An Effect stack so pure (aspirational) Kit Langton will blush.

Build an Effect app and its cloud as one typed program. Joel's goal is the best Effect + Alchemy application we can build; VISION.md explains why. AGENTS.md sets exact pins, checks, and hooks. The public tree lets you steal ideas. It carries no product support promise.

The pnpm + Turborepo workspace includes a working Effect v4 CLI, tests, formatting, and type-aware linting. Vendored source mirrors cover Effect, effect-solutions, XState, and Alchemy.

Define a Contract with Effect input, output, and failure schemas plus annotations. Bind a server-side handler, then project the capability onto every agent surface. The same inspectFile capability is the stats command, POST /inspectFile with an OpenAPI document, and an MCP tool over stdio.

gh repo create <name> --template joelhooks/rat-stack

Clone the new repository, then install and verify it:

nvm use
pnpm install
pnpm vendor:agent-sources
pnpm turbo run check test build

Node 24.18.0 and pnpm 11.3.0 are required. The requirement is declared in .nvmrc, engines, devEngines, and packageManager.

• apps/cli:
  • Package: @rat-stack/cli
  • Role: Composition root: stats, openapi, serve, mcp
• packages/capability:
  • Package: @rat-stack/capability
  • Role: defineContract, implement, and the toCommand, toHttpApi, toToolkit, toRpc, and toCodeMode projections
• packages/core:
  • Package: @rat-stack/core
  • Role: Domain example: the inspectFile contract, handler, and lifecycle machine
• packages/flags:
  • Package: @rat-stack/flags
  • Role: Typed flags, Config, memory and KV adapters, stable rollouts, audited writes, and removal dates
• packages/events:
  • Package: @rat-stack/events
  • Role: Request analytics: capture, visitor privacy rules, and Basin resources behind core's EventSink port
• packages/crash:
  • Package: @rat-stack/crash
  • Role: Private crash-trace archive for the Mischief Worker
• packages/lore:
  • Package: @rat-stack/lore
  • Role: Public content graph and traversal service
• packages/subscriber-delivery:
  • Package: @rat-stack/subscriber-delivery
  • Role: External subscriber intake and confirmation adapter behind core's job-shaped ports
• apps/infra:
  • Package: @rat-stack/infra
  • Role: Alchemy Stack (Cloudflare by default)
• apps/site:
  • Package: @rat-stack/site
  • Role: Cloudflare Worker for the public site, agent discovery, and sandboxed execute
• .agent_sources/:
  • Package: —
  • Role: Shallow upstream mirrors (gitignored clones; see README there)

The included stats command counts bytes, Unicode characters, words, and lines in a file:

pnpm cli stats README.md
pnpm cli stats README.md --json

After pnpm build, you can run the built entrypoint directly:

node apps/cli/dist/cli.js stats README.md

The same capability on the other surfaces:

pnpm cli openapi                 # OpenAPI 3.1 document for the REST projection
pnpm cli serve --port 3000       # POST /inspectFile, GET /openapi.json, GET /docs
pnpm cli mcp                     # MCP server over stdio, one tool per capability
pnpm cli mcp --code-mode         # MCP server with two tools: search and execute
pnpm cli catalog --types         # the `tools` declarations a code-mode program sees

Code mode is the fourth projection. The model gets search for ranked matches with TypeScript signatures and execute for JavaScript with tools in scope. The program runs in a fresh Node subprocess under --permission. It cannot touch the file system or spawn processes. To call the host, it uses tools.<name>(input). The host validates the input schema and runs the same handler used by every other surface. Node's permission model allows network egress. Put a Worker or Deno runtime behind the same Sandbox service to isolate the network too.

packages/capability/src is where a capability becomes a Command, an HttpApiEndpoint, a Tool, and a catalog entry. packages/core/src/inspect-file.ts supplies the CLI's example capability. Hosted content has its own registry in apps/site/src/capabilities/index.ts. Provider adapters stay outside core (rat-stack-boundaries/no-core-adapters); apps provide them to core's job-shaped ports at composition. Add another to capabilities, then verify every projection you keep; CLI command registration lives in apps/cli/src/command.ts.

• pnpm workspaces + Turborepo 2.11.9: cached typecheck / test / build across packages from day one.
• Effect 4.0.6: typed runtime, errors, filesystem service, and the three surfaces the capabilities project onto: effect/cli, effect/http-api (with OpenApi.fromApi), and effect/ai (Toolkit + McpServer).
• @effect/platform-node 4.0.6: Node-backed services; keep adapter and core pins matched.
• TypeScript 7.0.2: strict module and index-access checks.
• @yielded/effect-tsrs 0.2.2: runs TypeScript and Effect diagnostics in typecheck and check. --type-check includes ordinary TypeScript diagnostics; --strict makes Effect warnings fail. It bundles tsrs 8f135f106a63, contained in plain tsrs 0.20.0.
• tsrs 0.20.0-ts7.1.0-beta: experimental compiler targeting TypeScript 7.1.0-beta for typecheck:fast. It still has no Effect diagnostics; use typecheck or check for those.
• XState 6.0.0-alpha.70: real lifecycle states; do not replace those with boolean soup.
• @xstate/effect 1.0.0-alpha.9: the official XState v6 to Effect 4 bridge: createEffectActor runs a machine as a scoped Effect, createEffectLogic makes Effects into actors with typed failures and requirements. packages/core/src/inspect-machine.ts is the example.
• Alchemy 2.0.0-beta.84: Infrastructure as Effects: apps/infra/alchemy.run.ts is the Stack; cloud providers come from @alchemy.run/cloudflare, @alchemy.run/drizzle, and @alchemy.run/sql; pnpm infra:plan / infra:deploy / infra:destroy; auth via pnpm alchemy profile edit.
• Foldkit 0.169.0 + @foldkit/vite-plugin 0.28.0: the web UI. Server rendering and prerendering are on by default. One vite build writes the browser bundle, a server fetch function, and an HTML file for every public page. Cloudflare.Website.Foldkit serves the files and sends every other request to that function. The browser hydrates the same view. .brain/areas/web.svx is the system page.
• Oxlint + Ultracite + Oxfmt: native lint and format.
• Vitest 5.0.5 + @effect/vitest 4.0.6: it.effect and it.layer for every Effect test; running Effects by hand in a test file is a lint error.
• @effect/tsgo 0.55.0: patches TypeScript 7 in prepare for typecheck:tsc. Effect warnings fail because ignoreEffectWarningsInTscExitCode stays false. Patched tsc runs at the switch and on checker bumps through parity, not on every CI run. Report any checker disagreement.
• varlock 1.23.0: .env.schema declares every variable with @env-spec decorators; pnpm check runs varlock load, secrets stay in gitignored .env.local.
• Vendored agent sources: Effect, effect-solutions, XState, Alchemy, Better Auth, and Foldkit via ./scripts/vendor-agent-sources.sh, each at the ref its workspace pin names (not x-algorithm; that stays app-specific).
• Agent fence: lefthook pre-commit + Pi/Cursor/Claude hooks that block git … --no-verify. Cheating should be uncomfortable and obvious.

Every dependency is pinned exactly. Review pin upgrades as stack changes.

• pnpm typecheck: Check TypeScript and Effect diagnostics with strict effect-tsrs
• pnpm typecheck:tsc: Run patched TypeScript 7.0.2 / @effect/tsgo 0.55.0; runs at checker bumps, not in CI
• pnpm typecheck:fast: Fast feedback with tsrs; no Effect diagnostics; pnpm check stays the gate
• pnpm typecheck:parity: Compare effect-tsrs and patched tsc errors and exit verdicts, including TS377xxx; also compare plain tsrs with Effect-only codes excluded
• pnpm bump:checkers: Bump both exact checker pins to npm latest, report bundled revision alignment, and run both parity pairs
• pnpm check: Typecheck, check formatting, and run type-aware linting
• pnpm fix: Apply Oxfmt and safe Oxlint fixes
• pnpm test: Run the Vitest suite once
• pnpm build: Compile package outputs
• pnpm cli -- ...: Build and run the CLI
• pnpm vendor:agent-sources: Clone core lib mirrors
• pnpm turbo run check test build: Cached verification pipeline

Every clone includes AGENTS.md for repo law and commands, CLAUDE.md as Claude Code's pointer to that law, and VISION.md for project intent. Source mirrors live under .agent_sources/ after you run the vendor script. Repo-local Pi extensions belong in .pi/extensions/.

Start with the template:

gh repo create <name> --template joelhooks/rat-stack

Clone the new repository, then install it:

pnpm install
pnpm sources:fetch

pnpm sources:fetch imports missing pinned source commits from the configured repository remotes once, including in template children. Generation reads only local Git objects and never fetches. Re-run the command when adding a new pin that is not present locally.

Rename the workspace package names before you build on the example. The current name fields are:

• package.json: rat-stack
• apps/cli/package.json: @rat-stack/cli
• apps/infra/package.json: @rat-stack/infra
• apps/site/package.json: @rat-stack/site
• packages/capability/package.json: @rat-stack/capability
• packages/core/package.json: @rat-stack/core

Rename the bin entry in apps/cli/package.json, the root command in apps/cli/src/command.ts, and the version in apps/cli/src/version.ts. Then change every matching import. The current workspace imports are @rat-stack/capability, @rat-stack/cli, @rat-stack/core, @rat-stack/infra, and @rat-stack/site. Find them with:

rg -n '@rat-stack/' --glob '*.json' --glob '*.ts' -l

A new scope changes line lengths, so run the formatter once after the rename:

pnpm fix

Replace inspectFile in packages/core with one useful capability. Add it to capabilities, then verify each surface you keep. Rewrite the Project law, Architecture, and Boundaries sections of AGENTS.md and the top of .pi/APPEND_SYSTEM.md; they describe rat-stack until you do. Keep expected failures typed and map them to deliberate exit codes.

apps/site is the public site and Worker. apps/infra is its Alchemy Stack. Delete both if you do not want a public site. If you keep them, change the Cloudflare Zone name and the DNS names and targets derived from it in apps/infra/alchemy.run.ts. Change the Worker domain and redirects in apps/site/src/worker.ts. Choose an Alchemy stage for each plan or deploy. The stage is a command-line choice, for example --stage <stage>. Configure credentials with:

pnpm alchemy profile edit --add Cloudflare

Run the acceptance gate before the first push:

pnpm turbo run check test build

• One capability reaches every kept surface. Proof: packages/capability/test/to-command.test.ts, packages/capability/test/to-http-api.test.ts, packages/capability/test/to-toolkit.test.ts, packages/capability/test/to-code-mode.test.ts, and apps/cli/test/cli.e2e.test.ts.
• Schemas are the contract. Proof: packages/capability/test/catalog.test.ts, packages/capability/test/to-http-api.test.ts, and packages/capability/test/to-toolkit.test.ts check derived JSON Schema and typed failures.
• A fresh sandbox isolates model code. The Node sandbox has a 10-second wall-clock limit and a 1-second limit per synchronous evaluation. Both run inside the child. Scope close and interruption send SIGTERM, then SIGKILL after 250 milliseconds. Stdin EOF, a lost parent, or a failed protocol write ends the child. Child-process imports remain blocked. Proof: packages/capability/test/sandbox.test.ts checks isolation and VM budgets; sandbox-lifetime.test.ts and sandbox-orphan.test.ts check deadlines, parent death, and process-group cleanup.
• Rate limits fail closed. Proof: apps/site/test/worker.test.ts checks 429 responses before another execute worker starts and when the global limit denies.
• Markdown is the default machine representation. Proof: apps/site/test/worker.test.ts checks Markdown without Accept: text/html and HTML only when requested.

The template is a working project. Delete what you will not use on day one; the fence will identify dependent code that must go too. After each cut, trim packages/capability/src/index.ts and run pnpm install, pnpm fix, then pnpm turbo run check test build. Update the package list in AGENTS.md.

• Only the CLI:
  • Keep: packages/capability/src/contract.ts, packages/capability/src/implement.ts, packages/capability/src/to-command.ts, call-watch.ts, actor-watch.ts, every dependency imported by retained code, and their tests; all of packages/core; the toCommand composition in apps/cli/src/surfaces.ts
  • Delete: unused projections and their matching tests after tracing the retained imports; unused compositions in apps/cli/src/surfaces.ts; the catalog, openapi, serve, and mcp commands in apps/cli/src/command.ts; apps/cli/test/serve.test.ts and the MCP and catalog cases in apps/cli/test/cli.e2e.test.ts
• No code mode:
  • Delete: packages/capability/src/catalog.ts, packages/capability/src/code-mode.ts, packages/capability/src/sandbox-error.ts, packages/capability/src/sandbox-service.ts, packages/capability/src/sandbox-subprocess.ts, and packages/capability/src/to-code-mode.ts; packages/capability/test/catalog.test.ts, packages/capability/test/sandbox.test.ts, packages/capability/test/sandbox-lifetime.test.ts, packages/capability/test/sandbox-orphan.test.ts, packages/capability/scripts/sandbox-lifetime-proof.mjs, and packages/capability/test/to-code-mode.test.ts; the ./sandbox and ./code-mode exports in packages/capability/package.json; codeMode and mcpServer.codeMode in apps/cli/src/surfaces.ts; the catalog command and the --code-mode flag in apps/cli/src/command.ts; the code-mode and catalog cases in apps/cli/test/cli.e2e.test.ts
• No HTTP:
  • Delete: packages/capability/src/to-http-api.ts, packages/capability/src/http-api.ts, and their tests; the ./http-api export in packages/capability/package.json; http, routes, and webServer in apps/cli/src/surfaces.ts; the openapi and serve commands; apps/cli/test/serve.test.ts; the OpenAPI case in apps/cli/test/cli.e2e.test.ts
• No MCP:
  • Delete: packages/capability/src/to-toolkit.ts, packages/capability/src/toolkit.ts, their test, and packages/capability/test/mcp-harness.ts; the ./toolkit export in packages/capability/package.json; tools and mcpServer in apps/cli/src/surfaces.ts; the mcp command; the MCP cases in apps/cli/test/cli.e2e.test.ts. Code mode imports from packages/capability/src/to-toolkit.ts, so cutting MCP cuts code mode too
• Default flags only:
  • Keep: Core's Flags port and declarations
  • Delete: Replace apps/site/src/flags.ts with core imports and export const flagsLayer = Flags.defaults(eventFlags); export const liveFlagsLayer = flagsLayer;; remove packages/flags and its dependency in apps/site/package.json. Readers use defaults; the CLI writer fails with a named read-only error
• No analytics:
  • Delete: packages/events; the @rat-stack/events line in apps/site/package.json; the code excerpts that quote packages/events/test in .brain/resources/lore/tests-that-earn-their-place.svx and skills/test-behaviour/SKILL.md
  • Change: the one line in apps/site/src/events.ts becomes export { events, memoryEvents } from "@rat-stack/core/events-off";
  • Then: pnpm install, pnpm git-snapshot, and the gate
  • Optional: EVENTS_ENABLED, EVENTS_SINK_TOKEN, and EVENTS_IDENTITY_MODE in apps/site/.env.schema and apps/site/src/config-fingerprint.ts, and the events flags in packages/core/src/flags.ts. The Worker ignores them once capture is off. Details: packages/events/README.md
• No XState (only after removing interest and every other lifecycle except file inspection):
  • Keep: Keep XState and its bridge while any retained lifecycle imports them
  • Delete: packages/core/src/inspect-machine.ts and its test (call FileInspector.inspect directly from packages/core/src/inspect-file.ts); xstate and @xstate/effect in packages/core/package.json and their minimumReleaseAgeExclude entries in pnpm-workspace.yaml; scripts/oxlint-plugin-xstate-effect.ts and its entry in oxlint.config.ts

defineContract, implement, and toCommand are the minimum that keep stats working. The contract module has no dependency on the other projections.

MIT