# error-handling-typed-results > Claude/Codex skill by [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars · Updated 2026-09-23 Enforces a typed-error spine — a hand-rolled sealed Result\ plus one per-boundary sealed Failure carrying a stable code and typed params (never a localized string), returned instead of thrown; recoverable failures are values, only bugs throw. Convert-at-boundary catches narrowly with an on-clause and logs the original error+stack BEFORE returning a typed Failure; call sites switch exhaustively with no default:; the taxonomy of what the global error net (FlutterError.onError + PlatformDispatcher.onError, installed by app-startup-and-bootstrap) routes into, plus Isolate.run re-wrapping; mechanism selection (Error vs assert vs Exception vs sealed outcome) and @useResult; and a never-lose-data layer (one-transaction-per-mutation, debounced autosave drafts, optimistic soft-delete/Undo). Use when writing result.dart/failures.dart, a try/catch or sealed-switch default:, wiring bootstrap handlers, a repository/service/DAO boundary, or transactions, drafts, or soft-delete/Undo. Tags: agent-skills, ai-agents, best-practices, claude-code, codex, coding-agent, cursor, dart, dartlang, developer-tools, drift, flutter, flutter-architecture, github-copilot, go-router, llm, material-design, mvvm, riverpod, skills ## Install ```sh git clone https://github.com/zakariaf/Flutter-Skills /tmp/Flutter-Skills && ln -s /tmp/Flutter-Skills/skills/error-handling-typed-results ~/.claude/skills/error-handling-typed-results ``` ## From README Error Handling — Typed Results Recoverable failures are typed values that flow through the layers and are switched on exhaustively; only genuine bugs and unrecoverable states throw, and those are caught once by a global net. Wrapped around both, never-lose-data — transactions, autosave drafts, soft-delete/Undo — is a first-class subsystem, not plumbing. Two tiers, no middle ground. Read the reference for the task at hand: references/result-failure-spine.md — the Result/Failure source, the per-boundary taxonomy, convert-at-boundary, the global net, isolate re-wrapping, and local logging. references/mechanism-selection.md — throw vs assert vs Exception vs sealed outcome, @useResult, and the runZonedGuarded decision. references/never-lose-data.md — one transaction per mutation, debounced autosave drafts, optimistic soft-delete / Trash / Undo behind one filter. Run scripts/check-swallowed-catch.sh and scripts/check-softdelete-parity.sh before a PR. ## Links - HTML page: https://omgskills.com/library/zakariaf/flutter-skills/skills/error-handling-typed-results/ - GitHub: https://github.com/zakariaf/Flutter-Skills - Author: [@zakariaf](https://omgskills.com/library/zakariaf/index.md) ## More from this repo - [accessibility-as-code](https://omgskills.com/library/zakariaf/flutter-skills/skills/accessibility-as-code/index.md) — Enforces accessibility as a correctness property authored into each widget — Semantics(button/label) or... - [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars - [adaptive-layout](https://omgskills.com/library/zakariaf/flutter-skills/skills/adaptive-layout/index.md) — Enforces adapting layout by available CONSTRAINTS/size, never device or platform checks — LayoutBuilder +... - [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars - [ads-and-iap-monetization](https://omgskills.com/library/zakariaf/flutter-skills/skills/ads-and-iap-monetization/index.md) — Enforces opt-in, rewarded-first monetization over the service seam — a rewarded view grants exactly one benefit and... - [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars