[BUG] Claude agent crashes in Copilot Chat with "Error during execution" (VS Code 1.128.0 built-in Copilot, Node 24)

Description

Using @claude in VS Code's built-in Copilot Chat crashes with Error during execution. The crash occurs immediately after [ClaudeCodeSession] Passing 64 plugin(s) from skill locations, suggesting the failure is in the agent handshake/plugin registration phase.

Basic Copilot Chat requests (e.g. gpt-4o-mini) succeed — only the Claude agent integration fails.

Steps to Reproduce

1. Open VS Code 1.128.0 (which includes Copilot as a built-in extension)
2. Have Claude Code extension installed (v2.1.207)
3. Open Copilot Chat
4. Invoke @claude with any prompt

Expected Behavior

Claude agent responds in Copilot Chat.

Actual Behavior

Crash with Error during execution. A MODULE_TYPELESS_PACKAGE_JSON warning about ESM reparsing appears on stderr immediately before the error, which may be related — Node 24 tightened module type resolution.

Logs

From GitHub Copilot Chat output channel:

2026-07-13 11:43:34.133 [info] [ClaudeCodeSession] Passing 64 plugin(s) from skill locations
2026-07-13 11:43:34.601 [error] claude-agent-sdk stderr: (node:23795) [MODULE_TYPELESS_PACKAGE_JSON] Warning: Module type of file:///Applications/Visual%20Studio%20Code.app/Contents/Resources/app/extensions/copilot/dist/cli.js is not specified and it doesn't parse as CommonJS.
Reparsing as ES module because module syntax was detected. This incurs a performance overhead.
To eliminate this warning, add "type": "module" to /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/copilot/package.json.
(Use `Code Helper (Plugin) --trace-warnings ...` to show where the warning was created)
2026-07-13 11:43:36.231 [error] Error: Error during execution
	at cUo (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/copilot/dist/extension.js:2908:480)
	at iyr (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/copilot/dist/extension.js:2908:692)
	at n.invokeFunction (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/copilot/dist/extension.js:29:944)
	at uV._processMessages (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/copilot/dist/extension.js:2915:17124)
	at process.processTicksAndRejections (node:internal/process/task_queues:104:5)

Environment

• VS Code: 1.128.0 (Universal)
• Electron: 42.5.0
• Node.js: 24.17.0
• OS: macOS Darwin arm64 25.5.0
• Claude Code extension: 2.1.207
• Copilot: Built-in (no separate extension installed)

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This issue was drafted with the help of Claude Code (AI coding assistant).