chore(upstream): track deferred September sync work

[BumpyClock]

Purpose and source records

This issue records deferred September upstream work. It does not approve every feature below or claim that the immediate sync patches are complete. Each item needs a separate scope decision and semantic adaptation.

Source	Exact audit identity
Neutron baseline	58be988690645917d35fd4b636a4ce2e3a11a9b6
Zed engine range	d9ad6aff67e47de43abb270d22de75dd950f1b48..5a9b9558db01a6b906cec2fb70a797affdc58cdd
Longbridge framework range	334bbed2e8c47d606eb79ab05ddcebd60b823429..cbdf5baa26a5c20ae5c1d7481bffdd1d0d2abd3d

Longbridge now uses longbridge/gpui-kit. The local partial clones at /tmp/zed and /tmp/longbridge-gpui-component are disposable. engine/UPSTREAM.md, engine/fork.toml, and framework/UPSTREAM.md remain the authoritative sync records. This issue does not advance their cursors.

Paths below are relative to the Neutron root. Line references refer to the baseline and can move after the immediate sync.

Windows Restart Manager

Source: 7f2a2c3c3e, zed-industries/zed#62987.

The upstream WM_QUERYENDSESSION and WM_ENDSESSION support can help installer-driven shutdown. It conflicts with Neutron message allocation and embedded-host lifetime policy.

Local paths: engine/crates/gpui_windows/src/platform.rs, engine/crates/gpui_windows/src/window.rs, engine/crates/gpui/src/app.rs, and framework/crates/app/src/handles.rs.

• Reserve a distinct message ID. Upstream uses WM_USER + 9, which Neutron assigns to WM_GPUI_VSYNC_THREAD_STOPPED at platform.rs:117.
• Route shutdown through the existing lifecycle. Preserve request_quit_with, run_will_exit, and VSync thread cleanup.
• Keep the embedded host alive unless its owner explicitly requests process termination. Do not copy unconditional process::exit.
• Coordinate updater policy with Design AppShell updater integration #41 rather than create a separate updater feature.

Acceptance requires native Windows end-session, cancellation, repeated quit, and reentrant quit observations. Confirm one lifecycle completion, VSync cleanup, and preservation of the embedded host.

Browser IME and focus

The current hidden input lacks the upstream text mirror. The full adaptation must address composition, context-sensitive deletion, selection import, and virtual keyboard focus together.

Local paths: engine/crates/gpui_web/src/{events.rs,window.rs}, a new ime_mirror.rs, engine/crates/gpui/src/{input.rs,platform.rs,window.rs}, and concrete framework input handlers under framework/crates/ui/src/input/.

Dependency order	Source
Extract required selection and geometry contracts from the pre-cursor API	9c3273201c, zed-industries/zed#60496
Introduce the UTF-16 mirror and browser edit import	224373ab88, zed-industries/zed#63201
Correct mobile keyboard focus	5f1f7e634b, zed-industries/zed#63220
Add explicit text-assistance configuration	8fc1a8a0c6, zed-industries/zed#63264
Bound the editable mirror range	d84e5d4992, zed-industries/zed#63294
Resolve rejected asynchronous selection imports	5218009a2d, zed-industries/zed#63311
Drive focus state from the current GPUI input handler	9decdcc1f2, zed-industries/zed#63629

Neutron lacks parts of the pre-cursor API despite the audit cursor. Extract only required contracts rather than import the full mobile API.

Preserve the handled-key guard before preventDefault() in events.rs. Implement real selection mutation in concrete handlers. Do not accept upstream empty selection setters as proof of support. Keep unsupported desktop capabilities explicit instead of silent no-ops.

Acceptance requires browser composition commit and cancellation, emoji and UTF-16 selection, autocorrect, word deletion, and Android slide-delete selection. Exercise concurrent application selection changes and editable-range boundaries. Confirm keyboard reopen, focus loss, and no duplicate input. Keep browser observations separate from native IME claims.

Portable touch and callout policy

Neutron has no portable gesture recognizer. These changes add a feature rather than repair existing gesture physics. The current PlatformInput and pointer-to-mouse path need a coordinated extension.

Local paths: engine/crates/gpui/src/{interactive.rs,window.rs,elements/div.rs}, a new gestures.rs, and engine/crates/gpui_web/src/{events.rs,window.rs,platform.rs}.

Dependency order	Source
Add raw touch dispatch and portable recognition after the required pre-cursor API	956a49e4ca, zed-industries/zed#63373
Add host-specific physics and browser prediction	76b1096cbd, zed-industries/zed#63505
Lock the dominant axis	5e28272c14, zed-industries/zed#63553
Add long-press arbitration	0855410ccd, zed-industries/zed#63561
Prevent prediction corrections from reversing motion	a85cf449ec, zed-industries/zed#63638
Add element-claimed direct touch drag	b3326e13c1, zed-industries/zed#63645

The focus and hover changes in a66fb6aebd, zed-industries/zed#63533, also need this touch state.

Reconcile synchronous draws after taps with deferred arena cleanup, retained layers, accessibility, and frame scheduling. Preserve reduced-motion policy. Native recognizer defaults do not prove native touch support.

Acceptance requires browser tap-versus-pan arbitration, pointer cancellation and ID reuse, nested scroll boundaries, axis lock, prediction reversal, and long-press or direct-drag ownership. Confirm that pans do not move keyboard focus and that momentum stops correctly.

Defer 9bda6b4e03, zed-industries/zed#63775, until an alternative interaction exists. Its canvas callout suppression alone provides no replacement long-press behavior.

Framework soft-wrap affinity and optional multi-cursor input

Source: 91217366a5, longbridge/gpui-kit#2656.

At an exact soft-wrap boundary, one logical offset can identify either adjacent visual row. Neutron needs an explicit affinity model before the upstream selection correction can transfer safely.

Local paths: framework/crates/ui/src/input/{state.rs,element.rs,movement.rs,text_wrapper.rs,selection.rs}.

Define the logical-offset and visual-row contract first. Then adapt hit tests, caret movement, and selection endpoints. Preserve UTF-8 boundaries, IME ranges, accessibility selection, and existing undo behavior.

Acceptance requires clicks on both sides of exact wrap boundaries, Shift-selection, vertical movement, and Home/End behavior. Include empty lines, multibyte text, and resize-induced wrap changes.

Multi-cursor input is a separate optional subtask. Source: cbdf5baa26, longbridge/gpui-kit#2837. Coordinate ownership with #23.

The upstream commit touches 13 input files and exceeds 3,600 insertions overall. It changes the selection model, undo, IME, and editor operations. Do not treat it as a routine cherry-pick. Resolve affinity and document the selection-model migration before implementation.

Optional font cache and browser font policy

Source: f1d27d545e, zed-industries/zed#63158.

This optimization prepares font-match caches before first use. Its value depends on startup cost and actual cache misses.

Local paths: engine/crates/gpui_wgpu/src/cosmic_text_system.rs, engine/crates/gpui/src/{text_system.rs,platform.rs}, and the application startup integration.

Measure startup, first text use, and memory before an API change. Keep cache preparation off the foreground path where safe. Confirm fallback font selection and behavior after font additions. Glyph-raster reuse belongs to the immediate implementation scope, not this deferred item.

Preserve bundled browser fonts. ef075910c9, zed-industries/zed#63493, removes defaults rather than supply a missing font API. Neutron already exposes add_fonts.

An optional small-artifact policy may use explicit configuration in engine/crates/gpui_web/src/platform.rs. Require artifact-size measurements and missing-font behavior before approval. Keep current applications compatible by default.

Bounded macOS prompt migration

Source: a60addb9a9, zed-industries/zed#59572.

Local paths: engine/crates/gpui_macos/src/{window.rs,platform.rs}.

Limit the migration to PlatformWindow::prompt, MacWindow main-thread proof, and owned NSAlert state. Preserve MainThreadMarker requirements. Do not expand this task into a general Objective-C rewrite.

Acceptance requires native macOS button results, Escape cancellation, deferred completion, focus restoration, and window closure while the prompt exists. Preserve callback ownership and AppShell shutdown behavior.

Renderer image evidence

Sources: fecc3273ed, zed-industries/zed#63244, and 74490daced, zed-industries/zed#63012.

Local paths: engine/crates/gpui_macos/src/metal_renderer.rs, engine/crates/gpui_windows/src/{directx_renderer.rs,window.rs}, and engine/crates/gpui_platform/.

Upstream headless Metal exposure and Windows image capture do not model all Neutron renderer state. Define the capture contract before an implementation import.

Require image evidence for retained-layer reuse, element backdrop blur, resize, scale changes, and device recovery. Record compositor-only native blur and overlay behavior separately when renderer readback cannot capture it. Do not classify a headless image as native presentation evidence. Coordinate overlay coverage with #36.

Fractional padding and stack protection

Source: b1a7ef0cf6, zed-industries/zed#62296.

Local paths: engine/crates/gpui/src/{taffy.rs,elements/div.rs}.

Neutron's to_taffy path does not use the same authored-padding snap as upstream. Transfer the regression test before the patch. Establish whether recomputed padding and layout padding disagree at fractional scale factors. Include percentage padding and scroll-end clamping.

Keep stacksafe protection. 41d72f6c1d, zed-industries/zed#63187, is only a future measurement and opt-in policy reference. This issue does not request its removal or default disablement.

License-source reconciliation

Source: ac5af8b9e1, zed-industries/zed#63573.

Upstream grants Apache-2.0 to the current upstream packages. That grant does not by itself establish the license of every retained historical Neutron source variant.

The source comparison found differences in engine/crates/zlog/src/filter.rs and engine/crates/zlog/src/sink.rs, including historical rotation code. engine/crates/ztracing/src/lib.rs differs in WASM and feature extraction. The engine/crates/ztracing_macro source matches the compared upstream source.

The current GPL-declared dependency graph is gpui -> sum_tree -> ztracing -> zlog/ztracing_macro. This issue does not authorize a blanket metadata relabel of that graph.

engine/LICENSE-AUDIT.md records the new grant and unresolved source differences separately. Its update does not change package licenses. The engine policy requires license notices to remain unchanged unless an authorized task explicitly names the migration.

Map every retained source file and material local change to an applicable license grant. Then select exact relicensed upstream source plus authorized local adaptations, or obtain an owner or rightsholder decision for unresolved source. Preserve required notices and attribution throughout that work.

Acceptance requires a source-to-license record, explicit treatment of historical differences, and inspection of the resulting cargo package artifacts. Confirm that package metadata and included notices agree with the reconciled source. Preserve registry ownership, asset provenance, and other publication blockers. Do not claim publication readiness from the upstream grant alone.

Lower-priority decisions

Candidate	Dependency and ownership
TextView max_lines: a9edc3e294, longbridge/gpui-kit#2829	Review framework/crates/ui/src/text/{text_view.rs,state.rs,inline.rs} and whole-line truncation semantics. Coordinate text-domain ownership with #14.
Inline SVG bytes: 4475eeb56a, longbridge/gpui-kit#2980	Neutron lacks the required engine SVG-bytes API. Define that contract before changes to framework/crates/ui/src/icon.rs or icon slots.
ScaleBand HashMap index: c6a68e0cfd, longbridge/gpui-kit#2885	Defer the index optimization and coordinate the API decision with #28. Measure large-domain benefit before new Eq + Hash constraints.

The immediate ScaleBand adaptation uses first-occurrence category deduplication and retains PartialEq-compatible values. Central tests remain pending. This issue makes no completion claim for that code.

The current deduplication construction is O(n^2), and each lookup is O(n). A future API or index choice needs measured large-domain benefit. Decide float and custom PartialEq compatibility before a HashMap migration. Preserve category order and equality behavior unless an explicit API decision changes them.

These candidates are not automatic Stage 2 approvals. Existing #28 owns chart-domain work. Existing #34 owns system notifications. Neither needs a duplicate feature request here.

Invariants, non-goals, and completion evidence

Preserve typed unsupported errors, embedded lifecycle, accessibility, custom cursor and font behavior, retained layers, overlay policy, and native blur. Keep framework dependencies on public engine interfaces.

Exclude wholesale gpui-base or gpui-shell extraction, crate rebrand, native-menu replacement, and Zed application code. Do not copy upstream root manifests or lockfiles. Do not remove native blur or retained layers.

Do not import already-equivalent notification timers or the WASM application-lifetime example fix as deferred corrections. This issue makes no license or source-provenance completion claim.

For each approved item, record exact source identity, semantic changes, and remaining unsupported behavior. Run affected unit or headless checks and applicable native Stage 1 profiles through the repository scripts. Preserve downstream framework checks for engine changes.

Keep compile-only, headless, browser, software-GPU, hardware-GPU, and native observations distinct. Record exact commands, environments, artifacts, and omissions. Require native evidence for claims that depend on native lifecycle or presentation.

[BumpyClock]

Platform acceptance for the corrective batch

The local corrective batch retains the recorded sync cursors. The September
sections in engine/UPSTREAM.md and framework/UPSTREAM.md list its adaptations.
The baseline commit in this issue does not identify those uncommitted changes.

macOS conformance exercised lifecycle, menu commands, interaction contracts,
and StoryApp smoke. That evidence does not establish Windows or Linux behavior.

The Windows cross-target attempt stopped before the changed backend compiled.
The host lacks lib.exe and windows.h. The Linux musl attempt stopped because
x86_64-linux-musl-gcc and x86_64-linux-musl-g++ are absent.

Before acceptance, run the existing native CI profiles on the committed source.
Include the following affected package checks on their native hosts:

cargo test --locked -p gpui_windows --all-features --all-targets
cargo test --locked -p gpui_linux --no-default-features --features x11,test-support --lib
cargo test --locked -p gpui_linux --no-default-features --features wayland,test-support --lib

Windows observations must cover mixed-DPI initial placement, the poisoned-target
color-glyph regression, and restart behavior with and without PowerShell.
Linux observations must cover X11 application identity, Wayland error delivery,
and sheets with client, server, and tiled decorations.

Keep these acceptance tasks separate from the larger deferred feature decisions.
Do not advance exact-source support claims from the macOS or headless results.

Existing WASM test-platform gaps

The nightly platform, a11y, and view_example targets compile. The new
test_macros integration target also compiles on WASM with test-support.
Its asynchronous wrapper is native-only.

A broader GPUI --tests command still finds six native accessibility calls in
unchanged elements/div.rs and elements/retained_layer_tests.rs. Those tests
call Window::handle_a11y_action, which is unavailable on WASM.
The standalone scheduler test target also requires WASM getrandom backend
configuration.

Resolve those existing test-platform gaps before a full WASM test-support claim.
Do not restore synchronous production APIs to make those targets compile.