error-handling-audit

name	error-handling-audit
description	Audit a TypeScript codebase's error-handling discipline against an opinionated baseline spanning throw and catch hygiene, async and network error handling, React error boundaries, and logging and observability. Static-only by design. Optionally generates an implementation plan for the gaps.
trigger	/error-handling-audit

/error-handling-audit

Audit a TypeScript codebase's error-handling discipline against an opinionated baseline organised in four layers — throw and catch hygiene, async and network error handling, React error boundaries, logging and observability — preceded by a diagnostic snapshot. Then offer to generate an implementation plan for the gaps.

The default mental model is TypeScript and React. Layers 1, 2, and 4 apply to any TypeScript codebase; layer 3 is React-specific and is silently skipped when React is not detected.

Posture: static-only, no opt-in modes

Unlike /bundle-build-audit (--with-stats) and /dependency-audit (--with-network), this skill has no opt-in enrichment mode. Error handling is a pure code-shape audit and there is no external data source that improves it.

The actual errors happening in production belong to observability, not to an architectural audit. They are the responsibility of the user's existing error-reporting tool (Sentry, Datadog, Bugsnag, etc.) or a separate skill. This audit reads code; it never queries any reporting service, and it never executes the codebase.

Usage

/error-handling-audit                             # default: concise Top 5 + full report saved + ask about plan
/error-handling-audit --worktree                          # create an isolated Git worktree, then run the audit there
/error-handling-audit --learn                     # mid-level engineer teaching mode (detailed explanations + file/line examples)
/error-handling-audit --teach                     # alias for --learn

💡 Pro tip: Add --worktree to run this audit in an isolated Git worktree.

The skill never accepts --apply. The implementation plan is descriptive Markdown.

This audit deliberately has no numeric threshold flags. Most checks are zero-tolerance (an empty catch is an empty catch); the rest report partial based on qualitative pattern detection. The canonical path to evolving the baseline itself is /system-self-improve.

The opinionated baseline

A check resolves to one of four statuses:

• present — the invariant holds.
• partial — most signals resolve, with a small number of exceptions, or the check is qualitative and the codebase shows mixed adherence.
• missing — a structural prerequisite is absent (no error-reporting service installed, for example).
• violation — the audit identified concrete code that breaks the invariant.

Layer 0 is informational only and has no status. Layer 3 reports skipped: "react-not-detected" (and no per-check entries) when React is absent.

Layer 0 — Diagnostic snapshot (always written, no pass/fail)

• Total try/catch block count and the average per source file.
• Total throw statement count.
• Asynchronous style breakdown: async/await count vs raw .then()/.catch() chain count.
• Detected error-reporting service (Sentry, Bugsnag, Rollbar, Datadog RUM, Honeybadger, Highlight, custom — or none).
• Detected logger (console, pino, winston, loglevel, framework-provided, custom — or none beyond console).
• Error-boundary component count and placement breakdown (root, route-level, feature-level, leaf — when React is detected).
• Top 10 distinct error types thrown by the project (Error, TypeError, SyntaxError, custom subclasses), with occurrence counts.

Layer 1 — Throw and catch hygiene

Check	Expectation	Violation signal
No empty catch blocks	No catch (e) {} or catch {} with an empty body.	Any empty catch. Reported with file and line.
No silently swallowed errors	Every catch either logs/reports the error, returns a typed result (Result/Either pattern), or rethrows with context.	A catch that does none of the three. Reported with file and line.
No string or non-Error throws	Every throw throws an Error or subclass.	throw "message", throw 42, throw { code: 'X' }. Reported with file and line.
TypeScript catch typing	useUnknownInCatchVariables is enabled in tsconfig.json, OR every catch parameter in source is annotated : unknown.	The compiler option is off and untyped or any-typed catch parameters appear in source.
Error chaining preserves cause	When rethrowing or wrapping, the original is attached via the cause option (new WrappedError(message, { cause: e })).	A catch whose body throws a fresh error without referencing the original.
Domain errors use custom classes	At least one custom error class hierarchy exists for domain errors. Soft check — reported as partial if absent.	All thrown errors are bare Error.

Layer 2 — Async and network error handling

Check	Expectation	Violation signal
Network calls have error paths	Every fetch / axios / data-layer call site is inside a try/catch (when awaited) or has .catch (when chained), OR is in a function whose return type explicitly propagates the failure (TanStack Query function, Server Action, etc.).	Awaited fetch/axios with no surrounding error handling and no upward propagation.
Network calls have timeout configuration	Each network primitive uses AbortSignal.timeout(), a signal from a query layer, or an explicit timeout option.	Network calls without any timeout.
Retry logic for retriable failures	Retry behaviour is centralised in the data layer with explicit retriable conditions (5xx responses, 429, network errors), not duplicated per call site. Soft check.	Mixed: some call sites retry inline, others don't; or no retry strategy at all in an application that depends on network reliability.
Status-code branching is explicit	Network responses distinguish 4xx (client) from 5xx (server) and from network errors. Single-string error messages don't conflate them.	if (!response.ok) throw new Error('Request failed') with no status discrimination.
Top-level async errors captured	Async functions invoked from non-await contexts (useEffect, setTimeout, addEventListener, event handlers, promise constructors) capture rejections explicitly.	An async arrow passed as an event handler with no internal try/catch; an awaited call inside useEffect with no error path.
AbortController for cancellable requests	Components that issue requests and may unmount while a request is pending use AbortController (or the data layer's signal) to cancel on unmount.	Bare fetch inside useEffect with no cleanup.

Layer 3 — React error boundaries (skipped silently when React not detected)

Check	Expectation	Violation signal
Root error boundary present	At least one error boundary wraps the application root.	No root boundary detected.
Route- or feature-level boundaries	Boundaries exist at route level (or feature-cluster level for a large application), not only at the root.	Only a single root boundary present in an application with multiple routes or features.
Fallback UI offers recovery	Boundary fallback components include at least one recovery affordance: retry, reload, navigate home.	Fallback that only renders an error message with no action.
Boundary forwards to reporting service	The boundary's componentDidCatch (or react-error-boundary's onError) calls the detected error-reporting service.	Boundary that only renders the fallback without reporting.
Suspense paired with error boundary	Every <Suspense> that wraps async-loaded data has an error boundary as an ancestor.	A <Suspense> with no error boundary upstream.
No try/catch around JSX render	Render functions and components don't wrap return values in try/catch (it does not catch render errors anyway — that is the boundary's job).	A try/catch whose try block is a return <Foo />.
Mutation errors handled at call site	TanStack Query mutations, RTK Query mutations, and equivalents have explicit onError handlers, OR the consuming component handles isError.	Mutations with no error handling and no consuming isError branch.

Layer 4 — Logging and observability

Check	Expectation	Violation signal
Error-reporting service integrated	A recognised error-reporting service is installed as a dependency.	None detected.
Reporting initialised at entry point	Initialisation happens before any application code runs (in main.tsx, app/layout.tsx, pages/_app.tsx, or the framework equivalent).	Service installed but not initialised in the entry point.
Release versioning attached	Reporting client is configured with a release identifier (git SHA, npm version, deploy ID).	No release configuration.
Source maps uploaded	A continuous-integration step uploads source maps to the reporting service after a successful build.	No upload step detected in any workflow file.
Production sample rate configured	The reporting client has an explicit tracesSampleRate (or equivalent) in production — not the SDK default.	Default sample rate in production.
No console.log in production code paths	console.log, console.debug, console.warn are absent from production code (allowed in tests, build scripts, dev-only files, and when guarded by process.env.NODE_ENV !== 'production'). console.error is acceptable when also reporting to the error service.	Unguarded console.* calls in source under src/ (or the framework equivalent).
Structured logging	Logger calls pass a context object alongside the message, not a single string-concatenated argument. Soft check — reported as partial when adherence is mixed.	Logger calls that only pass a string.
Sensitive-data redaction configured	The reporting client has a beforeSend (or equivalent) configured to scrub passwords, tokens, and PII keys, OR a documented allowlist of safe fields.	No beforeSend or redaction configured.
Single log per error	An error that is caught, logged, and rethrown is not logged again at every layer above. Soft check.	Patterns where the same error path logs at multiple layers.

What this skill does

1. Reads the knowledge graph when present. Soft dependency: when graphify-out/graph.json exists, the audit uses the graph to trace which functions throw and how errors propagate, sharpening the top-level async-capture check. The audit still runs in full when the graph is absent.

2. Confirms a TypeScript project. Detects package.json, tsconfig.json, and a TypeScript dependency. If absent, the skill stops and tells the user it currently supports TypeScript projects only.

3. Detects React. Layer 3 is enabled only when react is in dependencies (directly or via a meta-framework that brings it in). When absent, layer 3 is recorded as skipped in findings.json and omitted from the chat summary.

4. Detects the error-reporting service and the logger for the diagnostic snapshot and for the layer 4 checks.

5. Writes Layer 0 — the diagnostic snapshot to .architect-audits/error-handling-audit/snapshot.md and prepends the same content to findings.md.

6. Walks each check in the active layer list, applying any --include and --exclude filters. Records a status, evidence, and (where relevant) sample file references per check.

7. Writes phase 1 outputs to .architect-audits/error-handling-audit/:

   • findings.md — diagnostic snapshot followed by check results, grouped by layer.
   • findings.json — machine-readable.
   • snapshot.md — diagnostic snapshot on its own.
   • metadata.json — skill version, run timestamp, Graphify revision (when present), framework variant, detected reporting service, detected logger, applied filters, layer 3 skipped status when applicable.

8. Phase 2 — offers to plan the gaps. Summarises the findings in chat and asks the user a single yes-or-no question:

   "Generate an implementation plan for the error-handling gaps? (yes/no)"

   On yes, writes .architect-audits/error-handling-audit/implementation-plan.md describing exactly which catch blocks to fix, which network call sites to wrap, which React error boundaries to add, and which observability primitives to wire up — ordered by layer and then by severity. The plan does not modify any project files.

   On no, exits cleanly.

Implementation steps

Step 1 — Confirm the prerequisites

test -f package.json || { echo "error-handling-audit: no package.json detected. This skill currently supports TypeScript projects only."; exit 1; }
test -f tsconfig.json || { echo "error-handling-audit: no tsconfig.json detected. This skill currently supports TypeScript projects only."; exit 1; }

Step 2 — Detect framework and observability stack

Read package.json. Resolve:

• React presence: react in dependencies (directly or via Next.js, Remix, etc.). Determines whether layer 3 runs.
• Framework variant: Next.js (App Router or Pages Router), Remix, Vite-React, Create React App, plain React, plain TypeScript. Influences entry-point detection in layer 4.
• Error-reporting service: scan dependencies for known packages — @sentry/*, @bugsnag/*, rollbar, @datadog/browser-rum, @honeybadger-io/js, @highlight-run/*. Record the first match, or none.
• Logger: scan for pino, winston, loglevel, framework-provided. When none of these is in dependencies, record console as the implicit logger.

Step 3 — Build the diagnostic snapshot

Compute the items listed in Layer 0 by reading source files. Use Graphify's communities to sample broadly when present; otherwise sweep all .ts/.tsx files under src/ (or the framework equivalent). Write snapshot.md and prepend the same content to findings.md.

Step 4 — Resolve each check

For each check in the active layer list, walk its detection logic:

• All required signals indicate the invariant holds → present.
• Most signals hold; a small number of exceptions → partial. For checks marked "soft", mixed adherence is the typical partial case.
• The structural prerequisite is absent → missing (e.g., layer 4 "error-reporting service integrated" when no service is installed).
• Concrete violators exist → violation. Always include sample file references.

For checks that can produce many offenders (empty catches, swallowed errors, unguarded console.*), record up to ten representative samples plus a total count rather than the exhaustive list.

Step 5 — Write phase 1 outputs

Create .architect-audits/error-handling-audit/ if needed. Write findings.md, findings.json, snapshot.md, metadata.json. Overwrite previous runs of these four; preserve implementation-plan.md unless the user agrees to regenerate it.

Step 6 — Print the concise chat summary and offer phase 2

Print a human-first, scannable summary in the chat. Do not print the full layered findings — those are written to disk in Step 5. The chat output has exactly this shape:

1. Short header — audit name, timestamp, and a one-line summary of the codebase state.
2. Top 5 Highest-Leverage Recommendations — ordered by architectural principles: test philosophy, maintainability, risk reduction, velocity, long-term health. For fewer than five findings, print what exists. For each recommendation (numbered 1–5):
   • Title (one clear line).
   • Why it matters (explain the principle in 1–2 sentences).
   • Real consequences if ignored (honest downside for the team or project).
   • Smallest high-leverage fix (exact next step, effort level, and which files to touch).
   • At the end, add a lettered sub-list of concrete actions if useful (e.g. 2a, 2b) so the user can reply with "2b" or "1 and 3" to trigger implementation.
3. Bottom line: Full detailed audit report (layered findings, snapshot, metadata, implementation plan) → .architect-audits/error-handling-audit/findings.md

When --learn or --teach is set, expand each recommendation into mid-level engineer teaching mode:

• For every item, explain as if teaching a mid-level engineer, pointing to specific files and line numbers from the current codebase.
• Use educational language: "Here's why this pattern bites teams in the long run…", "This is the exact mistake I see in most codebases at your stage…", "The fix is small but pays off huge because…".
• Include a short "What you'll learn from fixing this" section for each recommendation.
• Keep the numbered/lettered structure so the user can still reply with "2b" or "1 and 3".
• End with the same bottom-line link to the full report.

After printing, ask the single yes-or-no question: "Generate an implementation plan for the gaps identified above? (yes/no)" Do not proceed to phase 2 without an explicit affirmative.

Step 7 — Phase 2: generate the implementation plan

When the user agrees, build implementation-plan.md:

1. Header — repository name, baseline version, framework variant, detected reporting service, timestamp, total counts per layer.
2. Layer 1 — throw and catch hygiene plan: per finding, the file and line, the offending pattern, and the recommended replacement (typed result, rethrow with cause, custom error class).
3. Layer 2 — async and network plan: per finding, the call site, the wrapping pattern (try/catch with timeout, AbortController for components, query-layer extraction). Centralisation suggestions for retry strategy when scattered patterns are detected.
4. Layer 3 — React error boundaries plan (when React detected): boundary placement recommendations driven by route/feature structure (informed by Graphify communities when present), fallback-UI snippets with recovery affordances, reporting wiring snippet.
5. Layer 4 — logging and observability plan: installation snippet for the recommended reporting service when absent, initialisation snippet for the framework variant, source-map upload step for the continuous-integration workflow, sample-rate and beforeSend configuration, console-log replacements.
6. Closing checklist — flat checkbox list mirroring the gaps, suitable for pasting into a pull-request description.

The plan is descriptive, not executable. It does not edit source files and it does not install packages.

Findings file shape

findings.json:

{
  "skillVersion": "1.0.0",
  "runStartedAt": "2026-04-26T13:47:00Z",
  "runFinishedAt": "2026-04-26T13:47:13Z",
  "framework": "next-app-router",
  "reactDetected": true,
  "reportingService": "sentry",
  "logger": "console",
  "snapshot": {
    "tryCatchCount": 142,
    "tryCatchPerFileMean": 1.8,
    "throwCount": 67,
    "asyncStyle": { "asyncAwait": 318, "thenChain": 42 },
    "errorBoundaryCount": 3,
    "errorBoundaryPlacement": { "root": 1, "route": 2, "feature": 0, "leaf": 0 },
    "topErrorTypes": [
      { "type": "Error", "count": 51 },
      { "type": "ApiError", "count": 14 }
    ]
  },
  "summary": {
    "throwAndCatchHygiene":     { "present": 4, "partial": 1, "missing": 0, "violation": 1 },
    "asyncAndNetwork":          { "present": 2, "partial": 2, "missing": 0, "violation": 2 },
    "reactErrorBoundaries":     { "present": 3, "partial": 1, "missing": 1, "violation": 2 },
    "loggingAndObservability":  { "present": 5, "partial": 1, "missing": 1, "violation": 2 }
  },
  "checks": [
    {
      "layer": "throw-and-catch-hygiene",
      "check": "no-empty-catch-blocks",
      "status": "violation",
      "evidence": [],
      "samples": [
        { "path": "src/features/inbox/syncMessages.ts", "line": 87 },
        { "path": "src/lib/storage.ts", "line": 23 }
      ],
      "totalCount": 4,
      "expectation": "No catch (e) {} or catch {} with an empty body.",
      "gap": "4 empty catch blocks detected.",
      "remediation": "Either log the error to the reporting service, return a typed Result, or rethrow with cause attached. Empty catches lose information that is impossible to reconstruct later."
    }
  ]
}

When React is not detected, reactErrorBoundaries summary becomes "reactErrorBoundaries": { "skipped": "react-not-detected" } and the corresponding entries do not appear in the checks array.

findings.md mirrors the same content in human-readable form, with the diagnostic snapshot at the top and one section per check, grouped by layer. snapshot.md contains only the snapshot. metadata.json carries skill identity, timestamps, Graphify revision (when present), the framework, the detected reporting service and logger, the React-detected flag, and the configuration of the run.

Idempotency rules

• Re-running with no flags overwrites findings.md, findings.json, snapshot.md, and metadata.json in place.
• implementation-plan.md is preserved across runs unless the user agrees to regenerate it.
• Filter flags are recorded in metadata.json so a partial run can be reproduced.

Failure modes and remediation

Symptom	Cause	Fix
no package.json detected	The skill is run outside a Node.js project root.	Change directory into the project root and re-run.
no tsconfig.json detected	JavaScript-only project.	Stop. Inform the user that the skill currently supports TypeScript projects only.
Knowledge graph missing	/pre-audit-setup has not been run.	Continue. Record noGraphify: true in metadata.json. The async-capture and propagation analysis falls back to broader sweeps with reduced precision.
React detected but no entry point found	Custom application bootstrap that the skill cannot recognise.	Continue layer 3 with the boundary-placement checks; record the framework as react-custom and skip the entry-point-specific layer 4 check.
Multiple error-reporting services detected	Migration in progress or accidental dual-install.	Record both in the snapshot; treat both for the layer 4 checks (each must be initialised, configured, etc.). Surface the dual-install as a partial finding on a synthetic check "single-reporting-service".
useUnknownInCatchVariables is true but catches still use any annotations	The compiler option does not retroactively change explicit annotations.	The TypeScript-catch-typing check still reports violation for explicit any annotations, with a remediation note explaining the option-vs-annotation distinction.

What this skill explicitly does NOT do

• Execute any code, run any test, or query any error-reporting service.
• Read production error data. Runtime error frequency and impact are out of scope; that belongs to the user's existing observability tooling.
• Install any package or dependency.
• Create, modify, or delete any file outside .architect-audits/error-handling-audit/.
• Modify source files, configuration, or continuous-integration workflows.
• Open pull requests or commit anything to git.
• Audit JavaScript-only projects.
• Replace error-handling code review by a human. The audit catches structural issues; nuanced "is this the right level to handle this error" decisions remain a human judgment.
• Encode an opinion about Result/Either patterns vs idiomatic throw/catch. Both are accepted as valid responses to the swallowed-errors check.