rdmbair15m5-changelog-20260915-2154-tyrell-worktree-engine-defect-resolution

Resolved Tyrell Worktree Engine empty OID defect (ISSUE-20260915-09) and hardened ProcessRunner pipe drain under concurrency.

Scope

• Hosts: rdmbair15m5, rdmsm4x
• Projects: apps/Tyrell, lib/ECSProcess
• Ticket: ISSUE-20260915-09

Files Touched

1. apps/Tyrell/Sources/TyrellCore/Worktree/WorktreeModels.swift:
   • Added case emptyCommitGenerated to enum WorktreeError.
   • Added case .emptyCommitGenerated: return "git commit-tree returned an empty commit OID." to errorDescription.
2. apps/Tyrell/Sources/TyrellCore/Worktree/ECSWorktreeManager.swift:
   • In captureCheckpoint(), added: guard !commitOID.isEmpty else { throw WorktreeError.emptyCommitGenerated }.
3. lib/ECSProcess/Sources/ECSProcess/ProcessRunner.swift:
   • Hardened drainNonBlocking(fileHandle:) to retry when read() returns -1 and errno == EINTR.
   • Added bounded poll(&pfd, 1, 50) when read() encounters EAGAIN/EWOULDBLOCK to guarantee all trailing child pipe output is captured.
   • Hardened PipeReadGate.readAvailable(from:) to retry on EINTR.
   • Closed parent's pipe write handles (stdoutPipe.fileHandleForWriting and stderrPipe.fileHandleForWriting) immediately after process.run(), ensuring child is the sole writer and true EOF is reached upon child exit.
4. apps/Tyrell/Tests/TyrellCoreTests/WorktreeEngineTests.swift:
   • Added testParallelCheckpointStress50Iterations() running 50 concurrent checkpoint captures via withThrowingTaskGroup.

Git Commits

• lib/ECSProcess: commit 19d19d6 on canonical main (rdmsm4x:~/dev/lib/ECSProcess and rdmbair15m5:~/dev/lib/ECSProcess)
• apps/Tyrell: commit 67b55b9 on isolated worktree agy/tyrell-issue-20260915-09-worktree-engine (rdmsm4x:~/dev/_worktrees/tyrell-issue-20260915-09-worktree-engine)

Verification Evidence

1. lib/ECSProcess:
   • swift test on rdmbair15m5: 24/24 tests passed (0 failures).
   • swift test on rdmsm4x: 24/24 tests passed (0 failures).
2. apps/Tyrell:
   • swift test --filter WorktreeEngineTests on rdmbair15m5: 12/12 tests passed (including testParallelCheckpointStress50Iterations in 2.175s).
   • swift test --filter WorktreeEngineTests on rdmsm4x: 12/12 tests passed (including testParallelCheckpointStress50Iterations in 1.465s and 0.657s).
3. Swift 6 strict concurrency:
   • Compiled with 0 warnings / 0 errors on modified source files.
4. Ticket resolution:
   • ISSUE-20260915-09 resolved on canonical rdmsm4x ticket registry.

Rollback & Undo

• Revert commit 19d19d6 in lib/ECSProcess.
• Remove worktree ~/dev/_worktrees/tyrell-issue-20260915-09-worktree-engine or delete branch agy/tyrell-issue-20260915-09-worktree-engine.

Outstanding Actions

• None.