Snapshot directory can grow to 40GB+ in 7 days due to hardcoded prune=7.days

[qimenluoshu-eng]

Description

Bug: Snapshot directory fills disk during git gc --prune=7.days (disk drops 40GB in 2 hours)

Description

The snapshot cleanup feature (git gc --prune=7.days) can cause massive disk space spikes that temporarily require 2x the final pack size, potentially filling the entire disk.

In my case: Available disk space dropped from 75GB to 35GB in about 2 hours, and I had to kill the git process to prevent complete disk exhaustion.

Steps to Reproduce

1. Use OpenCode for 7+ days with frequent file edits (each triggers git add .)
2. Allow the hourly git gc --prune=7.days task to run
3. Observe disk space rapidly depleting as Git creates a huge pack file

Root Cause Analysis

Based on logs in ~/.local/share/opencode/log/:

1. Every file edit triggers git add . - OpenCode tracks all changes in ~/.local/share/opencode/snapshot/global/
2. 7 days of changes accumulate - After 7 days, thousands of loose Git objects exist
3. When git gc runs:
   • Reads all loose objects
   • Writes a huge pack file (requires 2x temporary space because loose objects + new pack coexist)
   • Only deletes loose objects after pack is complete

The critical issue: If free space is less than the estimated pack size, the system can run out of disk mid-process.

Evidence

• Before gc: 75GB available
• During gc: Dropped to 35GB (40GB pack file being created)
• Had to kill git process to prevent complete disk fill
• Logs show two 2.1GB pack files and one 54MB pack were created

Related Issues

• Snapshot feature consumes 533GB+ of disk due to orphaned git temp files and unbounded growth #15977: Snapshot uses 533GB+ disk space
• Snapshot system leaks tmp_pack_* files indefinitely, filling disk at ~9.5 GB/hour #14811: tmp_pack_* files accumulate infinitely (~9.5 GB/hour)
• Old snapshot folders not deleted after the 7 day threshhold #10782: Old snapshot folders not deleted after 7 days

User Impact (Current Limitations)

Users currently have no control over:

• The prune interval (hardcoded 7 days)
• Disk space checking before gc
• Maximum pack file size
• Manual cleanup of old snapshots

Proposed Fixes

1. Add disk space check - Abort if free space < (estimated pack size + 10GB buffer)
2. Use --max-pack-size - Split large packs into e.g., 1GB chunks to reduce temporary space needs
3. Make prune interval configurable - Allow users to set 1-30 days via env var (e.g., OPENCODE_SNAPSHOT_DAYS)
4. Add monitoring/warning - Log warnings before space runs out; optionally notify user
5. Implement cleanup for old snapshots - Currently they're never deleted even after prune

Environment

• OS: macOS 12.6
• OpenCode version: 1.2.4
• Git version: 2.39.5
• Total disk: 234GB APFS

Plugins

No response

OpenCode version

OpenCode Desktop v1.2.25

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response

[github-actions]

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

• Snapshot system leaks tmp_pack_* files indefinitely, filling disk at ~9.5 GB/hour #14811: Snapshot system leaks tmp_pack_* files indefinitely, filling disk — same root cause (git gc leaving temp files, unbounded snapshot growth, no disk checks)
• Snapshot feature consumes 533GB+ of disk due to orphaned git temp files and unbounded growth #15977: Snapshot feature consumes 533GB+ of disk due to orphaned git temp files and unbounded growth — same core issue (closed, but closely related)
• Old snapshot folders not deleted after the 7 day threshhold #10782: Old snapshot folders not deleted after the 7 day threshold — related (prune not working as expected)
• Session snapshots cause extreme memory usage (w/ repro script) #17226: Session snapshots cause extreme memory usage — related snapshot resource management issue

Several of these (especially #14811) overlap significantly with the symptoms and root causes described here. You may want to add your findings as a comment on those issues instead, or confirm this is a distinct enough scenario to warrant a separate report.

[thdxr]

This should be partially addressed by commit 0a80ef4 which adds a 2MB file size limit for snapshotting. Large files are now excluded, reducing the rate of snapshot growth.