generate-regression-cases

generate-regression-cases is a skill for Claude Code from xiaolai/eou-foundry. It costs 231 tokens per session (1,131 once invoked), scanned A, original, ISC.

A tool for turning incident reports or audit failures into proposed regression tests, which are checks that help prevent a bug from returning.

In plain words
What is it for?
Use it to create candidate regression cases from files describing errors, wrong output, missing files, or format mismatches.
Why use it?
It records the visible failure, its category, and the expected result in a defined format, while leaving activation for a human owner.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: $skill-name invocation.

Part of the eou-foundry plugin — 14 skills, 1 command shipped together

Good fit Use it to create candidate regression cases from files describing errors, wrong output, missing files, or format mismatches.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/xiaolai/eou-foundry/generate-regression-cases
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.

Any agent
npx skills add xiaolai/eou-foundry --skill generate-regression-cases
Clone the repo
git clone --depth 1 https://github.com/xiaolai/eou-foundry

Made for: Claude Code.

Or install eou-foundry, the plugin that ships this one along with the rest of its 14 skills, 1 command.

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 generate-regression-cases

README.md
[![agentmods](https://agentmods.dev/badge/skills/xiaolai/eou-foundry/generate-regression-cases.svg)](https://agentmods.dev/skills/xiaolai/eou-foundry/generate-regression-cases)
Your own site
<a href="https://agentmods.dev/skills/xiaolai/eou-foundry/generate-regression-cases"><img src="https://agentmods.dev/badge/skills/xiaolai/eou-foundry/generate-regression-cases.svg" alt="Measured on agentmods" height="20"></a>
Per session 231 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,131 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00231 $0.01131
Opus 5 $0.00115 $0.00566
Sonnet 5 $0.00046 $0.00226
Haiku 4.5 $0.00023 $0.00113

Measured 8d ago against content hash ca89525a5e68, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

generate-regression-cases 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 8d 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/generate-regression-cases/SKILL.md · 91 lines

How it starts

The opening of the file, as written. The whole thing — 91 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Generate Regression Cases

Convert $source (one or more incident reports or audit failures) into candidate regression cases.

Inputs

  • $source (required) — path to one or more incident reports or audit failure files. Accepts a direct file path or a glob (e.g., foundry/audits/incidents/*.yml). Every matched file must contain at least one observable failure symptom.

Required reading

  1. foundry/failure-taxonomy.yml — classify each failure by F-code
  2. foundry/constitution.yml — invariants that constrain what counts as a valid regression case
  3. schemas/incident.schema.yml — validate structured YAML incident files against this schema
  4. schemas/regression-case.schema.yml — the schema for the output regression case files

Stop conditions

Halt and report before generating cases if:

  • $source resolves to no readable files.
  • No observable failure symptom can be extracted from any source file — labels and conclusions without at least one observable symptom (error message, wrong output, missing artifact, schema mismatch) are not accepted as source input.
  • schemas/regression-case.schema.yml does not exist — cannot validate output structure.

Procedure

  1. Load $source. If it is a glob, read all matching files.
  2. For each incident or audit failure, extract the observable failure symptom.
  3. Classify the failure using foundry/failure-taxonomy.yml (F1–F12).
  4. Derive the regression case: the minimal input that reproducibly triggers the failure.
  5. Construct the fixture path: foundry/self-evolution/regression/fixtures/{case_id}/.
  6. Check foundry/self-evolution/regression/cases/ for existing cases that cover this failure — skip if a duplicate exists; record the duplicate case ID instead.
  7. For each new case, write the regression case file with all required fields.
  8. Set activation_status: candidate on all generated cases — never active.

Required fields per case (per schemas/regression-case.schema.yml)

id:                   # regression-{eou_id}-{failure_class}-{YYYYMMDD}
source_incident_id:   # incident or audit ID this case was derived from
failure_class:        # F1-F12 code
eou_id:               # EOU that exhibited the failure
fixture_path:         # foundry/self-evolution/regression/fixtures/{case_id}/
failure_shape_assertion:  # observable output that indicates the failure is occurring (non-empty)
activation_status:    # candidate — never active without human approval

Read the full file on GitHub · 91 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. 8d ago First seen · 91 lines · 231 tokens per session scan A ca89525a5e68

Subscribe to this mod's changes

generate-regression-cases is a skill published in the GitHub repository xiaolai/eou-foundry (10 stars, last pushed 14d ago), licensed ISC. It adds 231 tokens to every session and 1,131 once invoked, about $0.0012 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 2026-08-31.

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