feat(telemetry): expose Prometheus metrics

CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Request IDs are now added to router responses and structured logs.
 - Streaming backend responses now log first event latency and usage tokens when
   the backend sends OpenAI-compatible streamed usage chunks.
+- `/metrics` now exposes Prometheus-compatible request, queue, latency, byte,
+  and token telemetry.
 
 ### Changed
 

README.md

@@ -19,6 +19,7 @@ This repository is in early foundation work. The current service supports:
 
 - a small Go HTTP service
 - `/healthz`
+- `/metrics`
 - `/v1/models`
 - OpenAI-compatible `/v1/*` request proxying
 - model alias rewriting
@@ -29,6 +30,8 @@ This repository is in early foundation work. The current service supports:
 - Docker image and Compose smoke testing with a mock OpenAI-compatible backend
 - response telemetry for proxied backend calls
 - streaming response telemetry for first event latency and streamed usage data
+- Prometheus-compatible metrics for requests, queue wait, response latency,
+  first event latency, bytes, and token totals
 - consistent OpenAI-shaped errors for router-side failures
 - request IDs in router responses and logs
 

docs/roadmap.md

@@ -23,11 +23,14 @@ This phase makes one local backend dependable for day-to-day tools such as
 opencode, OpenClaw, and Hermes.
 
 - Stable `/healthz` and `/v1/models` endpoints.
+- Prometheus-compatible `/metrics` endpoint.
 - Alias-to-target model rewriting.
 - Bounded per-alias queueing and concurrency limits.
 - Command-backed profile ensure hooks for LM Studio and similar hosts.
 - Response telemetry for route, status, duration, bytes, and usage tokens.
 - Streaming telemetry for first event latency and streamed usage chunks.
+- Metrics for request counts, queue waits, request duration, streamed first
+  event latency, response bytes, and token totals.
 - Linux tarball packaging with systemd installation.
 - Docker and Vagrant smoke tests.
 - Consistent OpenAI-shaped router errors.
@@ -66,6 +69,7 @@ vibe-based.
 - Structured request logs with request ID, alias, target model, upstream model,
   queue wait, ensure duration, first-token latency, total duration, status, and
   token usage.
+- Grafana-ready Prometheus metrics and starter dashboards for local operators.
 - Optional local JSONL telemetry sink for offline analysis.
 - Small repeatable eval harness for real agent workflows:
   - commit hook failure handling
@@ -100,7 +104,8 @@ This phase turns the router from a lab service into durable local infrastructure
 - Auth for non-loopback deployments.
 - Rate limits by client, alias, or token.
 - Admin endpoint or CLI for draining, reloading config, and inspecting state.
-- Prometheus metrics.
+- Expanded Prometheus metrics for backend lifecycle, adapter state, and client
+  rate limiting.
 - Signed release artifacts and package repository support.
 - Upgrade and rollback runbooks.
 - Omarchy and desktop integration profiles.