feat(tui): add focus view to collapse multi-step turns

[liush2yuxjtu]

Issue for this PR

Closes #37003

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds an opt-in TUI "focus view" toggle that collapses each multi-step assistant turn into one compact block: the turn's final text, a one-line summary of every tool call across the turn, and a hidden-message count. New messages update the block in place instead of appending more messages.

Why it works: a single prompt often produces several assistant messages (a tool-calls round, then a final text round), so the transcript floods with full tool output. Focus view groups messages by parentID into turns and only renders the last message of each turn as a collapsed block while enabled.

Toggle via command palette ("Enter/Exit focus view"), a /focus slash command, or a focus_view keybind (default none, configurable in tui.json). State persists across sessions. Disabled by default so existing behavior is unchanged.

This is an implementation of the collapse behavior requested in #37003, delivered as opt-in rather than default-on.

Design

A turn is the set of assistant messages sharing the same parentID (the user message). A multi-step reply emits a tool-calls round (finish="tool-calls") followed by a final text round (finish="stop").

Demo 1 · Turn structure — click a message card to highlight its timeline row (interactive):

https://github.com/liush2yuxjtu/opencode/releases/download/focus-demo-v1/fig1-highlight.webm

Demo 2 · Focus OFF vs ON — click either side to toggle full/collapsed view (interactive):

https://github.com/liush2yuxjtu/opencode/releases/download/focus-demo-v1/fig2-toggle.webm

Demo 3 · Message flow — the display block updates in place as new messages arrive (interactive):

https://github.com/liush2yuxjtu/opencode/releases/download/focus-demo-v1/fig3-flow.webm

Render rule

function renderTurn(turn, focusView) {
  if (!focusView) return turn.messages.map(renderMessage)
  const last = turn.messages.at(-1)            // final assistant message of the turn
  const tools = turn.messages.flatMap(toolsOf) // all tool calls across the turn
  if (!last.time.completed) return <StreamingTurn summary={toolsSummary(tools)} />
  return <CollapsedTurn text={last.textParts} summary={toolsSummary(tools)} hidden={tools.length} />
}

How did you verify your code works?

• bun run typecheck (packages/tui) passes.
• Ran a local bun dev session and verified:
  • Focus ON: a hello-world turn collapsed to ↳ 1 write, 1 bash · 3 messages hidden + final text, with a single turn footer (no duplicate ▣ lines from hidden intermediate messages).
  • Focus OFF: full tool output (Write diff, shell output) restored.

Screenshots / recordings

Focus ON (collapsed):

↳ 1 write, 1 bash · 3 messages hidden (toggle /focus to show)
Wrote /tmp/hello.ts and ran it with bun — output: Hello, world!

Focus OFF (full):

# Wrote /tmp/hello.ts
  1 console.log("Hello, world!")
$ bun /tmp/hello.ts
Hello, world!
Wrote /tmp/hello.ts and ran it with bun — output: Hello, world!

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[liushiyu052333-gif]

fig2-toggle.webm

fig3-flow.webm

fig1-highlight.webm