ADR 0029: Separate native-window and work-panel resize ownership

• Status: Superseded in part by ADR 0032
• Date: 2026-07-28
• Related: 01-ui-ia · 08-component-spec §5 · 09-interaction-patterns §8 · 01-ipc-protocol · decision D156

ADR 0032 supersedes the clauses that responsively clamp the panel inside the existing client area and prohibit all panel-driven native geometry changes. Main ownership of BrowserWindow geometry, renderer ownership of committed panel width, and the divider gesture/commit rules remain in force.

Context

Work-panel visibility and divider commits previously called window/resizeBy so Electron could grow or shrink the native window. Renderer window.resize events then inferred whether the user moved the native right edge and wrote part of that delta back into the panel width. Time-limited attribution tickets attempted to distinguish those programmatic events from real window gestures.

This formed a circular ownership model: the panel changed the native window, and the native window changed the panel. It produced a second layout jump after divider release, stale asynchronous growth on rapid open/close, window-position drift near a display edge, platform-specific behavior, and preference values that changed during an unrelated native resize.

Decision

Native window geometry and renderer column geometry have independent owners:

1. Electron Main exclusively owns BrowserWindow bounds and persists the actual normal bounds. The supported minimum is 1040x700.
2. The renderer owns one preferred work-panel width in localStorage. The effective width is derived by clamping that preference against the current viewport, visible sidebar, and MainChat reserve.
3. Native window-edge gestures resize the shell only. They may temporarily clamp the effective panel width but never overwrite its preference.
4. The work-panel divider resizes internal columns only. Pointer math is anchored to the gesture start; move rendering is frame-coalesced; release commits once; Escape, pointer cancellation, and lost capture roll back.
5. Opening, collapsing, session-switching, and closing the panel never change native bounds on any platform.
6. The renderer-to-Main window/resizeBy IPC method, programmatic resize attribution tickets, panel growth tracking, and persisted-width offset are removed.

Consequences

• Divider feedback remains continuous through release instead of triggering a second native resize.
• Native edge behavior is symmetric and matches platform window conventions.
• Windows, macOS, and Linux share one panel interaction model.
• A temporarily constrained panel returns to its preferred width when space becomes available.
• The preload surface is smaller, and Electron window-state persistence no longer needs a panel-specific offset.
• Normal bounds are read independently of maximized/fullscreen state and are flushed synchronously on close so a pending debounce cannot lose them.
• Opening a panel reallocates the existing client area, so MainChat can become narrower until the operator resizes either the divider or native window.

Alternatives

Keep delta IPC and add request identifiers

Rejected. Request identifiers can reject stale replies but do not remove the circular geometry ownership or the post-release layout jump.

Let Electron own the complete three-column layout

Rejected. Main does not know renderer sidebar state or content constraints, and moving split-pane layout across IPC would add latency and duplicate DOM truth.

Keep native right-edge ownership for the work panel

Rejected. Edge-source inference is not reliable across frameless windows, display scaling, macOS window chrome, and Wayland. A native edge should retain its standard meaning: resize the window.

References

• docs/spec/03-runtime/01-ipc-protocol.md
• docs/spec/04-ux/01-ui-ia.md
• docs/spec/04-ux/07-ui-design-system.md
• docs/spec/04-ux/08-component-spec.md
• docs/spec/04-ux/09-interaction-patterns.md
• docs/spec/06-delivery/04-e2e-test-plan.md (E2E-056)
• docs/spec/08-meta/decisions-log.md (D156)