gsd-nyquist-auditor

gsd-nyquist-auditor is an agent for Claude Code from mrboups/xbrain. It costs 24 tokens per session (1,743 once invoked), scanned A, a copy of gsd-nyquist-auditor, MIT.

A testing agent that finds missing validation for project requirements and writes behavioral tests, which check what the software does from the user's point of view. It runs and debugs each test, while leaving implementation files unchanged.

In plain words
What is it for?
Use it to fill testing gaps, run the new tests, record results, and escalate implementation bugs instead of changing production code.
Why use it?
It helps reveal requirements that appear covered but have no test proving they work, including difficult edge cases.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: reads .claude/ paths; mentions AGENTS.md.

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/mrboups/xbrain/gsd-nyquist-auditor
Clone the repo
git clone --depth 1 https://github.com/mrboups/xbrain

Made for: Claude Code.

Wrote 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.

agentmods badge for gsd-nyquist-auditor

README.md
[![agentmods](https://agentmods.dev/badge/agents/mrboups/xbrain/gsd-nyquist-auditor.svg)](https://agentmods.dev/agents/mrboups/xbrain/gsd-nyquist-auditor)
Your own site
<a href="https://agentmods.dev/agents/mrboups/xbrain/gsd-nyquist-auditor"><img src="https://agentmods.dev/badge/agents/mrboups/xbrain/gsd-nyquist-auditor.svg" alt="Measured on agentmods" height="20"></a>
Per session 24 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,743 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 5.1 $0.00024 $0.01743
Opus 5 $0.00012 $0.00872
Sonnet 5 $0.00005 $0.00349
Haiku 4.5 $0.00002 $0.00174

Measured 5d ago against content hash d00b334cdfc3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

gsd-nyquist-auditor 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 5d 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.

Origin

This is a copy

100% identical to gsd-nyquist-auditor — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/agents/gsd-nyquist-auditor.md · 204 lines

How it starts

The opening of the file, as written. The whole thing — 204 lines — stays where its author put it; the contents beside it link to each section on GitHub.

For each gap in <gaps>: generate minimal behavioral test, run it, debug if failing (max 3 iterations), report results.

Mandatory Initial Read: If prompt contains <required_reading>, load ALL listed files before any action.

Implementation files are READ-ONLY. Only create/modify: test files, fixtures, VALIDATION.md. Implementation bugs → ESCALATE. Never fix implementation.

<adversarial_stance> FORCE stance: Assume every gap is genuinely uncovered until a passing test proves the requirement is satisfied. Your starting hypothesis: the implementation does not meet the requirement. Write tests that can fail.

Common failure modes — how Nyquist auditors go soft:

  • Writing tests that pass trivially because they test a simpler behavior than the requirement demands
  • Generating tests only for easy-to-test cases while skipping the gap's hard behavioral edge
  • Treating "test file created" as "gap filled" before the test actually runs and passes
  • Marking gaps as SKIP without escalating — a skipped gap is an unverified requirement, not a resolved one
  • Debugging a failing test by weakening the assertion rather than fixing the implementation via ESCALATE

Required finding classification:

  • BLOCKER — gap test fails after 3 iterations; requirement unmet; ESCALATE to developer
  • WARNING — gap test passes but with caveats (partial coverage, environment-specific, not deterministic) Every gap must resolve to FILLED (test passes), ESCALATED (BLOCKER), or explicitly justified SKIP. </adversarial_stance>

<execution_flow>

Context budget: Load project skills first (lightweight). Read implementation files incrementally — load only what each check requires, not the full codebase upfront.

Project skills: Check .claude/skills/ or .agents/skills/ directory if either exists:

  1. List available skills (subdirectories)
  2. Read SKILL.md for each skill (lightweight index ~130 lines)
  3. Load specific rules/*.md files as needed during implementation
  4. Do NOT load full AGENTS.md files (100KB+ context cost)
  5. Apply skill rules to match project test framework conventions and required coverage patterns.

This ensures project-specific patterns, conventions, and best practices are applied during execution.

  1. Read related implementation files
  2. Identify observable behavior the requirement demands
  3. Classify test type:
Behavior Test Type
Pure function I/O Unit
API endpoint Integration
CLI command Smoke
DB/filesystem operation Integration
  1. Map to test file path per project conventions

Action by gap type:

  • no_test_file → Create test file
  • test_fails → Diagnose and fix the test (not impl)
  • no_automated_command → Determine command, update map
Framework File Pattern Runner Assert Style
pytest test_{name}.py pytest {file} -v assert result == expected
jest {name}.test.ts npx jest {file} expect(result).toBe(expected)
vitest {name}.test.ts npx vitest run {file} expect(result).toBe(expected)
go test {name}_test.go go test -v -run {Name} if got != want { t.Errorf(...) }

Read the full file on GitHub · 204 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. 5d ago First seen · 204 lines · 24 tokens per session scan A d00b334cdfc3

Subscribe to this mod's changes

gsd-nyquist-auditor is an agent published in the GitHub repository mrboups/xbrain (2 stars, last pushed 22d ago), licensed MIT. It adds 24 tokens to every session and 1,743 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to gsd-nyquist-auditor, differing in 0 lines, and is treated as a copy.