diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 00000000000..bb0a21f21d4
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,60 @@
+# Lua-Modules
+
+## Running repository commands
+
+The toolchain can be installed natively or come from the devcontainer, and both
+are supported — see Setup in the README. Use whichever the machine already has
+rather than assuming one; a native setup is common on Linux, while the
+devcontainer saves a fight with Lua 5.1 on macOS.
+
+Check before running rather than guessing: `command -v busted luacheck ruff`,
+and `lua -v`, which needs to report 5.1. Anything newer is unsupported here, so
+its results do not mean much.
+
+With a native toolchain, or from a shell already inside the devcontainer, which
+you can tell from the workspace being under `/workspaces/`, run commands
+directly:
+
+```
+npm run lua-test
+```
+
+From the host with only the devcontainer set up, go through its CLI, starting
+the container first if it is not already up:
+
+```
+npx --yes @devcontainers/cli up --workspace-folder .
+npx --yes @devcontainers/cli exec --workspace-folder . npm run lua-test
+```
+
+If neither is available, say so instead of skipping a check or calling it
+passed. Installing the Lua tools natively is `luarocks install --lua-version=5.1
+busted`, and the same for `luacheck`; the devcontainer route needs Docker
+running.
+
+Say which of the two produced a result when it is not obvious. A native setup
+can differ from CI in Lua patch version or ruff version, and whoever reads the
+result should know which they got.
+
+## Commands
+
+- `npm run lua-test` — busted suite, builds the CSS first
+- `luacheck lua --config lua/.luacheckrc` — Lua lint
+- `npm run lint:scss` — SCSS lint
+- `npm run lint:js` — JS lint, note that it runs `eslint --fix` and edits files
+- `ruff check scripts/` and `ruff format --check scripts/` — Python
+- `npm run build` — CSS and JS bundles
+
+## Visual snapshots
+
+Do not update snapshots locally. CI regenerates them and commits them back to
+the branch, and reviewing that diff is part of reviewing the pull request.
+Rendering is not identical across CPU architectures, so a local update can
+produce changed files that are not real changes.
+
+## Deploying to the wiki
+
+`scripts/deploy.py` writes to liquipedia.net. Set `LUA_DEV_ENV_NAME` so it
+targets sandbox pages, and keep `DRY_RUN=1` unless the intent is a live write.
+With neither set, running it with no arguments resyncs every module to the live
+wiki.