behavior-validation

A testing method that checks a running application through the same public interfaces a user or operator would use, based on a written behavior contract. It does not inspect the source code.

In plain words
What is it for?
It is for acceptance checks, runtime proof, release smoke tests, API or CLI checks, browser checks, and testing invalid, interrupted, retry, persistence, or permission cases when required.
Why use it?
It shows whether the product actually behaves as promised and can expose fake, stale, broken, or incomplete behavior.

Skill for Claude CodeCodex

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 skills/thiientv/godmode/behavior-validation
Any agent
npx skills add thiientv/godmode --skill behavior-validation
Clone the repo
git clone --depth 1 https://github.com/thiientv/godmode

Made for: Claude Code, Codex.

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 418 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 $0.00080 $0.00418
Opus 5 $0.00040 $0.00209
Sonnet 5 $0.00016 $0.00084
Haiku 4.5 $0.00008 $0.00042

Measured 2d ago against content hash d8738f5f1244, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

behavior-validation 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.

skills/behavior-validation/SKILL.md · 48 lines

What it actually says

Behavior Validation

Judge what the product does, not how its source appears to do it.

Establish isolation

Write or read the behavior contract before exercising the target. Use behavior-contract.md. The contract must name user tasks, expected outcomes, setup, allowed interfaces, negative cases, and required evidence.

Do not inspect source, diffs, internal tests, Git history, or implementation notes during validation. Interact only through public browser, CLI, API, artifact, accessibility, or operator surfaces. If source is required, mark the clause blocked and hand it to root-cause-debugging.

Exercise the contract

  1. Run each task through the same entry point a real user or operator uses.
  2. Vary input and state to detect hard-coded success, stale data, or display-only behavior.
  3. Test invalid, empty, interrupted, retry, persistence, and permission paths where the contract makes them relevant.
  4. Capture redacted screenshots, terminal excerpts, response summaries, or artifact facts.
  5. Mark every clause pass, fail, blocked, or out of scope. Lack of evidence is not a pass.

When a finding is fixed, rerun the failed clause and nearby regression probes; do not rerun unrelated expensive scenarios without reason.

Completion condition

Every relevant contract clause has a status and reproducible evidence, anti-fake probes were attempted, secrets and private data were excluded, and the report does not infer implementation defects from observable symptoms.

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 48 lines · 80 tokens per session scan A d8738f5f1244

Subscribe to this mod's changes

behavior-validation is a skill published in the GitHub repository thiientv/godmode (93 stars, last pushed 7d ago), licensed MIT. It adds 80 tokens to every session and 418 once invoked, about $0.0004 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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