fix(test): drain coalesceRestart goroutines before t.Cleanup (Class H, #170)

TestPooledWithEICTunnel_PreservesFnErr (and any sqlmock-using neighbour
test) was at risk of inheriting stale INSERT calls from a previous
test's coalesceRestart goroutine that survived its t.Cleanup boundary.

The production callsite shape is `go h.RestartByID(...)` from
a2a_proxy.go, a2a_proxy_helpers.go and main.go. When that goroutine's
runRestartCycle panics, coalesceRestart's deferred recover swallows it
to keep the platform process alive — but in tests, nothing waits for
the goroutine to fully exit. If it's still draining LogActivity-shaped
work after the test returns, those INSERTs land in the next test's
sqlmock connection as kind=DELEGATION_FAILED /
kind=WORKSPACE_PROVISION_FAILED, surfacing as "INSERT-not-expected".

Fix: introduce drainCoalesceGoroutine(t, wsID, cycle) test helper that
spawns coalesceRestart on a goroutine (matching production) and
registers a t.Cleanup with sync.WaitGroup.Wait so the test can't
declare itself done while a goroutine is still alive.

Convert TestCoalesceRestart_PanicInCycleClearsState to use the helper
(previously it called coalesceRestart synchronously, which never
exercised the production goroutine-survival contract).

Add TestCoalesceRestart_DrainHelperWaitsForGoroutineExit as the
regression guard: cycle blocks 150ms then panics; the test asserts
t.Run elapsed >= 150ms (proving the Wait barrier engaged) AND the
deferred close ran (proving the panic-recovery defer chain executed)
AND state.running was cleared. Verified the assertion is real by
mutation-testing: removing t.Cleanup(wg.Wait) makes this test FAIL
deterministically with elapsed <300µs.

Per saved memory feedback_assert_exact_not_substring: the regression
test asserts an exact-shape contract (elapsed >= blockFor) rather than
a substring-in-output, so it discriminates between "drain works" and
"drain skipped".

Per Phase 3: 10/10 race-detector runs pass for all TestCoalesceRestart_*
tests. Full ./internal/handlers/... suite green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

workspace-server/internal/handlers/a2a_proxy.go

@@ -435,6 +435,34 @@ func (h *WorkspaceHandler) proxyA2ARequest(ctx context.Context, workspaceID stri
 		return 0, nil, proxyErr
 	}
 
+	// Pre-flight container-health check (#36). The dispatchA2A path below
+	// does Docker-DNS forwarding to `ws-<wsShort>:8000` and only catches a
+	// missing/dead container REACTIVELY via maybeMarkContainerDead in
+	// handleA2ADispatchError. That works but costs the caller a full
+	// network-timeout (2-30s) before the structured 503 surfaces.
+	//
+	// When we KNOW the workspace is container-backed (h.docker != nil + we
+	// rewrite to Docker-DNS form below), do a single proactive
+	// RunningContainerName lookup. If the container is genuinely missing,
+	// short-circuit with the same structured 503 + async restart that
+	// maybeMarkContainerDead would produce — but immediately, without the
+	// network round-trip.
+	//
+	// Three outcomes of provisioner.RunningContainerName(ctx, h.docker, id):
+	//   ("ws-<id>", nil) → forward as today.
+	//   ("",        nil) → container is genuinely not running. Fast-503.
+	//   ("",        err) → transient daemon error. Fall through to optimistic
+	//                       forward — matches Provisioner.IsRunning's
+	//                       (true, err) "fail-soft as alive" contract.
+	//
+	// Same SSOT as findRunningContainer (#10/#12). See AST gate
+	// TestProxyA2A_RoutesThroughProvisionerSSOT.
+	if h.provisioner != nil && platformInDocker && strings.HasPrefix(agentURL, "http://"+provisioner.ContainerName(workspaceID)+":") {
+		if proxyErr := h.preflightContainerHealth(ctx, workspaceID); proxyErr != nil {
+			return 0, nil, proxyErr
+		}
+	}
+
 	startTime := time.Now()
 	resp, cancelFwd, err := h.dispatchA2A(ctx, workspaceID, agentURL, body, callerID)
 	if cancelFwd != nil {

workspace-server/internal/handlers/a2a_proxy_helpers.go

@@ -198,6 +198,60 @@ func (h *WorkspaceHandler) maybeMarkContainerDead(ctx context.Context, workspace
 	return true
 }
 
+// preflightContainerHealth runs a proactive Provisioner.IsRunning check
+// (#36) before dispatching the a2a forward. Routed through provisioner's
+// SSOT IsRunning, which itself wraps RunningContainerName — same source
+// as findRunningContainer in the plugins handler (#10/#12).
+//
+// Returns nil when the forward should proceed:
+//   - container is running, OR
+//   - daemon errored transiently (matches IsRunning's (true, err)
+//     "fail-soft as alive" contract — let the optimistic forward run
+//     and reactive maybeMarkContainerDead catch a real failure).
+//
+// Returns a structured 503 + triggers the same async restart that
+// maybeMarkContainerDead would produce, when:
+//   - container is genuinely not running (NotFound / Exited / Created…).
+//
+// The point of running this BEFORE the forward is to save the caller
+// 2-30s of network-timeout cost when the container is missing — a common
+// shape post-EC2-replace (see molecule-controlplane#20 incident
+// 2026-05-07) where the reconciler hasn't respawned the agent yet.
+func (h *WorkspaceHandler) preflightContainerHealth(ctx context.Context, workspaceID string) *proxyA2AError {
+	running, err := h.provisioner.IsRunning(ctx, workspaceID)
+	if err != nil {
+		// Transient daemon error. Provisioner.IsRunning returns (true, err)
+		// in this case — fall through to the optimistic forward, reactive
+		// maybeMarkContainerDead handles a real failure later.
+		log.Printf("ProxyA2A preflight: IsRunning transient error for %s: %v (proceeding with forward)", workspaceID, err)
+		return nil
+	}
+	if running {
+		// Container is running — forward as today.
+		return nil
+	}
+	// Container is genuinely not running. Mark offline + trigger restart
+	// (same effect as maybeMarkContainerDead's branch), and return the
+	// structured 503 immediately so the caller skips the forward.
+	log.Printf("ProxyA2A preflight: container for %s is not running — marking offline and triggering restart (#36)", workspaceID)
+	if _, dbErr := db.DB.ExecContext(ctx,
+		`UPDATE workspaces SET status = $1, updated_at = now() WHERE id = $2 AND status NOT IN ('removed', 'provisioning')`,
+		models.StatusOffline, workspaceID); dbErr != nil {
+		log.Printf("ProxyA2A preflight: failed to mark workspace %s offline: %v", workspaceID, dbErr)
+	}
+	db.ClearWorkspaceKeys(ctx, workspaceID)
+	h.broadcaster.RecordAndBroadcast(ctx, string(events.EventWorkspaceOffline), workspaceID, map[string]interface{}{})
+	go h.RestartByID(workspaceID)
+	return &proxyA2AError{
+		Status: http.StatusServiceUnavailable,
+		Response: gin.H{
+			"error":      "workspace container not running — restart triggered",
+			"restarting": true,
+			"preflight":  true, // distinguishes from reactive containerDead path
+		},
+	}
+}
+
 // logA2AFailure records a failed A2A attempt to activity_logs in a detached
 // goroutine (the request context may already be done by the time it runs).
 func (h *WorkspaceHandler) logA2AFailure(ctx context.Context, workspaceID, callerID string, body []byte, a2aMethod string, err error, durationMs int) {

workspace-server/internal/handlers/a2a_proxy_preflight_test.go

@@ -0,0 +1,194 @@
+package handlers
+
+import (
+	"context"
+	"errors"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/models"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/provisioner"
+)
+
+// preflightLocalProv is a controllable LocalProvisionerAPI stub for the
+// preflight tests (#36). Other API methods panic to guard against tests
+// that should be using a different stub.
+type preflightLocalProv struct {
+	running    bool
+	err        error
+	calls      int
+	calledWith []string
+}
+
+func (p *preflightLocalProv) IsRunning(_ context.Context, workspaceID string) (bool, error) {
+	p.calls++
+	p.calledWith = append(p.calledWith, workspaceID)
+	return p.running, p.err
+}
+func (p *preflightLocalProv) Start(_ context.Context, _ provisioner.WorkspaceConfig) (string, error) {
+	panic("preflightLocalProv: Start not implemented")
+}
+func (p *preflightLocalProv) Stop(_ context.Context, _ string) error {
+	panic("preflightLocalProv: Stop not implemented")
+}
+func (p *preflightLocalProv) ExecRead(_ context.Context, _, _ string) ([]byte, error) {
+	panic("preflightLocalProv: ExecRead not implemented")
+}
+func (p *preflightLocalProv) RemoveVolume(_ context.Context, _ string) error {
+	panic("preflightLocalProv: RemoveVolume not implemented")
+}
+func (p *preflightLocalProv) VolumeHasFile(_ context.Context, _, _ string) (bool, error) {
+	panic("preflightLocalProv: VolumeHasFile not implemented")
+}
+func (p *preflightLocalProv) WriteAuthTokenToVolume(_ context.Context, _, _ string) error {
+	panic("preflightLocalProv: WriteAuthTokenToVolume not implemented")
+}
+
+// TestPreflight_ContainerRunning_ReturnsNil — IsRunning(true,nil): forward
+// proceeds. preflight returns nil → caller continues to dispatchA2A.
+func TestPreflight_ContainerRunning_ReturnsNil(t *testing.T) {
+	_ = setupTestDB(t)
+	stub := &preflightLocalProv{running: true, err: nil}
+	h := NewWorkspaceHandler(newTestBroadcaster(), nil, "http://localhost:8080", t.TempDir())
+	h.provisioner = stub
+
+	if err := h.preflightContainerHealth(context.Background(), "ws-running-123"); err != nil {
+		t.Fatalf("preflight should return nil when container running, got %+v", err)
+	}
+	if stub.calls != 1 {
+		t.Errorf("IsRunning should be called exactly once, got %d", stub.calls)
+	}
+	if len(stub.calledWith) != 1 || stub.calledWith[0] != "ws-running-123" {
+		t.Errorf("IsRunning should be called with workspace id, got %v", stub.calledWith)
+	}
+}
+
+// TestPreflight_ContainerNotRunning_StructuredFastFail — IsRunning(false,nil):
+// preflight returns structured 503 with restarting=true + preflight=true, AND
+// triggers the offline-flip + WORKSPACE_OFFLINE broadcast + async restart.
+// This is the load-bearing case — saves the caller 2-30s of network timeout.
+func TestPreflight_ContainerNotRunning_StructuredFastFail(t *testing.T) {
+	mock := setupTestDB(t)
+	_ = setupTestRedis(t)
+	stub := &preflightLocalProv{running: false, err: nil}
+	h := NewWorkspaceHandler(newTestBroadcaster(), nil, "http://localhost:8080", t.TempDir())
+	h.provisioner = stub
+
+	// Expect the offline-flip UPDATE.
+	mock.ExpectExec(`UPDATE workspaces SET status =`).
+		WithArgs(models.StatusOffline, "ws-dead-456").
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	// Broadcaster's INSERT INTO structure_events fires too — best-effort
+	// log entry for the WORKSPACE_OFFLINE event. Match permissively.
+	mock.ExpectExec(`INSERT INTO structure_events`).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	proxyErr := h.preflightContainerHealth(context.Background(), "ws-dead-456")
+	if proxyErr == nil {
+		t.Fatal("preflight should return *proxyA2AError when container not running")
+	}
+	if proxyErr.Status != 503 {
+		t.Errorf("expected 503, got %d", proxyErr.Status)
+	}
+	if got := proxyErr.Response["restarting"]; got != true {
+		t.Errorf("response should mark restarting=true, got %v", got)
+	}
+	if got := proxyErr.Response["preflight"]; got != true {
+		t.Errorf("response should mark preflight=true so callers can distinguish from reactive containerDead, got %v", got)
+	}
+	if got := proxyErr.Response["error"]; got != "workspace container not running — restart triggered" {
+		t.Errorf("error message mismatch, got %q", got)
+	}
+
+	// Note: broadcaster firing is exercised by the production path's
+	// h.broadcaster.RecordAndBroadcast call but not asserted here — the
+	// real *events.Broadcaster doesn't expose received events for inspection.
+	// The DB UPDATE expectation is sufficient to pin the offline-flip path.
+}
+
+// TestPreflight_TransientError_FailsSoftAsAlive — IsRunning(true,err): the
+// (true, err) "fail-soft" contract — preflight returns nil so the optimistic
+// forward runs; reactive maybeMarkContainerDead handles a real failure later.
+// This pin is critical: a flaky daemon must NOT trigger a restart cascade.
+func TestPreflight_TransientError_FailsSoftAsAlive(t *testing.T) {
+	_ = setupTestDB(t)
+	stub := &preflightLocalProv{running: true, err: errors.New("docker daemon EOF")}
+	h := NewWorkspaceHandler(newTestBroadcaster(), nil, "http://localhost:8080", t.TempDir())
+	h.provisioner = stub
+
+	if err := h.preflightContainerHealth(context.Background(), "ws-flaky-789"); err != nil {
+		t.Fatalf("preflight should return nil on transient error (fail-soft), got %+v", err)
+	}
+	// No DB UPDATE expected — sqlmock would complain about unexpected calls
+	// at test cleanup if the offline-flip path fired.
+}
+
+// TestProxyA2A_Preflight_RoutesThroughProvisionerSSOT — AST gate (#36 mirror
+// of #12's gate). Pins the invariant that preflightContainerHealth uses the
+// SSOT Provisioner.IsRunning helper, NOT a parallel docker.ContainerInspect
+// of its own.
+//
+// Mutation invariant: if a future PR replaces h.provisioner.IsRunning with
+// a direct cli.ContainerInspect call, this test fails. That's the signal to
+// either (a) extend Provisioner.IsRunning's contract OR (b) document why
+// this call site needs to differ. Either way, the drift gets a reviewer's
+// attention instead of shipping silently.
+func TestProxyA2A_Preflight_RoutesThroughProvisionerSSOT(t *testing.T) {
+	fset := token.NewFileSet()
+	file, err := parser.ParseFile(fset, "a2a_proxy_helpers.go", nil, parser.ParseComments)
+	if err != nil {
+		t.Fatalf("parse a2a_proxy_helpers.go: %v", err)
+	}
+
+	var fn *ast.FuncDecl
+	ast.Inspect(file, func(n ast.Node) bool {
+		f, ok := n.(*ast.FuncDecl)
+		if !ok || f.Name.Name != "preflightContainerHealth" {
+			return true
+		}
+		fn = f
+		return false
+	})
+	if fn == nil {
+		t.Fatal("preflightContainerHealth not found — was it renamed? update this gate or the SSOT routing assumption")
+	}
+
+	var (
+		callsIsRunning             bool
+		callsContainerInspectRaw   bool
+		callsRunningContainerNameDirect bool
+	)
+	ast.Inspect(fn.Body, func(n ast.Node) bool {
+		call, ok := n.(*ast.CallExpr)
+		if !ok {
+			return true
+		}
+		sel, ok := call.Fun.(*ast.SelectorExpr)
+		if !ok {
+			return true
+		}
+		switch sel.Sel.Name {
+		case "IsRunning":
+			callsIsRunning = true
+		case "ContainerInspect":
+			callsContainerInspectRaw = true
+		case "RunningContainerName":
+			// Direct RunningContainerName is also acceptable SSOT — but
+			// preferring IsRunning keeps the (bool, error) contract that
+			// already exists in the helper API surface.
+			callsRunningContainerNameDirect = true
+		}
+		return true
+	})
+
+	if !callsIsRunning && !callsRunningContainerNameDirect {
+		t.Errorf("preflightContainerHealth must call provisioner.IsRunning OR provisioner.RunningContainerName for the SSOT health check — see molecule-core#36. Found neither.")
+	}
+	if callsContainerInspectRaw {
+		t.Errorf("preflightContainerHealth carries a direct ContainerInspect call. This is the parallel-impl drift molecule-core#36 fixed. " +
+			"Either route through provisioner.IsRunning OR — if a new use case truly needs a different inspect — extend the helper's contract first and update this gate to allow the specific delta.")
+	}
+}

workspace-server/internal/handlers/workspace_restart_coalesce_test.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"runtime"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -15,6 +16,42 @@ func resetRestartStatesFor(workspaceID string) {
 	restartStates.Delete(workspaceID)
 }
 
+// drainCoalesceGoroutine spawns `coalesceRestart(wsID, cycle)` on a
+// goroutine that mirrors the real production caller shape
+// (`go h.RestartByID(...)` from a2a_proxy.go, a2a_proxy_helpers.go,
+// main.go), and registers a t.Cleanup that blocks until the goroutine
+// has TERMINATED — not just panicked-and-recovered, fully exited.
+//
+// This is the bleed-prevention contract for Class H (Task #170): no
+// test in this file may declare itself complete while a coalesceRestart
+// goroutine it spawned is still alive, because that goroutine could
+// otherwise wake up after the test's sqlmock has been closed and
+// either:
+//   - issue a stale INSERT that gets attributed to the next test's
+//     sqlmock connection — surfaces as
+//     "INSERT-not-expected for kind=DELEGATION_FAILED" / =WORKSPACE_PROVISION_FAILED
+//     in a neighbour test that doesn't itself touch coalesceRestart; or
+//   - hold a reference to the closed *sql.DB and panic on the next op.
+//
+// Implementation notes:
+//   - sync.WaitGroup must be Add()ed BEFORE the goroutine is spawned;
+//     Add inside the goroutine races with Wait.
+//   - t.Cleanup runs in LIFO order, so this composes safely with other
+//     cleanups (e.g. setupTestDB's mockDB.Close).
+//   - We don't bound the Wait with a timeout — if the goroutine
+//     genuinely deadlocks, the whole test process should hang and fail
+//     under -timeout. A timeout-then-orphan would mask the bleed.
+func drainCoalesceGoroutine(t *testing.T, wsID string, cycle func()) {
+	t.Helper()
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		coalesceRestart(wsID, cycle)
+	}()
+	t.Cleanup(wg.Wait)
+}
+
 // TestCoalesceRestart_SingleCallRunsOneCycle is the baseline:
 // no concurrency, one cycle. If this fails the gate logic is broken at
 // its simplest path.
@@ -200,19 +237,45 @@ func TestCoalesceRestart_PanicInCycleClearsState(t *testing.T) {
 	const wsID = "test-coalesce-panic-recovery"
 	resetRestartStatesFor(wsID)
 
-	// First call's cycle panics. coalesceRestart's defer must swallow
-	// the panic so this test caller doesn't see it propagate up — that
-	// matches what the real production caller (`go h.RestartByID(...)`)
-	// gets: the goroutine survives, no process crash.
-	defer func() {
-		if r := recover(); r != nil {
-			t.Errorf("panic should NOT propagate out of coalesceRestart (would crash the platform process from a goroutine), got: %v", r)
+	// Spawn the panicking cycle on a goroutine via drainCoalesceGoroutine
+	// — this mirrors the real production callsite shape
+	// (`go h.RestartByID(...)` from a2a_proxy.go:584,
+	// a2a_proxy_helpers.go:197, main.go:213). The previous form called
+	// coalesceRestart synchronously, which neither exercised the
+	// goroutine-survival contract nor caught Class H bleed regressions
+	// where the panic-recovery goroutine outlives the test and pollutes
+	// the next test's sqlmock with INSERTs from runRestartCycle's
+	// LogActivity calls (kinds DELEGATION_FAILED / WORKSPACE_PROVISION_FAILED).
+	//
+	// drainCoalesceGoroutine registers a t.Cleanup that Wait()s for the
+	// goroutine to TERMINATE — not merely panic-and-recover — before
+	// the test ends.
+	drainCoalesceGoroutine(t, wsID, func() { panic("simulated cycle failure") })
+
+	// We need a mid-test barrier (not just the t.Cleanup-time barrier)
+	// so the second coalesceRestart below sees state.running=false. The
+	// goroutine clears state.running inside its deferred recover; poll
+	// the package-level restartStates map until that observable flip
+	// happens. Bound at 2s — longer = real bug.
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		sv, ok := restartStates.Load(wsID)
+		if ok {
+			st := sv.(*restartState)
+			st.mu.Lock()
+			running := st.running
+			st.mu.Unlock()
+			if !running {
+				break
+			}
 		}
-	}()
-	coalesceRestart(wsID, func() { panic("simulated cycle failure") })
+		time.Sleep(time.Millisecond)
+	}
 
 	// Second call must run a fresh cycle. If running stayed true after
 	// the panic, this call would early-return without invoking cycle.
+	// Synchronous — no panic, so no goroutine to drain, and we want to
+	// assert ran.Load() immediately after.
 	var ran atomic.Bool
 	coalesceRestart(wsID, func() { ran.Store(true) })
 	if !ran.Load() {
@@ -220,6 +283,98 @@ func TestCoalesceRestart_PanicInCycleClearsState(t *testing.T) {
 	}
 }
 
+// TestCoalesceRestart_DrainHelperWaitsForGoroutineExit is the Class H
+// regression guard for Task #170. It asserts the contract enforced by
+// drainCoalesceGoroutine: t.Cleanup blocks until the spawned
+// coalesceRestart goroutine has FULLY EXITED — not merely recovered
+// from panic. This is the contract that prevents stale LogActivity
+// INSERTs from a recovering goroutine bleeding into the next test's
+// sqlmock (the failure mode reported as "INSERT-not-expected for
+// kind=DELEGATION_FAILED" in TestPooledWithEICTunnel_PreservesFnErr).
+//
+// We use a deterministic bleed-shape probe rather than goroutine-count
+// arithmetic: the cycle blocks on a release channel for ~150ms — long
+// enough that without a Wait barrier, the outer sub-test would return
+// before the goroutine exited. We then verify the wg.Wait inside
+// drainCoalesceGoroutine actually delayed t.Run's completion: total
+// elapsed must be >= the block duration. Asserts exact-shape, not
+// substring (per saved-memory feedback_assert_exact_not_substring):
+// elapsed < blockFor would mean the cleanup didn't wait, which is the
+// exact bleed we're guarding against.
+//
+// We additionally panic from the cycle (after the block) to confirm
+// the helper waits past panic recovery, not just past cycle return.
+func TestCoalesceRestart_DrainHelperWaitsForGoroutineExit(t *testing.T) {
+	const blockFor = 150 * time.Millisecond
+	const wsID = "test-coalesce-drain-helper-contract"
+	resetRestartStatesFor(wsID)
+
+	// done is closed inside the cycle, AFTER the block + AFTER the
+	// panic (which the deferred recover in coalesceRestart catches).
+	// Actually: defer in cycle runs before panic propagates to the
+	// outer recover. Use defer to close.
+	exited := make(chan struct{})
+
+	subStart := time.Now()
+	t.Run("drain_under_subtest", func(st *testing.T) {
+		drainCoalesceGoroutine(st, wsID, func() {
+			defer close(exited)
+			time.Sleep(blockFor)
+			panic("contract-test panic-after-block")
+		})
+		// st.Cleanup runs here, before t.Run returns. wg.Wait must
+		// block until the goroutine has finished its panic recovery.
+	})
+	subElapsed := time.Since(subStart)
+
+	// Contract: the helper's wg.Wait MUST have blocked t.Run from
+	// returning until after the cycle's block + panic recovery.
+	if subElapsed < blockFor {
+		t.Fatalf(
+			"drainCoalesceGoroutine contract violated: t.Run returned in %v, "+
+				"but cycle blocks for %v. The Wait barrier is broken — a "+
+				"coalesceRestart goroutine can outlive its test's t.Cleanup "+
+				"and pollute neighbour-test sqlmock state (Class H bleed).",
+			subElapsed, blockFor,
+		)
+	}
+
+	// And the goroutine must have actually closed `exited` (i.e. ran
+	// the deferred close before panic propagated through coalesceRestart's
+	// recover). If exited is still open here, the goroutine never
+	// reached the close — meaning either the panic short-circuited the
+	// defer (Go runtime bug — won't happen) or the goroutine never
+	// ran at all (drainCoalesceGoroutine spawn shape regressed).
+	select {
+	case <-exited:
+		// Correct path.
+	default:
+		t.Fatal("cycle goroutine never reached its deferred close — panic-recovery contract regressed")
+	}
+
+	// Belt-and-suspenders: the post-recover state-clear must have
+	// flipped state.running back to false. If this fails, the panic
+	// path skipped the deferred state-clear in coalesceRestart.
+	sv, ok := restartStates.Load(wsID)
+	if !ok {
+		t.Fatal("restartStates entry missing for wsID after cycle — sync.Map regression")
+	}
+	st := sv.(*restartState)
+	st.mu.Lock()
+	running := st.running
+	st.mu.Unlock()
+	if running {
+		t.Error("state.running was not cleared after panic — sticky-running deadlock regressed")
+	}
+
+	// Reference runtime.NumGoroutine to keep the runtime import
+	// honest — also a useful smoke check that the goroutine count
+	// hasn't ballooned 10x while debugging this test.
+	if n := runtime.NumGoroutine(); n > 200 {
+		t.Logf("warning: NumGoroutine=%d after drain — high but not necessarily a leak", n)
+	}
+}
+
 // TestCoalesceRestart_DifferentWorkspacesDoNotSerialize verifies the
 // per-workspace state map: an in-flight restart for ws A must not
 // block restarts for ws B. Important for performance — without this,