diff --git a/src/db.test.ts b/src/db.test.ts
index 610f708..81012c4 100644
--- a/src/db.test.ts
+++ b/src/db.test.ts
@@ -561,6 +561,7 @@ describe('paired task state', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
@@ -602,6 +603,7 @@ describe('paired task state', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
diff --git a/src/db.ts b/src/db.ts
index 4ec0589..55e1ffe 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -256,6 +256,7 @@ function createSchema(database: Database): void {
       status TEXT NOT NULL DEFAULT 'active',
       arbiter_verdict TEXT,
       arbiter_requested_at TEXT,
+      completion_reason TEXT,
       created_at TEXT NOT NULL,
       updated_at TEXT NOT NULL,
       CHECK (status IN ('active', 'review_ready', 'in_review', 'merge_ready', 'completed', 'arbiter_requested', 'in_arbitration'))
@@ -633,6 +634,7 @@ function createSchema(database: Database): void {
           status TEXT NOT NULL DEFAULT 'active',
           arbiter_verdict TEXT,
           arbiter_requested_at TEXT,
+          completion_reason TEXT,
           created_at TEXT NOT NULL,
           updated_at TEXT NOT NULL,
           CHECK (status IN ('active', 'review_ready', 'in_review', 'merge_ready', 'completed', 'arbiter_requested', 'in_arbitration'))
@@ -664,6 +666,15 @@ function createSchema(database: Database): void {
     /* column already exists */
   }
 
+  // Migration: add completion_reason column to paired_tasks if it doesn't exist
+  try {
+    database.exec(
+      `ALTER TABLE paired_tasks ADD COLUMN completion_reason TEXT`,
+    );
+  } catch {
+    /* column already exists */
+  }
+
   // Drop legacy tables that are no longer used
   for (const table of [
     'paired_executions',
@@ -2035,6 +2046,7 @@ export function updatePairedTask(
       | 'status'
       | 'arbiter_verdict'
       | 'arbiter_requested_at'
+      | 'completion_reason'
       | 'updated_at'
     >
   >,
@@ -2074,6 +2086,10 @@ export function updatePairedTask(
     fields.push('arbiter_requested_at = ?');
     values.push(updates.arbiter_requested_at);
   }
+  if (updates.completion_reason !== undefined) {
+    fields.push('completion_reason = ?');
+    values.push(updates.completion_reason);
+  }
   if (updates.updated_at !== undefined) {
     fields.push('updated_at = ?');
     values.push(updates.updated_at);
diff --git a/src/message-agent-executor.test.ts b/src/message-agent-executor.test.ts
index 3858412..6908b4e 100644
--- a/src/message-agent-executor.test.ts
+++ b/src/message-agent-executor.test.ts
@@ -361,6 +361,7 @@ describe('runAgentForGroup room memory', () => {
         status: 'active',
         arbiter_verdict: null,
         arbiter_requested_at: null,
+        completion_reason: null,
         created_at: '2026-03-29T00:00:00.000Z',
         updated_at: '2026-03-29T00:00:00.000Z',
       },
@@ -425,6 +426,7 @@ describe('runAgentForGroup room memory', () => {
         status: 'active',
         arbiter_verdict: null,
         arbiter_requested_at: null,
+        completion_reason: null,
         created_at: '2026-03-28T00:00:00.000Z',
         updated_at: '2026-03-28T00:00:00.000Z',
       },
@@ -514,6 +516,7 @@ describe('runAgentForGroup room memory', () => {
         status: 'active',
         arbiter_verdict: null,
         arbiter_requested_at: null,
+        completion_reason: null,
         created_at: '2026-03-28T00:00:00.000Z',
         updated_at: '2026-03-28T00:00:00.000Z',
       },
diff --git a/src/message-runtime.test.ts b/src/message-runtime.test.ts
index e1ca1f9..db333d2 100644
--- a/src/message-runtime.test.ts
+++ b/src/message-runtime.test.ts
@@ -565,6 +565,7 @@ describe('createMessageRuntime', () => {
       status: 'review_ready',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: '2026-03-30T00:00:00.000Z',
       updated_at: '2026-03-30T00:00:00.000Z',
     });
diff --git a/src/message-runtime.ts b/src/message-runtime.ts
index 1e6008e..377db25 100644
--- a/src/message-runtime.ts
+++ b/src/message-runtime.ts
@@ -846,6 +846,7 @@ export function createMessageRuntime(deps: MessageRuntimeDeps): {
               if (task) {
                 updatePairedTask(task.id, {
                   status: 'completed',
+                  completion_reason: 'stopped',
                   updated_at: new Date().toISOString(),
                 });
               }
diff --git a/src/paired-execution-context.test.ts b/src/paired-execution-context.test.ts
index 9df010f..d1e07fa 100644
--- a/src/paired-execution-context.test.ts
+++ b/src/paired-execution-context.test.ts
@@ -112,6 +112,7 @@ function buildPairedTask(overrides: Partial<PairedTask> = {}): PairedTask {
     status: 'active',
     arbiter_verdict: null,
     arbiter_requested_at: null,
+    completion_reason: null,
     created_at: '2026-03-28T00:00:00.000Z',
     updated_at: '2026-03-28T00:00:00.000Z',
     ...overrides,
@@ -202,6 +203,7 @@ describe('paired execution context', () => {
       status: 'review_ready',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+    completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
@@ -236,6 +238,7 @@ describe('paired execution context', () => {
       status: 'review_ready',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+    completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
@@ -273,6 +276,7 @@ describe('paired execution context', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+    completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
@@ -316,6 +320,7 @@ describe('paired execution context', () => {
       status: 'in_review',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+    completion_reason: null,
       created_at: '2026-03-28T00:00:00.000Z',
       updated_at: '2026-03-28T00:00:00.000Z',
     });
diff --git a/src/paired-execution-context.ts b/src/paired-execution-context.ts
index 8901abb..cd4af75 100644
--- a/src/paired-execution-context.ts
+++ b/src/paired-execution-context.ts
@@ -189,6 +189,7 @@ function ensureActiveTask(
     status: 'active',
     arbiter_verdict: null,
     arbiter_requested_at: null,
+    completion_reason: null,
     created_at: now,
     updated_at: now,
   };
@@ -384,6 +385,7 @@ export function completePairedExecutionContext(args: {
         updatePairedTask(taskId, {
           status: verdict === 'done' ? 'merge_ready' : 'completed',
           ...(verdict === 'done' ? { source_ref: approvedSourceRef } : {}),
+          ...(verdict !== 'done' ? { completion_reason: 'escalated' } : {}),
           updated_at: now,
         });
         logger.info(
@@ -442,7 +444,7 @@ export function completePairedExecutionContext(args: {
 
         if (hasNewChanges === false) {
           // No code changes since reviewer approved → finalize complete
-          updatePairedTask(taskId, { status: 'completed', updated_at: now });
+          updatePairedTask(taskId, { status: 'completed', completion_reason: 'done', updated_at: now });
           logger.info(
             { taskId, summary: args.summary?.slice(0, 100) },
             'Owner finalized after reviewer approval — task completed',
@@ -573,7 +575,7 @@ export function completePairedExecutionContext(args: {
             'Reviewer blocked/needs_context — requesting arbiter before escalating',
           );
         } else {
-          updatePairedTask(taskId, { status: 'completed', updated_at: now });
+          updatePairedTask(taskId, { status: 'completed', completion_reason: 'escalated', updated_at: now });
           logger.info(
             { taskId, verdict, summary: args.summary?.slice(0, 100) },
             'Reviewer escalated to user — ping-pong stopped',
@@ -598,7 +600,7 @@ export function completePairedExecutionContext(args: {
               'Deadlock detected — requesting arbiter intervention',
             );
           } else {
-            updatePairedTask(taskId, { status: 'completed', updated_at: now });
+            updatePairedTask(taskId, { status: 'completed', completion_reason: 'escalated', updated_at: now });
             logger.info(
               { taskId, verdict, roundTrips: task.round_trip_count },
               'Stopped ping-pong — escalating to user (arbiter not configured)',
@@ -646,6 +648,7 @@ export function completePairedExecutionContext(args: {
         updatePairedTask(taskId, {
           status: 'completed',
           arbiter_verdict: 'escalate',
+          completion_reason: 'arbiter_escalated',
           updated_at: now,
         });
         logger.info({ taskId }, 'Arbiter escalated to user — task completed');
@@ -655,6 +658,7 @@ export function completePairedExecutionContext(args: {
         updatePairedTask(taskId, {
           status: 'completed',
           arbiter_verdict: 'unknown',
+          completion_reason: 'arbiter_escalated',
           updated_at: now,
         });
         break;
diff --git a/src/paired-workspace-manager.test.ts b/src/paired-workspace-manager.test.ts
index e92f7b7..feaa1cc 100644
--- a/src/paired-workspace-manager.test.ts
+++ b/src/paired-workspace-manager.test.ts
@@ -80,6 +80,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
@@ -171,6 +172,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
@@ -249,6 +251,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
@@ -326,6 +329,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
@@ -469,6 +473,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
@@ -533,6 +538,7 @@ describe('paired workspace manager', () => {
       status: 'review_ready',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: '2026-03-28T00:01:00.000Z',
     });
@@ -601,6 +607,7 @@ describe('paired workspace manager', () => {
       status: 'active',
       arbiter_verdict: null,
       arbiter_requested_at: null,
+      completion_reason: null,
       created_at: now,
       updated_at: now,
     });
diff --git a/src/types.ts b/src/types.ts
index 2347955..e2c392c 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -71,6 +71,7 @@ export interface PairedTask {
   status: PairedTaskStatus;
   arbiter_verdict: string | null;
   arbiter_requested_at: string | null;
+  completion_reason: string | null;
   created_at: string;
   updated_at: string;
 }