`agent acp` never offers the AskQuestion tool, so `cursor/ask_question` is never sent

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1

Where does the bug appear (feature/product)?

Cursor CLI

Describe the Bug

Under agent acp, the model’s tool list never includes AskQuestion, in either agent or plan mode. Headless agent -p with the same model does include it. So ACP clients never receive the documented cursor/ask_question extension request, and agents fall back to printing questions as plain text.

This affects ACP clients that already implement cursor/ask_question, e.g. T3 Code: [Bug]: Cursor ACP sessions never offer the AskQuestion tool, so the question UI is never used · Issue #13632 · pingdotgg/t3code · GitHub

Steps to Reproduce

  1. Start agent acp and run initialize → authenticate (cursor_login) → session/new.
  2. Send session/prompt: “Do not call any tools. List the exact names of every tool/function available to you, comma-separated, nothing else.”
  3. Repeat after session/set_mode with modeId: "plan".
  4. Compare with agent -p --trust "<same prompt>".

Results (same model, same machine):

Launch Tools reported
agent acp, mode agent Shell, Glob, Grep, AwaitShell, Read, Delete, StrReplace, Write, EditNotebook, TodoWrite, WebSearch, WebFetch, Task, GetDynamicTools, FetchMcpResource, SwitchMode, CallDynamicTool
agent acp, mode plan same + CreatePlan. No AskQuestion
agent -p --trust same + AskQuestion

initialize capabilities sent: { fs: { readTextFile: false, writeTextFile: false }, terminal: false, _meta: { parameterizedModelPicker: true } }. I couldn’t find any client capability that enables it. The CLI only reads _meta.subagents and _meta.parameterizedModelPicker, and ACP requests are tagged x-cursor-client-type: acp.

Expected Behavior

ACP sessions get AskQuestion like the other surfaces, and calling it sends cursor/ask_question to the client, as described in ACP | Cursor Docs. If it should only be enabled for clients that handle the method, please document the capability flag that turns it on.

Operating System

MacOS

Version Information

CLI Version 2026.09.23-86fc751 (also reproduced on 2026.09.18-9a7762b)

For AI issues: which model did you use?

Claude Opus 5.5 (claude-opus-5-5) but happens with any model

Additional Information

Skills that say “use the harness question tool” work with the Claude Code and Codex providers in the same client, but fall back to plain-text questions with Cursor through ACP.

Does this stop you from using Cursor

No - Cursor works, but with this issue

7

Hey @javiervd, thanks for the report and the side-by-side comparison!

We were able to trace this on our side. It comes from how ACP sessions are identified on our end, not from anything missing in your client’s initialize capabilities.

I’ve flagged it to the team.