Overview

I'd like to take this on as an open source contribution. I'm a researcher at Lawrence Livermore National Laboratory working in ML, and in my free time I contribute to open source — this is a workflow problem I hit regularly and want to fix properly.

Ready to deliver within 15 days of approval via staged focused PRs per contribution guidelines.

The Problem

The Cline VS Code extension supports only one active agent session at a time in the sidebar. To work on two independent features in parallel today, a developer must:

• Open two separate VS Code windows manually, OR
• Wait for one task to finish before starting another

This is a real productivity bottleneck. Two independent tasks — say, implementing Feature A and Feature B — have no reason to share context, memory, or file state. Forcing them into the same session or window is an artificial constraint.

Prior Art & Why This Is the Right Moment

Inside Cline's own ecosystem:

• Discussion Independent Cline sessions for multi-root workspaces / multiple folders #8978 — The community has been asking for independent sessions and this feels like a natural next step to build on top of the great work already done in CLI 2.0 and Kanban.
• Issue Multiple Cline instances are synchronized to the same task #3514 — Pre-v3.15 behaviour allowed independent tabs, which users found valuable.
• Discussion Multi-Agent Software Development with Cline #1007 — Multi-agent orchestration demand has been consistently high since early in Cline's history.

Outside Cline:

• Cursor 2.0 (Oct 2025) ships native parallel agents in the sidebar, backed by git worktrees, with up to 8 simultaneous isolated sessions.
• Cline CLI 2.0 (Feb 2026) already solves this in the terminal — fully isolated instances, each with own state, conversation, and model config.
• Cline Kanban already creates ephemeral git worktrees per task card for parallel agent isolation.

The infrastructure already exists inside Cline. This proposal is simply the VS Code UI layer that connects it — building on top of what the team has already laid the groundwork for.

Proposed Solution: Tab Bar in the Sidebar

A single tab bar row added between the existing topbar and the content area. Nothing else in the shell changes.

Each tab is:

• An isolated ClineProvider instance with its own state, context, history, and model config
• Backed by its own ephemeral git worktree (reusing logic already in Cline CLI / Kanban)
• Running its own Plan, Act, or Chat mode independently
• Named per branch (e.g. feat/auth, feat/dashboard, bugfix/login)
• Persisted in VS Code workspace state across reloads

Tab dot color system:

Chat mode (green) is specifically for when you want to think out loud with the agent — explore a problem, sketch an approach, finalize a rough idea — before ever entering Plan or Act mode. No file changes, no worktree operations. Pure ideation.

No shared context. No file conflicts. Review and merge per branch.

Concrete Use Case

Working on a project with two independent features that should not share context:

1. Open Tab 1 → describe Feature A → agent plans and executes on branch feat/auth in its own worktree
2. Open Tab 2 → describe Feature B → separate agent plans and executes on branch feat/dashboard in its own worktree
3. Both run in parallel. No interference, no context bleed.
4. Flashing dot on either tab signals completion without needing to switch tabs constantly.
5. Review diffs independently per tab, merge whichever passes.

This is identical to how Cursor 2.0's parallel agent sidebar works, but built natively into Cline's open-source extension.

Implementation Plan (15-day delivery)

3 focused PRs, each independently reviewable:

PR 1 — TabBar UI component (Days 1–4)

• Files: webview-ui/src/components/TabBar.tsx (new)
• Tab bar React component above chat panel
• Tab state managed locally in React (active tab index, tab list)
• Dot color states: blue, yellow, green, grey, flashing
• Purely visual — no backend wiring yet
• Tests: component render tests

PR 2 — Multi-instance ClineProvider (Days 5–10)

• Files: src/core/ClineProvider.ts, src/extension.ts
• Multiple provider instances keyed by tab ID
• Each instance maintains isolated state, history, model config
• Tab switching triggers provider context swap
• Chat mode = no worktree, no file ops, conversation only
• Tests: unit tests for provider isolation

PR 3 — Git worktree binding per tab (Days 11–15)

• Reuse worktree creation logic from Cline CLI / Kanban
• Each Plan/Act tab creates an ephemeral worktree on a named branch
• Worktree cleanup on tab close
• Tab state (including worktree path) persisted in VS Code workspace state
• Tests: integration tests for worktree lifecycle

What I'm NOT changing

• The existing topbar layout and icons
• The existing home/recent screen (shown when a tab has no active task)
• The existing Plan/Act mode toggle within each session
• Any CLI or Kanban behaviour

References

• Discussion Independent Cline sessions for multi-root workspaces / multiple folders #8978 — Independent sessions community request
• Issue Multiple Cline instances are synchronized to the same task #3514 — Tab sync regression post-v3.15
• Discussion Multi-Agent Software Development with Cline #1007 — Multi-agent demand
• Cursor 2.0 parallel agents: https://cursor.com/blog/2-0
• Cline CLI 2.0 parallel execution: https://cline.bot/blog/introducing-cline-cli-2-0
• Cline Kanban worktrees: https://github.com/cline/kanban

Happy to discuss architecture details, adjust scope, or break into smaller pieces if preferred. Ready to start immediately on approval.