feat(pi): inject first-party local MCP tools

[jonathanlab]

Summary

• expose the shared posthog-code-tools MCP server to Pi cloud runs through Pi runtime capabilities
• move the local-tools MCP server out of the Codex adapter and reuse it from Pi
• remove the redundant Pi runtime factory and centralize capability-to-MCP resolution in createPiRpcClient
• package the MCP child with the Electron main build and resolve it from the Vite runtime

Testing

• pnpm --filter agent build
• pnpm --filter code typecheck
• targeted agent, harness, workspace-server, and desktop Pi tests

upload_artifact remains cloud-only; normal desktop Pi sessions retain local capabilities.

[trunk-io]

🚫 This pull request was removed from the merge queue because it was canceled by Jonathan Mieloo (a GitHub user). See more details here.

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 0573a01.}

[greptile-apps]

MCP child remains inside ASAR

When a packaged desktop Pi session enables a first-party local tool, the app launches .vite/build/mcp-server.js as a standalone Node script, but this new asset is not included in asarUnpack alongside rpc-host.js, causing the MCP child and its tools to fail at startup.

Knowledge Base Used: PostHog Code Desktop App (apps/code)

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/code/vite-main-plugins.mts
Line: 175-179

Comment:
**MCP child remains inside ASAR**

When a packaged desktop Pi session enables a first-party local tool, the app launches `.vite/build/mcp-server.js` as a standalone Node script, but this new asset is not included in `asarUnpack` alongside `rpc-host.js`, causing the MCP child and its tools to fail at startup.

**Knowledge Base Used:** [PostHog Code Desktop App (`apps/code`)](https://app.greptile.com/posthog-org-19734/-/custom-context/knowledge-base/posthog/code/-/docs/apps-code-desktop.md)

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

[greptile-apps]

Comments Outside Diff (1)

1. packages/harness/src/extensions/mcp/extension.ts, line 3497-3513 (link)

   Config errors drop runtime tools

   When the global or project mcp.json is malformed or unreadable, this handler returns before mergeRuntimeServers runs, causing the trusted posthog-code-tools server and its cloud Pi tools to be absent for the session.

   Knowledge Base Used:

   • Harness (hog/harness CLI)
   • Agent SDK (packages/agent)
   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: packages/harness/src/extensions/mcp/extension.ts
   Line: 3497-3513
   
   Comment:
   **Config errors drop runtime tools**
   
   When the global or project `mcp.json` is malformed or unreadable, this handler returns before `mergeRuntimeServers` runs, causing the trusted `posthog-code-tools` server and its cloud Pi tools to be absent for the session.
   
   **Knowledge Base Used:**
   - [Harness (`hog`/`harness` CLI)](https://app.greptile.com/posthog-org-19734/-/custom-context/knowledge-base/posthog/code/-/docs/harness-cli.md)
   - [Agent SDK (`packages/agent`)](https://app.greptile.com/posthog-org-19734/-/custom-context/knowledge-base/posthog/code/-/docs/agent-sdk.md)
   
   ---
   
   For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Prompt To Fix All With AI

### Issue 1
apps/code/vite-main-plugins.mts:175-179
**MCP child remains inside ASAR**

When a packaged desktop Pi session enables a first-party local tool, the app launches `.vite/build/mcp-server.js` as a standalone Node script, but this new asset is not included in `asarUnpack` alongside `rpc-host.js`, causing the MCP child and its tools to fail at startup.

### Issue 2
packages/harness/src/extensions/mcp/extension.ts:3497-3513
**Config errors drop runtime tools**

When the global or project `mcp.json` is malformed or unreadable, this handler returns before `mergeRuntimeServers` runs, causing the trusted `posthog-code-tools` server and its cloud Pi tools to be absent for the session.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(pi): inject local MCP tools" | Re-trigger Greptile}

[jonathanlab]

/merge stop

[jonathanlab]

/trunk stop

[veria-ai]

PR overview

All previously flagged issues have been addressed. No open security concerns remain on this pull request.

Security review

No open security issues remain on this pull request.

Fixed/addressed: 1 · PR risk: 0/10

[charlesvien]

Hey @jonathanlab, we've migrated this repo into the PostHog/posthog monorepo, so this PR needs to be recreated there.

Easiest path: check out the monorepo and run the /porting-code-prs skill with your agent pointed at this PR. It has the migration guide and path remappings baked in so the agent doesn't have to figure them out. You don't strictly need it though, just asking your agent to port the PR works fine too.

Shout if you get stuck.