Fix multi-diff and native host event leaks

[roblourens]

Problem

This fixes two independent leaks surfaced by disposable and event-buffer diagnostics.

Failed multi-diff model resolution

Opening the Agents window Changes multi-diff can attempt to resolve entries that cannot be opened as text, such as a directory or binary file. If either createModelReference call rejected, the surrounding Promise.all returned immediately without disposing the per-item DisposableStore. A reference acquired by the other call could also be lost without disposal, including when that call completed after its sibling had already rejected.

This produced [LEAKED DISPOSABLE] warnings rooted in MultiDiffEditorInput._createModel and could retain text model references after failed multi-diff item resolution.

Unconsumed native host blur buffer

ProxyChannel.fromService eagerly subscribes to and buffers service events so startup events can be replayed when an IPC client attaches. onDidBlurMainWindow has no IPC consumer, so every main-window blur was retained indefinitely and the eager proxy subscription was unnecessary. In dev builds this produced an [Event.buffer][onDidBlurMainWindow] potential LEAK detected warning after buffered events remained unconsumed.

This is long-standing rather than a recent regression:

• 42f5594892 (2023-11-02) split focus/blur into main-only and main-or-auxiliary events. Renderer consumers moved to the combined event, leaving the main-only blur buffer without an IPC listener.
• a837f16fbe (2026-02-28) added Event.buffer leak diagnostics, making the existing unbounded buffer visible.

The main-only focus event remains buffered intentionally because Settings Sync consumes it through the shared-process native host channel.

Fix

• wait for both model-reference acquisitions with Promise.allSettled
• dispose the multi-diff item store when either acquisition fails or when its cached item is removed while resolution is pending
• preserve handling for synchronous model-reference failures
• add an opt-in unbufferedEvents proxy-channel option that subscribes only when an IPC client listens
• make onDidBlurMainWindow lazy/unbuffered while preserving the event API for future consumers
• cover lazy subscription, lack of replay, and listener cleanup with an IPC unit test

CC @hediet, who authored the original multi-diff model-resolution path.

Validation

• npm run gulp compile
• npm run typecheck-client
• ./scripts/test.sh --run src/vs/base/parts/ipc/test/common/ipc.test.ts (23 passing)
• npm run precommit

(Written by Copilot)

[Copilot]

Pull request overview

Note

Copilot couldn't run its full agentic review because it didn't start before the timeout. Make sure your repository has a runner available, or add a copilot-code-review.yml file specifying one with the runs-on attribute. See the docs for more details.

Makes multi-diff model reference acquisition more failure-safe by ensuring partial successes are disposed when the other acquisition fails, and by handling disposal during in-flight acquisition.

Changes:

• Switched from Promise.all to Promise.allSettled for original/modified model reference acquisition.
• Disposes successfully acquired references when the other acquisition fails.
• Disposes acquired references if the parent store was disposed while acquisitions were in progress.

Show a summary per file

File	Description
src/vs/workbench/contrib/multiDiffEditor/browser/multiDiffEditorInput.ts	Ensures model references are cleaned up correctly across partial failures and disposal during acquisition

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 2
• Review effort level: Lite