# Vikunja: #460 — Retry budget: track all seen gate fingerprints, charge on repeat (cycle detection)

**Problem**

`DefaultRetryCoordinator.decide` compares the current failure fingerprint against only the *previous* one (`core/kernel/src/main/kotlin/com/correx/core/kernel/retry/DefaultRetryCoordinator.kt:29`):

```kotlin
val prevFingerprint = state.gateFailureFingerprints[gate]
val progressed = prevFingerprint != fingerprint
val charged = !progressed
```

A single slot cannot see a cycle. Whack-a-mole (fix A breaks B, fix B breaks A) alternates two fingerprints forever, every round reads as progress, nothing is ever charged, and the per-gate budget never triggers. `DefaultSessionOrchestratorStep.kt:296` already acknowledges this ("can be fooled into treating as still progressing indefinitely") but guards only inside the recovery stage. A normal implementer stage has no equivalent guard.

**Fix**

Make `OrchestrationState.gateFailureFingerprints[gate]` a `Set<String>` of every fingerprint seen for that gate, and charge when the current one is a repeat:

```kotlin
val seen = state.gateFailureFingerprints[gate]
val charged = fingerprint in seen
```

Touches: `OrchestrationState` field type, the reducer that writes it, `DefaultRetryCoordinator.decide`.

**Why not count-based progress**

Rejected: "charge unless the failing-item count went down". A syntax error masks later errors — fix `'}' expected` and tsc parses further, reporting 5 real type errors where there was 1. Count goes 1 to 5 on the most productive edit of the run, and the guard would charge the budget for genuine progress.

**Cases**

- Unmasking, `{syntax}` to `{5 type errors}`: new fingerprint, unseen, free. Correct.
- Grinding down, 3 to 2 to 1 errors: each state distinct, all free. Correct.
- Whack-a-mole, A/B/A: round 3 repeats round 1, charged. This is the case the single slot misses today.

**Known limit**

Detects cycles, not progress. A stage emitting a fresh distinct failure every round is still unbounded; only `stageCount` catches it. Worth measuring with `scripts/artread.py` over a few failed sessions before assuming that pattern matters.

## Acceptance criteria

- [ ] (fill in before starting)

## Quality gate

```sh
# the command that must pass, e.g. make check
```

## Rules

- Do not edit this file.
- One task, one session, one PR. Keep the diff under ~300 lines.
- Finish with `task pr`.