The implement run state has two same-uid hygiene gaps the security review of itd-2609221656373558 rated LOW and shipped past on the record: fsutil.AppendLineIn's openAppendIn (internal/fsutil/fsutil.go) opens the log leaf without the Lstat and symlink refusal its read twin ReadGuardedInRoot applies, so an in-root symlink leaf redirects every appended line (demonstrated: a log symlinked onto a claim file makes the claim unreadable); and readClaim (internal/core/implement/claim.go) checks a claim file's session and lane only for non-empty before they reach HeldError and the release refusal, printed to stderr unsanitised, so a hand-edited claim can put terminal escapes on the operator's screen. Remedy, each test-held: refuse a symlink leaf in openAppendIn as the read primitive does, and run validName on the claim's session and lane in readClaim treating failure as unreadable. Also: .lock is created 0644 beside 0600 run files (internal/fsutil/flock.go), and commands/implement.md does not say the release refusal rests on a cooperative, unauthenticated role. The next lane that extends internal/core/implement (the build verb, itd-2609201916151817) takes it.

The implement run state has two same-uid hygiene gaps the security review of itd-2609221656373558 rated LOW and shipped past on the record: fsutil.AppendLineIn's openAppendIn (internal/fsutil/fsutil.go) opens the log leaf without the Lstat and symlink refusal its read twin ReadGuardedInRoot applies, so an in-root symlink leaf redirects every appended line (demonstrated: a log symlinked onto a claim file makes the claim unreadable); and readClaim (internal/core/implement/claim.go) checks a claim file's session and lane only for non-empty before they reach HeldError and the release refusal, printed to stderr unsanitised, so a hand-edited claim can put terminal escapes on the operator's screen. Remedy, each test-held: refuse a symlink leaf in openAppendIn as the read primitive does, and run validName on the claim's session and lane in readClaim treating failure as unreadable. Also: .lock is created 0644 beside 0600 run files (internal/fsutil/flock.go), and commands/implement.md does not say the release refusal rests on a cooperative, unauthenticated role. The next lane that extends internal/core/implement (the build verb, itd-2609201916151817) takes it.

Grounds

• pursued: an in-root symlink leaf can no longer redirect an appended log line and a hand-edited claim can no longer put escapes on the operator's screen; a log append landing in a claim file, or an escape in a HeldError, would show it wrong.