feat(queue): 添加队列合并功能，支持跳过重复项并标记源队列为已合并

.claude/commands/issue/queue.md

@@ -65,9 +65,13 @@ Queue formation command using **issue-queue-agent** that analyzes all bound solu
 --queues <n>          Number of parallel queues (default: 1)
 --issue <id>          Form queue for specific issue only
 --append <id>         Append issue to active queue (don't create new)
+--force               Skip active queue check, always create new queue
 
 # CLI subcommands (ccw issue queue ...)
 ccw issue queue list                  List all queues with status
+ccw issue queue add <issue-id>        Add issue to queue (interactive if active queue exists)
+ccw issue queue add <issue-id> -f     Add to new queue without prompt (force)
+ccw issue queue merge <src> --queue <target>  Merge source queue into target queue
 ccw issue queue switch <queue-id>     Switch active queue
 ccw issue queue archive               Archive current queue
 ccw issue queue delete <queue-id>     Delete queue from history
@@ -92,7 +96,7 @@ Phase 2-4: Agent-Driven Queue Formation (issue-queue-agent)
    │   ├─ Build dependency DAG from conflicts
    │   ├─ Calculate semantic priority per solution
    │   └─ Assign execution groups (parallel/sequential)
-   └─ Each agent writes: queue JSON + index update
+   └─ Each agent writes: queue JSON + index update (NOT active yet)
 
 Phase 5: Conflict Clarification (if needed)
    ├─ Collect `clarifications` arrays from all agents
@@ -102,7 +106,24 @@ Phase 5: Conflict Clarification (if needed)
 
 Phase 6: Status Update & Summary
    ├─ Update issue statuses to 'queued'
-   └─ Display queue summary (N queues), next step: /issue:execute
+   └─ Display new queue summary (N queues)
+
+Phase 7: Active Queue Check & Decision (REQUIRED)
+   ├─ Read queue index: ccw issue queue list --brief
+   ├─ Get generated queue ID from agent output
+   ├─ If NO active queue exists:
+   │   ├─ Set generated queue as active_queue_id
+   │   ├─ Update index.json
+   │   └─ Display: "Queue created and activated"
+   │
+   └─ If active queue exists with items:
+       ├─ Display both queues to user
+       ├─ Use AskUserQuestion to prompt:
+       │   ├─ "Use new queue (keep existing)" → Set new as active, keep old inactive
+       │   ├─ "Merge: add new items to existing" → Merge new → existing, delete new
+       │   ├─ "Merge: add existing items to new" → Merge existing → new, archive old
+       │   └─ "Cancel" → Delete new queue, keep existing active
+       └─ Execute chosen action
 ```
 
 ## Implementation
@@ -306,6 +327,41 @@ ccw issue update <issue-id> --status queued
 - Show unplanned issues (planned but NOT in queue)
 - Show next step: `/issue:execute`
 
+### Phase 7: Active Queue Check & Decision
+
+**After agent completes Phase 1-6, check for active queue:**
+
+```bash
+ccw issue queue list --brief
+```
+
+**Decision:**
+- If `active_queue_id` is null → `ccw issue queue switch <new-queue-id>` (activate new queue)
+- If active queue exists → Use **AskUserQuestion** to prompt user
+
+**AskUserQuestion:**
+```javascript
+AskUserQuestion({
+  questions: [{
+    question: "Active queue exists. How would you like to proceed?",
+    header: "Queue Action",
+    options: [
+      { label: "Merge into existing queue", description: "Add new items to active queue, delete new queue" },
+      { label: "Use new queue", description: "Switch to new queue, keep existing in history" },
+      { label: "Cancel", description: "Delete new queue, keep existing active" }
+    ],
+    multiSelect: false
+  }]
+})
+```
+
+**Action Commands:**
+
+| User Choice | Commands |
+|-------------|----------|
+| **Merge into existing** | `ccw issue queue merge <new-queue-id> --queue <active-queue-id>` then `ccw issue queue delete <new-queue-id>` |
+| **Use new queue** | `ccw issue queue switch <new-queue-id>` |
+| **Cancel** | `ccw issue queue delete <new-queue-id>` |
 
 ## Storage Structure (Queue History)
 
@@ -360,6 +416,9 @@ ccw issue update <issue-id> --status queued
 | User cancels clarification | Abort queue formation |
 | **index.json not updated** | Auto-fix: Set active_queue_id to new queue |
 | **Queue file missing solutions** | Abort with error, agent must regenerate |
+| **User cancels queue add** | Display message, return without changes |
+| **Merge with empty source** | Skip merge, display warning |
+| **All items duplicate** | Skip merge, display "All items already exist" |
 
 ## Quality Checklist
 

ccw/src/commands/issue.ts

@@ -650,6 +650,125 @@ function createEmptyQueue(): Queue {
   };
 }
 
+interface MergeResult {
+  success: boolean;
+  itemsMerged: number;
+  totalItems: number;
+  skippedDuplicates: number;
+  reason?: string;
+}
+
+/**
+ * Merge items from source queue into target queue
+ * - Skips duplicate items (same issue_id + solution_id)
+ * - Re-generates item IDs for merged items
+ * - Marks source queue as 'merged' with metadata (or deletes if deleteSource=true)
+ * - Updates queue index
+ */
+function mergeQueues(target: Queue, source: Queue, options?: { deleteSource?: boolean }): MergeResult {
+  const sourceItems = source.solutions || source.tasks || [];
+  const targetItems = target.solutions || target.tasks || [];
+
+  if (sourceItems.length === 0) {
+    return { success: false, itemsMerged: 0, totalItems: targetItems.length, skippedDuplicates: 0, reason: 'Source queue is empty' };
+  }
+
+  // Ensure target has solutions array
+  if (!target.solutions) {
+    target.solutions = [];
+  }
+
+  let itemsMerged = 0;
+  let skippedDuplicates = 0;
+
+  for (const sourceItem of sourceItems) {
+    // Skip if already exists in target (same issue_id + solution_id)
+    const exists = target.solutions.some(
+      t => t.issue_id === sourceItem.issue_id && t.solution_id === sourceItem.solution_id
+    );
+
+    if (exists) {
+      skippedDuplicates++;
+      continue;
+    }
+
+    // Add issue to target's issue_ids if not present
+    if (!target.issue_ids.includes(sourceItem.issue_id)) {
+      target.issue_ids.push(sourceItem.issue_id);
+    }
+
+    // Clone and add item with new item_id
+    const newItem: QueueItem = {
+      ...sourceItem,
+      item_id: generateQueueItemId(target, 'solution'),
+      execution_order: target.solutions.length + 1
+    };
+
+    target.solutions.push(newItem);
+    itemsMerged++;
+  }
+
+  // Merge conflicts if any
+  if (source.conflicts && source.conflicts.length > 0) {
+    if (!target.conflicts) target.conflicts = [];
+    target.conflicts.push(...source.conflicts);
+  }
+
+  // Write updated target queue
+  writeQueue(target);
+
+  // Handle source queue: delete or mark as merged
+  const index = readQueueIndex();
+
+  if (options?.deleteSource) {
+    // Delete source queue file and remove from index
+    const queuePath = join(getQueuesDir(), `${source.id}.json`);
+    if (existsSync(queuePath)) {
+      unlinkSync(queuePath);
+    }
+    index.queues = index.queues.filter(q => q.id !== source.id);
+  } else {
+    // Mark source queue as merged
+    source.status = 'merged' as any;
+    if (!source._metadata) {
+      source._metadata = {
+        version: '2.1',
+        total_tasks: 0,
+        pending_count: 0,
+        executing_count: 0,
+        completed_count: 0,
+        failed_count: 0,
+        updated_at: new Date().toISOString()
+      };
+    }
+    (source._metadata as any).merged_into = target.id;
+    (source._metadata as any).merged_at = new Date().toISOString();
+    writeQueue(source);
+
+    const sourceEntry = index.queues.find(q => q.id === source.id);
+    if (sourceEntry) {
+      sourceEntry.status = 'merged';
+    }
+  }
+
+  // Update target entry in index
+  const targetEntry = index.queues.find(q => q.id === target.id);
+  if (targetEntry) {
+    targetEntry.total_solutions = target.solutions.length;
+    targetEntry.completed_solutions = target.solutions.filter(s => s.status === 'completed').length;
+    targetEntry.issue_ids = target.issue_ids;
+  }
+  writeQueueIndex(index);
+
+  return {
+    success: itemsMerged > 0,
+    itemsMerged,
+    totalItems: target.solutions.length,
+    skippedDuplicates,
+    reason: itemsMerged === 0 ? 'All items already exist in target queue' : undefined
+  };
+}
+
 // ============ Multi-Queue Helper Functions ============
 
 /**
@@ -1826,6 +1945,58 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
     return;
   }
 
+  // Merge queues: ccw issue queue merge <source-id> --queue <target-id>
+  if (subAction === 'merge' && issueId) {
+    const sourceQueueId = issueId; // issueId is actually source queue ID here
+    const targetQueueId = options.queue; // --queue option
+
+    if (!targetQueueId) {
+      console.error(chalk.red('Target queue ID required'));
+      console.error(chalk.gray('Usage: ccw issue queue merge <source-id> --queue <target-id>'));
+      process.exit(1);
+    }
+
+    const sourceQueue = readQueue(sourceQueueId);
+    const targetQueue = readQueue(targetQueueId);
+
+    if (!sourceQueue) {
+      console.error(chalk.red(`Source queue "${sourceQueueId}" not found`));
+      process.exit(1);
+    }
+
+    if (!targetQueue) {
+      console.error(chalk.red(`Target queue "${targetQueueId}" not found`));
+      process.exit(1);
+    }
+
+    // mergeQueues marks source as 'merged' and updates index
+    const result = mergeQueues(targetQueue, sourceQueue);
+
+    if (options.json) {
+      console.log(JSON.stringify({
+        success: result.success,
+        sourceQueueId,
+        targetQueueId,
+        itemsMerged: result.itemsMerged,
+        skippedDuplicates: result.skippedDuplicates,
+        totalItems: result.totalItems,
+        reason: result.reason
+      }, null, 2));
+    } else {
+      if (result.success) {
+        console.log(chalk.green(`✓ Merged ${result.itemsMerged} items from ${sourceQueueId} into ${targetQueueId}`));
+        if (result.skippedDuplicates > 0) {
+          console.log(chalk.gray(`  Skipped ${result.skippedDuplicates} duplicate items`));
+        }
+        console.log(chalk.gray(`  Total items in target: ${result.totalItems}`));
+        console.log(chalk.gray(`  Source queue ${sourceQueueId} marked as 'merged'`));
+      } else {
+        console.log(chalk.yellow(`⚠ Merge skipped: ${result.reason}`));
+      }
+    }
+    return;
+  }
+
   // Archive current queue
   if (subAction === 'archive') {
     const queue = readActiveQueue();
@@ -1900,32 +2071,12 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
       process.exit(1);
     }
 
-    // Get or create active queue (create new if current is completed/archived)
-    let queue = readActiveQueue();
-    const items = queue.solutions || [];
-    const isNewQueue = items.length === 0 || queue.status !== 'active';
-
-    if (queue.status !== 'active') {
-      // Create new queue if current is not active
-      queue = createEmptyQueue();
-    }
-
-    // Ensure solutions array exists
-    if (!queue.solutions) {
-      queue.solutions = [];
-    }
-
-    // Check if solution already in queue
-    const exists = queue.solutions.some(q => q.issue_id === issueId && q.solution_id === solution.id);
-    if (exists) {
-      console.log(chalk.yellow(`Solution ${solution.id} already in queue`));
-      return;
-    }
+    // Step 1: Create new queue (temporary, not active yet)
+    const newQueue = createEmptyQueue();
+    newQueue.solutions = [];
 
     // Add issue to queue's issue list
-    if (!queue.issue_ids.includes(issueId)) {
-      queue.issue_ids.push(issueId);
-    }
+    newQueue.issue_ids.push(issueId);
 
     // Collect all files touched by this solution
     const filesTouched = new Set<string>();
@@ -1936,12 +2087,12 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
     }
 
     // Create solution-level queue item (S-N)
-    queue.solutions.push({
-      item_id: generateQueueItemId(queue, 'solution'),
+    newQueue.solutions.push({
+      item_id: generateQueueItemId(newQueue, 'solution'),
       issue_id: issueId,
       solution_id: solution.id,
       status: 'pending',
-      execution_order: queue.solutions.length + 1,
+      execution_order: 1,
       execution_group: 'P1',
       depends_on: [],
       semantic_priority: 0.5,
@@ -1949,13 +2100,76 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
       files_touched: Array.from(filesTouched)
     });
 
-    writeQueue(queue);
+    // Step 2: Write temporary queue file
+    writeQueue(newQueue);
     updateIssue(issueId, { status: 'queued', queued_at: new Date().toISOString() });
 
-    if (isNewQueue) {
-      console.log(chalk.green(`✓ Created queue ${queue.id}`));
+    console.log(chalk.green(`✓ Created temporary queue ${newQueue.id}`));
+    console.log(chalk.gray(`  Solution ${solution.id} (${solution.tasks?.length || 0} tasks)`));
+
+    // Step 3: Check for existing active queue
+    const existingQueue = readQueue();
+    const hasActiveQueue = existingQueue && existingQueue.status === 'active' &&
+      (existingQueue.solutions?.length || existingQueue.tasks?.length || 0) > 0;
+
+    if (!hasActiveQueue || options.force) {
+      // No active queue or force flag - set new queue as active
+      const index = readQueueIndex();
+      index.active_queue_id = newQueue.id;
+      writeQueueIndex(index);
+      console.log(chalk.green(`✓ Queue ${newQueue.id} activated`));
+      return;
     }
-    console.log(chalk.green(`✓ Added solution ${solution.id} (${solution.tasks?.length || 0} tasks) to queue`));
+
+    // Step 4: Active queue exists - prompt user
+    const existingItems = existingQueue!.solutions || existingQueue!.tasks || [];
+    console.log();
+    console.log(chalk.cyan(`Active queue exists: ${existingQueue!.id}`));
+    console.log(chalk.gray(`  Issues: ${existingQueue!.issue_ids.join(', ')}`));
+    console.log(chalk.gray(`  Items: ${existingItems.length} (${existingItems.filter(i => i.status === 'completed').length} completed)`));
+    console.log();
+
+    const { action } = await inquirer.prompt([{
+      type: 'list',
+      name: 'action',
+      message: 'How would you like to proceed?',
+      choices: [
+        { name: 'Merge into existing queue', value: 'merge_to_existing' },
+        { name: 'Use new queue', value: 'use_new' },
+        { name: 'Cancel', value: 'cancel' }
+      ]
+    }]);
+
+    // Step 5: Execute user choice
+    if (action === 'cancel') {
+      // Delete temporary queue
+      const queuePath = join(getQueuesDir(), `${newQueue.id}.json`);
+      unlinkSync(queuePath);
+      console.log(chalk.yellow(`✓ New queue deleted, keeping ${existingQueue!.id} active`));
+      return;
+    }
+
+    if (action === 'use_new') {
+      // Switch to new queue
+      const index = readQueueIndex();
+      index.active_queue_id = newQueue.id;
+      writeQueueIndex(index);
+      console.log(chalk.green(`✓ Switched to new queue ${newQueue.id}`));
+      console.log(chalk.gray(`  Previous queue ${existingQueue!.id} remains in history`));
+      return;
+    }
+
+    if (action === 'merge_to_existing') {
+      // Merge new → existing, delete temporary queue
+      const mergeResult = mergeQueues(existingQueue!, newQueue, { deleteSource: true });
+      console.log(chalk.green(`✓ Merged ${mergeResult.itemsMerged} items into ${existingQueue!.id}`));
+      if (mergeResult.skippedDuplicates > 0) {
+        console.log(chalk.gray(`  Skipped ${mergeResult.skippedDuplicates} duplicate items`));
+      }
+      console.log(chalk.gray(`  Temporary queue ${newQueue.id} deleted`));
+      return;
+    }
+
     return;
   }
 

ccw/src/core/routes/issue-routes.ts

@@ -637,22 +637,44 @@ export async function handleIssueRoutes(ctx: RouteContext): Promise<boolean> {
         const targetItems = targetQueue.solutions || targetQueue.tasks || [];
         const isSolutionBased = !!targetQueue.solutions;
 
-        // Re-index source items to avoid ID conflicts
-        const maxOrder = targetItems.reduce((max: number, i: any) => Math.max(max, i.execution_order || 0), 0);
-        const reindexedSourceItems = sourceItems.map((item: any, idx: number) => ({
-          ...item,
-          item_id: `${item.item_id}-merged`,
-          execution_order: maxOrder + idx + 1,
-          execution_group: item.execution_group ? `M-${item.execution_group}` : 'M-ungrouped'
-        }));
+        if (!isSolutionBased) {
+          targetQueue.solutions = [];
+        }
 
-        // Merge items
-        const mergedItems = [...targetItems, ...reindexedSourceItems];
+        // Helper to generate next item ID (S-N format)
+        const getNextItemId = (): string => {
+          const items = targetQueue.solutions || [];
+          const maxNum = items.reduce((max: number, i: any) => {
+            const match = i.item_id?.match(/^S-(\d+)$/);
+            return match ? Math.max(max, parseInt(match[1])) : max;
+          }, 0);
+          return `S-${maxNum + 1}`;
+        };
 
-        if (isSolutionBased) {
-          targetQueue.solutions = mergedItems;
-        } else {
-          targetQueue.tasks = mergedItems;
+        let itemsMerged = 0;
+        let skippedDuplicates = 0;
+
+        for (const sourceItem of sourceItems) {
+          // Skip duplicates (same issue_id + solution_id)
+          const exists = (targetQueue.solutions || []).some(
+            (t: any) => t.issue_id === sourceItem.issue_id && t.solution_id === sourceItem.solution_id
+          );
+
+          if (exists) {
+            skippedDuplicates++;
+            continue;
+          }
+
+          // Add with new item_id (S-N format)
+          const newItem = {
+            ...sourceItem,
+            item_id: getNextItemId(),
+            execution_order: (targetQueue.solutions?.length || 0) + 1
+          };
+
+          if (!targetQueue.solutions) targetQueue.solutions = [];
+          targetQueue.solutions.push(newItem);
+          itemsMerged++;
         }
 
         // Merge issue_ids
@@ -662,20 +684,26 @@ export async function handleIssueRoutes(ctx: RouteContext): Promise<boolean> {
         ])];
         targetQueue.issue_ids = mergedIssueIds;
 
+        // Merge conflicts
+        if (sourceQueue.conflicts && sourceQueue.conflicts.length > 0) {
+          if (!targetQueue.conflicts) targetQueue.conflicts = [];
+          targetQueue.conflicts.push(...sourceQueue.conflicts);
+        }
+
         // Update metadata
+        const mergedItems = targetQueue.solutions || [];
         const completedCount = mergedItems.filter((i: any) => i.status === 'completed').length;
         targetQueue._metadata = {
           ...targetQueue._metadata,
           updated_at: new Date().toISOString(),
-          ...(isSolutionBased
-            ? { total_solutions: mergedItems.length, completed_solutions: completedCount }
-            : { total_tasks: mergedItems.length, completed_tasks: completedCount })
+          total_solutions: mergedItems.length,
+          completed_solutions: completedCount
         };
 
         // Write merged queue
         writeFileSync(targetPath, JSON.stringify(targetQueue, null, 2));
 
-        // Update source queue status
+        // Update source queue status to 'merged'
         sourceQueue.status = 'merged';
         sourceQueue._metadata = {
           ...sourceQueue._metadata,
@@ -695,13 +723,8 @@ export async function handleIssueRoutes(ctx: RouteContext): Promise<boolean> {
               sourceEntry.status = 'merged';
             }
             if (targetEntry) {
-              if (isSolutionBased) {
-                targetEntry.total_solutions = mergedItems.length;
-                targetEntry.completed_solutions = completedCount;
-              } else {
-                targetEntry.total_tasks = mergedItems.length;
-                targetEntry.completed_tasks = completedCount;
-              }
+              targetEntry.total_solutions = mergedItems.length;
+              targetEntry.completed_solutions = completedCount;
               targetEntry.issue_ids = mergedIssueIds;
             }
             writeFileSync(indexPath, JSON.stringify(index, null, 2));
@@ -714,7 +737,8 @@ export async function handleIssueRoutes(ctx: RouteContext): Promise<boolean> {
           success: true,
           sourceQueueId,
           targetQueueId,
-          mergedItemCount: sourceItems.length,
+          mergedItemCount: itemsMerged,
+          skippedDuplicates,
           totalItems: mergedItems.length
         };
       } catch (err) {

ccw/tests/integration/issue-routes.test.ts

@@ -292,5 +292,65 @@ describe('issue routes integration', async () => {
     assert.equal(Array.isArray(res.json.execution_groups), true);
     assert.equal(typeof res.json.grouped_items, 'object');
   });
+
+  it('POST /api/queue/merge merges source queue into target and skips duplicates', async () => {
+    const { writeFileSync, mkdirSync } = await import('fs');
+    const { join } = await import('path');
+
+    // Create queues directory
+    const queuesDir = join(projectRoot, '.workflow', 'issues', 'queues');
+    mkdirSync(queuesDir, { recursive: true });
+
+    // Create target queue
+    const targetQueue = {
+      id: 'QUE-TARGET',
+      status: 'active',
+      issue_ids: ['ISS-1'],
+      solutions: [
+        { item_id: 'S-1', issue_id: 'ISS-1', solution_id: 'SOL-1', status: 'pending' }
+      ],
+      conflicts: []
+    };
+    writeFileSync(join(queuesDir, 'QUE-TARGET.json'), JSON.stringify(targetQueue));
+
+    // Create source queue with one duplicate and one new item
+    const sourceQueue = {
+      id: 'QUE-SOURCE',
+      status: 'active',
+      issue_ids: ['ISS-1', 'ISS-2'],
+      solutions: [
+        { item_id: 'S-1', issue_id: 'ISS-1', solution_id: 'SOL-1', status: 'pending' }, // Duplicate
+        { item_id: 'S-2', issue_id: 'ISS-2', solution_id: 'SOL-2', status: 'pending' }  // New
+      ],
+      conflicts: []
+    };
+    writeFileSync(join(queuesDir, 'QUE-SOURCE.json'), JSON.stringify(sourceQueue));
+
+    // Create index
+    writeFileSync(join(queuesDir, 'index.json'), JSON.stringify({
+      active_queue_id: 'QUE-TARGET',
+      queues: [
+        { id: 'QUE-TARGET', status: 'active' },
+        { id: 'QUE-SOURCE', status: 'active' }
+      ]
+    }));
+
+    // Merge
+    const res = await requestJson(baseUrl, 'POST', '/api/queue/merge', {
+      sourceQueueId: 'QUE-SOURCE',
+      targetQueueId: 'QUE-TARGET'
+    });
+
+    assert.equal(res.status, 200);
+    assert.equal(res.json.success, true);
+    assert.equal(res.json.mergedItemCount, 1); // Only new item merged
+    assert.equal(res.json.skippedDuplicates, 1); // Duplicate skipped
+    assert.equal(res.json.totalItems, 2); // Target now has 2 items
+
+    // Verify source queue is marked as merged
+    const sourceContent = JSON.parse(readFileSync(join(queuesDir, 'QUE-SOURCE.json'), 'utf8'));
+    assert.equal(sourceContent.status, 'merged');
+    assert.equal(sourceContent._metadata.merged_into, 'QUE-TARGET');
+  });
 });
 

ccw/tests/issue-command.test.ts

@@ -965,6 +965,182 @@ describe('issue command module', async () => {
 
       assert.equal(existsSync(join(env.queuesDir, `${queueId}.json`)), false);
     });
+
+    it('queue merge merges source queue into target and marks source as merged', async () => {
+      issueModule ??= await import(issueCommandUrl);
+      assert.ok(env);
+
+      const logs: string[] = [];
+      mock.method(console, 'log', (...args: any[]) => {
+        logs.push(args.map(String).join(' '));
+      });
+      mock.method(console, 'error', () => {});
+
+      // Create target queue
+      const targetId = 'QUE-TARGET-001';
+      issueModule.writeQueue({
+        id: targetId,
+        status: 'active',
+        issue_ids: ['ISS-1'],
+        tasks: [],
+        solutions: [
+          {
+            item_id: 'S-1',
+            issue_id: 'ISS-1',
+            solution_id: 'SOL-ISS-1-1',
+            status: 'pending',
+            execution_order: 1,
+            files_touched: ['src/a.ts'],
+            task_count: 1,
+          },
+        ],
+        conflicts: [],
+      });
+
+      // Create source queue
+      const sourceId = 'QUE-SOURCE-001';
+      issueModule.writeQueue({
+        id: sourceId,
+        status: 'active',
+        issue_ids: ['ISS-2'],
+        tasks: [],
+        solutions: [
+          {
+            item_id: 'S-1',
+            issue_id: 'ISS-2',
+            solution_id: 'SOL-ISS-2-1',
+            status: 'pending',
+            execution_order: 1,
+            files_touched: ['src/b.ts'],
+            task_count: 2,
+          },
+        ],
+        conflicts: [{ id: 'CFT-1', type: 'file', severity: 'low' }],
+      });
+
+      // Set target as active queue
+      const indexPath = join(env.queuesDir, 'index.json');
+      writeFileSync(indexPath, JSON.stringify({ active_queue_id: targetId, queues: [] }));
+
+      await issueModule.issueCommand('queue', ['merge', sourceId], { queue: targetId });
+
+      // Verify merge result
+      const mergedTarget = issueModule.readQueue(targetId);
+      assert.ok(mergedTarget);
+      assert.equal(mergedTarget.solutions.length, 2);
+      assert.equal(mergedTarget.solutions[0].item_id, 'S-1');
+      assert.equal(mergedTarget.solutions[1].item_id, 'S-2'); // Re-generated ID
+      assert.equal(mergedTarget.solutions[1].issue_id, 'ISS-2');
+      assert.deepEqual(mergedTarget.issue_ids, ['ISS-1', 'ISS-2']);
+      assert.equal(mergedTarget.conflicts.length, 1); // Merged conflicts
+
+      // Verify source queue is marked as merged
+      const sourceQueue = issueModule.readQueue(sourceId);
+      assert.ok(sourceQueue);
+      assert.equal(sourceQueue.status, 'merged');
+      assert.equal(sourceQueue._metadata?.merged_into, targetId);
+    });
+
+    it('queue merge skips duplicate solutions with same issue_id and solution_id', async () => {
+      issueModule ??= await import(issueCommandUrl);
+      assert.ok(env);
+
+      mock.method(console, 'log', () => {});
+      mock.method(console, 'error', () => {});
+
+      const targetId = 'QUE-TARGET-DUP';
+      const sourceId = 'QUE-SOURCE-DUP';
+
+      // Create target with a solution
+      issueModule.writeQueue({
+        id: targetId,
+        status: 'active',
+        issue_ids: ['ISS-DUP'],
+        tasks: [],
+        solutions: [
+          {
+            item_id: 'S-1',
+            issue_id: 'ISS-DUP',
+            solution_id: 'SOL-ISS-DUP-1',
+            status: 'pending',
+            execution_order: 1,
+            files_touched: ['src/dup.ts'],
+            task_count: 1,
+          },
+        ],
+        conflicts: [],
+      });
+
+      // Create source with same solution (duplicate)
+      issueModule.writeQueue({
+        id: sourceId,
+        status: 'active',
+        issue_ids: ['ISS-DUP'],
+        tasks: [],
+        solutions: [
+          {
+            item_id: 'S-1',
+            issue_id: 'ISS-DUP',
+            solution_id: 'SOL-ISS-DUP-1', // Same issue_id + solution_id
+            status: 'pending',
+            execution_order: 1,
+            files_touched: ['src/dup.ts'],
+            task_count: 1,
+          },
+        ],
+        conflicts: [],
+      });
+
+      const indexPath = join(env.queuesDir, 'index.json');
+      writeFileSync(indexPath, JSON.stringify({ active_queue_id: targetId, queues: [] }));
+
+      await issueModule.issueCommand('queue', ['merge', sourceId], { queue: targetId });
+
+      const mergedTarget = issueModule.readQueue(targetId);
+      assert.ok(mergedTarget);
+      // Should still have only 1 solution (duplicate skipped)
+      assert.equal(mergedTarget.solutions.length, 1);
+      assert.equal(mergedTarget.solutions[0].solution_id, 'SOL-ISS-DUP-1');
+    });
+
+    it('queue merge returns skipped reason when source is empty', async () => {
+      issueModule ??= await import(issueCommandUrl);
+      assert.ok(env);
+
+      const logs: string[] = [];
+      mock.method(console, 'log', (...args: any[]) => {
+        logs.push(args.map(String).join(' '));
+      });
+      mock.method(console, 'error', () => {});
+
+      const targetId = 'QUE-TARGET-EMPTY';
+      const sourceId = 'QUE-SOURCE-EMPTY';
+
+      issueModule.writeQueue({
+        id: targetId,
+        status: 'active',
+        issue_ids: [],
+        tasks: [],
+        solutions: [{ item_id: 'S-1', issue_id: 'ISS-1', solution_id: 'SOL-1', status: 'pending' }],
+        conflicts: [],
+      });
+
+      issueModule.writeQueue({
+        id: sourceId,
+        status: 'active',
+        issue_ids: [],
+        tasks: [],
+        solutions: [], // Empty source
+        conflicts: [],
+      });
+
+      const indexPath = join(env.queuesDir, 'index.json');
+      writeFileSync(indexPath, JSON.stringify({ active_queue_id: targetId, queues: [] }));
+
+      await issueModule.issueCommand('queue', ['merge', sourceId], { queue: targetId });
+
+      assert.ok(logs.some((l) => l.includes('skipped') || l.includes('empty')));
+    });
   });
 
   describe('Queue Execution', () => {