harn-stdlib 0.8.57

Embedded Harn standard library source catalog
Documentation
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import { agent_emit_event, agent_session_inject_feedback } from "std/agent/state"

// Deterministic thrash / degenerate-loop detector over the agent's
// action/observation stream (#2712, part of the #2708 cheap-model
// reliability stack).
//
// This is the deterministic GATE in the reliability stack. An LLM
// "are we thrashing?" self-evaluation is unreliable on its own: intrinsic
// self-evaluation degrades otherwise-correct work (Huang et al., ICLR 2024;
// Kamoi et al., TACL 2024). So the advisory judge (consulted via
// `loop.harn`'s `stall_judge_due` path) must NEVER fire on its own — it is
// consulted only AFTER this detector trips, and even then it stays advisory.
//
// Compose, do not duplicate: every trip is surfaced through the EXISTING
// `agent_loop_stall_warning` event (the `warning` payload is passed through
// to the host verbatim, so enriching it needs no Rust change), the advisory
// judge stays gated on `stall_warning != nil`, and a hard stop surfaces
// through the loop's existing terminal `stuck` / `loop_control_decision`
// path. We deliberately avoid a parallel Rust detector or a new hook surface.
//
// Trip conditions (each behind a named, tunable threshold; mirrors the
// design reference's defaults):
//
//   1. same action -> byte-identical observation, repeated >= 4 times. This
//      SUBSUMES the old adjacent-same-signature logic with an
//      observation-signature refinement.
//   2. same action -> same error, repeated >= 3 times.
//   3. no-progress monologue: >= 3 consecutive assistant turns with text but
//      no tool call.
//   4. ping-pong: A,B,A,B alternation between two actions >= 6 cycles.
//   5. repeated context-window / token-limit errors >= 2 times.
//
// The polling / retry exemption (principled, not an allowlist; the fix for
// OpenHands #5355): a repeated identical action only counts toward conditions
// (1) and (4) when its observation signature is BYTE-IDENTICAL across
// repeats. Legitimate polling produces a changing observation (the status
// advances, the watched file mutates), which resets the streak, so polling
// never trips. The `exempt_tools` allowlist still works for back-compat but
// is now a SECONDARY escape hatch — the observation-signature principle is
// the primary mechanism.
// same action -> identical observation repeats before tripping.
const STALL_REPEAT_SAME_OBSERVATION = 4

// same action -> same error repeats before tripping.
const STALL_REPEAT_SAME_ERROR = 3

// consecutive no-progress agent messages (text, no tool call) before tripping.
const STALL_NO_PROGRESS_MESSAGES = 3

// ping-pong cycles (A,B,A,B,...) between two actions before tripping.
const STALL_PING_PONG_CYCLES = 6

// repeated context-window / token-limit errors before tripping.
const STALL_REPEAT_CONTEXT_WINDOW_ERROR = 2

// consecutive un-recovered trips before a hard stop is recommended. A trip
// "recovers" when a turn produces a step that does not itself trip (the agent
// broke the loop). Past this many back-to-back trips the detector flags
// `hard_stop` so the loop can surface a terminal stuck stop instead of
// nudging forever.
const STALL_HARD_STOP_AFTER_TRIPS = 3

type AgentStallConfig = {
  enabled: bool,
  threshold: int,
  inject_feedback: bool,
  max_feedback: int,
  exempt_tools: list,
  include_arguments: bool,
  repeat_same_observation: int,
  repeat_same_error: int,
  no_progress_messages: int,
  ping_pong_cycles: int,
  repeat_context_window_error: int,
  hard_stop_after_trips: int,
}

type AgentStallWarning = {
  iteration: int,
  tool_name: string,
  repeat_count: int,
  threshold: int,
  arguments_digest: string,
  signature_digest: string,
  pattern: string,
  signature: string,
  count: int,
  consecutive_trips: int,
  hard_stop: bool,
  arguments?: dict,
}

type AgentStallState = {
  last_signature: string,
  streak: int,
  warnings: list<AgentStallWarning>,
  repeated_tool_calls: int,
  feedback_count: int,
  last_observation_signature: string,
  last_outcome_kind: string,
  same_observation_streak: int,
  same_error_streak: int,
  context_window_error_streak: int,
  no_progress_streak: int,
  ping_pong_a: string,
  ping_pong_b: string,
  ping_pong_alternations: int,
  consecutive_trips: int,
  hard_stop: bool,
}

type AgentStallObservation = {
  state: AgentStallState,
  enabled: bool,
  warning: AgentStallWarning?,
  feedback_deferred: bool,
  config: AgentStallConfig,
  hard_stop: bool,
}

fn __agent_stall_bool(value, fallback: bool, field: string) -> bool {
  if value == nil {
    return fallback
  }
  if type_of(value) == "bool" {
    return value
  }
  throw "agent_loop: stall_diagnostics." + field + " must be a bool; got " + type_of(value)
}

fn __agent_stall_list(value, field: string) -> list {
  if value == nil {
    return []
  }
  if type_of(value) == "list" {
    return value
  }
  throw "agent_loop: stall_diagnostics." + field + " must be a list; got " + type_of(value)
}

fn __agent_stall_int(value, fallback: int, minimum: int) -> int {
  if type_of(value) == "int" && value >= minimum {
    return value
  }
  return fallback
}

fn __agent_stall_default_config() -> AgentStallConfig {
  return {
    enabled: false,
    threshold: 3,
    inject_feedback: true,
    max_feedback: 1,
    exempt_tools: [],
    include_arguments: false,
    repeat_same_observation: STALL_REPEAT_SAME_OBSERVATION,
    repeat_same_error: STALL_REPEAT_SAME_ERROR,
    no_progress_messages: STALL_NO_PROGRESS_MESSAGES,
    ping_pong_cycles: STALL_PING_PONG_CYCLES,
    repeat_context_window_error: STALL_REPEAT_CONTEXT_WINDOW_ERROR,
    hard_stop_after_trips: STALL_HARD_STOP_AFTER_TRIPS,
  }
}

fn __agent_stall_config(value) -> AgentStallConfig {
  let defaults = __agent_stall_default_config()
  if value == nil {
    return defaults
  }
  if type_of(value) == "bool" {
    return defaults + {enabled: value}
  }
  if type_of(value) != "dict" {
    throw "agent_loop: `stall_diagnostics` must be a dict, bool, or nil; got " + type_of(value)
  }
  let threshold = value?.threshold ?? 3
  let max_feedback = value?.max_feedback ?? 1
  let exempt_tools = if value?.exempt_tools != nil {
    __agent_stall_list(value.exempt_tools, "exempt_tools")
  } else {
    __agent_stall_list(value?.allow_repeated_tools, "allow_repeated_tools")
  }
  let resolved_threshold = if type_of(threshold) == "int" && threshold >= 2 {
    threshold
  } else {
    3
  }
  // The legacy `threshold` knob (N repeated identical calls) IS the same intent
  // as the same-observation condition, so when a caller sets it explicitly it
  // also drives `repeat_same_observation` for back-compat. Absent an explicit
  // `threshold`, the same-observation condition uses the reference default (4).
  let same_observation_default = if value?.threshold != nil {
    resolved_threshold
  } else {
    STALL_REPEAT_SAME_OBSERVATION
  }
  return {
    enabled: __agent_stall_bool(value?.enabled, true, "enabled"),
    threshold: resolved_threshold,
    inject_feedback: __agent_stall_bool(value?.inject_feedback, true, "inject_feedback"),
    max_feedback: if type_of(max_feedback) == "int" && max_feedback >= 0 {
      max_feedback
    } else {
      1
    },
    exempt_tools: exempt_tools,
    include_arguments: __agent_stall_bool(value?.include_arguments, false, "include_arguments"),
    repeat_same_observation: __agent_stall_int(value?.repeat_same_observation, same_observation_default, 2),
    repeat_same_error: __agent_stall_int(value?.repeat_same_error, STALL_REPEAT_SAME_ERROR, 2),
    no_progress_messages: __agent_stall_int(value?.no_progress_messages, STALL_NO_PROGRESS_MESSAGES, 2),
    ping_pong_cycles: __agent_stall_int(value?.ping_pong_cycles, STALL_PING_PONG_CYCLES, 2),
    repeat_context_window_error: __agent_stall_int(value?.repeat_context_window_error, STALL_REPEAT_CONTEXT_WINDOW_ERROR, 1),
    hard_stop_after_trips: __agent_stall_int(value?.hard_stop_after_trips, STALL_HARD_STOP_AFTER_TRIPS, 1),
  }
}

/**
 * agent_stall_initial_state creates repeated-tool-call diagnostic state.
 *
 * @effects: []
 * @allocation: heap
 * @errors: []
 * @api_stability: experimental
 * @example: agent_stall_initial_state()
 */
pub fn agent_stall_initial_state() -> AgentStallState {
  return {
    last_signature: "",
    streak: 0,
    warnings: [],
    repeated_tool_calls: 0,
    feedback_count: 0,
    last_observation_signature: "",
    last_outcome_kind: "",
    same_observation_streak: 0,
    same_error_streak: 0,
    context_window_error_streak: 0,
    no_progress_streak: 0,
    ping_pong_a: "",
    ping_pong_b: "",
    ping_pong_alternations: 0,
    consecutive_trips: 0,
    hard_stop: false,
  }
}

/*
 * Reset only the action-stream tracking (signatures, observation/error
 * streaks, ping-pong). Leaves the consecutive-trip escalation and feedback
 * counters alone. Used when an action is exempt or the turn made no tool call.
 */
fn __agent_stall_reset_action(state: AgentStallState) -> AgentStallState {
  return state
    + {
    last_signature: "",
    streak: 0,
    last_observation_signature: "",
    last_outcome_kind: "",
    same_observation_streak: 0,
    same_error_streak: 0,
    context_window_error_streak: 0,
    ping_pong_a: "",
    ping_pong_b: "",
    ping_pong_alternations: 0,
  }
}

fn __agent_tool_call_name(call) -> string {
  return to_string(call?.name ?? call?.tool_name ?? "")
}

fn __agent_tool_call_args(call) -> dict {
  let raw = call?.arguments ?? call?.tool_args
  if type_of(raw) == "dict" {
    return raw
  }
  return {}
}

fn __agent_tool_call_signature(call) -> string {
  let args_text = json_stringify(__agent_tool_call_args(call))
  return __agent_tool_call_name(call) + "\n" + args_text
}

/* observation classification (the polling-exemption mechanism) */
fn __agent_stall_result_ok(result) -> bool {
  if result?.ok != nil {
    return result.ok ? true : false
  }
  if result?.success != nil {
    return result.success ? true : false
  }
  let status = to_string(result?.status ?? "")
  return status == "ok" || status == "success"
}

fn __agent_stall_result_name(result) -> string {
  return to_string(result?.tool_name ?? result?.name ?? "")
}

/*
 * A context-window / token-limit error is its own trip condition because
 * repeating it is never productive and never recovers on its own.
 */
fn __agent_stall_is_context_window_error(text: string) -> bool {
  let lowered = lowercase(text)
  return contains(lowered, "context window")
    || contains(lowered, "context length")
    || contains(lowered, "context_length")
    || contains(lowered, "maximum context")
    || contains(lowered, "token limit")
    || contains(lowered, "too many tokens")
    || contains(lowered, "context_length_exceeded")
    || contains(lowered, "max_tokens")
}

/*
 * Outcome of a dispatched result, normalized for the detector: one of
 * "ok" / "error" / "context_window", plus a byte-stable signature of the
 * observation payload (for "ok") or the error text (for "error").
 */
fn __agent_stall_result_outcome(result) -> dict {
  if __agent_stall_result_ok(result) {
    let payload = json_stringify(result?.result ?? result?.output ?? result?.content ?? nil)
    return {kind: "ok", signature: "ok:" + sha256(payload)}
  }
  let error_text = to_string(result?.error ?? result?.message ?? result?.result ?? "")
  if __agent_stall_is_context_window_error(error_text) {
    return {kind: "context_window", signature: "ctx"}
  }
  return {kind: "error", signature: "err:" + sha256(error_text)}
}

/*
 * Find the dispatch result for the given tool name. The detector tracks one
 * action at a time, so the first matching result is the relevant observation.
 */
fn __agent_stall_outcome_for(prev_dispatch, tool_name: string) {
  if prev_dispatch == nil {
    return nil
  }
  let results = if type_of(prev_dispatch) == "list" {
    prev_dispatch
  } else {
    prev_dispatch?.results ?? []
  }
  for result in results {
    if __agent_stall_result_name(result) == tool_name {
      return __agent_stall_result_outcome(result)
    }
  }
  return nil
}

fn __agent_stall_feedback_text(warning: AgentStallWarning) -> string {
  let pattern = warning.pattern
  let count = to_string(warning.count)
  let core = if pattern == "repeated_same_observation" {
    "the action `" + warning.tool_name + "` produced the same observation " + count
      + " times in a row"
  } else if pattern == "repeated_error" {
    "the action `" + warning.tool_name + "` failed with the same error " + count + " times in a row"
  } else if pattern == "no_progress_monologue" {
    count + " consecutive assistant messages made no progress (no tool call)"
  } else if pattern == "ping_pong" {
    "the loop is ping-ponging between two actions (" + count + " cycles)"
  } else if pattern == "repeated_context_window_error" {
    "the run hit a context-window error " + count + " times in a row"
  } else {
    "the last " + count + " tool calls repeated `" + warning.tool_name
      + "` with identical arguments"
  }
  if warning.hard_stop {
    return "Loop detector (hard stop): "
      + core
      + ". "
      + to_string(warning.consecutive_trips)
      + " trips with no recovery — stop and report the blocker instead of repeating."
  }
  return "Stall diagnostic: "
    + core
    + ". Use different evidence, finish, or explain why repeating is necessary before doing so again."
}

fn __agent_stall_warning_record(
  iteration: int,
  tool_name: string,
  args: dict,
  signature: string,
  pattern: string,
  count: int,
  consecutive_trips: int,
  hard_stop: bool,
  config: AgentStallConfig,
  threshold: int,
) -> AgentStallWarning {
  let args_text = json_stringify(args)
  var record = {
    iteration: iteration,
    tool_name: tool_name,
    repeat_count: count,
    threshold: threshold,
    arguments_digest: "sha256:" + sha256(args_text),
    signature_digest: "sha256:" + sha256(signature),
    pattern: pattern,
    signature: signature,
    count: count,
    consecutive_trips: consecutive_trips,
    hard_stop: hard_stop,
  }
  if config.include_arguments {
    record = record + {arguments: args}
  }
  return record
}

/**
 * agent_stall_inject_feedback injects bounded stall feedback.
 *
 * @effects: [agent]
 * @allocation: heap
 * @errors: []
 * @api_stability: experimental
 * @example: agent_stall_inject_feedback(session_id, warning, config, state)
 */
pub fn agent_stall_inject_feedback(
  session_id: string,
  warning: AgentStallWarning,
  config: AgentStallConfig,
  state: AgentStallState,
) -> AgentStallState {
  let wants_feedback = config.inject_feedback ?? true
  let should_feedback = wants_feedback && state.feedback_count < config.max_feedback
  if should_feedback {
    agent_session_inject_feedback(session_id, "stall_diagnostics", __agent_stall_feedback_text(warning))
    return state + {feedback_count: state.feedback_count + 1}
  }
  return state
}

fn __agent_stall_maybe_emit(
  session_id: string,
  warning: AgentStallWarning,
  config: AgentStallConfig,
  state: AgentStallState,
  defer_feedback: bool,
) {
  agent_emit_event(session_id, "agent_loop_stall_warning", warning)
  if defer_feedback {
    return {state: state, warning: warning, feedback_deferred: true}
  }
  return {
    state: agent_stall_inject_feedback(session_id, warning, config, state),
    warning: warning,
    feedback_deferred: false,
  }
}

/*
 * ping-pong tracking: track the two action signatures in a candidate A/B
 * alternation and the count of alternations. Two alternations (A->B->A) is one
 * cycle. Returns the updated state; the cycle count lives in
 * `ping_pong_alternations`.
 */
fn __agent_stall_update_ping_pong(state: AgentStallState, signature: string) -> AgentStallState {
  let a = state.ping_pong_a
  let b = state.ping_pong_b
  if a == "" {
    return state + {ping_pong_a: signature, ping_pong_b: "", ping_pong_alternations: 0}
  }
  if b == "" {
    if a == signature {
      // Same action twice — this is the same-action repeat path, not ping-pong.
      return state + {ping_pong_alternations: 0}
    }
    return state + {ping_pong_b: signature, ping_pong_alternations: 1}
  }
  let expected_next = if state.ping_pong_alternations % 2 == 1 {
    a
  } else {
    b
  }
  if expected_next == signature {
    return state + {ping_pong_alternations: state.ping_pong_alternations + 1}
  }
  if a == signature || b == signature {
    // Within the A/B pair but out of strict alternation: restart the pair
    // anchored on the current value.
    return state + {ping_pong_a: signature, ping_pong_b: "", ping_pong_alternations: 0}
  }
  // A third distinct action: not a two-action ping-pong.
  return state + {ping_pong_a: signature, ping_pong_b: "", ping_pong_alternations: 0}
}

/*
 * Apply a fired trip: bump the consecutive-trip escalation and decide whether
 * to flag a hard stop. Returns the state with the trip recorded.
 */
fn __agent_stall_register_trip(state: AgentStallState, config: AgentStallConfig) -> AgentStallState {
  let trips = state.consecutive_trips + 1
  return state + {consecutive_trips: trips, hard_stop: trips >= config.hard_stop_after_trips}
}

/*
 * A non-tripping step recovers: reset the consecutive-trip escalation so the
 * hard stop only fires on genuinely uninterrupted thrashing.
 */
fn __agent_stall_register_recovery(state: AgentStallState) -> AgentStallState {
  return state + {consecutive_trips: 0, hard_stop: false}
}

/*
 * Detect a no-progress monologue turn (assistant produced text but no tool
 * call). Returns the observation when the streak crosses the threshold.
 */
fn __agent_stall_observe_no_progress(
  session_id: string,
  iteration: int,
  config: AgentStallConfig,
  state: AgentStallState,
  defer_feedback: bool,
) -> AgentStallObservation {
  // An agent message breaks any action-repeat / ping-pong run.
  var next_state = __agent_stall_reset_action(state)
  next_state = next_state + {no_progress_streak: next_state.no_progress_streak + 1}
  if next_state.no_progress_streak < config.no_progress_messages {
    next_state = __agent_stall_register_recovery(next_state)
    return {
      state: next_state,
      enabled: true,
      warning: nil,
      feedback_deferred: false,
      config: config,
      hard_stop: false,
    }
  }
  next_state = __agent_stall_register_trip(next_state, config)
  let warning = __agent_stall_warning_record(
    iteration,
    "",
    {},
    "",
    "no_progress_monologue",
    next_state.no_progress_streak,
    next_state.consecutive_trips,
    next_state.hard_stop,
    config,
    config.no_progress_messages,
  )
  let emitted = __agent_stall_maybe_emit(session_id, warning, config, next_state, defer_feedback)
  next_state = emitted.state + {warnings: emitted.state.warnings.push(warning)}
  return {
    state: next_state,
    enabled: true,
    warning: warning,
    feedback_deferred: emitted?.feedback_deferred ?? false,
    config: config,
    hard_stop: next_state.hard_stop,
  }
}

/*
 * __agent_stall_process_call folds a single tool call (and the observation it
 * produced last turn) into the detector state and decides which condition, if
 * any, tripped. Extracted from `agent_stall_observe_tool_calls` to keep that
 * function within the cyclomatic-complexity budget. Returns the updated state
 * plus a `trip` dict (or nil). Trip ordering: context-window, then repeated
 * error, then repeated identical observation, then ping-pong, then the legacy
 * signature-only threshold (used only when no dispatch results are available).
 */
fn __agent_stall_process_call(
  state: AgentStallState,
  config: AgentStallConfig,
  call,
  tool_name: string,
  prev_dispatch,
) -> dict {
  let signature = __agent_tool_call_signature(call)
  let same_action = signature == state.last_signature
  let outcome = __agent_stall_outcome_for(prev_dispatch, tool_name)
  // Observation signature of the action that just repeated. When dispatch
  // results are unavailable, fall back to the action signature itself so the
  // legacy adjacent-repeat behavior still trips.
  let obs_signature = if outcome != nil {
    outcome.signature
  } else {
    "sig:" + sha256(signature)
  }
  let outcome_kind = if outcome != nil {
    outcome.kind
  } else {
    "ok"
  }
  // Ping-pong is independent of the same-action streak and only considers
  // distinct alternating actions; update it first.
  var next_state = __agent_stall_update_ping_pong(state, signature)
  let streak = if same_action {
    next_state.streak + 1
  } else {
    1
  }
  let repeated = if streak > 1 {
    next_state.repeated_tool_calls + 1
  } else {
    next_state.repeated_tool_calls
  }
  // The polling exemption (principled, not an allowlist): a repeated identical
  // action counts toward the same-observation condition UNLESS we have positive
  // evidence the observation changed — i.e. both this turn's and last turn's
  // observations are real (non-fallback) AND differ. A changing observation is
  // legitimate polling (status advances, watched file mutates) and resets the
  // streak. When observations are unavailable (no dispatch results threaded in)
  // the streak counts the raw signature repeat, preserving the legacy
  // adjacent-identical-call behavior so existing thresholds still trip.
  let both_known = outcome != nil && next_state.last_outcome_kind != ""
  let observation_changed = both_known && obs_signature != next_state.last_observation_signature
  let new_same_observation_streak = if !same_action || outcome_kind != "ok" {
    if outcome_kind == "ok" {
      1
    } else {
      0
    }
  } else if observation_changed {
    1
  } else {
    next_state.same_observation_streak + 1
  }
  // Same-error streak: same action producing the same (or unknown) error.
  // Distinct errors reset, because the agent is making different mistakes.
  let new_same_error_streak = if !same_action || outcome_kind != "error" {
    if outcome_kind == "error" {
      1
    } else {
      0
    }
  } else if observation_changed {
    1
  } else {
    next_state.same_error_streak + 1
  }
  let new_context_streak = if outcome_kind == "context_window" {
    next_state.context_window_error_streak + 1
  } else {
    0
  }
  next_state = next_state
    + {
    last_signature: signature,
    streak: streak,
    repeated_tool_calls: repeated,
    last_observation_signature: obs_signature,
    last_outcome_kind: if outcome != nil {
      outcome_kind
    } else {
      ""
    },
    same_observation_streak: new_same_observation_streak,
    same_error_streak: new_same_error_streak,
    context_window_error_streak: new_context_streak,
  }
  let ping_pong_cycles = next_state.ping_pong_alternations / 2
  let trip = if new_context_streak >= config.repeat_context_window_error {
    {
      pattern: "repeated_context_window_error",
      count: new_context_streak,
      threshold: config.repeat_context_window_error,
    }
  } else if new_same_error_streak >= config.repeat_same_error {
    {pattern: "repeated_error", count: new_same_error_streak, threshold: config.repeat_same_error}
  } else if outcome_kind == "ok" && new_same_observation_streak >= config.repeat_same_observation {
    {
      pattern: "repeated_same_observation",
      count: new_same_observation_streak,
      threshold: config.repeat_same_observation,
    }
  } else if ping_pong_cycles >= config.ping_pong_cycles {
    {pattern: "ping_pong", count: ping_pong_cycles, threshold: config.ping_pong_cycles}
  } else if outcome == nil && streak >= config.threshold {
    {pattern: "repeated_same_signature", count: streak, threshold: config.threshold}
  } else {
    nil
  }
  return {state: next_state, trip: trip}
}

/**
 * agent_stall_observe_tool_calls detects degenerate agent loops.
 *
 * Conditions: same action -> identical observation, same action -> same
 * error, no-progress monologue, ping-pong, and repeated context-window
 * errors. `prev_dispatch` carries the previous turn's dispatch results so the
 * detector can attribute an observation signature to the repeated action;
 * pass nil to fall back to the signature-only same-action heuristic. The
 * polling exemption is principled: a repeated identical action counts toward
 * the same-observation and ping-pong conditions only when its observation is
 * byte-identical across repeats. `exempt_tools` remains a secondary escape
 * hatch.
 *
 * @effects: [agent]
 * @allocation: heap
 * @errors: [agent_loop]
 * @api_stability: experimental
 * @example: agent_stall_observe_tool_calls(session_id, calls, iteration, config, state, true, prev_dispatch, text)
 */
pub fn agent_stall_observe_tool_calls(
  session_id: string,
  tool_calls: list,
  iteration: int,
  raw_config,
  state: AgentStallState,
  defer_feedback: bool,
  prev_dispatch = nil,
  turn_text = "",
) -> AgentStallObservation {
  let config = __agent_stall_config(raw_config)
  if !config.enabled {
    return {
      state: state,
      enabled: false,
      warning: nil,
      feedback_deferred: false,
      config: config,
      hard_stop: false,
    }
  }
  if len(tool_calls) == 0 {
    // No tool call this turn. A turn with visible text but no tool call is a
    // no-progress monologue candidate; a fully empty turn just resets the
    // action stream.
    if to_string(turn_text) != "" {
      return __agent_stall_observe_no_progress(session_id, iteration, config, state, defer_feedback)
    }
    return {
      state: __agent_stall_register_recovery(__agent_stall_reset_action(state)),
      enabled: true,
      warning: nil,
      feedback_deferred: false,
      config: config,
      hard_stop: false,
    }
  }
  var next_state = state + {no_progress_streak: 0}
  var emitted_warning = nil
  var feedback_deferred = false
  for call in tool_calls {
    let tool_name = __agent_tool_call_name(call)
    if tool_name == "" || contains(config.exempt_tools, tool_name) {
      next_state = __agent_stall_register_recovery(__agent_stall_reset_action(next_state))
      continue
    }
    let processed = __agent_stall_process_call(next_state, config, call, tool_name, prev_dispatch)
    next_state = processed.state
    let trip = processed.trip
    if trip != nil {
      next_state = __agent_stall_register_trip(next_state, config)
      let warning = __agent_stall_warning_record(
        iteration,
        tool_name,
        __agent_tool_call_args(call),
        __agent_tool_call_signature(call),
        trip.pattern,
        trip.count,
        next_state.consecutive_trips,
        next_state.hard_stop,
        config,
        trip.threshold,
      )
      let emitted = __agent_stall_maybe_emit(session_id, warning, config, next_state, defer_feedback)
      next_state = emitted.state
      if emitted_warning == nil {
        emitted_warning = warning
      }
      feedback_deferred = feedback_deferred || emitted?.feedback_deferred ?? false
      next_state = next_state + {warnings: next_state.warnings.push(warning)}
    } else {
      next_state = __agent_stall_register_recovery(next_state)
    }
  }
  return {
    state: next_state,
    enabled: true,
    warning: emitted_warning,
    feedback_deferred: feedback_deferred,
    config: config,
    hard_stop: next_state.hard_stop,
  }
}

/**
 * agent_stall_apply_result adds stall diagnostics to an agent-loop result.
 *
 * @effects: []
 * @allocation: heap
 * @errors: []
 * @api_stability: experimental
 * @example: agent_stall_apply_result(result, enabled, state)
 */
pub fn agent_stall_apply_result(result: dict, stall_enabled: bool, stall_state: AgentStallState) -> dict {
  if !stall_enabled && len(stall_state.warnings) == 0 {
    return result
  }
  return result
    + {
    repeated_tool_calls: stall_state.repeated_tool_calls,
    stall_warnings: stall_state.warnings,
    suspected_loop: len(stall_state.warnings) > 0,
  }
}

fn __agent_done_judge_stall_cadence(opts) {
  let judge = opts?.done_judge
  if type_of(judge) != "dict" {
    return nil
  }
  let cadence = judge?.cadence
  if type_of(cadence) != "dict" || cadence?.when != "stalled" {
    return nil
  }
  return cadence
}

/**
 * agent_stall_done_judge_due decides whether the stall done judge is due.
 *
 * @effects: []
 * @allocation: stack
 * @errors: []
 * @api_stability: experimental
 * @example: agent_stall_done_judge_due(opts, 0, 3)
 */
pub fn agent_stall_done_judge_due(opts, invocations: int, turn_number: int) -> bool {
  let cadence = __agent_done_judge_stall_cadence(opts)
  if cadence == nil {
    return false
  }
  let max_invocations = cadence?.max_invocations
  if max_invocations != nil && invocations >= max_invocations {
    return false
  }
  let min_iterations = cadence?.min_iterations_before_first
  if min_iterations != nil && turn_number <= min_iterations {
    return false
  }
  let every = cadence?.every
  if every != nil && turn_number % every != 0 {
    return false
  }
  return true
}