feat(sidebar-v2): add task tabs and context forks

[t3dotgg]

What changed

• Reframes Sidebar v2 thread rows as workspace tasks, grouping sibling provider threads under a durable workspaceTaskId.
• Adds an in-task tab strip with Cmd/Ctrl+T fresh-tab creation, a web-visible add button, provider/model selection per tab, context-fork creation, status indicators, and safe tab close behavior.
• Keeps every tab in a task on the same project/worktree while allowing a different provider harness.
• Adds a bounded, provider-neutral context handoff for the child tab's first turn without copying that handoff into the visible child transcript.
• Makes settle, snooze, unread, rename, and delete behavior task-aware in Sidebar v2.
• Adds migration 035, projection persistence, server capability negotiation, and one-task/one-tab backfill behavior for legacy threads.
• Includes the original HTML implementation plan at .plans/task-tabs-context-fork.html.

Why

The current sidebar treats each agent conversation as an independent unit even when several agents are working toward one outcome. This experiment makes the worktree-backed task the durable unit while preserving threads as independently configurable execution tabs.

Older servers and legacy rows retain the existing one-thread behavior. The client only exposes task-tab creation when the server advertises support.

Validation

• vp run -F @t3tools/contracts -F @t3tools/shared -F t3 -F @t3tools/web --parallel typecheck
• Targeted lint and formatting across all changed TypeScript files
• 251 focused tests across contracts, migrations, projections, command invariants, provider handoff, composer persistence, keybindings, and workspace-task grouping
• Isolated authenticated browser pass:
  • enabled Sidebar v2
  • created and closed a fresh draft tab
  • materialized a main task with a real provider turn
  • forked that context into a second live provider tab
  • verified the shared-tree running state and sidebar tab count
  • received the forked response
  • closed the persisted child tab and returned to Main
  • confirmed both projection rows shared a task/branch and the child retained portable-fork provenance plus a durable close timestamp

Note

Add workspace task tabs and context forks to sidebar and chat view

• Introduces a WorkspaceTaskId concept that groups related threads (tabs) into a single task; the sidebar now groups, displays, and operates on threads at the task level (snooze, settle, delete, etc. apply to all tabs)
• Adds a WorkspaceTaskTabs tab bar in the chat view for navigating between tabs, creating fresh tabs, and forking context into a new tab (portable fork)
• Portable context forks synthesize a size-bounded transcript from the source thread and prepend it to the first provider turn in the new tab via buildPortableForkProviderInput
• Adds database migration 035 to add workspace_task_id, tab_position, tab_closed_at, and fork_provenance_json columns to projection_threads, with backfill for legacy rows
• Extends orchestration contracts, decider invariants, projector, and projection queries to carry and enforce tab/task metadata and fork provenance throughout the event pipeline
• Risk: listActiveThreadRows now excludes threads with tab_closed_at IS NOT NULL; any caller expecting closed tabs in active listings will silently receive fewer results

📊 Macroscope summarized 0ed495a. 25 files reviewed, 0 issues evaluated, 0 issues filtered, 0 comments posted

🗂️ Filtered Issues

No issues evaluated.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 9e0d5cf0-9466-4448-8522-b8b36ffc05d6

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch t3code/task-tabs-context-fork

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}