diff --git a/server/src/__tests__/heartbeat-workspace-session.test.ts b/server/src/__tests__/heartbeat-workspace-session.test.ts
index 26734c687d..a969382862 100644
--- a/server/src/__tests__/heartbeat-workspace-session.test.ts
+++ b/server/src/__tests__/heartbeat-workspace-session.test.ts
@@ -25,6 +25,7 @@ import {
   prioritizeProjectWorkspaceCandidatesForRun,
   parseSessionCompactionPolicy,
   provisionExecutionWorkspaceForFreshnessDecision,
+  reconcileReusedExecutionWorkspaceProjectWorkspaceId,
   resolveExecutionWorkspaceConfigFreshness,
   resolveExecutionWorkspaceReuseRequestForIssue,
   resolveExecutionWorkspaceReuseProvisioningPolicy,
@@ -2884,3 +2885,29 @@ describe("isWorkspaceSyncConflictFailure", () => {
     expect(isWorkspaceSyncConflictFailure("")).toBe(false);
   });
 });
+
+describe("reconcileReusedExecutionWorkspaceProjectWorkspaceId", () => {
+  it("backfills a null existing binding from the resolved value", () => {
+    expect(
+      reconcileReusedExecutionWorkspaceProjectWorkspaceId(null, "resolved-workspace"),
+    ).toBe("resolved-workspace");
+  });
+
+  it("never overwrites an existing binding, even when a resolved value is present", () => {
+    expect(
+      reconcileReusedExecutionWorkspaceProjectWorkspaceId("existing-workspace", "resolved-workspace"),
+    ).toBe("existing-workspace");
+  });
+
+  it("returns null when both existing and resolved are absent", () => {
+    expect(reconcileReusedExecutionWorkspaceProjectWorkspaceId(null, null)).toBeNull();
+    expect(reconcileReusedExecutionWorkspaceProjectWorkspaceId(undefined, undefined)).toBeNull();
+    expect(reconcileReusedExecutionWorkspaceProjectWorkspaceId(null, undefined)).toBeNull();
+  });
+
+  it("backfills when existing is undefined and resolved is present", () => {
+    expect(
+      reconcileReusedExecutionWorkspaceProjectWorkspaceId(undefined, "resolved-workspace"),
+    ).toBe("resolved-workspace");
+  });
+});
diff --git a/server/src/services/heartbeat.ts b/server/src/services/heartbeat.ts
index 11e9e24725..f9eddcbd5b 100644
--- a/server/src/services/heartbeat.ts
+++ b/server/src/services/heartbeat.ts
@@ -1979,6 +1979,26 @@ export async function assertPushCapabilityCheckoutValid(input: {
   );
 }
 
+/**
+ * Reconcile the `projectWorkspaceId` for a reused execution workspace.
+ *
+ * A `reuse_existing` workspace can have been persisted with a null
+ * `projectWorkspaceId` (e.g. it was created before its project had a primary
+ * project workspace). When we later restore it for a run whose issue now
+ * expects a concrete project workspace, backfill the column so the launch
+ * guard (`persisted_workspace_missing_project_workspace_id`) stops rejecting
+ * it on every requeue — otherwise `reuse_existing` re-binds the same stale
+ * record forever and the run crash-loops. Prefer the existing binding when
+ * present so we never null out a good value or silently rebind a genuine
+ * mismatch (which the guard still surfaces).
+ */
+export function reconcileReusedExecutionWorkspaceProjectWorkspaceId(
+  existingProjectWorkspaceId: string | null | undefined,
+  resolvedProjectWorkspaceId: string | null | undefined,
+): string | null {
+  return existingProjectWorkspaceId ?? resolvedProjectWorkspaceId ?? null;
+}
+
 export async function assertGitSensitiveAdapterWorkspaceValid(input: {
   adapterType: string;
   agentId: string;
@@ -14578,6 +14598,10 @@ export function heartbeatService(db: Db, options: HeartbeatServiceOptions = {})
             status: "active",
             lastUsedAt: new Date(),
             metadata: nextExecutionWorkspaceMetadata,
+            projectWorkspaceId: reconcileReusedExecutionWorkspaceProjectWorkspaceId(
+              reusableExistingExecutionWorkspace.projectWorkspaceId,
+              resolvedProjectWorkspaceId,
+            ),
           })
         : resolvedProjectId
           ? await executionWorkspacesSvc.create({