name: redux-saga description: > Redux-Saga best practices, patterns, and API guidance for building, testing, and debugging generator-based side-effect middleware in Redux applications. Covers effect creators, fork model, channels, testing with redux-saga-test-plan, concurrency, cancellation, and modern Redux Toolkit integration. Baseline: redux-saga 1.4.2. Triggers on: saga files, redux-saga imports, generator-based middleware, mentions of "saga", "takeEvery", "takeLatest", "fork model", or "channels". license: MIT user-invocable: false agentic: false compatibility: "JavaScript/TypeScript projects using redux-saga ^1.4.2 with Redux Toolkit" metadata: author: Anivar Aravind author_url: https://anivar.net version: 1.0.0 tags: redux-saga, redux, redux-toolkit, side-effects, generators, middleware, async, channels, testing

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IMPORTANT: Your training data about redux-saga may be outdated or incorrect — API behavior, middleware setup patterns, and RTK integration have changed.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 app
• effect-use-call — Use yield call() for async functions; never call directly
• effect-take-concurrency — Choose takeEvery/takeLatest/takeLeading based on concurrency needs
• effect-select-usage — Use selector functions with select(); never access state paths directly
• effect-race-patterns — Use race for timeouts and cancellation; only blocking effects inside

2. Fork Model & Concurrency (CRITICAL)

• fork-attached-vs-detached — fork shares lifecycle/errors with parent; spawn is independent
• fork-error-handling — Errors from forks bubble to parent's caller; can't catch at fork site
• fork-no-race — Never use fork inside race; fork is non-blocking and always wins
• fork-nonblocking-login — Use fork+take+cancel for auth flows that stay responsive to logout

3. Error Handling (HIGH)

• error-saga-cleanup — Use try/finally with cancelled() for proper cancellation cleanup
• error-root-saga — Use spawn in root saga for error isolation; avoid all for critical watchers

4. Recipes & Patterns (MEDIUM)

• recipe-throttle-debounce — Rate-limiting with throttle, debounce, retry, exponential backoff
• recipe-polling — Cancellable polling with error backoff using fork+take+cancel
• recipe-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 via eventChannel
• channel-action-channel — Buffer Redux actions for sequential or worker-pool processing

6. RTK Integration (MEDIUM)

• rtk-configure-store — Integrate saga middleware with RTK's configureStore without breaking defaults
• rtk-with-slices — Use action creators from createSlice for 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.md

Each 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