fix(installtxn): put back an install a killed commit left behind - #997
fix(installtxn): put back an install a killed commit left behind#997beardthelion wants to merge 2 commits into
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CommitDir publishes by two renames: the live target moves into a workspace backup, then the staged copy is renamed into place. Neither is journaled, so a process killed between them left the target absent with the install's only copy retained in a workspace nothing ever read. plugins.Load and skills.Load enumerate directories, so the extension simply disappeared, while the lockfile went on listing it. Recovering needed one fact the transaction never wrote down: which install a backup belonged to. CommitDir now records that before it moves anything, and Recover puts the backup back when the target is absent. Recovery is a second data-loss surface, so it is bounded on every side. It refuses a name that is not a single element inside the install root, never replaces a live target, identifies a workspace by the name StageDir gives one rather than by contents alone, and leaves intact anything it cannot attribute. Every path that takes the install lock recovers, not just the two that install. Recovering on the install path alone is worse than not recovering: a removal takes the not-present branch, drops the lockfile entry and reports success while the backup it never looked at stays on disk, and the next install republishes it, reinstating an extension the user deleted. Removal and the terminalpet install hold the same lock and now do the same thing first. Recovery stays an explicit call rather than a side effect of Lock, matching how the other staged-swap transactions here invoke their repair pass and keeping a filesystem mutation visible at the sites that cause it.
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Included review availability: 4 reviews are currently available. Your included PR review attempts over the past 7 days set your current allowance at 5 reviews per hour. WalkthroughTransaction commits now record their target names. ChangesInstallation transaction recovery
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR restores interrupted installs during subsequent lock-holder operations without any supplied evidence of an unresolved merge-blocking issue; it is merge-ready after normal checks and review. Sequence Diagram(s)sequenceDiagram
participant Installer as Plugin, skill, or terminal pet installer
participant Lock as Directory lock
participant Recover as installtxn.Recover
participant Filesystem
Installer->>Lock: acquire installation lock
Installer->>Recover: recover abandoned transaction workspaces
Recover->>Filesystem: validate target metadata and retained backup
Recover->>Filesystem: restore backup when target is absent
Recover->>Filesystem: retire backup when target exists
Installer->>Filesystem: continue installation or removal
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Full details: Linked Issues checkExplanation The changes satisfy issue ✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@internal/installtxn/installtxn.go`:
- Around line 152-153: Update the existing-target branch in the install
transaction recovery flow to retire the matching backup and clean its workspace
before continuing, so recovery cannot later restore a stale extension after the
target is removed. Preserve the existing behavior when the target does not
exist, and add a regression test covering recover, remove, then recover.
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📒 Files selected for processing (7)
internal/installtxn/installtxn.gointernal/installtxn/installtxn_test.gointernal/plugins/install.gointernal/plugins/install_test.gointernal/skills/install.gointernal/skills/install_test.gointernal/terminalpet/client.go
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I found an issue that needs to be addressed before this is ready.
Findings
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[P1] Retire a backup once its update has already reached the live target
internal/installtxn/installtxn.go:151
The recovery record currently identifies which target a backup belongs to, but not whether the staged replacement ever became live. That leaves a second crash window: an update can die afterstagedhas been renamed intotargetbut beforepreviousand its workspace are removed. On the next locked operation,Recoversees the live target and skips the workspace, preserving its marked old backup. A subsequent plugin or skill removal then deletes the live target and its lockfile entry, but not that skipped backup; the next install sees the target absent and restores the old tree. The removed extension is therefore loadable again without a lockfile entry.Address the root cause by making recovery distinguish a backup from an interrupted pre-publish swap from one superseded by a successfully published target. For example, record/advance a transaction phase atomically enough for recovery to retire a superseded backup, or make the target-present recovery branch safely retire only a fully attributable backup. Preserve the existing conservative behavior for malformed/unattributable workspaces and the legitimate first-rename interruption where the target is genuinely absent; do not overwrite a live target. Please add regression coverage for: update → interruption after the second rename → remove → later install/recovery, for both plugin and skill paths.
Recover skipped any workspace whose target was occupied, which left the backup of a commit that was killed after its publish rename but before its cleanup. Removing that install then deleted the live target and its lockfile entry but not the skipped backup, and the next recovery read the absent target as an interrupted swap and published the stale tree again. plugins.Load and skills.Load enumerate directories, so the removed extension was loadable again with nothing in the lockfile naming it. The target already records how far the commit got, so recovery reads it as the phase rather than carrying a phase file. Absent means the swap never finished and the backup is put back as before. Present means the publish rename committed, so the backup beside it is superseded and its workspace is retired. The live install is never replaced or removed either way, and the guards that skip a workspace with no backup, an unreadable or missing marker, or a recorded name that is not a single element inside the install root are unchanged. The retire path removes the workspace directly rather than through cleanupWorkspace, which refuses one holding a previous precisely because it cannot tell a superseded backup from one still owed a restore. Reading the target that way is only safe once nothing can leave a partial tree there. rollback deleted the failed install in place before restoring, so a process killed partway through that delete left a husk at the target while the backup was still the only complete copy, and recovery would have taken the husk for a committed publish and deleted the last good tree. The renames are now ordered so the target is never partial: the failed install moves aside into the workspace, the backup moves back to the target, and only then is the set aside tree removed. A first install has no backup to protect and recorded no target, so it still deletes in place. The move aside can fail too, and then the failed install stays live at the target with the backup still the only copy of what it replaced. Rollback drops the workspace marker on that path, which leaves a workspace nothing can attribute, and recovery already leaves those alone.
Fixed in 3fe120e. Reproduced before changing anything: plant a commit that completed The fix takes the phase option without adding a phase file, because the target already records how far the commit got. Absent means the swap never finished, so the backup is put back as before. Present means the publish rename committed, so the backup beside it is superseded and its workspace is retired. The live install is never replaced or removed on either branch, and the conservative guards are untouched: no Reading the target that way is only safe once nothing else can leave a partial tree there, so two rollback changes landed with it.
That move aside can fail too, on Windows with a handle open under the target or on a permission problem on the install root, and then the failed install stays live at the target with the backup still the only copy of what it replaced. Recovery would read that as a committed publish and retire it, which is the one state where the new branch would destroy a tree nothing superseded. Rollback now drops the workspace marker on that path, handing it to the guard that already leaves unattributable workspaces alone. Coverage, each observed red before the fix and green after:
The PR body is updated too: the third known residual described this exact deferral, and the note that the live target check could not be falsified on Linux is no longer true. |
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I found issues that need to be addressed before this is ready.
Overall guidance
These findings share one root cause rather than representing unrelated follow-up work: recovery currently infers three different facts from incidental filesystem shape. Target existence is used as the transaction phase, a public directory prefix plus ordinary filenames is used as workspace ownership, and a void best-effort call is used for both “nothing attributable to recover” and “recognized recovery failed.” Those inferences are individually plausible, but together they leave callers unable to distinguish a fully committed update from an interrupted one, an owned journal from valid user content, or successful recovery from an operational failure. Fixing each symptom locally is likely to open another crash window.
Please close this as one recovery protocol with explicit invariants:
- Commit state must cover both halves of the transaction. For plugin and skill updates, “committed” means the replacement tree and its lockfile source/hash agree, not merely that
staged -> targetcompleted. Recovery needs enough durable information—or caller-specific reconciliation—to distinguish the pre-publish, tree-published/metadata-pending, and fully published states. A phase bit written only afterpublish()is not automatically sufficient, because a kill after the lockfile replacement but before that bit is durable creates the inverse ambiguity; the ordering has to make every crash point recoverable. - Workspace ownership must be exclusive before destructive action. Do not recursively delete or move a directory solely because its name has the temp prefix and it contains
previousandtarget. Either reserve that namespace consistently across installation and discovery, including existing user-authored skills, or add ownership/version evidence and validation that ordinary supported content cannot accidentally satisfy. Malformed, legacy, and unattributable directories should remain untouched. - Recovery outcomes must be observable by lock holders. Distinguish “skipped because it is not an attributable transaction” from “recognized transaction repaired/retired” and “recognized transaction could not be repaired/retired.” The last case must stop callers before they inspect the target, change the lockfile, install over it, or report a successful removal.
To avoid another review round, exercise the protocol as a state-transition matrix rather than adding only happy-path tests. For an update with an old target and old lock entry, inject interruption after the marker write, after target -> previous, after staged -> target but before/during lockfile publication, and after lockfile publication but before cleanup. From each state, run the next install and remove entry points and then a second recovery pass; assert tree contents, lock source/hash, loadability, workspace retention/cleanup, and removal finality. Also inject failures in both previous -> target and workspace retirement, and cover valid prefix-colliding skill content alongside malformed/unattributable workspaces. This remains bounded to the replacement-recovery behavior claimed by this PR; it does not require fixing the disclosed pre-existing first-install or interrupted-RemoveDir residuals.
Findings
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[P1] Do not infer lockfile publication from target presence
internal/installtxn/installtxn.go:162
CommitDirrenamesstagedintotargetat line 72 and only then invokespublish, which is where plugin and skill installs atomically replace their lockfiles. A killed forced update can therefore leave this exact state:targetcontains the replacement from source B,previouscontains the last committed tree from source A, and the lockfile still records source A and its hash. On the next locked operation, this branch sees only thattargetexists and recursively deletes the workspace, permanently discarding the tree that actually matches the recorded metadata. The replacement remains executable/discoverable while clash checks,info, hash-drift reporting, and later update decisions consume stale provenance. The base behavior already had the tree/lockfile crash gap, but this PR worsens it by destroying the retained recovery evidence. The root cause is that “directory publish rename completed” is being treated as “the content-plus-lockfile transaction committed.” Reconcile both halves before retiringprevious; preserve the newly fixed target-absent restoration, live-target non-overwrite, and post-commit stale-backup retirement rather than reverting to keeping every target-present backup. -
[P1] Stop removals when an attributable recovery fails
internal/installtxn/installtxn.go:166
Once a workspace has passed the prefix, backup, marker, and target-name checks, a failed rename or retirement is an operational recovery failure, not the same condition as an unattributable legacy workspace. Today both are silent because restore andRemoveAllerrors are discarded andRecoverhas no result. A concrete sequence is: an interrupted update leavestargetabsent andpreviousattributable;previous -> targetfails transiently because the workspace is non-writable or blocked by a Windows sharing handle;plugins.Remove/skills.Removecontinues, sees only the old lock entry, deletes it, and returns success; after the obstruction clears, a later recovery restoresprevious, making the supposedly removed extension loadable with no lock entry. Target-present retirement failure creates the symmetric risk because Remove can delete the live target while the stale backup remains recoverable. The root cause is that callers cannot tell “safe to proceed” from “recognized transaction is unresolved.” Return an actionable result/error for failures after attribution and make all relevant lock holders stop before reading or mutating installation state; keep conservative non-errors for malformed, legacy, or unowned directories that recovery deliberately skips. -
[P2] Keep valid skill directories out of the workspace namespace
internal/installtxn/installtxn.go:137
The comment says the dot-prefixed workspace cannot be mistaken for an installed skill, but that is not an enforced contract:validSkillNameaccepts names such as.zero-install-txn-notes, and the loader enumerates dot-prefixed directories in the primary skills root. If a valid user-authored skill directory also contains aprevious/directory and a regulartargetfile naming one path component, it satisfies every ownership check here. Recovery then either recursively deletes the whole skill when the named target exists, or moves itspreviouscontent elsewhere and deletes the rest when the target is absent. This requires an unusual shape, hence P2, but the consequence is deletion of supported user content. The root cause is using a non-reserved public namespace and ordinary content names as proof that Zero created the directory. Make the namespace and ownership rule consistent acrossStageDir, skill installation/name validation, discovery of existing user-authored skills, and recovery. If compatibility prevents reserving the prefix outright, strengthen the transaction record and refuse destructive action on ambiguous pre-existing directories; do not merely tightenvalidSkillName, because that would not protect already present or manually authored skills.
2 participants
Fixes #996.
CommitDirpublishes by two renames: the live target moves into the transaction workspace asprevious, then the staged copy is renamed into place. Neither is journaled, so a process killedbetween them left the target absent with the install's only copy retained in a workspace nothing
ever read.
plugins.Loadandskills.Loadenumerate directories, so the extension disappearedwhile the lockfile went on listing it.
Recovery needed one fact the transaction never wrote down: which install a backup belonged to.
CommitDirnow records that before it moves anything, andRecoverputs the backup back when thetarget is absent.
Recovery is bounded on every side, because it is a second data-loss surface. It refuses a
recorded name that is not a single path element inside the install root, never replaces a live
target, identifies a workspace by the name
StageDirgives one rather than by contents alone, andleaves intact anything it cannot attribute.
Every path that takes the install lock recovers, not just the two that install. This is the
part worth reviewing closely. Recovering on the install path alone is worse than not recovering at
all:
Removetakes its not-present branch, drops the lockfile entry and reports success while thebackup it never looked at stays on disk, and the next install republishes it, reinstating an
extension the user deleted. Both
Removepaths and theinternal/terminalpetinstall hold thesame lock and now do the same thing first.
Recovery stays an explicit call rather than a side effect of
Lock. That matches how the otherstaged-swap transactions in this repo invoke their repair pass, and it keeps a filesystem mutation
visible at the sites that cause it. Binding it to lock acquisition would cover all five callers for
free, but an acquire function that mutates the filesystem is a surprising contract, and this
repository has no precedent for it.
Behavior change
An interrupted install is now put back the next time anything takes that install root's lock,
rather than staying lost. A workspace left by a version before this change carries no recorded
target, so
Recoverskips it and it is left in place rather than reclaimed.The target is also what records how far a commit got, so recovery reads it as the transaction
phase. A target that is absent means the swap never finished and the backup is put back. A target
that is there means the publish rename committed, so the backup beside it is superseded and its
workspace is retired instead of being kept for a later pass. Keeping it was what let a removal be
undone by accident: the removal deleted the live target, and the next recovery then read the absent
target as an interrupted swap and published the stale tree again. Reading the target that way also
required
rollbackto stop deleting a failed install in place, since a kill partway through thatdelete would leave a husk recovery could mistake for a committed publish.
Verification
Each defect was reproduced first, with a passing control, then each guard was ablated individually
and confirmed to fail without it:
publishcallback fails.Recoverfromplugins.Installor fromskills.Install, and that package's recovery testfails while the other stays green.
Recoverfromplugins.Remove, and the removal test fails with the removed plugin back ondisk and loadable again.
to contain the same two entries.
One guard could not be made to fail and is called out rather than claimed: the backup-presence
check is an early-out that the following rename already catches. The live-target branch is now
falsifiable, since removing it resurrects a removed extension in both caller packages. What still
cannot be falsified is the narrower claim that a backup never replaces a live target: Go's
os.RenamereturnsEEXISTon Linux even for an empty destination directory. POSIX permitsreplacing an empty one, so that assertion pins the contract rather than one platform's syscall.
gofmt,go vet,go test ./... -race,zero-release buildandzero-release smokeare clean onlinux/arm64, with the four affected packages repeated at
-count=3. Cross-compiled forwindows/amd64 and darwin/arm64. macOS and Windows are otherwise untested locally and rest on CI;
the change is directory renames, which is where Windows differs most.
Known residuals
RemoveDirwrites no marker, so its workspace stays unattributable and is skipped.That window predates this change and is unaffected by it.
through the install path, since recovery runs under the lock before every commit, and a workspace
it does not restore from is skipped intact rather than deleted.
copy survives as a workspace nothing can attribute. Recovery leaves it alone forever. That is
litter rather than a hazard: an unattributable workspace is never published from.
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