[magma-beef]

Summary

Port of #143 (release/v2) to the v1 line: the post step runs fstrim on the buildkit sticky disk before unmounting and committing it, so freed blocks are discarded from the backing image.

• The agent sends the trim budget in GetStickyDiskResponse.fstrim_timeout_secs and the minimum free extent in fstrim_min_extent_bytes (bumped @buf/blacksmith_vm-agent.bufbuild_es); setup stores both in action state. A 0/absent budget disables the trim; a 0/absent minimum keeps fstrim's default.
• Post trims only when the budget is positive and the run is still on track to commit (expose id, integrity check passed, no early deny, no SIGKILL, no failed previous steps), after buildkitd shutdown and sync, before the usage sample and umount.
• Best-effort timeout <budget> sudo fstrim -v [-m <bytes>]: a missing binary, unsupported discard, or timeout is logged and never fails the step. v1 has no DockerJobLifecycle report, so the result is log-only.

Prod impact: none at merge. The trim runs only when the agent sends a positive fstrim_timeout_secs, and v1 users pick it up with the next v1 release/tag.

Start here: src/main.ts (post step, trimFilesystem), then src/setup_builder.ts (parseFstrimTimeoutSecs, parseFstrimMinExtentBytes, fstrimFailureOutcome) and src/state-helper.ts. dist/ is regenerated.

Checks: pnpm lint, pnpm typecheck, pnpm test, pnpm build.

Link to Devin session: https://app.devin.ai/sessions/2b54a64701834e1ca263ab9a9e881691
Open in Devin Desktop: https://app.devin.ai/desktop/session/2b54a64701834e1ca263ab9a9e881691?variant=devin
Requested by: @magma-beef

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^{Open in [code]smith · Need help on this PR? Tag @codesmith-bot with what you need. (Staging)}

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🟢 Devin Review found nothing to fix · View findings · Follow Devin's work

[devin-ai-integration]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[blacksmith-staging]

Post step trims the buildkit disk before unmount

After the PR the post step runs fstrim between the integrity check and the usage sample/umount, and the freed 512 MiB is released from the backing image; before, it stays allocated. buildkitd was not running, so its shutdown step was a no-op.

_Merge-base

_{This PR 7eafd5e8}

Also checked · 4 match

Trim skipped when disabled or not committing
Trim failures never fail the step
Min extent passed as fstrim -m
Setup reads budget from agent response

_{Proof on 7eafd5e8 · mocked: Blacksmith VM agent (GetStickyDisk / Com... (unavailable), Buildkit sticky disk (/var/lib/buildkit) (unavailable) · Did Proof get it right? Yes · No}

View full Proof report

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