ADR 0040: Customizable in-app notifications

Date: 2026-10-16 Status: Implementation decision for the maintainer-requested notification controls.

Decision

Reuse the existing floating notification stack for confirmed Snooze, Return to inbox, Archive and Trash outcomes. Snooze includes its chosen local return date and time. Publish success only after the action completes. A later inbox-refresh failure keeps that confirmed outcome and adds a separate warning to refresh the inbox, rather than implying that the action must be repeated.

Add Settings, Notifications with independent switches for in-app new-mail counts and action confirmations. Offer Bottom right, Bottom center and Top right, and 3, 6 or 10 seconds or Until dismissed. Defaults retain Bottom right and six seconds with both switches enabled. Provide a generic preview and reset.

Store only validated display choices in versioned localStorage. These choices contain no mailbox data. A failed write keeps the current in-memory selection and reports that it could not be saved. Invalid stored values fall back to defaults.

Errors, uncertain sends and Sent-copy warnings stay visible until dismissed regardless of the switches or duration. Keep privacy masking, queued outcomes, hover/focus pause, dismissal and keyboard focus behavior. The new-mail switch applies to in-app arrivals; native operating-system notifications retain their existing behavior.

Verification

Require mounted synthetic action, Settings and notification tests for confirmed, pending and failed operations, refresh failure, persistence and invalid values, switches, positions, durations, preview, reset and error persistence. Run the application test suite and strict build, then review the exact diff independently. PRODUCT.md prohibits live browser application testing. Native appearance, physical input and live-provider delivery remain separate acceptance work.