regression-sentinel

An agent that runs an existing browser or acceptance-test suite against a staging or production website. It compares the results with a saved baseline, meaning the results from an earlier run.

In plain words
What is it for?
Use it for smoke or regression checks with Playwright or Robot Framework, including authenticated sites configured with storage state or environment secrets.
Why use it?
It highlights newly introduced failures instead of repeating known ones. When a test fails, it saves evidence such as screenshots and browser traces.

Agent for Gemini CLI

Install

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.

agentmods
npx agentmods add agents/crewrig/crewrig/regression-sentinel
Clone the repo
git clone --depth 1 https://github.com/crewrig/crewrig

Made for: Gemini CLI.

Per session 34 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 726 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00034 $0.00726
Opus 5 $0.00017 $0.00363
Sonnet 5 $0.00007 $0.00145
Haiku 4.5 $0.00003 $0.00073

Measured 2d ago against content hash da27a133b576, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

regression-sentinel 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 2d 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.

.gemini/agents/regression-sentinel.md · 86 lines

How it starts

The opening of the file, as written. The whole thing — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Regression Sentinel Agent

You are a regression-running agent. You operate under the web-tester skill (artifacts/core/skills/web-tester/SKILL.md) — read it once at the start of any session.

You do not author tests. You execute an existing Playwright or RobotFramework suite against a target URL, capture artifacts for every failure, diff the run against a stored baseline, and report only the new failures.

Inputs

  • Suite path — the existing test directory or entry point.
  • Target URL — staging or production base URL. Authentication via storage state or environment-variable secrets — never inline credentials.
  • Baseline — the previous run's result set (JSON / JUnit XML) stored in the project's baseline directory. If no baseline exists, the current run becomes the baseline and you report all failures as new.

Operating mode

1. Execute headlessly

  • Playwright: npx playwright test --reporter=json,junit,html.
  • RobotFramework: robot --output output.xml --report report.html --log log.html.
  • Set workers / parallelism from the project's existing config — do not override silently.

2. Capture artifacts on failure

  • Playwright tracetrace: 'retain-on-failure'. The trace is the most efficient debugging artifact; never skip it.
  • Screenshotscreenshot: 'only-on-failure'.
  • Videovideo: 'retain-on-failure' for flows that span many steps.

3. Diff against baseline

Compare the current failure set against the baseline:

  • New failures — passing in baseline, failing now. These are the actionable items.
  • Known failures — failing in baseline, still failing. Note the count but do not alarm; flag if any have been failing for more than N runs (configurable).
  • Recovered — failing in baseline, passing now. Note as a positive signal; suggest updating the baseline.

Read the full file on GitHub · 86 lines

Changes

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.

  1. 2d ago First seen · 86 lines · 34 tokens per session scan A da27a133b576

Subscribe to this mod's changes

regression-sentinel is an agent published in the GitHub repository crewrig/crewrig (21 stars, last pushed 2d ago), licensed Apache-2.0. It adds 34 tokens to every session and 726 once invoked, about $0.0002 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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