# W-B — Measure Pi's real tool registry

- **Task / internal ref:** W-B from the lease-remediation orchestrator brief (no matching `docs/TASKS.md` row; workers do not modify that file)
- **Objective:** identify the exact tool names emitted as `event.toolName` by the installed Pi runtime and compare them with the broker's Pi read-only carve-out.
- **Scope:** measurement and report only; no broker or runtime source changes. W-C is out of scope.
- **Budget:** no explicit token cap; constrained to this scratchpad and one local commit.
- **Installed runtime:** `@earendil-works/pi-coding-agent` / `pi` `0.84.1`.

## Method

I created a throwaway extension at `/tmp/measure-pi-tool-registry.ts` (not in the worktree). On `session_start` it recorded `pi.getAllTools()` and `pi.getActiveTools()`; on every `tool_call` it appended the exact `event.toolName`. I then launched an isolated, ephemeral Pi session with all built-ins explicitly selected:

```text
PI_OFFLINE=1 pi --mode print --no-session --no-approve \
  --no-context-files --no-skills --no-prompt-templates --no-extensions \
  -e /tmp/measure-pi-tool-registry.ts \
  --tools read,bash,edit,write,grep,find,ls <deterministic probe prompt>
```

The prompt exercised file read, content search, file search, directory listing, shell execution, file write, and file edit. Pi exited `0`; every selected tool produced one `tool_call`. The write/edit control artifact ended with exact content `after`, proving the mutating calls executed in order.

This runtime observation was cross-checked against the installed distribution's canonical registry at `dist/core/tools/index.js:17`, which declares the same seven names. The gate consumes the measured field directly at `packages/mosaic/framework/runtime/pi/mosaic-extension.ts:368`.

## Exact distinct built-in set

The installed Pi built-in registry is exactly:

```text
{bash, edit, find, grep, ls, read, write}
```

| Tool | Runtime registry observation | `tool_call` observation | Installed definition |
| --- | --- | --- | --- |
| `read` | `<builtin:read>` | observed once | `dist/core/tools/read.js:138` |
| `bash` | `<builtin:bash>` | observed once | `dist/core/tools/bash.js:231` |
| `edit` | `<builtin:edit>` | observed once | `dist/core/tools/edit.js:170` |
| `write` | `<builtin:write>` | observed once | `dist/core/tools/write.js:138` |
| `grep` | `<builtin:grep>` | observed once | `dist/core/tools/grep.js:79` |
| `find` | `<builtin:find>` | observed once | `dist/core/tools/find.js:79` |
| `ls` | `<builtin:ls>` | observed once | `dist/core/tools/ls.js:61` |

The raw distinct `event.toolName` result was:

```json
["bash", "edit", "find", "grep", "ls", "read", "write"]
```

Pi registers all seven, but its default active set is only `read`, `bash`, `edit`, and `write` (`dist/core/sdk.js:132`). The probe explicitly activated all seven so the three search/list tools could be observed at the hook.

## Positive control

The known `read` tool was the control. The method surfaced it twice:

1. `pi.getAllTools()` returned `read` with source path `<builtin:read>`.
2. Reading `/tmp/pi-registry-probe/seed.txt`, which contained `CONTROL_TOKEN`, produced one hook record with `event.toolName === "read"`.

The control was therefore positive; the seven-name result is measured, not an empty-probe inference.

## Carve-out comparison and collision result

The broker currently declares `{"read", "grep", "find", "ls"}` at `packages/mosaic/framework/tools/lease-broker/daemon.py:54`.

- `read`: real built-in.
- `grep`: real built-in.
- `find`: real built-in.
- `ls`: real built-in.

All four carve-out names are exact, case-sensitive Pi tool names.

The general execution/writing tool names are `bash`, `edit`, and `write`. Their intersection with the carve-out is empty:

```text
{bash, edit, write} ∩ {read, grep, find, ls} = ∅
```

Therefore no general shell-exec or file-mutating Pi tool shares a name with a carve-out entry. `grep` and `find` may invoke constrained search helpers internally, but neither exposes an arbitrary command interface; the arbitrary command tool is distinctly named `bash`.

The Mosaic extension separately registers the non-built-in custom tool `mosaic_context_recover` at `packages/mosaic/framework/runtime/pi/mosaic-extension.ts:379`; the broker handles that identity through its dedicated recovery exemption rather than the read-only set (`daemon.py:722`). Unknown or third-party custom tools are not part of Pi's built-in seven-name registry and remain outside the carve-out.

## Verification evidence

- `pi --version` → `0.84.1`.
- Isolated probe exit → `0`.
- Runtime `getAllTools()` count → `7`, all with `sourceInfo.source === "builtin"`.
- Distinct hook names → `bash`, `edit`, `find`, `grep`, `ls`, `read`, `write`.
- Hook counts → exactly one call for each of the seven names.
- Mutation artifact after `write` then `edit` → exact content `after`.
- Installed registry source → `allToolNames = new Set(["read", "bash", "edit", "write", "grep", "find", "ls"])`.

## Risks / limitations

- The probe deliberately disabled all other extensions, so extension-defined third-party tools were excluded from the built-in registry measurement. The production gate still receives those names and treats names outside the broker carve-out as mutating/fail-closed.
- Explicit `--tools` activation was required to exercise `grep`, `find`, and `ls`; this does not imply they are active in Pi's default four-tool configuration.
