tools-only Gemini CLI Invocation
Default Configuration
- Model:
gemini-3-pro-preview - Extensions:
code-review,gemini-cli-security
Key Flags
| Flag | Purpose |
|---|---|
-p <prompt> |
Non-interactive (headless) mode |
--yolo / -y |
Auto-approve all tool calls |
-m <model> |
Model selection |
-e <ext> |
Load specific extension(s) |
Scope-to-Diff Mapping
Gemini does not have built-in scope flags like Codex. Map the
user's scope choice to the correct git diff command:
| Scope | Diff command |
|---|---|
| Uncommitted | git diff HEAD (captures both staged and unstaged) |
| Branch diff | git diff <branch>...HEAD |
| Specific commit | git diff <sha>~1..<sha> |
Important: For uncommitted scope, use git diff HEAD not
bare git diff. Bare git diff misses staged changes.
Code Review (General, Performance, Error Handling)
For uncommitted changes, the /code-review extension
automatically picks up the working tree diff:
gemini -p "/code-review" \
--yolo \
-e code-review \
-m gemini-3-pro-preview
For branch diffs or specific commits, pipe the diff into a heredoc-based prompt to avoid shell expansion issues:
git diff <branch>...HEAD > /tmp/review-diff.txt
cat <<'PROMPT' | gemini -p - \
-m gemini-3-pro-preview \
--yolo
Review this diff for code quality issues. <focus prompt>
$(cat /tmp/review-diff.txt)
PROMPT
Security Review
The /security:analyze extension is interactive-only, so use
headless mode with a security-focused prompt instead:
git diff HEAD > /tmp/review-diff.txt
cat <<'PROMPT' | gemini -p - \
-e gemini-cli-security \
-m gemini-3-pro-preview \
--yolo
Analyze this diff for security vulnerabilities, including
injection, auth bypass, data exposure, and input validation
issues. Report each finding with severity, location, and
remediation.
$(cat /tmp/review-diff.txt)
PROMPT
When security focus is selected, also run dependency scanning:
gemini -p "/security:scan-deps" \
--yolo \
-e gemini-cli-security \
-m gemini-3-pro-preview
Adding Project Context
If project context was requested, prepend it to the prompt:
git diff HEAD > /tmp/review-diff.txt
cat <<'PROMPT' | gemini -p - \
-m gemini-3-pro-preview \
--yolo
Project conventions:
---
<CLAUDE.md or AGENTS.md contents>
---
<review instructions and focus>
$(cat /tmp/review-diff.txt)
PROMPT
Error Handling
| Error | Action |
|---|---|
gemini: command not found |
Tell user: npm i -g @google/gemini-cli |
| Extension missing | Tell user: gemini extensions install <github-url> |
-e security silently ignored |
Use -e gemini-cli-security (the actual installed name) |
| Timeout | Inform user, suggest scoping down the diff |
Extension Install Commands
gemini extensions install https://github.com/gemini-cli-extensions/code-review
gemini extensions install https://github.com/gemini-cli-extensions/security
Note: The security extension installs as gemini-cli-security
(not security). Always use -e gemini-cli-security when
loading it.