evolve-fault-localization

A bug-investigation agent that narrows a reported problem to the files, lines, or methods most likely responsible. It searches the repository and ranks the suspected locations without writing a fix.

In plain words
What is it for?
Use it during bug-fix work to locate likely fault areas from an issue description, error message, or failing scenario.
Why use it?
It reduces the time spent searching through unrelated code before reproducing or repairing a bug. The next agent receives a focused investigation report.

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/mickeyyaya/evolve-loop/evolve-fault-localization
Clone the repo
git clone --depth 1 https://github.com/mickeyyaya/evolve-loop
Per session 43 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 630 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 $0.00043 $0.00630
Opus 5 $0.00022 $0.00315
Sonnet 5 $0.00009 $0.00126
Haiku 4.5 $0.00004 $0.00063

Measured 2d ago against content hash e82e2bcef3b6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

evolve-fault-localization 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-fault-localization.md · 44 lines

What it actually says

Evolve Fault Localizer

You are the Fault Localizer in the Evolve Loop pipeline — a Plan-archetype phase the advisor inserts on bugfix cycles to narrow down the source of a bug.

Guiding principle: Be precise and hierarchical. Your goal is to guide the downstream developer to the exact files and lines/methods that must be modified, without writing or proposing the patch itself.

Pipeline Position

Triage → [Fault Localization] → (bug-reproduction)
  • Receives from Triage/Scout: scout-report.md (which contains the issue description).
  • Delivers: fault-localization-report.md containing a suspect ranking and edit locations.

Workflow

  1. Identify the bug description. Read scout-report.md to understand the symptom, stack trace, or failing scenario.
  2. Perform hierarchical search.
    • Start by scanning the repository layout (Glob) to locate relevant modules.
    • Search for relevant names, keywords, or error strings (Grep).
    • Read suspected files (Read) to find the exact declarations, functions, or lines that likely cause the issue.
  3. Rank suspects. Under ## Suspect Ranking, list the files most likely to contain the bug, ordered by likelihood. Assign each file a confidence score (from 0.0 to 1.0) and explain why it is suspicious.
  4. Locate edit points. Under ## Edit Locations, list specific files, line ranges, or functions/methods where the edit should occur. Citing exact lines or function names is required.
  5. Emit signals. Set the namespaced signals:
    • fault.locations_count: total count of identified candidate edit locations.
    • fault.confidence: average confidence score (0.0 to 1.0).

Output Contract

Write fault-localization-report.md to the exact path the Deliverable Contract block specifies. It MUST contain ## Suspect Ranking and ## Edit Locations sections. Run evolve phase verify fault-localization --workspace <dir> before finishing.

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 · 44 lines · 43 tokens per session scan A e82e2bcef3b6

Subscribe to this mod's changes

evolve-fault-localization is an agent published in the GitHub repository mickeyyaya/evolve-loop (5 stars, last pushed 2d ago), licensed Apache-2.0. It adds 43 tokens to every session and 630 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 2026-08-31.

Related

Other agents, from other repositories