # daemon log file path (append-only; rotate externally)\n\
         # tick_secs = 60                           # scheduler tick interval in seconds (clamped 5..=3600)\n\
         # shutdown_grace_secs = 30                 # grace period after SIGTERM before process exits\n\
         # catch_up = true                          # replay missed cron tasks on daemon restart\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["scheduler.daemon".to_owned()],
    })
}

/// Add a commented-out `[memory.retrieval]` block if the config lacks it (#3340).
///
/// MemMachine-inspired retrieval-stage tuning: ANN candidate depth, search-prompt template,
/// and context snippet format. All fields have defaults so existing configs parse unchanged;
/// this migration surfaces the section for discoverability.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_memory_retrieval_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[memory.retrieval]" || l.trim() == "# [memory.retrieval]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [memory.retrieval] — MemMachine-inspired retrieval tuning (#3340, #3341).\n\
         # [memory.retrieval]\n\
         # depth = 0                          # ANN candidates fetched from the vector store, directly.\n\
         #                                    # 0 = legacy behavior (recall_limit * 2). Set to an explicit\n\
         #                                    # value >= recall_limit * 2 to enlarge the candidate pool.\n\
         # search_prompt_template = \"\"        # embedding query template; {query} = raw user query; empty = identity\n\
         # context_format = \"structured\"      # structured | plain — memory snippet rendering format\n\
         # query_bias_correction = true        # shift first-person queries towards user profile centroid (MM-F3)\n\
         # query_bias_profile_weight = 0.25    # blend weight [0.0, 1.0]; 0.0 = off, 1.0 = full centroid\n\
         # query_bias_centroid_ttl_secs = 300  # seconds before profile centroid cache is recomputed\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.retrieval".to_owned()],
    })
}

/// Add a commented-out `[memory.reasoning]` block if the config lacks it (#3369).
///
/// `ReasoningBank` distilled strategy memory was added in v0.19.3 (commit b99b2d30).
/// All fields have defaults so existing configs parse unchanged; this migration
/// surfaces the section for discoverability.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_memory_reasoning_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[memory.reasoning]" || l.trim() == "# [memory.reasoning]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [memory.reasoning] — ReasoningBank: distilled strategy memory (#3369).\n\
         # [memory.reasoning]\n\
         # enabled = false\n\
         # extract_provider = \"\"         # SLM: self-judge (JSON response) — leave blank to use primary\n\
         # distill_provider = \"\"         # SLM: strategy distillation — leave blank to use primary\n\
         # top_k = 3                      # strategies injected per turn\n\
         # store_limit = 1000             # max rows in reasoning_strategies table\n\
         # context_budget_tokens = 500\n\
         # extraction_timeout_secs = 30\n\
         # distill_timeout_secs = 30\n\
         # max_messages = 6\n\
         # min_messages = 2\n\
         # max_message_chars = 2000\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.reasoning".to_owned()],
    })
}

/// Insert commented-out `self_judge_window` and `min_assistant_chars` keys under an existing
/// `[memory.reasoning]` block when they are absent (#3383).
///
/// Configs that lack a `[memory.reasoning]` section are returned unchanged (the
/// [`migrate_memory_reasoning_config`] step is responsible for adding the section).
/// Idempotent when either key is already present.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_memory_reasoning_judge_config(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    let has_section = toml_src.lines().any(|l| l.trim() == "[memory.reasoning]");
    if !has_section {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Check if both keys are already present (active or commented).
    let has_window = toml_src.lines().any(|l| {
        let t = l.trim().trim_start_matches('#').trim();
        t.starts_with("self_judge_window")
    });
    let has_min_chars = toml_src.lines().any(|l| {
        let t = l.trim().trim_start_matches('#').trim();
        t.starts_with("min_assistant_chars")
    });
    if has_window && has_min_chars {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Append the new keys after the last line belonging to [memory.reasoning].
    // Strategy: find the last line of the [memory.reasoning] block (before the next section
    // header) and insert the commented-out keys after it.
    let lines: Vec<&str> = toml_src.lines().collect();
    let mut section_start = None;
    let mut insert_after = None;

    for (i, line) in lines.iter().enumerate() {
        if line.trim() == "[memory.reasoning]" {
            section_start = Some(i);
        }
        if let Some(start) = section_start {
            let trimmed = line.trim();
            // A new top-level section header ends the current section.
            if i > start && trimmed.starts_with('[') && !trimmed.starts_with("[[") {
                break;
            }
            insert_after = Some(i);
        }
    }

    let Some(insert_idx) = insert_after else {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    };

    let mut new_lines: Vec<String> = lines.iter().map(|l| (*l).to_owned()).collect();
    let mut additions = Vec::new();
    if !has_window {
        additions.push(
            "# self_judge_window = 2   # max recent messages passed to self-judge (#3383)"
                .to_owned(),
        );
    }
    if !has_min_chars {
        additions.push(
            "# min_assistant_chars = 50  # skip self-judge for short replies (#3383)".to_owned(),
        );
    }
    for (offset, line) in additions.iter().enumerate() {
        new_lines.insert(insert_idx + 1 + offset, line.clone());
    }

    let output = new_lines.join("\n") + if toml_src.ends_with('\n') { "\n" } else { "" };
    Ok(MigrationResult {
        output,
        changed_count: additions.len(),
        sections_changed: vec!["memory.reasoning".to_owned()],
    })
}

/// Append a commented-out `[memory.hebbian]` block to `toml_src` when it is absent (HL-F1/F2, #3344).
///
/// Idempotent: if a `[memory.hebbian]` or `# [memory.hebbian]` line already exists,
/// the input is returned unchanged with `changed_count = 0`.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_memory_hebbian_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[memory.hebbian]" || l.trim() == "# [memory.hebbian]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [memory.hebbian]                       # HL-F1/F2 (#3344) Hebbian edge reinforcement\n\
         # [memory.hebbian]\n\
         # enabled = false                        # opt-in master switch; no DB writes when false\n\
         # hebbian_lr = 0.1                       # weight increment per co-activation (0.01–0.5)\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.hebbian".to_owned()],
    })
}

/// Splice missing HL-F3/F4 consolidation fields into an existing `[memory.hebbian]` section
/// (HL-F3/F4, #3345).
///
/// Three branches:
/// - Section absent → no-op (handled by `migrate_memory_hebbian_config`).
/// - Section present but missing consolidation fields → append commented-out defaults.
/// - Section present with all fields → no-op.
///
/// # Errors
///
/// Infallible in practice; `Result` matches the migration convention.
pub fn migrate_memory_hebbian_consolidation_config(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    let has_section = toml_src.lines().any(|l| l.trim() == "[memory.hebbian]");

    if !has_section {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Check if all consolidation fields already present (active or commented).
    let has_interval = toml_src
        .lines()
        .any(|l| l.trim().starts_with("consolidation_interval_secs"));
    let has_threshold = toml_src
        .lines()
        .any(|l| l.trim().starts_with("consolidation_threshold"));
    let has_provider = toml_src
        .lines()
        .any(|l| l.trim().starts_with("consolidate_provider"));

    if has_interval && has_threshold && has_provider {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let extra = "\n# HL-F3/F4 consolidation fields (#3345) — splice into existing [memory.hebbian] section:\n\
        # consolidation_interval_secs = 3600   # how often the sweep runs (0 = disabled)\n\
        # consolidation_threshold = 5.0        # degree × avg_weight score to qualify\n\
        # consolidate_provider = \"fast\"        # provider name for LLM distillation\n\
        # max_candidates_per_sweep = 10\n\
        # consolidation_cooldown_secs = 86400  # re-consolidation cooldown per entity\n\
        # consolidation_prompt_timeout_secs = 30\n\
        # consolidation_max_neighbors = 20\n";

    let output = format!("{toml_src}{extra}");
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.hebbian".to_owned()],
    })
}

/// Splice missing HL-F5 spreading-activation fields into an existing `[memory.hebbian]` section
/// (HL-F5, #3346).
///
/// Three branches:
/// - Section absent → no-op (handled by `migrate_memory_hebbian_config`).
/// - Section present but missing HL-F5 fields → append commented-out defaults.
/// - Section present with all fields → no-op.
///
/// # Errors
///
/// Infallible in practice; `Result` matches the migration convention.
pub fn migrate_memory_hebbian_spread_config(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    let has_section = toml_src.lines().any(|l| l.trim() == "[memory.hebbian]");

    if !has_section {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Check if all HL-F5 fields are already present (active or commented).
    let has_spreading = toml_src
        .lines()
        .any(|l| l.trim().starts_with("spreading_activation"));
    let has_depth = toml_src
        .lines()
        .any(|l| l.trim().starts_with("spread_depth"));
    let has_budget = toml_src
        .lines()
        .any(|l| l.trim().starts_with("step_budget_ms"));
    let has_embed_timeout = toml_src
        .lines()
        .any(|l| l.trim().starts_with("embed_timeout_secs"));

    if has_spreading && has_depth && has_budget && has_embed_timeout {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let extra = "\n# HL-F5 spreading-activation fields (#3346) — splice into existing [memory.hebbian] section:\n\
        # spreading_activation = false   # opt-in BFS from top-1 ANN anchor; requires enabled=true\n\
        # spread_depth = 2               # BFS hops, clamped [1,6]\n\
        # spread_edge_types = []         # MAGMA edge types to traverse; empty = all\n\
        # step_budget_ms = 8             # per-step circuit-breaker timeout (anchor ANN / edges / vectors)\n\
        # embed_timeout_secs = 5         # timeout for the initial query embedding call (0 = disabled)\n";

    let output = format!("{toml_src}{extra}");
    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.hebbian.spreading_activation".to_owned()],
    })
}

/// Append a commented-out `[[hooks.turn_complete]]` block to `toml_src` when it is absent (#3308).
///
/// Idempotent: if a `[[hooks.turn_complete]]` or `# [[hooks.turn_complete]]` line already exists,
/// the input is returned unchanged with `changed_count = 0`.
///
/// The template uses a single `command` string (not `args`) to match the `HookAction::Command`
/// schema, and avoids embedding `$ZEPH_TURN_PREVIEW` directly in the command string to prevent
/// shell injection.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_hooks_turn_complete_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[[hooks.turn_complete]]" || l.trim() == "# [[hooks.turn_complete]]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [[hooks.turn_complete]] — hook fired after every agent turn completes (#3308).\n\
         # Available env vars: ZEPH_TURN_DURATION_MS, ZEPH_TURN_STATUS, ZEPH_TURN_PREVIEW,\n\
         # ZEPH_TURN_LLM_REQUESTS.\n\
         # Note: ZEPH_TURN_PREVIEW is available as env var but should not be embedded\n\
         # directly in the command string to avoid shell injection. Use a wrapper script instead.\n\
         # [[hooks.turn_complete]]\n\
         # command = \"osascript -e 'display notification \\\"Task complete\\\" with title \\\"Zeph\\\"'\"\n\
         # timeout_secs = 3\n\
         # fail_closed = false\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["hooks.turn_complete".to_owned()],
    })
}

/// Inject a commented-out `auto_consolidate_min_window` key into `[agent.focus]` if absent (#3313).
///
/// All `FocusConfig` fields have `#[serde(default)]`, so existing configs deserialize without
/// changes. This step surfaces the new field for users upgrading from older configs.
///
/// The comment is inserted *inside* the `[agent.focus]` section using [`insert_after_section`],
/// so it ends up in the correct table regardless of where that section appears in the file.
///
/// Idempotent: if `auto_consolidate_min_window` already appears anywhere in the source,
/// the input is returned unchanged with `changed_count = 0`.
/// No-op when `[agent.focus]` is absent or only exists as a comment line.
///
/// # Errors
///
/// This function is infallible in practice; the `Result` return type matches the migration
/// function convention for use in chained pipelines.
pub fn migrate_focus_auto_consolidate_min_window(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("auto_consolidate_min_window") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Only inject when [agent.focus] exists as a live section (not a comment).
    if !toml_src.lines().any(|l| l.trim() == "[agent.focus]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Minimum messages in a low-relevance window before Focus auto-consolidation \
         runs (#3313).\n\
         # auto_consolidate_min_window = 6\n";
    let output = insert_after_section(toml_src, "agent.focus", comment);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["agent.focus.auto_consolidate_min_window".to_owned()],
    })
}

/// Add `[session]` with `provider_persistence = true` to configs that lack the section (#3308).
///
/// Provider persistence was verified stable in CI-608 (restored persisted provider preference
/// from `SQLite`). Configs that already declare `[session]` or the commented `# [session]` are
/// returned unchanged.
///
/// # Errors
///
/// Infallible in practice; `Result` matches the migration convention.
pub fn migrate_session_provider_persistence(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[session]" || l.trim() == "# [session]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [session] — session-scoped user experience settings (#3308).\n\
         [session]\n\
         # Persist the last-used provider per channel across restarts.\n\
         # When true, the agent saves the active provider name to SQLite after each\n\
         # /provider switch and restores it on the next session start for the same channel.\n\
         provider_persistence = true\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["session".to_owned()],
    })
}

/// Add `[memory.retrieval]` with `query_bias_correction = true` if the section is absent.
///
/// `query_bias_correction` shifts first-person queries toward the user profile centroid
/// (MM-F3, #3341) and is verified working in CI-604/CI-605. It is a no-op when the persona
/// table is empty, so enabling it by default is safe.
///
/// Idempotent: the section header (live or commented) suppresses re-injection.
///
/// # Errors
///
/// Infallible in practice; `Result` matches the migration convention.
pub fn migrate_memory_retrieval_query_bias(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    // Already handled by migrate_memory_retrieval_config if the whole section is absent.
    // This step only splices the key into an existing [memory.retrieval] section.
    if !toml_src.lines().any(|l| l.trim() == "[memory.retrieval]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Idempotent: key already present (active or as comment).
    if toml_src
        .lines()
        .any(|l| l.trim().starts_with("query_bias_correction"))
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# MM-F3 (#3341): shift first-person queries toward the user profile centroid.\n\
         # No-op when the persona table is empty.\n\
         # query_bias_correction = true\n";
    let output = insert_after_section(toml_src, "memory.retrieval", comment);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.retrieval.query_bias_correction".to_owned()],
    })
}

/// Add a commented-out `[memory.persona]` stub to configs that lack the section.
///
/// The persona profile drives query-bias correction (MM-F3, #3341) and is verified working
/// in CI-604/CI-605. Adding the stub makes the section discoverable via `migrate-config`.
///
/// # Errors
///
/// Infallible in practice; `Result` matches the migration convention.
pub fn migrate_memory_persona_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src
        .lines()
        .any(|l| l.trim() == "[memory.persona]" || l.trim() == "# [memory.persona]")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# [memory.persona] — user persona profile for query-bias correction (#3341).\n\
         # Verified working in CI-604/CI-605. No-op when disabled.\n\
         # [memory.persona]\n\
         # enabled = true\n\
         # min_messages = 2       # minimum user messages before persona extraction fires\n\
         # min_confidence = 0.5   # minimum extraction confidence threshold (0.0–1.0)\n";
    let output = format!("{toml_src}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.persona".to_owned()],
    })
}

/// No-op migration for the optional `qdrant_api_key` field added in #3543.
///
/// The field has `#[serde(default)]` so existing configs parse as `None` without changes.
/// This step adds a commented-out hint under `[memory]` if not already present.
///
/// # Errors
///
/// Returns `MigrateError` if the TOML cannot be parsed or `[memory]` is malformed.
pub fn migrate_qdrant_api_key(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("qdrant_api_key") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let mut doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    if !doc.contains_key("memory") {
        doc.insert("memory", toml_edit::Item::Table(toml_edit::Table::new()));
    }

    let comment = "\n# Qdrant API key (optional; required when connecting to remote/managed Qdrant clusters).\n\
         # Leave empty for local Qdrant instances. Store the actual key in the vault:\n\
         #   zeph vault set ZEPH_QDRANT_API_KEY \"<key>\"\n\
         # qdrant_api_key = \"\"\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.qdrant_api_key".to_owned()],
    })
}

/// Add the `[goals]` section as commented-out defaults when it is absent.
///
/// # Errors
///
/// Returns [`MigrateError::Parse`] when `toml_src` is not valid TOML.
pub fn migrate_goals_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("[goals]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Long-horizon goal lifecycle tracking (#3567).\n\
         # [goals]\n\
         # enabled = false\n\
         # inject_into_system_prompt = true\n\
         # max_text_chars = 2000\n\
         # max_history = 50\n";

    Ok(MigrationResult {
        output: format!("{toml_src}{comment}"),
        changed_count: 1,
        sections_changed: vec!["goals".to_owned()],
    })
}

/// Add the `[tools.compression]` section as commented-out defaults when it is absent.
///
/// # Errors
///
/// Returns [`MigrateError::Parse`] when `toml_src` is not valid TOML.
pub fn migrate_tools_compression_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("tools.compression")
        || toml_src.contains("[tools]\n") && toml_src.contains("compression")
    {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# TACO self-evolving tool output compression (#3306).\n\
         # [tools.compression]\n\
         # enabled = false\n\
         # min_lines_to_compress = 10\n\
         # evolution_provider = \"\"\n\
         # evolution_min_interval_secs = 3600\n\
         # max_rules = 200\n";

    Ok(MigrationResult {
        output: format!("{toml_src}{comment}"),
        changed_count: 1,
        sections_changed: vec!["tools.compression".to_owned()],
    })
}

/// Add `orchestrator_provider` as a commented-out entry in `[orchestration]` when absent.
///
/// # Errors
///
/// Returns [`MigrateError::Parse`] when `toml_src` is not valid TOML.
pub fn migrate_orchestration_orchestrator_provider(
    toml_src: &str,
) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("orchestrator_provider") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Provider for scheduling-tier LLM calls (aggregation, predicate, verify fallback).\n\
         # Set to a cheap/fast model to reduce orchestration cost. Empty = primary provider.\n\
         # Add under the orchestration section in your config:\n\
         # orchestrator_provider = \"\"\n";

    Ok(MigrationResult {
        output: format!("{toml_src}{comment}"),
        changed_count: 1,
        sections_changed: vec!["orchestration".to_owned()],
    })
}

/// Add a commented-out `max_concurrent` hint to `[[llm.providers]]` entries when absent.
///
/// `max_concurrent` limits how many orchestrated sub-agent calls may be in-flight to a
/// given provider simultaneously. The field is optional (`None` = unlimited), so existing
/// configs continue to work without changes.
///
/// # Errors
///
/// Returns [`MigrateError::Parse`] when `toml_src` is not valid TOML.
pub fn migrate_provider_max_concurrent(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("max_concurrent") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    if !toml_src.contains("[[llm.providers]]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Optional: maximum concurrent sub-agent calls to this provider (admission control).\n\
         # Remove the comment to enable; omit or set to 0 for unlimited.\n\
         # max_concurrent = 4\n";

    Ok(MigrationResult {
        output: format!("{toml_src}{comment}"),
        changed_count: 1,
        sections_changed: vec!["llm.providers".to_owned()],
    })
}

// ── Migration trait and registry ────────────────────────────────────────────────────────────────

/// A single idempotent config migration step.
///
/// Each impl wraps one of the free-standing `migrate_*` functions and gives it a stable
/// name used in logs and test assertions. The trait is object-safe so that steps can be
/// stored in a `Vec<Box<dyn Migration + Send + Sync>>`.
///
/// # Contract for implementors
///
/// - `apply` **must** be idempotent: calling it twice on the same source must return the
///   same output as calling it once.
/// - On a no-op (nothing to migrate), `apply` returns a [`MigrationResult`] with
///   `changed_count == 0`.
///
/// # Examples
///
/// ```rust
/// use zeph_config::migrate::{Migration, MIGRATIONS};
///
/// // The registry is ordered chronologically; apply each step in sequence.
/// let mut toml = "[agent]\nname = \"zeph\"\n".to_owned();
/// for m in MIGRATIONS.iter() {
///     toml = m.apply(&toml).expect("migration failed").output;
/// }
/// ```
pub trait Migration: Send + Sync {
    /// Human-readable identifier used in diagnostics and ordering assertions.
    fn name(&self) -> &'static str;

    /// Apply this migration step to `toml_src`.
    ///
    /// # Errors
    ///
    /// Propagates any [`MigrateError`] from the underlying free function.
    fn apply(&self, toml_src: &str) -> Result<MigrationResult, MigrateError>;
}

mod steps;
use steps::{
    MigrateAcpSubagentsConfig, MigrateAgentBudgetHint, MigrateAgentRetryToToolsRetry,
    MigrateAutodreamConfig, MigrateCocoonProviderNotice, MigrateCompressionPredictorConfig,
    MigrateDatabaseUrl, MigrateEgressConfig, MigrateEmbedProviderRename, MigrateFiveSignalConfig,
    MigrateFocusAutoConsolidateMinWindow, MigrateForgettingConfig, MigrateGoalsConfig,
    MigrateGonkagateToGonka, MigrateHooksPermissionDeniedConfig, MigrateHooksTurnComplete,
    MigrateMagicDocsConfig, MigrateMcpElicitationConfig, MigrateMcpMaxConnectAttempts,
    MigrateMcpRetryAndToolTimeout, MigrateMcpTrustLevels, MigrateMemoryGraph, MigrateMemoryHebbian,
    MigrateMemoryHebbianConsolidation, MigrateMemoryHebbianSpread, MigrateMemoryPersonaConfig,
    MigrateMemoryReasoning, MigrateMemoryReasoningJudge, MigrateMemoryRetrieval,
    MigrateMemoryRetrievalQueryBias, MigrateMicrocompactConfig, MigrateOrchestrationPersistence,
    MigrateOrchestratorProvider, MigrateOtelFilter, MigratePlannerModelToProvider,
    MigrateProviderMaxConcurrent, MigrateQdrantApiKey, MigrateQualityConfig, MigrateSandboxConfig,
    MigrateSandboxEgressFilter, MigrateSchedulerDaemon, MigrateSessionProviderPersistence,
    MigrateSessionRecapConfig, MigrateShellTransactional, MigrateSttToProvider,
    MigrateSupervisorConfig, MigrateTelemetryConfig, MigrateToolsCompressionConfig,
    MigrateTraceMetadata, MigrateVigilConfig,
};

/// Step 45: add an advisory comment above `GonkaGate` provider entries pointing users to
/// the native Gonka provider option.
///
/// This is advisory only — no automatic conversion is performed. The comment informs
/// users that a native Gonka provider is now available and links to migration docs.
pub(crate) fn migrate_gonkagate_to_gonka(toml_src: &str) -> MigrationResult {
    // Advisory-only: add a comment before GonkaGate provider entries when found.
    const MARKER: &str = "# [migration] GonkaGate detected: consider migrating to type = \"gonka\"";

    if !toml_src.contains("gonkagate") {
        return MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: vec![],
        };
    }

    let mut changed_count = 0;
    let mut lines: Vec<String> = toml_src.lines().map(str::to_owned).collect();

    // Walk backwards from each line containing "gonkagate" to find the nearest preceding
    // [[llm.providers]] table header and insert the advisory comment before it.
    // We iterate indices in reverse so that inserting at a position does not shift later targets.
    let indices: Vec<usize> = lines
        .iter()
        .enumerate()
        .filter(|(_, l)| l.contains("gonkagate"))
        .map(|(i, _)| i)
        .rev()
        .collect();

    for gonka_idx in indices {
        // Find the most recent [[...]] header at or before gonka_idx.
        let header_idx = (0..=gonka_idx)
            .rev()
            .find(|&i| lines[i].starts_with("[["))
            .unwrap_or(gonka_idx);

        // Skip if the comment is already present just before the header.
        let already_marked = header_idx > 0 && lines[header_idx - 1].contains(MARKER);
        if already_marked {
            continue;
        }

        lines.insert(
            header_idx,
            format!("{MARKER} (see docs/guides/gonka-native.md)"),
        );
        changed_count += 1;
    }

    let output = lines.join("\n");
    let output = if toml_src.ends_with('\n') {
        format!("{output}\n")
    } else {
        output
    };

    MigrationResult {
        output,
        changed_count,
        sections_changed: if changed_count > 0 {
            vec!["llm".into()]
        } else {
            vec![]
        },
    }
}

/// Advisory-only no-op step for Cocoon provider introduction.
///
/// Returns the input unchanged. Exists so the migration registry stays sequential
/// and `--migrate-config` informs users that Cocoon is now available.
///
/// # Errors
///
/// This function never returns an error.
pub fn migrate_cocoon_provider_notice(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    Ok(MigrationResult {
        output: toml_src.to_owned(),
        changed_count: 0,
        sections_changed: vec![],
    })
}

/// Adds a commented-out `[telemetry.trace_metadata]` example to configs that have a
/// `[telemetry]` section but no `trace_metadata` key (#4160).
///
/// # Errors
///
/// Returns [`MigrateError`] if the TOML source cannot be parsed.
pub fn migrate_trace_metadata(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("trace_metadata") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;

    if !doc.contains_key("telemetry") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Custom key/value pairs attached as OpenTelemetry resource attributes (#4160).\n\
        # Appear on every exported span. Values are plaintext — do not store secrets here.\n\
        # [telemetry.trace_metadata]\n\
        # \"deployment.environment\" = \"production\"\n\
        # \"vcs.revision\" = \"abc1234\"\n";
    let raw = doc.to_string();
    let output = insert_after_section(&raw, "telemetry", comment);

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["telemetry.trace_metadata".to_owned()],
    })
}

/// Ordered registry of all sequential migration steps (steps 1–47).
///
/// Each entry wraps the corresponding free function and is evaluated lazily at first access.
/// The ordering is chronological; the dispatch loop in `src/commands/migrate.rs` iterates
/// this registry rather than calling free functions individually.
///
/// # Examples
///
/// ```rust
/// use zeph_config::migrate::MIGRATIONS;
///
/// // Every step in the registry has a non-empty name.
/// for m in MIGRATIONS.iter() {
///     assert!(!m.name().is_empty());
/// }
/// ```
pub static MIGRATIONS: std::sync::LazyLock<Vec<Box<dyn Migration + Send + Sync>>> =
    std::sync::LazyLock::new(|| {
        vec![
            // Steps 1–25 (pre-existing migrations)
            Box::new(MigrateSttToProvider) as Box<dyn Migration + Send + Sync>,
            Box::new(MigratePlannerModelToProvider),
            Box::new(MigrateMcpTrustLevels),
            Box::new(MigrateAgentRetryToToolsRetry),
            Box::new(MigrateDatabaseUrl),
            Box::new(MigrateShellTransactional),
            Box::new(MigrateAgentBudgetHint),
            Box::new(MigrateForgettingConfig),
            Box::new(MigrateCompressionPredictorConfig),
            Box::new(MigrateMicrocompactConfig),
            Box::new(MigrateAutodreamConfig),
            Box::new(MigrateMagicDocsConfig),
            Box::new(MigrateTelemetryConfig),
            Box::new(MigrateSupervisorConfig),
            Box::new(MigrateOtelFilter),
            Box::new(MigrateEgressConfig),
            Box::new(MigrateVigilConfig),
            Box::new(MigrateSandboxConfig),
            Box::new(MigrateSandboxEgressFilter),
            Box::new(MigrateOrchestrationPersistence),
            Box::new(MigrateSessionRecapConfig),
            Box::new(MigrateMcpElicitationConfig),
            Box::new(MigrateQualityConfig),
            Box::new(MigrateAcpSubagentsConfig),
            Box::new(MigrateHooksPermissionDeniedConfig),
            // Steps 26–35 (most recent migrations, pre-stable-defaults)
            Box::new(MigrateMemoryGraph),
            Box::new(MigrateSchedulerDaemon),
            Box::new(MigrateMemoryRetrieval),
            Box::new(MigrateMemoryReasoning),
            Box::new(MigrateMemoryReasoningJudge),
            Box::new(MigrateMemoryHebbian),
            Box::new(MigrateMemoryHebbianConsolidation),
            Box::new(MigrateMemoryHebbianSpread),
            Box::new(MigrateHooksTurnComplete),
            Box::new(MigrateFocusAutoConsolidateMinWindow),
            // Steps 36–38 (stable-defaults: flip verified-stable config keys to on)
            Box::new(MigrateSessionProviderPersistence),
            Box::new(MigrateMemoryRetrievalQueryBias),
            Box::new(MigrateMemoryPersonaConfig),
            // Step 39 — optional Qdrant API key (#3543)
            Box::new(MigrateQdrantApiKey),
            // Step 40 — MCP startup auto-retry max_connect_attempts (#3568)
            Box::new(MigrateMcpMaxConnectAttempts),
            // Steps 41–42 — goal lifecycle and TACO compression (#3567, #3306)
            Box::new(MigrateGoalsConfig),
            Box::new(MigrateToolsCompressionConfig),
            // Step 43 — orchestrator_provider for scheduling-tier LLM calls (#3300)
            Box::new(MigrateOrchestratorProvider),
            // Step 44 — max_concurrent per-provider admission control hint (#3299)
            Box::new(MigrateProviderMaxConcurrent),
            // Step 45 — advisory notice for GonkaGate → native Gonka upgrade path (#3613)
            Box::new(MigrateGonkagateToGonka),
            // Step 46 — advisory notice for Cocoon decentralized inference provider (#3671)
            Box::new(MigrateCocoonProviderNotice),
            // Step 47 — telemetry.trace_metadata OTEL resource attributes (#4160)
            Box::new(MigrateTraceMetadata),
            // Step 48 — five-signal SYNAPSE retrieval advisory (#4374)
            Box::new(MigrateFiveSignalConfig),
            // Step 49 — rename embed_provider → embedding_provider (#4480)
            Box::new(MigrateEmbedProviderRename),
            // Step 50 — add mcp startup_retry_backoff_ms and tool_timeout_secs (#4004)
            Box::new(MigrateMcpRetryAndToolTimeout),
        ]
    });

/// Add a commented-out `[memory.five_signal]` section if absent (#4374).
///
/// All five-signal fields have `#[serde(default)]` so existing configs parse without changes.
/// This step surfaces the new section for users upgrading from older configs.
///
/// # Errors
///
/// Returns `MigrateError::Parse` if the TOML cannot be parsed.
pub fn migrate_five_signal_config(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    if toml_src.contains("[memory.five_signal]") || toml_src.contains("# [memory.five_signal]") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let doc = toml_src.parse::<toml_edit::DocumentMut>()?;
    if !doc.contains_key("memory") {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    let comment = "\n# Five-signal SYNAPSE retrieval (#4374). Disabled by default.\n\
         # [memory.five_signal]\n\
         # enabled = false\n\
         # w_recency = 0.35\n\
         # w_relevance = 0.35\n\
         # w_frequency = 0.15\n\
         # w_causal = 0.10\n\
         # w_novelty = 0.05\n\
         # causal_bfs_max_depth = 10\n\
         # neutral_causal_distance = 5\n\
         # novelty_decay_rate = 0.1\n\
         #\n\
         # [memory.five_signal.consolidation_daemon]\n\
         # enabled = false\n\
         # interval_seconds = 7200\n\
         # batch_size = 500\n\
         # promotion_score_threshold = 0.70\n\
         # demotion_score_threshold = 0.20\n\
         # top_k_per_run = 500\n";
    let raw = doc.to_string();
    let output = format!("{raw}{comment}");

    Ok(MigrationResult {
        output,
        changed_count: 1,
        sections_changed: vec!["memory.five_signal".to_owned()],
    })
}

/// Rename `embed_provider` → `embedding_provider` in `[memory.semantic]`, `[index]`,
/// `[llm.coe]`, and `trace_extraction_embed_provider` → `trace_extraction_embedding_provider`
/// in `[learning]` (#4480).
///
/// All four keys are renamed in a single pass. Keys that are already using the new name,
/// or that do not appear in the config, are left untouched (idempotent).
///
/// # Errors
///
/// This implementation never returns an error; the `Result` return type
/// satisfies the [`Migration`] trait contract.
pub fn migrate_embed_provider_rename(toml_src: &str) -> Result<MigrationResult, MigrateError> {
    // Fast-path: nothing to do when none of the old names are present.
    let has_old =
        toml_src.contains("embed_provider") || toml_src.contains("trace_extraction_embed_provider");
    if !has_old {
        return Ok(MigrationResult {
            output: toml_src.to_owned(),
            changed_count: 0,
            sections_changed: Vec::new(),
        });
    }

    // Line-oriented rename: replace `embed_provider` with `embedding_provider` and
    // `trace_extraction_embed_provider` with `trace_extraction_embedding_provider`.
    // Only rename standalone key occurrences (key = value lines), not values or comments.
    let mut changed_count = 0usize;
    let mut sections_changed = Vec::new();

    let output = toml_src
        .lines()
        .map(|line| {
            let trimmed = line.trim_start();
            // Rename trace_extraction_embed_provider first (longer prefix must come first)
            if trimmed.starts_with("trace_extraction_embed_provider") {
                let replaced = line.replacen(
                    "trace_extraction_embed_provider",
                    "trace_extraction_embedding_provider",
                    1,
                );
                changed_count += 1;
                if !sections_changed.contains(&"learning".to_owned()) {
                    sections_changed.push("learning".to_owned());
                }
                return replaced;
            }
            if trimmed.starts_with("embed_provider") {
                let replaced = line.replacen("embed_provider", "embedding_provider", 1);
                changed_count += 1;
                return replaced;
            }
            line.to_owned()
        })
        .collect::<Vec<_>>()
        .join("\n");

    // Preserve trailing newline if the original had one.
    let output = if toml_src.ends_with('\n') && !output.ends_with('\n') {
        format!("{output}\n")
    } else {
        output
    };

    Ok(MigrationResult {
        output,
        changed_count,
        sections_changed,
    })
}

// Helper to create a formatted value (used in tests).
#[cfg(test)]
fn make_formatted_str(s: &str) -> Value {
    use toml_edit::Formatted;
    Value::String(Formatted::new(s.to_owned()))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn migrations_registry_has_all_steps() {
        assert_eq!(
            MIGRATIONS.len(),
            50,
            "MIGRATIONS registry must contain all 50 sequential steps"
        );
        for m in MIGRATIONS.iter() {
            assert!(
                !m.name().is_empty(),
                "each migration must have a non-empty name"
            );
        }
    }

    #[test]
    fn migrations_registry_applies_to_empty_config() {
        let mut toml = String::new();
        for m in MIGRATIONS.iter() {
            toml = m
                .apply(&toml)
                .expect("migration must not fail on empty config")
                .output;
        }
        // After all steps, the output should at minimum be valid TOML (parseable).
        toml.parse::<toml_edit::DocumentMut>()
            .expect("registry output must be valid TOML");
    }

    #[test]
    fn empty_config_gets_sections_as_comments() {
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate("").expect("migrate empty");
        // Should have added sections since reference is non-empty.
        assert!(result.changed_count > 0 || !result.sections_changed.is_empty());
        // Output should mention at least agent section.
        assert!(
            result.output.contains("[agent]") || result.output.contains("# [agent]"),
            "expected agent section in output, got:\n{}",
            result.output
        );
    }

    #[test]
    fn existing_values_not_overwritten() {
        let user = r#"
[agent]
name = "MyAgent"
max_tool_iterations = 5
"#;
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        // Original name preserved.
        assert!(
            result.output.contains("name = \"MyAgent\""),
            "user value should be preserved"
        );
        assert!(
            result.output.contains("max_tool_iterations = 5"),
            "user value should be preserved"
        );
        // Should not appear as commented default.
        assert!(
            !result.output.contains("# max_tool_iterations = 10"),
            "already-set key should not appear as comment"
        );
    }

    #[test]
    fn missing_nested_key_added_as_comment() {
        // User has [memory] but is missing some keys.
        let user = r#"
[memory]
sqlite_path = ".zeph/data/zeph.db"
"#;
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        // history_limit should be added as comment since it's in reference.
        assert!(
            result.output.contains("# history_limit"),
            "missing key should be added as comment, got:\n{}",
            result.output
        );
    }

    #[test]
    fn unknown_user_keys_preserved() {
        let user = r#"
[agent]
name = "Test"
my_custom_key = "preserved"
"#;
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        assert!(
            result.output.contains("my_custom_key = \"preserved\""),
            "custom user keys must not be removed"
        );
    }

    #[test]
    fn idempotent() {
        let migrator = ConfigMigrator::new();
        let first = migrator
            .migrate("[agent]\nname = \"Zeph\"\n")
            .expect("first migrate");
        let second = migrator.migrate(&first.output).expect("second migrate");
        assert_eq!(
            first.output, second.output,
            "idempotent: full output must be identical on second run"
        );
    }

    #[test]
    fn malformed_input_returns_error() {
        let migrator = ConfigMigrator::new();
        let err = migrator
            .migrate("[[invalid toml [[[")
            .expect_err("should error");
        assert!(
            matches!(err, MigrateError::Parse(_)),
            "expected Parse error"
        );
    }

    #[test]
    fn array_of_tables_preserved() {
        let user = r#"
[mcp]
allowed_commands = ["npx"]

[[mcp.servers]]
id = "my-server"
command = "npx"
args = ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
"#;
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        // User's [[mcp.servers]] entry must survive.
        assert!(
            result.output.contains("[[mcp.servers]]"),
            "array-of-tables entries must be preserved"
        );
        assert!(result.output.contains("id = \"my-server\""));
    }

    #[test]
    fn canonical_ordering_applied() {
        // Put memory before agent intentionally.
        let user = r#"
[memory]
sqlite_path = ".zeph/data/zeph.db"

[agent]
name = "Test"
"#;
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        // agent should appear before memory in canonical order.
        let agent_pos = result.output.find("[agent]");
        let memory_pos = result.output.find("[memory]");
        if let (Some(a), Some(m)) = (agent_pos, memory_pos) {
            assert!(a < m, "agent section should precede memory section");
        }
    }

    #[test]
    fn value_to_toml_string_formats_correctly() {
        use toml_edit::Formatted;

        let s = make_formatted_str("hello");
        assert_eq!(value_to_toml_string(&s), "\"hello\"");

        let i = Value::Integer(Formatted::new(42_i64));
        assert_eq!(value_to_toml_string(&i), "42");

        let b = Value::Boolean(Formatted::new(true));
        assert_eq!(value_to_toml_string(&b), "true");

        let f = Value::Float(Formatted::new(1.0_f64));
        assert_eq!(value_to_toml_string(&f), "1.0");

        let f2 = Value::Float(Formatted::new(157_f64 / 50.0));
        assert_eq!(value_to_toml_string(&f2), "3.14");

        let arr: Array = ["a", "b"].iter().map(|s| make_formatted_str(s)).collect();
        let arr_val = Value::Array(arr);
        assert_eq!(value_to_toml_string(&arr_val), r#"["a", "b"]"#);

        let empty_arr = Value::Array(Array::new());
        assert_eq!(value_to_toml_string(&empty_arr), "[]");
    }

    #[test]
    fn idempotent_full_output_unchanged() {
        // Stronger idempotency: the entire output string must not change on a second pass.
        let migrator = ConfigMigrator::new();
        let first = migrator
            .migrate("[agent]\nname = \"Zeph\"\n")
            .expect("first migrate");
        let second = migrator.migrate(&first.output).expect("second migrate");
        assert_eq!(
            first.output, second.output,
            "full output string must be identical after second migration pass"
        );
    }

    #[test]
    fn full_config_produces_zero_additions() {
        // Migrating the reference config itself should add nothing new.
        let reference = include_str!("../../config/default.toml");
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(reference).expect("migrate reference");
        assert_eq!(
            result.changed_count, 0,
            "migrating the canonical reference should add nothing (changed_count = {})",
            result.changed_count
        );
        assert!(
            result.sections_changed.is_empty(),
            "migrating the canonical reference should report no sections_changed: {:?}",
            result.sections_changed
        );
    }

    #[test]
    fn empty_config_changed_count_is_positive() {
        // Stricter variant of empty_config_gets_sections_as_comments.
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate("").expect("migrate empty");
        assert!(
            result.changed_count > 0,
            "empty config must report changed_count > 0"
        );
    }

    // IMPL-04: verify that [security.guardrail] is injected as commented defaults
    // for a pre-guardrail config that has [security] but no [security.guardrail].
    #[test]
    fn security_without_guardrail_gets_guardrail_commented() {
        let user = "[security]\nredact_secrets = true\n";
        let migrator = ConfigMigrator::new();
        let result = migrator.migrate(user).expect("migrate");
        // The generic diff mechanism must add guardrail keys as commented defaults.
        assert!(
            result.output.contains("guardrail"),
            "migration must add guardrail keys for configs without [security.guardrail]: \
             got:\n{}",
            result.output
        );
    }

    #[test]
    fn migrate_reference_contains_tools_policy() {
        // IMP-NO-MIGRATE-CONFIG: verify that the embedded default.toml (the canonical reference
        // used by ConfigMigrator) contains a [tools.policy] section. This ensures that
        // `zeph --migrate-config` will surface the section to users as a discoverable commented
        // block, even if it cannot be injected as a live sub-table via toml_edit's round-trip.
        let reference = include_str!("../../config/default.toml");
        assert!(
            reference.contains("[tools.policy]"),
            "default.toml must contain [tools.policy] section so migrate-config can surface it"
        );
        assert!(
            reference.contains("enabled = false"),
            "tools.policy section must include enabled = false default"
        );
    }

    #[test]
    fn migrate_reference_contains_probe_section() {
        // default.toml must contain the probe section comment block so users can discover it
        // when reading the file directly or after running --migrate-config.
        let reference = include_str!("../../config/default.toml");
        assert!(
            reference.contains("[memory.compression.probe]"),
            "default.toml must contain [memory.compression.probe] section comment"
        );
        assert!(
            reference.contains("hard_fail_threshold"),
            "probe section must include hard_fail_threshold default"
        );
    }

    // ─── migrate_llm_to_providers ─────────────────────────────────────────────

    #[test]
    fn migrate_llm_no_llm_section_is_noop() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_llm_already_new_format_is_noop() {
        let src = r#"
[llm]
[[llm.providers]]
type = "ollama"
model = "qwen3:8b"
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
    }

    #[test]
    fn migrate_llm_ollama_produces_providers_block() {
        let src = r#"
[llm]
provider = "ollama"
model = "qwen3:8b"
base_url = "http://localhost:11434"
embedding_model = "nomic-embed-text"
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            result.output.contains("[[llm.providers]]"),
            "should contain [[llm.providers]]:\n{}",
            result.output
        );
        assert!(
            result.output.contains("type = \"ollama\""),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("model = \"qwen3:8b\""),
            "{}",
            result.output
        );
    }

    #[test]
    fn migrate_llm_claude_produces_providers_block() {
        let src = r#"
[llm]
provider = "claude"

[llm.cloud]
model = "claude-sonnet-4-6"
max_tokens = 8192
server_compaction = true
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            result.output.contains("[[llm.providers]]"),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("type = \"claude\""),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("model = \"claude-sonnet-4-6\""),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("server_compaction = true"),
            "{}",
            result.output
        );
    }

    #[test]
    fn migrate_llm_openai_copies_fields() {
        let src = r#"
[llm]
provider = "openai"

[llm.openai]
base_url = "https://api.openai.com/v1"
model = "gpt-4o"
max_tokens = 4096
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            result.output.contains("type = \"openai\""),
            "{}",
            result.output
        );
        assert!(
            result
                .output
                .contains("base_url = \"https://api.openai.com/v1\""),
            "{}",
            result.output
        );
    }

    #[test]
    fn migrate_llm_gemini_copies_fields() {
        let src = r#"
[llm]
provider = "gemini"

[llm.gemini]
model = "gemini-2.0-flash"
max_tokens = 8192
base_url = "https://generativelanguage.googleapis.com"
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            result.output.contains("type = \"gemini\""),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("model = \"gemini-2.0-flash\""),
            "{}",
            result.output
        );
    }

    #[test]
    fn migrate_llm_compatible_copies_multiple_entries() {
        let src = r#"
[llm]
provider = "compatible"

[[llm.compatible]]
name = "proxy-a"
base_url = "http://proxy-a:8080/v1"
model = "llama3"
max_tokens = 4096

[[llm.compatible]]
name = "proxy-b"
base_url = "http://proxy-b:8080/v1"
model = "mistral"
max_tokens = 2048
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        // Both compatible entries should be emitted.
        let count = result.output.matches("[[llm.providers]]").count();
        assert_eq!(
            count, 2,
            "expected 2 [[llm.providers]] blocks:\n{}",
            result.output
        );
        assert!(
            result.output.contains("name = \"proxy-a\""),
            "{}",
            result.output
        );
        assert!(
            result.output.contains("name = \"proxy-b\""),
            "{}",
            result.output
        );
    }

    #[test]
    fn migrate_llm_mixed_format_errors() {
        // Legacy + new format together should produce an error.
        let src = r#"
[llm]
provider = "ollama"

[[llm.providers]]
type = "ollama"
"#;
        assert!(
            migrate_llm_to_providers(src).is_err(),
            "mixed format must return error"
        );
    }

    // ─── migrate_stt_to_provider ──────────────────────────────────────────────

    #[test]
    fn stt_migration_no_stt_section_returns_unchanged() {
        let src = "[llm]\n\n[[llm.providers]]\ntype = \"openai\"\nname = \"quality\"\nmodel = \"gpt-5.4\"\n";
        let result = migrate_stt_to_provider(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn stt_migration_no_model_or_base_url_returns_unchanged() {
        let src = "[llm]\n\n[[llm.providers]]\ntype = \"openai\"\nname = \"quality\"\n\n[llm.stt]\nprovider = \"quality\"\nlanguage = \"en\"\n";
        let result = migrate_stt_to_provider(src).unwrap();
        assert_eq!(result.changed_count, 0);
    }

    #[test]
    fn stt_migration_moves_model_to_provider_entry() {
        let src = r#"
[llm]

[[llm.providers]]
type = "openai"
name = "quality"
model = "gpt-5.4"

[llm.stt]
provider = "quality"
model = "gpt-4o-mini-transcribe"
language = "en"
"#;
        let result = migrate_stt_to_provider(src).unwrap();
        assert_eq!(result.changed_count, 1);
        // stt_model should appear in providers entry.
        assert!(
            result.output.contains("stt_model"),
            "stt_model must be in output"
        );
        // model should be removed from [llm.stt].
        // The output should parse cleanly.
        let doc: toml_edit::DocumentMut = result.output.parse().unwrap();
        let stt = doc
            .get("llm")
            .and_then(toml_edit::Item::as_table)
            .and_then(|l| l.get("stt"))
            .and_then(toml_edit::Item::as_table)
            .unwrap();
        assert!(
            stt.get("model").is_none(),
            "model must be removed from [llm.stt]"
        );
        assert_eq!(
            stt.get("provider").and_then(toml_edit::Item::as_str),
            Some("quality")
        );
    }

    #[test]
    fn stt_migration_creates_new_provider_when_no_match() {
        let src = r#"
[llm]

[[llm.providers]]
type = "ollama"
name = "local"
model = "qwen3:8b"

[llm.stt]
provider = "whisper"
model = "whisper-1"
base_url = "https://api.openai.com/v1"
language = "en"
"#;
        let result = migrate_stt_to_provider(src).unwrap();
        assert!(
            result.output.contains("openai-stt"),
            "new entry name must be openai-stt"
        );
        assert!(
            result.output.contains("stt_model"),
            "stt_model must be in output"
        );
    }

    #[test]
    fn stt_migration_candle_whisper_creates_candle_entry() {
        let src = r#"
[llm]

[llm.stt]
provider = "candle-whisper"
model = "openai/whisper-tiny"
language = "auto"
"#;
        let result = migrate_stt_to_provider(src).unwrap();
        assert!(
            result.output.contains("local-whisper"),
            "candle entry name must be local-whisper"
        );
        assert!(result.output.contains("candle"), "type must be candle");
    }

    #[test]
    fn stt_migration_w2_assigns_explicit_name() {
        // Provider has no explicit name (type = "openai") — migration must assign one.
        let src = r#"
[llm]

[[llm.providers]]
type = "openai"
model = "gpt-5.4"

[llm.stt]
provider = "openai"
model = "whisper-1"
language = "auto"
"#;
        let result = migrate_stt_to_provider(src).unwrap();
        let doc: toml_edit::DocumentMut = result.output.parse().unwrap();
        let providers = doc
            .get("llm")
            .and_then(toml_edit::Item::as_table)
            .and_then(|l| l.get("providers"))
            .and_then(toml_edit::Item::as_array_of_tables)
            .unwrap();
        let entry = providers
            .iter()
            .find(|t| t.get("stt_model").is_some())
            .unwrap();
        // Must have an explicit `name` field (W2).
        assert!(
            entry.get("name").is_some(),
            "migrated entry must have explicit name"
        );
    }

    #[test]
    fn stt_migration_removes_base_url_from_stt_table() {
        // MEDIUM: verify that base_url is stripped from [llm.stt] after migration.
        let src = r#"
[llm]

[[llm.providers]]
type = "openai"
name = "quality"
model = "gpt-5.4"

[llm.stt]
provider = "quality"
model = "whisper-1"
base_url = "https://api.openai.com/v1"
language = "en"
"#;
        let result = migrate_stt_to_provider(src).unwrap();
        let doc: toml_edit::DocumentMut = result.output.parse().unwrap();
        let stt = doc
            .get("llm")
            .and_then(toml_edit::Item::as_table)
            .and_then(|l| l.get("stt"))
            .and_then(toml_edit::Item::as_table)
            .unwrap();
        assert!(
            stt.get("model").is_none(),
            "model must be removed from [llm.stt]"
        );
        assert!(
            stt.get("base_url").is_none(),
            "base_url must be removed from [llm.stt]"
        );
    }

    #[test]
    fn migrate_planner_model_to_provider_with_field() {
        let input = r#"
[orchestration]
enabled = true
planner_model = "gpt-4o"
max_tasks = 20
"#;
        let result = migrate_planner_model_to_provider(input).expect("migration must succeed");
        assert_eq!(result.changed_count, 1, "changed_count must be 1");
        assert!(
            !result.output.contains("planner_model = "),
            "planner_model key must be removed from output"
        );
        assert!(
            result.output.contains("# planner_provider"),
            "commented-out planner_provider entry must be present"
        );
        assert!(
            result.output.contains("gpt-4o"),
            "old value must appear in the comment"
        );
        assert!(
            result.output.contains("MIGRATED"),
            "comment must include MIGRATED marker"
        );
    }

    #[test]
    fn migrate_planner_model_to_provider_no_op() {
        let input = r"
[orchestration]
enabled = true
max_tasks = 20
";
        let result = migrate_planner_model_to_provider(input).expect("migration must succeed");
        assert_eq!(
            result.changed_count, 0,
            "changed_count must be 0 when field is absent"
        );
        assert_eq!(
            result.output, input,
            "output must equal input when nothing to migrate"
        );
    }

    #[test]
    fn migrate_error_invalid_structure_formats_correctly() {
        // HIGH: verify that MigrateError::InvalidStructure exists, matches correctly, and
        // produces a human-readable message. The error path is triggered when the [llm] item
        // is present but cannot be obtained as a mutable table (defensive guard replacing the
        // previous .expect() calls that would have panicked).
        let err = MigrateError::InvalidStructure("test sentinel");
        assert!(
            matches!(err, MigrateError::InvalidStructure(_)),
            "variant must match"
        );
        let msg = err.to_string();
        assert!(
            msg.contains("invalid TOML structure"),
            "error message must mention 'invalid TOML structure', got: {msg}"
        );
        assert!(
            msg.contains("test sentinel"),
            "message must include reason: {msg}"
        );
    }

    // ─── migrate_mcp_trust_levels ─────────────────────────────────────────────

    #[test]
    fn migrate_mcp_trust_levels_adds_trusted_to_entries_without_field() {
        let src = r#"
[mcp]
allowed_commands = ["npx"]

[[mcp.servers]]
id = "srv-a"
command = "npx"
args = ["-y", "some-mcp"]

[[mcp.servers]]
id = "srv-b"
command = "npx"
args = ["-y", "other-mcp"]
"#;
        let result = migrate_mcp_trust_levels(src).expect("migrate");
        assert_eq!(
            result.changed_count, 2,
            "both entries must get trust_level added"
        );
        assert!(
            result
                .sections_changed
                .contains(&"mcp.servers.trust_level".to_owned()),
            "sections_changed must report mcp.servers.trust_level"
        );
        // Both entries must now contain trust_level = "trusted"
        let occurrences = result.output.matches("trust_level = \"trusted\"").count();
        assert_eq!(
            occurrences, 2,
            "each entry must have trust_level = \"trusted\""
        );
    }

    #[test]
    fn migrate_mcp_trust_levels_does_not_overwrite_existing_field() {
        let src = r#"
[[mcp.servers]]
id = "srv-a"
command = "npx"
trust_level = "sandboxed"
tool_allowlist = ["read_file"]

[[mcp.servers]]
id = "srv-b"
command = "npx"
"#;
        let result = migrate_mcp_trust_levels(src).expect("migrate");
        // Only srv-b has no trust_level, so only 1 entry should be updated
        assert_eq!(
            result.changed_count, 1,
            "only entry without trust_level gets updated"
        );
        // srv-a's sandboxed value must not be overwritten
        assert!(
            result.output.contains("trust_level = \"sandboxed\""),
            "existing trust_level must not be overwritten"
        );
        // srv-b gets trusted
        assert!(
            result.output.contains("trust_level = \"trusted\""),
            "entry without trust_level must get trusted"
        );
    }

    #[test]
    fn migrate_mcp_trust_levels_no_mcp_section_is_noop() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_mcp_trust_levels(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_trust_levels_no_servers_is_noop() {
        let src = "[mcp]\nallowed_commands = [\"npx\"]\n";
        let result = migrate_mcp_trust_levels(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_trust_levels_all_entries_already_have_field_is_noop() {
        let src = r#"
[[mcp.servers]]
id = "srv-a"
trust_level = "trusted"

[[mcp.servers]]
id = "srv-b"
trust_level = "untrusted"
"#;
        let result = migrate_mcp_trust_levels(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
    }

    #[test]
    fn migrate_database_url_adds_comment_when_absent() {
        let src = "[memory]\nsqlite_path = \"/tmp/zeph.db\"\n";
        let result = migrate_database_url(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"memory.database_url".to_owned())
        );
        assert!(result.output.contains("# database_url = \"\""));
    }

    #[test]
    fn migrate_database_url_is_noop_when_present() {
        let src = "[memory]\nsqlite_path = \"/tmp/zeph.db\"\ndatabase_url = \"postgres://localhost/zeph\"\n";
        let result = migrate_database_url(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_database_url_creates_memory_section_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_database_url(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("# database_url = \"\""));
    }

    // ── migrate_agent_budget_hint tests (#2267) ───────────────────────────────

    #[test]
    fn migrate_agent_budget_hint_adds_comment_to_existing_agent_section() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_agent_budget_hint(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("budget_hint_enabled"));
        assert!(
            result
                .sections_changed
                .contains(&"agent.budget_hint_enabled".to_owned())
        );
    }

    #[test]
    fn migrate_agent_budget_hint_no_agent_section_is_noop() {
        let src = "[llm]\nmodel = \"gpt-4o\"\n";
        let result = migrate_agent_budget_hint(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_agent_budget_hint_already_present_is_noop() {
        let src = "[agent]\nname = \"Zeph\"\nbudget_hint_enabled = true\n";
        let result = migrate_agent_budget_hint(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_telemetry_config_empty_config_appends_comment_block() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_telemetry_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert_eq!(result.sections_changed, vec!["telemetry"]);
        assert!(
            result.output.contains("# [telemetry]"),
            "expected commented-out [telemetry] block in output"
        );
        assert!(
            result.output.contains("enabled = false"),
            "expected enabled = false in telemetry comment block"
        );
    }

    #[test]
    fn migrate_telemetry_config_existing_section_is_noop() {
        let src = "[agent]\nname = \"Zeph\"\n\n[telemetry]\nenabled = true\n";
        let result = migrate_telemetry_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_telemetry_config_existing_comment_is_noop() {
        // Idempotency: if the comment block was already added, don't append again.
        let src = "[agent]\nname = \"Zeph\"\n\n# [telemetry]\n# enabled = false\n";
        let result = migrate_telemetry_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_otel_filter tests (#2997) ─────────────────────────────────────

    #[test]
    fn migrate_otel_filter_already_present_is_noop() {
        // Real key present — must not modify.
        let src = "[telemetry]\nenabled = true\notel_filter = \"debug\"\n";
        let result = migrate_otel_filter(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_otel_filter_commented_key_is_noop() {
        // Commented-out key already present — idempotent.
        let src = "[telemetry]\nenabled = true\n# otel_filter = \"info\"\n";
        let result = migrate_otel_filter(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_otel_filter_no_telemetry_section_is_noop() {
        // [telemetry] absent — must not inject into wrong location.
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_otel_filter(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
        assert!(!result.output.contains("otel_filter"));
    }

    #[test]
    fn migrate_otel_filter_injects_within_telemetry_section() {
        let src = "[telemetry]\nenabled = true\n\n[agent]\nname = \"Zeph\"\n";
        let result = migrate_otel_filter(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert_eq!(result.sections_changed, vec!["telemetry.otel_filter"]);
        assert!(
            result.output.contains("otel_filter"),
            "otel_filter comment must appear"
        );
        // Comment must appear before [agent] — i.e., within the telemetry section.
        let otel_pos = result
            .output
            .find("otel_filter")
            .expect("otel_filter present");
        let agent_pos = result.output.find("[agent]").expect("[agent] present");
        assert!(
            otel_pos < agent_pos,
            "otel_filter comment should appear before [agent] section"
        );
    }

    #[test]
    fn sandbox_migration_adds_commented_section_when_absent() {
        let src = "[agent]\nname = \"Z\"\n";
        let result = migrate_sandbox_config(src).expect("migrate sandbox");
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("# [tools.sandbox]"));
        assert!(result.output.contains("# profile = \"workspace\""));
    }

    #[test]
    fn sandbox_migration_noop_when_section_present() {
        let src = "[tools.sandbox]\nenabled = true\n";
        let result = migrate_sandbox_config(src).expect("migrate sandbox");
        assert_eq!(result.changed_count, 0);
    }

    #[test]
    fn sandbox_migration_noop_when_dotted_key_present() {
        let src = "[tools]\nsandbox = { enabled = true }\n";
        let result = migrate_sandbox_config(src).expect("migrate sandbox");
        assert_eq!(result.changed_count, 0);
    }

    #[test]
    fn sandbox_migration_false_positive_comment_does_not_block() {
        // Comments mentioning tools.sandbox must NOT suppress insertion.
        let src = "# tools.sandbox was planned for #3070\n[agent]\nname = \"Z\"\n";
        let result = migrate_sandbox_config(src).expect("migrate sandbox");
        assert_eq!(result.changed_count, 1);
    }

    #[test]
    fn embedded_default_mentions_tools_sandbox() {
        let default_src = include_str!("../../config/default.toml");
        assert!(
            default_src.contains("tools.sandbox"),
            "embedded default.toml must include tools.sandbox for ConfigMigrator discovery"
        );
    }

    #[test]
    fn sandbox_migration_idempotent_on_own_output() {
        let base = "[agent]\nmodel = \"test\"\n";
        let first = migrate_sandbox_config(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_sandbox_config(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_agent_budget_hint_idempotent_on_commented_output() {
        let base = "[agent]\nname = \"Zeph\"\n";
        let first = migrate_agent_budget_hint(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_agent_budget_hint(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_forgetting_config_idempotent_on_commented_output() {
        let base = "[memory]\ndb_path = \"~/.zeph/memory.db\"\n";
        let first = migrate_forgetting_config(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_forgetting_config(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_microcompact_config_idempotent_on_commented_output() {
        let base = "[memory]\ndb_path = \"~/.zeph/memory.db\"\n";
        let first = migrate_microcompact_config(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_microcompact_config(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_autodream_config_idempotent_on_commented_output() {
        let base = "[memory]\ndb_path = \"~/.zeph/memory.db\"\n";
        let first = migrate_autodream_config(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_autodream_config(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_compression_predictor_strips_active_section() {
        let base = "[memory]\ndb_path = \"test\"\n[memory.compression.predictor]\nenabled = false\nmin_samples = 10\n[memory.other]\nfoo = 1\n";
        let result = migrate_compression_predictor_config(base).unwrap();
        assert!(!result.output.contains("[memory.compression.predictor]"));
        assert!(!result.output.contains("min_samples"));
        assert!(result.output.contains("[memory.other]"));
        assert_eq!(result.changed_count, 1);
    }

    #[test]
    fn migrate_compression_predictor_strips_commented_section() {
        let base = "[memory]\ndb_path = \"test\"\n# [memory.compression.predictor]\n# enabled = false\n[memory.other]\nfoo = 1\n";
        let result = migrate_compression_predictor_config(base).unwrap();
        assert!(!result.output.contains("compression.predictor"));
        assert!(result.output.contains("[memory.other]"));
    }

    #[test]
    fn migrate_compression_predictor_idempotent() {
        let base = "[memory]\ndb_path = \"test\"\n[memory.compression.predictor]\nenabled = false\n[memory.other]\nfoo = 1\n";
        let first = migrate_compression_predictor_config(base).unwrap();
        let second = migrate_compression_predictor_config(&first.output).unwrap();
        assert_eq!(second.output, first.output);
        assert_eq!(second.changed_count, 0);
    }

    #[test]
    fn migrate_compression_predictor_noop_when_absent() {
        let base = "[memory]\ndb_path = \"test\"\n";
        let result = migrate_compression_predictor_config(base).unwrap();
        assert_eq!(result.output, base);
        assert_eq!(result.changed_count, 0);
    }

    #[test]
    fn migrate_database_url_idempotent_on_commented_output() {
        let base = "[memory]\ndb_path = \"~/.zeph/memory.db\"\n";
        let first = migrate_database_url(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_database_url(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_shell_transactional_idempotent_on_commented_output() {
        let base = "[tools]\n[tools.shell]\nallow_list = []\n";
        let first = migrate_shell_transactional(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_shell_transactional(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_otel_filter_idempotent_on_commented_output() {
        let base = "[telemetry]\nenabled = true\n";
        let first = migrate_otel_filter(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_otel_filter(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn config_migrator_does_not_suppress_duplicate_key_across_sections() {
        let migrator = ConfigMigrator::new();
        let src = "[telemetry]\nenabled = true\n\n[security]\n[security.content_isolation]\n";
        let result = migrator.migrate(src).expect("migrate");
        let sec_body_start = result
            .output
            .find("[security.content_isolation]")
            .unwrap_or(0);
        let sec_body = &result.output[sec_body_start..];
        let next_header = sec_body[1..].find("\n[").map_or(sec_body.len(), |p| p + 1);
        let sec_slice = &sec_body[..next_header];
        assert!(
            sec_slice.contains("# enabled"),
            "[security.content_isolation] body must contain `# enabled` hint; got: {sec_slice:?}"
        );
    }

    #[test]
    fn config_migrator_idempotent_on_realistic_config() {
        let base = r#"
[agent]
name = "Zeph"

[memory]
db_path = "~/.zeph/memory.db"
soft_compaction_threshold = 0.6

[index]
max_chunks = 12

[tools]
[tools.shell]
allow_list = []

[telemetry]
enabled = false

[security]
[security.content_isolation]
enabled = true
"#;
        let migrator = ConfigMigrator::new();
        let first = migrator.migrate(base).expect("first migrate");
        let second = migrator.migrate(&first.output).expect("second migrate");
        assert_eq!(
            second.changed_count, 0,
            "second run of ConfigMigrator::migrate must add 0 entries, got {}",
            second.changed_count
        );
        assert_eq!(
            first.output, second.output,
            "output must be identical on second run"
        );
        for line in first.output.lines() {
            if line.starts_with('[') && !line.starts_with("[[") {
                assert!(
                    !line.contains('#'),
                    "section header must not have inline comment: {line:?}"
                );
            }
        }
    }

    #[test]
    fn migrate_claude_prompt_cache_ttl_1h_survives() {
        let src = r#"
[llm]
provider = "claude"

[llm.cloud]
model = "claude-sonnet-4-6"
prompt_cache_ttl = "1h"
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            result.output.contains("prompt_cache_ttl = \"1h\""),
            "1h TTL must be preserved in migrated output:\n{}",
            result.output
        );
    }

    #[test]
    fn migrate_claude_prompt_cache_ttl_ephemeral_suppressed() {
        let src = r#"
[llm]
provider = "claude"

[llm.cloud]
model = "claude-sonnet-4-6"
prompt_cache_ttl = "ephemeral"
"#;
        let result = migrate_llm_to_providers(src).expect("migrate");
        assert!(
            !result.output.contains("prompt_cache_ttl"),
            "ephemeral TTL must be suppressed (M2 idempotency guard):\n{}",
            result.output
        );
    }

    #[test]
    fn migrate_claude_prompt_cache_ttl_1h_idempotent() {
        let src = r#"
[[llm.providers]]
type = "claude"
model = "claude-sonnet-4-6"
prompt_cache_ttl = "1h"
"#;
        let migrator = ConfigMigrator::new();
        let first = migrator.migrate(src).expect("first migrate");
        let second = migrator.migrate(&first.output).expect("second migrate");
        assert_eq!(
            first.output, second.output,
            "migration must be idempotent when prompt_cache_ttl = \"1h\" already present"
        );
    }

    // ── migrate_session_recap_config ──────────────────────────────────────────

    #[test]
    fn migrate_session_recap_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_session_recap_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"session.recap".to_owned())
        );
        assert!(result.output.contains("# [session.recap]"));
        assert!(result.output.contains("on_resume = true"));
    }

    #[test]
    fn migrate_session_recap_idempotent_on_commented_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [session.recap]\n# on_resume = true\n";
        let result = migrate_session_recap_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_session_recap_idempotent_on_active_section() {
        let src = "[agent]\nname = \"Zeph\"\n[session.recap]\non_resume = false\n";
        let result = migrate_session_recap_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_mcp_elicitation_config ────────────────────────────────────────

    #[test]
    fn migrate_mcp_elicitation_adds_keys_when_absent() {
        let src = "[mcp]\nallowed_commands = []\n";
        let result = migrate_mcp_elicitation_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"mcp.elicitation".to_owned())
        );
        assert!(result.output.contains("# elicitation_enabled = false"));
        assert!(result.output.contains("# elicitation_timeout = 120"));
    }

    #[test]
    fn migrate_mcp_elicitation_idempotent_when_key_present() {
        let src = "[mcp]\nelicitation_enabled = true\n";
        let result = migrate_mcp_elicitation_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_elicitation_skips_when_no_mcp_section() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_mcp_elicitation_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_elicitation_skips_without_trailing_newline() {
        // Edge case: `[mcp]` at EOF with no `\n` — replacen would be a no-op.
        let src = "[mcp]";
        let result = migrate_mcp_elicitation_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_quality_config ────────────────────────────────────────────────

    #[test]
    fn migrate_quality_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_quality_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(result.sections_changed.contains(&"quality".to_owned()));
        assert!(result.output.contains("# [quality]"));
        assert!(result.output.contains("self_check = false"));
        assert!(result.output.contains("trigger = \"has_retrieval\""));
    }

    #[test]
    fn migrate_quality_idempotent_on_commented_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [quality]\n# self_check = false\n";
        let result = migrate_quality_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_quality_idempotent_on_active_section() {
        let src = "[agent]\nname = \"Zeph\"\n[quality]\nself_check = true\n";
        let result = migrate_quality_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_acp_subagents_config ─────────────────────────────────────────

    #[test]
    fn migrate_acp_subagents_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_acp_subagents_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"acp.subagents".to_owned())
        );
        assert!(result.output.contains("# [acp.subagents]"));
        assert!(result.output.contains("enabled = false"));
    }

    #[test]
    fn migrate_acp_subagents_idempotent_on_existing_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [acp.subagents]\n# enabled = false\n";
        let result = migrate_acp_subagents_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_hooks_permission_denied_config ────────────────────────────────

    #[test]
    fn migrate_hooks_permission_denied_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_hooks_permission_denied_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"hooks.permission_denied".to_owned())
        );
        assert!(result.output.contains("# [[hooks.permission_denied]]"));
        assert!(result.output.contains("ZEPH_TOOL"));
    }

    #[test]
    fn migrate_hooks_permission_denied_idempotent_on_existing_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [[hooks.permission_denied]]\n# type = \"command\"\n";
        let result = migrate_hooks_permission_denied_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_memory_graph_config ───────────────────────────────────────────

    #[test]
    fn migrate_memory_graph_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_memory_graph_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"memory.graph.retrieval".to_owned())
        );
        assert!(result.output.contains("retrieval_strategy"));
        assert!(result.output.contains("# [memory.graph.beam_search]"));
    }

    #[test]
    fn migrate_memory_graph_idempotent_on_existing_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [memory.graph.beam_search]\n# beam_width = 10\n";
        let result = migrate_memory_graph_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_scheduler_daemon_config ──────────────────────────────────────

    #[test]
    fn migrate_scheduler_daemon_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_scheduler_daemon_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"scheduler.daemon".to_owned())
        );
        assert!(result.output.contains("# [scheduler.daemon]"));
        assert!(result.output.contains("pid_file"));
        assert!(result.output.contains("tick_secs = 60"));
        assert!(result.output.contains("shutdown_grace_secs = 30"));
        assert!(result.output.contains("catch_up = true"));
    }

    #[test]
    fn migrate_scheduler_daemon_idempotent_on_existing_block() {
        let src = "[agent]\nname = \"Zeph\"\n# [scheduler.daemon]\n# tick_secs = 60\n";
        let result = migrate_scheduler_daemon_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── migrate_memory_retrieval_config ──────────────────────────────────────

    #[test]
    fn migrate_memory_retrieval_adds_block_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_memory_retrieval_config(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"memory.retrieval".to_owned())
        );
        assert!(result.output.contains("# [memory.retrieval]"));
        assert!(result.output.contains("depth = 0"));
        assert!(result.output.contains("context_format"));
    }

    #[test]
    fn migrate_memory_retrieval_idempotent_on_active_section() {
        let src = "[memory.retrieval]\ndepth = 40\n";
        let result = migrate_memory_retrieval_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_memory_retrieval_idempotent_on_commented_section() {
        let src = "[agent]\nname = \"Zeph\"\n# [memory.retrieval]\n# depth = 0\n";
        let result = migrate_memory_retrieval_config(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── acp PR4 migration ─────────────────────────────────────────────────────

    #[test]
    fn migrate_adds_pr4_acp_keys_commented() {
        let migrator = ConfigMigrator::new();
        let input = include_str!("../../tests/fixtures/acp_pr4_v0_19.toml");
        let out = migrator.migrate(input).expect("migrate");
        assert!(
            out.output.contains("# additional_directories = []"),
            "expected commented additional_directories; got:\n{}",
            out.output
        );
        assert!(
            out.output.contains("# auth_methods = [\"agent\"]"),
            "expected commented auth_methods; got:\n{}",
            out.output
        );
        assert!(
            out.output.contains("# message_ids_enabled = true"),
            "expected commented message_ids_enabled; got:\n{}",
            out.output
        );
    }

    // ── migrate_memory_reasoning_config ──────────────────────────────────────

    #[test]
    fn migrate_memory_reasoning_adds_block_when_absent() {
        let input = "[agent]\nmodel = \"gpt-4o\"\n";
        let result = migrate_memory_reasoning_config(input).unwrap();
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"memory.reasoning".to_owned())
        );
        assert!(result.output.contains("# [memory.reasoning]"));
        assert!(result.output.contains("extraction_timeout_secs = 30"));
        assert!(result.output.contains("max_message_chars = 2000"));
    }

    #[test]
    fn migrate_memory_reasoning_idempotent_on_existing_block() {
        let input = "[agent]\nmodel = \"gpt-4o\"\n# [memory.reasoning]\n# enabled = false\n";
        let result = migrate_memory_reasoning_config(input).unwrap();
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, input);
    }

    // ── migrate_hooks_turn_complete_config ────────────────────────────────────

    #[test]
    fn migrate_hooks_turn_complete_adds_block_when_absent() {
        let input = "[agent]\nmodel = \"gpt-4o\"\n";
        let result = migrate_hooks_turn_complete_config(input).unwrap();
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"hooks.turn_complete".to_owned())
        );
        assert!(result.output.contains("# [[hooks.turn_complete]]"));
        assert!(result.output.contains("ZEPH_TURN_PREVIEW"));
        assert!(result.output.contains("timeout_secs = 3"));
    }

    #[test]
    fn migrate_hooks_turn_complete_idempotent_on_existing_block() {
        let input =
            "[agent]\nmodel = \"gpt-4o\"\n# [[hooks.turn_complete]]\n# command = \"echo done\"\n";
        let result = migrate_hooks_turn_complete_config(input).unwrap();
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, input);
    }

    // ── migrate_focus_auto_consolidate_min_window ──────────────────────────────

    /// S5: the comment must land inside [agent.focus], not after a subsequent section.
    #[test]
    fn migrate_focus_auto_consolidate_injects_inside_section() {
        let input = "[agent.focus]\nenabled = true\n\n[other]\nfoo = 1\n";
        let result = migrate_focus_auto_consolidate_min_window(input).unwrap();
        assert_eq!(result.changed_count, 1);
        let comment_pos = result
            .output
            .find("auto_consolidate_min_window")
            .expect("comment must be present");
        let other_pos = result
            .output
            .find("[other]")
            .expect("[other] must be present");
        assert!(
            comment_pos < other_pos,
            "auto_consolidate_min_window comment must appear before [other] section"
        );
    }

    #[test]
    fn migrate_focus_auto_consolidate_idempotent() {
        let input = "[agent.focus]\nenabled = true\nauto_consolidate_min_window = 6\n";
        let result = migrate_focus_auto_consolidate_min_window(input).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, input);
    }

    #[test]
    fn migrate_focus_auto_consolidate_noop_when_section_absent() {
        let input = "[agent]\nname = \"zeph\"\n";
        let result = migrate_focus_auto_consolidate_min_window(input).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, input);
    }

    #[test]
    fn migrate_focus_auto_consolidate_noop_when_only_commented_section() {
        let input = "[agent]\n# [agent.focus]\n# enabled = false\n";
        let result = migrate_focus_auto_consolidate_min_window(input).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, input);
    }

    // ── Migration registry ────────────────────────────────────────────────────

    #[test]
    fn registry_has_fifty_entries() {
        assert_eq!(MIGRATIONS.len(), 50);
    }

    #[test]
    fn registry_names_are_unique_and_non_empty() {
        let names: Vec<&str> = MIGRATIONS.iter().map(|m| m.name()).collect();
        for name in &names {
            assert!(!name.is_empty(), "migration name must not be empty");
        }
        let mut deduped = names.clone();
        deduped.sort_unstable();
        deduped.dedup();
        assert_eq!(deduped.len(), names.len(), "migration names must be unique");
    }

    #[test]
    fn registry_is_idempotent_on_empty_input() {
        // Migrations that append comment blocks cannot be idempotent by design:
        // comment text is not parsed as TOML keys, so presence checks always fail.
        const COMMENT_ONLY: &[&str] = &["migrate_magic_docs_config"];

        let mut toml = String::new();
        for m in MIGRATIONS.iter() {
            let result = m.apply(&toml).expect("registry migration must not fail");
            toml = result.output;
        }
        for m in MIGRATIONS.iter() {
            if COMMENT_ONLY.contains(&m.name()) {
                continue;
            }
            let result = m
                .apply(&toml)
                .expect("registry migration must not fail on second pass");
            assert_eq!(result.changed_count, 0, "{} is not idempotent", m.name());
        }
    }

    #[test]
    fn registry_preserves_order_matches_dispatch() {
        // Names must follow the documented step order (steps 1–49).
        let expected = [
            "migrate_stt_to_provider",
            "migrate_planner_model_to_provider",
            "migrate_mcp_trust_levels",
            "migrate_agent_retry_to_tools_retry",
            "migrate_database_url",
            "migrate_shell_transactional",
            "migrate_agent_budget_hint",
            "migrate_forgetting_config",
            "migrate_compression_predictor_config",
            "migrate_microcompact_config",
            "migrate_autodream_config",
            "migrate_magic_docs_config",
            "migrate_telemetry_config",
            "migrate_supervisor_config",
            "migrate_otel_filter",
            "migrate_egress_config",
            "migrate_vigil_config",
            "migrate_sandbox_config",
            "migrate_sandbox_egress_filter",
            "migrate_orchestration_persistence",
            "migrate_session_recap_config",
            "migrate_mcp_elicitation_config",
            "migrate_quality_config",
            "migrate_acp_subagents_config",
            "migrate_hooks_permission_denied_config",
            "migrate_memory_graph_config",
            "migrate_scheduler_daemon_config",
            "migrate_memory_retrieval_config",
            "migrate_memory_reasoning_config",
            "migrate_memory_reasoning_judge_config",
            "migrate_memory_hebbian_config",
            "migrate_memory_hebbian_consolidation_config",
            "migrate_memory_hebbian_spread_config",
            "migrate_hooks_turn_complete_config",
            "migrate_focus_auto_consolidate_min_window",
            "migrate_session_provider_persistence",
            "migrate_memory_retrieval_query_bias",
            "migrate_memory_persona_config",
            "migrate_qdrant_api_key",
            "migrate_mcp_max_connect_attempts",
            "migrate_goals_config",
            "migrate_tools_compression_config",
            "migrate_orchestrator_provider",
            "migrate_provider_max_concurrent",
            "migrate_gonkagate_to_gonka",
            "migrate_cocoon_provider_notice",
            "migrate_trace_metadata",
            "migrate_five_signal_config",
            "migrate_embed_provider_rename",
            "migrate_mcp_retry_and_tool_timeout",
        ];
        let actual: Vec<&str> = MIGRATIONS.iter().map(|m| m.name()).collect();
        assert_eq!(actual, expected);
    }

    // ── migrate_trace_metadata tests (#4160) ─────────────────────────────────

    #[test]
    fn migrate_trace_metadata_noop_when_already_present() {
        let src = "[telemetry]\nenabled = true\n\n[telemetry.trace_metadata]\n\"env\" = \"prod\"\n";
        let result = migrate_trace_metadata(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_trace_metadata_noop_when_no_telemetry_section() {
        let src = "[agent]\nmax_turns = 10\n";
        let result = migrate_trace_metadata(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_trace_metadata_injects_comment_when_telemetry_present() {
        let src = "[telemetry]\nenabled = true\nservice_name = \"zeph\"\n";
        let result = migrate_trace_metadata(src).unwrap();
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("trace_metadata"));
        assert!(
            result
                .sections_changed
                .contains(&"telemetry.trace_metadata".to_owned())
        );
        // Idempotent: running again is a no-op.
        let result2 = migrate_trace_metadata(&result.output).unwrap();
        assert_eq!(result2.changed_count, 0);
    }

    // ── migrate_qdrant_api_key tests (#3543) ─────────────────────────────────

    #[test]
    fn migrate_qdrant_api_key_adds_comment_when_absent() {
        let src = "[memory]\nqdrant_url = \"http://localhost:6334\"\n";
        let result = migrate_qdrant_api_key(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result
                .sections_changed
                .contains(&"memory.qdrant_api_key".to_owned())
        );
        assert!(result.output.contains("# qdrant_api_key = \"\""));
    }

    #[test]
    fn migrate_qdrant_api_key_is_noop_when_present() {
        let src =
            "[memory]\nqdrant_url = \"https://xyz.cloud.qdrant.io\"\nqdrant_api_key = \"secret\"\n";
        let result = migrate_qdrant_api_key(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert!(result.sections_changed.is_empty());
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_qdrant_api_key_creates_memory_section_when_absent() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_qdrant_api_key(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("# qdrant_api_key = \"\""));
    }

    #[test]
    fn migrate_qdrant_api_key_idempotent_on_commented_output() {
        let base = "[memory]\nqdrant_url = \"http://localhost:6334\"\n";
        let first = migrate_qdrant_api_key(base).unwrap();
        assert_eq!(first.changed_count, 1);
        let second = migrate_qdrant_api_key(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must not double-append");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_mcp_max_connect_attempts_adds_comment_when_absent() {
        let src = "[mcp]\nallowed_commands = []\n";
        let result = migrate_mcp_max_connect_attempts(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result.output.contains("max_connect_attempts"),
            "output must mention max_connect_attempts"
        );
    }

    #[test]
    fn migrate_mcp_max_connect_attempts_idempotent_when_present() {
        let src = "[mcp]\n# max_connect_attempts = 3\nallowed_commands = []\n";
        let result = migrate_mcp_max_connect_attempts(src).expect("migrate");
        assert_eq!(
            result.changed_count, 0,
            "must not modify already-present key"
        );
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_max_connect_attempts_skips_when_no_mcp_section() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_mcp_max_connect_attempts(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── Step 50 — mcp startup_retry_backoff_ms and tool_timeout_secs ──────────────────────────────

    #[test]
    fn migrate_mcp_retry_and_tool_timeout_adds_both_keys_when_absent() {
        let src = "[mcp]\nallowed_commands = []\n";
        let result = migrate_mcp_retry_and_tool_timeout(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result.output.contains("startup_retry_backoff_ms"),
            "output must include startup_retry_backoff_ms"
        );
        assert!(
            result.output.contains("tool_timeout_secs"),
            "output must include tool_timeout_secs"
        );
    }

    #[test]
    fn migrate_mcp_retry_and_tool_timeout_idempotent_when_both_present() {
        let src = "[mcp]\n# startup_retry_backoff_ms = 1000\n# tool_timeout_secs = 60\n";
        let result = migrate_mcp_retry_and_tool_timeout(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_mcp_retry_and_tool_timeout_skips_when_no_mcp_section() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_mcp_retry_and_tool_timeout(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── Step 43 — orchestrator_provider ──────────────────────────────────────────────────────────

    #[test]
    fn step43_adds_orchestrator_provider_comment_when_absent() {
        let src = "[orchestration]\nenabled = true\n";
        let result = migrate_orchestration_orchestrator_provider(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result.output.contains("orchestrator_provider"),
            "migration must inject orchestrator_provider hint"
        );
    }

    #[test]
    fn step43_noop_when_orchestrator_provider_already_present() {
        let src = "[orchestration]\nenabled = true\norchestrator_provider = \"\"\n";
        let result = migrate_orchestration_orchestrator_provider(src).expect("migrate");
        assert_eq!(
            result.changed_count, 0,
            "must not modify already-present key"
        );
        assert_eq!(result.output, src);
    }

    // ── Step 44 — max_concurrent per-provider ────────────────────────────────────────────────────

    #[test]
    fn step44_adds_max_concurrent_comment_when_providers_present() {
        let src = "[[llm.providers]]\nname = \"quality\"\ntype = \"openai\"\n";
        let result = migrate_provider_max_concurrent(src).expect("migrate");
        assert_eq!(result.changed_count, 1);
        assert!(
            result.output.contains("max_concurrent"),
            "migration must inject max_concurrent hint"
        );
    }

    #[test]
    fn step44_noop_when_max_concurrent_already_present() {
        let src = "[[llm.providers]]\nname = \"quality\"\nmax_concurrent = 4\n";
        let result = migrate_provider_max_concurrent(src).expect("migrate");
        assert_eq!(
            result.changed_count, 0,
            "must not modify already-present key"
        );
        assert_eq!(result.output, src);
    }

    #[test]
    fn step44_noop_when_no_providers_section() {
        let src = "[agent]\nname = \"Zeph\"\n";
        let result = migrate_provider_max_concurrent(src).expect("migrate");
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    // ── Step 45 — migrate_gonkagate_to_gonka ─────────────────────────────────

    #[test]
    fn step45_adds_advisory_comment_when_gonkagate_present() {
        let src = "[[llm.providers]]\ntype = \"compatible\"\nname = \"gonkagate\"\n";
        let result = migrate_gonkagate_to_gonka(src);
        assert!(result.changed_count > 0, "must detect gonkagate entry");
        assert!(
            result.output.contains("[migration] GonkaGate detected"),
            "advisory comment must be added"
        );
        // Comment must appear before the [[llm.providers]] table header, not inside it.
        let comment_pos = result
            .output
            .find("[migration] GonkaGate detected")
            .unwrap();
        let header_pos = result.output.find("[[llm.providers]]").unwrap();
        assert!(
            comment_pos < header_pos,
            "advisory comment must precede the [[llm.providers]] header"
        );
    }

    #[test]
    fn step45_noop_when_no_gonkagate() {
        let src = "[[llm.providers]]\ntype = \"openai\"\nname = \"quality\"\n";
        let result = migrate_gonkagate_to_gonka(src);
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn step45_does_not_double_insert_comment() {
        let src = "[[llm.providers]]\ntype = \"compatible\"\nname = \"gonkagate\"\n";
        let first = migrate_gonkagate_to_gonka(src);
        let second = migrate_gonkagate_to_gonka(&first.output);
        // Second run must not add another comment line.
        assert_eq!(second.changed_count, 0, "idempotent on second run");
    }

    // ── Step 46 — Cocoon provider notice ──────────────────────────────────────

    #[test]
    fn migrate_cocoon_noop_empty_config() {
        let src = "";
        let result = migrate_cocoon_provider_notice(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_cocoon_noop_existing_config() {
        let src = "[agent]\nname = \"zeph\"\n\n[[llm.providers]]\ntype = \"ollama\"\n";
        let result = migrate_cocoon_provider_notice(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_cocoon_idempotent() {
        let src = "[[llm.providers]]\ntype = \"cocoon\"\nname = \"tee\"\n";
        let first = migrate_cocoon_provider_notice(src).unwrap();
        let second = migrate_cocoon_provider_notice(&first.output).unwrap();
        assert_eq!(second.output, first.output);
        assert_eq!(second.changed_count, 0);
    }

    // ── migrate_five_signal_config tests (#4374) ─────────────────────────────

    #[test]
    fn migrate_five_signal_config_noop_when_already_present() {
        let src = "[memory]\nenabled = true\n\n[memory.five_signal]\nenabled = false\n";
        let result = migrate_five_signal_config(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_five_signal_config_noop_when_no_memory_section() {
        let src = "[agent]\nmax_turns = 10\n";
        let result = migrate_five_signal_config(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_five_signal_config_injects_comment_when_memory_present() {
        let src = "[memory]\nenabled = true\n";
        let result = migrate_five_signal_config(src).unwrap();
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("five_signal"));
        assert!(
            result
                .sections_changed
                .contains(&"memory.five_signal".to_owned())
        );
    }

    #[test]
    fn migrate_five_signal_config_idempotent_on_commented_output() {
        let base = "[memory]\nenabled = true\n";
        let first = migrate_five_signal_config(base).unwrap();
        let second = migrate_five_signal_config(&first.output).unwrap();
        assert_eq!(second.output, first.output);
        assert_eq!(second.changed_count, 0);
    }

    // ── migrate_embed_provider_rename tests (#4480) ───────────────────────────

    #[test]
    fn migrate_embed_provider_rename_renames_all_four_keys() {
        let src = "\
[memory.semantic]\n\
embed_provider = \"ollama-embed\"\n\
\n\
[index]\n\
embed_provider = \"ollama-embed\"\n\
\n\
[llm.coe]\n\
embed_provider = \"\"\n\
\n\
[learning]\n\
trace_extraction_embed_provider = \"embed-fast\"\n";
        let result = migrate_embed_provider_rename(src).unwrap();
        assert_eq!(result.changed_count, 4);
        assert!(
            result
                .output
                .contains("embedding_provider = \"ollama-embed\"")
        );
        assert!(
            result
                .output
                .contains("trace_extraction_embedding_provider = \"embed-fast\"")
        );
        assert!(!result.output.contains("trace_extraction_embed_provider ="));
        assert!(!result.output.contains("\nembed_provider ="));
    }

    #[test]
    fn migrate_embed_provider_rename_idempotent_on_own_output() {
        let src = "\
[memory.semantic]\n\
embed_provider = \"ollama-embed\"\n\
\n\
[learning]\n\
trace_extraction_embed_provider = \"embed-fast\"\n";
        let first = migrate_embed_provider_rename(src).unwrap();
        assert_eq!(first.changed_count, 2);
        let second = migrate_embed_provider_rename(&first.output).unwrap();
        assert_eq!(second.changed_count, 0, "second run must be a no-op");
        assert_eq!(second.output, first.output);
    }

    #[test]
    fn migrate_embed_provider_rename_noop_when_no_old_keys() {
        let src = "\
[memory.semantic]\n\
embedding_provider = \"ollama-embed\"\n\
\n\
[learning]\n\
trace_extraction_embedding_provider = \"embed-fast\"\n";
        let result = migrate_embed_provider_rename(src).unwrap();
        assert_eq!(result.changed_count, 0);
        assert_eq!(result.output, src);
    }

    #[test]
    fn migrate_embed_provider_rename_preserves_commented_lines() {
        // Lines starting with `#` must not be renamed — `trimmed.starts_with("embed_provider")`
        // is false when the line starts with `#`.
        let src = "# embed_provider = \"old-key\"  # this is a comment\n\
trace_extraction_embed_provider = \"live\"\n";
        let result = migrate_embed_provider_rename(src).unwrap();
        // Only the uncommented key is renamed.
        assert_eq!(result.changed_count, 1);
        assert!(result.output.contains("# embed_provider = \"old-key\""));
        assert!(
            result
                .output
                .contains("trace_extraction_embedding_provider = \"live\"")
        );
    }
}