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Dify version

1.10.1

Cloud or Self Hosted

Cloud

Steps to reproduce

When running Workflow nodes, the browser console displays a TypeError that crashes the application and prevents proper workflow execution.

Error Details

Error Message:

TypeError: Cannot set properties of undefined (setting 'type')

Stack Trace:

78536-0e29f6099381af25.js:75 Uncaught TypeError: Cannot set properties of undefined (setting 'type') 
     at 78536-0e29f6099381af25.js:75:51800 
     at push.8894.U.constructor.produce (51246-404ebadb6c77138b.js:5:17938) 
     at 78536-0e29f6099381af25.js:75:51784 
     at 78536-0e29f6099381af25.js:75:49953 
     at i8 (2de95d4b-8278ff6b72f9ce97.js:1:135370) 
     at 2de95d4b-8278ff6b72f9ce97.js:1:141456 
     at nz (2de95d4b-8278ff6b72f9ce97.js:1:19204) 
     at sn (2de95d4b-8278ff6b72f9ce97.js:1:136603) 
     at cc (2de95d4b-8278ff6b72f9ce97.js:1:163605) 
     at ci (2de95d4b-8278ff6b72f9ce97.js:1:163427) 

Root Cause Analysis

Issue Location: web/service/base.ts file, handleStream function

Problem: When processing Server-Sent Events (SSE) streams, if the received JSON data is malformed or truncated, JSON parsing fails and bufferObj is set to undefined. However, subsequent code attempts to access properties of bufferObj without checking for null/undefined values first.

Code Context:

try {
  bufferObj = JSON.parse(message.substring(6)) as Record<string, any>
} catch {
  // mute handle message cut off
  bufferObj = undefined
  onData?('', isFirstMessage, {
    conversationId: undefined,
    messageId: '',
  })
  return
}
// Later code without null check:
bufferObj.event // This can cause the error

Steps to Reproduce

1. Create a new Workflow in Dify
2. Add any node type (e.g., LLM, Code node, etc.)
3. Run the workflow node
4. Observe browser console errors

Environment Information

• Component: Web frontend
• Files Affected: web/service/base.ts
• Function: handleStream
• Error Context: Server-Sent Events (SSE) stream processing
• Browser: Any modern browser (Chrome, Firefox, Safari, Edge)

Impact

• Workflow execution fails with JavaScript errors
• Poor user experience with unclear error messages
• Potential data loss or incomplete processing
• Application stability issues

Proposed Fix

Add null/undefined check for bufferObj before accessing its properties:

if (!bufferObj) {
  onData('', false, {
    conversationId: undefined,
    messageId: '',
    errorMessage: 'Invalid response data',
    errorCode: 'invalid_data',
  })
  hasError = true
  onCompleted?.(true, 'Invalid response data')
  return
}

This ensures graceful error handling when encountering malformed JSON data in the SSE stream, preventing the TypeError and providing proper error feedback.

Priority

Severity: Medium
Impact: Workflow functionality
Complexity: Low (simple null check)

✔️ Expected Behavior

The workflow should execute successfully without any JavaScript errors in the browser console. When processing Server-Sent Events (SSE) streams, the application should:

1. Handle well-formed JSON data normally and display workflow results
2. Gracefully handle malformed or truncated JSON data with proper error messages
3. Provide clear feedback to users about any issues that occur during execution
4. Maintain application stability and prevent crashes
5. Allow users to understand what went wrong through meaningful error messages

❌ Actual Behavior

When running workflow nodes, the application encounters a TypeError that crashes the execution:

1. JavaScript Error: Cannot set properties of undefined (setting 'type') appears in browser console
2. Workflow Failure: The workflow execution stops immediately and no results are displayed
3. Poor Error Handling: The error provides no meaningful feedback to users about what went wrong
4. Application Instability: The error may affect other parts of the application or subsequent workflow runs
5. Data Loss Risk: Incomplete processing may result in lost data or partial results