fix(server): keep scheduled-task intervals on elapsed time across DST

[Sypher760-gif]

Problem

The interval contract specifies a fixed number of milliseconds, but the scheduler adds them to a zoned wall clock. In New York at 2026-11-01T06:30:00Z, a one-minute task persists its next run at 05:31Z, 59 minutes in the past. Two-hour intervals also become one hour at spring-forward or three hours at fall-back.

Change

Use DateTime.addDuration in the existing interval branch, retaining the one-minute floor. Add service regressions for creation, persisted listing, pause/resume and failed dispatch completion, with UTC, Tokyo and fixed local-time controls.

Scope and approval

This restores the existing fixed-millisecond contract with one production change and focused tests. It qualifies for CONTRIBUTING.md's very small, focused obvious-bug exception: the change repairs duration arithmetic within an existing capability and needs no new feature, schema, client or execution-policy change.

Closed, unmerged PR #14714 identified the unrestricted calendar-arithmetic defect and explicitly left it unchanged while repairing a proposed restricted path. This fixes that existing residual and credits the earlier discovery. A refreshed scoped issue/PR/discussion and contributor-claim review found no matching active repair as of 2026-10-04.

Verification

Windows x64, Node 26, TypeScript 7.0.2, rebased onto main @ 50647de0 with a frozen-lockfile install.

• vp test run apps/server/src/scheduledTasks: 8 files, 70 tests passed, including the 7 new service cases in ScheduledTaskService.interval.test.ts. They run the real service, schema and persistence paths against in-memory SQLite, with provider effects mocked.
• With Schedule.ts reverted to main, 3 of the 7 fail (the America/New_York spring-forward and fall-back cases) and 4 controls pass.
• tsc --noEmit -p apps/server/tsconfig.json: exit 0, 0 errors. Format is clean on the 2 changed files. Lint reports one existing warning (describeSchedule is unused on main).

No Linux/macOS, UI, live-provider, scheduler soak or repo-wide suite validation is claimed.

Model: GPT-6.1 Sol (build, review) and Claude Sonnet 5.5 (rebase, test fix), Harness: Codex CLI and Hermes in T3 Code

[macroscopeapp]

Approvability

Verdict: Approved at 9c0529c

Macroscope's review found this PR approvable — This is a narrowly scoped scheduling bug fix: one production line changes interval calculations to preserve elapsed milliseconds across DST, while fixed-time behavior and the existing interval floor remain intact. The accompanying tests cover the affected service paths without introducing schema, default, deployment, security, or static-analysis changes.

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[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Path: .coderabbit.config.ts
• Review profile: CHILL
• Plan: Advanced
• Run ID: 49c25f73-5481-4e93-abd4-fec70a1b1a7c

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📥 Commits

Reviewing files that changed from the base of the PR and between 9c0529c and 59ece38.

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📒 Files selected for processing (2)

• apps/server/src/scheduledTasks/Schedule.ts
• apps/server/src/scheduledTasks/ScheduledTaskService.interval.test.ts

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📝 Walkthrough

📝 Walkthrough

📝 Walkthrough

Walkthrough

Interval schedules now advance by adding a duration, with the existing minimum interval applied. Tests cover interval schedules across time zones and daylight-saving transitions, plus fixed-time schedules around New York clock changes.

Changes

Scheduled task scheduling

Layer / File(s)	Summary
Interval advancement and schedule tests apps/server/src/scheduledTasks/Schedule.ts, apps/server/src/scheduledTasks/ScheduledTaskService.interval.test.ts	Interval schedules use duration-based addition while retaining the minimum interval. Tests check next-run times across time zones and daylight-saving transitions, including fixed-time schedules.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

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Merge Risk: ⚪ Minimal · up to 59ece

The interval change is ready to merge after normal checks; no actionable scheduling risk remains identified.

Pre-merge checks | 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly and concisely describes the main change: preserving elapsed-time intervals across daylight-saving transitions. It uses an appropriate conventional commit format.
Description check		The description includes all required sections. It explains the problem, the implementation, scope and approval rationale, focused verification results, limitations, and agent details.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

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[maria-rcks]

Note

Written by claude-opus-5-5 on behalf of Maria

Hi! We are cleaning up open PRs, and this one does not say which model or harness was used to create it. If this change is really important, we recommend rebuilding the PR with a newer model and noting the model and harness in the PR description.

[maria-rcks]

Note

Written by claude-opus-5-5 on behalf of Maria

Reopening, this was closed by mistake. Sorry for the noise!