Feature: Observability — timing and metrics for performance and UX (ADR-030, #15)
  As the maintainer running Tapir for pilot users
  I want timing and Prometheus metrics for the activities that drive performance and UX
  So that I can see latency, model behaviour, and usage — and feed the Stage-0 eval gate

  # AI metrics are the priority (ADR-030 R3). Each scenario maps to a Go test in
  # test/acceptance/scenario_coverage_test.go (the BDD name-coverage gate).

  Scenario: Summarization latency is recorded per endpoint
    Given the summarizer runs a transcript through its endpoint chain
    When an endpoint returns a parseable summary
    Then the summarize latency is recorded with the model, outcome "success", and whether it was a fallback

  Scenario: A failing summarizer endpoint records its failure outcome
    Given the summarizer runs a transcript through its endpoint chain
    When an endpoint errors or returns unparseable output
    Then the summarize latency is recorded with outcome "error" or "parse_error" before the chain advances

  Scenario: Caption fetch latency is recorded by outcome
    Given a caption fetch is attempted for a video
    When it resolves to captions, no captions, or a rate limit
    Then the caption-fetch latency is recorded labelled by that outcome

  Scenario: LLM token usage is recorded from the completion
    Given an LLM completion returns a usage block with prompt and completion tokens
    When the client finishes the call
    Then the prompt and completion tokens are recorded for that model

  Scenario: Q&A answer latency is recorded
    Given a user asks a question about a video
    When the answer is produced from the stored transcript
    Then the chat answer latency is recorded for the answering model

  Scenario: HTTP requests are counted by route, method, and status
    Given the metrics HTTP middleware wraps the app
    When a request is served against a registered route
    Then it is counted and timed under the bounded route pattern, not the raw path

  Scenario: A successful login is counted
    Given a user completes the OIDC callback and a session is established
    Then the login counter is incremented

  Scenario: The metrics endpoint is not on the public app port
    Given the service is running
    When the public app mux is inspected
    Then it exposes no /metrics route — metrics are served on the dedicated metrics port only