[pixari]

Follow-up to #1019 (#1016).

The compatibility problem

#1019 added every N weeks on <weekdays> and made quick add, CalDAV, the importer and the vault write it, even for "every other Friday" due on a Friday, where 1.0's every 2 weeks means exactly the same. A 1.0.0 client cannot parse the new form: in v1.0.0's completeTask (web/src/lib/ops.ts), seriesRule() returns null for an unparseable rule, the task takes completePlain, and the series ends for good. docs/stability.md promises that every 1.x client (including a web app still cached on a phone) keeps working against a newer server, so this was data loss on a 1.0 device.

The fix

• every N weeks on <day> on a task whose due date (at write time) falls on that day is stored as every N weeks, which the due date anchors. The until / for N times end is kept. The two give the same dates, including catch-up.
• Several weekdays with N > 1, a due date on another weekday, or no due date keep the new form, which is the only correct one.
• One function per language: recurrence.Compatible (Go) and compatibleRule (TS), pinned by the new compatible vectors in recurrence.vectors.json. Every writer goes through it: quick add (both parsers), the repeat field (setRecurrence) and planTask, REST (canonicalizeRecurrence, using the body's due or the task's), the agent tools (create and update), CalDAV (FromRRULE, which also covers the importer's and the vault notes' RRULEs), the importer planner and own-export import, the vault's 🔁 lines, and a series split (Go and web).
• Compatibility test: internal/recurrence/recurrence10 and web/src/lib/testdata/recurrence-1.0.ts are frozen copies of the v1.0.0 grammar. Check / check10 fail a stored rule that 1.0 can't read when a 1.0 rule gives the same dates over 60 occurrences. Every writer's test runs its output through it, and so does every quick-add vector, in both languages. TestNotLinked keeps the Go copy out of both binaries.
• The three inputs from Quick add: "today … every other Saturday" loses the weekday; "and repeat" and "starting" stay in the title #1016 are now vectors with today = Wednesday 2026-11-04 and today = Saturday 2026-11-07.
• What remains (a rule only 1.1 can express shows as text on a 1.0 device, and completing it there ends the series) is documented in docs/stability.md under what may change within 1.x, with the advice to update devices. I left resume-detection out: the op doesn't record which client version completed the task, and "completed with a rule 1.0 can't read" would also catch series someone ended on purpose.

What each writer stores now

Input	Due	Stored
"every other Saturday" (quick add, import, repeat field, REST, agent, vault)	Saturday	every 2 weeks
"take the bins out today and repeat every other Saturday" typed on a Wednesday	Wednesday (today)	every 2 weeks on saturday
same line typed on a Saturday	Saturday	every 2 weeks
CalDAV FREQ=WEEKLY;INTERVAL=2;BYDAY=SA, Saturday DTSTART/DUE	Saturday	every 2 weeks
CalDAV same RRULE, Wednesday DUE	Wednesday	every 2 weeks on saturday

OpenSpec change recurrence-1-0-compatible (archived): it adds "Rules a 1.0 client reads" to recurring-tasks and updates the "every other" scenarios in natural-language-capture. Docs: stability.md, recurrence.md (new "Rules older devices read"), quick-add.md, repeat-rules.md, caldav.md, import.md, plus AGENTS.md and architecture.md for the new package. The changelog fragment from #1019 now describes the final behaviour.

Checks

go test ./..., go vet ./..., staticcheck on the touched packages; npx vitest run src/lib/nlp src/lib/recurrence src/lib/recurring src/lib/recurrenceCompatible src/lib/seriesSplit src/lib/habits src/app/task-detail (1089 tests), npm run typecheck, make web-lint, npm run build, make bundle-budget (687.0 of 687 KB), make docs-check, make openspec-validate, make repo-check, make i18n-check.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Bkw4TZLFDGeMdZR3vWZF13