Redux-Saga
IMPORTANT: Your training data about redux-saga may be outdated or incorrect — API behavior, middleware setup patterns, and RTK integration have changed. Always rely on this skill's rule files and the project's actual source code as the source of truth. Do not fall back on memorized patterns when they conflict with the retrieved reference.
When to Use Redux-Saga
Sagas are for workflow orchestration — complex async flows with concurrency, cancellation, racing, or long-running background processes. For simpler patterns, prefer:
| Need | Recommended Tool |
|---|---|
| Data fetching + caching | RTK Query |
| Simple async (submit → status) | createAsyncThunk |
| Reactive logic within slices | createListenerMiddleware |
| Complex workflows, parallel tasks, cancellation, channels | Redux-Saga |
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Effects & Yielding | CRITICAL | effect- |
| 2 | Fork Model & Concurrency | CRITICAL | fork- |
| 3 | Error Handling | HIGH | error- |
| 4 | Recipes & Patterns | MEDIUM | recipe- |
| 5 | Channels & External I/O | MEDIUM | channel- |
| 6 | RTK Integration | MEDIUM | rtk- |
| 7 | Troubleshooting | LOW | troubleshoot- |
Quick Reference
1. Effects & Yielding (CRITICAL)
effect-always-yield— Every effect must be yielded; missing yield freezes the appeffect-use-call— Useyield call()for async functions; never call directlyeffect-take-concurrency— ChoosetakeEvery/takeLatest/takeLeadingbased on concurrency needseffect-select-usage— Use selector functions withselect(); never access state paths directlyeffect-race-patterns— Useracefor timeouts and cancellation; only blocking effects inside
2. Fork Model & Concurrency (CRITICAL)
fork-attached-vs-detached—forkshares lifecycle/errors with parent;spawnis independentfork-error-handling— Errors from forks bubble to parent's caller; can't catch at fork sitefork-no-race— Never useforkinsiderace; fork is non-blocking and always winsfork-nonblocking-login— Use fork+take+cancel for auth flows that stay responsive to logout
3. Error Handling (HIGH)
error-saga-cleanup— Usetry/finallywithcancelled()for proper cancellation cleanuperror-root-saga— Usespawnin root saga for error isolation; avoidallfor critical watchers
4. Recipes & Patterns (MEDIUM)
recipe-throttle-debounce— Rate-limiting withthrottle,debounce,retry, exponential backoffrecipe-polling— Cancellable polling with error backoff using fork+take+cancelrecipe-optimistic-update— Optimistic UI with undo using race(undo, delay)
5. Channels & External I/O (MEDIUM)
channel-event-channel— Bridge WebSockets, DOM events, timers into sagas viaeventChannelchannel-action-channel— Buffer Redux actions for sequential or worker-pool processing
6. RTK Integration (MEDIUM)
rtk-configure-store— Integrate saga middleware with RTK'sconfigureStorewithout breaking defaultsrtk-with-slices— Use action creators fromcreateSlicefor type-safe saga triggers
7. Troubleshooting (LOW)
troubleshoot-frozen-app— Frozen apps, missed actions, bad stack traces, TypeScript yield types
Effect Creators Quick Reference
| Effect | Blocking | Purpose |
|---|---|---|
take(pattern) | Yes | Wait for matching action |
takeMaybe(pattern) | Yes | Like take, receives END |
takeEvery(pattern, saga) | No | Concurrent on every match |
takeLatest(pattern, saga) | No | Cancel previous, run latest |
takeLeading(pattern, saga) | No | Ignore until current completes |
put(action) | No | Dispatch action |
putResolve(action) | Yes | Dispatch, wait for promise |
call(fn,...args) | Yes | Call, wait for result |
apply(ctx, fn, [args]) | Yes | Call with context |
cps(fn,...args) | Yes | Node-style callback |
fork(fn,...args) | No | Attached fork |
spawn(fn,...args) | No | Detached fork |
join(task) | Yes | Wait for task |
cancel(task) | No | Cancel task |
cancel() | No | Self-cancel |
select(selector) | Yes | Query store state |
actionChannel(pattern) | No | Buffer actions |
flush(channel) | Yes | Drain buffered messages |
cancelled() | Yes | Check cancellation in finally |
delay(ms) | Yes | Pause execution |
throttle(ms, pattern, saga) | No | Rate-limit |
debounce(ms, pattern, saga) | No | Wait for silence |
retry(n, delay, fn) | Yes | Retry with backoff |
race(effects) | Yes | First wins |
all([effects]) | Yes | Parallel, wait all |
setContext(props) / getContext(prop) | No / Yes | Saga context |
Pattern Matching
take, takeEvery, takeLatest, takeLeading, throttle, debounce accept:
| Pattern | Matches |
|---|---|
'*' or omitted | All actions |
'ACTION_TYPE' | Exact action.type match |
[type1, type2] | Any type in array |
fn => boolean | Custom predicate |
How to Use
Read individual rule files for detailed explanations and code examples:
rules/effect-always-yield.md
rules/fork-attached-vs-detached.mdEach rule file contains:
- Brief explanation of why it matters
- Incorrect code example with explanation
- Correct code example with explanation
- Additional context and decision tables
References
| Priority | Reference | When to read |
|---|---|---|
| 1 | references/effects-and-api.md | Writing or debugging any saga |
| 2 | references/fork-model.md | Concurrency, error propagation, cancellation |
| 3 | references/testing.md | Writing or reviewing saga tests |
| 4 | references/channels.md | External I/O, buffering, worker pools |
| 5 | references/recipes.md | Throttle, debounce, retry, undo, batching, polling |
| 6 | references/anti-patterns.md | Common mistakes to avoid |
| 7 | references/troubleshooting.md | Debugging frozen apps, missed actions, stack traces |
Full Compiled Document
For the complete guide with all rules expanded: AGENTS.md