AgentMux — Claude, Codex, OpenCode, Hermes & Antigravity in tmux

Five agents. One terminal flow.

Run Claude Code, OpenAI Codex CLI, OpenCode, Hermes (Nous Research) and Google Antigravity (agy) in persistent tmux sessions, switch between them instantly, and hand work from one agent to another from a single VS Code side-bar view.

The extension is deliberately workspace-scoped:

• the Claude tab controls only tmux_claude_<folder>;
• the Codex tab controls only tmux_codex_<folder>;
• the OpenCode tab controls only tmux_opencode_<folder>;
• the Hermes tab controls only tmux_hermes_<folder>;
• the Antigravity tab controls only tmux_agy_<folder>;
• every existing session is accepted only when its tmux session_path matches the current VS Code workspace root;
• projects with the same folder name receive a stable path hash when needed, so one project can never attach to another project's tmux session.

Every agent survives VS Code restarts, Remote-SSH drops and local disconnects.

What the view does

It mirrors the selected tmux pane instead of opening another VS Code terminal:

• a persistent tmux control-mode client drives everything by default: no fork/exec per refresh, and tmux pushes an output notification the moment the active pane changes (a pipe-pane tap and classic polling are automatic fallbacks — claudeTmux.transport);
• each refresh fuses the frame and its cursor/size metadata into one atomic call, and small changes travel to the view as per-line deltas;
• the refresh loop is adaptive: hot while you type or output streams, slow when the pane is static, watchdog-only when push notifications are live;
• one ordered input pump merges pending keystrokes under backpressure, while bracketed paste preserves large UTF-8 input;
• a tab appears only while that workspace's matching tmux session exists, and only for agents whose CLI is installed; tabs carry live state dots;
• the + menu starts or resumes an absent agent (past conversations are listed per workspace for Claude, Codex, OpenCode and Hermes);
• Cmd/Ctrl+click a path/file.js:42 in agent output to open it in the editor;
• Alt+Up recalls previously submitted prompts (reconstructed locally from your keystrokes, never from agent output);
• mouse wheel, scrollbar and Shift+PageUp / Shift+PageDown navigate history; large history captures render virtualized, so scrolling up never hitches;
• new output follows automatically only while you are at the bottom;
• switching tabs paints an at-most-seconds-old frame instantly (background captures keep the inactive tab's cache warm).

Requirements

Install these on the machine where the extension runs. Under Remote-SSH that is normally the remote host.

tmux -V
claude --version
codex --version
opencode --version
hermes --version

• tmux 2.9 or newer;
• at least one agent CLI on PATH — Claude Code, OpenAI Codex, OpenCode, Hermes (Nous Research) or Google Antigravity (agy) — for its tab.

You may use any tab when only one agent CLI is installed.

Build and install

From this repository:

npm run check
npm run package
code --install-extension claude-tmux-sidebar-0.12.0.vsix --force

Alternatively use VS Code: Extensions → … → Install from VSIX…, select the generated file, then run Developer: Reload Window.

For Remote-SSH, install the VSIX in the remote extension host from the connected window. tmux, claude and codex must be available on that same remote host.

The AgentMux icon appears in the Activity Bar. You can drag its view to the Secondary Side Bar; VS Code remembers the layout.

Daily workflow

1. Open a project folder in VS Code.
2. Open AgentMux. If no agent is running, choose one from the central launcher. Use + later to add the others.
3. Start or resume:
   • each agent lists its own past conversations for this folder, when its CLI exposes them (Claude, Codex, OpenCode, Hermes);
4. Click the mirror and type. Switch visible tabs whenever you want; both tmux sessions continue running independently.
5. Scroll with the wheel or scrollbar. Use Shift+PageUp/PageDown from the keyboard. Plain PageUp/PageDown are still forwarded to the agent TUI.

The toolbar actions always target the selected tab:

Pair Mode

Pair Mode coordinates the agents sequentially and refuses a handoff while either side is detected as working:

1. Select the agent that currently owns the work and press ⇄.
2. Add optional details for the other agent. Nothing is sent until you press Create handoff.
3. If the other agent has no workspace tmux, the extension offers to start it.
4. AgentMux asks the source agent to author a standalone briefing specifically for the target: objective, completed work, files, decisions, tests, risks and the recommended next action.
5. Fresh Git facts are added separately. Choose Continue task, Review only or Review & Fix, then freely edit the complete message.
6. Only Send handoff delivers the reviewed message. By default the briefing is written to .claude/agentmux/handoff-<id>.md and only a short pointer is pasted into the target TUI; the target acknowledges by writing .claude/agentmux/ack-<id> (or printing the marker line if it cannot write files). On success it becomes the Pair Mode writer. If the best-effort acknowledgement is not observed, AgentMux offers manual acceptance or dismissal without ever resending. A delivered handoff even survives a VS Code restart (rehydrated from the workspace ledger as manual-accept only).
7. After a Review only / Review & Fix handoff completes, ↩ asks the reviewer to author a structured findings report and hands it back to the original author under the same acknowledgement rules.
8. Hand back with ⇄, release the lock with ◇, or audit everything in the ◷ Timeline.

Arbiter mode

⚖ (or AgentMux: Ask both agents) sends one question to two running agents in parallel — answers only, no file changes. Both replies are gathered through the .claude/agentmux channel and shown side by side; the answer you pick makes that agent the Pair Mode writer and tells it to proceed.

The briefing capsule now includes recent commits, capped real diff hunks, your task file (claudeTmux.handoffTodoFile), optional verify-command output (claudeTmux.handoffVerifyCommand, trust-gated) and best-effort conversation resume pointers, in addition to the Git status/stat facts.

The compact footer shows pane size, session uptime and agent state — plus, when available, token usage and turn count tailed from the CLI's own local transcript, the current tool while working, and the last turn's git delta (Δ3 +120−14). It also shows available history, attached tmux clients and capture lag when that lag is high enough to matter. All of it reuses existing snapshots and local file reads; nothing new runs on the live refresh path and nothing leaves your machine.

Agent state is no longer only a heuristic: managed launches install Claude Code lifecycle hooks, a Codex notify program and an OpenCode state plugin that stamp working / needs-input / done (and the current tool) into tmux pane options, which the extension already reads for free. A single consolidated status bar item mirrors the active agent everywhere in VS Code (every present agent in its tooltip, click to cycle focus), the view badge counts agents that finished or are waiting, and when a hidden agent asks a numbered question a notification offers its options as one-click answer buttons (explicit, identity-pinned, never automatic). Anyone attached to the tmux session from a real terminal sees the same facts on the tmux status line.

The lock coordinates input sent through this side bar; it cannot stop a turn that was launched outside the extension or prevent a user/process attached to the same tmux session elsewhere from editing files. Review only is an instruction to the agent, not an operating-system sandbox.

Shared .claude rules

With claudeTmux.codexReadClaudeRules enabled (the default), every Codex start, resume and restart receives a developer instruction to recursively discover and read all Markdown files below the workspace .claude directory before working. This includes .claude/CLAUDE.md and any other nested .md files. The extension does not copy or modify those rules, so .claude remains the single source of truth for both agents.

The bridge uses Codex's per-launch developer_instructions. If claudeTmux.codexArgs already defines that key, the bridge is skipped and the extension warns once instead of silently replacing the explicit value. An existing global Codex developer_instructions value is replaced for bridged launches; keep durable project constraints in .claude, or disable the bridge and compose the instruction yourself in codexArgs.

Codex is also started in Full Access by default. This was chosen for the requested workflow, but it disables Codex approvals and sandboxing. Turn off claudeTmux.codexFullAccess for repositories you do not fully trust.

Settings

The existing claudeTmux.* namespace is retained so upgrades keep current user settings.

Scope and limits

• A workspace folder is required; the extension never falls back to $HOME.
• In a multi-root workspace, the first root is used.
• With stateHooks off (or unmanaged launches), working, finished and needs input fall back to visual heuristics based on submitted input, pane changes and common prompts; they can occasionally be wrong.
• The control-mode client parks on a private _agentmux_ctl_<pid> session and rides along on the active agent session to receive push notifications; it is excluded from the footer's client count and cleans up after itself.
• Transcript telemetry parses the CLIs' local JSONL files, which are not a stable API; the chips silently disappear if a format changes.
• This is a terminal mirror, not a full PTY. Mouse input is not forwarded.
• Scrollback is bounded by claudeTmux.scrollbackLines and tmux's own history.
• Multi-line paste is sent raw and a newline may submit input.
• Pair Mode transfers a source-authored, target-specific snapshot and uses a best-effort terminal acknowledgement; it remains sequential and user-reviewed.
• A tab disappears when the agent TUI exits even if its tmux shell remains; the launcher can start the agent again in that workspace session.

See USER_GUIDE.md for troubleshooting and TESTING.md for the installation smoke test.