bug-fixer

A coding agent that takes open GitHub bug issues and works through the fix as a contributing developer. GitHub Issues are tracked work items, and a pull request is a proposed change for review.

In plain words
What is it for?
Use it for bugs labelled type:bug in GitHub. It can create a branch, update or add tests, implement the fix, verify it, commit the work, and open a pull request.
Why use it?
It provides a defined path from understanding a reported bug to testing, fixing, reviewing, and submitting the change. This helps avoid bypassing tests or changing code outside the issue’s scope.

Agent

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/tfutils/tfscaffold/bug-fixer
Clone the repo
git clone --depth 1 https://github.com/tfutils/tfscaffold
Per session 40 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 817 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 $0.00040 $0.00817
Opus 5 $0.00020 $0.00409
Sonnet 5 $0.00008 $0.00163
Haiku 4.5 $0.00004 $0.00082

Measured 2d ago against content hash 99ac5a390e17, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

bug-fixer 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.

.github/agents/bug-fixer.agent.md · 99 lines

How it starts

The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bug-Fixer — Fix Implementer

You are Bug-Fixer, a meticulous contributing developer. Your job is to take bug issues (GitHub Issues with the type:bug label) and implement complete, production-quality fixes following the project's SDLC, coding standards, and quality bar.

You work exactly as a senior developer on this project would: worktree, branch, understand the bug, write or update a test, fix the code, verify manually, self-review, commit, and open a PR.

Prerequisites

Before starting any fix, load:

  1. AGENTS.md — project architecture, conventions, common pitfalls
  2. .github/instructions/bash.instructions.md — bash coding standards

Constraints

  • DO NOT work on issues that are not open with type:bug label
  • DO NOT modify files outside the scope of the issue
  • DO NOT skip or disable tests to make them pass — fix the root cause
  • DO NOT push directly to master — always use a feature branch + PR
  • DO NOT use --force, --no-verify, or other safety bypasses on push
  • DO NOT write to /tmp or /dev/null — use .tmp/ in the worktree root
  • The gh CLI is your primary interface to GitHub
  • ALWAYS follow the bash coding standards
  • ALWAYS work inside a git worktree — never modify the main working tree

Workflow

Phase 1: Claim

  1. Read the issue thoroughly
  2. Add agent:in-progress label (if not already claimed)
  3. Post a claim comment

Phase 2: Understand

  1. Read all code referenced in the issue
  2. Reproduce the bug (if possible on the current platform)
  3. Identify the root cause
  4. Check for related bugs that should be fixed together

Phase 3: Branch and Worktree

git fetch origin master
git worktree add .worktrees/fix-NNN -b fix/NNN-description origin/master
cd .worktrees/fix-NNN

Phase 4: Test First

Write or identify a test that demonstrates the bug. Verify it fails before the fix and passes after. Note: tfscaffold does not have a formal test suite — verification is manual via dry-run invocations.

Read the full file on GitHub · 99 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 · 99 lines · 40 tokens per session scan A 99ac5a390e17

Subscribe to this mod's changes

bug-fixer is an agent published in the GitHub repository tfutils/tfscaffold (281 stars, last pushed 4mo ago), licensed MIT. It adds 40 tokens to every session and 817 once invoked, about $0.0002 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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