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:

# 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:
2. gemini-3-pro-preview ⭐ (flagship model, best for coding & complex reasoning, 35% better at software engineering than 2.5 Pro)
3. gemini-3-flash (sub-second latency, distilled from 3 Pro, best for speed-critical tasks)
4. gemini-2.5-pro (legacy option, strong all-around performance)
5. gemini-2.5-flash (legacy option, cost-efficient with thinking capabilities)
6. gemini-2.5-flash-lite (legacy option, fastest processing)

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

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

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

1. 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" ```

1. For interactive sessions with an initial prompt:

``bash gemini -m gemini-3-pro-preview -i "Review the authentication system" --approval-mode auto_edit ``

1. 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."

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, $2-4/M input | | 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 | Best price ($0.15/M), 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)

# For background execution (Claude Code, CI/CD, etc.)
gemini -m gemini-3-pro-preview --approval-mode yolo \
  "Perform a comprehensive code review focusing on:
   1. Security vulnerabilities
   2. Performance issues
   3. Code quality and maintainability
   4. Best practices violations"

# With timeout safety (5 minutes)
timeout 300 gemini -m gemini-3-pro-preview --approval-mode yolo \
  "Perform a comprehensive code review..."

Plan Review (Background/Automated)

# For background execution
gemini -m gemini-3-pro-preview --approval-mode yolo \
  "Review this architectural plan for:
   1. Scalability concerns
   2. Missing components
   3. Integration challenges
   4. Alternative approaches"

Big Context Analysis (Background/Automated)

# For background execution
gemini -m gemini-3-pro-preview --approval-mode yolo \
  "Analyze the entire codebase to understand:
   1. Overall architecture
   2. Key patterns and conventions
   3. Potential technical debt
   4. Refactoring opportunities"

Interactive Code Review (Terminal Only)

# ONLY use default mode in interactive terminal
gemini -m gemini-3-pro-preview --approval-mode default \
  "Review the authentication flow for security issues"

Following Up

• Gemini CLI sessions are typically one-shot or interactive. Unlike Codex, there's no built-in resume functionality.
• For follow-up analysis, start a new Gemini session with context from previous findings.
• When proposing follow-up actions, restate the chosen model and approval mode.
• Use AskUserQuestion after each Gemini command to confirm next steps or gather clarifications.

Error Handling

• Stop and report failures whenever gemini --version or a Gemini command exits non-zero.
• Request direction before retrying failed commands.
• Before using high-impact flags (--approval-mode yolo, -y, --sandbox), ask the user for permission using AskUserQuestion unless already granted.
• When output includes warnings or partial results, summarize them and ask how to adjust using AskUserQuestion.

Troubleshooting Hung Gemini Processes

Detection

# Check for hung processes
ps aux | grep -E "gemini.*gemini-3" | grep -v grep

# Look for these symptoms:
# - Process running 20+ minutes
# - CPU usage at 0%
# - Process state 'S' (sleeping)
# - No network connections

Diagnosis

# Get detailed process info
ps -o pid,etime,pcpu,stat,com