polyc_agent/

question.rs

//! `ask_question` (#1660): parse/validate the model's clarifying-question
//! batch, and the pure types the turn loop's question-pause phase builds and
//! consumes.
//!
//! This is a **sibling pause path to the tool-approval gate, not a reuse of
//! it** — see issue #1660 and its parent PRD #1659. This module owns only
//! the parse/validate half (invariant I5: a malformed call is rejected back
//! to the model as a tool-call error and never reaches a pause or an
//! event-log write); the pause/resume machinery that consumes
//! [`QuestionItem`] (a pending-question record, the turn result's own
//! pending-questions list) lands in a later slice of this same issue.
//!
//! # Why the tool name is duplicated here rather than imported
//!
//! `polyc_tools` already depends on `polyc_agent` (for
//! [`crate::ToolExecutor`]), so this crate cannot depend back on
//! `polyc_tools` without a cycle. [`ASK_QUESTION_TOOL_NAME`] is therefore the
//! same literal as `polyc_tools::ask_question::TOOL_NAME`, duplicated
//! deliberately — the same reasoning `polyc_proto`'s `INVITE_TOOL_NAME`
//! duplication already documents. A cross-crate test in `polyc-tools` pins
//! the two literals equal.

use serde_json::Value;

/// The `ask_question` tool name the turn loop recognizes to trigger the
/// question-pause phase.
///
/// Kept in sync with `polyc_tools::ask_question::TOOL_NAME` by a cross-crate
/// test in that crate (see the module doc for why it's not imported
/// directly).
pub const ASK_QUESTION_TOOL_NAME: &str = "ask_question";

/// Maximum number of questions in a single `ask_question` call. Kept in sync
/// with `polyc_tools::ask_question::MAX_QUESTIONS_PER_CALL`.
pub const MAX_QUESTIONS_PER_CALL: usize = 3;

/// Minimum number of options a question may offer. Kept in sync with
/// `polyc_tools::ask_question::MIN_OPTIONS`.
pub const MIN_OPTIONS: usize = 2;

/// Maximum number of options a question may offer. Kept in sync with
/// `polyc_tools::ask_question::MAX_OPTIONS`.
pub const MAX_OPTIONS: usize = 4;

/// Maximum length (in characters) of a question's `header`. Kept in sync with
/// `polyc_tools::ask_question::MAX_HEADER_CHARS`.
pub const MAX_HEADER_CHARS: usize = 60;

/// Maximum length (in characters) of an option's `label`. Kept in sync with
/// `polyc_tools::ask_question::MAX_OPTION_LABEL_CHARS`.
pub const MAX_OPTION_LABEL_CHARS: usize = 48;

/// Maximum length (in characters) of a one-sentence field (`question` or an
/// option's `description`). Kept in sync with
/// `polyc_tools::ask_question::MAX_SENTENCE_CHARS`.
pub const MAX_SENTENCE_CHARS: usize = 200;

const ARG_QUESTIONS: &str = "questions";
const ARG_HEADER: &str = "header";
const ARG_QUESTION: &str = "question";
const ARG_OPTIONS: &str = "options";
const ARG_LABEL: &str = "label";
const ARG_DESCRIPTION: &str = "description";
const ARG_RECOMMENDED: &str = "recommended";

/// One option a question offers: a short label and its one-sentence
/// consequence. At most one option per [`QuestionItem`] is `recommended`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct QuestionOption {
    /// A few words naming this option.
    pub label: String,
    /// The one-sentence consequence of picking this option.
    pub description: String,
    /// Whether this is the model's recommendation (at most one per question).
    pub recommended: bool,
}

/// One clarifying question: a short header, a one-sentence prompt, and 2-4
/// mutually exclusive [`QuestionOption`]s.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct QuestionItem {
    /// A short label (fits a chat-surface button-row heading).
    pub header: String,
    /// The one-sentence question to ask.
    pub question: String,
    /// 2-4 mutually exclusive options.
    pub options: Vec<QuestionOption>,
}

/// One question from an `ask_question` call, paused and awaiting an answer.
///
/// Identity is `(call_id, index)` (`#1660`): one `ask_question` call carries
/// 1-3 questions, each individually answerable, so `index` is the question's
/// position WITHIN the call's own `questions` array — never a batch-wide
/// counter across multiple `ask_question` calls in the same turn.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PendingQuestion {
    /// Provider-assigned tool-call id of the `ask_question` call this
    /// question came from. Shared by every [`PendingQuestion`] the same call
    /// produced.
    pub call_id: String,
    /// This question's position within its call's `questions` array
    /// (0-based).
    pub index: u32,
    /// The question itself: header, prompt, and options.
    pub item: QuestionItem,
    /// The raw `ask_question` call's full arguments JSON (every question in
    /// the call, not just this one) — the audit binding a later signed
    /// answer must match against, mirroring `PendingApproval::args_json`.
    pub args_json: String,
}

/// A validation failure from [`parse_ask_question_args`] (invariant I5).
///
/// The `Display` text IS the reader-facing sentence — fed back to the model
/// verbatim as the tool call's own `{"error": ...}` result. This is a typed
/// wrapper over that message, not a bare `String`
/// (`thiserror` in libraries), but it changes nothing about what the model
/// sees: `Display` renders the wrapped text byte-for-byte, the same shape
/// `polyc_query::ScopedQueryError::Rejected`/`SourceBudgetExceeded` already
/// use for a pre-rendered, safe message with no further variants to
/// distinguish programmatically.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
#[error("{0}")]
pub struct QuestionArgsError(String);

impl QuestionArgsError {
    fn new(message: impl Into<String>) -> Self {
        Self(message.into())
    }
}

/// Parses and validates one `ask_question` call's arguments (invariant I5).
///
/// Rejects: malformed JSON; a `questions` array of 0 or more than
/// [`MAX_QUESTIONS_PER_CALL`]; a question missing `header`/`question`/
/// `options`; a `header` over [`MAX_HEADER_CHARS`]; a `question` or option
/// `description` over [`MAX_SENTENCE_CHARS`]; an `options` array with fewer
/// than [`MIN_OPTIONS`] or more than [`MAX_OPTIONS`] entries; an option with
/// an empty or missing `label`/`description`, or a `label` over
/// [`MAX_OPTION_LABEL_CHARS`]; more than one option marked `recommended` on
/// the same question.
///
/// # Errors
///
/// Returns a complete, reader-facing sentence — fed back to the model
/// verbatim as the tool call's own `{"error": ...}` result, never a pause
/// and never an event-log write (I5) — describing exactly what was wrong.
pub fn parse_ask_question_args(args_json: &str) -> Result<Vec<QuestionItem>, QuestionArgsError> {
    let value: Value = serde_json::from_str(args_json)
        .map_err(|_| QuestionArgsError::new("That ask_question call did not parse as JSON."))?;
    let questions = value
        .get(ARG_QUESTIONS)
        .and_then(Value::as_array)
        .ok_or_else(|| QuestionArgsError::new("ask_question needs a \"questions\" array."))?;

    if questions.is_empty() {
        return Err(QuestionArgsError::new(
            "ask_question needs at least 1 question, got 0.",
        ));
    }
    if questions.len() > MAX_QUESTIONS_PER_CALL {
        return Err(QuestionArgsError::new(format!(
            "ask_question allows at most {MAX_QUESTIONS_PER_CALL} questions per call, got {}.",
            questions.len()
        )));
    }

    questions.iter().map(parse_question_item).collect()
}

/// Parses and validates one entry of the `questions` array.
fn parse_question_item(v: &Value) -> Result<QuestionItem, QuestionArgsError> {
    let header = required_str(v, ARG_HEADER, "header")?;
    if header.chars().count() > MAX_HEADER_CHARS {
        return Err(QuestionArgsError::new(format!(
            "A question's header must be at most {MAX_HEADER_CHARS} characters."
        )));
    }
    let question = required_str(v, ARG_QUESTION, "question")?;
    if question.chars().count() > MAX_SENTENCE_CHARS {
        return Err(QuestionArgsError::new(format!(
            "A question must be at most {MAX_SENTENCE_CHARS} characters."
        )));
    }

    let options_v = v
        .get(ARG_OPTIONS)
        .and_then(Value::as_array)
        .ok_or_else(|| QuestionArgsError::new("Each question needs an \"options\" array."))?;
    if options_v.len() < MIN_OPTIONS || options_v.len() > MAX_OPTIONS {
        return Err(QuestionArgsError::new(format!(
            "Each question needs between {MIN_OPTIONS} and {MAX_OPTIONS} options, got {}.",
            options_v.len()
        )));
    }

    let mut options = Vec::with_capacity(options_v.len());
    let mut recommended_count = 0usize;
    for o in options_v {
        let label = required_str(o, ARG_LABEL, "label")?;
        if label.chars().count() > MAX_OPTION_LABEL_CHARS {
            return Err(QuestionArgsError::new(format!(
                "An option's label must be at most {MAX_OPTION_LABEL_CHARS} characters."
            )));
        }
        let description = required_str(o, ARG_DESCRIPTION, "description")?;
        if description.chars().count() > MAX_SENTENCE_CHARS {
            return Err(QuestionArgsError::new(format!(
                "An option's description must be at most {MAX_SENTENCE_CHARS} characters."
            )));
        }
        let recommended = o
            .get(ARG_RECOMMENDED)
            .and_then(Value::as_bool)
            .unwrap_or(false);
        if recommended {
            recommended_count += 1;
        }
        options.push(QuestionOption {
            label,
            description,
            recommended,
        });
    }
    if recommended_count > 1 {
        return Err(QuestionArgsError::new(
            "A question may mark at most one option recommended.",
        ));
    }

    Ok(QuestionItem {
        header,
        question,
        options,
    })
}

/// Reads a required, non-empty string field from a JSON object, or a
/// complete reader-facing sentence naming what's missing/empty.
fn required_str(v: &Value, key: &str, human: &str) -> Result<String, QuestionArgsError> {
    let s = v
        .get(key)
        .and_then(Value::as_str)
        .ok_or_else(|| QuestionArgsError::new(format!("ask_question is missing a {human}.")))?;
    if s.trim().is_empty() {
        return Err(QuestionArgsError::new(format!(
            "ask_question's {human} can't be empty."
        )));
    }
    Ok(s.to_owned())
}

/// A resolved answer's state (invariant I4: three states, pairwise
/// distinguishable in the tool result).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AnswerState {
    /// A human picked one of the offered options.
    Answered,
    /// A human explicitly declined to choose — "use your own judgment" —
    /// distinct from [`Self::Answered`] so the agent never mistakes a
    /// decline for a real answer.
    Declined,
    /// Nobody answered before the idle window elapsed; the control plane
    /// auto-resolved to the recommended option (or the first option if none
    /// was marked). Distinct from both other states so the agent is told
    /// explicitly this was an assumption, not a genuine human answer.
    AutoResolved,
}

/// `s` did not match any of `polyc_crypto::question`'s three signed state
/// strings.
#[derive(Debug, Clone, thiserror::Error)]
#[error("unrecognized question-answer state {0:?}")]
pub struct UnrecognizedAnswerState(String);

/// The ONE place the wire/persisted `state` string (`polyc_crypto::question`'s
/// `ANSWERED_STATE`/`DECLINED_STATE`/`AUTO_RESOLVED_STATE` consts — the proto
/// field itself stays a plain string; only its Rust-side conversion is
/// centralized here) converts to and from [`AnswerState`]. Every reader that
/// decodes a signed answer's `state` — `harness_dialer.rs`'s
/// `From<&QuestionAnswerRecord>` and `polyc_turn_runner::verify_question_answers`
/// — calls this instead of re-deriving its own if/else chain.
impl std::str::FromStr for AnswerState {
    type Err = UnrecognizedAnswerState;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s == polyc_crypto::question::ANSWERED_STATE {
            Ok(Self::Answered)
        } else if s == polyc_crypto::question::DECLINED_STATE {
            Ok(Self::Declined)
        } else if s == polyc_crypto::question::AUTO_RESOLVED_STATE {
            Ok(Self::AutoResolved)
        } else {
            Err(UnrecognizedAnswerState(s.to_owned()))
        }
    }
}

/// The reverse of `AnswerState`'s `FromStr` impl above — the exact
/// wire/persisted state string this state signs as.
impl From<AnswerState> for String {
    fn from(state: AnswerState) -> Self {
        match state {
            AnswerState::Answered => polyc_crypto::question::ANSWERED_STATE,
            AnswerState::Declined => polyc_crypto::question::DECLINED_STATE,
            AnswerState::AutoResolved => polyc_crypto::question::AUTO_RESOLVED_STATE,
        }
        .to_owned()
    }
}

/// A verified, signature-checked answer to one pending question.
///
/// The harness-side counterpart of
/// `polyc_crypto::question::VerifiedQuestionAnswer`, carrying only what the
/// turn loop needs to build the tool result (never the raw signature bytes;
/// those stay in the crypto/wire layers).
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct VerifiedAnswer {
    /// The `ask_question` call id this answer resolves.
    pub call_id: String,
    /// This answer's question index within its call's `questions` array.
    pub index: u32,
    /// The resolved state.
    pub state: AnswerState,
    /// The chosen option's index, when [`AnswerState::Answered`] or
    /// [`AnswerState::AutoResolved`]. `None` for a decline.
    pub selected_index: Option<u32>,
    /// The chosen option's label, mirrored alongside the index. Empty for a
    /// decline.
    pub selected_label: String,
    /// Who answered — empty for [`AnswerState::AutoResolved`] (nobody did).
    pub answered_by: String,
}

/// The reader-facing note appended to a declined question's result — the
/// single source for this sentence so it can never read differently between
/// the turn-loop result payload and (later) any edge-facing copy.
const DECLINED_NOTE: &str =
    "The user explicitly declined to choose — use your own judgment and proceed.";

/// The reader-facing note appended to an auto-resolved question's result.
const AUTO_RESOLVED_NOTE: &str = "Nobody answered before the idle window elapsed, so this was \
    auto-resolved to the recommended option — this is an assumption, not a real answer; flag it \
    and re-ask later if it turns out to matter.";

/// Build the combined tool-call result JSON for one `ask_question` call.
///
/// Called once every question in the call has a [`VerifiedAnswer`]
/// (invariant I4: answered, declined, and auto-resolved each produce a
/// distinct, machine-readable `state`).
///
/// `items` is the call's own parsed questions (in order); `answers` is every
/// [`VerifiedAnswer`] resolving one of them, matched by
/// [`VerifiedAnswer::index`]. An index in `items` with no matching entry in
/// `answers` renders as `"state": "unresolved"` — a defensive fallback the
/// caller must never actually reach (see [`crate::step::QuestionResumePrePass`],
/// which only calls this once every index resolves).
#[must_use]
pub fn question_call_result_json(items: &[QuestionItem], answers: &[VerifiedAnswer]) -> String {
    let entries: Vec<Value> = items
        .iter()
        .enumerate()
        .map(|(i, item)| {
            let index = u32::try_from(i).unwrap_or(u32::MAX);
            let Some(answer) = answers.iter().find(|a| a.index == index) else {
                return serde_json::json!({ "header": item.header, "state": "unresolved" });
            };
            match answer.state {
                AnswerState::Answered => serde_json::json!({
                    "header": item.header,
                    "state": "answered",
                    "selected_index": answer.selected_index,
                    "selected_label": answer.selected_label,
                }),
                AnswerState::Declined => serde_json::json!({
                    "header": item.header,
                    "state": "declined",
                    "note": DECLINED_NOTE,
                }),
                AnswerState::AutoResolved => serde_json::json!({
                    "header": item.header,
                    "state": "auto_resolved",
                    "selected_index": answer.selected_index,
                    "selected_label": answer.selected_label,
                    "note": AUTO_RESOLVED_NOTE,
                }),
            }
        })
        .collect();
    serde_json::json!({ "answers": entries }).to_string()
}

/// The reader-facing note attached to a still-pending interim result
/// (invariant I8) — the transcript-only splice
/// [`crate::step::QuestionResumePrePass`] builds when new turn input arrives
/// before a question is genuinely answered, so the model can act on the new
/// input instead of the whole turn silently re-pausing on the same dangling
/// call.
const STILL_PENDING_NOTE: &str = "Nobody has answered this yet — it's still open, not a real \
    answer. Don't re-ask it and don't assume what the answer will be. Handle whatever the user \
    just said, and only circle back to this question if it still matters once you have.";

/// Builds a transcript-only interim result for a call whose question(s) are
/// still unanswered when new turn input arrives (invariant I8).
///
/// An unrelated message arriving while a question is pending must reach the
/// model on its very next dispatch, not be silently dropped. Distinct from
/// [`question_call_result_json`]'s three real states
/// (invariant I4, `answered`/`declined`/`auto_resolved`) — `"state":
/// "still_pending"` can never be confused with a genuine answer. The caller
/// ([`crate::step::QuestionResumePrePass`], the only one) must splice this
/// into the provider-facing transcript ONLY, never into the durable
/// `TurnCtx::outputs` — persisting it would make the call look answered on
/// every later resume, permanently losing the real question.
#[must_use]
pub fn question_still_pending_json(items: &[QuestionItem]) -> String {
    let entries: Vec<Value> = items
        .iter()
        .map(|item| {
            serde_json::json!({
                "header": item.header,
                "state": "still_pending",
                "note": STILL_PENDING_NOTE,
            })
        })
        .collect();
    serde_json::json!({ "answers": entries }).to_string()
}

#[cfg(test)]
mod tests {
    #![allow(clippy::pedantic, clippy::nursery, missing_docs)]
    use super::*;
    use std::str::FromStr;

    /// Every `AnswerState` round-trips through its wire string unchanged —
    /// the single shared conversion `harness_dialer.rs` and
    /// `polyc_turn_runner::verify_question_answers` both call instead of
    /// re-deriving their own if/else chain.
    #[test]
    fn answer_state_round_trips_through_its_wire_string() {
        for state in [
            AnswerState::Answered,
            AnswerState::Declined,
            AnswerState::AutoResolved,
        ] {
            let wire: String = state.into();
            assert_eq!(AnswerState::from_str(&wire).unwrap(), state);
        }
    }

    #[test]
    fn answer_state_wire_strings_match_the_crypto_crate_consts() {
        assert_eq!(
            String::from(AnswerState::Answered),
            polyc_crypto::question::ANSWERED_STATE
        );
        assert_eq!(
            String::from(AnswerState::Declined),
            polyc_crypto::question::DECLINED_STATE
        );
        assert_eq!(
            String::from(AnswerState::AutoResolved),
            polyc_crypto::question::AUTO_RESOLVED_STATE
        );
    }

    #[test]
    fn answer_state_rejects_an_unrecognized_string() {
        assert!(AnswerState::from_str("not_a_real_state").is_err());
    }

    /// A single well-formed question with 2 options, one recommended.
    fn valid_call() -> String {
        serde_json::json!({
            "questions": [{
                "header": "Deploy target",
                "question": "Which environment should this ship to?",
                "options": [
                    {"label": "Staging", "description": "Deploys to staging only.", "recommended": true},
                    {"label": "Production", "description": "Deploys straight to production."}
                ]
            }]
        })
        .to_string()
    }

    #[test]
    fn parses_a_well_formed_call() {
        let items = parse_ask_question_args(&valid_call()).expect("valid call parses");
        assert_eq!(items.len(), 1);
        let q = &items[0];
        assert_eq!(q.header, "Deploy target");
        assert_eq!(q.question, "Which environment should this ship to?");
        assert_eq!(q.options.len(), 2);
        assert!(q.options[0].recommended);
        assert!(!q.options[1].recommended);
    }

    #[test]
    fn rejects_garbage_json() {
        let err = parse_ask_question_args("not json").unwrap_err();
        assert!(!err.to_string().is_empty());
    }

    /// `QuestionArgsError` is a typed wrapper over the exact model-facing
    /// sentence — its `Display` output must be byte-for-byte the message
    /// text, not `"QuestionArgsError(...)"` or any other wrapped rendering,
    /// since the caller feeds it to the model verbatim as the tool call's
    /// own `{"error": ...}` result.
    #[test]
    fn error_display_is_exactly_the_model_facing_sentence() {
        let err = parse_ask_question_args(r#"{"questions": []}"#).unwrap_err();
        assert_eq!(
            err.to_string(),
            "ask_question needs at least 1 question, got 0."
        );
    }

    #[test]
    fn rejects_zero_questions() {
        let err = parse_ask_question_args(r#"{"questions": []}"#).unwrap_err();
        assert!(err.to_string().contains("at least 1 question"), "{err}");
    }

    #[test]
    fn rejects_more_than_three_questions() {
        let one = serde_json::json!({
            "header": "h", "question": "q?",
            "options": [
                {"label": "a", "description": "d"},
                {"label": "b", "description": "d"}
            ]
        });
        let args = serde_json::json!({ "questions": [one.clone(), one.clone(), one.clone(), one] })
            .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("at most 3 questions"), "{err}");
    }

    #[test]
    fn rejects_fewer_than_two_options() {
        let args = serde_json::json!({
            "questions": [{
                "header": "h", "question": "q?",
                "options": [{"label": "a", "description": "d"}]
            }]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("between 2 and 4 options"), "{err}");
    }

    #[test]
    fn rejects_more_than_four_options() {
        let opt = serde_json::json!({"label": "a", "description": "d"});
        let args = serde_json::json!({
            "questions": [{
                "header": "h", "question": "q?",
                "options": [opt.clone(), opt.clone(), opt.clone(), opt.clone(), opt]
            }]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("between 2 and 4 options"), "{err}");
    }

    #[test]
    fn rejects_empty_option_label() {
        let args = serde_json::json!({
            "questions": [{
                "header": "h", "question": "q?",
                "options": [
                    {"label": "", "description": "d"},
                    {"label": "b", "description": "d"}
                ]
            }]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("label"), "{err}");
        assert!(err.to_string().contains("empty"), "{err}");
    }

    #[test]
    fn rejects_over_length_header() {
        let long_header = "x".repeat(MAX_HEADER_CHARS + 1);
        let args = serde_json::json!({
            "questions": [{
                "header": long_header, "question": "q?",
                "options": [
                    {"label": "a", "description": "d"},
                    {"label": "b", "description": "d"}
                ]
            }]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("header"), "{err}");
    }

    #[test]
    fn rejects_two_recommended_options() {
        let args = serde_json::json!({
            "questions": [{
                "header": "h", "question": "q?",
                "options": [
                    {"label": "a", "description": "d", "recommended": true},
                    {"label": "b", "description": "d", "recommended": true}
                ]
            }]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("at most one option"), "{err}");
    }

    #[test]
    fn rejects_missing_options_field() {
        let args = serde_json::json!({
            "questions": [{"header": "h", "question": "q?"}]
        })
        .to_string();
        let err = parse_ask_question_args(&args).unwrap_err();
        assert!(err.to_string().contains("options"), "{err}");
    }

    fn two_items() -> Vec<QuestionItem> {
        vec![
            QuestionItem {
                header: "Deploy target".to_owned(),
                question: "Which environment?".to_owned(),
                options: vec![
                    QuestionOption {
                        label: "Staging".to_owned(),
                        description: "d1".to_owned(),
                        recommended: false,
                    },
                    QuestionOption {
                        label: "Production".to_owned(),
                        description: "d2".to_owned(),
                        recommended: true,
                    },
                ],
            },
            QuestionItem {
                header: "Notify team?".to_owned(),
                question: "Should we notify the team?".to_owned(),
                options: vec![
                    QuestionOption {
                        label: "Yes".to_owned(),
                        description: "d3".to_owned(),
                        recommended: false,
                    },
                    QuestionOption {
                        label: "No".to_owned(),
                        description: "d4".to_owned(),
                        recommended: false,
                    },
                ],
            },
        ]
    }

    /// Invariant I4: answered / declined / auto-resolved must each produce a
    /// distinct, pairwise-different result JSON the model can act on
    /// differently.
    #[test]
    fn answered_declined_and_auto_resolved_produce_distinct_results() {
        let items = vec![two_items()[0].clone()];
        let answered = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::Answered,
                selected_index: Some(1),
                selected_label: "Production".to_owned(),
                answered_by: "slack:T1:U9".to_owned(),
            }],
        );
        let declined = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::Declined,
                selected_index: None,
                selected_label: String::new(),
                answered_by: "slack:T1:U9".to_owned(),
            }],
        );
        let auto_resolved = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::AutoResolved,
                selected_index: Some(1),
                selected_label: "Production".to_owned(),
                answered_by: String::new(),
            }],
        );

        assert_ne!(answered, declined);
        assert_ne!(answered, auto_resolved);
        assert_ne!(declined, auto_resolved);

        let a: serde_json::Value = serde_json::from_str(&answered).unwrap();
        assert_eq!(a["answers"][0]["state"], "answered");
        assert_eq!(a["answers"][0]["selected_label"], "Production");

        let d: serde_json::Value = serde_json::from_str(&declined).unwrap();
        assert_eq!(d["answers"][0]["state"], "declined");
        assert!(d["answers"][0].get("selected_index").is_none());

        let r: serde_json::Value = serde_json::from_str(&auto_resolved).unwrap();
        assert_eq!(r["answers"][0]["state"], "auto_resolved");
        assert!(
            r["answers"][0]["note"]
                .as_str()
                .unwrap()
                .contains("assumption"),
            "an auto-resolved answer must flag itself as an assumption, not a real answer"
        );
    }

    /// Invariant I8: the still-pending interim state is pairwise distinct
    /// from every I4 real answer state, so the model can never mistake "no
    /// one has answered yet" for a genuine answer/decline/auto-resolution.
    #[test]
    fn still_pending_is_distinct_from_every_real_answer_state() {
        let items = vec![two_items()[0].clone()];
        let still_pending = question_still_pending_json(&items);
        let answered = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::Answered,
                selected_index: Some(1),
                selected_label: "Production".to_owned(),
                answered_by: "slack:T1:U9".to_owned(),
            }],
        );
        let declined = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::Declined,
                selected_index: None,
                selected_label: String::new(),
                answered_by: "slack:T1:U9".to_owned(),
            }],
        );
        let auto_resolved = question_call_result_json(
            &items,
            &[VerifiedAnswer {
                call_id: "call-1".to_owned(),
                index: 0,
                state: AnswerState::AutoResolved,
                selected_index: Some(1),
                selected_label: "Production".to_owned(),
                answered_by: String::new(),
            }],
        );

        assert_ne!(still_pending, answered);
        assert_ne!(still_pending, declined);
        assert_ne!(still_pending, auto_resolved);

        let v: serde_json::Value = serde_json::from_str(&still_pending).unwrap();
        assert_eq!(v["answers"][0]["state"], "still_pending");
        assert!(v["answers"][0].get("selected_index").is_none());
        assert!(
            v["answers"][0]["note"]
                .as_str()
                .unwrap()
                .contains("still open"),
            "the still-pending note must tell the model this is not a real answer"
        );
    }

    /// A call with more than one question renders one entry per question, in
    /// order, each independently resolved.
    #[test]
    fn multi_question_call_renders_one_entry_per_question() {
        let items = two_items();
        let json = question_call_result_json(
            &items,
            &[
                VerifiedAnswer {
                    call_id: "call-1".to_owned(),
                    index: 0,
                    state: AnswerState::Answered,
                    selected_index: Some(0),
                    selected_label: "Staging".to_owned(),
                    answered_by: "slack:T1:U9".to_owned(),
                },
                VerifiedAnswer {
                    call_id: "call-1".to_owned(),
                    index: 1,
                    state: AnswerState::Declined,
                    selected_index: None,
                    selected_label: String::new(),
                    answered_by: "slack:T1:U9".to_owned(),
                },
            ],
        );
        let v: serde_json::Value = serde_json::from_str(&json).unwrap();
        assert_eq!(v["answers"].as_array().unwrap().len(), 2);
        assert_eq!(v["answers"][0]["header"], "Deploy target");
        assert_eq!(v["answers"][0]["state"], "answered");
        assert_eq!(v["answers"][1]["header"], "Notify team?");
        assert_eq!(v["answers"][1]["state"], "declined");
    }
}