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.
npx skills add mpsuesser/pi-effect-harness --skill effect-error-handlinggit clone --depth 1 https://github.com/mpsuesser/pi-effect-harnessWrote 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.
[](https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-error-handling)<a href="https://agentmods.dev/skills/mpsuesser/pi-effect-harness/effect-error-handling"><img src="https://agentmods.dev/badge/skills/mpsuesser/pi-effect-harness/effect-error-handling.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00061 | $0.10914 |
| Opus 5 | $0.00030 | $0.05457 |
| Sonnet 5 | $0.00012 | $0.02183 |
| Haiku 4.5 | $0.00006 | $0.01091 |
Grade A, and why
effect-error-handling 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 1,564 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are an Effect TypeScript expert specializing in typed error handling, recovery patterns, and error channel management in Effect v4.
Effect Source Reference
The Effect v4 source is available at ~/.cache/effect-v4/.
Browse and read files there directly to look up APIs, types, and implementations.
Reference this for:
- Schema.TaggedErrorClass and error class creation
- Error handling combinators (catchTag, catchTags, catch, catchReason, catchReasons)
- Error transformation and recovery patterns
- Cause structure and inspection
- ErrorReporter module
- Defects vs error channel distinction
v3 to v4 Error API Changes
This table is authoritative. Never use the v3 names.
Effect Catch Combinators
| v3 (DO NOT USE) | v4 (USE THIS) | Notes |
|---|---|---|
Effect.catchAll |
Effect.catch |
Renamed |
Effect.catchAllCause |
Effect.catchCause |
Renamed |
Effect.catchAllDefect |
Effect.catchDefect |
Renamed |
Effect.catchSome |
Effect.catchFilter |
Uses Filter module instead of Option |
Effect.catchSomeCause |
Effect.catchCauseFilter |
Uses Filter module instead of Option |
Effect.catchSomeDefect |
Removed | No replacement |
Effect.optionFromOptional |
Effect.catchNoSuchElement |
Renamed |
Effect.catchTag |
Effect.catchTag |
Enhanced: accepts array of tags, optional orElse |
Effect.catchTags |
Effect.catchTags |
Enhanced: optional orElse fallback |
Effect.catchIf |
Effect.catchIf |
Enhanced: optional orElse fallback |
| (none) | Effect.catchReason |
NEW: catch nested reason within tagged error |
| (none) | Effect.catchReasons |
NEW: catch multiple nested reasons |
| (none) | Effect.unwrapReason |
NEW: promote nested reasons to error channel |
| (none) | Effect.catchEager |
NEW: synchronous recovery optimization |
| (none) | Effect.withErrorReporting |
NEW: report errors to registered ErrorReporters |
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.
- 7d ago First seen · 1,564 lines · 61 tokens per session scan A 032bd7352d59
effect-error-handling is a skill published in the GitHub repository mpsuesser/pi-effect-harness (24 stars, last pushed 2mo ago), licensed MIT. It adds 61 tokens to every session and 10,914 once invoked, about $0.0003 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 2026-08-30.
Other skills, from other repositories
effect-patterns-concurrency
Effect-TS patterns for Concurrency. Use when working with concurrency in Effect-TS applications.
effect-patterns-streams
Effect-TS patterns for Streams. Use when working with streams in Effect-TS applications.
effect-patterns-making-http-requests
Effect-TS patterns for Making Http Requests. Use when working with making http requests in Effect-TS applications.
effect-patterns-streams-sinks
Effect-TS patterns for Streams Sinks. Use when working with streams sinks in Effect-TS applications.
effect-patterns-error-handling
Effect-TS patterns for Error Handling. Use when working with error handling in Effect-TS applications.
effect-patterns-resource-management
Effect-TS patterns for Resource Management. Use when working with resource management in Effect-TS applications.