feat(ui): add copy button to assistant text responses

[IamCoder18]

Context

Assistant text responses in the chat UI have no copy button. User messages, code blocks inside markdown, and bash tool output all have copy buttons — but assistant text parts don't. This adds one.

Closes #7870

Implementation

The rendering chain ChatView → MessageList → VscodeSessionTurn → AssistantMessage → Part → TextPartDisplay is shared across the sidebar, Agent Manager, and subagent viewer, so a single change in the shared TextPartDisplay component covers all three surfaces.

Most of the infrastructure was already in place:

• The CSS had a [data-slot="text-part-copy-wrapper"] selector with display: none — pre-wired but never connected
• i18n keys ui.message.copyResponse and ui.message.copied already translated in 16+ languages
• All imports (Tooltip, IconButton, createSignal, useI18n) already in the file
• showAssistantCopyPartID prop already plumbed through the component chain
• The same copy-button pattern used 4 other times in the same file

CSS (message-part.css): Changed the wrapper from display: none to display: flex with opacity: 0; pointer-events: none and a 0.15s opacity transition. Hover over the parent [data-component="text-part"] reveals the button. When data-is-turn-copy is set (active/last text part), the button is always visible.

TSX (message-part.tsx): Added to TextPartDisplay — useI18n() call, copied signal, isLastTextPart memo (finds last text part in message), showCopy memo (uses showAssistantCopyPartID prop or falls back to isLastTextPart), handleCopy handler with 2s check icon toggle, and a <Tooltip> + <IconButton> block inside a <div data-slot="text-part-copy-wrapper">.

Zero new imports, zero new i18n keys, zero new CSS selectors, zero new props.

Screenshots

Before (no copy button):

After:

after.mp4

How to Test

1. Open the Kilo sidebar chat
2. Send a message that generates an assistant response with multiple text parts
3. Hover over any assistant text part — a copy button should appear in the bottom-right
4. Click the copy button — it should briefly show a check icon and copy the text to clipboard
5. The last/active text part's copy button should be always visible (not just on hover)
6. Test in the Agent Manager panel — the same copy button should appear there too

Get in Touch

My discord is @iamcoder18 and I am in the Kilo Code discord server.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 files)

• packages/kilo-ui/src/components/message-part.css

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_{Reviewed by gpt-5.4-20260305 · 186,545 tokens}