fables

Use when designing, changing, or debugging backend server code (REST, Node.js/TypeScript, Go), especially endpoints, response envelopes, pagination, migrations, queries, auth, password hashing, secrets, or deploys; also for N+1 queries, races, IDOR, SSRF/injection, goroutine leaks, unhandled rejections, event-loop blocking, graceful shutdown, or production-only migration failures.

Use when designing, changing, or debugging backend server code (REST, Node.js/TypeScript, Go), especially endpoints, response envelopes, pagination, migrations, queries, auth, password hashing, secrets, or deploys; also for N+1 queries, races, IDOR, SSRF/injection, goroutine leaks, unhandled rejections, event-loop blocking, graceful shutdown, or production-only migration failures.

Use when a feature or refactor changes public contracts, schemas, shared integration points, cross-layer data flow, release behavior, or other high-risk architecture decisions.

Use when designing or debugging high-concurrency Go services, especially worker pools, backpressure, bounded channels, errgroup/WaitGroup, rate limits, load shedding, circuit breakers, GOMAXPROCS, or connection pools; also for load-time OOM, rising goroutines, lock contention, p99 spikes, retry storms, pprof, singleflight, semaphore, or production-only collapse.

Use when writing a git commit message, Japanese UI copy or app strings (ボタン/エラーメッセージ等の文言), code review comments, or a completion report, especially when tone, formality, verbosity, or review phrasing is uncertain.

Use when creating, regenerating, or auditing a repository-specific development harness, contract system, risk router, evidence gate, or project workflow policy.

Use when a feature or refactor changes public contracts, schemas, shared integration points, cross-layer data flow, release behavior, or other high-risk architecture decisions.

Use when designing or debugging high-concurrency Go services, especially worker pools, backpressure, bounded channels, errgroup/WaitGroup, rate limits, load shedding, circuit breakers, GOMAXPROCS, or connection pools; also for load-time OOM, rising goroutines, lock contention, p99 spikes, retry storms, pprof, singleflight, semaphore, or production-only collapse.

Use when writing a git commit message, Japanese UI copy or app strings (ボタン/エラーメッセージ等の文言), code review comments, or a completion report, especially when tone, formality, verbosity, or review phrasing is uncertain.

Use when creating, regenerating, or auditing a repository-specific development harness, contract system, risk router, evidence gate, or project workflow policy.

Use when building or polishing mobile app UI visuals (Flutter, SwiftUI, Jetpack Compose) — before choosing spacing, typography, color, corner radius, elevation, or motion duration; when a screen "looks off", feels cluttered, cheap, or inconsistent; when reviewing touch targets, contrast ratio, Dynamic Type, text overflow, or dark mode; also when hard-coded colors/paddings spread across widgets, or every new screen re-invents its own styling.

Use when building or polishing mobile app UI visuals (Flutter, SwiftUI, Jetpack Compose) — before choosing spacing, typography, color, corner radius, elevation, or motion duration; when a screen "looks off", feels cluttered, cheap, or inconsistent; when reviewing touch targets, contrast ratio, Dynamic Type, text overflow, or dark mode; also when hard-coded colors/paddings spread across widgets, or every new screen re-invents its own styling.

Use when creating a new custom agent/subagent definition (.claude/agents/*.md), auditing or rewriting existing agent definitions, deciding whether a task deserves a dedicated agent vs general-purpose with a good prompt, choosing an agent's tools whitelist or model tier, or when delegated agents keep going off-scope, dumping full transcripts back, or overlapping each other's roles.

Use when writing, refactoring, or debugging Android app code (Kotlin, Jetpack Compose, Gradle, ProGuard/R8) — before adding a feature, touching build config or proguard-rules, preparing a release/AAB, or when facing release-only crashes, ClassNotFoundException after minify, lifecycle leaks, ANR, or excessive recomposition.

Use when about to spawn or delegate work to a subagent (Agent/Task tool), choosing a model tier (haiku/sonnet/opus) for a task, writing a delegation prompt, deciding whether something should be delegated at all, verifying a delegated result, or after a delegated task failed twice and needs escalation.

Use when creating a new custom agent/subagent definition (.claude/agents/*.md), auditing or rewriting existing agent definitions, deciding whether a task deserves a dedicated agent vs general-purpose with a good prompt, choosing an agent's tools whitelist or model tier, or when delegated agents keep going off-scope, dumping full transcripts back, or overlapping each other's roles.

Use when writing, refactoring, or debugging Android app code (Kotlin, Jetpack Compose, Gradle, ProGuard/R8) — before adding a feature, touching build config or proguard-rules, preparing a release/AAB, or when facing release-only crashes, ClassNotFoundException after minify, lifecycle leaks, ANR, or excessive recomposition.

Use when about to spawn or delegate work to a subagent (Agent/Task tool), choosing a model tier (haiku/sonnet/opus) for a task, writing a delegation prompt, deciding whether something should be delegated at all, verifying a delegated result, or after a delegated task failed twice and needs escalation.

Use when writing, refactoring, or debugging Flutter/Dart app code (widgets, Riverpod, Bloc, setState, platform channel, pubspec) — before adding a screen, choosing state management, measuring performance, adding a plugin, or preparing a release build. Also when facing jank/dropped frames, rebuild storms, release mode crash (tree shaking / AOT-only), MissingPluginException, or "works in debug but crashes in release".

Use when writing, refactoring, or debugging React/Next.js frontend code (App Router, Server/Client Components, hooks, Tailwind/CSS Modules) — before adding a component, choosing where state lives, wiring data fetching, or preparing a production deploy; or when facing hydration mismatch, NEXT_PUBLIC_ env leaks, excessive re-render, bundle size bloat, CLS, SEO/metadata gaps, or XSS via dangerouslySetInnerHTML.

Use when writing, refactoring, or debugging iOS app code (Swift, SwiftUI, Swift Concurrency, Xcode) — before adding a feature, choosing state ownership (@State / @Observable / @Environment), touching MainActor/actor/Sendable, preparing a TestFlight/App Store build, or when facing App Store review rejection, provisioning profile errors, missing dSYM / unsymbolicated crashes, data races, or continuation misuse.

Use when building or debugging RAG / semantic search / retrieval systems — before choosing a vector store (pgvector, Qdrant, Milvus, Elasticsearch), designing chunking, embedding models, hybrid search (BM25 + vector), HNSW indexing, or a reranker; or when facing bad recall, "retrieved the wrong docs", LLM answers wrong despite good docs, stale index, post-filter emptying top-k, metadata filtering, or planning a semantic similarity / retrieval evaluation with recall@k / MRR / nDCG.

Use when working in a technical domain with no existing playbook, writing new coding guidelines / review criteria / checklists from scratch, judging whether a verification method actually proves a claim (test passed but does it count?), or when repeated fixes keep failing and the direction feels wrong. Domain-agnostic reasoning moves that generate concrete decision criteria for any field — not tied to any language or framework.

Use when writing, refactoring, or debugging Flutter/Dart app code (widgets, Riverpod, Bloc, setState, platform channel, pubspec) — before adding a screen, choosing state management, measuring performance, adding a plugin, or preparing a release build. Also when facing jank/dropped frames, rebuild storms, release mode crash (tree shaking / AOT-only), MissingPluginException, or "works in debug but crashes in release".

Use when writing, refactoring, or debugging React/Next.js frontend code (App Router, Server/Client Components, hooks, Tailwind/CSS Modules) — before adding a component, choosing where state lives, wiring data fetching, or preparing a production deploy; or when facing hydration mismatch, NEXT_PUBLIC_ env leaks, excessive re-render, bundle size bloat, CLS, SEO/metadata gaps, or XSS via dangerouslySetInnerHTML.

Use when writing, refactoring, or debugging iOS app code (Swift, SwiftUI, Swift Concurrency, Xcode) — before adding a feature, choosing state ownership (@State / @Observable / @Environment), touching MainActor/actor/Sendable, preparing a TestFlight/App Store build, or when facing App Store review rejection, provisioning profile errors, missing dSYM / unsymbolicated crashes, data races, or continuation misuse.

Use when building or debugging RAG / semantic search / retrieval systems — before choosing a vector store (pgvector, Qdrant, Milvus, Elasticsearch), designing chunking, embedding models, hybrid search (BM25 + vector), HNSW indexing, or a reranker; or when facing bad recall, "retrieved the wrong docs", LLM answers wrong despite good docs, stale index, post-filter emptying top-k, metadata filtering, or planning a semantic similarity / retrieval evaluation with recall@k / MRR / nDCG.

Use when working in a technical domain with no existing playbook, writing new coding guidelines / review criteria / checklists from scratch, judging whether a verification method actually proves a claim (test passed but does it count?), or when repeated fixes keep failing and the direction feels wrong. Domain-agnostic reasoning moves that generate concrete decision criteria for any field — not tied to any language or framework.