- `X-Mana-LLM-Resolved: <provider>/<model>` header on non-streaming
responses. Streaming clients read the same info from each chunk's
`model` field (SSE headers go out before the chain is walked).
- Three new Prometheus metrics: `mana_llm_alias_resolved_total{alias,
target}` (which concrete model an alias resolved to per request),
`mana_llm_fallback_total{from_model, to_model, reason}` (each
fallback transition), `mana_llm_provider_healthy{provider}` (gauge,
mirrors the circuit-breaker).
- New debug endpoints: `GET /v1/aliases` (registry inspection — chain
+ description per alias, useful for confirming SIGHUP reloads),
`GET /v1/health` (full per-provider liveness snapshot — failure
counter, last error, unhealthy-until backoff).
- `kill -HUP <pid>` reloads `aliases.yaml`. Parse errors leave the
previous good state in memory and log the rejection.
- `ProviderHealthCache.add_listener()` for cache→metrics decoupling:
the gauge is updated via a transition-only listener wired in main.py
rather than the cache importing prometheus_client itself.
- Request-side metrics now use the requested model string, success-side
uses the resolved one. So `mana_llm_llm_requests_total{provider="ollama",
model="gemma3:12b"}` reflects actual upstream load even when callers
used `mana/long-form` aliases.
16 new observability tests (test_m4_observability.py): listener
fire-on-transition semantics, exception-isolation, multi-listener,
counter increments, gauge writes, end-to-end alias→metric flow,
v1/aliases + v1/health endpoint shape, response.model carries the
resolved target after fallback. Total suite: 115/115 in 1.6s.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
