Local Environment Skill

Helps manage the Polar local development environment through the dev docker CLI. Use it to start, stop, debug, or reason about the local stack.

The two-part model

dev docker deliberately splits the stack so many worktrees can share one set of heavy infra:

• Shared infra — one copy per machine, Docker project polar-shared: postgres, redis, minio, tinybird, and optional prometheus/grafana. Postgres and redis publish no host ports; MinIO exposes 9000/9001 for browser uploads. Use dev docker exec <service> ... for services without host ports.
• Per-instance app stack — one per worktree, project polar-app-<N>: api, worker, web. Only api and web publish host ports, offset per instance so worktrees don't collide.

Knowing this prevents the most common confusion: there is no localhost:5432 for the database (it lives in the shared stack and is reached through dev docker exec db ...). MinIO does expose ports 9000/9001 for browser uploads and console access.

Instance auto-detection

dev docker auto-detects the instance for the current worktree, so -i is rarely needed. Priority:

1. POLAR_DOCKER_INSTANCE pinned in dev/docker/.env.docker (dev docker set-instance N)
2. The cross-worktree registry (~/.config/polar/docker-instances.json)
3. Otherwise the lowest free number, then registered

Run dev docker ports to see the resolved instance and its URLs (add --json for tooling). To wire this worktree into Claude Code's preview, run dev docker launch-json, which writes a per-instance .claude/launch.json with the correct ports (it's gitignored, so regenerate after set-instance).

When to use

• Start / stop / restart the local environment
• View logs or debug a service that won't come up
• Run several isolated worktree instances in parallel
• Understand the service architecture or find a service's real port
• Diagnose container or first-boot errors

Quick reference

Task	Command
Start full stack (background)	dev docker up -d
Start and block until healthy	dev docker up -d --wait
Start in foreground (stream logs)	dev docker up --no-detach
Rebuild with fresh base images	dev docker up -b --pull -d
Show this instance's ports/URLs	dev docker ports (--json for tooling)
Write Claude Code preview config	dev docker launch-json
Stop app stack	dev docker down
Stop app and shared infra	dev docker down --all
Follow logs	dev docker logs -f [service]
Print logs and exit	dev docker logs --no-follow [service]
Status	dev docker ps
Restart a service	dev docker restart <service>
Shell into a service	dev docker shell <service>
One-off command in a service	dev docker exec <service> <cmd>
Reset this instance	dev docker cleanup -f
Wipe ALL shared data	dev docker cleanup --all -f
List every instance	dev docker list
With monitoring	dev docker up --monitoring -d

Services

Service	Project	Host port (instance 0 / N)	Notes
api	polar-app-<N>	8000 / 8100+N	FastAPI; /healthz healthcheck
web	polar-app-<N>	3000 / 3100+N	Next.js; healthchecked
worker	polar-app-<N>	none	Background jobs
db	polar-shared	none (exec)	PostgreSQL; DB polar_dev_<N>
redis	polar-shared	none (exec)	Redis DB index = N
minio	polar-shared	9000, 9001	S3; buckets polar-s3-<N>; console at 9001
tinybird	polar-shared	none (exec)	Analytics
prometheus / grafana	polar-shared	none (exec)	--monitoring only

Discover the exact host ports for the current worktree with dev docker ports.

Instance port mapping

Only api and web get host ports: Port = Base + Instance (Base 8100 for api, 3100 for web) for instances 1–99. Instance 0 uses the legacy 8000 / 3000.

Instance	API	Web
0	8000	3000
1	8101	3101
2	8102	3102
5	8105	3105

Everything else is per-instance but not on a host port: database polar_dev_<N>, redis DB index <N>, buckets polar-s3-<N> / polar-s3-public-<N>. Reach them via dev docker exec <service> or docker exec polar-shared-<service>-1.

Rules index

Rule	Category	Description
service-architecture	Reference	Service details, ports, healthchecks
start-environment	Operations	Starting the stack (flags, --wait, --pull)
stop-environment	Operations	Stopping and cleanup (app vs shared)
manage-instances	Operations	Parallel worktree instances
view-logs	Debugging	Viewing service logs
shell-and-workflows	Operations	Shell access and common dev workflows
troubleshooting	Debugging	Common errors and fixes
payment-testing	Operations	Login codes, Stripe webhooks, backoffice