anchor-repro

anchor-repro is a skill for Claude Code from lynxlangya/techne. It costs 52 tokens per session (1,141 once invoked), scanned A, original, MIT.

A bug-reproduction workflow that records a failing check before code is changed and runs the same check after the fix.

In plain words
What is it for?
Use it for failing tests, crashes, hangs, regressions, incorrect results, error messages, and other behavior that should change.
Why use it?
It prevents debugging from relying on assumptions and shows whether the reported behavior was actually corrected.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the techne plugin — 5 skills shipped together

Good fit Use it for failing tests, crashes, hangs, regressions, incorrect results, error messages, and other behavior that should change.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/lynxlangya/techne/anchor-repro
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 lynxlangya/techne --skill anchor-repro
Clone the repo
git clone --depth 1 https://github.com/lynxlangya/techne

Made for: Claude Code.

Or install techne, the plugin that ships this one along with the rest of its 5 skills.

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 anchor-repro

README.md
[![agentmods](https://agentmods.dev/badge/skills/lynxlangya/techne/anchor-repro/github.svg)](https://agentmods.dev/skills/lynxlangya/techne/anchor-repro)
Your own site
<a href="https://agentmods.dev/skills/lynxlangya/techne/anchor-repro"><img src="https://agentmods.dev/badge/skills/lynxlangya/techne/anchor-repro/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for anchor-repro

Your own site · 80×15
<a href="https://agentmods.dev/skills/lynxlangya/techne/anchor-repro"><img src="https://agentmods.dev/badge/skills/lynxlangya/techne/anchor-repro.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,141 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00052 $0.01141
Opus 5 $0.00026 $0.00571
Sonnet 5 $0.00010 $0.00228
Haiku 4.5 $0.00005 $0.00114

Measured 9d ago against content hash f2864103ae5d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

anchor-repro 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 9d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/repro_ledger.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/anchor-repro/SKILL.md · 113 lines

How it starts

The opening of the file, as written. The whole thing — 113 lines — stays where its author put it; the contents beside it link to each section on GitHub.

anchor-repro

Force the skipped move in debugging: observe the bug before editing, then prove the fix with the same observation.

Trigger Check

Use this skill when the task is to correct observable behavior that is currently wrong: a failing test, error message, stack trace, regression, crash, hang, wrong return value, wrong render, or "X does Y; it should do Z."

Do not use it for new features, refactors, renames, formatting, docs/copy changes, dependency bumps without a behavioral symptom, or performance work without a measurable probe.

Boundary test: can the wrongness be written as "running X currently produces Y; it should produce Z"? If yes, use this skill and make X the probe seed. If the statement cannot be formed from current information, ask for or find the missing observation before editing.

Forced Procedure

  1. Capture the symptom and stable anchor. Choose the most stable literal substring of the observable symptom for --expect. Omit heap addresses, PIDs, timestamps, temp paths, and wrapped fragments. Use --expect whenever the symptom has stable text. If no stable text exists, --no-stable-expect is the honest fallback, not an unanchored run; do not use it when stable textual output exists.
  2. Locate, then probe. Read enough code to place the behavior. Pick the smallest CLI probe that exercises the reported symptom. In workspaces or monorepos, run from the package with --cwd <package-dir>, not with a cd ... && convention. If required environment changes matter, encode them inside --shell as one quoted command string such as 'VAR=... command'; inherited environment changes are not part of probe identity in v1.
  3. Demonstrate. Run the probe through scripts/repro_ledger.py run --project <root> --bug <slug> ... -- <command>. Read the failing output and confirm it fails for the reported reason: mechanically, expectMatched should be true when --expect was supplied; procedurally, inspect the tail/context instead of trusting an exit code.
  4. Diagnose against the probe. Test hypotheses with discriminating runs before stacking edits. If a better probe is needed, the new probe starts a new fail -> pass cycle and must be observed failing too.
  5. Fix.
  6. Verify with the identical probe identity. Re-run the same execution mode, argv vector or shell string, --cwd, and --timeout. Then run scripts/repro_ledger.py close --project <root> --bug <slug>.
  7. Promote when possible. If the target repo has a test suite, promote the probe into a committed regression test. This is encouraged, not a gate.
  8. Report. Cite the close JSON, cite the first repro entry's git evidence, name the strength rung from reference.md, and carry speculative when the ledger took an unreproduced path.

Read the full file on GitHub · 113 lines

Files

What ships with it

5 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. 9d ago First seen · 113 lines · 52 tokens per session scan A f2864103ae5d

Subscribe to this mod's changes

anchor-repro is a skill published in the GitHub repository lynxlangya/techne (105 stars, last pushed 2mo ago), licensed MIT. It adds 52 tokens to every session and 1,141 once invoked, about $0.0003 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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