Second Opinion Gemini

Second Opinion — Gemini (explicit / fallback engine)

Get an independent second opinion from Google's Gemini Pro. This model has a completely different architecture and training from Claude, making it genuinely useful for catching blind spots, validating reasoning on edge cases, or surfacing trade-offs you might miss.

This is NOT the default second-opinion engine. Generic second-opinion requests route to the default second-opinion skill. Use this Gemini skill only when:

• The user explicitly asks for Gemini ("ask Gemini", "Gemini's take", "what does Gemini think").
• The user says "ask both" — run this and the default second-opinion skill, then synthesize all three views (yours + the default engine's + Gemini's).
• The default engine was reported unavailable and the user wants the alternate independent voice.

Gemini has full read access to the project — it can read files, grep code, and explore the codebase. Its project instructions (GEMINI.md) tell it to prime itself on the key docs before answering. You provide the specific question and any focused context; Gemini handles the rest.

Model selection

Pinned to gemini-3.1-pro-preview by default for quality (smaller models give weaker second opinions; not worth the false confidence they create).

When Google deprecates the preview pin — preview models rotate fast — override per-session or globally:

export CLAUDE_SECOND_OPINION_MODEL=gemini-3.2-pro   # or whatever the current Pro-tier model is

Every invocation below uses the bash pattern ${CLAUDE_SECOND_OPINION_MODEL:-gemini-3.1-pro-preview} — the env var wins if set, otherwise the pinned default.

Do not fall back to a smaller/older model when the pin breaks. Report unavailability and continue with Claude-only analysis.

Process

Step 1: Prepare the Prompt

Gemini has NO access to your conversation history, but it CAN read project files. Structure your prompt as:

1. Scope (optional) — by default Gemini primes on the whole project. If the question is about one module or component, name it so Gemini reads the right files first (e.g., "This is about the auth module" — detect the relevant module from the file paths you've been working in).
2. The question — what exactly you want Gemini to weigh in on
3. Your current thinking (recommended) — share your position so Gemini can challenge it
4. Specific context (if needed) — pipe code snippets or diffs via stdin when the relevant code is scattered or you want to focus attention on specific sections

For questions about existing project code, you can simply reference file paths — Gemini will read them itself.

Step 2: Invoke Gemini

CRITICAL: Permission-free invocation pattern. The command MUST start with gemini (matches the Bash(gemini:*) allow rule) and MUST NOT use $() command substitution or /tmp/ file redirects — both trigger permission prompts.

Standard call (Gemini reads project files itself — preferred):

gemini -m "${CLAUDE_SECOND_OPINION_MODEL:-gemini-3.1-pro-preview}" -p '<your question here>' -o text

With context piped via stdin (for code snippets, diffs, or focused excerpts — use when context is scattered or you want to focus attention on specific sections):

gemini -m "${CLAUDE_SECOND_OPINION_MODEL:-gemini-3.1-pro-preview}" -p '<your question here>' -o text <<'CONTEXT_EOF'
<relevant code, diff, or context here>
CONTEXT_EOF

The Bash tool captures all output (stdout + stderr) directly — no file redirects needed. Gemini's stderr noise (Loading, Registering, Scheduling, etc.) appears in the output but is easily identified and ignored.

Output markers that mean Gemini did NOT answer:

• Capacity exhausted (transient): MODEL_CAPACITY_EXHAUSTED, No capacity available, code.*429. Retry later or proceed without second opinion.
• Model deprecated (permanent): model not found, MODEL_NOT_FOUND, unknown model, model_id_invalid, or 404 paired with the model name. The pinned model is dead — see the unavailable-block below.

Required flags — no exceptions:

DO NOT use:

• $() command substitution (e.g., GEMINI_RESPONSE=$(gemini ...)) — triggers "Command contains $() command substitution" permission prompt
• /tmp/ file redirects (e.g., 2>/tmp/gemini-stderr.txt) — triggers "allow access to tmp/" permission prompt
• Nested heredocs inside $() — same issue

Set a 600-second timeout on the Bash tool call (Gemini may need time to read files and reason through complex questions).