Collaborate with Gemini CLI

Overview

Gemini CLI in headless mode (-p) cannot execute shell commands or write files. Use tmux send-keys to control Gemini interactively while monitoring via capture-pane.

Quick Reference

Action	Command
Start (split pane)	`tmux split-window -h -d "cd PROJECT && gemini --yolo"`
Start (session)	`tmux new-session -d -s gemini -x 200 -y 50`
Send text	`tmux send-keys -t {right} 'task text'`
Send Enter	`tmux send-keys -t {right} Enter`
Check output	`tmux capture-pane -t {right} -p -S -100`
Clear input	`tmux send-keys -t {right} Escape Escape`
Kill pane	`tmux kill-pane -t {right}`
Kill session	`tmux kill-session -t gemini`

Target: {right} for split pane, gemini for named session.

Status Markers

Detect Gemini state by grepping capture-pane output:

Marker	State
`Type your message`	Idle, ready for input
`esc to cancel`	Working on task
`✓ built` / `✓ Shell`	Action completed
`Found \d+ errors`	Build failed
`error TS`	TypeScript error
`potential loop`	Needs intervention (send `2` + Enter)
`Waiting for auth`	OAuth expired

Workflow

bash

# 1. Start Gemini
tmux split-window -h -d "cd ~/project && gemini --yolo"
sleep 5

# 2. Send task (TWO separate calls - critical!)
tmux send-keys -t {right} 'Build the app per PLAN.md'
tmux send-keys -t {right} Enter

# 3. Poll for completion
while true; do
  output=$(tmux capture-pane -t {right} -p -S -50)

  # Check if idle (task done)
  if echo "$output" | grep -q "Type your message"; then
    break
  fi

  # Handle loop detection
  if echo "$output" | grep -q "potential loop"; then
    tmux send-keys -t {right} '2'
    tmux send-keys -t {right} Enter
  fi

  sleep 10
done

# 4. Check result
tmux capture-pane -t {right} -p -S -200 | tail -100

Common Mistakes

Mistake	Fix
`send-keys 'text' Enter` in one call	Enter doesn't register - send separately
Chaining: `send-keys && sleep && capture`	Commands leak into Gemini input - use separate bash calls
Fixed `sleep 60`	Use polling with status markers instead
Ignoring loop detection	Gemini hangs - detect and send `2`
Long prompts	Create `.gemini/commands/task.toml`

Custom Commands

For repeating tasks, create .gemini/commands/:

toml

# .gemini/commands/improve-design.toml
[command]
description = "Improve app design"

[[steps]]
prompt = "Improve design: gradients, shadows, animations. Run build when done."

Call: tmux send-keys -t {right} '/improve-design' + Enter

When NOT to Use

•Read-only analysis → gemini -p "analyze" --output-format json
•Simple questions → direct API call
•Need deterministic output → headless with JSON schema