agent_ui: Show controls after every agent message

[peakxy]

Objective

Fixes #61244

In the Agent Panel, after a multi-turn conversation, the action buttons ("Copy this Agent response", "Scroll to User Message", and "Scroll to top") were only shown after the last assistant response. This was inconvenient for users who wanted to copy or navigate from earlier responses.

Additionally, the "Scroll to User Message" button always jumped to the most recent user message in the entire thread, even when clicked from a historical assistant response.

This PR addresses both issues by rendering the controls after every non-blank assistant response, and by making "Scroll to User Message" jump to the user prompt associated with that specific response.

Solution

• Refactored render_thread_controls in crates/agent_ui/src/conversation_view/thread_view.rs to accept an explicit entry_ix, copy_response_index, is_thread_bottom, and user_message_index, making it reusable per assistant message.
• Rendered the control bar after each non-blank AssistantMessage entry, not just the last entry.
• Made button IDs unique by using tuple IDs like ("name", entry_ix), matching the existing style in this file and avoiding format! allocations.
• Keyed the copy button ID by the control bar location (entry_ix) while still copying response_index's content, so the bottom fallback bar doesn't duplicate IDs with the per-response bar.
• Gated the generation/confirmation early return to is_thread_bottom, so historical controls remain accessible while the thread is generating or waiting for confirmation.
• Gated turn stats and thread feedback buttons to the bottom of the thread so they only appear on the last response.
• Replaced scroll_to_most_recent_user_prompt with a more general scroll_to_user_message_index that takes an optional target user message index.
• For each per-response button, computed the associated user message index as the most recent user message before that assistant response.
• For the bottom fallback (when the last entry is not an assistant message), passed None so the button still scrolls to the most recent user message.
• Updated the tooltip from "Scroll to Most Recent User Message" to "Scroll to User Message".
• Updated existing tests and added assertions for scroll_to_user_message_index(Some(ix), cx).

Testing

• cargo check -p agent_ui
• ./script/clippy -p agent_ui
• cargo test -p agent_ui --lib (399 passed)
• Added assertions in test_scroll_to_most_recent_user_prompt to verify scroll_to_user_message_index(Some(0), cx) and scroll_to_user_message_index(Some(2), cx) scroll to the correct user message indices.
• Manual testing recommended: open the Agent Panel, send multiple messages, and verify that each assistant response has the three buttons and that "Scroll to User Message" jumps to the corresponding user prompt.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments (no unsafe blocks)
• The content adheres to Zed's UI standards (UX/UI and icon guidelines)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Showcase

Before: Only the last assistant response in the Agent Panel showed the "Copy this Agent response", "Scroll to User Message", and "Scroll to top" buttons. Clicking "Scroll to User Message" always jumped to the most recent user message.

After: Every non-blank assistant response displays these buttons. Clicking "Scroll to User Message" on a historical response scrolls to the user prompt that triggered that specific response.

CleanShot.2026-07-18.at.15.44.08.mp4

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Release Notes:

• Added "Copy this Agent response", "Scroll to User Message", and "Scroll to top" buttons to every agent response in the Agent Panel.
• Fixed "Scroll to User Message" so it jumps to the user prompt associated with the current response, rather than the most recent user message.

[Copilot]

Pull request overview

This PR updates the Agent Panel conversation thread UI so the per-turn action controls (copy response, scroll to the corresponding user prompt, scroll to top) are rendered after every non-blank assistant message, and makes “Scroll to User Message” target the user message associated with that specific assistant response (instead of always jumping to the most recent user message).

Changes:

• Render the thread control bar under each non-blank AssistantMessage, and gate turn stats + thread feedback controls to the bottom of the thread.
• Replace scroll_to_most_recent_user_prompt with scroll_to_user_message_index(user_message_index: Option<usize>) and wire the per-response “Scroll to User Message” button to the appropriate index.
• Update tests to use the new scroll API (and adjust control button IDs to avoid duplicate IDs).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
crates/agent_ui/src/conversation_view/thread_view.rs	Refactors and reuses render_thread_controls per assistant response; adds user-message targeting for scroll; adjusts control rendering/gating.
crates/agent_ui/src/conversation_view.rs	Updates existing tests to call the new scroll_to_user_message_index API.

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[peakxy]

@ChristopherBiscardi Hi, you’ve merged my PR before, so I’d like to trouble you to take a look at this one as well at your convenience😊

[ChristopherBiscardi]

thanks