/vcs/diff can OOM in desktop-layout web UI on umbrella workspaces with many nested git repos #24049

Description

I’m seeing repeated OpenCode OOM crashes caused by GET /vcs/diff on a workspace that is an umbrella/meta-repo containing many nested git repos and worktrees.

Important context:

• I am not intentionally using the review/diff UI.
• I am using the web UI in a normal desktop browser, not the desktop app.
• The issue still reproduces with Oh-My-OpenCode disabled.
• My workspace layout contains many nested repos/worktrees, and OpenCode’s vcsDiff does not handle that layout well.

What I found:

• In the logs, multiple actual Out of memory failed events happen while one or more GET /vcs/diff requests are in flight.
• In source, /vcs/diff ultimately builds full-file patches using structuredPatch(..., { context: Number.MAX_SAFE_INTEGER }), which looks extremely memory-heavy.
• In the app source, the desktop-layout session page can auto-enable review/diff behavior when the file tree is open, even if the review tab was not explicitly opened.

Source references:

• Route:
  • packages/opencode/src/server/routes/instance/index.ts
• Implementation:
  • packages/opencode/src/project/vcs.ts
• Auto-trigger path in app:
  • packages/app/src/pages/session.tsx

Specific code paths:

• packages/opencode/src/server/routes/instance/index.ts:155-180
• packages/opencode/src/project/vcs.ts:49-50
• packages/app/src/pages/session.tsx:586-610
• packages/app/src/pages/session.tsx:1259-1289

Relevant implementation detail from packages/opencode/src/project/vcs.ts:

const patch = (file: string, before: string, after: string) =>
  formatPatch(structuredPatch(file, file, before, after, "", "", { context: Number.MAX_SAFE_INTEGER }))

And from packages/app/src/pages/session.tsx:

const wantsReview = createMemo(() =>
  isDesktop()
    ? desktopFileTreeOpen() || (desktopReviewOpen() && activeTab() === "review")
    : store.mobileTab === "changes",
)

That means on the desktop-layout web UI, simply having the file tree open appears to be enough to enable diff/review behavior.

Plugins

No response

OpenCode version

1.14.22

Steps to reproduce

1. Open OpenCode in a desktop browser against a top-level workspace that contains multiple nested git repos/worktrees.
2. Use the normal session page in the web UI.
3. Keep the file tree open in the desktop layout.
4. Allow the session UI to load/refresh.
5. OpenCode starts issuing GET /vcs/diff requests.
6. On large enough workspaces, memory usage spikes and OpenCode crashes with OOM.

My workspace shape is roughly:

• top-level project root
• multiple nested repos/worktrees underneath for different agents, including active worktrees and nested git roots

This seems important because vcsDiff appears to assume a simpler VCS layout than what an umbrella workspace provides.

Proposed fix

I think there are a few possible fixes, and probably more than one is warranted:

1. Do not use unbounded patch context in /vcs/diff

   • Replace Number.MAX_SAFE_INTEGER with a bounded context size.
   • This alone may dramatically reduce memory use.

2. Avoid auto-triggering /vcs/diff just because the file tree is open

   • The desktop-layout web UI should not implicitly enable diff/review behavior unless the user actually opens the review UI or explicitly requests diff state.

3. Detect and handle nested git repos/worktrees safely

   • Scope diff generation to the active repo only
   • or cheaply short-circuit when nested repo layouts are detected
   • or return a degraded response instead of trying to diff the whole umbrella workspace

4. Prevent overlapping/redundant /vcs/diff requests

   • The logs show repeated in-flight diff requests.
   • Debouncing, deduping, or canceling stale diff requests would likely help.

5. Cap total diff output

   • Limit number of files
   • limit total bytes
   • or stop diff generation once a memory-safe threshold is exceeded

Screenshot and/or share link

I uploaded heap snapshots separately, but the strongest evidence here is the route-level log correlation plus the current source code.

Representative log sequence:

• GET /vcs/diff starts
• heap warnings begin
• Out of memory failed
• the same /vcs/diff request finally completes after a long duration

Example from logs:

• /vcs/diff starts at 17:54:12
• heap warnings at 17:54:19 and 17:54:24
• Out of memory failed at 17:55:42
• the same /vcs/diff completes at 17:55:42

Operating System

Ubuntu 22.04.5 LTS

Terminal

Web UI for front end, Gnome Terminal / tmux 3.2a for CLI