{"id":"b9778f4e6389ed8c","repo":"gofiber/fiber","slug":"failed-to-bind-to-response-headers-w","errorCode":null,"errorMessage":"failed to bind to response headers: %w","messagePattern":"failed to bind to response headers: %w","errorType":"http","errorClass":null,"httpStatus":null,"severity":"error","filePath":"middleware/idempotency/idempotency.go","lineNumber":155,"sourceCode":"\t\t} else if ok {\n\t\t\treturn nil\n\t\t}\n\n\t\t// Execute the request handler\n\t\tif err := c.Next(); err != nil {\n\t\t\t// If the request handler returned an error, return it and skip idempotency\n\t\t\treturn err\n\t\t}\n\n\t\t// Construct response\n\t\tres := &response{\n\t\t\tStatusCode: c.Response().StatusCode(),\n\t\t\tBody:       c.Response().Body(),\n\t\t}\n\t\t{\n\t\t\theaders := make(map[string][]string)\n\t\t\tif err := c.Bind().RespHeader(headers); err != nil {\n\t\t\t\treturn fmt.Errorf(\"failed to bind to response headers: %w\", err)\n\t\t\t}\n\n\t\t\tif keepResponseHeaders == nil {\n\t\t\t\t// Keep all\n\t\t\t\tres.Headers = headers\n\t\t\t} else {\n\t\t\t\t// Filter\n\t\t\t\tres.Headers = make(map[string][]string)\n\t\t\t\tfor h, vals := range headers {\n\t\t\t\t\tif shouldKeepHeader(h) {\n\t\t\t\t\t\tres.Headers[h] = vals\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\t// Marshal response\n\t\tbs, err := res.MarshalMsg(nil)","sourceCodeStart":137,"sourceCodeEnd":173,"githubUrl":"https://github.com/gofiber/fiber/blob/9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c/middleware/idempotency/idempotency.go#L137-L173","documentation":"Returned by the middleware (idempotency.go:154-156) when c.Bind().RespHeader(headers) fails while building the cached response. Binding response headers into a map[string][]string rarely fails — it would require an internal fiber/v3 binding error.","triggerScenarios":"Effectively unreachable in normal fiber operation; would require a fiber/v3 regression in the RespHeader binder, or a custom binder override that returns an error.","commonSituations":"Not seen in production. If hit, suspect an incompatible fiber/v3 patch version or a custom Bind implementation.","solutions":["Confirm you are on a compatible fiber/v3 release.","If you overrode the binder via app.NewCtx or custom Bind, validate its RespHeader path.","File an upstream issue — this path should be infallible."],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":"// at startup, exercise the binder path\nh := make(map[string][]string)\n// simulate via a test ctx if available; otherwise pin fiber version","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Pin fiber/v3 to a known-good release in go.mod.","Avoid overriding Bind with custom implementations that can fail.","Treat occurrence as an upstream bug and report it."],"tags":["idempotency","binding","fiber","unreachable"],"analyzedSha":"9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c","analyzedAt":"2026-08-04T21:44:03.395Z","schemaVersion":2}