diff --git a/app/main.py b/app/main.py
index 0d5955a..ec2adb4 100644
--- a/app/main.py
+++ b/app/main.py
@@ -409,3 +409,33 @@ def list_webhook_logs(webhook_id: int, limit: int = 50, db: Session = Depends(ge
         WebhookLog.webhook_id == webhook_id
     ).order_by(WebhookLog.created_at.desc()).limit(limit).all()
     return logs
+
+
+
+# ============ Issue Status Transition ============
+
+@app.post("/issues/{issue_id}/transition", response_model=schemas.IssueResponse)
+def transition_issue(issue_id: int, new_status: str, bg: BackgroundTasks, db: Session = Depends(get_db)):
+    """Transition issue status with validation and webhook."""
+    valid_statuses = ["open", "in_progress", "resolved", "closed", "blocked"]
+    if new_status not in valid_statuses:
+        raise HTTPException(status_code=400, detail=f"Invalid status. Must be one of: {valid_statuses}")
+    
+    issue = db.query(models.Issue).filter(models.Issue.id == issue_id).first()
+    if not issue:
+        raise HTTPException(status_code=404, detail="Issue not found")
+    
+    old_status = issue.status
+    issue.status = new_status
+    db.commit()
+    db.refresh(issue)
+    
+    event = "issue.closed" if new_status == "closed" else "issue.updated"
+    bg.add_task(fire_webhooks_sync, event, {
+        "issue_id": issue.id,
+        "title": issue.title,
+        "old_status": old_status,
+        "new_status": new_status,
+    }, issue.project_id, db)
+    
+    return issue