Guardrails / claude

Claude answers CI in a format a program can read

claude/cli-structured-output@v1

Every headless Claude CLI invocation the build ran asked for structured output.

Id	claude/cli-structured-output
Version	v1
Category	claude
Default severity	warning
Interpreter	python3
Timeout	30 seconds
Violations tolerated	0
Collects	commands

Collectors

This guardrail doesn't gather anything itself. It relies on the collectors below, which the CLI runs once per build before any check, and reads what they found from GUARDRAIL_FACTS. If a collector collects nothing, this guardrail is skipped, not failed.

Collector	Gathers	Inputs it is given
commands	Every command the build executed, read from the session a running buildnote monitor records on the runner. This is what the job actually ran, not what a pipeline file says it would run.	none

The inputs above are this guardrail's own inputs, passed straight through to the collector. Setting one in buildnote.json changes what is collected, and two guardrails configured the same way share a single collection.

Configuration

{
  "guardrails": {
      "failOn": "error",
      "checks": [
          {
              "use": "claude/cli-structured-output@v1",
              "severity": "warning",
              "with": {
                  "formats": "json,stream-json"
              },
              "exemptions": []
          }
      ]
  }
}

Inputs

Input	Description	Default	Environment variable
formats	Comma separated --output-format values that count as structured.	json,stream-json	GUARDRAIL_INPUT_FORMATS

How to fix

Add --output-format json to the invocation:

claude -p --output-format json 'summarise what changed' > review.json

A headless run is read by a program, not a person, and reading prose means guessing: a step that greps the answer for FAIL passes the day the model words it differently. JSON returns the result, the cost and the session id as fields, so your job can branch on a value instead of on a phrasing.

More in claude

• claude/cli-safe-flags. No Claude CLI invocation the build ran asked to skip its approval step.
• claude/instructions-symlinked. CLAUDE.md is a symbolic link to AGENTS.md, not a second copy of it or missing altogether.

All 3 claude guardrails