[Feature]: Support multi-directory context linking / flexible multi-folder workspaces (Claude Code parity)

[alexwork1611]

Problem / Motivation

In modern development workflows, projects frequently span beyond a single Git repository root. Common setups include:

• Multi-repository microservices (e.g., separate \rontend, \�ackend, and \shared-contracts\ repositories).
• External documentation, design systems, or API specs maintained in separate folders.
• Monorepos with sibling packages, or external local utilities referenced without merging everything into a single repo.

Currently, T3 Code binds each conversation/thread tightly to a single project's Git root. When an agent needs to reference or cross-check code across multiple folders/projects, the user must either switch between isolated threads or manually copy files into the active worktree, breaking continuity.

Proposed Solution: Flexible Multi-Directory / Project Context System

Similar to Claude Code's /add-dir\ and --add-dir\ capabilities, introduce a flexible mechanism to attach and manage one or more secondary directories/projects within an active conversation:

1. Multiple Folder / Repository Attachment:

   • Support adding an arbitrary number of supplementary directories to an active conversation thread.
   • Accessible via both GUI controls (e.g., an "Attached Folders / Context" section in the thread sidebar/inspector) and conversational slash commands (e.g., /add-dir \ or /link ).

2. Granular Access Control & Modes:

   • Read-only vs. Read-write: Allow setting mounted directories to reference-only (for documentation, shared types, or sibling services) or editable.
   • Git Integration: When a linked directory is a Git repository, allow the agent to inspect git status/diffs while respecting its separate git boundary.

3. Tool & Context Awareness:

   • Ensure file search, grep/ripgrep, file reading, and MCP servers can discover and resolve paths across all attached roots in that session.
   • Prefix or scope paths clearly in agent tool calls to avoid collisions between identically named files across distinct directories.

4. Persistence & Presets:

   • Save attached directories per thread or allow users to define workspace presets grouping related project folders together.

Alternatives Considered

• Moving all repositories into an overarching monorepo (often infeasible for teams or existing infrastructure).
• Using OS symlinks into the active worktree (fragile across OS platforms, especially Windows/macOS, and pollutes git status).

[juliusmarminge]

Duplicate of #7041 — same multi-root / multi-folder / multi-repo workspace request (agent context across multiple directories in one thread; Claude Code /add-dir / Codex-style attached folders).

Please continue there. Related prior consolidations: #11051, #12220.

[alexwork1611]

Thanks, Julius. I searched for similar issues, but I guess my AI's GitHub issue search scope was not large enough.