gemini

# Gemini Skill Guide

## When to Use Gemini
- WHEN ASKED TO BE ACTIVATED
- **Code Review**: Comprehensive code reviews across multiple files
- **Plan Review**: Analyzing architectural plans, technical specifications, or project roadmaps
- **Big Context Processing**: Tasks requiring >200k tokens of context (entire codebases, documentation sets)
- **Multi-file Analysis**: Understanding relationships and patterns across many files

## ⚠️ Critical: Background/Non-Interactive Mode Warning

**NEVER use `--approval-mode default` in background or non-interactive shells** (like Claude Code tool calls). It will hang indefinitely waiting for approval prompts that cannot be provided.

**For automated/background reviews:**
- ✅ Use `--approval-mode yolo` for fully automated execution
- ✅ OR wrap with timeout: `timeout 300 gemini ...`
- ❌ NEVER use `--approval-mode default` without interactive terminal

**Symptoms of hung Gemini:**
- Process running 20+ minutes with 0% CPU usage
- No network activity
- Process state shows 'S' (sleeping)

**Fix hung process:**
```bash
# Check if hung
ps aux | grep gemini | grep -v grep

# Kill if necessary
pkill -9 -f "gemini.*gemini-3-pro-preview"
```

## Running a Task

1. Ask the user (via `AskUserQuestion`) which model to use in a **single prompt**. Available models:
   - `gemini-3-pro-preview` ⭐ (flagship model, best for coding & complex reasoning, 35% better at software engineering than 2.5 Pro)
   - `gemini-3-flash` (sub-second latency, distilled from 3 Pro, best for speed-critical tasks)
   - `gemini-2.5-pro` (legacy option, strong all-around performance)
   - `gemini-2.5-flash` (legacy option, cost-efficient with thinking capabilities)
   - `gemini-2.5-flash-lite` (legacy option, fastest processing)

2. Select the approval mode based on the task:
   - `default`: Prompt for approval (⚠️ ONLY for interactive terminal sessions)
   - `auto_edit`: Auto-approve edit tools only (for code reviews with suggestions)
   - `yolo`: Auto-approve all tools (✅ REQUIRED for background/automated tasks)

3. Assemble the command with appropriate options:
   - `-m, --model <MODEL>` - Model selection
   - `--approval-mode <default|auto_edit|yolo>` - Control tool approval
   - `-y, --yolo` - Alternative to `--approval-mode yolo`
   - `-i, --prompt-interactive "prompt"` - Execute prompt and continue interactively
   - `--include-directories <DIR>` - Additional directories to include in workspace
   - `-s, --sandbox` - Run in sandbox mode for isolation

4. **For background/automated tasks, ALWAYS use `--approval-mode yolo`** or add timeout wrapper. NEVER use `default` in non-interactive shells.

5. Run the command and capture the output. For background/automated mode:
   ```bash
   # Recommended: Use yolo for background tasks
   gemini -m gemini-3-pro-preview --approval-mode yolo "Review this codebase for security issues"

   # Or with timeout (5 min limit)
   timeout 300 gemini -m gemini-3-pro-preview --approval-mode yolo "Review this codebase"
   ```

6. For interactive sessions with an initial prompt:
   ```bash
   gemini -m gemini-3-pro-preview -i "Review the authentication system" --approval-mode auto_edit
   ```

7. **After Gemini completes**, inform the user: "The Gemini analysis is complete. You can start a new Gemini session for follow-up analysis or continue exploring the findings."

## Safety Boundaries

- Do not run Gemini unless the user explicitly asked for Gemini or for a second-opinion review that justifies it.
- Do not use `--approval-mode yolo` unless the task is non-interactive and the user approved high-autonomy execution.
- Do not save reports or write files unless the user asked for an artifact.
- Do not pass secrets, private keys, or unrelated workspace data into prompts.

### Quick Reference

| Use case | Approval mode | Key flags |
| --- | --- | --- |
| Background code review | `yolo` ✅ | `-m gemini-3-pro-preview --approval-mode yolo` |
| Background analysis | `yolo` ✅ | `-m gemini-3-pro-preview --approval-mode yolo` |
| Background with timeout | `yolo` ✅ | `timeout 300 gemini -m gemini-3-pro-preview --approval-mode yolo` |
| Interactive code review | `default` | `-m gemini-3-pro-preview --approval-mode default` (interactive terminal only) |
| Code review with auto-edits | `auto_edit` | `-m gemini-3-pro-preview --approval-mode auto_edit` |
| Automated refactoring | `yolo` | `-m gemini-3-pro-preview --approval-mode yolo` |
| Speed-critical background | `yolo` ✅ | `-m gemini-3-flash --approval-mode yolo` |
| Cost-optimized background | `yolo` ✅ | `-m gemini-2.5-flash --approval-mode yolo` |
| Multi-directory analysis | `yolo` (if background) | `--include-directories <DIR1> --include-directories <DIR2>` |
| Interactive with prompt | `auto_edit` or `default` | `-i "prompt" --approval-mode <mode>` |

### Model Selection Guide

| Model | Best for | Context window | Key features |
| --- | --- | --- | --- |
| `gemini-3-pro-preview` ⭐ | **Flagship model**: Complex reasoning, coding, agentic tasks | 1M input / 64k output | Vibe coding, 76.2% SWE-bench |
| `gemini-3-flash` | Sub-second latency, speed-critical applications | 1M input / 64k output | Distilled from 3 Pro, TPU-optimized |
| `gemini-2.5-pro` | Legacy: Strong all-around performance | 1M input / 65k output | Thinking mode, mature stability |
| `gemini-2.5-flash` | Legacy: Cost-efficient, high-volume tasks | 1M input / 65k output | Thinking mode |
| `gemini-2.5-flash-lite` | Legacy: Fastest processing, high throughput | 1M input / 65k output | Maximum speed, minimal latency |

**Gemini 3 Advantages**: 35% higher accuracy in software engineering, state-of-the-art on SWE-bench (76.2%), GPQA Diamond (91.9%), and WebDev Arena (1487 Elo). Knowledge cutoff: January 2025.

**Coming Soon**: `gemini-3-deep-think` for ultra-complex reasoning with enhanced thinking capabilities.

## Common Use Cases

### Code Review (Background/Automated)
```bash
# For background execution (Claude Code, CI/CD, etc.)
gemini -m gemini-3-pro-