Wrdn Effect Promise Exit

You fix one pattern: a React handler awaits an effect-atom mutation in mode: "promise" and catches failures with try/catch.

The preferred UI boundary is mode: "promiseExit" plus Exit.isFailure. This keeps mutation failures as values, matches Effect's error model, and prevents optimistic mutation cleanup from depending on thrown exceptions.

Trace before changing

1. Find the mutation setter. Look for const doX = useAtomSet(<mutationAtom>, { mode: "promise" }).
2. Confirm it is an effect-atom mutation boundary. The setter should come from @effect/atom-react and a mutation atom from ./atoms, ../api/atoms, or plugin React atoms.
3. Find thrown-control handling. The same handler has try { await doX(...) } catch (e) { ... }, usually setting error text, resetting adding/saving, or showing a toast.
4. Check for non-mutation async work in the same block. If the block also awaits follow-up mutations, convert those to promiseExit too or keep a narrow boundary only around truly non-effect APIs.
5. Do not rewrite unrelated local async code. Probe requests, OAuth popup helpers, fetch, and browser APIs may need a different skill unless the lint finding specifically points at the mutation call.

Fix shape

• Change the setter to { mode: "promiseExit" }.
• Import * as Exit from "effect/Exit" if missing.
• Import * as Option from "effect/Option" only when extracting an optional error.
• Replace try/catch around the mutation with:
  • const exit = await doX(args);
  • if (Exit.isFailure(exit)) { ...; return; }
  • success work after the failure branch.
• Use Exit.findErrorOption(exit) when preserving an existing error message or typed error branch.
• Keep existing typed error handling when present, e.g. SecretInUseError, ConnectionInUseError.

Bad

const doAdd = useAtomSet(addGraphqlSource, { mode: "promise" });

const handleAdd = async () => {
  setAdding(true);
  setAddError(null);
  try {
    await doAdd({
      params: { scopeId },
      payload,
      reactivityKeys: sourceWriteKeys,
    });
    props.onComplete();
  } catch (e) {
    setAddError(e instanceof Error ? e.message : "Failed to add source");
    setAdding(false);
  }
};

Good

import * as Exit from "effect/Exit";
import * as Option from "effect/Option";

const doAdd = useAtomSet(addGraphqlSource, { mode: "promiseExit" });

const handleAdd = async () => {
  setAdding(true);
  setAddError(null);
  const exit = await doAdd({
    params: { scopeId },
    payload,
    reactivityKeys: sourceWriteKeys,
  });
  if (Exit.isFailure(exit)) {
    const error = Exit.findErrorOption(exit);
    setAddError(
      Option.isSome(error) && error.value instanceof Error
        ? error.value.message
        : "Failed to add source",
    );
    setAdding(false);
    return;
  }
  props.onComplete();
};

Follow-up mutation chains

If success work depends on the mutation result, read it after the failure branch:

const exit = await doAdd(args);
if (Exit.isFailure(exit)) {
  setAdding(false);
  return;
}

const sourceId = exit.value.namespace;

If a follow-up effect-atom mutation can fail and the UI treats that as add failure, make that setter promiseExit too and branch the same way. Do not put the follow-up mutation in try/catch just because the first mutation now returns Exit.

What not to report

• try/catch around non-effect APIs such as new URL, JSON.parse, raw fetch, or browser popup code. Those may be real lint findings, but they need a different remediation skill.
• useAtomSet(..., { mode: "promise" }) with no local failure handling and no lint finding. Some call sites intentionally let callers decide the boundary.
• Tests or SDK/server Effect code. This skill is for React/effect-atom UI mutation handlers.
• Manual optimistic placeholder cleanup. Use wrdn-effect-atom-optimistic for that; if both patterns appear together, fix optimistic plumbing first, then use promiseExit for the remaining mutation boundary.

Output requirements

When reviewing, report:

• File and line of the useAtomSet(..., { mode: "promise" }) or try/catch.
• Mutation being called.
• Why it should return Exit at this UI boundary.
• Fix: the exact setter mode and the failure branch to add.

When editing, keep changes local to the handler and imports unless a follow-up mutation in the same success path must also become promiseExit.