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Retire mcp-loader.ts in favour of pi's built-in MCP support

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pi has had MCP as a built-in extension (builtin:mcp) since 0.99.0. It reads
~/.pi/agent/mcp.json and adds `pi mcp add|list|login`, a /mcp manager,
OAuth, per-tool exposure and resources. An extension that registers /mcp
REPLACES the built-in, so with mcp-loader installed pi never read mcp.json
and printed "registers command /mcp, so built-in extension mcp was not
loaded" on every start.

Measured on pi 1.1.0 (pi-devbox v1.11.0, tor-ms22) before removing it:
- time to the (auto) footer in a real pty, 7 interleaved runs each:
  -ne 0.276 s | -ne -e mcp-loader.ts 0.283 s | -ne -e builtin:mcp 0.272 s
- with no servers, the same prompt costs 79 input + 7680 cached tokens with
  the loader, the built-in, or neither
- a stdio server (server-everything) connected via `pi mcp list` in 3 s,
  and its echo tool ran end to end from `pi -p` with direct exposure
- no device in the fleet had an `mcp` block, so nothing needs migrating

install.sh now prunes links into this repo whose target is gone (.ts and
.ts.off), so the stale mcp-loader.ts link on a preserved pi-devbox volume is
removed on the first boot of an image without the file. It also warns once
if settings.json still carries an `mcp` block. Tested two-sided in a temp
HOME: the new script removes the repo link and a stale .ts.off, and keeps a
foreign dangling link and a real file. The old script leaves the dangling
link. Re-runs are idempotent, and there is no warning without an mcp block.

mempalace.ts (mempalace-toolkit) is unaffected: it registers mempalace_*
tools itself. Its vendored RemoteMcpClient loses its sync partner; that is
handled in mempalace-toolkit.
This commit is contained in:
Joakim Persson
2026-10-13 00:15:57 +02:00
parent a88fa99d39
commit 750b2a89c8
5 changed files with 100 additions and 988 deletions
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skill/SKILL.md
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@@ -23,11 +23,13 @@ Pi has **two distinct extension locations** and it's easy to look in the wrong o
| Location | Mechanism | Examples |
|---|---|---|
| `~/.pi/agent/extensions/*.ts` (or `.ts.off`) | **Local extensions** — TypeScript files, usually symlinks into `/opt/pi-extensions/extensions/` or similar. Toggled via `/ext` slash command. | `ssh-controlmaster`, `git-checkpoint`, `notify`, `todo`, `mempalace`, `mcp-loader`, `ext-toggle`, `confirm-destructive` |
| `~/.pi/agent/extensions/*.ts` (or `.ts.off`) | **Local extensions** — TypeScript files, usually symlinks into `/opt/pi-extensions/extensions/` or similar. Toggled via `/ext` slash command. | `ssh-controlmaster`, `git-checkpoint`, `notify`, `todo`, `mempalace`, `ext-toggle`, `task`, `fork-gate`, `secret-guard`, `aws-sso`, `confirm-destructive` |
| `~/.pi/agent/git/<host>/<owner>/<repo>/` | **Package extensions (git-installed)** — git-cloned npm packages registered via the `packages` array in `~/.pi/agent/settings.json`. | `pi-fork` (`github.com/elpapi42/pi-fork`), `pi-observational-memory` (`github.com/elpapi42/pi-observational-memory`, **default branch `master`** — a `main` branch does not exist, so `pi install git:...` resolves against `master`) |
| `~/.pi/agent/npm/node_modules/<pkg>/` | **Package extensions (npm-installed)** — `pi install npm:<pkg>`; recorded in `packages[]` as `npm:<pkg>`. | `pi-atelier` (status rail + sidebar TUI) |
| `/opt/<pkg>/` — **pi-devbox containers only** | **Vendored package extensions** — cloned into an image layer at build time with `node_modules` baked, then registered at container start by `entrypoint-user.sh` via `pi install /opt/<pkg>`. Recorded in `packages[]` as a **relative** path (`../../../../opt/pi-fork`) that resolves out of `~/.pi/agent` into the image layer, so it survives volume recreate. | `/opt/pi-fork`, `/opt/pi-observational-memory`, `/opt/pi-studio` |
**MCP servers are not an extension here.** pi's built-in MCP support (`builtin:mcp`) reads `~/.pi/agent/mcp.json`; manage it with `/mcp` or `pi mcp add|list`. Its tools are named `mcp__<server>__<tool>` and default to `codemode` exposure (not declared to the model) unless the server sets `"exposure": "direct"`. The `mempalace_*` tools are different: `mempalace.ts` registers them itself, so exposure never applies. The old `mcp-loader.ts` (an `mcp` block in `settings.json`) was retired on 2026-10-12, because an extension that registers `/mcp` replaces the built-in.
When the user asks how to use "the X extension", **check all of these** — `find ~/.pi/agent -maxdepth 4 -name "*X*"` covers the first three, and `ls -d /opt/*X*` the fourth. The `/ext` slash command shows the local-extensions list with enable/disable state. There is also a distinct skill-bundled-script category (e.g. `ci-release-watcher`'s `ssh-control-master-setup.sh`) which is **not** a pi extension at all — it's a helper script inside a skill. Don't conflate the three.
**In a pi-devbox container, do not conclude "pi-fork isn't installed" because `~/.pi/agent/git/` is empty.** It is deliberately absent: `Dockerfile.variant` vendors to `/opt` and installs by local path, because a build-time `pi install git:...` would write into `~/.pi/agent`, which the named volume then shadows on first run.