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Google Gemini CLI for second opinions, architectural advice, code reviews, security audits. Leverage 1M+ context for comprehensive codebase analysis via command-line tool.
One skill from claude-skills .
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Google Gemini CLI for second opinions, architectural advice, code reviews, security audits. Leverage 1M+ context for comprehensive codebase analysis via command-line tool. 📦 Ships with claude-skills
</> SKILL.md
gemini-cli.SKILL.md
---
name : gemini-cli
description : "Google Gemini CLI for second opinions, architectural advice, code reviews, security audits. Leverage 1M+ context for comprehensive codebase analysis via command-line tool."
license : MIT
metadata:
version: 2.1.0
production_tested: true
gemini_cli_version: 0.13.0+
last_verified: 2025-11-13
token_savings: ~60-70%
errors_prevented: 6+
keywords:
- gemini-cli
- google gemini
- gemini command line
- second opinion
- model comparison
- gemini-2.5-flash
- gemini-2.5-pro
- architectural decisions
- debugging assistant
- code review gemini
- security audit gemini
- 1M context window
- AI pair programming
- gemini consultation
- flash vs pro
- AI-to-AI prompting
- peer review
- codebase analysis
- gemini CLI tool
- shell gemini
- command line AI assistant
- gemini architecture advice
- gemini debug help
Flowy AI Flows that just work. Hand-picked Claude Code plugins that fire the right skill as you prompt.
- gemini security scan
- gemini code compare
---
# Gemini CLI
**Leverage Gemini's 1M+ context window as your AI pair programmer within Claude Code workflows.**
This skill teaches Claude Code how to use the official Google Gemini CLI (`gemini` command) to get second opinions, architectural advice, debugging help, and comprehensive code reviews. Based on production testing with the official CLI tool.
---
## Table of Contents
1. [Quick Start](#quick-start)
2. [When to Use Gemini Consultation](#when-to-use-gemini-consultation)
3. [Installation](#installation)
4. [Model Selection: Flash vs Pro](#model-selection-flash-vs-pro)
5. [Top 3 Use Cases](#top-3-use-cases)
6. [Integration Example](#integration-example)
7. [Top 3 Errors & Solutions](#top-3-errors--solutions)
8. [When to Load References](#when-to-load-references)
9. [Production Rules](#production-rules)
---
## Quick Start
**Prerequisites**:
- Gemini CLI installed (`bun add -g @google/gemini-cli`)
- Authenticated with Google account (run `gemini` once to authenticate)
**Core Command Patterns**:
```bash
# Quick question (non-interactive with -p flag)
gemini -p "Should I use D1 or KV for session storage?"
# Code review with file context
cat src/auth.ts | gemini -p "Review this authentication code for security vulnerabilities"
# Architecture advice using Pro model
gemini -m gemini-2.5-pro -p "Best way to handle WebSockets in Cloudflare Workers?"
# With all files in directory
gemini --all-files -p "Review this auth implementation for security issues"
# Interactive mode for follow-up questions
gemini -i "Help me debug this authentication error"
```
**Critical**: Always use `-p` flag for non-interactive commands in automation/scripts.
---
## When to Use Gemini Consultation
### ALWAYS Consult (Critical Scenarios)
Claude Code should **automatically invoke Gemini** in these situations:
1. **Major Architectural Decisions**
- Example: "Should I use D1 or KV for session storage?"
- Example: "Durable Objects vs Workflows for long-running tasks?"
- **Pattern**: `gemini -m gemini-2.5-pro -p "[architectural question]"`
2. **Security-Sensitive Code Changes**
- Authentication systems, payment processing, PII handling
- API key/secret management
- **Pattern**: `cat [security-file] | gemini -m gemini-2.5-pro -p "Security audit this code"`
3. **Stuck Debugging (2+ Failed Attempts)**
- Error persists after 2 debugging attempts
- Stack trace unclear or intermittent bugs
- **Pattern**: `gemini -p "Help debug: [error message]" < error.log`
4. **Large Refactors (5+ Files)**
- Core architecture changes, database schema migrations
- **Pattern**: `gemini --all-files -m gemini-2.5-pro -p "Review this refactoring plan"`
5. **Context Window Pressure (70%+ Full)**
- Approaching token limit, need to offload analysis
- **Pattern**: `cat large-file.ts | gemini -p "Analyze this code structure"`
### OPTIONALLY Consult
6. **Unfamiliar Technology** - Using library/framework for first time
7. **Code Reviews** - Before committing major changes
---
## Installation
### 1. Install Gemini CLI
```bash
bun add -g @google/gemini-cli
```
### 2. Authenticate
```bash
gemini
```
Follow the authentication prompts to link your Google account.
### 3. Verify Installation
```bash
gemini --version # Should show 0.13.0+
gemini -p "What is 2+2?" # Test connection
```
---
## Model Selection: Flash vs Pro
### gemini-2.5-flash (Default)
- **Speed**: ~5-25 seconds
- **Quality**: Good for most tasks
- **Use For**: Code reviews, debugging, quick questions
- **Cost**: Lower
```bash
gemini -m gemini-2.5-flash -p "Review this function for performance issues"
```
### gemini-2.5-pro
- **Speed**: ~15-30 seconds
- **Quality**: Excellent, thorough analysis
- **Use For**: Architecture decisions, security audits, major refactors
- **Cost**: Higher
```bash
gemini -m gemini-2.5-pro -p "Security audit this authentication system"
```
### Quick Decision Guide
```
Quick question? → Flash
Security/architecture? → Pro
Debugging? → Flash (try Pro if stuck)
Refactoring 5+ files? → Pro
```
**CRITICAL FINDING**: Flash and Pro can give **opposite recommendations** on the same question (both valid, different priorities). Flash prioritizes performance, Pro prioritizes consistency/correctness. For details, load `references/models-guide.md`.
---
## Top 3 Use Cases
### 1. Security Audit
```bash
# Audit authentication code
cat src/middleware/auth.ts | gemini -m gemini-2.5-pro -p "
Security audit this authentication middleware. Check for:
1. Token validation vulnerabilities
2. Timing attack risks
3. Error handling leaks
4. CSRF protection
5. Rate limiting
"
```
### 2. Architecture Decision
```bash
# Compare technologies with context
gemini -m gemini-2.5-pro -p "
Context: Building Cloudflare Worker with user authentication.
Question: Should I use D1 or KV for storing session data?
Considerations:
1. Session reads on every request
2. TTL-based expiration
3. Cost under 10M requests/month
4. Deployment complexity
"
```
### 3. Debugging Root Cause
```bash
# Analyze error logs with context
tail -100 error.log | gemini -p "
These errors started after deploying auth changes. What's the likely root cause?
Context:
- Added JWT validation middleware
- Using @cloudflare/workers-jwt
- Errors only on /api/* routes
"
```
**For more use cases**: Load `references/models-guide.md` for performance optimization, refactoring plans, and code reviews.
---
## Integration Example
### Claude Consulting Gemini Automatically
**Scenario**: User asks architectural question
```
User: "Should I use D1 or KV for storing user sessions?"
Claude (internal): This is an architectural decision. Consult Gemini for second opinion.
[Runs: gemini -m gemini-2.5-pro -p "Compare D1 vs KV for user session storage in Cloudflare Workers. Consider: read/write patterns, cost, performance, complexity."]
Claude (to user): "I've consulted Gemini for a second opinion. Here's what we both think:
My perspective: [Claude's analysis]
Gemini's perspective: [Gemini's analysis]
Key differences: [synthesis]
Recommendation: [combined recommendation]"
```
**Key Pattern**: Synthesize both perspectives, don't just forward Gemini's response.
---
## Top 3 Errors & Solutions
### Error 1: Not Authenticated
**Error**: `Error: Not authenticated`
**Solution**:
```bash
gemini # Follow authentication prompts
```
### Error 2: Model Not Found
**Error**: `Error: Model not found: gemini-2.5-flash-lite`
**Cause**: Model deprecated or renamed (flash-lite doesn't exist)
**Solution**: Use stable models only:
```bash
gemini -m gemini-2.5-flash -p "Your question"
gemini -m gemini-2.5-pro -p "Your question"
```
### Error 3: Command Hangs
**Cause**: Interactive mode when expecting non-interactive
**Solution**: Always use `-p` flag for non-interactive commands
```bash
# ✅ Correct
gemini -p "Question"
# ❌ Wrong (will hang waiting for input)
gemini "Question"
```
**For more troubleshooting**: Load `references/models-guide.md` for rate limits, large file context issues, and performance tips.
---
## When to Load References
Load reference files in these scenarios:
### Load `references/models-guide.md` when:
- User asks about Flash vs Pro differences
- Models give conflicting recommendations
- Need detailed performance comparison
- Choosing model for specific task type
- Want to understand why models disagree
### Load `references/prompting-strategies.md` when:
- Crafting complex prompts to Gemini
- Need AI-to-AI prompting format template
- Want to improve prompt quality
- Comparing old vs new prompting approaches
### Load `references/gemini-experiments.md` when:
- Need historical context on testing
- Investigating edge cases
- Understanding design decisions
- Troubleshooting unusual behavior
**Note**: `helper-functions.md` is obsolete (references old gemini-coach wrapper, not the official `gemini` CLI).
---
## Production Rules
### 1. Always Use `-p` for Automation
```bash
# ✅ Good for scripts
gemini -p "Question"
# ❌ Bad (interactive)
gemini
```
### 2. Select Model Based on Criticality
```bash
# Architecture/security → Pro
gemini -m gemini-2.5-pro -p "[critical question]"
# Debugging/review → Flash
gemini -m gemini-2.5-flash -p "[general question]"
```
### 3. Provide Context in Prompts
```bash
# ✅ Good: Context + Question + Considerations
gemini -p "Context: Building Cloudflare Worker. Question: Best auth pattern? Considerations: 1) Stateless, 2) JWT, 3) <100ms overhead"
# ❌ Bad: Vague
gemini -p "Best auth?"
```
### 4. Pipe File Content for Reviews
```bash
# ✅ Efficient
cat src/auth.ts | gemini -p "Review for security"
# ❌ Less efficient
gemini -p "Review src/auth.ts"
```
### 5. Synthesize, Don't Just Forward
**❌ BAD**: Just paste Gemini's response
```
Claude: [runs gemini] "Gemini says: [paste]"
```
**✅ GOOD**: Synthesize both perspectives
```
Claude: "I've consulted Gemini for a second opinion:
My analysis: [Claude's perspective]
Gemini's analysis: [Gemini's perspective]
Key differences: [synthesis]
Recommendation: [unified answer]"
```
### 6. Handle Errors Gracefully
```bash
if output=$(gemini -p "Question" 2>&1); then
echo "Gemini says: $output"
else
echo "Gemini consultation failed, proceeding with Claude's recommendation"
fi
```
---
## Version History
**2.1.0** (2025-12-15):
- Optimized to <500 lines (Phase 12.5 → 13 condensation)
- Extracted detailed content to references/
- Added "When to Load References" section
- Condensed to top 3 errors, top 3 use cases
**2.0.0** (2025-11-13):
- Complete rewrite for official Gemini CLI (removed gemini-coach wrapper)
- Direct CLI integration patterns
- Updated command examples for `gemini` CLI v0.13.0+
**1.0.0** (2025-11-08):
- Initial release with gemini-coach wrapper
---
## Related Skills
- [google-gemini-api](../google-gemini-api/) - Gemini API integration via SDK
- [google-gemini-embeddings](../google-gemini-embeddings/) - Gemini embeddings for RAG
- [google-gemini-file-search](../google-gemini-file-search/) - Managed RAG with Gemini
---
## License
MIT - See [LICENSE](../../LICENSE)
---
## Support
- **Issues**: https://github.com/jezweb/claude-skills/issues
- **Email**: jeremy@jezweb.net
- **Official Gemini CLI**: https://github.com/google-gemini/gemini-cli
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