diff --git a/packages/daemon/src/domain/claude-compaction-enforcer.ts b/packages/daemon/src/domain/claude-compaction-enforcer.ts
index 4b561b257..55e4103d7 100644
--- a/packages/daemon/src/domain/claude-compaction-enforcer.ts
+++ b/packages/daemon/src/domain/claude-compaction-enforcer.ts
@@ -323,6 +323,10 @@ export class ClaudeCompactionEnforcer {
   // retired-generation stage → refuse. Injected resolver (atom-B's currentOccupantTenure by session).
   private readonly pendingStageGeneration = new Map<string, string | null>();
   private readonly pendingStageAuthorization = new Map<string, PendingStageAuthorization>();
+  // Monotonic per-seat invalidation identity. Unlike the occupant state maps, this survives
+  // invalidation so an already-awaiting manual trigger can detect a same-name handover even when
+  // best-effort successor tenure minting failed and the durable generation still appears equal.
+  private readonly occupantInvalidationEpoch = new Map<string, number>();
   private readonly resolveOccupantGeneration?: (sessionName: string) => string | null;
   private readonly decisionStore?: Pick<
     EnforcerDecisionStore,
@@ -715,6 +719,7 @@ export class ClaudeCompactionEnforcer {
       resolveCurrentSessionName?: (sessionName: string) => string | null;
     } = {},
   ): Promise<ManualCompactionOutcome> {
+    const startingInvalidationEpoch = this.occupantInvalidationEpoch.get(input.sessionName) ?? 0;
     const startingGenerationUuid = this.resolveOccupantGeneration?.(input.sessionName) ?? null;
     const activeHold = this.findAndObserveHold(input.sessionName, startingGenerationUuid);
     if (activeHold) {
@@ -834,6 +839,13 @@ export class ClaudeCompactionEnforcer {
               error: `Session '${input.sessionName}' changed occupant generation during manual compaction preparation.`,
             };
           }
+          if ((this.occupantInvalidationEpoch.get(input.sessionName) ?? 0) !== startingInvalidationEpoch) {
+            preCompactCheck.reason = "occupant_generation_changed";
+            return {
+              reason: preCompactCheck.reason,
+              error: `Session '${input.sessionName}' was invalidated during manual compaction preparation.`,
+            };
+          }
           return null;
         },
       },
@@ -889,6 +901,10 @@ export class ClaudeCompactionEnforcer {
    * record. Occupant-scoped (no atom-B): the retiring occupant is gone, so a name match IS the ghost.
    */
   invalidateOccupant(sessionName: string): void {
+    this.occupantInvalidationEpoch.set(
+      sessionName,
+      (this.occupantInvalidationEpoch.get(sessionName) ?? 0) + 1,
+    );
     this.lastAutoCompactAt.delete(sessionName);
     this.postCompactRestoreCooldownUntil.delete(sessionName);
     this.triggeredAboveThreshold.delete(sessionName);
diff --git a/packages/daemon/test/w4-enforcement-routes.test.ts b/packages/daemon/test/w4-enforcement-routes.test.ts
index 54badb95c..70597fbb7 100644
--- a/packages/daemon/test/w4-enforcement-routes.test.ts
+++ b/packages/daemon/test/w4-enforcement-routes.test.ts
@@ -8,6 +8,7 @@ import { RigRepository } from "../src/domain/rig-repository.js";
 import { SessionRegistry } from "../src/domain/session-registry.js";
 import { ClaudeCompactionEnforcer } from "../src/domain/claude-compaction-enforcer.js";
 import { EnforcerDecisionStore } from "../src/domain/enforcer-decision-store.js";
+import { DefaultOccupantInvalidator } from "../src/domain/occupant-invalidator.js";
 import { compactionRoutes } from "../src/routes/compaction.js";
 
 const IDENTITY = "orch-lead@rig";
@@ -515,6 +516,47 @@ describe("W4 compaction-control routes", () => {
     expect(tx.delivered).toHaveLength(1);
   });
 
+  it("the public manual trigger refuses a same-alias handover when successor tenure minting fails", async () => {
+    const store = new EnforcerDecisionStore(db, {
+      now: () => new Date("2026-08-08T18:00:00.000Z"),
+      authorizeTtlMinutes: () => 15,
+    });
+    const startingGeneration = sessionRegistry.currentOccupantGenerationForSession(SEAT);
+    let invalidator: DefaultOccupantInvalidator;
+    const tx = makeBoundaryTransport(() => {
+      const mint = vi.spyOn(sessionRegistry, "mintOccupantTenure").mockImplementationOnce(() => {
+        throw new Error("forced successor tenure mint failure");
+      });
+      sessionRegistry.registerClaimedSession(nodeId, SEAT, "handover");
+      mint.mockRestore();
+
+      expect(sessionRegistry.currentOccupantGenerationForSession(SEAT)).toBe(startingGeneration);
+      expect(
+        (db.prepare("SELECT session_name FROM sessions WHERE node_id = ? ORDER BY id DESC LIMIT 1")
+          .get(nodeId) as { session_name: string }).session_name,
+      ).toBe(SEAT);
+      invalidator.invalidateRetiringOccupant({
+        retiringSessionName: SEAT,
+        successorSessionName: SEAT,
+        retiringGeneration: startingGeneration ?? undefined,
+      });
+    });
+    installManualHarness(store, tx.transport);
+    invalidator = new DefaultOccupantInvalidator({
+      enforcer: manualDeps!.enforcer,
+      contextUsage: { invalidateOccupantSidecar: vi.fn() },
+    });
+
+    const response = await request("/api/compaction/trigger", { session: SEAT });
+    expect(response.status).toBe(409);
+    expect(await response.json()).toMatchObject({
+      ok: false,
+      reason: "occupant_generation_changed",
+    });
+    expect(tx.delivered).toHaveLength(1);
+    expect(tx.delivered[0]).toContain("automatic compaction preparation");
+  });
+
   it("lists durable observation fields without requiring a write identity", async () => {
     const response = await request(`/api/compaction/control?session=${encodeURIComponent(SEAT)}`);
     expect(response.status).toBe(200);