Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/anthropics/claude-code-base-action/claude-mdgit clone --depth 1 https://github.com/anthropics/claude-code-base-actionWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/anthropics/claude-code-base-action/claude-md)<a href="https://agentmods.dev/instructions/anthropics/claude-code-base-action/claude-md"><img src="https://agentmods.dev/badge/instructions/anthropics/claude-code-base-action/claude-md.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00404 | $0.00404 |
| Opus 5 | $0.00202 | $0.00202 |
| Sonnet 5 | $0.00081 | $0.00081 |
| Haiku 4.5 | $0.00040 | $0.00040 |
Grade A, and why
claude-code-base-action CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
CLAUDE.md
Common Commands
Development Commands
- Build/Type check:
bun run typecheck - Format code:
bun run format - Check formatting:
bun run format:check - Run tests:
bun test - Install dependencies:
bun install
Action Testing
- Test action locally:
./test-local.sh - Test specific file:
bun test test/prepare-prompt.test.ts
Architecture Overview
This is a GitHub Action that allows running Claude Code within GitHub workflows. The action consists of:
Core Components
- Action Definition (
action.yml): Defines inputs, outputs, and the composite action steps - Prompt Preparation (
src/index.ts): Runs Claude Code with specified arguments
Key Design Patterns
- Uses Bun runtime for development and execution
- JSON streaming output format for execution logs
- Composite action pattern to orchestrate multiple steps
- Provider-agnostic design supporting Anthropic API, AWS Bedrock, and Google Vertex AI
Provider Authentication
- Anthropic API (default): Requires API key via
anthropic_api_keyinput - AWS Bedrock: Uses OIDC authentication when
use_bedrock: true - Google Vertex AI: Uses OIDC authentication when
use_vertex: true
Testing Strategy
Local Testing
- Use
acttool to run GitHub Actions workflows locally test-local.shscript automates local testing setup- Requires
ANTHROPIC_API_KEYenvironment variable
Test Structure
- Unit tests for configuration logic
- Integration tests for prompt preparation
- Full workflow tests in
.github/workflows/test-base-action.yml
Important Technical Details
- Outputs execution logs as JSON to
/tmp/claude-execution-output.json - Timeout enforcement via
timeoutcommand wrapper - Strict TypeScript configuration with Bun-specific settings
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 59 lines · 404 tokens per session scan A ce9cf4cb97bf
claude-code-base-action CLAUDE.md is an instructions file published in the GitHub repository anthropics/claude-code-base-action (961 stars, last pushed 6d ago), licensed MIT. It adds 404 tokens to every session, about $0.0020 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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