Large file tracked by opencode git tool causes OOM

[elijahmorg]

Description

I had a very large file (+200MB) sucked into my opencode session.

Then I ran multiple sub agents that somehow also pulled it into their sessions causing a ballooning memory issue.

The file was technically json, but wasn't something that opencode touched or modified. It was generated by a tool and I was deleting it.

Doing some digging and it appears that the file was sucked in by Snapshot.diffFull

Tangentially related to this is that all sub-agent sessions are fully loaded into a main session when you reload. So when I close and reload my session it immediately balloons back up even tho most of the large diff elements are residing in the sub-agent sessions.

Plugins

None

OpenCode version

issue exists on dev branch

Steps to reproduce

1. have a large text blob (you can generate one by doing export heap snapshot in opencode)
2. send one message
3. delete large text blob
4. see memory footprint increase
5. can also do the same thing with sub agents too multiply the issue

Screenshot and/or share link

No response

Operating System

macOS

Terminal

iterm2

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Session snapshots cause extreme memory usage (w/ repro script) #17226: Same root cause — Snapshot.diffFull() loading full file bodies into memory, causing extreme memory usage with large generated files. Also covers session reload behavior that re-materializes large diff data.
• Bug Report: Desktop Application Crashes with Out of Memory When Attaching Large Files (>500 MiB) #15846: OOM crash when attaching large files (>500 MiB).
• Massive memory use on opening opencode when there is a very large file #2585: Massive memory use when opencode encounters a very large file in the workspace.

Please review these issues and consider whether your report adds new information not already covered.

[elijahmorg]

1. issue is that there is no size check before the diff is saved into the session (a 250MB 1 line file seems like something that should never get sucked in)
2. each sub-agent did the same thing and this like 10x'ed the issue
3. when reloading each sub-agent session is fully loaded into the solid-store

I should note that I confirmed this issue by exporting the sessions and inspecting them.

I also played around with a fix that seems to resolve the issue (check file size before reading it).

[thdxr]

This should be fixed by commit 0a80ef4 which adds a 2MB file size limit for snapshotting. Files over 2MB are now excluded from git snapshots.