refactor(main): introduce explicit AniList runtime transitions

backlog/tasks/task-79 - Introduce-explicit-runtime-state-transitions-and-reducers-in-main.md

@@ -1,10 +1,11 @@
 ---
 id: TASK-79
 title: Introduce explicit runtime state transitions and reducers in main
-status: To Do
-assignee: []
+status: Done
+assignee:
+  - '@sudacode'
 created_date: '2026-02-18 11:43'
-updated_date: '2026-02-18 11:43'
+updated_date: '2026-02-22 00:10'
 labels:
   - main-process
   - state-management
@@ -41,15 +42,49 @@ Main runtime state is currently mutable from many callsites. This task introduce
 
 ## Acceptance Criteria
 <!-- AC:BEGIN -->
-- [ ] #1 Critical runtime state domains mutate through explicit transition helpers
-- [ ] #2 State invariants are test-covered
-- [ ] #3 Direct ad-hoc mutation in migrated domains is removed
-- [ ] #4 Ownership/mutation rules documented
+- [x] #1 Critical runtime state domains mutate through explicit transition helpers
+- [x] #2 State invariants are test-covered
+- [x] #3 Direct ad-hoc mutation in migrated domains is removed
+- [x] #4 Ownership/mutation rules documented
 <!-- AC:END -->
 
+## Implementation Plan
+
+<!-- SECTION:PLAN:BEGIN -->
+Implementation plan (writing-plans):
+1) Add pure reducer-style transition helpers in `src/main/state.ts` for critical AniList domains: client-secret state, retry queue metadata, media-guess runtime state, and tracking in-flight flag. Add focused tests in `src/main/state.test.ts`.
+2) Rewire `src/main.ts` to use transition helpers instead of direct mutation for migrated domains in runtime deps wiring (`buildAnilistStateRuntimeMainDepsHandler`, media-guess state deps, retry-update deps, post-watch in-flight setter).
+3) Add/extend invariant tests in `src/main/runtime/anilist-state.test.ts` and `src/main/runtime/anilist-media-state.test.ts` (metadata preservation, idempotent reset, scoped-field resets).
+4) Document ownership/mutation rules in `docs/architecture.md` under composition guidance and run verification gates (`bun run build`, `bun run test:core:src`).
+5) Record evidence and AC/DoD progress in TASK-79 notes.
+
+Parallelization: run code-wiring slice and tests/docs slice in parallel subagents where safe, then reconcile and run final gates in the main session.
+
+Detailed step-by-step plan saved at `docs/plans/2026-02-21-task-79-runtime-state-reducers.md`.
+<!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+2026-02-21: Started implementation pass via writing-plans/executing-plans workflow. Scoping to explicit transition helpers/reducers for critical AniList runtime state domains in `src/main.ts`/`src/main/state.ts`, plus invariant tests and architecture ownership rules docs.
+
+Implemented explicit AniList runtime transition helpers/reducers in `src/main/state.ts` and rewired migrated `src/main.ts` mutation paths through them (client-secret state, retry queue metadata, media-guess runtime state, in-flight flag).
+
+Added focused reducer tests in `src/main/state.test.ts` plus invariants coverage updates in `src/main/runtime/anilist-state.test.ts` and `src/main/runtime/anilist-media-state.test.ts`.
+
+Documented runtime ownership/mutation rules for migrated domains in `docs/architecture.md` under Composition Pattern.
+
+Validation evidence: `bun test src/main/state.test.ts src/main/runtime/anilist-state.test.ts src/main/runtime/anilist-media-state.test.ts` (12 pass), `bun run build` (pass), `bun run test:core:src` (219 pass, 6 skip, 0 fail).
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Introduced explicit reducer-style runtime transitions for critical AniList state in the main process by adding pure transition helpers in `src/main/state.ts` and routing migrated writes in `src/main.ts` through those helpers. Removed ad-hoc direct mutation in migrated domains (client-secret state, retry queue metadata, media-guess runtime state, in-flight flag), added focused and invariant tests, and documented ownership/mutation rules in architecture docs. Validation passed with focused state suites, full build, and core source test lane.
+<!-- SECTION:FINAL_SUMMARY:END -->
+
 ## Definition of Done
 <!-- DOD:BEGIN -->
-- [ ] #1 Core tests pass after migration
-- [ ] #2 No behavior regressions in startup/IPC/overlay flows
+- [x] #1 Core tests pass after migration
+- [x] #2 No behavior regressions in startup/IPC/overlay flows
 <!-- DOD:END -->
-