agent: Add ask_user tool using elicitation forms

[e-r-w]

Summary

Adds a first-party ask_user tool to Zed's native agent (crates/agent) that lets the agent ask the user a question and get an answer back through a proper elicitation form rather than free-form chat text.

This is a step towards the interactive-question experience requested in discussion #48784 (implement the ACP elicitation spec for agent questions). Zed already renders elicitation forms client-side; this wires the native agent up to that existing rail so the agent can drive single-select and/or free-text prompts.

What it does

The tool takes:

• question — the prompt shown to the user
• options — optional list of selectable choices (single-select)
• allow_free_text — whether the user may type a custom answer instead of picking an option

The agent decides the shape of each question:

options	allow_free_text	Result
2+	false	Single-select only
2+	true	Single-select with a free-text "other" field
empty	true	Free-text only

A typed answer takes precedence over a selected option, and the tool always resolves (a cancelled or failed elicitation is reported back to the agent rather than hanging).

Demo

Screen.Recording.2026-07-24.at.9.57.02.am.mov

Implementation

• thread.rs — new ThreadEvent::Elicitation(ElicitationRequest) variant plus ToolCallEventStream::request_elicitation, mirroring the existing prompt_for_decision permission rail.
• agent.rs — handles the elicitation event by building a session-scoped acp::CreateElicitationRequest and routing it through AcpThread::request_elicitation, piping the response back to the tool.
• tools/ask_user_tool.rs — the tool itself, including schema construction and response extraction.
• Registered in the write and ask profiles and excluded from the tool-permissions setup UI.

No client-side UI changes were needed — the existing elicitation form rendering handles it.

Tests

cargo test -p agent ask_user — 5 unit tests covering schema construction, validation, and accept/decline/cancel handling.

Release Notes:

• Added an ask_user tool that lets the agent ask the user a question with selectable options and/or free-text input, rendered as an elicitation form

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[e-r-w]

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[e-r-w]

@ChristopherBiscardi any thoughts on this? I love the zed agent and this would bring it up to speed with the other ACP agents

[ChristopherBiscardi]

Thank you! This works wonderfully.

[pedropaulocs]

Until finally huehuehue Tks!