vercel/next.js · error

Unexpected root span type '${rootSpanAttributes.get('next.sp

Error message

Unexpected root span type '${rootSpanAttributes.get('next.span_type')}'. Please report this Next.js issue https://github.com/vercel/next.js

What it means

Post-response telemetry sanity check in Server.handleRequest (base-server.ts): after finishing a request it reads the OTEL root span attributes via tracer.getRootSpanAttributes() and expects next.span_type to be BaseServerSpan.handleRequest. Any other value means tracing instrumentation wrapped the request wrongly (custom tracer setup or nested spans) — a Next.js-internal inconsistency, hence the request to report it.

Source

Thrown at packages/next/src/server/base-server.ts:917

              if (res.statusCode && res.statusCode >= 500) {
                // For 5xx status codes: SHOULD be set to 'Error' span status.
                // x-ref: https://opentelemetry.io/docs/specs/semconv/http/http-spans/#status
                span.setStatus({
                  code: SpanStatusCode.ERROR,
                })
                // For span status 'Error', SHOULD set 'error.type' attribute.
                span.setAttribute('error.type', res.statusCode.toString())
              }

              const rootSpanAttributes = tracer.getRootSpanAttributes()
              // We were unable to get attributes, probably OTEL is not enabled
              if (!rootSpanAttributes) return

              if (
                rootSpanAttributes.get('next.span_type') !==
                BaseServerSpan.handleRequest
              ) {
                console.warn(
                  `Unexpected root span type '${rootSpanAttributes.get(
                    'next.span_type'
                  )}'. Please report this Next.js issue https://github.com/vercel/next.js`
                )
                return
              }

              const route = rootSpanAttributes.get('next.route')
              if (route) {
                const name = isRSCRequest
                  ? `RSC ${method} ${route}`
                  : `${method} ${route}`

                span.setAttributes({
                  'next.route': route,
                  'http.route': route,
                  'next.span_name': name,
                })

View on GitHub (pinned to 258b1c1bc0)

Solutions

1. Report the issue at https://github.com/vercel/next.js with a reproduction; this indicates an internal tracing bug.

When it happens

Trigger: Thrown at packages/next/src/server/base-server.ts:910 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/next.js@258b1c1bc0 (2026-08-19). Data as JSON: /api/errors/e36b4baf09cd8efc. Report an issue: GitHub.