Gemini CLI Large Context Analysis

Gemini CLI Large Context Analysis

Overview

Use Gemini CLI's massive context window (1M tokens) when analysis requires more context than available in current session. Ideal for codebase-wide searches, multi-file comparisons, and pattern discovery across large projects.

When to Use

• Analyzing entire codebases or large directories (100KB+)
• Comparing multiple large files simultaneously
• Understanding project-wide patterns or architecture
• Context window insufficient for current task
• Verifying feature implementations across codebase
• Research that needs to scan many files at once

Quick Reference

# Basic non-interactive analysis
gemini -p "@src/ Summarize architecture"

# Multiple directories
gemini -p "@src/ @tests/ Analyze test coverage"

# All project files
gemini --all-files -p "Project overview"

# Specific model (Pro = 1M context)
gemini -m gemini-2.5-pro -p "@src/ Deep analysis"

File/​Directory Inclusion Syntax

# Single file
gemini -p "@src/​main.py Explain this file"

# Multiple files
gemini -p "@package.json @src/​index.js Analyze dependencies"

# Entire directory (recursive)
gemini -p "@src/ Summarize architecture"

# Multiple directories
gemini -p "@src/ @tests/ Analyze test coverage"

# Current directory
gemini -p "@./ Project overview"

# Alternative: all files flag
gemini --all-files -p "Analyze project structure"

Research Patterns

Architecture Analysis

gemini -p "@src/
Describe:
1. Overall architecture pattern (MVC, Clean, etc.)
2. Key modules and their responsibilities
3. Data flow between components
4. External dependencies and integrations"

Feature Implementation Check

gemini -p "@src/ @lib/
Has [FEATURE] been implemented?
Show:
- Relevant files and functions
- Implementation approach
- Any gaps or incomplete areas"

Pattern Discovery

gemini -p "@src/
Find all instances of [PATTERN]:
- File paths
- Implementation variations
- Consistency assessment"

Security Audit

gemini -p "@src/ @api/
Security review:
- Input validation practices
- Authentication/​authorization patterns
- SQL injection protections
- XSS prevention measures"

Test Coverage Analysis

gemini -p "@src/ @tests/
Assess test coverage:
- Which modules have tests?
- Which are missing tests?
- Test quality (unit vs integration)
- Edge cases covered"

Integration with OpenCode Workflow

For Task-Constrained Research

When researching within task boundaries:

# 1. Include bead spec in context
gemini -p "@src/ @.beads/​artifacts/​bd-xxx/​spec.md
Research implementations matching spec constraints"

# 2. Save findings to bead artifacts
# Write to .beads/​artifacts/​bd-xxx/​research.md

Delegating Large Research to Gemini

In AGENTS.md or prompts, instruct agents:

When analysis requires more than 100KB of files:

1. Use Gemini CLI: `gemini -p "@[paths] [question]"`
2. Capture output
3. Synthesize findings in response

Output Options

# Plain text (default)
gemini -p "query"

# JSON for parsing
gemini -p "query" --output-format json

# Streaming for long ops
gemini -p "query" --output-format stream-json

Common Research Queries

• Architecture overview: gemini -p "@src/ Describe architecture"
• Find implementations: gemini -p "@src/ Where is [X] implemented?"
• Pattern audit: gemini -p "@src/ Find all [pattern] usages"
• Dependency analysis: gemini -p "@package.json @src/ Analyze dependency usage"
• Code quality: gemini -p "@src/ Identify code smells"
• Migration planning: gemini -p "@src/ Plan migration from [A] to [B]"

Configuration

Authentication

# Google login (free tier: 60 req/​min, 1000/​day)
gemini  # Follow OAuth flow

# Or API key
export GEMINI_API_KEY="your-key"

Model Selection

For most analysis tasks, gemini-2.5-pro is the best choice—it has a 1M token context window and handles code, text, and image analysis exceptionally well. This is the default model.

Use gemini-2.5-flash when you need faster responses and don't need the full context window.

Important: If you're analyzing images or screenshots, use gemini-2.5-pro. Image generation models like imagen-3.0-generate-002 are for creating new images, not understanding existing ones.

# Gemini 2.5 Pro (1M context) - default, best for analysis
gemini -p "query"

# Gemini Flash (faster, smaller context)
gemini -m gemini-2.5-flash -p "query"

Best Practices

1. Scope appropriately - Include only relevant directories
2. Be specific - Ask focused questions, not vague queries
3. Use for read-only analysis - Don't ask Gemini to modify files in non-interactive mode
4. Capture output - Redirect to file for long analyses: gemini -p "..." > analysis.md
5. Combine with local tools - Use Gemini for research, local tools for implementation

Limitations

• Non-interactive mode: no tool approvals (file writes, shell commands)
• @file syntax: best in interactive mode
• Network dependency: requires internet connection
• Rate limits: 60 req/​min free tier