khive_runtime/

presentation.rs

//! Verb response presentation modes and transformation.
//!
//! Transforms canonical handler output into caller-appropriate form after dispatch
//! and before wire serialization. `Agent` mode abbreviates UUIDs and drops
//! empty fields; `Verbose` and `Human` pass through canonical JSON unchanged.
//!
//! This module also contains the `OutputFormat` axis (ADR-078) which governs how
//! the resulting `serde_json::Value` is serialized or rendered to an output string.
//! `PresentationMode` and `OutputFormat` compose independently.

use std::{cmp::Ordering, collections::HashSet};

use khive_types::VerbPresentationPolicy;
use serde::{Deserialize, Serialize};
use serde_json::{Map, Value};

/// Exact note-body locations selected by the request boundary for
/// `get/list(parse_content=true)`. No policy marker is inferred from user JSON.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum NoteContentScope {
    #[default]
    None,
    Record,
    Items,
    Notes,
}

impl NoteContentScope {
    /// Keep note bodies outside a metadata-only transform, including nulls,
    /// empty containers/strings, and fields that resemble IDs or timestamps.
    /// The transform must preserve record order and the get/list envelope.
    pub fn protect(self, mut value: Value, transform: impl FnOnce(Value) -> Value) -> Value {
        if self == Self::None {
            return transform(value);
        }
        fn take_content(record: &mut Value) -> Option<Value> {
            record.as_object_mut()?.remove("content")
        }
        fn restore_content(record: &mut Value, content: Option<Value>) {
            if let (Some(record), Some(content)) = (record.as_object_mut(), content) {
                record.insert("content".to_string(), content);
            }
        }
        if self == Self::Record {
            let content = take_content(&mut value);
            let mut value = transform(value);
            restore_content(&mut value, content);
            return value;
        }
        let key = if self == Self::Items {
            "items"
        } else {
            "notes"
        };
        let contents: Vec<_> = value
            .get_mut(key)
            .and_then(Value::as_array_mut)
            .into_iter()
            .flatten()
            .map(take_content)
            .collect();
        let mut value = transform(value);
        if let Some(records) = value.get_mut(key).and_then(Value::as_array_mut) {
            for (record, content) in records.iter_mut().zip(contents) {
                restore_content(record, content);
            }
        }
        value
    }

    fn stringify_table_content(self, value: &mut Value) {
        fn stringify(record: &mut Value) {
            if let Some(content) = record.get_mut("content") {
                if content.is_object() || content.is_array() {
                    *content = Value::String(content.to_string());
                }
            }
        }
        match self {
            Self::None => {}
            Self::Record => stringify(value),
            Self::Items | Self::Notes => {
                let key = if self == Self::Items {
                    "items"
                } else {
                    "notes"
                };
                if let Some(records) = value.get_mut(key).and_then(Value::as_array_mut) {
                    records.iter_mut().for_each(stringify);
                }
            }
        }
    }
}

// ── OutputFormat ─────────────────────────────────────────────────────────────

/// Output serialization format for verb results (ADR-078).
///
/// Orthogonal to [`PresentationMode`]: `PresentationMode` controls field-level
/// transforms (UUID shortening, exact UTC timestamps, empty-field dropping);
/// `OutputFormat` controls how the resulting `serde_json::Value` is serialized
/// or rendered to the wire string.
///
/// Default is [`OutputFormat::Json`] on every surface: compact and
/// machine-walkable. Verbose JSON is lossless; Agent JSON additionally elides
/// `namespace="local"` and duplicate `properties` entries (ADR-078 Amendment
/// 3, Machine scope) but keeps `full_id` — it is the caller's chaining
/// handle, not a redundant field.
///
/// Note: `Yaml` is a clean follow-up — implemented as a 3-variant enum
/// (`Json`, `Auto`, `Table`) per ADR-078 §"yaml" which permits omission when
/// the in-tree emitter would balloon.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
#[serde(rename_all = "snake_case")]
pub enum OutputFormat {
    /// Compact JSON (`serde_json::to_string`). Default; lossless in Verbose
    /// presentation, Machine-scope redundancy-reduced in Agent presentation
    /// (`full_id` retained — see [`RedundancyScope`]).
    #[default]
    Json,
    /// Shape-aware: markdown table for homogeneous record arrays (with
    /// envelope siblings preserved as trailing `key: value` lines),
    /// compact-JSON fallback for every other shape.
    Auto,
    /// Force the markdown-table renderer regardless of detected shape.
    /// Ordinary results share Auto's dispatch. Opt-in parsed note bodies are
    /// stringified for table display; Auto preserves their JSON values.
    Table,
}

/// Cell truncation limit for markdown-table rendering (ADR-078 §3a).
const CELL_TRUNCATE: usize = 120;

/// Scalar payload fields hoisted from `properties` to the top level in the
/// auto/table pre-pass, when no top-level sibling of that name exists.
/// View-only (never applied to `json`): without the hoist, a table row for a
/// scheduled event cannot say when it fires or whether it is pending —
/// those fields exist only inside the nested `properties` bag.
const PROPERTY_HOIST_FIELDS: &[&str] = &["trigger_at", "due", "status"];

// ── Public render entry point ────────────────────────────────────────────────

/// Render a successful verb result value to a wire string using the given format.
///
/// Called at the single serialization seam (ADR-078 §9) AFTER all `$prev` chain
/// resolution and AFTER the [`PresentationMode`] transform.
///
/// Error envelopes (`ok=false`) are never passed here — the caller must handle
/// them as compact JSON directly (ADR-078 §8.2).
///
/// Agent presentation applies the redundancy-reduction pre-pass (§7) for every
/// format, including JSON — at Machine scope for `json` (keeps `full_id`) and
/// View scope for `auto`/`table` (drops it too, ADR-078 Amendment 3). Auto/table
/// also apply View scope for Human presentation; Verbose remains canonical and
/// unreduced. The prepared value is then encoded as compact JSON or dispatched
/// to the shape-aware renderer. Verbose also disables cell truncation in the
/// table renderer (§3a).
pub fn render_format(value: Value, format: OutputFormat, presentation: PresentationMode) -> String {
    render_format_with_note_content(value, format, presentation, NoteContentScope::None)
}

/// Render an opt-in parsed-note response without treating its body as metadata
/// or a top-level record table. Auto preserves parsed values; Table stringifies
/// non-scalar content for display only.
pub fn render_format_with_note_content(
    value: Value,
    format: OutputFormat,
    presentation: PresentationMode,
    content_scope: NoteContentScope,
) -> String {
    let value = prepare_format_value_with_note_content(value, format, presentation, content_scope);
    match format {
        OutputFormat::Json => serde_json::to_string(&value).unwrap_or_else(|_| "null".to_string()),
        OutputFormat::Auto if content_scope != NoteContentScope::None => {
            serde_json::to_string(&value).unwrap_or_else(|_| "null".to_string())
        }
        OutputFormat::Auto | OutputFormat::Table => {
            render_auto(value, presentation != PresentationMode::Verbose)
        }
    }
}

/// Prepare a successful result for its requested format at the wire boundary.
///
/// JSON remains a JSON value in compounded response envelopes, so the MCP seam
/// uses this helper directly instead of round-tripping through a serialized
/// string. Keeping the policy here prevents the single-value and compounded
/// paths from drifting.
pub fn prepare_format_value(
    value: Value,
    format: OutputFormat,
    presentation: PresentationMode,
) -> Value {
    let scope = match format {
        OutputFormat::Json if presentation == PresentationMode::Agent => {
            Some(RedundancyScope::Machine)
        }
        OutputFormat::Json => None,
        OutputFormat::Auto | OutputFormat::Table if presentation != PresentationMode::Verbose => {
            Some(RedundancyScope::View)
        }
        OutputFormat::Auto | OutputFormat::Table => None,
    };
    match scope {
        Some(scope) => apply_redundancy_drop(value, scope),
        None => value,
    }
}

/// Apply format reductions to record metadata while preserving parsed bodies.
pub fn prepare_format_value_with_note_content(
    value: Value,
    format: OutputFormat,
    presentation: PresentationMode,
    content_scope: NoteContentScope,
) -> Value {
    let mut value = content_scope.protect(value, |value| {
        prepare_format_value(value, format, presentation)
    });
    if format == OutputFormat::Table {
        content_scope.stringify_table_content(&mut value);
    }
    value
}

// ── Redundancy-reduction pre-pass (ADR-078 §7, Amendment 3) ────────────────

/// Which redundancy-reduction rules apply (ADR-078 §7, Amendment 3).
///
/// `View` is the rendered-view scope (`auto`/`table`): the caller has opted
/// into a display form that is never chained on programmatically, so
/// `full_id` — the caller's stable chaining handle — is safe to drop along
/// with the other reductions.
///
/// `Machine` is the machine-contract scope (Agent `json`): this is the
/// default MCP response shape, the one a caller chains `$prev` and strict
/// verb parameters (`memory.feedback(target_id=...)`, `gtd.assign
/// (context_entity_id=...)`, etc.) from. It applies the `namespace` elision
/// and the `properties` dedup, but never drops `full_id`, and the
/// `properties` dedup itself exempts `full_id`/`ROUND_TRIP_FULL_UUID_FIELDS`
/// keys — a caller reading a strict identifier out of `properties` must see
/// the same canonical value there as at the top level. Dropping any of
/// those would return a value the strict verbs that consume it reject.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RedundancyScope {
    View,
    Machine,
}

/// Apply the redundancy-reduction pre-pass (ADR-078 §7, Amendment 3) to a
/// value at the given [`RedundancyScope`].
///
/// Applies at most ONE pass over the value. This function is the canonical
/// entry for the pre-pass; the per-record logic lives in `drop_record`.
///
/// Applied for Agent presentation in every format (`Machine` scope for
/// `json`, `View` scope for non-Verbose `auto`/`table`). Callers are
/// responsible for checking those conditions; this function applies
/// unconditionally.
pub fn apply_redundancy_drop(value: Value, scope: RedundancyScope) -> Value {
    match value {
        Value::Object(_) => drop_record(value, scope),
        Value::Array(arr) => Value::Array(
            arr.into_iter()
                .map(|v| {
                    if v.is_object() {
                        drop_record(v, scope)
                    } else {
                        v
                    }
                })
                .collect(),
        ),
        other => other,
    }
}

/// Apply per-record redundancy rules (§7.1, §7.2, §7.3) to a single record object.
fn drop_record(value: Value, scope: RedundancyScope) -> Value {
    let Value::Object(mut map) = value else {
        return value;
    };

    // `full_id` is a chaining handle. Dropping it is safe only in the View
    // scope (a rendered auto/table view the caller opted into); the Machine
    // scope (Agent JSON, the default machine contract) must keep it.
    if scope == RedundancyScope::View {
        map.remove("full_id");
    }

    // `"local"` is the common case, so only surface `namespace` when it isn't.
    if map.get("namespace").and_then(Value::as_str) == Some("local") {
        map.remove("namespace");
    }

    // Properties dedup: drop key-value pairs from `properties` that
    // duplicate an identical top-level sibling. The scalar hoist for table
    // columns lives in `hoist_table_scalars`, applied only on the table
    // path: reshaping the compact-JSON fallback would move fields with no
    // column to gain.
    //
    // Machine scope exempts `full_id`/`ROUND_TRIP_FULL_UUID_FIELDS`: a caller
    // that reads the strict identifier out of `properties` (rather than the
    // top-level convenience mirror) must keep getting the same canonical
    // value there too. View scope is unaffected — those callers already
    // opted into a display form, not the strict round-trip contract.
    let props_val = map.remove("properties");
    if let Some(Value::Object(props)) = props_val {
        let mut new_props = Map::new();
        for (k, v) in props {
            let strict_round_trip = scope == RedundancyScope::Machine
                && (k == "full_id" || ROUND_TRIP_FULL_UUID_FIELDS.contains(&k.as_str()));
            if !strict_round_trip && map.get(&k) == Some(&v) {
                continue;
            }
            new_props.insert(k, v);
        }
        if !new_props.is_empty() {
            map.insert("properties".to_string(), Value::Object(new_props));
        }
    } else if let Some(other) = props_val {
        map.insert("properties".to_string(), other);
    }

    // A stream entry's record is opaque caller JSON, including arrays of
    // objects whose fields happen to look like metadata.
    let stream_entry = is_stream_entry(&map);
    // Recurse into array values so nested record arrays are also reduced.
    let out: Map<String, Value> = map
        .into_iter()
        .map(|(k, v)| {
            if stream_entry && k == "record" {
                return (k, v);
            }
            let v = match v {
                Value::Array(arr) => Value::Array(
                    arr.into_iter()
                        .map(|item| {
                            if item.is_object() {
                                drop_record(item, scope)
                            } else {
                                item
                            }
                        })
                        .collect(),
                ),
                other => other,
            };
            (k, v)
        })
        .collect();
    Value::Object(out)
}

// ── Shape-aware rendering (`auto`) ──────────────────────────────────────────

/// A record array located inside a value: the records, their ordered column
/// keys, and — when the array sat under an object key — that key's name, so
/// the caller can enumerate the remaining (sibling) keys.
struct RecordArray {
    key: Option<String>,
    records: Vec<Value>,
    columns: Vec<String>,
}

/// Render a value using shape-aware dispatch (ADR-078 §3, as amended).
///
/// Shape (a): homogeneous record array → markdown table, with any envelope
/// siblings preserved as trailing `key: value` lines.
/// Every other shape → compact JSON, lossless by construction. The former
/// kv-block renderer for single records is removed: its truncation destroyed
/// single-record payloads (e.g. a compose briefing's `markdown` field).
fn render_auto(value: Value, truncate: bool) -> String {
    match locate_record_array(&value) {
        Some(found) => render_table_with_siblings(&value, &found, truncate),
        None => serde_json::to_string(&value).unwrap_or_else(|_| "null".to_string()),
    }
}

/// Find the first homogeneous record array in `value`.
///
/// Checks:
/// 1. `value` itself is an array of 2+ objects.
/// 2. `value` is an object with a key whose value is an array of 2+ objects.
fn locate_record_array(value: &Value) -> Option<RecordArray> {
    let build = |key: Option<String>, arr: &[Value]| {
        let records: Vec<Value> = arr.iter().cloned().map(hoist_table_scalars).collect();
        let columns = collect_keys(&records);
        RecordArray {
            key,
            records,
            columns,
        }
    };
    match value {
        Value::Array(arr) if is_record_array(arr) => Some(build(None, arr)),
        Value::Object(map) => map.iter().find_map(|(k, v)| match v {
            Value::Array(arr) if is_record_array(arr) => Some(build(Some(k.clone()), arr)),
            _ => None,
        }),
        _ => None,
    }
}

/// Hoist `PROPERTY_HOIST_FIELDS` scalars out of a record's `properties` bag
/// to the top level (never overwriting a top-level sibling), so the table
/// renderer can surface them as columns — a scheduled event's
/// `trigger_at`/`status` live only inside `properties`, and a nested cell
/// renders as `{…}`. Table path only (ADR-078 Amendment 2): the compact-JSON
/// fallback keeps its shape.
fn hoist_table_scalars(record: Value) -> Value {
    let Value::Object(mut map) = record else {
        return record;
    };
    let mut props = match map.remove("properties") {
        Some(Value::Object(props)) => props,
        Some(other) => {
            // Non-object `properties` is not a bag to hoist from — restore it.
            map.insert("properties".to_string(), other);
            return Value::Object(map);
        }
        None => return Value::Object(map),
    };
    for field in PROPERTY_HOIST_FIELDS {
        if map.contains_key(*field) {
            continue;
        }
        if props
            .get(*field)
            .is_some_and(|v| !v.is_object() && !v.is_array())
        {
            let v = props.remove(*field).expect("checked above");
            map.insert((*field).to_string(), v);
        }
    }
    if !props.is_empty() {
        map.insert("properties".to_string(), Value::Object(props));
    }
    Value::Object(map)
}

/// An array of 2+ objects qualifies as a record array.
fn is_record_array(arr: &[Value]) -> bool {
    arr.len() >= 2 && arr.iter().all(Value::is_object)
}

/// Render the located record array as a table, then append one `key: value`
/// line per remaining top-level key. Envelope fields (`has_more`, `offset`,
/// counts) must survive rendering: dropping them made a truncated `query`
/// page read as complete.
fn render_table_with_siblings(value: &Value, found: &RecordArray, truncate: bool) -> String {
    let mut out = render_table(&found.records, &found.columns, truncate);
    let (Value::Object(map), Some(array_key)) = (value, &found.key) else {
        return out;
    };
    for (k, v) in map {
        if k == array_key {
            continue;
        }
        let text = match v {
            // A newline-bearing string renders as its JSON literal (one line,
            // lossless) so a stored value cannot fabricate a sibling line or
            // table row (ADR-078 Amendment 2 escaping contract).
            Value::String(s) if !s.contains(['\n', '\r']) => s.clone(),
            // Non-string scalars and nested values: compact JSON, untruncated
            // — sibling fidelity is the point of this path.
            other => serde_json::to_string(other).unwrap_or_default(),
        };
        out.push_str(&format!("{k}: {text}\n"));
    }
    out
}

/// Collect column names in first-seen order across all records.
fn collect_keys(records: &[Value]) -> Vec<String> {
    let mut seen = HashSet::new();
    let mut keys = Vec::new();
    for record in records {
        if let Value::Object(map) = record {
            for k in map.keys() {
                if seen.insert(k.clone()) {
                    keys.push(k.clone());
                }
            }
        }
    }
    keys
}

// ── Markdown table renderer (ADR-078 §3a) ───────────────────────────────────

/// Render a record array as a GitHub-Flavored Markdown table.
fn render_table(records: &[Value], keys: &[String], truncate: bool) -> String {
    let mut out = String::new();

    out.push('|');
    for k in keys {
        out.push(' ');
        out.push_str(k);
        out.push_str(" |");
    }
    out.push('\n');

    out.push('|');
    for _ in keys {
        out.push_str("---|");
    }
    out.push('\n');

    for record in records {
        out.push('|');
        for k in keys {
            let cell = record.get(k).unwrap_or(&Value::Null);
            let text = cell_text(k, cell, truncate);
            out.push(' ');
            out.push_str(&text);
            out.push_str(" |");
        }
        out.push('\n');
    }

    out
}

/// Column names exempt from cell truncation: identity and decision fields
/// must arrive whole — a truncated id cannot be resolved and a truncated
/// title cannot be selected on.
fn truncation_exempt(key: &str) -> bool {
    matches!(
        key,
        "id" | "kind"
            | "status"
            | "priority"
            | "relation"
            | "title"
            | "name"
            | "signature"
            | "slug"
            | "assignee"
            | "from"
            | "to"
            | "due"
    ) || key.ends_with("_id")
        || key.ends_with("_at")
        || key.starts_with("due")
}

/// Format a cell value: escape `|`, collapse newlines, truncate to ~120 chars
/// unless `truncate` is off or the column is identity/decision-bearing.
///
/// Nested values are elided to a constant marker (`{…}` / `[…]`) rather than
/// stringified and cut mid-JSON: truncated pseudo-JSON reads as data while
/// silently missing fields. Full content is one `format=json` or `get` away.
fn cell_text(key: &str, value: &Value, truncate: bool) -> String {
    let raw = match value {
        Value::Null => String::new(),
        Value::Bool(b) => b.to_string(),
        Value::Number(n) => n.to_string(),
        Value::String(s) => s.clone(),
        Value::Object(_) => return "{…}".to_string(),
        Value::Array(arr) => {
            if arr.iter().any(|v| v.is_object() || v.is_array()) {
                return "[…]".to_string();
            }
            // Arrays of scalars (tags, ids) stay compact JSON.
            serde_json::to_string(value).unwrap_or_default()
        }
    };

    // Escape literal `|` and collapse embedded newlines to a space.
    let escaped = raw.replace('|', "\\|").replace(['\n', '\r'], " ");

    if !truncate || truncation_exempt(key) {
        return escaped;
    }

    // Truncate to approximately CELL_TRUNCATE *characters* (char boundary,
    // not byte index — slicing on a byte offset can panic on multi-byte chars).
    let char_count = escaped.chars().count();
    if char_count > CELL_TRUNCATE {
        let truncated: String = escaped.chars().take(CELL_TRUNCATE).collect();
        format!("{truncated}...")
    } else {
        escaped
    }
}

/// Format an instant in UTC using RFC3339 whole seconds and a `Z` suffix.
///
/// Fractional seconds are omitted. Chrono's supported years and signed
/// expanded-year rendering are inherited; no additional range validation is done.
/// Parsing and error policy remain with callers.
pub fn format_utc_rfc3339_seconds<Tz: chrono::TimeZone>(value: &chrono::DateTime<Tz>) -> String {
    value
        .with_timezone(&chrono::Utc)
        .to_rfc3339_opts(chrono::SecondsFormat::Secs, true)
}

/// Convert a microsecond epoch `i64` to an exact UTC ISO-8601 string.
///
/// Output always carries six fractional digits and a `Z` suffix. Years
/// 0000–9999 use the RFC 3339 spelling; other years use Chrono's signed
/// expanded-year convention. The full `i64` microsecond range is supported.
pub fn micros_to_iso(micros: i64) -> String {
    if let Some(dt) = chrono::DateTime::<chrono::Utc>::from_timestamp_micros(micros) {
        return dt.to_rfc3339_opts(chrono::SecondsFormat::Micros, true);
    }

    // Gregorian leap positions repeat every 400 years. Euclidean reduction
    // keeps the remainder in 1970–2369, including for negative timestamps.
    const CYCLE_MICROS: i64 = 146_097 * 86_400 * 1_000_000;
    let cycles = micros.div_euclid(CYCLE_MICROS);
    let reduced =
        chrono::DateTime::<chrono::Utc>::from_timestamp_micros(micros.rem_euclid(CYCLE_MICROS))
            .expect("400-year remainder is within Chrono's range");
    let year = i64::from(chrono::Datelike::year(&reduced)) + cycles * 400;
    let rendered = reduced.to_rfc3339_opts(chrono::SecondsFormat::Micros, true);
    format!("{year:+05}{}", &rendered[4..])
}

/// Parse an RFC 3339 timestamp (offset required) into microsecond epoch
/// `i64` — the inverse of [`micros_to_iso`] within the RFC 3339 four-digit
/// year range. Expanded ISO years are not accepted. This is the single parse
/// point for caller-supplied instants entering storage comparisons.
///
/// Leading/trailing whitespace is tolerated. Date-only and offset-less forms
/// are rejected; callers own the verb-specific error context around the
/// returned `ParseError`.
pub fn rfc3339_to_utc_micros(raw: &str) -> Result<i64, chrono::ParseError> {
    chrono::DateTime::parse_from_rfc3339(raw.trim()).map(|dt| dt.timestamp_micros())
}

/// How the response envelope is presented to the caller.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
#[serde(rename_all = "snake_case")]
pub enum PresentationMode {
    /// Token-efficient. Default for MCP callers (agents).
    ///
    /// Short UUIDs (8-char), exact UTC timestamps with relative labels on
    /// list rows, empty fields dropped, structural nulls preserved, and
    /// score fields truncated to 3 significant figures.
    #[default]
    Agent,
    /// Full canonical shape. Default for `kkernel exec` and CI/scripted callers.
    ///
    /// No transformation — handler output passes through as-is.
    Verbose,
    /// Pretty-printed terminal output. Default for `khive` CLI.
    ///
    /// **At the MCP runtime level this is identical to `Verbose`** — the
    /// canonical JSON is returned unchanged. Terminal formatting (relative
    /// timestamps, glyph substitution, table layout) is applied by the CLI
    /// layer (`khive-cli::format::pretty`), not the MCP response pipeline.
    Human,
}

/// Lifecycle/operational `null` fields that are PRESERVED in Agent mode.
///
/// These fields carry state meaning (absent ≠ known-unknown) and must not be
/// dropped. The channel-health fields distinguish a quarantine-only identity
/// from a heartbeat row whose liveness facts were actually observed.
const LIFECYCLE_NULL_PRESERVE: &[&str] = &[
    "completed_at",
    "deleted_at",
    "due_at",
    "read_at",
    "started_at",
    "superseded_at",
    "applied_at",
    "withdrawn_at",
    "reviewed_at",
    "parent_id",
    "superseded_by",
    "replaced_by",
    "poll_interval_secs",
    "stalled",
    "last_success_at",
    "last_poll_attempt_at",
    "last_failure_at",
    "last_error",
    "consecutive_failures",
];

/// Empty collection fields that define a stable response envelope and must
/// survive Agent-mode compaction. Dropping these turns an empty page into a
/// different response type and leaves callers unable to distinguish an empty
/// result from a missing/unsupported field.
const EMPTY_ARRAY_PRESERVE: &[&str] = &[
    "items",
    "entities",
    "notes",
    "edges",
    "results",
    "entries",
    "neighbors",
];

fn is_stable_list_envelope(map: &Map<String, Value>) -> bool {
    map.contains_key("requested_limit")
        && map.contains_key("effective_limit")
        && map.contains_key("limit_clamped")
        && EMPTY_ARRAY_PRESERVE
            .iter()
            .any(|field| map.contains_key(*field))
}

/// Keyset cursor pages outside the ADR-023 envelope — `knowledge.list(after=…)`
/// returns `{results, limit, order, next_after}` — are structural in the same
/// way (ADR-045 Amendment 4): an empty `results` page and a terminal
/// `next_after: null` are the walk's completion signals, so a caller that
/// cannot see them cannot stop. A `results` array without a sibling
/// `next_after` key is an ordinary response and gets the generic transform.
fn is_keyset_cursor_envelope(map: &Map<String, Value>) -> bool {
    map.contains_key("next_after")
        && (map.get("results").is_some_and(Value::is_array)
            || (map.get("head_seq").is_some_and(Value::is_number)
                && map.get("entries").is_some_and(Value::is_array)))
}

fn is_stream_entry(map: &Map<String, Value>) -> bool {
    map.get("seq").is_some_and(Value::is_number)
        && map.contains_key("id")
        && map.contains_key("created_at")
        && map.contains_key("record")
}

/// Field names carrying caller-supplied payload timestamps that must never be
/// transformed, regardless of nesting.
///
/// These encode domain semantics the caller needs to round-trip verbatim —
/// e.g. `trigger_at` on a `schedule.remind`/`schedule.schedule` create
/// response, returned as a top-level convenience field alongside `id` and
/// `full_id`, not nested under `"properties"`. The `inside_properties` guard
/// alone only protects fields nested under a literal `"properties"` key
/// (as returned by `agenda`/`get`); it does not cover this top-level case,
/// which older Agent presentation rewrote into a relative or minute-truncated
/// form, discarding the seconds and offset needed for round trips (#871).
///
/// `due` on `gtd.assign`/`gtd.tasks`/`gtd.next` responses is the same shape:
/// a top-level convenience field mirroring `properties.due`, which
/// `parse_due` already normalizes to full RFC 3339.
const PAYLOAD_TIMESTAMP_FIELDS: &[&str] = &["trigger_at", "due"];

/// UUID fields whose canonical value is itself a strict-verb input.
///
/// Shortening these would make a successful response fail when submitted back
/// to the verb that produced or consumes it. `context_entity_id` and
/// `thread_id` are explicit stable references rather than prefix searches;
/// `outbound_ref` is the exact correlation key consumed by `comm.delivered`;
/// `parent_id` is the explicit ancestry reference consumed by `propose`;
/// `session_id` is an exact event-list filter; and `project_id` is the exact
/// provenance anchor required by git issue and pull-request creation.
const ROUND_TRIP_FULL_UUID_FIELDS: &[&str] = &[
    "context_entity_id",
    "thread_id",
    "outbound_ref",
    "parent_id",
    "session_id",
    "project_id",
];

/// Score field names that are truncated to 3 significant figures in Agent mode.
const SCORE_FIELDS: &[&str] = &[
    "score",
    "rank_score",
    "vector_similarity",
    "keyword_score",
    "salience",
    "decay_factor",
    "rrf_score",
    "similarity",
    "cross_encoder_score",
    "graph_proximity_score",
];

/// UUID v4 canonical string length (8-4-4-4-12 = 32 hex + 4 dashes = 36).
const UUID_CANONICAL_LEN: usize = 36;

/// Return true for fields whose whole-string UUID values may be shortened in
/// Agent mode. Content-like fields are intentionally excluded even when their
/// value happens to be UUID-shaped.
///
/// `full_id` and strict round-trip fields are explicitly excluded: their
/// purpose is to give callers a stable chaining handle, so shortening them
/// would produce a value that the corresponding strict verb rejects.
fn should_shorten_uuid_field(key: &str) -> bool {
    if key == "full_id" || key == "bridge_instance_id" || ROUND_TRIP_FULL_UUID_FIELDS.contains(&key)
    {
        return false;
    }
    key == "id" || key.ends_with("_id") || matches!(key, "superseded_by" | "replaced_by")
}

/// Transform a successful verb result value according to the given
/// [`PresentationMode`].
///
/// - `Verbose` / `Human`: returns `value` unchanged.
/// - `Agent`: applies UUID shortening, exact UTC timestamp rendering, empty-field
///   dropping, structural-null preservation, and score truncation.
///
/// `now_unix_seconds` is a whole-second clock for callers without a finer
/// sample. All relative list-row labels within a response use this instant.
pub fn present(value: Value, mode: PresentationMode, now_unix_seconds: i64) -> Value {
    present_with_policy(
        value,
        mode,
        now_unix_seconds,
        VerbPresentationPolicy::Standard,
    )
}

/// Present a successful result using its trusted registered verb policy.
/// Receipt policies preserve only their closed string paths, not descendants.
pub fn present_with_policy(
    value: Value,
    mode: PresentationMode,
    now_unix_seconds: i64,
    policy: VerbPresentationPolicy,
) -> Value {
    present_with_policy_at(value, mode, now_unix_seconds.into(), policy)
}

/// A response-wide clock sample. Fractional precision distinguishes a newly
/// stored row from a truly future row within the same Unix second.
#[derive(Clone, Copy)]
pub struct PresentationNow {
    seconds: i64,
    nanoseconds: u32,
}

impl From<i64> for PresentationNow {
    fn from(seconds: i64) -> Self {
        Self {
            seconds,
            nanoseconds: 0,
        }
    }
}

impl From<i32> for PresentationNow {
    fn from(seconds: i32) -> Self {
        i64::from(seconds).into()
    }
}

impl From<chrono::DateTime<chrono::Utc>> for PresentationNow {
    fn from(now: chrono::DateTime<chrono::Utc>) -> Self {
        Self {
            seconds: now.timestamp(),
            nanoseconds: now.timestamp_subsec_nanos(),
        }
    }
}

/// Present with the response's single sampled instant, including its fraction.
pub fn present_with_policy_at(
    value: Value,
    mode: PresentationMode,
    now: PresentationNow,
    policy: VerbPresentationPolicy,
) -> Value {
    if policy == VerbPresentationPolicy::AlwaysVerbose {
        return value;
    }
    match mode {
        PresentationMode::Verbose | PresentationMode::Human => value,
        PresentationMode::Agent => {
            // These root paths are selected by the registered agenda handler,
            // never by a payload marker or a nested lookalike. The cursor's
            // timestamp spelling and full UUID jointly define its seek position.
            let mut value = value;
            let agenda_next = (policy == VerbPresentationPolicy::AgendaContinuation)
                .then(|| value.as_object_mut().and_then(|map| map.remove("next")))
                .flatten();
            let agenda_empty = policy == VerbPresentationPolicy::AgendaContinuation
                && value
                    .get("events")
                    .and_then(Value::as_array)
                    .is_some_and(Vec::is_empty);
            let config = AgentTransformConfig {
                preserved_nulls: LIFECYCLE_NULL_PRESERVE.iter().copied().collect(),
                scores: SCORE_FIELDS.iter().copied().collect(),
                payload_timestamps: PAYLOAD_TIMESTAMP_FIELDS.iter().copied().collect(),
                now,
            };
            let mut value = transform_agent(
                value,
                &config,
                AgentTreeContext {
                    inside_properties: false,
                    object_properties: false,
                    array_member: false,
                    receipt_context: match policy {
                        VerbPresentationPolicy::StreamAppendReceipt => ReceiptContext::AppendRoot,
                        VerbPresentationPolicy::StreamBatchReceipts => ReceiptContext::BatchRoot,
                        _ => ReceiptContext::None,
                    },
                },
            );
            if let Some(map) = value.as_object_mut() {
                if let Some(next) = agenda_next {
                    map.insert("next".into(), next);
                }
                if agenda_empty {
                    map.insert("events".into(), Value::Array(Vec::new()));
                }
            }
            value
        }
    }
}

#[derive(Clone, Copy, PartialEq, Eq)]
enum ReceiptContext {
    None,
    AppendRoot,
    BatchRoot,
    BatchResults,
    BatchMember,
}

struct AgentTransformConfig {
    preserved_nulls: HashSet<&'static str>,
    scores: HashSet<&'static str>,
    payload_timestamps: HashSet<&'static str>,
    now: PresentationNow,
}

#[derive(Clone, Copy)]
struct AgentTreeContext {
    inside_properties: bool,
    object_properties: bool,
    array_member: bool,
    receipt_context: ReceiptContext,
}

/// Apply the Agent-mode transform to an arbitrary JSON value.
///
/// `inside_properties` is `true` when recursing inside a `"properties"` value.
/// Caller-supplied payload timestamps (e.g. `trigger_at`) must not be normalized
/// because they encode domain semantics the agent may need to round-trip.
fn transform_agent(
    value: Value,
    config: &AgentTransformConfig,
    context: AgentTreeContext,
) -> Value {
    match value {
        Value::Object(map) => {
            let preserve_list_envelope =
                is_stable_list_envelope(&map) || is_keyset_cursor_envelope(&map);
            let stream_entry = is_stream_entry(&map);
            let relative_created_at = (context.array_member
                && !context.inside_properties
                && !map.contains_key("created_at_relative")
                && !matches!(
                    context.receipt_context,
                    ReceiptContext::AppendRoot | ReceiptContext::BatchMember
                ))
            .then(|| map.get("created_at").and_then(Value::as_str))
            .flatten()
            .and_then(|raw| {
                let (_, created_at) = exact_timestamp(raw)?;
                let age = config.now.seconds.checked_sub(created_at)?;
                // Floor the full fractional age. The lexicographic comparison
                // also handles canonical fractions longer than nanoseconds.
                age.checked_sub(i64::from(
                    timestamp_fraction_cmp(raw, config.now.nanoseconds) == Ordering::Greater,
                ))
            })
            .filter(|difference| *difference >= 0)
            .map(relative_time);
            let mut out = Map::new();
            for (k, v) in map {
                if stream_entry && k == "record" {
                    out.insert(k, v);
                    continue;
                }
                if v.is_string()
                    && ((context.receipt_context == ReceiptContext::AppendRoot
                        && k == "created_at")
                        || (context.receipt_context == ReceiptContext::BatchMember
                            && matches!(k.as_str(), "created_at" | "updated_at")))
                {
                    out.insert(k, v);
                    continue;
                }
                let child_receipt_context = if context.receipt_context == ReceiptContext::BatchRoot
                    && k == "results"
                    && v.is_array()
                {
                    ReceiptContext::BatchResults
                } else {
                    ReceiptContext::None
                };
                // ADR-045 Amendment 3 scopes the empty-string carve-out to
                // strings nested under an object-valued `properties`; a
                // scalar or array `properties` value gets no carve-out.
                let child_inside_properties = context.inside_properties || k == "properties";
                let child_object_properties =
                    context.object_properties || (k == "properties" && v.is_object());
                let transformed = transform_field_agent(
                    &k,
                    v,
                    config,
                    AgentFieldContext {
                        inside_properties: child_inside_properties,
                        object_properties: child_object_properties,
                        preserve_list_envelope,
                        receipt_context: child_receipt_context,
                    },
                );
                match transformed {
                    None => {} // drop
                    Some(tv) => {
                        out.insert(k, tv);
                    }
                }
            }
            if let Some(relative) = relative_created_at {
                out.insert("created_at_relative".to_string(), Value::String(relative));
            }
            Value::Object(out)
        }
        Value::Array(arr) => {
            let items: Vec<Value> = arr
                .into_iter()
                .map(|v| {
                    transform_agent(
                        v,
                        config,
                        AgentTreeContext {
                            inside_properties: context.inside_properties,
                            object_properties: context.object_properties,
                            array_member: true,
                            receipt_context: if context.receipt_context
                                == ReceiptContext::BatchResults
                            {
                                ReceiptContext::BatchMember
                            } else {
                                ReceiptContext::None
                            },
                        },
                    )
                })
                .collect();
            Value::Array(items)
        }
        other => other,
    }
}

/// Transform a single named field value under Agent mode.
///
/// Returns `None` if the field should be dropped.
///
/// `inside_properties` suppresses timestamp normalization for caller-submitted
/// payload values nested under a literal `"properties"` key (e.g. `trigger_at`
/// as returned by `agenda`/`get`). `payload_timestamps` suppresses normalization
/// by field name regardless of nesting, covering top-level convenience fields
/// such as the `trigger_at` returned directly in a `schedule.remind`/
/// `schedule.schedule` create response (#871). Metadata timestamps at the top
/// level (`created_at`, `updated_at`) still render as exact UTC instants.
#[derive(Clone, Copy)]
struct AgentFieldContext {
    inside_properties: bool,
    object_properties: bool,
    preserve_list_envelope: bool,
    receipt_context: ReceiptContext,
}

fn transform_field_agent(
    key: &str,
    value: Value,
    config: &AgentTransformConfig,
    context: AgentFieldContext,
) -> Option<Value> {
    match &value {
        // Preserve lifecycle and stable-envelope nulls; drop other nulls.
        Value::Null => {
            if config.preserved_nulls.contains(key)
                || (context.preserve_list_envelope && key == "next_after")
            {
                Some(value)
            } else {
                None
            }
        }
        // Stable page-envelope arrays remain present even when empty.
        Value::Array(a)
            if context.preserve_list_envelope
                && a.is_empty()
                && EMPTY_ARRAY_PRESERVE.contains(&key) =>
        {
            Some(value)
        }
        // Preserve empty strings under a record's `properties` object: those
        // keys exist only because a caller wrote them, so `""` there is data
        // (set-to-empty vs absent, ADR-045 Amendment 3, issue #1995). Empty
        // arrays and objects under `properties` are still dropped per the
        // amendment's scope note.
        Value::String(s) if s.is_empty() && context.object_properties => Some(value),
        // Drop other empty strings, arrays, objects.
        Value::String(s) if s.is_empty() => None,
        Value::Array(a) if a.is_empty() => None,
        Value::Object(o) if o.is_empty() => None,
        // Truncate score fields.
        Value::Number(_) if config.scores.contains(key) => {
            if let Some(f) = value.as_f64() {
                Some(truncate_to_3_sig_figs(f))
            } else {
                Some(value)
            }
        }
        // Shorten UUIDs only in fields whose names carry ID semantics.
        Value::String(s) if is_canonical_uuid(s) && should_shorten_uuid_field(key) => {
            Some(Value::String(s[..8].to_string()))
        }
        // Render whole, offset-bearing timestamps in exact UTC form unless
        // this is caller-supplied or otherwise protected payload data.
        Value::String(s)
            if !context.inside_properties
                && !config.payload_timestamps.contains(key)
                && looks_like_iso8601(s) =>
        {
            Some(Value::String(
                exact_timestamp(s).map_or_else(|| s.clone(), |(rendered, _)| rendered),
            ))
        }
        // Recurse into objects and arrays.
        Value::Object(_) | Value::Array(_) => Some(transform_agent(
            value,
            config,
            AgentTreeContext {
                inside_properties: context.inside_properties,
                object_properties: context.object_properties,
                array_member: false,
                receipt_context: context.receipt_context,
            },
        )),
        // Everything else passes through.
        _ => Some(value),
    }
}

/// Returns `true` if `s` looks like a canonical UUID (36 chars, standard form).
fn is_canonical_uuid(s: &str) -> bool {
    if s.len() != UUID_CANONICAL_LEN {
        return false;
    }
    let b = s.as_bytes();
    // Pattern: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    b[8] == b'-'
        && b[13] == b'-'
        && b[18] == b'-'
        && b[23] == b'-'
        && b[..8].iter().all(|c| c.is_ascii_hexdigit())
        && b[9..13].iter().all(|c| c.is_ascii_hexdigit())
        && b[14..18].iter().all(|c| c.is_ascii_hexdigit())
        && b[19..23].iter().all(|c| c.is_ascii_hexdigit())
        && b[24..].iter().all(|c| c.is_ascii_hexdigit())
}

/// Returns `true` if `s` looks like an ISO-8601 datetime string.
///
/// Heuristic: starts with `YYYY-MM-DDTHH:` (16 chars, proper digit positions).
fn looks_like_iso8601(s: &str) -> bool {
    if s.len() < 16 {
        return false;
    }
    let b = s.as_bytes();
    b[4] == b'-'
        && b[7] == b'-'
        && b[10] == b'T'
        && b[13] == b':'
        && b[..4].iter().all(|c| c.is_ascii_digit())
        && b[5..7].iter().all(|c| c.is_ascii_digit())
        && b[8..10].iter().all(|c| c.is_ascii_digit())
        && b[11..13].iter().all(|c| c.is_ascii_digit())
}

/// Render a whole timestamp in UTC while retaining its original fraction digits.
fn exact_timestamp(s: &str) -> Option<(String, i64)> {
    let unix = parse_iso8601_unix(s)?;
    let tail = s.get(19..)?;
    let fraction = if let Some(after_dot) = tail.strip_prefix('.') {
        let digits = after_dot.bytes().take_while(u8::is_ascii_digit).count();
        tail.get(..digits + 1)?
    } else {
        ""
    };
    let utc = chrono::DateTime::<chrono::Utc>::from_timestamp(unix, 0)?;
    Some((
        format!("{}{fraction}Z", utc.format("%Y-%m-%dT%H:%M:%S")),
        unix,
    ))
}

/// Compare the timestamp's decimal fraction with a sampled nanosecond value.
/// Digits beyond nanoseconds matter when the leading nine digits tie.
fn timestamp_fraction_cmp(timestamp: &str, now_nanoseconds: u32) -> Ordering {
    let fraction = if timestamp.as_bytes().get(19) == Some(&b'.') {
        timestamp.as_bytes()[20..]
            .split(|byte| !byte.is_ascii_digit())
            .next()
            .unwrap_or_default()
    } else {
        &[]
    };
    let now_fraction = format!("{now_nanoseconds:09}");
    for index in 0..fraction.len().max(9) {
        let created_digit = fraction.get(index).copied().unwrap_or(b'0');
        let now_digit = now_fraction.as_bytes().get(index).copied().unwrap_or(b'0');
        match created_digit.cmp(&now_digit) {
            Ordering::Equal => {}
            difference => return difference,
        }
    }
    Ordering::Equal
}

/// Parse a whole ISO-8601 datetime with an explicit offset to Unix seconds.
///
/// Accepts `YYYY-MM-DDTHH:MM:SS[.frac](Z|±HH:MM|±HHMM)`. An offset-less,
/// invalid or trailing-text value stays byte-exact in Agent presentation.
fn parse_iso8601_unix(s: &str) -> Option<i64> {
    if s.len() < 20 {
        return None;
    }
    let b = s.as_bytes();
    if b[4] != b'-' || b[7] != b'-' || b[10] != b'T' || b[13] != b':' || b[16] != b':' {
        return None;
    }
    let year: i64 = parse_digits(&b[0..4])?;
    let month: i64 = parse_digits(&b[5..7])?;
    let day: i64 = parse_digits(&b[8..10])?;
    let hour: i64 = parse_digits(&b[11..13])?;
    let minute: i64 = parse_digits(&b[14..16])?;
    let second: i64 = parse_digits(&b[17..19])?;

    let local = chrono::NaiveDate::from_ymd_opt(
        year.try_into().ok()?,
        month.try_into().ok()?,
        day.try_into().ok()?,
    )?
    .and_hms_opt(
        hour.try_into().ok()?,
        minute.try_into().ok()?,
        second.try_into().ok()?,
    )?
    .and_utc()
    .timestamp();
    let offset_secs = parse_tz_offset_secs(s.get(19..)?)?;
    local.checked_sub(offset_secs)
}

/// Parse the tail of an ISO-8601 timestamp (everything from byte index 19
/// onward, i.e. after the whole-seconds field) into a UTC offset in seconds.
///
/// Handles, in order: optional fractional seconds (`.nnn`, skipped — this
/// parser only has whole-second precision), then one of:
/// - `"Z"` → offset 0
/// - `±HH:MM` or the compact `±HHMM` form → `sign * (hh*3600 + mm*60)`
///
/// Returns `None` for anything else (malformed tail).
fn parse_tz_offset_secs(tail: &str) -> Option<i64> {
    let mut rest = tail;
    if let Some(after_dot) = rest.strip_prefix('.') {
        let frac_len = after_dot.bytes().take_while(u8::is_ascii_digit).count();
        if frac_len == 0 {
            return None;
        }
        rest = &after_dot[frac_len..];
    }

    if rest == "Z" {
        return Some(0);
    }

    let sign: i64 = match rest.as_bytes().first()? {
        b'+' => 1,
        b'-' => -1,
        _ => return None,
    };
    let digits = &rest[1..];
    let (hh, mm) = match digits.len() {
        // "HH:MM"
        5 if digits.as_bytes()[2] == b':' => (
            parse_digits(&digits.as_bytes()[0..2])?,
            parse_digits(&digits.as_bytes()[3..5])?,
        ),
        // "HHMM"
        4 => (
            parse_digits(&digits.as_bytes()[0..2])?,
            parse_digits(&digits.as_bytes()[2..4])?,
        ),
        _ => return None,
    };
    if hh > 23 || mm > 59 {
        return None;
    }
    Some(sign * (hh * 3600 + mm * 60))
}

fn parse_digits(b: &[u8]) -> Option<i64> {
    let s = std::str::from_utf8(b).ok()?;
    s.parse().ok()
}

/// Format a duration in seconds as a relative time string (e.g. `"3m ago"`).
fn relative_time(diff_secs: i64) -> String {
    if diff_secs < 60 {
        format!("{diff_secs}s ago")
    } else if diff_secs < 3600 {
        format!("{}m ago", diff_secs / 60)
    } else if diff_secs < 86400 {
        format!("{}h ago", diff_secs / 3600)
    } else {
        format!("{}d ago", diff_secs / 86400)
    }
}

/// Truncate a float to 3 significant figures, returning a `serde_json::Value`.
fn truncate_to_3_sig_figs(f: f64) -> Value {
    if f == 0.0 || !f.is_finite() {
        return Value::from(f);
    }
    let magnitude = f.abs().log10().floor() as i32;
    let factor = 10f64.powi(2 - magnitude);
    let rounded = (f * factor).round() / factor;
    // Re-serialize through serde_json to avoid floating-point noise.
    serde_json::Number::from_f64(rounded)
        .map(Value::Number)
        .unwrap_or(Value::from(rounded))
}

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

    /// A fixed "now" for deterministic tests: 2025-05-23T16:08:00Z.
    const NOW: i64 = 1_748_016_480;

    #[test]
    fn utc_rfc3339_seconds_normalizes_offsets_and_omits_fractions() {
        for (raw, expected) in [
            (
                "2026-01-01T00:15:30.987654321+01:00",
                "2025-12-31T23:15:30Z",
            ),
            ("1969-12-31T23:59:59.999999999Z", "1969-12-31T23:59:59Z"),
        ] {
            let instant = chrono::DateTime::parse_from_rfc3339(raw).unwrap();
            assert_eq!(format_utc_rfc3339_seconds(&instant), expected, "{raw}");
        }
    }

    #[test]
    fn micros_to_iso_preserves_chrono_range_spelling() {
        for (micros, expected) in [
            (0, "1970-01-01T00:00:00.000000Z"),
            (-1, "1969-12-31T23:59:59.999999Z"),
            (1_748_016_480_123_456, "2025-05-23T16:08:00.123456Z"),
            (-62_198_755_200_000_000, "-0001-01-01T00:00:00.000000Z"),
            (253_402_300_800_000_000, "+10000-01-01T00:00:00.000000Z"),
            (-8_334_601_228_800_000_000, "-262143-01-01T00:00:00.000000Z"),
            (8_210_266_876_799_999_999, "+262142-12-31T23:59:59.999999Z"),
        ] {
            assert!(
                chrono::DateTime::<chrono::Utc>::from_timestamp_micros(micros).is_some(),
                "{micros}"
            );
            assert_eq!(micros_to_iso(micros), expected, "{micros}");
        }
    }

    #[test]
    fn micros_to_iso_formats_outside_chrono_range_exactly() {
        for (micros, expected) in [
            (i64::MIN, "-290308-12-21T19:59:05.224192Z"),
            (i64::MAX, "+294247-01-10T04:00:54.775807Z"),
            (-8_334_601_228_800_000_001, "-262144-12-31T23:59:59.999999Z"),
            (8_210_266_876_800_000_000, "+262143-01-01T00:00:00.000000Z"),
            (-8_898_108_636_303_876_544, "-280000-02-29T12:34:56.123456Z"),
            (8_776_940_198_400_000_001, "+280100-03-01T00:00:00.000001Z"),
        ] {
            assert!(
                chrono::DateTime::<chrono::Utc>::from_timestamp_micros(micros).is_none(),
                "{micros}"
            );
            assert_eq!(micros_to_iso(micros), expected, "{micros}");
        }
    }

    #[test]
    fn expanded_micros_timestamps_pass_through_agent_without_relative_labels() {
        for (micros, expected) in [
            (i64::MIN, "-290308-12-21T19:59:05.224192Z"),
            (i64::MAX, "+294247-01-10T04:00:54.775807Z"),
        ] {
            let shown = present(
                json!({"items": [{"created_at": micros_to_iso(micros)}]}),
                PresentationMode::Agent,
                NOW,
            );
            assert_eq!(shown, json!({"items": [{"created_at": expected}]}));
            assert!(rfc3339_to_utc_micros(expected).is_err());
        }
    }

    #[test]
    fn rfc3339_to_utc_micros_round_trips_and_rejects_partial_forms() {
        let micros = 1_748_016_480_000_000_i64;
        assert_eq!(rfc3339_to_utc_micros(&micros_to_iso(micros)), Ok(micros));
        // Offset spellings resolve to the same instant; whitespace tolerated.
        // The offset spelling names the same instant as NOW.
        assert_eq!(
            rfc3339_to_utc_micros(" 2025-05-23T12:08:00-04:00 "),
            Ok(micros)
        );
        assert!(rfc3339_to_utc_micros("2026-05-23").is_err());
        assert!(rfc3339_to_utc_micros("2026-05-23T16:18:00").is_err());
    }

    fn agent(v: Value) -> Value {
        present(v, PresentationMode::Agent, NOW)
    }

    #[test]
    fn agent_preserves_empty_string_under_properties() {
        // ADR-045 Amendment 3 (issue #1995): a key under `properties` exists
        // only because a caller wrote it, so `""` there distinguishes
        // set-to-empty from absent and must survive Agent mode — at any
        // nesting depth under `properties`.
        let v = json!({
            "id": "a1b2c3d4",
            "summary": "",
            "properties": {"k": "", "nested": {"deep": ""}},
        });
        let out = agent(v);
        assert_eq!(out["properties"]["k"], json!(""));
        assert_eq!(out["properties"]["nested"]["deep"], json!(""));
        // Control: outside `properties` the empty-string drop still applies.
        assert!(out.get("summary").is_none());
    }

    #[test]
    fn agent_drops_scalar_empty_properties_value() {
        // The carve-out applies only to strings nested under an object-valued
        // `properties`; a scalar `properties: ""` is the field's own value,
        // not a caller-written key under it, and drops like any empty string.
        let v = json!({
            "id": "a1b2c3d4",
            "properties": "",
        });
        let out = agent(v);
        assert!(out.get("properties").is_none());
    }

    #[test]
    fn agent_still_drops_empty_containers_under_properties() {
        // The amendment's scope note keeps the container drop: empty arrays
        // and objects under `properties` are not carved out.
        let v = json!({
            "id": "a1b2c3d4",
            "properties": {"tags": [], "meta": {}, "kept": "x"},
        });
        let out = agent(v);
        assert!(out["properties"].get("tags").is_none());
        assert!(out["properties"].get("meta").is_none());
        assert_eq!(out["properties"]["kept"], json!("x"));
    }

    #[test]
    fn verbose_passthrough() {
        let v = json!({"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890", "title": "X"});
        let out = present(v.clone(), PresentationMode::Verbose, NOW);
        assert_eq!(out, v);
    }

    #[test]
    fn agent_shortens_uuid() {
        let v = json!({"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890"});
        let out = agent(v);
        assert_eq!(out["id"], json!("a1b2c3d4"));
    }

    #[test]
    fn agent_drops_empty_string() {
        let v = json!({"title": "ok", "description": ""});
        let out = agent(v);
        assert!(out.get("description").is_none());
        assert_eq!(out["title"], json!("ok"));
    }

    #[test]
    fn agent_drops_empty_array() {
        let v = json!({"tags": [], "title": "ok"});
        let out = agent(v);
        assert!(out.get("tags").is_none());
    }

    #[test]
    fn agent_preserves_empty_list_page_arrays() {
        let v = json!({
            "items": [],
            "entities": [],
            "notes": [],
            "edges": [],
            "results": [],
            "entries": [],
            "neighbors": [],
            "next_after": null,
            "requested_limit": 10,
            "effective_limit": 10,
            "limit_clamped": false,
        });
        let out = agent(v);
        for key in EMPTY_ARRAY_PRESERVE {
            assert_eq!(out[*key], json!([]), "missing structural key {key}");
        }
        assert_eq!(out["next_after"], json!(null));
    }

    #[test]
    fn agent_preserves_keyset_cursor_envelope_completion_signals() {
        // knowledge.list(after=…) terminal/empty page: both signals survive.
        let out = agent(json!({
            "results": [],
            "limit": 500,
            "order": "created_at ASC, id ASC",
            "next_after": null,
        }));
        assert_eq!(out["results"], json!([]));
        assert!(
            out.get("next_after").is_some_and(Value::is_null),
            "terminal cursor page must keep next_after:null: {out}"
        );
    }

    #[test]
    fn agent_results_without_next_after_is_not_a_cursor_envelope() {
        let out = agent(json!({"results": [], "limit": 500, "title": "ordinary response"}));
        assert!(out.get("results").is_none());
    }

    #[test]
    fn agent_still_drops_empty_arrays_outside_list_envelopes() {
        let out = agent(json!({"items": [], "entities": [], "title": "ordinary response"}));
        assert!(out.get("items").is_none());
        assert!(out.get("entities").is_none());
    }

    #[test]
    fn agent_drops_empty_object() {
        let v = json!({"properties": {}, "title": "ok"});
        let out = agent(v);
        assert!(out.get("properties").is_none());
    }

    #[test]
    fn agent_drops_non_lifecycle_null() {
        let v = json!({"result": null, "title": "ok"});
        let out = agent(v);
        assert!(out.get("result").is_none());
    }

    #[test]
    fn agent_preserves_lifecycle_null() {
        let v = json!({"completed_at": null, "due_at": null, "title": "ok"});
        let out = agent(v);
        assert_eq!(out["completed_at"], json!(null));
        assert_eq!(out["due_at"], json!(null));
    }

    #[test]
    fn agent_preserves_relationship_null() {
        let v = json!({"parent_id": null, "superseded_by": null});
        let out = agent(v);
        assert_eq!(out["parent_id"], json!(null));
        assert_eq!(out["superseded_by"], json!(null));
    }

    #[test]
    fn agent_preserves_unknown_channel_heartbeat_nulls() {
        let v = json!({
            "channels": [{
                "poll_interval_secs": null,
                "stalled": null,
                "last_success_at": null,
                "last_poll_attempt_at": null,
                "last_failure_at": null,
                "last_error": null,
                "consecutive_failures": null,
                "quarantined_count": 1,
            }]
        });
        let out = agent(v);
        let channel = out["channels"][0].as_object().expect("channel object");
        for field in [
            "poll_interval_secs",
            "stalled",
            "last_success_at",
            "last_poll_attempt_at",
            "last_failure_at",
            "last_error",
            "consecutive_failures",
        ] {
            assert_eq!(
                channel.get(field),
                Some(&Value::Null),
                "Agent presentation must preserve unknown heartbeat fact `{field}`"
            );
        }
    }

    #[test]
    fn agent_truncates_score_field() {
        let v = json!({"score": 0.12345678});
        let out = agent(v);
        let s = out["score"].as_f64().unwrap();
        assert!((s - 0.123).abs() < 1e-9, "expected ~0.123, got {s}");
    }

    #[test]
    fn agent_presents_ranking_alias_and_nested_evidence() {
        let canonical = json!([
            {
                "rank_score": 0.0325224749,
                "score": 0.0325224749,
                "rank_score_kind": "rrf",
                "signals": {"vector_similarity": 0.842567, "keyword_score": 18.375}
            },
            {"rank_score": 0.0, "score": 0.0, "rank_score_kind": "keyword", "signals": {}}
        ]);
        for mode in [PresentationMode::Verbose, PresentationMode::Human] {
            assert_eq!(present(canonical.clone(), mode, NOW), canonical);
        }
        let shown = agent(canonical);
        assert_eq!(shown[0]["rank_score"], json!(0.0325));
        assert_eq!(shown[0]["score"], shown[0]["rank_score"]);
        assert_eq!(shown[0]["rank_score_kind"], "rrf");
        assert_eq!(shown[0]["signals"]["vector_similarity"], json!(0.843));
        assert_eq!(shown[0]["signals"]["keyword_score"], json!(18.4));
        assert_eq!(shown[1]["rank_score"], json!(0.0));
        assert_eq!(shown[1]["score"], shown[1]["rank_score"]);
        assert_eq!(shown[1]["rank_score_kind"], "keyword");
        assert!(shown[1].get("signals").is_none());
    }

    #[test]
    fn agent_renders_old_timestamp_exactly() {
        let v = json!({"created_at": "2020-01-01T10:30:45.123456Z"});
        let out = agent(v);
        assert_eq!(out["created_at"], json!("2020-01-01T10:30:45.123456Z"));
        assert!(out.get("created_at_relative").is_none());
    }

    #[test]
    fn agent_renders_recent_timestamp_exactly() {
        let ts_unix = NOW - 180;
        let ts = unix_to_iso8601(ts_unix);
        let v = json!({"updated_at": ts.clone()});
        let out = agent(v);
        assert_eq!(out["updated_at"], json!(ts));
    }

    #[test]
    fn agent_does_not_compact_top_level_trigger_at_field() {
        // Regression for #871: `schedule.remind`'s create response returns
        // `trigger_at` as a top-level convenience field (sibling to `id`,
        // `full_id`), not nested under `"properties"`. The pre-existing
        // `inside_properties` guard alone did not protect it, so Agent-mode
        // compaction rewrote it: `at` here is far outside the 24h relative
        // window, so pre-fix it would have been minute-truncated to
        // "2026-07-11T19:00", discarding the seconds and the "-04:00"
        // offset the caller needs to round-trip the exact value verbatim.
        let at = "2026-07-11T19:00:00-04:00";
        let v = json!({
            "id": "a1b2c3d4",
            "full_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
            "event_type": "remind",
            "trigger_at": at,
            "repeat": null,
            "status": "pending",
        });
        let out = agent(v);
        assert_eq!(out["trigger_at"], json!(at));
    }

    #[test]
    fn agent_does_not_compact_top_level_trigger_at_utc() {
        let at = "2026-07-11T23:00:00Z";
        let v = json!({"trigger_at": at});
        let out = agent(v);
        assert_eq!(out["trigger_at"], json!(at));
    }

    #[test]
    fn agent_does_not_compact_top_level_trigger_at_offset_less() {
        let at = "2026-07-11T23:00:00";
        let v = json!({"trigger_at": at});
        let out = agent(v);
        assert_eq!(out["trigger_at"], json!(at));
    }

    #[test]
    fn agent_still_renders_other_top_level_timestamps_alongside_trigger_at() {
        // The `trigger_at` exemption is scoped to that field name only — a
        // sibling generic timestamp field still converts to exact UTC.
        let v = json!({
            "trigger_at": "2026-07-11T19:00:00-04:00",
            "created_at": "2020-01-01T10:30:45.123456Z",
        });
        let out = agent(v);
        assert_eq!(out["trigger_at"], json!("2026-07-11T19:00:00-04:00"));
        assert_eq!(out["created_at"], json!("2020-01-01T10:30:45.123456Z"));
    }

    #[test]
    fn agent_does_not_compact_top_level_due() {
        // gtd.assign/gtd.tasks/gtd.next return the caller-supplied `due` as
        // a top-level convenience field mirroring `properties.due`; it must
        // round-trip verbatim through Agent-mode presentation, the same
        // guarantee already given to `trigger_at`.
        let due = "2026-08-01T09:30:15-04:00";
        let v = json!({"due": due});
        let out = agent(v);
        assert_eq!(out["due"], json!(due));
    }

    #[test]
    fn agent_still_protects_nested_trigger_at_under_properties() {
        // Pre-existing protection (agenda/get responses nest trigger_at
        // under "properties") must remain intact alongside the new
        // top-level, field-name-based guard.
        let at = "2026-07-11T19:00:00-04:00";
        let v = json!({
            "id": "a1b2c3d4",
            "properties": {"trigger_at": at, "status": "pending"},
        });
        let out = agent(v);
        assert_eq!(out["properties"]["trigger_at"], json!(at));
    }

    #[test]
    fn agent_recurses_into_nested_objects() {
        let v = json!({
            "items": [
                {
                    "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
                    "tags": [],
                    "score": 0.9999
                }
            ]
        });
        let out = agent(v);
        let item = &out["items"][0];
        assert_eq!(item["id"], json!("a1b2c3d4"));
        assert!(item.get("tags").is_none());
        let s = item["score"].as_f64().unwrap();
        assert!((s - 1.0).abs() < 1e-9);
    }

    // full_id must never be shortened in Agent mode: it's the caller's
    // stable chaining handle.
    #[test]
    fn agent_preserves_full_id_as_36_chars() {
        let uuid = "a1b2c3d4-e5f6-7890-abcd-ef1234567890";
        let v = json!({"id": uuid, "full_id": uuid, "title": "X"});
        let out = agent(v);
        // `id` is shortened to 8 chars
        assert_eq!(
            out["id"],
            json!("a1b2c3d4"),
            "id should be 8-char short form"
        );
        // `full_id` must remain the full 36-char UUID
        assert_eq!(
            out["full_id"].as_str().unwrap().len(),
            36,
            "full_id must be 36 chars in agent mode"
        );
        assert_eq!(
            out["full_id"],
            json!(uuid),
            "full_id must equal the original UUID"
        );
        // Verify the invariant: full_id starts with the short id prefix
        assert!(
            out["full_id"]
                .as_str()
                .unwrap()
                .starts_with(out["id"].as_str().unwrap()),
            "full_id must start with the short id prefix"
        );
    }

    #[test]
    fn is_canonical_uuid_recognizes_valid() {
        assert!(is_canonical_uuid("a1b2c3d4-e5f6-7890-abcd-ef1234567890"));
        assert!(!is_canonical_uuid("a1b2c3d4"));
        assert!(!is_canonical_uuid("not-a-uuid-at-all-here---------"));
    }

    #[test]
    fn looks_like_iso8601_recognizes_valid() {
        assert!(looks_like_iso8601("2026-05-23T16:18:15.234567Z"));
        assert!(!looks_like_iso8601("not a timestamp"));
        assert!(!looks_like_iso8601("2026-05-23"));
    }

    /// Format Unix seconds as ISO-8601 for test construction.
    fn unix_to_iso8601(unix: i64) -> String {
        let (y, mo, d, h, mi, s) = unix_to_civil(unix);
        format!("{y:04}-{mo:02}-{d:02}T{h:02}:{mi:02}:{s:02}Z")
    }

    fn unix_to_civil(unix: i64) -> (i64, i64, i64, i64, i64, i64) {
        let s = unix % 86400;
        let days = unix / 86400;
        let h = s / 3600;
        let m = (s % 3600) / 60;
        let sec = s % 60;
        // Howard Hinnant civil_from_days
        let z = days + 719468;
        let era = z.div_euclid(146097);
        let doe = z - era * 146097;
        let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
        let y = yoe + era * 400;
        let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
        let mp = (5 * doy + 2) / 153;
        let d = doy - (153 * mp + 2) / 5 + 1;
        let mo = if mp < 10 { mp + 3 } else { mp - 9 };
        let y = if mo <= 2 { y + 1 } else { y };
        (y, mo, d, h, m, sec)
    }

    #[test]
    fn agent_does_not_shorten_uuid_shaped_content_fields() {
        let uuid = "a1b2c3d4-e5f6-7890-abcd-ef1234567890";
        let out = agent(json!({
            "id": uuid,
            "full_id": uuid,
            "content": uuid,
            "description": uuid,
            "title": uuid,
            "query": uuid,
        }));

        assert_eq!(out["id"], json!("a1b2c3d4"));
        assert_eq!(out["full_id"], json!(uuid));
        assert_eq!(out["content"], json!(uuid));
        assert_eq!(out["description"], json!(uuid));
        assert_eq!(out["title"], json!(uuid));
        assert_eq!(out["query"], json!(uuid));
    }

    #[test]
    fn agent_shortens_suffix_id_fields() {
        let uuid = "a1b2c3d4-e5f6-7890-abcd-ef1234567890";
        let out = agent(json!({
            "note_id": uuid,
            "source_id": uuid,
            "target_id": uuid,
        }));

        assert_eq!(out["note_id"], json!("a1b2c3d4"));
        assert_eq!(out["source_id"], json!("a1b2c3d4"));
        assert_eq!(out["target_id"], json!("a1b2c3d4"));
    }

    #[test]
    fn agent_preserves_strict_round_trip_uuid_fields() {
        let uuid = "a1b2c3d4-e5f6-7890-abcd-ef1234567890";
        let out = agent(json!({
            "context_entity_id": uuid,
            "thread_id": uuid,
            "session_id": uuid,
            "project_id": uuid,
            "properties": {
                "context_entity_id": uuid,
                "thread_id": uuid,
                "outbound_ref": uuid,
                "parent_id": uuid,
                "session_id": uuid,
                "project_id": uuid,
            },
            "parent_id": uuid,
        }));

        assert_eq!(out["context_entity_id"], json!(uuid));
        assert_eq!(out["thread_id"], json!(uuid));
        assert_eq!(out["session_id"], json!(uuid));
        assert_eq!(out["project_id"], json!(uuid));
        assert_eq!(out["properties"]["context_entity_id"], json!(uuid));
        assert_eq!(out["properties"]["thread_id"], json!(uuid));
        assert_eq!(out["properties"]["outbound_ref"], json!(uuid));
        assert_eq!(out["properties"]["parent_id"], json!(uuid));
        assert_eq!(out["properties"]["session_id"], json!(uuid));
        assert_eq!(out["properties"]["project_id"], json!(uuid));
        assert_eq!(out["parent_id"], json!(uuid));
    }

    // ── ADR-078: OutputFormat tests ───────────────────────────────────────────

    /// (a) verbose json preserves full shape (no field dropped, no transformation).
    #[test]
    fn format_verbose_json_preserves_full_shape() {
        let v = json!({
            "full_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
            "namespace": "local",
            "properties": {"k": "v"},
            "title": "test"
        });
        let rendered = render_format(v.clone(), OutputFormat::Json, PresentationMode::Verbose);
        let parsed: Value = serde_json::from_str(&rendered).unwrap();
        // full_id must not be dropped in json mode.
        assert!(
            parsed.get("full_id").is_some(),
            "json mode must keep full_id"
        );
        // namespace must NOT be elided in json mode.
        assert_eq!(
            parsed.get("namespace").and_then(Value::as_str),
            Some("local")
        );
        // properties must NOT be deduped in json mode.
        assert!(parsed.get("properties").is_some());
    }

    /// (a-agent-json) Agent JSON applies the Machine-scope redundancy
    /// reduction: `namespace`/duplicate-`properties` elision, but `full_id`
    /// is retained — it is the caller's chaining handle, not a view drop
    /// (ADR-078 Amendment 3, corrected).
    #[test]
    fn format_agent_json_drops_redundancy() {
        let v = json!({
            "full_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
            "namespace": "local",
            "title": "test",
            "status": "next",
            "properties": {"status": "next", "additive": true}
        });
        let rendered = render_format(v, OutputFormat::Json, PresentationMode::Agent);
        let parsed: Value = serde_json::from_str(&rendered).unwrap();
        assert!(
            parsed.get("full_id").is_some(),
            "Agent JSON must keep full_id: it is the machine contract's chaining handle"
        );
        assert!(parsed.get("namespace").is_none());
        assert_eq!(parsed["status"], json!("next"));
        assert!(parsed["properties"].get("status").is_none());
        assert_eq!(parsed["properties"]["additive"], json!(true));
    }

    /// Agent JSON (Machine scope) keeps `full_id` while dropping
    /// `namespace="local"` and duplicate `properties`; Auto (View scope) on
    /// the same record still drops all three — the view scope is unchanged
    /// by Amendment 3's correction.
    #[test]
    fn agent_json_keeps_full_id_while_auto_still_drops_it() {
        let v = json!({
            "full_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
            "namespace": "local",
            "title": "test",
            "properties": {"title": "test", "additive": true}
        });

        let json_rendered = render_format(v.clone(), OutputFormat::Json, PresentationMode::Agent);
        let json_parsed: Value = serde_json::from_str(&json_rendered).unwrap();
        assert!(
            json_parsed.get("full_id").is_some(),
            "Agent JSON must keep full_id"
        );
        assert!(
            json_parsed.get("namespace").is_none(),
            "Agent JSON must elide namespace=\"local\""
        );
        assert!(
            json_parsed["properties"].get("title").is_none(),
            "Agent JSON must dedupe a duplicate properties entry"
        );
        assert_eq!(json_parsed["properties"]["additive"], json!(true));

        let auto_rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            !auto_rendered.contains("full_id"),
            "Auto (view scope) must still drop full_id: {auto_rendered}"
        );
        assert!(
            !auto_rendered.contains("\"namespace\""),
            "Auto must still elide namespace=\"local\": {auto_rendered}"
        );
    }

    /// (b1) homogeneous record array → markdown table with header + separator + rows.
    #[test]
    fn format_auto_homogeneous_array_renders_markdown_table() {
        let v = json!([
            {"id": "abc", "title": "First"},
            {"id": "def", "title": "Second"}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(rendered.starts_with('|'), "must start with |");
        assert!(
            rendered.contains("| id |") || rendered.contains("| id"),
            "must have id column"
        );
        assert!(rendered.contains("title"), "must have title column");
        assert!(rendered.contains("|---|"), "must have separator row");
        assert!(rendered.contains("abc"), "must have first row data");
        assert!(rendered.contains("Second"), "must have second row data");
    }

    /// (b2) single record → compact JSON, lossless (kv-block renderer removed).
    #[test]
    fn format_auto_single_record_renders_compact_json() {
        let v = json!({"id": "abc", "title": "Hello World"});
        let rendered = render_format(v.clone(), OutputFormat::Auto, PresentationMode::Agent);
        let parsed: Value = serde_json::from_str(&rendered).expect("must be valid JSON");
        assert_eq!(parsed, v, "single record must round-trip losslessly");
        assert!(
            !rendered.starts_with('|'),
            "single record must not be a markdown table"
        );
    }

    /// (b2-lossless) a single record with a large payload field (a compose
    /// briefing's `markdown`) arrives whole — the former kv-block renderer
    /// truncated it.
    #[test]
    fn format_auto_single_record_large_payload_survives_whole() {
        let briefing = "line one\nline two\n".repeat(500); // ~9KB, newlines included
        let v = json!({"id": "abc", "markdown": briefing.clone()});
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        let parsed: Value = serde_json::from_str(&rendered).expect("must be valid JSON");
        assert_eq!(
            parsed.get("markdown").and_then(Value::as_str),
            Some(briefing.as_str()),
            "large payload field must survive untruncated"
        );
    }

    /// Envelope siblings survive table rendering: a `query`-style page whose
    /// `has_more` is dropped reads as complete — fail-open.
    #[test]
    fn format_auto_table_preserves_sibling_scalars() {
        let v = json!({
            "results": [
                {"id": "abc", "title": "First"},
                {"id": "def", "title": "Second"}
            ],
            "has_more": true,
            "offset": 20,
            "page_size": 2,
            "truncated": false
        });
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(rendered.contains("| id"), "records must render as a table");
        assert!(
            rendered.contains("has_more: true"),
            "has_more sibling must survive: {rendered}"
        );
        assert!(
            rendered.contains("offset: 20"),
            "offset sibling must survive"
        );
        assert!(
            rendered.contains("page_size: 2"),
            "page_size sibling must survive"
        );
        assert!(
            rendered.contains("truncated: false"),
            "truncated sibling must survive"
        );
    }

    /// Nested table cells render a constant elision marker, never
    /// truncated pseudo-JSON that reads as data while missing fields.
    #[test]
    fn format_auto_nested_cell_renders_elision_marker() {
        let big_nested: Value = json!({"k": "v".repeat(300), "other": {"deep": true}});
        let v = json!([
            {"id": "abc", "properties": big_nested},
            {"id": "def", "properties": {"x": 1}}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            rendered.contains("{…}"),
            "nested object cell must render the elision marker: {rendered}"
        );
        assert!(
            !rendered.contains("..."),
            "no truncated pseudo-JSON in nested cells"
        );
    }

    /// Arrays of scalars (tags) still render as compact JSON in cells.
    #[test]
    fn format_auto_scalar_array_cell_renders_compact_json() {
        let v = json!([
            {"id": "abc", "tags": ["lesson", "khive"]},
            {"id": "def", "tags": ["adr"]}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            rendered.contains(r#"["lesson","khive"]"#),
            "scalar array cell must be compact JSON: {rendered}"
        );
    }

    /// Identity/decision columns are exempt from truncation: a truncated
    /// title cannot be selected on, a truncated signature is unusable.
    #[test]
    fn format_auto_identity_columns_not_truncated() {
        let long_title = "T".repeat(300);
        let long_note = "N".repeat(300);
        let v = json!([
            {"id": "abc", "title": long_title.clone(), "note": long_note.clone()},
            {"id": "def", "title": "short", "note": "short"}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            rendered.contains(&long_title),
            "title column must not be truncated"
        );
        assert!(
            !rendered.contains(&long_note),
            "non-exempt column must still truncate"
        );
    }

    /// Verbose presentation disables cell truncation entirely (ADR-078 §3a).
    #[test]
    fn format_auto_verbose_disables_truncation() {
        let long_note = "N".repeat(300);
        let v = json!([
            {"id": "abc", "note": long_note.clone()},
            {"id": "def", "note": "short"}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Verbose);
        assert!(
            rendered.contains(&long_note),
            "verbose must render full cell content"
        );
    }

    /// The pre-pass hoists named scalar payload fields (`trigger_at`, `due`,
    /// `status`) out of `properties` so they can surface as table columns —
    /// a scheduled event carries them only inside `properties`.
    #[test]
    fn table_path_hoists_payload_scalars_to_columns() {
        // The hoist is table-path only (ADR-078 Amendment 2): two scheduled
        // events whose trigger_at/status live inside `properties` must gain
        // top-level columns in the rendered table.
        let record = |n: u32| {
            json!({
                "id": format!("evt-{n}"),
                "properties": {
                    "trigger_at": "2026-09-01T14:00:00-04:00",
                    "status": "pending",
                    "dispatch_receipt": {"state": "succeeded"}
                }
            })
        };
        let out = render_format(
            json!([record(1), record(2)]),
            OutputFormat::Auto,
            PresentationMode::Agent,
        );
        let header = out.lines().next().expect("table header");
        assert!(
            header.contains("trigger_at") && header.contains("status"),
            "hoisted scalars must appear as table columns, got header: {header}"
        );
        assert!(
            out.contains("2026-09-01T14:00:00-04:00") && out.contains("pending"),
            "hoisted values must render in cells:\n{out}"
        );
    }

    #[test]
    fn redundancy_drop_no_longer_hoists_outside_tables() {
        // Rule-separating control for the table-scoped hoist: the §7 pre-pass
        // alone must leave the properties bag in place, so a single record's
        // compact-JSON fallback keeps its shape.
        let v = json!({
            "id": "abc",
            "properties": {
                "trigger_at": "2026-09-01T14:00:00-04:00",
                "status": "pending"
            }
        });
        let reduced = apply_redundancy_drop(v, RedundancyScope::View);
        assert!(
            reduced.get("trigger_at").is_none() && reduced.get("status").is_none(),
            "the pre-pass must not hoist; the hoist is table-path only"
        );
        let props = reduced.get("properties").expect("properties must remain");
        assert_eq!(
            props.get("status").and_then(Value::as_str),
            Some("pending"),
            "fallback shape keeps payload fields inside properties"
        );
    }

    #[test]
    fn sibling_string_with_newline_renders_as_json_literal() {
        // Escaping contract: a newline-bearing sibling string must not be able
        // to fabricate an additional `key: value` line.
        let v = json!({
            "items": [{"id": "a", "kind": "x"}, {"id": "b", "kind": "y"}],
            "note": "line one\nforged_key: forged_value",
            "has_more": true
        });
        let out = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            !out.contains("\nforged_key: forged_value"),
            "raw newline from a sibling string must not start a new line:\n{out}"
        );
        assert!(
            out.contains(r#"note: "line one\nforged_key: forged_value""#),
            "newline-bearing sibling renders as its JSON literal:\n{out}"
        );
        assert!(out.contains("has_more: true"), "siblings still preserved");
    }

    #[test]
    fn carriage_return_in_cell_collapses_like_newline() {
        // Escaping contract pin: cells collapse \r exactly like \n, so a
        // \r- or \r\n-bearing value cannot smuggle a raw line break into
        // the table body and forge row structure.
        let v = json!([
            {"id": "a", "note": "before\rafter"},
            {"id": "b", "note": "one\r\ntwo"}
        ]);
        let out = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            !out.contains('\r'),
            "no raw carriage return may survive into rendered output:\n{out:?}"
        );
        assert!(
            out.contains("before after") && out.contains("one  two"),
            "\\r and \\r\\n collapse to spaces inside cells:\n{out}"
        );
    }

    /// The hoist never overwrites an existing top-level sibling.
    #[test]
    fn redundancy_drop_hoist_does_not_overwrite_top_level() {
        let v = json!({
            "id": "abc",
            "status": "active",
            "properties": {"status": "pending"}
        });
        let reduced = apply_redundancy_drop(v, RedundancyScope::View);
        assert_eq!(
            reduced.get("status").and_then(Value::as_str),
            Some("active"),
            "existing top-level status must win"
        );
        assert_eq!(
            reduced
                .get("properties")
                .and_then(|p| p.get("status"))
                .and_then(Value::as_str),
            Some("pending"),
            "conflicting properties value must stay where it was"
        );
    }

    /// (b3) fallback: auto on heterogeneous/scalar value falls back to compact json.
    #[test]
    fn format_auto_scalar_fallback_compact_json() {
        let v = json!(42);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert_eq!(rendered, "42");
    }

    /// (c) table format forces markdown table even when shape would normally be kv.
    #[test]
    fn format_table_forces_markdown_when_array() {
        let v = json!({
            "items": [
                {"name": "A", "score": 1},
                {"name": "B", "score": 2}
            ]
        });
        let rendered = render_format(v, OutputFormat::Table, PresentationMode::Agent);
        assert!(
            rendered.contains("|"),
            "table format must produce markdown table"
        );
        assert!(rendered.contains("name"), "must have name column");
        assert!(rendered.contains("score"), "must have score column");
    }

    /// (c-fallback) table format falls back to compact json when no record array found.
    #[test]
    fn format_table_falls_back_to_json_when_no_array() {
        let v = json!({"single": "value"});
        let rendered = render_format(v, OutputFormat::Table, PresentationMode::Agent);
        // No record array → compact JSON fallback.
        let parsed: Value = serde_json::from_str(&rendered).unwrap();
        assert_eq!(parsed["single"], json!("value"));
    }

    /// (d) redundancy-drop: auto/table skipped in Verbose mode (§7).
    #[test]
    fn format_auto_verbose_skips_redundancy_drop() {
        let v = json!({
            "full_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
            "namespace": "local",
            "title": "test"
        });
        // In Verbose mode, redundancy drop must be skipped.
        // The value is a single object → compact JSON; full_id and namespace stay.
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Verbose);
        assert!(
            rendered.contains("full_id"),
            "verbose must preserve full_id"
        );
        assert!(
            rendered.contains("namespace"),
            "verbose must preserve namespace"
        );
    }

    /// Indirect check that the redundancy pre-pass doesn't corrupt an error
    /// envelope's shape; the actual ok=false bypass is enforced by
    /// `render_result`, not by this pre-pass.
    #[test]
    fn redundancy_drop_does_not_corrupt_error_shape() {
        let v = json!({"ok": false, "error": "something failed", "namespace": "local"});
        // apply_redundancy_drop is a pure value transform with no knowledge of
        // `ok`: bypassing it for error envelopes is the caller's job
        // (render_result in server.rs). This only checks the pre-pass itself
        // doesn't lose the error field.
        let reduced = apply_redundancy_drop(v.clone(), RedundancyScope::View);
        assert!(
            reduced.get("error").is_some(),
            "redundancy drop must preserve error field"
        );
        assert_eq!(
            reduced.get("ok").and_then(Value::as_bool),
            Some(false),
            "redundancy drop must preserve ok=false"
        );
    }

    /// Properties dedup removes only keys that match a top-level sibling exactly.
    #[test]
    fn redundancy_drop_properties_dedup() {
        let v = json!({
            "id": "abc",
            "title": "Same",
            "properties": {
                "title": "Same",  // duplicate → removed
                "extra": "unique" // not at top level → kept
            }
        });
        let reduced = apply_redundancy_drop(v, RedundancyScope::View);
        let props = reduced.get("properties").expect("properties must remain");
        assert!(props.get("extra").is_some(), "unique property must be kept");
        assert!(
            props.get("title").is_none(),
            "duplicate top-level property must be removed"
        );
    }

    /// Cell truncation: text > 120 chars gets `...` appended.
    #[test]
    fn cell_text_truncates_long_values() {
        let long = "X".repeat(200);
        let v = json!([
            {"col": long.clone()},
            {"col": "short"}
        ]);
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        // Cell must be truncated to ~120 chars + "..."
        assert!(
            rendered.contains("..."),
            "long cell must be truncated with ..."
        );
        assert!(
            !rendered.contains(&long),
            "full long string must not appear in table"
        );
    }

    /// Cell truncation must not panic on multi-byte UTF-8 characters.
    ///
    /// A string of 119 ASCII bytes followed by a 3-byte CJK character and more
    /// text has `len() > 120` but byte index 120 falls inside the CJK char.
    /// The old byte-slice truncation would panic; char-boundary truncation is safe.
    #[test]
    fn cell_text_truncation_is_utf8_safe() {
        // 119 ASCII 'a' bytes, then CJK char U+4E2D (3 bytes each), then more text.
        // Total byte length: 119 + 3 * 10 + 5 > 120, but byte 120 is inside a CJK char.
        let prefix = "a".repeat(119);
        let suffix = "中".repeat(10); // each '中' is 3 bytes
        let long_multibyte = format!("{prefix}{suffix}trailing");
        let v = json!([
            {"col": long_multibyte.clone()},
            {"col": "ok"}
        ]);
        // Must not panic — this was the bug.
        let rendered = render_format(v, OutputFormat::Auto, PresentationMode::Agent);
        assert!(
            rendered.contains("..."),
            "multibyte cell must be truncated with ..."
        );
        // The rendered string must be valid UTF-8 (no partial char slicing).
        assert!(
            std::str::from_utf8(rendered.as_bytes()).is_ok(),
            "rendered output must be valid UTF-8"
        );
    }

    // --- parse_iso8601_unix / relative-time offset handling ---

    #[test]
    fn parse_iso8601_unix_negative_offset_matches_equivalent_utc() {
        // "-04:00" is 4 hours behind UTC, so 11:55 local == 15:55Z.
        assert_eq!(
            parse_iso8601_unix("2026-07-09T11:55:00-04:00"),
            parse_iso8601_unix("2026-07-09T15:55:00Z")
        );
    }

    #[test]
    fn parse_iso8601_unix_positive_offset_matches_equivalent_utc() {
        // "+04:00" is 4 hours ahead of UTC, so 20:15 local == 16:15Z.
        assert_eq!(
            parse_iso8601_unix("2026-05-23T20:15:00+04:00"),
            parse_iso8601_unix("2026-05-23T16:15:00Z")
        );
    }

    #[test]
    fn parse_iso8601_unix_zero_offset_matches_z() {
        assert_eq!(
            parse_iso8601_unix("2026-07-09T15:55:00+00:00"),
            parse_iso8601_unix("2026-07-09T15:55:00Z")
        );
    }

    #[test]
    fn parse_iso8601_unix_compact_offset_form_matches_colon_form() {
        assert_eq!(
            parse_iso8601_unix("2026-07-09T11:55:00-0400"),
            parse_iso8601_unix("2026-07-09T11:55:00-04:00")
        );
    }

    #[test]
    fn parse_iso8601_unix_fractional_seconds_with_offset() {
        // Fractional seconds are dropped (whole-second precision only) but
        // must not prevent the trailing offset from being applied.
        assert_eq!(
            parse_iso8601_unix("2026-07-09T11:55:00.123-04:00"),
            parse_iso8601_unix("2026-07-09T15:55:00Z")
        );
    }

    #[test]
    fn parse_iso8601_unix_fractional_seconds_with_z() {
        assert_eq!(
            parse_iso8601_unix("2026-07-09T15:55:00.999Z"),
            parse_iso8601_unix("2026-07-09T15:55:00Z")
        );
    }

    #[test]
    fn parse_iso8601_unix_rejects_bare_form() {
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00"), None);
    }

    #[test]
    fn parse_iso8601_unix_malformed_tail_returns_none() {
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00X"), None);
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00+04"), None);
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00."), None);
    }

    #[test]
    fn parse_iso8601_unix_out_of_range_offset_returns_none() {
        // Hour out of range (>23), colon and compact forms.
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00+24:00"), None);
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00+2400"), None);
        // Minute out of range (>59), colon and compact forms.
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00+01:60"), None);
        assert_eq!(parse_iso8601_unix("2026-07-09T15:55:00+0160"), None);
    }

    #[test]
    fn parse_iso8601_unix_max_valid_offset_boundary_is_accepted() {
        // +23:59 / -23:59 are the largest valid offsets and must still parse.
        assert!(parse_iso8601_unix("2026-07-09T15:55:00+23:59").is_some());
        assert!(parse_iso8601_unix("2026-07-09T15:55:00-23:59").is_some());
        assert!(parse_iso8601_unix("2026-07-09T15:55:00+2359").is_some());
    }

    #[test]
    fn exact_timestamp_converts_future_offset_without_relative_form() {
        let out = exact_timestamp("2025-05-23T16:08:00-02:00").unwrap();
        assert_eq!(out.0, "2025-05-23T18:08:00Z");
        assert!(out.1 > NOW);
    }

    #[test]
    fn exact_timestamp_converts_past_offset_and_retains_fraction() {
        let out = exact_timestamp("2025-05-23T20:05:00.123+04:00").unwrap();
        assert_eq!(out.0, "2025-05-23T16:05:00.123Z");
        assert_eq!(out.1, NOW - 180);
    }
}

#[cfg(test)]
mod stream_presentation_tests {
    use super::*;
    use serde_json::json;

    #[test]
    fn stream_agent_json_preserves_opaque_record_and_empty_page() {
        let record = json!([{"id": "aabbccdd-1234-4321-1234-abcdefabcdef", "score": 0.123456789, "created_at": "2026-09-08T00:00:00.123456Z", "empty": [], "null": null, "namespace": "local", "properties": {"namespace": "local"}}]);
        for payload in [record, Value::Null, json!([]), json!({}), json!("")] {
            let page = json!({"entries": [{"seq": 1, "id": "aabbccdd-1234-4321-1234-abcdefabcdef", "created_at": "2026-09-08T00:00:00.123456Z", "record": payload}], "head_seq": 1, "next_after": null});
            let presented = present(page, PresentationMode::Agent, 0);
            let out = prepare_format_value(presented, OutputFormat::Json, PresentationMode::Agent);
            assert_eq!(out["entries"][0].get("record"), Some(&payload));
            assert!(out.get("next_after").is_some_and(Value::is_null));
        }
        let empty = json!({"entries": [], "head_seq": 0, "next_after": null});
        assert_eq!(present(empty.clone(), PresentationMode::Agent, 0), empty);
    }
}

#[cfg(test)]
mod issue_2537_standard_tests {
    use super::*;
    use serde_json::json;

    #[test]
    fn issue_2537_standard_context_baseline_controls() {
        let timestamp = "2026-01-01T00:00:00.123456Z";
        let now = 1_767_225_780; // 2026-01-01T00:03:00Z, independently literal clock.
        let uuid = "aabbccdd-1234-4321-1234-abcdefabcdef";
        let payload = json!({"id":uuid,"created_at":timestamp,"empty":[],"null":null});
        let value = json!({"tool":"stream.batch","policy":"StreamBatchReceipts","id":uuid,
            "updated_at":timestamp,"score":0.123456,"empty":[],"null":null,
            "results":[{"id":uuid,"version":1,"updated_at":timestamp,"details":{"updated_at":timestamp}}],
            "properties":{"created_at":timestamp,"id":uuid,"empty":""},"trigger_at":timestamp,"due":timestamp,
            "entry":{"seq":1,"id":uuid,"created_at":timestamp,"record":payload},
            "cursor":{"head_seq":0,"entries":[],"next_after":null}});
        let shown = present(value.clone(), PresentationMode::Agent, now);
        assert_eq!(shown["updated_at"], timestamp);
        assert_eq!(shown["results"][0]["updated_at"], timestamp);
        assert_eq!(shown["results"][0]["details"]["updated_at"], timestamp);
        assert_eq!(shown["id"], "aabbccdd");
        assert_eq!(shown["score"], json!(0.123));
        assert!(shown.get("empty").is_none());
        assert!(shown.get("null").is_none());
        assert_eq!(
            shown["properties"],
            json!({"created_at":timestamp,"id":"aabbccdd","empty":""})
        );
        assert_eq!(shown["trigger_at"], timestamp);
        assert_eq!(shown["due"], timestamp);
        assert_eq!(shown["entry"]["record"], payload);
        assert_eq!(shown["entry"]["created_at"], timestamp);
        assert_eq!(shown["cursor"], value["cursor"]);
        for mode in [PresentationMode::Verbose, PresentationMode::Human] {
            assert_eq!(present(value.clone(), mode, now), value);
        }
        assert_eq!(
            present(
                json!({"properties":timestamp}),
                PresentationMode::Agent,
                now
            )["properties"],
            timestamp
        );
        assert_eq!(
            present(
                json!({"properties":[timestamp,{"created_at":timestamp}]}),
                PresentationMode::Agent,
                now
            )["properties"],
            json!([timestamp,{"created_at":timestamp}])
        );
    }
}

#[cfg(test)]
mod issue_2537_receipt_policy_tests {
    use super::*;
    use serde_json::json;

    const TIMESTAMP: &str = "2026-01-01T00:00:00.123456Z";
    const NOW: i64 = 1_767_225_780;
    const UUID: &str = "aabbccdd-1234-4321-1234-abcdefabcdef";

    #[test]
    fn issue_2537_receipt_policies_preserve_only_the_named_fields() {
        let append = json!({
            "id": UUID, "created_at": TIMESTAMP, "updated_at": TIMESTAMP,
            "score": 0.123456, "empty": [], "null": null,
            "details": {"created_at": TIMESTAMP},
            "ticker": {"last_tick_at": TIMESTAMP},
        });
        let batch = json!({
            "id": UUID, "created_at": TIMESTAMP, "updated_at": TIMESTAMP,
            "results": [{
                "id": UUID, "created_at": TIMESTAMP, "updated_at": TIMESTAMP,
                "details": {"created_at": TIMESTAMP, "updated_at": TIMESTAMP},
                "record": {"updated_at": TIMESTAMP},
                "score": 0.123456, "empty": [], "null": null,
            }],
            "properties": {"created_at": TIMESTAMP, "id": UUID, "empty": ""},
            "entry": {"seq": 1, "id": UUID, "created_at": TIMESTAMP,
                "record": {"id": UUID, "updated_at": TIMESTAMP, "empty": [], "null": null}},
            "trigger_at": TIMESTAMP, "due": TIMESTAMP,
            "ticker": {"last_tick_at": TIMESTAMP},
        });
        for (value, policy) in [
            (append, VerbPresentationPolicy::StreamAppendReceipt),
            (batch, VerbPresentationPolicy::StreamBatchReceipts),
        ] {
            let mut expected = present(value.clone(), PresentationMode::Agent, NOW);
            assert_eq!(expected["created_at"], TIMESTAMP);
            assert_eq!(expected["updated_at"], TIMESTAMP);
            assert_eq!(expected["id"], "aabbccdd");
            assert_eq!(expected["ticker"]["last_tick_at"], TIMESTAMP);
            if policy == VerbPresentationPolicy::StreamAppendReceipt {
                expected["created_at"] = json!(TIMESTAMP);
            } else {
                expected["results"][0]["created_at"] = json!(TIMESTAMP);
                expected["results"][0]["updated_at"] = json!(TIMESTAMP);
                expected["results"][0]
                    .as_object_mut()
                    .unwrap()
                    .remove("created_at_relative");
            }
            assert_eq!(
                present_with_policy(value.clone(), PresentationMode::Agent, NOW, policy),
                expected
            );
            for mode in [PresentationMode::Verbose, PresentationMode::Human] {
                assert_eq!(present_with_policy(value.clone(), mode, NOW, policy), value);
            }
            assert_eq!(
                present_with_policy(
                    value.clone(),
                    PresentationMode::Agent,
                    NOW,
                    VerbPresentationPolicy::AlwaysVerbose
                ),
                value
            );
        }
    }

    #[test]
    fn issue_2537_receipt_paths_do_not_match_other_containers_or_descendants() {
        let row = json!({"created_at": TIMESTAMP, "updated_at": TIMESTAMP});
        for (policy, cases) in [
            (
                VerbPresentationPolicy::StreamAppendReceipt,
                vec![
                    json!([row.clone()]),
                    json!({"details": row.clone()}),
                    json!({"results": [row.clone()]}),
                    json!({"created_at": {"created_at": TIMESTAMP}}),
                ],
            ),
            (
                VerbPresentationPolicy::StreamBatchReceipts,
                vec![
                    json!([{"results": [row.clone()]}]),
                    json!({"results": row.clone()}),
                    json!({"results": [[row.clone()]]}),
                    json!({"details": {"results": [row.clone()]}}),
                    json!({"results": [{"details": row.clone(), "record": row.clone(), "results": [row.clone()]}]}),
                    json!({"results": [{"created_at": {"updated_at": TIMESTAMP}, "updated_at": null}]}),
                ],
            ),
        ] {
            for value in cases {
                assert_eq!(
                    present_with_policy(value.clone(), PresentationMode::Agent, NOW, policy),
                    present(value.clone(), PresentationMode::Agent, NOW),
                    "container must not acquire receipt protection: {value}"
                );
            }
        }
    }

    #[test]
    fn issue_2537_receipt_strings_are_preserved_without_parsing() {
        for text in ["", "not a timestamp", "2026-01-01T05:30:00.123456+05:30"] {
            let append = json!({"created_at": text});
            assert_eq!(
                present_with_policy(
                    append.clone(),
                    PresentationMode::Agent,
                    NOW,
                    VerbPresentationPolicy::StreamAppendReceipt
                ),
                append
            );
            let batch = json!({"results": [{"created_at": text, "updated_at": text}]});
            assert_eq!(
                present_with_policy(
                    batch.clone(),
                    PresentationMode::Agent,
                    NOW,
                    VerbPresentationPolicy::StreamBatchReceipts
                ),
                batch
            );
        }
        for non_string in [Value::Null, json!([]), json!({}), json!(42), json!(true)] {
            for (value, policy) in [
                (
                    json!({"created_at": non_string}),
                    VerbPresentationPolicy::StreamAppendReceipt,
                ),
                (
                    json!({"results": [{"created_at": non_string, "updated_at": non_string}]}),
                    VerbPresentationPolicy::StreamBatchReceipts,
                ),
            ] {
                assert_eq!(
                    present_with_policy(value.clone(), PresentationMode::Agent, NOW, policy),
                    present(value, PresentationMode::Agent, NOW)
                );
            }
        }
    }
}

#[cfg(test)]
mod parsed_note_content_tests {
    use super::*;
    use serde_json::json;

    #[test]
    fn issue2757_content_is_opaque_to_metadata_and_format_reductions() {
        let payload = json!([
            {"id":"11111111-1111-4111-8111-111111111111", "full_id":"keep", "namespace":"local",
             "created_at":"2026-09-15T12:34:56.123456Z", "score":0.123456789,
             "nil":null, "empty":"", "array":[], "object":{},
             "properties":{"id":"11111111-1111-4111-8111-111111111111"}},
            {"status":"pending"}
        ]);
        for (scope, response, pointer) in [
            (
                NoteContentScope::Record,
                json!({"id":"22222222-2222-4222-8222-222222222222", "content":payload}),
                "/content",
            ),
            (
                NoteContentScope::Items,
                json!({"items":[{"id":"22222222-2222-4222-8222-222222222222", "content":payload}], "requested_limit":1, "effective_limit":1, "limit_clamped":false}),
                "/items/0/content",
            ),
            (
                NoteContentScope::Notes,
                json!({"notes":[{"id":"22222222-2222-4222-8222-222222222222", "content":payload}], "next_after":null}),
                "/notes/0/content",
            ),
        ] {
            let presented =
                scope.protect(response, |value| present(value, PresentationMode::Agent, 0));
            for format in [OutputFormat::Json, OutputFormat::Auto, OutputFormat::Table] {
                let rendered = render_format_with_note_content(
                    presented.clone(),
                    format,
                    PresentationMode::Agent,
                    scope,
                );
                let actual: Value = serde_json::from_str(&rendered)
                    .expect("single note stays a JSON record, never a table of its body");
                let expected = if format == OutputFormat::Table {
                    Value::String(payload.to_string())
                } else {
                    payload.clone()
                };
                assert_eq!(actual.pointer(pointer), Some(&expected));
            }
        }
    }
}

#[cfg(test)]
mod adr045_amendment9_tests {
    use super::*;
    use serde_json::json;

    const NOW: i64 = 1_748_016_480; // 2025-05-23T16:08:00Z

    #[test]
    fn agent_exact_utc_preserves_fraction_digits_and_instant() {
        for (utc_clock, plus_clock, minus_clock) in [
            (
                "2025-05-23T16:05:00",
                "2025-05-23T20:05:00",
                "2025-05-23T12:05:00",
            ),
            (
                "2020-01-01T10:30:45",
                "2020-01-01T14:30:45",
                "2020-01-01T06:30:45",
            ),
        ] {
            for fraction in ["", ".123", ".123456"] {
                let expected = format!("{utc_clock}{fraction}Z");
                for (clock, offset) in [
                    (utc_clock, "Z"),
                    (utc_clock, "+00:00"),
                    (plus_clock, "+0400"),
                    (minus_clock, "-04:00"),
                ] {
                    let input = format!("{clock}{fraction}{offset}");
                    let shown = present(
                        json!({"updated_at": input.clone()}),
                        PresentationMode::Agent,
                        NOW,
                    );
                    assert_eq!(shown["updated_at"], expected, "{input}");
                    assert_eq!(
                        parse_iso8601_unix(&input),
                        parse_iso8601_unix(&expected),
                        "{input}"
                    );
                }
            }
        }
    }

    #[test]
    fn agent_preserves_timestamp_prefix_body() {
        let body = "2025-05-23T16:05:00Z followed by ordinary message text";
        let shown = present(json!({"content": body}), PresentationMode::Agent, NOW);
        assert_eq!(shown["content"], body);
    }

    #[test]
    fn agent_preserves_offsetless_timestamp() {
        let body = "2025-05-23T16:05:00";
        let shown = present(json!({"content": body}), PresentationMode::Agent, NOW);
        assert_eq!(shown["content"], body);
    }

    #[test]
    fn agent_preserves_malformed_offset() {
        let body = "2025-05-23T16:05:00+25:00";
        let shown = present(json!({"content": body}), PresentationMode::Agent, NOW);
        assert_eq!(shown["content"], body);
    }

    #[test]
    fn agent_list_rows_pair_exact_and_relative_time_in_each_band() {
        let bands = [
            (42, "42s ago"),
            (180, "3m ago"),
            (3 * 3600, "3h ago"),
            (2 * 86400, "2d ago"),
        ];
        let rows: Vec<Value> = bands
            .into_iter()
            .map(|(age, _)| {
                let created = chrono::DateTime::<chrono::Utc>::from_timestamp(NOW - age, 0)
                    .unwrap()
                    .to_rfc3339_opts(chrono::SecondsFormat::Secs, true);
                json!({"created_at": created, "updated_at": created})
            })
            .collect();
        let shown = present(json!({"items": rows.clone()}), PresentationMode::Agent, NOW);
        for (index, (_, relative)) in bands.into_iter().enumerate() {
            assert_eq!(
                shown["items"][index]["created_at"],
                rows[index]["created_at"]
            );
            assert_eq!(
                shown["items"][index]["updated_at"],
                rows[index]["updated_at"]
            );
            assert_eq!(shown["items"][index]["created_at_relative"], relative);
            assert!(shown["items"][index].get("updated_at_relative").is_none());
        }
    }

    #[test]
    fn agent_relative_sibling_obeys_array_properties_existing_and_future_bounds() {
        let recent = "2025-05-23T16:05:00+00:00";
        let future = "2025-05-23T16:08:10Z";
        let shown = present(
            json!({
                "created_at": recent,
                "items": [
                    {"created_at": future},
                    {"created_at": recent, "created_at_relative": "canonical"},
                    {"created_at": "2025-05-23T16:05:00"},
                    {"updated_at": recent},
                    {"created_at": "2025-05-23T16:08:00.000001Z"},
                    {"created_at": "2025-05-23T16:07:59.999999Z"},
                    {"created_at": "2025-05-23T16:08:00.000000Z"},
                    {"properties": [{"created_at": recent, "empty": ""}]}
                ],
                "properties": {"nested": [{"created_at": recent}]}
            }),
            PresentationMode::Agent,
            NOW,
        );
        assert_eq!(shown["created_at"], "2025-05-23T16:05:00Z");
        assert!(shown.get("created_at_relative").is_none());
        assert_eq!(shown["items"][0]["created_at"], future);
        assert!(shown["items"][0].get("created_at_relative").is_none());
        assert_eq!(shown["items"][1]["created_at_relative"], "canonical");
        assert_eq!(shown["items"][2]["created_at"], "2025-05-23T16:05:00");
        assert!(shown["items"][2].get("created_at_relative").is_none());
        assert!(shown["items"][3].get("created_at_relative").is_none());
        assert!(shown["items"][4].get("created_at_relative").is_none());
        assert_eq!(shown["items"][5]["created_at_relative"], "0s ago");
        assert_eq!(shown["items"][6]["created_at_relative"], "0s ago");
        assert_eq!(shown["items"][7]["properties"][0]["created_at"], recent);
        assert!(shown["items"][7]["properties"][0]
            .get("created_at_relative")
            .is_none());
        assert!(shown["items"][7]["properties"][0].get("empty").is_none());
        assert_eq!(shown["properties"]["nested"][0]["created_at"], recent);
        assert!(shown["properties"]["nested"][0]
            .get("created_at_relative")
            .is_none());
    }

    #[test]
    fn agent_relative_sibling_uses_sampled_fraction_within_same_second() {
        let sampled = chrono::DateTime::parse_from_rfc3339("2025-05-23T16:08:00.500000000Z")
            .unwrap()
            .with_timezone(&chrono::Utc);
        let shown = present_with_policy_at(
            json!({"items": [
                {"created_at": "2025-05-23T16:08:00.499999999Z"},
                {"created_at": "2025-05-23T16:08:00.500000000Z"},
                {"created_at": "2025-05-23T16:08:00.5000000000Z"},
                {"created_at": "2025-05-23T16:08:00.5000000001Z"},
                {"created_at": "2025-05-23T16:08:00.500000001Z"},
                {"created_at": "2025-05-23T16:07:59.500000001Z"},
                {"created_at": "2025-05-23T16:07:59.500000000Z"}
            ]}),
            PresentationMode::Agent,
            sampled.into(),
            VerbPresentationPolicy::Standard,
        );
        for index in [0, 1, 2, 5] {
            assert_eq!(shown["items"][index]["created_at_relative"], "0s ago");
        }
        for index in [3, 4] {
            assert!(shown["items"][index].get("created_at_relative").is_none());
        }
        assert_eq!(shown["items"][6]["created_at_relative"], "1s ago");
    }
}