## Parent issue

[Lexus2016]

Parent issue

#464 — Auxiliary Client Fallback Chain Non-Functional

This slice

Track consecutive failures per auxiliary provider entry; after 3 failures, stop attempting that entry for the remainder of the session and log the decision.

Acceptance criteria

• Per-entry failure counter persisted in-memory for the session.
• Entry disabled after threshold with clear log line.
• Counter resets on a successful call.
• Unit test for disable threshold.

Estimated effort

Easy (< 4h)

[Lexus2016]

Child of parent issue. This slice must land before the parent can be closed.

[Da-Mikey]

Deferred — needs further decomposition

Reason: agent/auxiliary_client.py (270K, 6082 lines) is one of the largest files in the codebase. The per-entry failure counter needs integration with CredentialPool.mark_exhausted_and_rotate and the in-memory _client_cache. This is a significant architectural change touching cache eviction, pool rotation, and provider client resolution. Estimated 4h is understated. Suggest: start with a standalone _FailureCounter utility class (collections.Counter with a configurable threshold and auto-reset on success), then wire it into the credential pool separately.

[Da-Mikey]

Deferred at implementation: larger than estimated. The auxiliary client (agent/auxiliary_client.py) is ~6.2k lines with a complex fallback chain. Adding per-entry failure tracking touches the provider resolution, client creation, and fallback routing paths — real scope confirmed at ~12h.

Proposed decomposition:

1. Standalone _FailureCounter class in a shared utility (e.g. hermes_cli/breaker.py) — configurable N failures, thread-safe, reset-on-success.
2. Auxiliary entry wrapper — wrap each fallback entry with failure tracking, skip on threshold.
3. Integration with resolve_provider_client() — check failure counter before attempting entry.
4. Logging — clear log line when entry is disabled after threshold.
5. Tests — unit test with mocked failures.

Step 1 (standalone _FailureCounter) is the same building block as #524's step 1 — they share the exact same class. Implement once, use in both places.

[Lexus2016]

Decomposed into child issues:\n- #571 — shared utility\n- #572 — per-entry failure tracking in auxiliary client

[Lexus2016]

Rejected by evolution-analysis: duplicate — Already decomposed into child issues #571 and #572; those children cover the remaining work.