[BUG] IDE diagnostics (mcp__ide__getDiagnostics) unavailable in the VS Code embedded-panel runtime

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When Claude Code runs as the native VS Code extension (the embedded panel, not the standalone CLI attached to VS Code via /ide), the assistant has no access to VS Code's live language-server diagnostics. The ide MCP server — the bridge that normally exposes mcp__ide__getDiagnostics — is never registered in this runtime (verified: ListMcpResources shows only unrelated user-configured servers, no ide entry). The /ide command also doesn't exist in this build, because there's no separate IDE instance to attach to — the extension is the host.

The only code-intelligence tool available to the model is the LSP tool, which exposes navigation operations only (goToDefinition, findReferences, hover, documentSymbol, workspaceSymbol, call hierarchy) — there is no diagnostics operation — and it reads disk-snapshot state rather than the editor's live buffer.

Net effect: the assistant is running inside VS Code, with a warm, permanently-running language server in the same process tree, and cannot read it. To check whether code compiles or has errors, it has to fall back to running a full build, and its view of a file is stale relative to unsaved editor changes. The diagnostics path appears to have been built for the attach-from-terminal topology; the embedded-panel topology has no equivalent bridge.

This (or something similar) was reported in #21374, but there was never any activity. The problem still exists.

What Should Happen?

In the embedded VS Code extension runtime, the model should have access to the live language-server diagnostics for the workspace — equivalent to what mcp__ide__getDiagnostics provides when the standalone CLI attaches to VS Code. Specifically:

An in-process bridge that surfaces VS Code's current diagnostics (errors/warnings, including from unsaved buffers) as a callable tool, without requiring a separate attach step.
Diagnostics that reflect the editor's live in-memory document state, so the model's view matches what the user sees in the Problems panel rather than lagging behind on disk.

Error Messages/Logs

Steps to Reproduce

1. Install and enable the Claude Code VS Code extension.
2. Open a workspace and interact with Claude through the embedded extension panel (not via a terminal where you ran claude + /ide).
3. Open a file with a known type error / diagnostic visible in VS Code's Problems panel.
4. Ask Claude to report the diagnostics, or have it inspect available MCP servers/tools.
5. Observe: no ide MCP server is registered and no mcp__ide__getDiagnostics tool is available; /ide is not a recognized command; the LSP tool offers navigation only, with no way to read the diagnostics the IDE already has.

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.145

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_