Run it locally

Prefer containers?

This page runs Zimmer as host processes and expects you to supply Postgres and Redis. To run the whole stack in Docker instead — no host Ruby, Postgres, or Redis — see Run it in containers.

Prerequisites

• Ruby 3.4.6 (see .ruby-version)
• PostgreSQL 14+
• Redis
• Node.js (for the AIR CLI and npx-based MCP servers)
• The claude and/or codex CLI, logged in
• gh CLI, logged in (agents use it to open PRs)

Setup

bundle install
cp .env.example .env          # then set ANTHROPIC_API_KEY
bin/rails db:setup
bin/dev                       # → http://localhost:3000

bin/setup does the same thing plus bundle check, db:prepare, and log:clear, then execs bin/dev. Use PORT=0 bin/dev for a random port.

bin/dev installs foreman if it’s missing, warns (non-fatally) if redis-cli ping fails, kills any stale foreman or port-3000 processes, and starts Procfile.dev:

web: bin/rails server
css: while true; do bin/rails tailwindcss:watch || sleep 5; done

There is no worker line in Procfile.dev — that’s correct

In development, GoodJob runs in :async mode in-process with Puma (config/environments/development.rb). Jobs and cron work.

In production and staging, execution_mode = :external and a separate bundle exec good_job start process is required — which the Kamal deploy runs as a dedicated worker role.

Two databases

config/database.yml and config/cable.yml expect two databases per environment: zimmer_development and zimmer_development_cable. The second is Action Cable’s, via solid_cable. bin/rails db:setup creates both.

Environment variables

Everything in .env.example is commented out except RAILS_ENV=development. The ones that matter:

Var	What for
DATABASE_HOST / _PORT / _USERNAME / _PASSWORD	Postgres. Postgres.app users want 5450.
REDIS_URL	Cache. redis://localhost:6379
ANTHROPIC_API_KEY	Claude Code, if not using OAuth
API_KEYS	Comma-separated keys for the REST API. Unset ⇒ the API 401s on everything.
APP_HOST	The MCP OAuth redirect host. Unset ⇒ defaults to localhost:3000.
RAILS_MASTER_KEY	Unlocks Rails credentials (mcp_secrets, mcp_oauth_clients)
AIR_CONFIG	Override which air.json the catalog resolves from
AGENT_CLONES_DIR	Where session clones go. Default ~/.zimmer/clones
GOOD_JOB_AGENTS_THREADS	Worker concurrency: how many agent sessions run at once. It also moves the database pool that has to serve them — see the connection budget

gh and the agent CLIs authenticate via OAuth (gh auth login, claude /login), not env vars.

First run: the catalog

On boot, config/initializers/air_catalog.rb runs AirCatalogService.refresh!, which lazily npm installs the AIR CLI (pinned to 0.13.0) into AIR_INSTALL_DIR and then shells out to air resolve. The first boot is slow because of that install.

If the catalog fails to resolve, the app downgrades to a warning and serves a stale snapshot — but the test suite is less forgiving. See below.

Running tests

bin/rails test test/models/session_test.rb    # targeted — do this
bin/rails test                                # the whole suite
bin/rubocop                                   # lint
bin/brakeman                                  # security scan

Run targeted tests locally and let CI run the full suite.

If the whole suite suddenly goes red, suspect the catalog

test/test_helper.rb pre-warms the AIR catalog at boot, before parallelize forks its workers. So a catalog that doesn’t resolve reddens every session-creating test at once, with ActiveRecord::RecordInvalid.

A wave of RecordInvalid across unrelated session tests almost always means a broken catalog. Check air resolve before you debug your change.

The browser suite runs in CI

.github/workflows/ci.yml runs the Chrome-driven system suite (test/system/*.rb) in a dedicated test-system job, alongside the unit + integration test-unit job. The JavaScript Playwright scripts under test/e2e/*.js are the one browser layer still not wired in (issue #162) — see Testing philosophy.