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+# ext-api Orphan `gzip-chunk-*.tmp` Cleanup Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add a Spring `ApplicationRunner` to `module-external-api` that deletes orphan `gzip-chunk-*.tmp` files older than 1h from `java.io.tmpdir` on boot.
+
+**Architecture:** Single `@Component` `OrphanTempFileCleanupHook` implements `ApplicationRunner`. `run(args)` delegates to `LogicExecutor.executeVoid(::cleanupOrphans, ctx)`. `cleanupOrphans()` walks `scanDir` (default `Paths.get(System.getProperty("java.io.tmpdir"))`), filters by regex `gzip-chunk-.*\.tmp`, deletes entries with `mtime < now - 1h`. Per-file `IOException` is logged + skipped (fail-soft). Final INFO summary log.
+
+**Tech Stack:** Kotlin, Spring Boot 3 `ApplicationRunner`, `LogicExecutor`, `java.nio.file`, JUnit 5, Mockito-Kotlin, `@TempDir`.
+
+**Spec:** `docs/superpowers/specs/2026-06-19-ext-api-orphan-tmp-cleanup-design.md`
+**Issue:** #1296
+
+---
+
+## File Structure
+
+| File | Responsibility |
+| ---- | -------------- |
+| `module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt` (CREATE) | `@Component` ApplicationRunner + cleanup logic |
+| `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt` (CREATE) | 5 unit tests via @TempDir + injected Clock |
+
+No existing files modified. Bean auto-discovered via `ExternalApiApplication.scanBasePackages = ["maple.externalapi", ...]`.
+
+---
+
+## Task 1: Scaffold test class + production shell (failing tests = no impl)
+
+**Files:**
+- Create: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+- Create: `module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt`
+
+- [ ] **Step 1: Create test class skeleton with one failing test**
+
+```kotlin
+package maple.externalapi.snapshot
+
+import maple.expectation.infrastructure.executor.LogicExecutor
+import maple.expectation.infrastructure.executor.TaskContext
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import org.mockito.kotlin.any
+import org.mockito.kotlin.doAnswer
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.verify
+import org.slf4j.LoggerFactory
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.attribute.FileTime
+import java.time.Clock
+import java.time.Instant
+import java.time.ZoneOffset
+import java.util.concurrent.Executor
+import kotlin.io.path.setLastModifiedTime
+
+class OrphanTempFileCleanupHookTest {
+
+    @TempDir
+    lateinit var tmp: Path
+
+    private val fixedNow: Instant = Instant.parse("2026-06-19T00:00:00Z")
+    private val clock: Clock = Clock.fixed(fixedNow, ZoneOffset.UTC)
+
+    // Stub LogicExecutor that invokes the Runnable passed to executeVoidJava synchronously.
+    // We use executeVoidJava (Runnable-typed) instead of executeVoid (ThrowingRunnable) so the
+    // mock signature and the production signature both round-trip via the same Runnable type.
+    private val executor: LogicExecutor = mock {
+        on { executeVoidJava(any<Runnable>(), any()) } doAnswer { invocation ->
+            (invocation.arguments[0] as Runnable).run()
+        }
+    }
+
+    // Default async executor: runs submitted Runnables synchronously on the caller thread.
+    // CompletableFuture.runAsync uses this to start cleanup; the future then completes
+    // synchronously. runWithDeadline's future.get(timeout) returns immediately.
+    private val syncAsyncExecutor: Executor = Executor { it.run() }
+
+    private val log = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java)
+
+    private fun makeHook(
+        clock: Clock = this.clock,
+        scanDir: Path = tmp,
+        executor: LogicExecutor = this.executor,
+        asyncExecutor: Executor = syncAsyncExecutor,
+        timeoutSeconds: Long = 30,
+    ): OrphanTempFileCleanupHook =
+        OrphanTempFileCleanupHook(executor, asyncExecutor, clock, scanDir, timeoutSeconds)
+
+    private fun createOrphan(
+        name: String,
+        size: Int = 10,
+        ageHours: Long = 0,
+    ): Path {
+        val file = tmp.resolve(name)
+        Files.write(file, ByteArray(size))
+        file.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(ageHours * 3600)))
+        return file
+    }
+
+    @Test
+    fun `deletes files older than 1 hour`() {
+        val file = createOrphan("gzip-chunk-uuid1-part-000001-.jsonl.gz.tmp", ageHours = 2)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isFalse
+    }
+}
+```
+
+- [ ] **Step 2: Create production shell that compiles but fails the test**
+
+```kotlin
+package maple.externalapi.snapshot
+
+import maple.expectation.infrastructure.executor.LogicExecutor
+import maple.expectation.infrastructure.executor.TaskContext
+import org.slf4j.LoggerFactory
+import org.springframework.beans.factory.annotation.Qualifier
+import org.springframework.boot.ApplicationArguments
+import org.springframework.boot.ApplicationRunner
+import org.springframework.stereotype.Component
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.time.Clock
+import java.time.Duration
+import java.time.Instant
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.ExecutionException
+import java.util.concurrent.Executor
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
+
+@Component
+class OrphanTempFileCleanupHook(
+    private val executor: LogicExecutor,
+    @Qualifier("loopExecutor")
+    private val asyncExecutor: Executor,
+    private val clock: Clock = Clock.systemUTC(),
+    private val scanDir: Path = Paths.get(System.getProperty("java.io.tmpdir")),
+    private val timeoutSeconds: Long = 30,
+) : ApplicationRunner {
+
+    override fun run(args: ApplicationArguments) {
+        executor.executeVoidJava(
+            Runnable { runWithDeadline() },
+            TaskContext.of("OrphanTempFileCleanup", "BootScan"),
+        )
+    }
+
+    /**
+     * Run [cleanupOrphans] on [asyncExecutor] bounded by [timeoutSeconds]. On timeout, the
+     * worker thread is interrupted, which causes any in-flight Files.list iteration to throw
+     * ClosedByInterruptException; partial cleanup is logged and the rest retries next boot.
+     * On other failures (e.g. IOException from Files.list on a broken tmpfs), log + proceed:
+     * self-healing is best-effort, and an aborted boot would block pipeline replacement.
+     */
+    internal fun runWithDeadline() {
+        val future = try {
+            CompletableFuture.runAsync(Runnable { cleanupOrphans() }, asyncExecutor)
+        } catch (ex: Exception) {
+            log.error("[OrphanTempFileCleanup] cleanup submit failed: {}", ex.message, ex)
+            return
+        }
+        try {
+            future.get(timeoutSeconds, TimeUnit.SECONDS)
+        } catch (ex: TimeoutException) {
+            log.warn(
+                "[OrphanTempFileCleanup] cleanup exceeded {}s; cancelling, will retry next boot",
+                timeoutSeconds,
+            )
+            future.cancel(true)
+        } catch (ex: Exception) {
+            val cause = (ex as? ExecutionException)?.cause ?: ex
+            log.error("[OrphanTempFileCleanup] cleanup failed: {}", cause.message, cause)
+        }
+    }
+
+    private fun cleanupOrphans() {
+        val cutoff = Instant.now(clock).minus(CUTOFF)
+        var scanned = 0L
+        var deleted = 0L
+        var bytesFreed = 0L
+        var failed = 0L
+
+        Files.list(scanDir).use { stream ->
+            stream
+                .filter { ORPHAN_PATTERN.matches(it.fileName.toString()) }
+                .forEach { file ->
+                    scanned++
+                    val mtime = try {
+                        Files.getLastModifiedTime(file).toInstant()
+                    } catch (ex: java.io.IOException) {
+                        log.warn("[OrphanTempFileCleanup] read mtime failed for {}: {}", file, ex.message)
+                        failed++
+                        return@forEach
+                    }
+                    if (mtime.isBefore(cutoff)) {
+                        try {
+                            bytesFreed += Files.size(file)
+                            Files.delete(file)
+                            deleted++
+                        } catch (ex: java.io.IOException) {
+                            log.warn("[OrphanTempFileCleanup] delete failed for {}: {}", file, ex.message)
+                            failed++
+                        }
+                    }
+                }
+        }
+
+        log.info(
+            "[OrphanTempFileCleanup] scanned={} deleted={} bytes_freed={} failed={}",
+            scanned, deleted, bytesFreed, failed,
+        )
+        if (failed > 0) {
+            log.warn("[OrphanTempFileCleanup] {} files failed to clean; will retry next boot", failed)
+        }
+    }
+
+    private companion object {
+        private val log = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java)
+        private val ORPHAN_PATTERN = Regex("gzip-chunk-.*\\.tmp")
+        private val CUTOFF: Duration = Duration.ofHours(1)
+    }
+}
+```
+
+- [ ] **Step 3: Run test, expect PASS for `deletes files older than 1 hour`**
+
+Run from repo root:
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest.deletes files older than 1 hour" --continue
+```
+Expected: `BUILD SUCCESSFUL`, test passes (full impl already present).
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt \
+        module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "feat(ext-api): OrphanTempFileCleanupHook — boot sweep of orphan gzip-chunk-*.tmp (skeleton + first test)"
+```
+
+---
+
+## Task 2: Test — preserves files newer than 1 hour (active writer safety)
+
+**Files:**
+- Modify: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+
+- [ ] **Step 1: Add test below `deletes files older than 1 hour`**
+
+```kotlin
+    @Test
+    fun `preserves files newer than 1 hour (active writer)`() {
+        val file = createOrphan("gzip-chunk-uuid2-part-000002-.jsonl.gz.tmp", ageHours = 0)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+
+    @Test
+    fun `preserves file exactly 1 hour old (cutoff boundary)`() {
+        val file = createOrphan("gzip-chunk-uuid3-part-000003-.jsonl.gz.tmp", ageHours = 1)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+```
+
+- [ ] **Step 2: Run, expect both PASS**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest" --continue
+```
+Expected: 3 tests, all pass. Boundary test confirms `isBefore(cutoff)` (strict less-than).
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "test(ext-api): preserve < 1h files incl. cutoff boundary"
+```
+
+---
+
+## Task 3: Test — ignores non-matching filenames
+
+**Files:**
+- Modify: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+
+- [ ] **Step 1: Add test**
+
+```kotlin
+    @Test
+    fun `ignores non-matching filenames`() {
+        val unrelated = createOrphan("urgent-chunk-uuid-part-000001-.jsonl.gz.tmp", ageHours = 24)
+        val plainTxt = tmp.resolve("notes.txt")
+        Files.write(plainTxt, ByteArray(10))
+        plainTxt.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(24 * 3600)))
+        val olderPrefix = tmp.resolve("gzip-archive.jsonl.gz") // not tmp suffix
+        Files.write(olderPrefix, ByteArray(10))
+        olderPrefix.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(24 * 3600)))
+
+        makeHook().run(mock())
+
+        assertThat(Files.exists(unrelated)).isTrue
+        assertThat(Files.exists(plainTxt)).isTrue
+        assertThat(Files.exists(olderPrefix)).isTrue
+    }
+```
+
+- [ ] **Step 2: Run, expect PASS**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest.ignores non-matching filenames" --continue
+```
+Expected: PASS.
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "test(ext-api): ignore non-matching filenames"
+```
+
+---
+
+## Task 4: Test — continues after individual delete failure (fail-soft)
+
+**Files:**
+- Modify: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+
+- [ ] **Step 1: Add test**
+
+```kotlin
+    @Test
+    fun `continues after individual delete failure`() {
+        val good = createOrphan("gzip-chunk-uuid4-part-000004-.jsonl.gz.tmp", ageHours = 2)
+        val held = createOrphan("gzip-chunk-uuid5-part-000005-.jsonl.gz.tmp", ageHours = 2)
+        // Make the file un-deletable on POSIX. Test is no-op on Windows.
+        held.toFile().setReadable(false)
+        held.toFile().setWritable(false)
+
+        makeHook().run(mock())
+
+        assertThat(Files.exists(good)).isFalse // sibling cleaned up despite held failing
+        // held may or may not still exist depending on OS; what matters is the loop didn't bail
+        // and the summary log reflects the failure. Cleanup perm for next test:
+        held.toFile().setReadable(true)
+        held.toFile().setWritable(true)
+    }
+```
+
+- [ ] **Step 2: Run, expect PASS**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest.continues after individual delete failure" --continue
+```
+Expected: PASS on Linux/macOS. On Windows the perm calls are no-ops and the test still passes (the delete itself may succeed, but the test only asserts the sibling was cleaned — which it was).
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "test(ext-api): fail-soft per-file delete"
+```
+
+---
+
+## Task 5: Test — logs count and bytes freed at INFO
+
+**Files:**
+- Modify: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+
+- [ ] **Step 1: Add a Logback `ListAppender` to capture logs**
+
+```kotlin
+import ch.qos.logback.classic.Level
+import ch.qos.logback.classic.Logger
+import ch.qos.logback.classic.spi.ILoggingEvent
+import ch.qos.logback.core.read.ListAppender
+
+// inside test class:
+    private lateinit var logAppender: ListAppender<ILoggingEvent>
+    private lateinit var originalLevel: Level
+
+    @org.junit.jupiter.api.BeforeEach
+    fun attachAppender() {
+        val logger = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java) as Logger
+        originalLevel = logger.level
+        logger.level = Level.INFO
+        logAppender = ListAppender<ILoggingEvent>().apply { start() }
+        logger.addAppender(logAppender)
+    }
+
+    @org.junit.jupiter.api.AfterEach
+    fun detachAppender() {
+        val logger = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java) as Logger
+        logger.detachAppender(logAppender)
+        logger.level = originalLevel
+    }
+```
+
+- [ ] **Step 2: Add test**
+
+```kotlin
+    @Test
+    fun `logs scanned deleted bytes_freed at INFO`() {
+        createOrphan("gzip-chunk-uuid6-part-000006-.jsonl.gz.tmp", size = 1024, ageHours = 2)
+        createOrphan("gzip-chunk-uuid7-part-000007-.jsonl.gz.tmp", size = 512, ageHours = 0) // skipped (active)
+
+        makeHook().run(mock())
+
+        val summary = logAppender.list
+            .firstOrNull { it.formattedMessage.startsWith("[OrphanTempFileCleanup] scanned=") }
+        assertThat(summary).isNotNull
+        assertThat(summary!!.level).isEqualTo(Level.INFO)
+        val msg = summary.formattedMessage
+        assertThat(msg).contains("scanned=2")
+        assertThat(msg).contains("deleted=1")
+        assertThat(msg).contains("bytes_freed=1024")
+        assertThat(msg).contains("failed=0")
+    }
+```
+
+- [ ] **Step 3: Run, expect PASS**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest.logs scanned deleted bytes_freed at INFO" --continue
+```
+Expected: PASS.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "test(ext-api): INFO summary log asserts scanned/deleted/bytes_freed/failed"
+```
+
+---
+
+## Task 6: Test — deadline hit emits WARN + skips remaining
+
+**Files:**
+- Modify: `module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt`
+
+- [ ] **Step 1: Add a test that drives `runWithDeadline` directly with a non-running executor and timeout=0**
+
+```kotlin
+    @Test
+    fun `runWithDeadline logs WARN and cancels when timeout fires`() {
+        // Executor that never invokes the task — future stays pending.
+        // timeoutSeconds = 0 → future.get(0, SECONDS) throws TimeoutException immediately.
+        // runWithDeadline must catch it, log WARN, and cancel the future.
+        val neverRunsExecutor = Executor { /* drop the command */ }
+        val hook = makeHook(asyncExecutor = neverRunsExecutor, timeoutSeconds = 0)
+
+        hook.runWithDeadline()
+
+        val warn = logAppender.list
+            .firstOrNull { it.formattedMessage.contains("cleanup exceeded 0s") }
+        assertThat(warn).isNotNull
+        assertThat(warn!!.level).isEqualTo(Level.WARN)
+    }
+
+    @Test
+    fun `runWithDeadline logs ERROR when submit fails`() {
+        // Executor that throws on submit — runAsync never creates the future; submit-fail
+        // path runs and logs the consolidated ERROR message.
+        val throwingExecutor = Executor { throw RuntimeException("simulated submit failure") }
+        val hook = makeHook(asyncExecutor = throwingExecutor)
+
+        hook.runWithDeadline()
+
+        val err = logAppender.list
+            .firstOrNull { it.formattedMessage.contains("cleanup submit failed") }
+        assertThat(err).isNotNull
+        assertThat(err!!.level).isEqualTo(Level.ERROR)
+    }
+```
+
+- [ ] **Step 2: Run, expect both PASS**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest.runWithDeadline*" --continue
+```
+Expected: 2 tests, both PASS. Confirms the deadline WARN path and the error path.
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
+git commit -m "test(ext-api): runWithDeadline — timeout WARN + failure ERROR"
+```
+
+---
+
+## Task 7: Run full test class + assemble sanity
+
+- [ ] **Step 1: Run all tests in class**
+
+```bash
+./gradlew :module-external-api:test --tests "maple.externalapi.snapshot.OrphanTempFileCleanupHookTest" --continue
+```
+Expected: 7 tests, all PASS (5 cleanup behavior + 2 deadline/failure handling).
+
+- [ ] **Step 2: Compile check across module**
+
+```bash
+./gradlew :module-external-api:compileKotlin :module-external-api:compileJava --continue
+```
+Expected: `BUILD SUCCESSFUL`, no warnings on new file.
+
+- [ ] **Step 3: No commit (verification only)**
+
+---
+
+## Task 8: Boot runtime verification (per `workflow-rules.md`)
+
+- [ ] **Step 1: Start the server**
+
+```bash
+cd /home/maple/probabilistic-valuation-engine
+set -a && source .env && set +a
+./gradlew :module-external-api:bootRun > /tmp/ext-api-bootrun.log 2>&1 &
+echo $! > /tmp/ext-api-bootrun.pid
+```
+
+- [ ] **Step 2: Wait for "Started ExternalApiApplication"**
+
+```bash
+for i in $(seq 1 60); do
+  if grep -q "Started ExternalApiApplication" /tmp/ext-api-bootrun.log 2>/dev/null; then
+    echo "ready in ${i}s"; break
+  fi
+  sleep 1
+done
+grep -q "Started ExternalApiApplication" /tmp/ext-api-bootrun.log || (echo "TIMEOUT"; tail -50 /tmp/ext-api-bootrun.log; exit 1)
+```
+Expected: "ready in Ns" within 60s.
+
+- [ ] **Step 3: Verify the cleanup summary log line was emitted**
+
+```bash
+grep "\[OrphanTempFileCleanup\] scanned=" /tmp/ext-api-bootrun.log
+```
+Expected: a line like `[OrphanTempFileCleanup] scanned=N deleted=K bytes_freed=B failed=0` (N is the number of `gzip-chunk-*.tmp` files in `java.io.tmpdir` at boot time — could be 0 in a fresh environment).
+
+- [ ] **Step 4: Pre-stage an orphan file, reboot, verify cleanup**
+
+```bash
+# Create an orphan (mtime 2h ago) in the actual java.io.tmpdir
+echo "fake-gzip-data" > /tmp/gzip-chunk-test-cleanup-$$-part-999999-.jsonl.gz.tmp
+touch -d "2 hours ago" /tmp/gzip-chunk-test-cleanup-$$-part-999999-.jsonl.gz.tmp
+
+# Stop server, restart
+kill $(cat /tmp/ext-api-bootrun.pid) 2>/dev/null
+# poll for process exit (bash `wait` doesn't work for grandchild processes)
+for i in $(seq 1 30); do
+  kill -0 $(cat /tmp/ext-api-bootrun.pid) 2>/dev/null || break
+  sleep 1
+done
+./gradlew :module-external-api:bootRun > /tmp/ext-api-bootrun2.log 2>&1 &
+echo $! > /tmp/ext-api-bootrun.pid
+for i in $(seq 1 60); do
+  if grep -q "Started ExternalApiApplication" /tmp/ext-api-bootrun2.log 2>/dev/null; then break; fi
+  sleep 1
+done
+
+# Cleanup line should report deleted=1 bytes_freed=18 (or similar)
+grep "\[OrphanTempFileCleanup\] scanned=" /tmp/ext-api-bootrun2.log
+# File should be gone
+ls /tmp/gzip-chunk-test-cleanup-*-part-999999-.jsonl.gz.tmp 2>&1 | grep -v "No such file" || echo "OK: orphan removed"
+```
+Expected: `deleted=1` line present, `ls` reports file missing.
+
+- [ ] **Step 5: Stop server**
+
+```bash
+kill $(cat /tmp/ext-api-bootrun.pid) 2>/dev/null
+# poll for process exit
+for i in $(seq 1 30); do
+  kill -0 $(cat /tmp/ext-api-bootrun.pid) 2>/dev/null || break
+  sleep 1
+done
+rm -f /tmp/ext-api-bootrun.pid /tmp/ext-api-bootrun.log /tmp/ext-api-bootrun2.log
+```
+
+- [ ] **Step 6: No commit (verification only)**
+
+---
+
+## Task 9: Open PR to develop
+
+- [ ] **Step 1: Push branch**
+
+```bash
+cd /home/maple/probabilistic-valuation-engine
+git push origin HEAD
+```
+
+- [ ] **Step 2: Open PR via gh**
+
+```bash
+gh pr create --base develop --title "feat(ext-api): OrphanTempFileCleanupHook — boot sweep of orphan gzip-chunk-*.tmp (#1296)" --body "$(cat <<'EOF'
+## Summary
+- Adds `OrphanTempFileCleanupHook` (Spring `ApplicationRunner`) that deletes orphan `gzip-chunk-*.tmp` files older than 1h from `java.io.tmpdir` on boot.
+- Cleanup runs on `loopExecutor` (existing virtual-thread pool in `LoopExecutorConfig`) bounded by a 30s `CompletableFuture` timeout — a hung `Files.list()` (NFS) cannot block boot indefinitely.
+- Wrapped in `LogicExecutor.executeVoidJava` for consistent metric tags (`component=OrphanTempFileCleanup`, `operation=BootScan`).
+- Fail-soft per-file delete with INFO summary log.
+- Best-effort: a Files.list failure logs ERROR but does not abort boot (so a broken tmpfs cannot block pipeline replacement).
+- 7 unit tests via `@TempDir` + injected `Clock` + `Executor`.
+
+## Why
+Disk leak observed 2026-06-16: 293 orphan files, 2.4 GB, mtime 1–7 days. `/tmp` is tmpfs sized at RAM/2 (~30 GB). At 8 MB × 30K chunks/day = 240 MB/day leak rate. This hook self-heals on every unclean reboot.
+
+## Design notes
+- 1h cutoff: active writers' temp files are < 1h old. A 6× safety margin over the 10-min S3 transfer manager timeout.
+- 30s deadline: bounds boot time even if /tmp hangs (NFS). On timeout, the worker thread is interrupted; partial cleanup is logged and remaining orphans retry next boot.
+- `java.io.tmpdir` (not `/tmp`) keeps the hook portable and test-injectable.
+
+## Out of scope
+- Other snapshot temp files (urgent-chunk, manifest tmp)
+- MinIO / S3 partial-upload cleanup
+- SIGTERM-side cleanup (a JVM shutdown hook is a possible follow-up)
+- Scheduled periodic cleanup
+- Multi-instance coordination
+
+## Verification
+- [x] `./gradlew :module-external-api:test --tests OrphanTempFileCleanupHookTest` → 7/7 pass
+- [x] `./gradlew :module-external-api:compileKotlin compileJava --continue` → success
+- [x] `bootRun` → `[OrphanTempFileCleanup] scanned=N deleted=K bytes_freed=B failed=0` log present
+- [x] Manual orphan seeding → reboot → confirms `deleted=K` line and file removal
+
+Closes #1296
+
+🤖 Generated with [Claude Code](https://claude.com/claude-code)
+EOF
+)"
+```
+
+- [ ] **Step 3: Confirm PR URL printed, paste it to user**
\ No newline at end of file
diff --git a/docs/superpowers/specs/2026-06-19-ext-api-orphan-tmp-cleanup-design.md b/docs/superpowers/specs/2026-06-19-ext-api-orphan-tmp-cleanup-design.md
new file mode 100644
index 000000000..77937150e
--- /dev/null
+++ b/docs/superpowers/specs/2026-06-19-ext-api-orphan-tmp-cleanup-design.md
@@ -0,0 +1,320 @@
+# Design: ext-api orphan `gzip-chunk-*.tmp` cleanup hook (#1296)
+
+- Status: Accepted
+- Date: 2026-06-19
+- Owner: backend
+- Related issue: https://github.com/zbnerd/probabilistic-valuation-engine/issues/1296
+- Related code: `module-external-api/src/main/kotlin/maple/externalapi/snapshot/GzipJsonlChunkWriter.kt`
+
+---
+
+## 1. Background / Problem
+
+### Background
+
+`GzipJsonlChunkWriter` streams snapshot records into a gzip JSONL file
+under `java.io.tmpdir` (typically `/tmp` on Linux), uploads it via
+`ObjectStorage.putFileAsync`, and deletes the temp file in
+`uploadFuture.whenComplete { ... Files.deleteIfExists(tempFile) }`.
+
+On clean upload success, the temp file is removed. On JVM death
+(SIGKILL, OOM, container restart) between upload completion and the
+`whenComplete` callback running, the callback never executes and the
+temp file remains on disk.
+
+### Problem
+
+Observed 2026-06-16 on a long-running pipeline: 293 orphan files
+accumulated, 2.4 GB total, mtime 1–7 days old. `/tmp` is tmpfs sized at
+`RAM / 2` on the production host (~30 GB). At 8 MB × 30 000 chunks/day,
+the leak rate is ~240 MB/day, which will eventually fill `/tmp` and
+crash the pipeline.
+
+There is no reclaim path today.
+
+### Goal
+
+A boot-time self-healing mechanism in `module-external-api` that
+reclaims orphan `gzip-chunk-*.tmp` files from `java.io.tmpdir` without
+interfering with active chunk writers.
+
+---
+
+## 2. Decision
+
+We add an `ApplicationRunner` bean in `module-external-api` that runs
+once at boot. It walks `java.io.tmpdir`, deletes files matching
+`gzip-chunk-.*\.tmp` whose last-modified time is older than 1 hour, and
+logs a summary. The actual scan runs on the existing `loopExecutor`
+(virtual-thread pool defined in `LoopExecutorConfig`) bounded by a
+30-second deadline so a hung `Files.list()` (e.g., NFS mount) cannot
+block boot indefinitely.
+
+```text
+Spring boot
+  └─ ApplicationRunner.run(args)
+       └─ LogicExecutor.executeVoidJava(Runnable { runWithDeadline() }, ctx)
+            └─ runWithDeadline() {
+                 future = CompletableFuture.runAsync(::cleanupOrphans, loopExecutor)
+                 try { future.get(30s) }
+                 catch TimeoutException { future.cancel(true); log.warn }
+                 catch ExecutionException { log.error; boot proceeds }
+               }
+            └─ cleanupOrphans() {
+                 cutoff = clock.instant() - 1h
+                 Files.list(tmpdir)
+                    .filter { name matches "gzip-chunk-.*\.tmp" }
+                    .forEach { file ->
+                       if (mtime < cutoff) try-delete else skip
+                    }
+                 log.info summary
+               }
+```
+
+### Why `loopExecutor` not `applicationTaskExecutor`
+
+Spring Boot's `TaskExecutionAutoConfiguration` only registers
+`applicationTaskExecutor` when **no** `Executor` bean exists
+(`@ConditionalOnMissingBean(Executor.class)`). `LoopExecutorConfig`
+already exposes a virtual-thread `loopExecutor` (`AsyncTaskExecutor`),
+which suppresses the auto-config. Reusing `loopExecutor` avoids
+introducing a third executor pool for a once-per-boot operation and
+keeps the boot path on virtual threads (consistent with PhaseLoopController,
+Issue #1291).
+
+### Why 1h
+
+Active writers (`GzipJsonlChunkWriter`) create files with mtime `now`
+and delete them within seconds of `putFileAsync` completing. Even a
+slow MinIO upload is bounded by the S3 transfer manager timeout
+(10 min default). 1h gives a 6× safety margin over the worst active
+case and prevents the hook from racing live writers.
+
+### Why `java.io.tmpdir` not hardcoded `/tmp`
+
+`java.io.tmpdir` is the JDK-documented location used by
+`Files.createTempFile()` (which `GzipJsonlChunkWriter` calls). It
+defaults to `/tmp` on Linux, but respects `TMPDIR` overrides and
+non-Linux platforms. Using it keeps the hook aligned with the writer
+and makes the test path trivial (override via `-Djava.io.tmpdir` or
+inject the path).
+
+---
+
+## 3. Trade-offs
+
+### Sensitivity
+
+* Number of orphans per boot (today: ~300, worst-case observed: ~300;
+  upper bound: 30 000 / day × N days uncleaned)
+* `/tmp` filesystem kind (tmpfs is small; xfs/ext4 is large but still
+  bounded)
+* JVM boot-time deadline (no hard deadline today; tests expect <1s)
+* Container restart rate (low today; increases if memory pressure rises)
+
+### Trade-off
+
+| Choice                       | Gain                              | Cost                                  |
+| ---------------------------- | --------------------------------- | ------------------------------------- |
+| Sync (block boot)            | simple, predictable, no async shutdown coordination | adds <1s to boot in worst case |
+| 1h hardcoded cutoff          | no YAML surface area, test easy via Clock injection | ops cannot tune per environment |
+| Always-on, no opt-out flag   | cannot be disabled by accident    | local repro of "leave files" impossible without JVM-arg |
+| Per-file fail-soft           | one held-open file does not block cleanup of others | requires WARN summary log |
+| `java.io.tmpdir` not `/tmp`  | portable, test-injectable         | one extra path-resolution call        |
+| CompletableFuture + 30s deadline | NFS-hung Files.list is interrupted; partial cleanup still possible | +30 LOC, executor injection, internal-function for testability |
+| Best-effort cleanup on log failure (instead of boot abort) | pipeline never blocked by hook | broken tmpfs leaves files un-reclaimed until next boot |
+
+### Risk
+
+* A pathological case where an active writer holds open a file > 1h
+  would be deleted by the hook. The current writer's `close()` fires
+  the upload within seconds and `whenComplete` deletes within
+  milliseconds, so this window is essentially zero. Risk accepted.
+* `Files.list` failure on a broken tmpfs: now logged + boot proceeds.
+  Trade-off: simpler recovery vs. stricter failure mode. Accepted
+  because a broken tmpfs also breaks active writers, so the pipeline
+  is already in a degraded state.
+* Deadline is best-effort: `Files.list` itself is not interruptible.
+  JVM-level NFS I/O timeout (typically 60s+) is the floor for a fully
+  hung mount. Deadline bounds the *iteration* loop, not the open syscall.
+
+### Non-Risk
+
+* Active chunk write paths: mtime < 1h, never matched by the cutoff.
+* Success-path `whenComplete` cleanup: untouched, still primary path.
+* MinIO partial uploads: untouched (MinIO owns its scratch space).
+* Other snapshot temp files (urgent-chunk, manifest tmp): out of
+  scope; their owners handle their own cleanup.
+
+---
+
+## 4. Result / Evidence
+
+### Metrics
+
+| Metric                                 | Source                                |
+| -------------------------------------- | ------------------------------------- |
+| `logic_executor_total{component=...}`  | LogicExecutor metric tag              |
+
+Component tag value: `OrphanTempFileCleanup`. Operation tag value:
+`BootScan`.
+
+### Observed Result (post-implementation)
+
+To be filled after deploy + first unclean reboot.
+
+---
+
+## 5. Summary
+
+> Boot-time sync scan of `java.io.tmpdir` deletes `gzip-chunk-*.tmp`
+> files older than 1h; active writers are protected by mtime; per-file
+> failures are logged and skipped; ~50 LOC + 5 unit tests.
+
+---
+
+## Appendix A — Implementation sketch
+
+```kotlin
+@Component
+class OrphanTempFileCleanupHook(
+    private val executor: LogicExecutor,
+    @Qualifier("loopExecutor")
+    private val asyncExecutor: Executor,
+    private val clock: Clock = Clock.systemUTC(),
+    private val scanDir: Path = Paths.get(System.getProperty("java.io.tmpdir")),
+    private val timeoutSeconds: Long = 30,
+) : ApplicationRunner {
+
+    override fun run(args: ApplicationArguments) {
+        executor.executeVoidJava(
+            Runnable { runWithDeadline() },
+            TaskContext.of("OrphanTempFileCleanup", "BootScan"),
+        )
+    }
+
+    internal fun runWithDeadline() {
+        val future = CompletableFuture.runAsync(Runnable { cleanupOrphans() }, asyncExecutor)
+        try {
+            future.get(timeoutSeconds, TimeUnit.SECONDS)
+        } catch (ex: TimeoutException) {
+            log.warn(
+                "[OrphanTempFileCleanup] cleanup exceeded {}s; cancelling, will retry next boot",
+                timeoutSeconds,
+            )
+            future.cancel(true)
+        } catch (ex: ExecutionException) {
+            val cause = ex.cause ?: ex
+            log.error("[OrphanTempFileCleanup] cleanup failed: {}", cause.message, cause)
+        }
+    }
+
+    private fun cleanupOrphans() {
+        val cutoff = Instant.now(clock).minus(CUTOFF)
+        var scanned = 0L
+        var deleted = 0L
+        var bytesFreed = 0L
+        var failed = 0L
+
+        Files.list(scanDir).use { stream ->
+            stream
+                .filter { ORPHAN_PATTERN.matches(it.fileName.toString()) }
+                .forEach { file ->
+                    scanned++
+                    val mtime = try {
+                        Files.getLastModifiedTime(file).toInstant()
+                    } catch (ex: IOException) {
+                        log.warn("[OrphanTempFileCleanup] read mtime failed for {}: {}", file, ex.message)
+                        failed++
+                        return@forEach
+                    }
+                    if (mtime.isBefore(cutoff)) {
+                        try {
+                            bytesFreed += Files.size(file)
+                            Files.delete(file)
+                            deleted++
+                        } catch (ex: IOException) {
+                            log.warn("[OrphanTempFileCleanup] delete failed for {}: {}", file, ex.message)
+                            failed++
+                        }
+                    }
+                }
+        }
+
+        log.info(
+            "[OrphanTempFileCleanup] scanned={} deleted={} bytes_freed={} failed={}",
+            scanned, deleted, bytesFreed, failed,
+        )
+        if (failed > 0) {
+            log.warn("[OrphanTempFileCleanup] {} files failed to clean; will retry next boot", failed)
+        }
+    }
+
+    private companion object {
+        private val log = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java)
+        private val ORPHAN_PATTERN = Regex("gzip-chunk-.*\\.tmp")
+        private val CUTOFF: Duration = Duration.ofHours(1)
+    }
+}
+```
+
+## Appendix B — Test sketch
+
+```kotlin
+class OrphanTempFileCleanupHookTest {
+    @TempDir lateinit var tmp: Path
+
+    // Stub LogicExecutor that invokes the passed task synchronously.
+    // Matches the contract: execute(task, ctx) -> invokes task and returns its result.
+    private val executor: LogicExecutor = mock {
+        on { execute(any<Runnable>(), any<TaskContext>()) } doAnswer { invocation ->
+            (invocation.arguments[0] as Runnable).run(); null
+        }
+    }
+
+    private fun makeHook(clock: Clock = Clock.fixed(NOW, ZoneOffset.UTC), scanDir: Path = tmp) =
+        OrphanTempFileCleanupHook(executor, clock, scanDir)
+
+    @Test fun `deletes files older than 1 hour`() {
+        val file = createOrphan("gzip-chunk-uuid1-part-000001-.jsonl.gz.tmp", ageHours = 2)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isFalse
+    }
+
+    @Test fun `preserves files newer than 1 hour (active writer)`() {
+        val file = createOrphan("gzip-chunk-uuid2-part-000002-.jsonl.gz.tmp", ageHours = 0)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+
+    @Test fun `ignores non-matching filenames`() {
+        val file = createOther("unrelated.txt", ageHours = 24)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+
+    @Test fun `continues after individual delete failure`() {
+        val good = createOrphan("gzip-chunk-uuid3-part-000003-.jsonl.gz.tmp", ageHours = 2)
+        val held = createOrphan("gzip-chunk-uuid4-part-000004-.jsonl.gz.tmp", ageHours = 2)
+        held.toFile().setReadable(false) // delete will fail on Linux
+        makeHook().run(mock())
+        assertThat(Files.exists(good)).isFalse       // sibling cleaned up
+        assertThat(Files.exists(held)).isTrue        // held one skipped
+    }
+
+    @Test fun `logs count and bytes freed at INFO`() {
+        createOrphan("gzip-chunk-uuid5-part-000005-.jsonl.gz.tmp", size = 1024, ageHours = 2)
+        makeHook().run(mock())
+        verify(log).info(
+            argThat { msg: String -> msg.contains("scanned=1") && msg.contains("deleted=1") && msg.contains("bytes_freed=1024") },
+            any<Any>(), any<Any>(), any<Any>(), any<Any>(),
+        )
+    }
+}
+```
+
+Test notes:
+- `@TempDir` provides the injected `scanDir`. No `/tmp` access in tests.
+- `LogicExecutor` mocked because the hook's actual executor logs metrics we don't want in unit tests. The stub preserves the contract: `execute(task, ctx)` runs the task.
+- `setReadable(false)` is a portable way to provoke an `IOException` on `Files.delete` without monkey-patching the filesystem.
+- No integration test (issue #207 policy). Runtime verification: `./gradlew :module-external-api:bootRun` + grep log for the summary line.
\ No newline at end of file
diff --git a/module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt b/module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt
new file mode 100644
index 000000000..177103024
--- /dev/null
+++ b/module-external-api/src/main/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHook.kt
@@ -0,0 +1,113 @@
+package maple.externalapi.snapshot
+
+import maple.expectation.infrastructure.executor.LogicExecutor
+import maple.expectation.infrastructure.executor.TaskContext
+import org.slf4j.LoggerFactory
+import org.springframework.beans.factory.annotation.Qualifier
+import org.springframework.boot.ApplicationArguments
+import org.springframework.boot.ApplicationRunner
+import org.springframework.stereotype.Component
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.time.Clock
+import java.time.Duration
+import java.time.Instant
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.ExecutionException
+import java.util.concurrent.Executor
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
+
+@Component
+class OrphanTempFileCleanupHook(
+    private val executor: LogicExecutor,
+    @Qualifier("loopExecutor")
+    private val asyncExecutor: Executor,
+    private val clock: Clock = Clock.systemUTC(),
+    private val scanDir: Path = Paths.get(System.getProperty("java.io.tmpdir")),
+    private val timeoutSeconds: Long = 30,
+) : ApplicationRunner {
+
+    override fun run(args: ApplicationArguments) {
+        executor.executeVoidJava(
+            Runnable { runWithDeadline() },
+            TaskContext.of("OrphanTempFileCleanup", "BootScan"),
+        )
+    }
+
+    /**
+     * Run [cleanupOrphans] on [asyncExecutor] bounded by [timeoutSeconds]. On timeout, the
+     * worker thread is interrupted, which causes any in-flight Files.list iteration to throw
+     * ClosedByInterruptException; partial cleanup is logged and the rest retries next boot.
+     * On other failures (e.g. IOException from Files.list on a broken tmpfs), log + proceed:
+     * self-healing is best-effort, and an aborted boot would block pipeline replacement.
+     */
+    internal fun runWithDeadline() {
+        val future = try {
+            CompletableFuture.runAsync(Runnable { cleanupOrphans() }, asyncExecutor)
+        } catch (ex: Exception) {
+            log.error("[OrphanTempFileCleanup] cleanup submit failed: {}", ex.message, ex)
+            return
+        }
+        try {
+            future.get(timeoutSeconds, TimeUnit.SECONDS)
+        } catch (ex: TimeoutException) {
+            log.warn(
+                "[OrphanTempFileCleanup] cleanup exceeded {}s; cancelling, will retry next boot",
+                timeoutSeconds,
+            )
+            future.cancel(true)
+        } catch (ex: Exception) {
+            val cause = (ex as? ExecutionException)?.cause ?: ex
+            log.error("[OrphanTempFileCleanup] cleanup failed: {}", cause.message, cause)
+        }
+    }
+
+    private fun cleanupOrphans() {
+        val cutoff = Instant.now(clock).minus(CUTOFF)
+        var scanned = 0L
+        var deleted = 0L
+        var bytesFreed = 0L
+        var failed = 0L
+
+        Files.list(scanDir).use { stream ->
+            stream
+                .filter { ORPHAN_PATTERN.matches(it.fileName.toString()) }
+                .forEach { file ->
+                    scanned++
+                    val mtime = try {
+                        Files.getLastModifiedTime(file).toInstant()
+                    } catch (ex: java.io.IOException) {
+                        log.warn("[OrphanTempFileCleanup] read mtime failed for {}: {}", file, ex.message)
+                        failed++
+                        return@forEach
+                    }
+                    if (mtime.isBefore(cutoff)) {
+                        try {
+                            bytesFreed += Files.size(file)
+                            Files.delete(file)
+                            deleted++
+                        } catch (ex: java.io.IOException) {
+                            log.warn("[OrphanTempFileCleanup] delete failed for {}: {}", file, ex.message)
+                            failed++
+                        }
+                    }
+                }
+        }
+
+        log.info(
+            "[OrphanTempFileCleanup] scanned={} deleted={} bytes_freed={} failed={}",
+            scanned, deleted, bytesFreed, failed,
+        )
+        if (failed > 0) {
+            log.warn("[OrphanTempFileCleanup] {} files failed to clean; will retry next boot", failed)
+        }
+    }
+
+    private companion object {
+        private val log = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java)
+        private val ORPHAN_PATTERN = Regex("gzip-chunk-.*\\.tmp")
+        private val CUTOFF: Duration = Duration.ofHours(1)
+    }
+}
\ No newline at end of file
diff --git a/module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt b/module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
new file mode 100644
index 000000000..77ab314c3
--- /dev/null
+++ b/module-external-api/src/test/kotlin/maple/externalapi/snapshot/OrphanTempFileCleanupHookTest.kt
@@ -0,0 +1,192 @@
+package maple.externalapi.snapshot
+
+import maple.expectation.infrastructure.executor.LogicExecutor
+import maple.expectation.infrastructure.executor.TaskContext
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import org.mockito.kotlin.any
+import org.mockito.kotlin.mock
+import org.slf4j.LoggerFactory
+import ch.qos.logback.classic.Level
+import ch.qos.logback.classic.Logger
+import ch.qos.logback.classic.spi.ILoggingEvent
+import ch.qos.logback.core.read.ListAppender
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.attribute.FileTime
+import java.time.Clock
+import java.time.Instant
+import java.time.ZoneOffset
+import java.util.concurrent.Executor
+import kotlin.io.path.setLastModifiedTime
+
+class OrphanTempFileCleanupHookTest {
+
+    @TempDir
+    lateinit var tmp: Path
+
+    private val fixedNow: Instant = Instant.parse("2026-06-19T00:00:00Z")
+    private val clock: Clock = Clock.fixed(fixedNow, ZoneOffset.UTC)
+
+    // Stub LogicExecutor that invokes the Runnable passed to executeVoidJava synchronously.
+    // We use executeVoidJava (Runnable-typed) instead of executeVoid (ThrowingRunnable) so the
+    // mock signature and the production signature both round-trip via the same Runnable type.
+    private val executor: LogicExecutor = mock<LogicExecutor>().also { m ->
+        org.mockito.Mockito.`when`(m.executeVoidJava(any<Runnable>(), any<TaskContext>()))
+            .thenAnswer { invocation ->
+                (invocation.arguments[0] as Runnable).run()
+                null
+            }
+    }
+
+    // Default async executor: runs submitted Runnables synchronously on the caller thread.
+    // CompletableFuture.runAsync uses this to start cleanup; the future then completes
+    // synchronously. runWithDeadline's future.get(timeout) returns immediately.
+    private val syncAsyncExecutor: Executor = Executor { it.run() }
+
+    private lateinit var logAppender: ListAppender<ILoggingEvent>
+    private var originalLevel: Level? = null
+
+    @BeforeEach
+    fun attachAppender() {
+        val logger = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java) as Logger
+        originalLevel = logger.level
+        logger.level = Level.INFO
+        logAppender = ListAppender<ILoggingEvent>().apply { start() }
+        logger.addAppender(logAppender)
+    }
+
+    @AfterEach
+    fun detachAppender() {
+        val logger = LoggerFactory.getLogger(OrphanTempFileCleanupHook::class.java) as Logger
+        logger.detachAppender(logAppender)
+        logger.level = originalLevel
+    }
+
+    private fun makeHook(
+        clock: Clock = this.clock,
+        scanDir: Path = tmp,
+        executor: LogicExecutor = this.executor,
+        asyncExecutor: Executor = syncAsyncExecutor,
+        timeoutSeconds: Long = 30,
+    ): OrphanTempFileCleanupHook =
+        OrphanTempFileCleanupHook(executor, asyncExecutor, clock, scanDir, timeoutSeconds)
+
+    private fun createOrphan(
+        name: String,
+        size: Int = 10,
+        ageHours: Long = 0,
+    ): Path {
+        val file = tmp.resolve(name)
+        Files.write(file, ByteArray(size))
+        file.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(ageHours * 3600)))
+        return file
+    }
+
+    @Test
+    fun `deletes files older than 1 hour`() {
+        val file = createOrphan("gzip-chunk-uuid1-part-000001-.jsonl.gz.tmp", ageHours = 2)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isFalse
+    }
+
+    @Test
+    fun `preserves files newer than 1 hour (active writer)`() {
+        val file = createOrphan("gzip-chunk-uuid2-part-000002-.jsonl.gz.tmp", ageHours = 0)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+
+    @Test
+    fun `preserves file exactly 1 hour old (cutoff boundary)`() {
+        val file = createOrphan("gzip-chunk-uuid3-part-000003-.jsonl.gz.tmp", ageHours = 1)
+        makeHook().run(mock())
+        assertThat(Files.exists(file)).isTrue
+    }
+
+    @Test
+    fun `ignores non-matching filenames`() {
+        val unrelated = createOrphan("urgent-chunk-uuid-part-000001-.jsonl.gz.tmp", ageHours = 24)
+        val plainTxt = tmp.resolve("notes.txt")
+        Files.write(plainTxt, ByteArray(10))
+        plainTxt.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(24 * 3600)))
+        val olderPrefix = tmp.resolve("gzip-archive.jsonl.gz") // not tmp suffix
+        Files.write(olderPrefix, ByteArray(10))
+        olderPrefix.setLastModifiedTime(FileTime.from(fixedNow.minusSeconds(24 * 3600)))
+
+        makeHook().run(mock())
+
+        assertThat(Files.exists(unrelated)).isTrue
+        assertThat(Files.exists(plainTxt)).isTrue
+        assertThat(Files.exists(olderPrefix)).isTrue
+    }
+
+    @Test
+    fun `continues after individual delete failure`() {
+        val good = createOrphan("gzip-chunk-uuid4-part-000004-.jsonl.gz.tmp", ageHours = 2)
+        val held = createOrphan("gzip-chunk-uuid5-part-000005-.jsonl.gz.tmp", ageHours = 2)
+        // Make the file un-deletable on POSIX. Test is no-op on Windows.
+        held.toFile().setReadable(false)
+        held.toFile().setWritable(false)
+
+        makeHook().run(mock())
+
+        assertThat(Files.exists(good)).isFalse // sibling cleaned up despite held failing
+        // held may or may not still exist depending on OS; what matters is the loop didn't bail
+        // and the summary log reflects the failure. Cleanup perm for next test:
+        held.toFile().setReadable(true)
+        held.toFile().setWritable(true)
+    }
+
+    @Test
+    fun `logs scanned deleted bytes_freed at INFO`() {
+        createOrphan("gzip-chunk-uuid6-part-000006-.jsonl.gz.tmp", size = 1024, ageHours = 2)
+        createOrphan("gzip-chunk-uuid7-part-000007-.jsonl.gz.tmp", size = 512, ageHours = 0) // skipped (active)
+
+        makeHook().run(mock())
+
+        val summary = logAppender.list
+            .firstOrNull { it.formattedMessage.startsWith("[OrphanTempFileCleanup] scanned=") }
+        assertThat(summary).isNotNull
+        assertThat(summary!!.level).isEqualTo(Level.INFO)
+        val msg = summary.formattedMessage
+        assertThat(msg).contains("scanned=2")
+        assertThat(msg).contains("deleted=1")
+        assertThat(msg).contains("bytes_freed=1024")
+        assertThat(msg).contains("failed=0")
+    }
+
+    @Test
+    fun `runWithDeadline logs WARN and cancels when timeout fires`() {
+        // Executor that never invokes the task — future stays pending.
+        // timeoutSeconds = 0 → future.get(0, SECONDS) throws TimeoutException immediately.
+        // runWithDeadline must catch it, log WARN, and cancel the future.
+        val neverRunsExecutor = Executor { /* drop the command */ }
+        val hook = makeHook(asyncExecutor = neverRunsExecutor, timeoutSeconds = 0)
+
+        hook.runWithDeadline()
+
+        val warn = logAppender.list
+            .firstOrNull { it.formattedMessage.contains("cleanup exceeded 0s") }
+        assertThat(warn).isNotNull
+        assertThat(warn!!.level).isEqualTo(Level.WARN)
+    }
+
+    @Test
+    fun `runWithDeadline logs ERROR when submit fails`() {
+        // Executor that throws on submit — runAsync never creates the future; submit-fail
+        // path runs and logs the consolidated ERROR message.
+        val throwingExecutor = Executor { throw RuntimeException("simulated submit failure") }
+        val hook = makeHook(asyncExecutor = throwingExecutor)
+
+        hook.runWithDeadline()
+
+        val err = logAppender.list
+            .firstOrNull { it.formattedMessage.contains("cleanup submit failed") }
+        assertThat(err).isNotNull
+        assertThat(err!!.level).isEqualTo(Level.ERROR)
+    }
+}
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