#112411

SyntaxError: Invalid JSON Response in frontend-web

Error

Events

Users2

Error Frequency

Event

Occurrence First Recent Recommended

JSON

Markdown

{"attachments":null,"browser":null,"device":null,"endpoint_hash":null,"environment":null,"error_type":"SyntaxError","geo_city":null,"geo_country":null,"geo_region":null,"handled":null,"hash":"2453d0d1","is_framework":false,"level":"error","mechanism":"span_status","message":"Unexpected token 'u', \"upstream c\"... is not valid JSON","os":null,"parent_hash":"36b73825","parent_span_id":"f8a973cfe897f652","project_id":"00000000-0000-0000-0000-000000000000","release":null,"request_headers":null,"request_method":null,"request_path":null,"root_error_message":"Unexpected token 'u', \"upstream c\"... is not valid JSON","root_error_type":"SyntaxError","runtime":null,"service_name":"frontend-web","session_id":null,"shape_hash":"4c41b620","span_id":"a9a82073dd90aed6","stack_trace":"SyntaxError: Unexpected token 'u', \"upstream c\"... is not valid JSON\n    at JSON.parse (<anonymous>)\n    at f (http://frontend-proxy:8080/_next/static/chunks/0zzy1y99582vs.js:1:70798)","technology":null,"tenant_name":null,"thread_id":null,"thread_name":null,"trace_id":"9cb5b973e7c56efafb951dd3439c8ca8","url_full":null,"url_query":null,"user_agent":null,"user_email":null,"user_id":"121743b5-da9a-4744-9ad5-af1dda0d9cd0","user_ip":null,"user_name":null,"when":"2026-10-04T12:57:56.967Z"}

## SyntaxError: Invalid JSON Response in frontend-web

- Type: runtime_exception
- Severity: info
- Service: frontend-web

```
SyntaxError: Unexpected token 'u', "upstream c"... is not valid JSON
SyntaxError: Unexpected token 'u', "upstream c"... is not valid JSON
    at JSON.parse (<anonymous>)
    at f (http://frontend-proxy:8080/_next/static/chunks/0zzy1y99582vs.js:1:70798)
```

Jump to:Highlights Contexts Stack trace Tags Event grouping Trace Logs All events Session replay

Highlights

level: error
trace.id: 9cb5b973e7c56efafb951dd3439c8ca8

Contexts

User

id: 121743b5-da9a-4744-9ad5-af1dda0d9cd0

Runtime

service: frontend-web
mechanism: span_status

Trace

trace.id: 9cb5b973e7c56efafb951dd3439c8ca8
span.id: a9a82073dd90aed6
parent_span.id: f8a973cfe897f652

Stack trace

Error message

Unexpected token 'u', "upstream c"... is not valid JSON

c"...SyntaxError: Unexpected token 'u', "upstream c"... is not valid JSON

JSON.parseat JSON.parse (<anonymous>)

at f (http://frontend-proxy:8080/_next/static/chunks/0zzy1y99582vs.js:1:70798):1

Raw

SyntaxError: Unexpected token 'u', "upstream c"... is not valid JSON
    at JSON.parse (<anonymous>)
    at f (http://frontend-proxy:8080/_next/static/chunks/0zzy1y99582vs.js:1:70798)

Event grouping

Events join this issue when their fingerprint matches: the error type, the message with volatile parts (ids, numbers, hex) replaced, the service, the span name, and the in-app frames.