# CLAUDE.md

Concise guidance for agents working in this repository.

## Project

ComputerCraft / CC:Tweaked Lua APIs, servers, and programs for Minecraft 1.21. Code runs in the ComputerCraft sandbox, not standard Lua.

Use `docs/README.md` as the entrypoint for CC:Tweaked, CraftOS-PC, Advanced Peripherals, and Create integration documentation links. Use `docs/adrs/README.md` for repository architecture decisions.

## Constraints

- Do not add a standalone Lua test harness unless asked. Local execution happens through the CraftOS-PC harness (see `docs/install-craftos-pc.md`, `docs/craftos_pc_glossary.md`, and ADR-0005); code otherwise executes in-game.
- Do not run `just repl` as an LLM agent; it is a human-only interactive CraftOS-PC wrapper. Use `just trapos --headless --exec '<lua>; os.shutdown()'` for automated probes against the TrapOS dev environment, or `just craftos --headless --exec '<lua>; os.shutdown()'` for probes against vanilla CraftOS (no TrapOS mounts). Headless probes are the recommended way to verify hypotheses about CC:Tweaked behavior; see ADR-0012.
- When changing behavior, add as many useful CraftOS-PC tests as practical. It is acceptable to skip tests that require human-only validation, such as complex turtle motion, in-game UX feel, or visual approval, but still add unit-style non-regression tests for deterministic parts when possible.
- Use `/apis/libtest.lua` for test scripts under `tests/`; `/programs/runtest.lua` prints `__TRAPOS_TEST_OK__` only after the suite passes.
- `libtest` cancels each case after `3`s (`--timeout <s>` / `--no-timeout` to override); never commit a hanging test to `tests/`. Slow harness fixtures go in `tests/harness/` behind dedicated recipes. See `docs/adrs/adr-0009-layered-test-timeouts.md`.
- Git hooks own commit/push verification: pre-commit runs `just check test`, and pre-push runs `just ci`. When explicitly asked to commit and/or push, do not run `just test` manually first; rely on the hooks. See `docs/adrs/adr-0011-git-hooks-own-commit-push-verification.md`.
- After editing Lua or Markdown, run `just check` and fix all `luacheck` warnings and `lychee` broken-link reports (markdown link validation is offline-only via `just lint-markdown`).
- Use 2-space indent, semicolons, and `local function`.
- `require` paths are absolute ComputerCraft paths, for example `require('/apis/net')()`.
- Most API modules return factories; call the required module once before use.

## Architecture

- `apis/eventloop.lua` is the single-threaded event loop around `os.pullEventRaw`; consider using it everywhere async behavior is needed. A handler that returns `api.STOP` auto-unregisters.
- `apis/libtest.lua` is the lightweight test helper used by scripts under `tests/`; `/programs/runtest.lua` discovers tests, renders suite output, and owns the `__TRAPOS_TEST_OK__` success marker.
- `apis/net.lua` builds modem packet messaging, routing, and request/response RPC on the event loop. `sendRequest` returns `ok, result, packet` and defaults to a 0.5s timeout.
- A router (`/programs/router.lua`) must be running somewhere on the network; without it, packets lack `routerId`, `isPacketOk` rejects them, and cross-machine messaging silently fails.
- `servers/` listen for requests and start loops; `programs/` are clients that send requests and exit.
- Well-known channels: `9` ping, `10` router/default routing. Keep duplicated constants in sync.

## Boot And Install

- `startup/servers.lua` starts `/programs`, the shell, and configured servers via `parallel.waitForAll`.
- Preserve `periphemu` guards used for CraftOS-PC emulation; see `docs/craftos_pc_glossary.md` for upstream emulator references.
- TrapOS ships as packages, each described by `packages/<name>/ccpm.json` (`name`, `version`, `dependencies`, `files`, `autostart`); `packages/index.json` lists them. Source files stay in place — descriptors only reference them. To ship a new file, add it to the right package's `files` (and `autostart` if it is a server). `packages/trapos/ccpm.json` is the full OS meta-package. See ADR-0010.
- `install-ccpm.lua` is the one-time wget bootstrap. It installs only `tos-core`/`ccpm`, seeds the default `guillaumearm/cc-libs` registry on `master` (or `next` with `--beta`), and tells users to run `ccpm update` then `ccpm install trapos`.
- `ccpm` (in `tos-core`) is the package manager: `apis/libccpm.lua` is the testable core (factory with injectable `http`/`stateDir`/`installRoot`), `programs/ccpm.lua` the CLI. State: `/trapos/ccpm.json` (registries), `/trapos/ccpm.lock.json` (installed packages), and `/trapos/ccpm.cache.json` (available packages from `ccpm update`). Never use the word "manifest" in ccpm — it is reserved for the OS manifest.
- Add new servers to `startup/servers.lua` as needed.

## Conventions

- Bump `local _VERSION = '...'` when changing module behavior.
- Programs support `-version`/`--version` and `-help`/`--help`; router also supports `-silent`/`--silent`.
- French or English comments are fine; match surrounding code.
- Commit messages use lightweight conventional style: `topic(scope): description` or `topic: description`.

See `DEVELOPMENT.md` for local setup.