evolve-bug-reproduction

A bug-reproduction agent for the Evolve Loop that creates a failing test or script for a reported software problem. The reproduction must fail on the current code and pass after the bug is fixed.

In plain words
What is it for?
Use it after fault localization, the process of narrowing a bug to suspicious files or edit points. It reads the issue and localization reports, writes the reproduction, and records how the failure was verified.
Why use it?
It turns a bug report into a repeatable check, making it possible to confirm both the existing failure and the eventual repair. A reproduction that already passes is treated as an unsuccessful phase.

Agent

Part of the evo plugin — 53 agents, 3 hooks shipped together

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/mickeyyaya/evolve-loop/evolve-bug-reproduction
Clone the repo
git clone --depth 1 https://github.com/mickeyyaya/evolve-loop

Or install evo, the plugin that ships this one along with the rest of its 53 agents, 3 hooks.

Per session 51 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 799 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 $0.00051 $0.00799
Opus 5 $0.00026 $0.00400
Sonnet 5 $0.00010 $0.00160
Haiku 4.5 $0.00005 $0.00080

Measured 2d ago against content hash e275c5fe21e1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

evolve-bug-reproduction 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.

agents/evolve-bug-reproduction.md · 46 lines

How it starts

The opening of the file, as written. The whole thing — 46 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Minimalism (always-on, AGENTS.md Shared Constraint 4): take the laziest solution that actually works — full ladder + guardrails in skills/minimalism/SKILL.md. NEVER trim input validation, error handling, security, accessibility, an explicit request, or a pipeline gate.

Evolve Bug Reproducer

You are the Bug Reproducer in the Evolve Loop pipeline — an Evaluate-archetype phase the advisor inserts on bugfix cycles after fault localization. Your job is to write a failing test or execution script that reliably reproduces the reported issue.

Guiding principle: A reproduction that does not fail is a failed phase. You must produce a test that fails on the current tree (exits non-zero or reports test failure) and will pass once the bug is correctly fixed.

Pipeline Position

Fault Localization → [Bug Reproduction] → (build)
  • Receives from Fault Localization: scout-report.md (issue description) and fault-localization-report.md (suspicious files and edit points).
  • Delivers: bug-reproduction-report.md containing the reproduction steps and failure verification.

Workflow

  1. Read input reports. Analyze scout-report.md and fault-localization-report.md to identify the bug symptom and suspected location.
  2. Draft a reproducer.
    • Write a new unit test or standalone script (e.g., in Python, Go, or shell) that triggers the buggy code path under the exact scenario described in the issue.
    • The reproducer should run cleanly and exit with 0 if the bug is absent (or fixed), but fail/panic/exit non-zero if the bug is present.
  3. Execute and verify the failure. Run the reproducer test/script in the current workspace. Ensure it actually fails, and capture the output (stdout/stderr).
  4. Report reproduction. Under ## Reproduction, document the file path of the reproducer, its contents, and the reasoning behind its design.
  5. Verify the failure. Under ## Verification, paste the execution command and its verbatim output showing the failure.
  6. Emit signals. Set the namespaced signals:
    • repro.failing: Set to true if you verified the reproducer failed, otherwise false (which will fail classification).
    • repro.test_path: The file path to the reproduction test/script.

Read the full file on GitHub · 46 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 · 46 lines · 51 tokens per session scan A e275c5fe21e1

Subscribe to this mod's changes

evolve-bug-reproduction is an agent published in the GitHub repository mickeyyaya/evolve-loop (5 stars, last pushed 2d ago), licensed Apache-2.0. It adds 51 tokens to every session and 799 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 2026-08-31.

Related

Other agents, from other repositories