external-llm-consulting

name	external-llm-consulting
description	Get architecture and design second opinions from external LLMs (OpenAI Codex, Google Gemini) via their CLIs. Use when you need alternative perspectives on design decisions, model selection, or structured comparison of approaches.
allowed-tools	Bash Read Grep Glob

External LLM Consulting

Audience: Developers seeking alternative AI perspectives on architecture and design decisions. Goal: Invoke external LLM CLIs in read-only/sandbox mode to get structured second opinions, then present results for comparison with Claude's perspective.

When to Use

• Validating architectural choices with diverse AI perspectives
• Exploring alternative approaches Claude might not consider
• High-stakes design decisions benefiting from model diversity
• Surfacing blind spots through cross-model analysis

General Workflow

1. Gather relevant context (CLAUDE.md, AGENTS.md, existing code patterns, constraints)
2. Formulate a focused prompt with context, specific questions, and structured output request
3. Execute the external CLI in sandbox/read-only mode
4. Parse and structure the response for comparison

Codex Consulting

Prerequisites

• Codex CLI installed (codex --version to verify)
• OpenAI authentication configured (codex login)

Available Models

Model	Use Case	Cost
gpt-5.1-codex-mini	Fast, cost-effective (~4x more usage)	Low
gpt-5.1-codex	Balanced, optimized for agentic tasks (default)	Medium
gpt-5.1-codex-max	Maximum intelligence for critical decisions	High

Parse model from prompt if specified (e.g., "using codex-mini, analyze..." or "model: gpt-5.1-codex-max").

CLI Execution

Run Codex in read-only sandbox mode:

codex exec --sandbox read-only --model <model> "<prompt>"

Important flags:

• --sandbox read-only - Prevents any code modifications
• --model <model> - Model to use (default: gpt-5.1-codex)

For complex prompts, use heredoc:

codex exec --sandbox read-only --model gpt-5.1-codex "$(cat <<'EOF'
Context: [codebase context]

Question: [specific architectural question]

Please provide:
1. 2-3 alternative approaches
2. Trade-offs for each approach
3. Your recommendation with reasoning
EOF
)"

Codex Error Handling

Error	Resolution
CLI not found	Install: npm install -g @openai/codex then codex login
Auth failed	Run: codex login
Timeout (>2 min)	Report partial results or simplify the query

Gemini Consulting

Prerequisites

• Gemini CLI installed (gemini --version to verify)
• Google authentication configured

Available Models

Model	Use Case	Cost
gemini-2.5-flash	Fast, cost-effective consulting	Low
gemini-2.5-pro	Balanced reasoning	Medium
gemini-3.0-pro-preview	Latest Gemini 3 Pro (default)	Medium

Parse model from prompt if specified (e.g., "using flash, analyze..." or "model: gemini-3.0-pro-preview").

CLI Execution

Run Gemini in sandbox mode:

gemini --sandbox --output-format text --model <model> "<prompt>"

Important flags:

• --sandbox - Prevents any code modifications
• --output-format text - Returns plain text (vs json/stream-json)
• --model <model> - Model to use (default: gemini-3.0-pro-preview)

For complex prompts, use heredoc:

gemini --sandbox --output-format text --model gemini-3.0-pro-preview "$(cat <<'EOF'
Context: [codebase context]

Question: [specific architectural question]

Please provide:
1. 2-3 alternative approaches
2. Trade-offs for each approach
3. Your recommendation with reasoning
EOF
)"

Gemini Error Handling

Error	Resolution
CLI not found	Install: npm install -g @anthropic-ai/gemini-cli / See https://github.com/google-gemini/gemini-cli
Auth failed	Run gemini and follow authentication prompts
Timeout (>2 min)	Report partial results or simplify the query

Prompt Formulation

Create a focused prompt that:

• Provides necessary context about the codebase
• Asks specific questions about the decision
• Requests structured output (options with trade-offs)

Include relevant sections from CLAUDE.md/AGENTS.md and any project constraints mentioned in the user's request.

Output Format

## [Codex/Gemini] Consulting Results

**Query:** [Original question/topic]

**Model:** [model used] (via [Codex/Gemini] CLI)

### Alternative Perspectives

#### Option 1: [Name]
- **Approach:** [Description]
- **Pros:** [Benefits]
- **Cons:** [Drawbacks]

#### Option 2: [Name]
- **Approach:** [Description]
- **Pros:** [Benefits]
- **Cons:** [Drawbacks]

#### Option 3: [Name]
- **Approach:** [Description]
- **Pros:** [Benefits]
- **Cons:** [Drawbacks]

### Recommendation
[LLM's preferred approach and reasoning]

### Key Insights
- [Insight 1 - something Claude might not have considered]
- [Insight 2]
- [Insight 3]

### Raw Output
<details>
<summary>Full Response</summary>

[Complete unedited response]

</details>

Safety Constraints

• Always use sandbox/read-only mode - Never allow code modifications
• No secrets in prompts - Don't include API keys, credentials, or sensitive data
• Verify responses - External LLM suggestions are opinions, not authoritative answers