diff --git a/src/paired-execution-context-reviewer.ts b/src/paired-execution-context-reviewer.ts
index 0f5c59c..57b64b8 100644
--- a/src/paired-execution-context-reviewer.ts
+++ b/src/paired-execution-context-reviewer.ts
@@ -209,6 +209,9 @@ export function handleReviewerCompletion(args: {
     visibleVerdict: verdict,
     roundTripCount: task.round_trip_count,
     deadlockThreshold,
+    // Always finite (independent of arbiter availability) so reviewer STEP_DONE
+    // ping-pong terminates instead of looping forever when arbiter is disabled.
+    stepDoneDeadlockThreshold: ARBITER_DEADLOCK_THRESHOLD,
   });
 
   switch (signal.kind) {
diff --git a/src/paired-execution-context-shared.test.ts b/src/paired-execution-context-shared.test.ts
index 8f6bb59..9f883cb 100644
--- a/src/paired-execution-context-shared.test.ts
+++ b/src/paired-execution-context-shared.test.ts
@@ -127,6 +127,7 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: parseVisibleVerdict('APPROVE\nverified'),
         roundTripCount: 2,
         deadlockThreshold: 2,
+        stepDoneDeadlockThreshold: 2,
       }),
     ).toEqual({ kind: 'request_owner_finalize' });
     expect(
@@ -134,6 +135,7 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: 'task_done',
         roundTripCount: 0,
         deadlockThreshold: 3,
+        stepDoneDeadlockThreshold: 3,
       }),
     ).toEqual({ kind: 'request_owner_finalize' });
     expect(
@@ -141,6 +143,7 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: 'step_done',
         roundTripCount: 0,
         deadlockThreshold: 3,
+        stepDoneDeadlockThreshold: 3,
       }),
     ).toEqual({ kind: 'request_owner_changes' });
     expect(
@@ -148,6 +151,7 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: 'done',
         roundTripCount: 0,
         deadlockThreshold: 3,
+        stepDoneDeadlockThreshold: 3,
       }),
     ).toEqual({ kind: 'request_owner_finalize' });
     expect(
@@ -155,6 +159,7 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: 'continue',
         roundTripCount: 1,
         deadlockThreshold: 3,
+        stepDoneDeadlockThreshold: 3,
       }),
     ).toEqual({ kind: 'request_owner_changes' });
     expect(
@@ -162,26 +167,40 @@ describe('paired execution context shared verdict helpers', () => {
         visibleVerdict: 'done_with_concerns',
         roundTripCount: 3,
         deadlockThreshold: 3,
+        stepDoneDeadlockThreshold: 3,
       }),
     ).toEqual({ kind: 'request_arbiter' });
   });
 
-  it('routes reviewer step_done to arbiter once round trips hit the deadlock threshold', () => {
-    // Below threshold: keep iterating with the owner.
+  it('routes reviewer step_done to arbiter once round trips hit its own finite threshold', () => {
+    // Below the step_done threshold: keep iterating with the owner.
     expect(
       resolveReviewerCompletionSignal({
         visibleVerdict: 'step_done',
         roundTripCount: 1,
         deadlockThreshold: 2,
+        stepDoneDeadlockThreshold: 2,
       }),
     ).toEqual({ kind: 'request_owner_changes' });
-    // At/above threshold: break the owner⇄reviewer step_done oscillation by
-    // escalating to the arbiter instead of looping forever.
+    // At/above the step_done threshold: break the owner⇄reviewer step_done
+    // oscillation by escalating to the arbiter instead of looping forever.
     expect(
       resolveReviewerCompletionSignal({
         visibleVerdict: 'step_done',
         roundTripCount: 2,
         deadlockThreshold: 2,
+        stepDoneDeadlockThreshold: 2,
+      }),
+    ).toEqual({ kind: 'request_arbiter' });
+    // Regression guard: when arbiter is disabled the caller passes
+    // deadlockThreshold=Infinity, but step_done must STILL terminate via its own
+    // finite threshold — otherwise the production loop (arbiter off) never ends.
+    expect(
+      resolveReviewerCompletionSignal({
+        visibleVerdict: 'step_done',
+        roundTripCount: 2,
+        deadlockThreshold: Number.POSITIVE_INFINITY,
+        stepDoneDeadlockThreshold: 2,
       }),
     ).toEqual({ kind: 'request_arbiter' });
   });
diff --git a/src/paired-execution-context-shared.ts b/src/paired-execution-context-shared.ts
index dcd995c..2bb0217 100644
--- a/src/paired-execution-context-shared.ts
+++ b/src/paired-execution-context-shared.ts
@@ -104,15 +104,28 @@ export function resolveReviewerCompletionSignal(args: {
   visibleVerdict: VisibleVerdict;
   roundTripCount: number;
   deadlockThreshold: number;
+  stepDoneDeadlockThreshold: number;
 }): CompletionSignal {
-  const { visibleVerdict, roundTripCount, deadlockThreshold } = args;
+  const {
+    visibleVerdict,
+    roundTripCount,
+    deadlockThreshold,
+    stepDoneDeadlockThreshold,
+  } = args;
 
   switch (visibleVerdict) {
     case 'task_done':
     case 'done':
       return { kind: 'request_owner_finalize' };
     case 'step_done':
-      if (roundTripCount >= deadlockThreshold) {
+      // Reviewer STEP_DONE while the owner keeps replying TASK_DONE is a
+      // content-free oscillation, so it must terminate even when no arbiter is
+      // configured (deadlockThreshold would otherwise be Infinity and never
+      // trip). Use the always-finite arbiter threshold; once it is hit,
+      // requestArbiterOrEscalate routes to the arbiter, or escalates to the
+      // user when no arbiter exists. Productive REVISE/continue disagreement
+      // keeps using deadlockThreshold below and is intentionally left alone.
+      if (roundTripCount >= stepDoneDeadlockThreshold) {
         return { kind: 'request_arbiter' };
       }
       return { kind: 'request_owner_changes' };
diff --git a/src/paired-execution-context.test.ts b/src/paired-execution-context.test.ts
index ccaf4fc..7628766 100644
--- a/src/paired-execution-context.test.ts
+++ b/src/paired-execution-context.test.ts
@@ -1444,6 +1444,95 @@ describe('paired execution context', () => {
     );
   });
 
+  it('escalates reviewer STEP_DONE to the user at the threshold when arbiter is disabled', () => {
+    vi.spyOn(config, 'isArbiterEnabled').mockReturnValue(false);
+    vi.mocked(db.getPairedTaskById).mockReturnValue(
+      buildPairedTask({
+        status: 'in_review',
+        round_trip_count: config.ARBITER_DEADLOCK_THRESHOLD,
+      }),
+    );
+
+    completePairedExecutionContext({
+      taskId: 'task-1',
+      role: 'reviewer',
+      status: 'succeeded',
+      summary: 'STEP_DONE\n남은 단계가 있어 계속 진행합니다.',
+    });
+
+    // Arbiter off: the ping-pong terminates by escalating to the user instead
+    // of looping back to the owner forever.
+    expect(db.updatePairedTask).toHaveBeenCalledWith(
+      'task-1',
+      expect.objectContaining({
+        status: 'completed',
+        completion_reason: 'escalated',
+      }),
+    );
+    expect(db.updatePairedTask).not.toHaveBeenCalledWith(
+      'task-1',
+      expect.objectContaining({
+        status: 'active',
+      }),
+    );
+  });
+
+  it('requests arbiter for reviewer STEP_DONE at the threshold when arbiter is enabled', () => {
+    vi.spyOn(config, 'isArbiterEnabled').mockReturnValue(true);
+    vi.mocked(db.getPairedTaskById).mockReturnValue(
+      buildPairedTask({
+        status: 'in_review',
+        round_trip_count: config.ARBITER_DEADLOCK_THRESHOLD,
+      }),
+    );
+
+    completePairedExecutionContext({
+      taskId: 'task-1',
+      role: 'reviewer',
+      status: 'succeeded',
+      summary: 'STEP_DONE\n남은 단계가 있어 계속 진행합니다.',
+    });
+
+    expect(db.updatePairedTask).toHaveBeenCalledWith(
+      'task-1',
+      expect.objectContaining({
+        status: 'arbiter_requested',
+        arbiter_requested_at: expect.any(String),
+      }),
+    );
+  });
+
+  it('returns reviewer STEP_DONE to the owner below the threshold when arbiter is disabled', () => {
+    vi.spyOn(config, 'isArbiterEnabled').mockReturnValue(false);
+    vi.mocked(db.getPairedTaskById).mockReturnValue(
+      buildPairedTask({
+        status: 'in_review',
+        round_trip_count: config.ARBITER_DEADLOCK_THRESHOLD - 1,
+      }),
+    );
+
+    completePairedExecutionContext({
+      taskId: 'task-1',
+      role: 'reviewer',
+      status: 'succeeded',
+      summary: 'STEP_DONE\n남은 단계가 있어 계속 진행합니다.',
+    });
+
+    expect(db.updatePairedTask).toHaveBeenCalledWith(
+      'task-1',
+      expect.objectContaining({
+        status: 'active',
+      }),
+    );
+    expect(db.updatePairedTask).not.toHaveBeenCalledWith(
+      'task-1',
+      expect.objectContaining({
+        status: 'completed',
+        completion_reason: 'escalated',
+      }),
+    );
+  });
+
   it('keeps reviewer tasks review_ready and increments reviewer_failure_count after the first silent failure', () => {
     vi.mocked(db.getPairedTaskById).mockReturnValue(
       buildPairedTask({