What is debugging-playbook?

A symptom-based guide for finding bugs in the Cambridge Beer Festival app. It links visible problems to likely causes, small experiments, relevant tests, and established fix patterns.

Use it to debug data and state problems, reproduce controller issues with tests, investigate release crashes, and interpret the result of test or analysis commands.

It gives developers a focused way to investigate stale data, incorrect festival switching, cached state, cold-start changes, and Flutter web crashes without exploring the whole codebase blindly.

How richardthe3rd/cambridge-beer-festival-app configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to richardthe3rd/cambridge-beer-festival-app. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/richardthe3rd/cambridge-beer-festival-app/main/.claude/skills/debugging-playbook/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/richardthe3rd/cambridge-beer-festival-app

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook/github.svg)](https://agentmods.dev/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook)

Your own site

<a href="https://agentmods.dev/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook"><img src="https://agentmods.dev/badge/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook"><img src="https://agentmods.dev/badge/skills/richardthe3rd/cambridge-beer-festival-app/debugging-playbook.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 188 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 5,501 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00188	$0.05501
Opus 5.5	$0.00075	$0.02200
Sonnet 5.5	$0.00038	$0.01100
Haiku 4.5	$0.00019	$0.00550

Measured 2mo ago against content hash 471eb796ef70, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

debugging-playbook scanned grade A with 1 finding 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 2mo 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

| One drink category (e.g. cider) silently empty while others load | Per-type 404 soft-omission: a type returning HTTP 404 lands in NEITHER `drinksByType` NOR `failedTypes` — deliberate, so a transient mid-deploy 404 pre

.claude/skills/debugging-playbook/SKILL.md · 158 lines

How it starts

The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging Playbook

Symptom-first triage for this codebase. Every row below comes from a real incident (issue/PR cited); code locations verified against the working tree on 2026-07-02. Find your symptom, run the discriminating experiment, apply the fix-pattern. If your symptom isn't here, check skill failure-archaeology before deep-diving — most battles in this repo have already been fought once.

How to debug here (method)

Reproduce with the cheapest signal. Prefer a unit/widget test over the dev server; prefer the dev server over a release build. Domain controllers (lib/domain/controllers/) are pure and synchronous — most state bugs reproduce in a plain Dart test.
Run tests/analyze ONCE, then grep the log. ./bin/mise run test and ./bin/mise run analyze print TEST_LOG=/ANALYZE_LOG= paths (temp files) at the start of the run. Grep that file for different things instead of re-running the suite. See skill diagnostics-and-tooling for the full workflow, coverage inspection, and the source-map crash-decode scripts.
Isolate with a discriminating experiment (third column below): one cheap observation that splits the hypothesis space in half. Predict the result before running it.
Check history before deep-diving. Skill failure-archaeology chronicles every major investigation, rejected fix, and revert. Re-proposing a rejected fix (see Traps below) wastes a review cycle at best.
Fix through change control. Every behaviour change goes through ./bin/mise run check, a conventional commit, and PR + CI. See skill change-control. CI is ground truth: if analyzer and tests pass, a "this won't compile" review comment is wrong.

Doc-drift warning: AGENTS.md still lists FavoritesService/RatingsService/ TastingLogService as separate services. They no longer exist — personal state was unified into UserDataStore (lib/services/user_data_store.dart, #391/#395). lib/services/storage_service.dart now contains only FestivalStorageService. Trust the code.

Read the full file on GitHub · 158 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.

2mo ago First seen · 158 lines · 188 tokens per session scan A 471eb796ef70

Subscribe to this mod's changes

debugging-playbook is a skill published in the GitHub repository richardthe3rd/cambridge-beer-festival-app (3 stars, last pushed today), licensed MIT. It adds 188 tokens to every session and 5,501 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Debugging

debugging-playbook next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
debugging-playbookrichardthe3rd/cambridge-beer-festival-app	Skill	3	today	MIT	A	188	Claude Code
systematic-debuggingopen-metadata/OpenMetadata	Skill	16k	yesterday	Apache-2.0	A	37	Claude Code
log-error-digestzebbern/claude-code-guide	Skill	4.7k	3d ago	MIT	A	71	Claude Code, Codex
cwv-optimizeradobe/skills	Skill	319	yesterday	Apache-2.0	A	112	Claude Code
ci-fixersipyourdrink-ltd/bernstein	Skill	1.2k	yesterday	Apache-2.0	A	15	Claude Code, Codex
triaging-web-analytics-supportPostHog/posthog	Skill	41k	yesterday	none	A	151	Claude Code, Codex
diagnosing-missing-recordingsPostHog/posthog	Skill	41k	yesterday	none	A	76	Claude Code, Codex

cambridge-beer-festival-app: Skill for Claude Code