forked from bchanot/claude
189 lines
10 KiB
Markdown
189 lines
10 KiB
Markdown
# Claude Code — Settings Rule Syntax
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## Rule syntax
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### Bash
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```json
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"Bash(git status)" // exact match
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"Bash(npm run test:*)" // wildcard suffix
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"Bash(git push*)" // prefix match
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"Bash(curl * | bash)" // pipe pattern — block code injection
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```
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### Read / Edit — gitignore syntax
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```json
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"Read(**/.env)" // any .env in any subdirectory
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"Read(**/secrets/**)" // anything inside secrets/
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"Read(src/**/*.ts)" // all .ts under src/
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"Edit(**/*.key)" // deny writing any .key file — Edit covers
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// Write/Edit/MultiEdit/NotebookEdit
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```
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`Write(path)` rules are **inert**: file permission checks only match
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`Edit(path)`. Claude Code warns at startup for every `Write(glob)` rule.
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Always write the file-write ban as `Edit(...)`.
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### WebFetch / WebSearch
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```json
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"WebFetch(domain:docs.rs)" // specific domain only
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"WebFetch" // all web fetches
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"WebSearch" // no sub-patterns supported
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```
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### Agent / Skill / MCP
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```json
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"Agent(explorer)"
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"Skill(deploy *)"
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"mcp__github__*" // all tools from github MCP server
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```
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## defaultMode values
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| Value | Behavior | When to use |
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|---|---|---|
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| `default` | Prompts on first use of each tool | Normal development |
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| `acceptEdits` | Auto-accepts file edits, prompts for Bash | Trusting sessions |
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| `plan` | Read-only — Claude plans, cannot execute | Code review, audit |
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| `auto` | Research preview — agentic default, permission model evolving. This config's default (BDR-004) | Daily driving with guardrails |
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| `bypassPermissions` | Skips all prompts — **dangerous** | CI/CD only, sandboxed env |
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## Auto mode (`autoMode`)
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With `defaultMode: auto`, a classifier decides each action instead of a static
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prompt. The `autoMode` block is what you hand that classifier.
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| Key | What it holds |
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|---|---|
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| `environment` | Facts about the machine and the repo. Context, not rules. |
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| `allow` | Action classes the classifier may clear on its own. |
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| `soft_deny` | Destructive or irreversible actions. Explicit user intent clears them. |
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| `hard_deny` | Security boundaries. User intent does **not** clear them. |
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| `classifyAllShell` | `true` suspends every Bash allow rule so all shell goes through the classifier. |
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All four lists are prose spliced into the classifier prompt, not permission-rule
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syntax. Write `Sending SIGKILL reaches processes outside this session`, not
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`Bash(kill -9 *)`.
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### `$defaults`
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Each list **replaces** the built-in entries unless it contains the literal
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string `"$defaults"`, which splices them in at that position. Put it first and
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your own entries refine what follows. Omit it and you silently drop every
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built-in rule, which is almost never the intent.
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### Scope it right
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`autoMode` in `~/.claude/settings.json` reaches **every** project on the
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machine. Project facts (this repo's deploy target, its secrets, its data)
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belong in that project's `.claude/settings.local.json`. A global block naming
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one repo feeds the classifier false facts in all the others.
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### `ask` is not a prompt under auto mode
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Verified in-session (LRN-146, re-verified on 2.1.273 on 2026-09-16 with a
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`node -e` probe matching an `ask` rule): with `defaultMode: auto`, Bash rules
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in `permissions.ask` were auto-approved and raised no prompt. The auto-mode
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docs claim the opposite for "content-scoped" rules such as `Bash(git push *)`;
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the observed behavior wins until a probe shows a prompt. `deny` is the only
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tier the classifier cannot lift.
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So for a destructive command you want gated but still reachable, `ask` is the
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wrong tier. Use `autoMode.soft_deny`: blocked until the user's intent clears
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it. Keep `deny` for what must never run at all.
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### Picking a tier
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| You want | Tier |
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|---|---|
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| Never runs, no exception, matchable by a command pattern | `permissions.deny` |
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| Never runs, and a pattern cannot express it (a read then a send, a prod target) | `autoMode.hard_deny` |
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| Runs when the user asks for it, blocked otherwise | `autoMode.soft_deny` |
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| Runs freely when a condition holds that only the classifier can judge (a local dev container, a package declared in the lockfile) | `autoMode.allow` |
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| Runs freely | `permissions.allow`, or nothing |
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`permissions.ask` is not on this list on purpose. Under `defaultMode: auto` it
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gates nothing.
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`autoMode.allow` is the exception tier: inside the classifier an `allow` entry
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overrides a matching `soft_deny`, built-in or yours, so word it as narrowly as
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the condition allows. It is also the only tier that can open an interpreter:
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under auto mode Claude Code suspends the static allow rules that grant
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arbitrary code execution (`Bash(*)`, wildcarded interpreters such as
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`Bash(node *)`), so those commands reach the classifier whatever
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`permissions.allow` says. `awk` and `echo` pass through a static rule; `node`
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cannot.
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### Package installs
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Global npm installs run their install scripts with your rights on the whole machine. `npm install -g`, `npm i -g` and their `--global` spellings are in `permissions.deny`. An `autoMode.soft_deny` entry catches every other spelling (a flag after the package name, `npm add -g`) and holds the install until you name the package in the current turn, after Claude states its publisher, age, download volume, install scripts and known advisories. A second `soft_deny` entry covers `npx`, `pnpm dlx` and `yarn dlx` of a package absent from the manifest and lockfile. Project-local scripts and declared packages pass through `autoMode.allow`.
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### Scope of intent
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A `soft_deny` clears on the user's instruction, and this config scopes that to
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the **current turn**. An approval from an earlier turn is not an approval now.
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State the scope in the rules themselves: the classifier reads the list, it has
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no separate setting for this.
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## Security notes
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- `Read(**/.env)` only blocks the Read tool. `Bash(cat .env)` bypasses it unless separately denied.
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→ Use `.claudeignore` for hard file exclusion regardless of tool.
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- `disableBypassPermissionsMode: "disable"` prevents switching to bypass mode mid-session.
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- Prefer `autoMode.soft_deny` over `allow` for anything touching external systems.
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- `deny` in `~/.claude/settings.json` cannot be overridden by project-level `allow` — deny always wins.
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- Under `defaultMode: auto`, `ask` does not raise a prompt (see above). A destructive
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command belongs in `deny` or in `autoMode.soft_deny`, not in `ask`.
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## Data-loss guardrails (BDR-095)
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Written after the 2026-09-21 wipe: a sub-agent traced `lftp mirror --delete`
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against a local `file://` path; the prose tiers named neither lftp nor a
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local trace, and the brief had authorized it. What holds now, by tier:
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| Class | Where | Why that tier |
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|---|---|---|
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| Transfer and mirror tools (`lftp`, `sftp`, `ftp`, `curl -T`), `rsync --delete`, `xargs rm`, pipe-to-shell | `permissions.deny` | Never needed in a session: Claude explains a deploy, the user runs it. Static, so it resolves before the classifier and inside sub-agents. |
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| `chmod`/`chown -R`, `sudo`/`doas`/`pkexec`, disk tools (`dd`, `mkfs`, `shred`…), `chattr` | `permissions.deny` | The user runs them by hand. |
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| Docker volume drops, `system prune`, `compose down -v`, `--privileged`, the docker socket, `-v /:` | `permissions.deny` | Promoted from `soft_deny`: no in-session clearance for data drops. |
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| Git history destruction (`push --delete`/`--mirror`/`:ref`/`--force-with-lease`, `branch -D`, `filter-branch`, `reflog expire`, `stash clear`/`drop`, `clean -f`), `--no-verify`, `core.hooksPath` | `permissions.deny` | A remote is the backup; nothing rewrites or deletes what it holds. |
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| Destructive tool against a local path (variable, `~`, `..`, wildcard, outside cwd/tmp), even as a trace or a rehearsal a brief allows | `autoMode.hard_deny` | A pattern cannot express "the target resolves outside the project"; the classifier can. A sub-agent brief carries no user authority. |
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| `docker rm -f`, bind mount outside cwd; discarding uncommitted work | `autoMode.soft_deny` | Recoverable or user-intended in the turn. |
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Rules apply to sub-agents (auto mode is inherited) and to each segment of
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a compound command; a tool nested in another command (`docker compose run …
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lftp`) is not matched by a static rule. The PreToolUse guard hook that scans
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the whole command, its executable spec in `lib/tests/guard-bash.test.sh`,
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is not shipped yet (BLK-022).
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Push discipline lives in `lib/gitflow.sh`: `start` pushes the branch,
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`finish` pushes each merge target, and the post-commit / post-merge hooks
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push every commit as it lands (warn, never block, on failure). `finish`
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deletes the merged branch through `gitflow_delete`, which refuses
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`main`/`develop` and any branch not merged into develop or main (`git branch
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-d` alone proves nothing once the branch has an auto-pushed upstream), then
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removes the `origin/` copy once its tip passes the same check (best effort:
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unreachable origin or an unmerged remote tip keeps it, loudly). A
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fourth hook, `reference-transaction`, vetoes any deletion or rename of
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`main`/`develop` at the ref layer. The hooks
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reach every repo two ways: `make link` generates `githooks/` from the lib
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and sets git's global `core.hooksPath` to `~/.claude/githooks` (a repo's own
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local `core.hooksPath` wins, by git's rules), and `hooks/session-start.sh`
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refreshes a repo's `.githooks/` when it lags the lib. Per-repo opt-outs, set
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by a human: `git config gitflow.protect false` (branch model, foreign clone)
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and `git config gitflow.autopush false` (manual-push mode: the hooks,
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`start` and `finish` push nothing, and `delete` leaves the `origin/` copy in
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place, printing the command to remove it by hand); `GITFLOW_NO_PUSH=1` for
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one command in a throwaway repo. `start` and `finish` warn when a base is
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behind origin and cannot fast-forward. `make doctor` checks the global
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setting and the generated dir. `hooks/unpushed-guard.sh` reports a branch
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ahead of its upstream at session start and at each turn end; in manual-push
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mode it stays silent at turn end and gives one `ℹ manual push mode:` line at
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session start, counting unpushed commits across every local branch.
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## managed-settings.json (enterprise)
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| OS | Path |
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| Windows | `C:\ProgramData\ClaudeCode\managed-settings.json` |
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| macOS | `/Library/Application Support/ClaudeCode/managed-settings.json` |
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| Linux | `/etc/claude-code/managed-settings.json` |
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