Claude: production observability guidance (#1725)

CLAUDE.md

@@ -137,6 +137,43 @@ Key recurring tasks (via `config/recurring.yml`):
 - Search records denormalized for performance
 - Models in `app/models/search/`
 
+## Production Observability
+
+Grafana MCP tools provide access to production metrics and logs for performance analysis.
+
+### Datasources
+| Name | UID | Use |
+|------|-----|-----|
+| Thanos (Prometheus) | `PC96415006F908B67` | Metrics, latencies |
+| Loki | `e38bdfea-097e-47fa-a7ab-774fd2487741` | Application logs |
+
+### Key Metrics
+- `rails_request_duration_seconds_bucket:rate1m:sum_by_app:quantiles{app="fizzy"}` - Request latency percentiles
+- `rails_request_total:rate1m:sum_by_controller_action{app="fizzy"}` - Request rates by endpoint
+- `fizzy_replica_wait_seconds` - Database replica consistency wait times
+
+### Loki Log Labels
+Query: `{service_namespace="fizzy", deployment_environment_name="production", service_name="rails"}`
+
+Useful fields: `event_duration_ms`, `performance_time_db_ms`, `performance_time_cpu_ms`, `rails_endpoint`, `rails_controller`
+
+### Instrumentation
+Yabeda-based metrics exported at `:9394/metrics`. Config in `config/initializers/yabeda.rb`.
+
+### Chrome MCP (Local Dev)
+URL: `http://fizzy.localhost:3006`
+Login: david@37signals.com (passwordless magic link auth - check rails console for link)
+
+Use Chrome MCP tools to interact with the running dev app for UI testing and debugging.
+
+### Sentry Error Tracking
+Organization: `basecamp` | Project: `fizzy` | Region: `https://us.sentry.io`
+
+Use Sentry MCP tools to investigate production errors:
+- `search_issues` - Find grouped issues by natural language query
+- `get_issue_details` - Get full stacktrace and context for a specific issue
+- `analyze_issue_with_seer` - AI-powered root cause analysis with code fix suggestions
+
 ## Coding style
 
 Please read the separate file `STYLE.md` for some guidance on coding style.