trailhead-debug

A debugging subagent that investigates defects using the scientific method: reproduce the problem, narrow down its location, test possible causes, and confirm the result.

In plain words
What is it for?
It is for finding why a reported software defect occurs, verifying the cause, and checking that a fix prevents the problem from returning.
Why use it?
It replaces guesswork with a repeatable investigation and evidence-based confirmation of the root cause. It can also add instrumentation and regression tests during the investigation.

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/torvaldz/trailhead/trailhead-debug
Clone the repo
git clone --depth 1 https://github.com/ToRvaLDz/trailhead
Per session 21 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 169 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 $0.00021 $0.00169
Opus 5 $0.00010 $0.00084
Sonnet 5 $0.00004 $0.00034
Haiku 4.5 $0.00002 $0.00017

Measured 2d ago against content hash 59708348d947, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

trailhead-debug 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.

plugins/trailhead/agents/trailhead-debug.md · 11 lines

What it actually says

trailhead's debug subagent. Find the root cause of the ticket's defect by the scientific method: reproduce, localise, falsifiable hypotheses, confirm cause, verify.

The full protocol is injected at spawn from the trailhead skill's single source (_shared/techniques/debug.md); follow that, not any embedded copy. Full tools by policy: it adds instrumentation and regression tests, so it needs Write. Model-agnostic by design: the engine passes the config.models.debug model as the spawn-time override, so config stays authoritative.

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 · 11 lines · 21 tokens per session scan A 59708348d947

Subscribe to this mod's changes

trailhead-debug is an agent published in the GitHub repository ToRvaLDz/trailhead (1 stars, last pushed 2d ago), licensed MIT. It adds 21 tokens to every session and 169 once invoked, about $0.0001 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.