Fix router block

Author: Sg312

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/components/sub-block/components/condition-input/condition-input.tsx

@@ -654,16 +654,19 @@ export function ConditionInput({
   }
 
   const removeBlock = (id: string) => {
-    if (isPreview || disabled || conditionalBlocks.length <= 2) return
+    if (isPreview || disabled) return
+    // Condition mode requires at least 2 blocks (if/else), router mode requires at least 1
+    const minBlocks = isRouterMode ? 1 : 2
+    if (conditionalBlocks.length <= minBlocks) return
 
     // Remove any associated edges before removing the block
+    const handlePrefix = isRouterMode ? `router-${id}` : `condition-${id}`
     edges.forEach((edge) => {
-      if (edge.sourceHandle?.startsWith(`condition-${id}`)) {
+      if (edge.sourceHandle?.startsWith(handlePrefix)) {
         removeEdge(edge.id)
       }
     })
 
-    if (conditionalBlocks.length === 1) return
     shouldPersistRef.current = true
     setConditionalBlocks((blocks) => updateBlockTitles(blocks.filter((block) => block.id !== id)))
 
@@ -815,7 +818,11 @@ export function ConditionInput({
                   <Button
                     variant='ghost'
                     onClick={() => removeBlock(block.id)}
-                    disabled={isPreview || disabled || conditionalBlocks.length === 1}
+                    disabled={
+                      isPreview ||
+                      disabled ||
+                      conditionalBlocks.length <= (isRouterMode ? 1 : 2)
+                    }
                     className='h-auto p-0 text-[var(--text-error)] hover:text-[var(--text-error)]'
                   >
                     <Trash className='h-[14px] w-[14px]' />

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-block/workflow-block.tsx

@@ -863,7 +863,8 @@ export const WorkflowBlock = memo(function WorkflowBlock({
           return parsed.map((item: unknown, index: number) => {
             const routeItem = item as { id?: string; value?: string }
             return {
-              id: routeItem?.id ?? `${id}-route-${index}`,
+              // Use stable ID format that matches ConditionInput's generateStableId
+              id: routeItem?.id ?? `${id}-route${index + 1}`,
               value: routeItem?.value ?? '',
             }
           })
@@ -873,7 +874,8 @@ export const WorkflowBlock = memo(function WorkflowBlock({
       logger.warn('Failed to parse router routes value', { error, blockId: id })
     }
 
-    return [{ id: `${id}-route-route1`, value: '' }]
+    // Fallback must match ConditionInput's default: generateStableId(blockId, 'route1') = `${blockId}-route1`
+    return [{ id: `${id}-route1`, value: '' }]
   }, [type, subBlockState, id])
 
   /**

apps/sim/blocks/blocks/router.ts

@@ -115,25 +115,29 @@ Description: ${route.value || 'No description provided'}
     )
     .join('\n')
 
-  return `You are an intelligent routing agent. Your task is to analyze the provided context and select the most appropriate route from the available options.
+  return `You are a DETERMINISTIC routing agent. You MUST select exactly ONE route. There is NO other option.
+
+CRITICAL RULES:
+- You MUST output a route ID. Period.
+- You CANNOT say "I need more information"
+- You CANNOT refuse to choose
+- You CANNOT explain your reasoning
+- You CANNOT ask questions
+- You CANNOT output anything except a route ID
+- There is ALWAYS a best option. Pick it.
 
 Available Routes:
 ${routesInfo}
 
-Context to analyze:
+Context:
 ${context}
 
-Instructions:
-1. Carefully analyze the context against each route's description
-2. Select the route that best matches the context's intent and requirements
-3. Consider the semantic meaning, not just keyword matching
-4. If multiple routes could match, choose the most specific one
-
-Response Format:
-Return ONLY the route ID as a single string, no punctuation, no explanation.
-Example: "route-abc123"
+MANDATORY BEHAVIOR:
+1. Analyze the context against each route description
+2. ALWAYS pick the BEST matching route - one route is always better than the others
+3. Output ONLY the route ID - nothing else
 
-Remember: Your response must be ONLY the route ID - no additional text, formatting, or explanation.`
+Your response must be EXACTLY one route ID from the list above. No punctuation. No explanation. No refusal. Just the ID.`
 }
 
 /**

apps/sim/executor/handlers/router/router-handler.ts

@@ -273,14 +273,15 @@ export class RouterBlockHandler implements BlockHandler {
       const result = await response.json()
 
       const chosenRouteId = result.content.trim()
-      const chosenRoute = routes.find((r) => r.id === chosenRouteId)
+      let chosenRoute = routes.find((r) => r.id === chosenRouteId)
 
+      // Fallback to first route if LLM returns invalid route ID
       if (!chosenRoute) {
-        logger.error(
-          `Invalid routing decision. Response content: "${result.content}", available routes:`,
+        logger.warn(
+          `Invalid routing decision. Response content: "${result.content}", falling back to first route. Available routes:`,
           routes.map((r) => ({ id: r.id, title: r.title }))
         )
-        throw new Error(`Invalid routing decision: ${chosenRouteId}`)
+        chosenRoute = routes[0]
       }
 
       // Find the target block connected to this route's handle