fix: clear tool output and attachments when pruning to prevent memory leak by hendem · Pull Request #7049 · anomalyco/opencode · GitHub

Summary

Clear tool output and attachments when compaction prunes old tool results, actually freeing memory instead of just flagging.

Evidence

In a real session working on this repo:

Metric	Value
OpenCode process RAM	16.4 GB
Tool parts on disk	34,887 files
Session duration	~3 hours

Sample tool output sizes from this session:

webfetch of docs page: 10 KB
read of source file: 5-50 KB
git diff / gh pr diff: 10-100 KB
bash command outputs: 1-50 KB

All of these outputs stay in memory even after compaction marks them "old".

The Problem

In SessionCompaction.prune(), when tool outputs are pruned:

// BEFORE: Only sets a flag, output data stays in memory
part.state.time.compacted = Date.now()
await Session.updatePart(part)

The compacted timestamp is used by toModelMessage() to replace output with placeholder text like "(Old tool result content cleared)" - but the actual data never gets freed.

Over a long session:

34,887 tool calls × average output size = hundreds of MB to GBs retained
Memory never decreases, even after compaction runs
Eventually Bun runs out of memory and crashes

The Fix

// AFTER: Actually clear the data
part.state.time.compacted = Date.now()
part.state.output = ""              // Free the output string
part.state.attachments = undefined  // Free any attachments
await Session.updatePart(part)

Now when compaction runs, the memory is actually freed. The placeholder text is already shown to the LLM (that logic exists), we just were not clearing the source data.

Testing

Existing compaction tests pass. Added test verifying output/attachments are cleared after prune.

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

Pull request overview

This PR fixes a memory leak where compacted tool outputs and their attachments were retained indefinitely in storage. When the pruning mechanism marks old tool outputs as compacted, the fix now clears both the output string and attachments array to free memory.

Key changes:

Clears tool output and attachments during compaction to prevent unbounded memory growth
Adds comprehensive test coverage for the pruning behavior

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
packages/opencode/src/session/compaction.ts	Sets output to empty string and attachments to undefined when marking tool parts as compacted, with explanatory comment
packages/opencode/test/session/compaction.test.ts	Adds two new test cases: one verifying output/attachments are cleared during pruning, and one testing that pruning respects the disabled configuration

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Addressed review comment about test not verifying behavior when pruning is disabled (commit 488173440).

The test now:

Creates a tool part with large output (200,000 chars) and an attachment (similar to the first test)
Creates additional user messages to get past turn protection
Calls prune() with pruning disabled via config
Verifies that:
- output.length remains 200,000 (unchanged)
- attachments.length remains 1 (unchanged)
- time.compacted is undefined (not set)

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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this would be really helpful

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

Open an issue describing the bug/feature (if one doesn't exist)
Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

… leak When compaction prunes old tool outputs, only the compacted timestamp was being set - the actual output string and attachments array remained in storage indefinitely. This caused storage files to grow unbounded with large tool outputs (file contents, base64 images/PDFs, etc.). Now prune() clears both output and attachments when marking parts as compacted. The toModelMessage function already replaces compacted outputs with placeholder text, so this is safe. Fixes part of anomalyco#4315

…s to pruning disabled test

This reverts commit b302472.

Server Mode Diagnostic Data

Running OpenCode v1.1.23 as a systemd daemon (opencode serve) on a 64GB Linux server. Here is data that may help with this PR.

Memory Growth (from systemd logs)

Runtime	Memory Peak	Swap
2.5h	263 MB	0
4.5h	699 MB	0
4.75h	56 GB	8.8 GB
2.25h	20.9 GB	0

Memory grows over time and eventually causes the process to become unresponsive.

Storage Accumulation

storage/part/     141MB (10,820 directories)
storage/message/   19MB (728 directories)
tool-output/       21MB (15 files)

The 10,820 part directories correlate with the unfree-d tool outputs described in this PR.

Timeout Pattern

When memory gets high, HTTP requests to /session/{id}/message stop responding. Downstream clients see 10-minute timeouts:

17:22:29 WARN Retry attempt=2 session=ses_xxx
17:32:30 WARN Retry attempt=3 (10 min gap = timeout)
17:42:31 ERROR elapsed_secs=1801 Failed after retries

Environment

OpenCode v1.1.23, server mode (opencode serve --port 4096)
Ubuntu Linux, systemd service
Multiple concurrent sessions over extended periods
Heavy tool usage (grep, read, bash)

Happy to provide more data if useful.

can the PR be reviewed along with this one, it was fixing similar issues from a different persepctive: #14650

Tier 1 bug fixes: - Fix O(n²) bash output concatenation with StreamingOutput class (anomalyco#9693) - Fix memory leaks in Bus.once, Format, Plugin, ShareNext, Bootstrap (anomalyco#13514) - Fix FileTime race condition using actual file mtime instead of JS clock - Free memory on compaction prune: clear output/attachments/metadata (anomalyco#7049) - Throttle reasoning-delta storage writes to 50ms intervals (anomalyco#11328) - Handle SIGHUP/SIGTERM to prevent orphaned processes (anomalyco#12718) - Add process.once("close") handler for bash tool reliability Tier 2 features: - Support 1M context window for Anthropic models via beta header (anomalyco#14375) - Input-only token counting for compaction with limit.input models - MCP lazy loading: on-demand tool discovery via mcp_search tool (anomalyco#8771) - MCP servers listed in system prompt when lazy mode enabled - StreamingOutput: output_filter regex for build diagnostics - LSP server cleanup callback for temp directory removal - Extract formatSize utility from uninstall to shared util/format - GitHub CI: fix Bus subscription leak in session event handler Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Addresses the remaining memory leaks identified in anomalyco#16697 by consolidating the best fixes from 23+ open community PRs into a single coherent changeset. Fixes consolidated from PRs: anomalyco#16695, anomalyco#16346, anomalyco#14650, anomalyco#15646, anomalyco#13186, anomalyco#10392, anomalyco#7914, anomalyco#9145, anomalyco#9146, anomalyco#7049, anomalyco#16616, anomalyco#16241 - Plugin subscriber stacking: unsub before re-subscribing in init() - Subagent deallocation: Session.remove() after task completion - SSE stream cleanup: centralized cleanup with done guard (3 endpoints) - Compaction data trimming: clear output/attachments on prune - Process exit cleanup: Instance.disposeAll() with 5s timeout - Serve cmd: graceful shutdown instead of blocking forever - Bash tool: ring buffer with 10MB cap instead of O(n²) concat - LSP index teardown: clear clients/broken/spawning on dispose - LSP open-files cap: evict oldest when >1000 tracked files - Format subscription: store and cleanup unsub handle - Permission/Question clearSession: reject pending on session delete - Session.remove() cleanup chain: FileTime, Permission, Question - ShareNext subscription cleanup: store unsub handles, cleanup on dispose - OAuth transport: close existing before replacing Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Closing this pull request because it has had no updates for more than 60 days. If you plan to continue working on it, feel free to reopen or open a new PR.

Copilot AI review requested due to automatic review settings January 6, 2026 05:49

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hendem mentioned this pull request Jan 7, 2026

fix: clean up pending permissions when session is deleted #7154

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github-actions Bot mentioned this pull request Jan 7, 2026

feat: implement smart pruning #7215

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hendem requested a review from Copilot January 7, 2026 15:45

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github-actions Bot added the needs:issue label Jan 9, 2026

github-actions Bot removed the needs:issue label Jan 9, 2026

hendem mentioned this pull request Jan 9, 2026

fix: force kill MCP server processes on dispose to prevent orphan processes #7424

Closed

fwang force-pushed the dev branch from 4da2998 to a618fbe Compare January 9, 2026 06:32

fwang requested a review from adamdotdevin as a code owner January 9, 2026 06:32

Mark Henderson and others added 7 commits January 10, 2026 14:14

address PR review comments: remove unused variables and add assertion…

718df08

…s to pruning disabled test

wip: zen

b302472

Revert "wip: zen"

1b3aec7

This reverts commit b302472.

wip: black

62d4b51

wip: black

d6fca76

chore: generate

141c413

fwang force-pushed the fix/memory-leak-compaction-cleanup branch from 9d089b6 to 141c413 Compare January 10, 2026 19:15

hendem added 2 commits January 11, 2026 00:51

Merge branch 'dev' into fix/memory-leak-compaction-cleanup

9f0287b

Merge branch 'dev' into fix/memory-leak-compaction-cleanup

4cbc49a

github-actions Bot mentioned this pull request Jan 16, 2026

feat(bash): stream large output to tmpfile with filtering and GC #8953

Closed

github-actions Bot mentioned this pull request Jan 20, 2026

fix: Prevent O(n²) memory usage in command output #9693

Closed

thdxr force-pushed the dev branch from cbab81f to 2d3c7a0 Compare January 30, 2026 04:50

opencode-agent Bot force-pushed the dev branch from 00637c0 to 71e0ba2 Compare January 30, 2026 14:32

thdxr force-pushed the dev branch 3 times, most recently from f1ae801 to 08fa7f7 Compare January 30, 2026 14:37

github-actions Bot mentioned this pull request Feb 13, 2026

fix: resolve multiple memory leaks causing unbounded RAM growth ( Now passing: && Fixed failing tests for windows ) #13514

Closed

github-actions Bot mentioned this pull request Feb 22, 2026

fix(core): clear tool output and attachments on compaction prune #14693

Closed

6 tasks

github-actions Bot mentioned this pull request Feb 28, 2026

fix: consolidate memory leak fixes from #14650 and #8953 #15435

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6 tasks

guazi04 mentioned this pull request Mar 5, 2026

[FEATURE]: Session Lifecycle Management — unified storage reclamation, auto-archival, and child session cleanup #16101

Open

1 task

github-actions Bot mentioned this pull request Mar 5, 2026

fix: clear tool output and attachments during compaction prune #16162

Closed

binarydoubling mentioned this pull request Mar 9, 2026

Multiple memory leaks cause unbounded RAM growth during extended TUI usage #16697

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github-actions Bot mentioned this pull request Mar 9, 2026

fix(session): clear compacted tool output #16785

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6 tasks

binarydoubling mentioned this pull request Mar 9, 2026

fix: resolve multiple memory leaks causing unbounded growth #16695

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6 tasks

github-actions Bot mentioned this pull request Apr 7, 2026

fix: bash tool memory leak #21321

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3 tasks

opencode-agent Bot force-pushed the dev branch from 2f2ed11 to 9f201d6 Compare April 16, 2026 21:55

github-actions Bot closed this Apr 25, 2026

fix: clear tool output and attachments when pruning to prevent memory leak by hendem · Pull Request #7049 · anomalyco/opencode · GitHub

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fix: clear tool output and attachments when pruning to prevent memory leak - #7049

fix: clear tool output and attachments when pruning to prevent memory leak#7049
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fix: clear tool output and attachments when pruning to prevent memory leak by hendem · Pull Request #7049 · anomalyco/opencode · GitHub

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fix: clear tool output and attachments when pruning to prevent memory leak - #7049

fix: clear tool output and attachments when pruning to prevent memory leak#7049hendem wants to merge 9 commits intoanomalyco:devanomalyco/opencode:devfrom hendem:fix/memory-leak-compaction-cleanuphendem/opencode:fix/memory-leak-compaction-cleanupCopy head branch name to clipboard

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Summary

Evidence

The Problem

The Fix

Testing

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Pull request overview

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Pull request overview

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Th0rgal commented Jan 17, 2026

Server Mode Diagnostic Data

Memory Growth (from systemd logs)

Storage Accumulation

Timeout Pattern

Environment

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fix: clear tool output and attachments when pruning to prevent memory leak#7049
hendem wants to merge 9 commits into
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hendem:fix/memory-leak-compaction-cleanup

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