Code Review Router

Routes code reviews to the optimal CLI (Gemini or Codex) based on change characteristics.

When NOT to Use This Skill

• For non-code reviews (documentation proofreading, prose editing)

• When reviewing external/third-party code you don't control

• For commit message generation (use a dedicated commit skill)

• When you need a specific reviewer (use that CLI directly)

Step 0: Environment Check

Verify we're in a git repository:

git rev-parse --git-dir 2>/dev/null || echo "NOT_A_GIT_REPO"

If not a git repo: Stop and inform the user: "This directory is not a git repository. Initialize with git init or navigate to a repo."

Step 1: Prerequisites Check

Verify both CLIs are available:

Check for Gemini CLI

which gemini || echo "GEMINI_NOT_FOUND"

Check for Codex CLI

which codex || echo "CODEX_NOT_FOUND"

If neither CLI is found: Stop and inform the user they need to install at least one:

• Gemini: Check Google's Gemini CLI installation docs

• Codex: Check OpenAI's Codex CLI installation docs

If only one CLI is available: Use that CLI (no routing needed).

If both are available: Proceed with routing analysis.

Step 2: Analyze Git Diff

Run these commands to gather diff statistics:

Get diff stats (staged + unstaged)

git --no-pager diff --stat HEAD 2>/dev/null || git --no-pager diff --stat

Get full diff for pattern analysis

git --no-pager diff HEAD 2>/dev/null || git --no-pager diff

Count changed files

git --no-pager diff --name-only HEAD 2>/dev/null | wc -l

Count total changed lines

git --no-pager diff --numstat HEAD 2>/dev/null | awk '{added+=$1; removed+=$2} END {print added+removed}'

If no changes detected: Report "Nothing to review - no uncommitted changes found." and stop.

Step 3: Calculate Complexity Score

Initialize complexity_score = 0 , then add points:

Condition Points Detection Method

Files changed > 10 +2 git diff --name-only | wc -l

Files changed > 20 +3 (additional, total +5)

Lines changed > 300 +2 git diff --numstat sum

Lines changed > 500 +3 (additional, total +5)

Multiple directories touched +1 Count unique dirs in changed files

Test files included +1 Files matching test , spec

Config files changed +1 Files: .config. , *.json , *.yaml , *.yml , *.toml

Database/schema changes +2 Files: migration , schema , .sql , prisma/

API route changes +2 Files in api/ , routes/ , containing endpoint , handler

Service layer changes +2 Files in services/ , service , provider

Step 4: Detect Language & Framework

Analyze file extensions and content patterns:

Primary Language Detection

.ts, .tsx → TypeScript .js, .jsx → JavaScript .py → Python .go → Go .rs → Rust .java → Java .rb → Ruby .php → PHP .cs → C# .swift → Swift .kt → Kotlin

Framework Detection (check imports/file patterns)

React/Next.js → "import React", "from 'react'", "next.config", pages/, app/ Vue → ".vue" files, "import Vue", "from 'vue'" Angular → "angular.json", "@angular/core" Django → "django", "models.py", "views.py", "urls.py" FastAPI → "from fastapi", "FastAPI(" Express → "express()", "from 'express'" NestJS → "@nestjs/", ".module.ts", ".controller.ts" Rails → "Gemfile" with rails, app/controllers/ Spring → "springframework", "@RestController"

Security-Sensitive Patterns

Detect by file path OR code content:

File paths:

/auth/ /security/ **/authentication **/authorization */middleware/auth

Code patterns (in diff content):

password\s*= api_key\s*= secret\s*= Bearer\s+ JWT .env credentials private_key access_token

Config files:

.env* credentials secrets *.pem *.key

Step 5: Apply Routing Decision Tree

Routing Priority Order (evaluate top-to-bottom, first match wins):

Priority 1: Pattern-Based Rules (Hard Rules)

Pattern Route Reason

Security-sensitive files/code detected Codex Requires careful security analysis

Files > 20 OR lines > 500 Codex Large changeset needs thorough review

Database migrations or schema changes Codex Architectural risk

API/service layer modifications Codex Backend architectural changes

Changes span 3+ top-level directories Codex Multi-service impact

Complex TypeScript (generics, type utilities) Codex Type system complexity

Pure frontend only (jsx/tsx/vue/css/html) Gemini Simpler, visual-focused review

Python ecosystem (py, Django, FastAPI) Gemini Strong Python support

Documentation only (md/txt/rst) Gemini Simple text review

Priority 2: Complexity Score (if no pattern matched)

Score Route Reason

≥ 6 Codex High complexity warrants deeper analysis

< 6 Gemini Moderate complexity, prefer speed

Priority 3: Default

→ Gemini (faster feedback loop for unclear cases)

Step 6: Execute Review

Explain Routing Decision

Before executing, output:

Code Review Routing

Changes detected:

• Files: [X] files changed
• Lines: [Y] lines modified
• Primary language: [language]
• Framework: [framework or "none detected"]

Complexity score: [N]/10

• [List contributing factors]

Routing decision: [Gemini/Codex]

• Reason: [primary reason for choice]

Executing review...

CLI Commands

Note: Gemini receives the diff via stdin (piped), while Codex has a dedicated review subcommand that reads the git context directly. If debugging, check that git diff HEAD produces output before running Gemini.

For Gemini:

Pipe diff to Gemini with review prompt

git --no-pager diff HEAD | gemini -p "Review this code diff for: 1) Code quality issues, 2) Best practices violations, 3) Potential bugs, 4) Security concerns, 5) Performance issues. Provide specific, actionable feedback."

For Codex:

Use dedicated 'review' subcommand for non-interactive code review

Note: --uncommitted and [PROMPT] are mutually exclusive

codex review --uncommitted

Step 7: Handle Failures with Fallback

If the chosen CLI fails (non-zero exit or error output):

Report the failure:

[Primary CLI] failed: [error message] Attempting fallback to [other CLI]...

Try the alternative CLI

If fallback also fails:

Both review CLIs failed.

• Gemini error: [error]
• Codex error: [error]

Please check CLI installations and try manually.

Step 8: Format Output

Present the review results clearly:

Code Review Results

Reviewed by: [Gemini/Codex] Routing: [brief reason]

[CLI output here]

Review complete. [X files, Y lines analyzed]

Quick Reference

Change Type Route Reason

React component styling Gemini Pure frontend

Django view update Gemini Python ecosystem

Single bug fix < 50 lines Gemini Simple change

New API endpoint + tests Codex Architectural

Auth system changes Codex Security-sensitive

Database migration Codex Schema change

Multi-service refactor Codex High complexity

TypeScript type overhaul Codex Complex types