…29747)

Reporter diagnosed three independent gaps that together allowed infinite
'unblock → re-stuck' loops with no surfacing or escalation:

GAP 1: `_rule_stuck_in_blocked` resets timer on any `commented`/`unblocked`
event, so a task that cycles every few minutes is invisible to it
regardless of how many times it cycles.

Fix: new `_rule_block_unblock_cycling` rule (`hermes_cli/kanban_diagnostics.py`)
that counts block→unblock cycles in a sliding window. Default threshold
3 cycles within 24h, configurable via `block_cycle_threshold` /
`block_cycle_window_seconds`. Walks events in arrival order (event id)
since multiple events can share the same `created_at` second. Fires as a
warning with a CLI hint to inspect the block reasons.

GAP 2: Iteration-budget-exhausted runs in kanban workers map to
`kanban_block` (status=blocked, but a clean exit from the kernel's
perspective). `_rule_repeated_failures` reads `consecutive_failures`,
which `_record_task_failure` increments only for crashed/timed_out/
spawn_failed — `blocked` outcome bypasses the failure counter, so the
`kanban.failure_limit` circuit breaker never trips on budget-exhaustion
loops.

Fix: `agent/conversation_loop.py` budget-exhaustion path now calls
`_record_task_failure(outcome="timed_out")` instead of `kanban_block`.
Budget exhaustion is genuinely a timeout-shaped failure (the task ran out
of allowed iterations), so this is more honest semantics; it also routes
through the unified failure counter, so repeated budget exhaustions trip
the circuit breaker and the task auto-blocks with `gave_up` after
`failure_limit` retries.

GAP 3: `release_stale_claims` uses `_pid_alive(worker_pid)` only and
ignores `last_heartbeat_at`. Reporter observed a 91-min run that held
its claim with frozen heartbeat because the worker entered a logic loop
with no tool calls — `_pid_alive` kept returning True so the claim was
extended every 15 minutes indefinitely.

Fix: heartbeat-stale backstop. If `last_heartbeat_at` is set AND older
than `DEFAULT_CLAIM_HEARTBEAT_MAX_STALE_SECONDS` (default 1h), reclaim
even if the PID is alive. NULL `last_heartbeat_at` preserves backward
compatibility (no heartbeat yet = extend, as before). The reclaim event
payload now includes a `heartbeat_stale` boolean so operators see why a
live-PID worker was reclaimed.

This works cleanly in concert with PR #34418 (#31752 runtime → heartbeat
bridge): once `_touch_activity` keeps `last_heartbeat_at` fresh as a
side effect of normal API traffic, the backstop only fires for genuinely
wedged workers (no chunks, no tool results, no progress at all).

Co-authored-by: baofuen <45189813+baofuen@users.noreply.github.com>