microsoft/typescript-go · error

unknown API method %q

Error message

unknown API method %q

What it means

unmarshalPayload looks the method string up in the server's generated unmarshaler registry; no entry means this server build has never heard of the method. The request fails at payload-decode time and never reaches a handler, so even param-less calls fail.

Source

Thrown at internal/api/proto.go:1454

	return resp
}

// NewDiagnosticResponses converts a slice of ast.Diagnostics to DiagnosticResponses.
func NewDiagnosticResponses(diags []*ast.Diagnostic) []*DiagnosticResponse {
	if len(diags) == 0 {
		return nil
	}
	result := make([]*DiagnosticResponse, len(diags))
	for i, d := range diags {
		result[i] = NewDiagnosticResponse(d)
	}
	return result
}

func unmarshalPayload(method string, payload json.Value) (any, error) {
	unmarshaler, ok := unmarshalers[Method(method)]
	if !ok {
		return nil, fmt.Errorf("unknown API method %q", method)
	}
	return unmarshaler(payload)
}

func unmarshallerFor[T any](data []byte) (any, error) {
	var v T
	if err := json.Unmarshal(data, &v); err != nil {
		return nil, fmt.Errorf("failed to unmarshal %T: %w", (*T)(nil), err)
	}
	return &v, nil
}

func noParams(data []byte) (any, error) {
	return nil, nil
}

View on GitHub (pinned to 1bcfa18d79)

Solutions

1. Check the exact method string against the server's Method constants in proto.go
2. Align client and server to the same typescript-go version
3. After connecting, negotiate capabilities via initialize and only call methods the server supports
4. Trim and normalize method names before sending

Example fix

// before
client.Call(ctx, "getdiagnostics", params) // typo

// after
client.Call(ctx, string(api.MethodGetDiagnostics), params)

var supported = map[string]bool{
	string(api.MethodInitialize): true,
	string(api.MethodGetDiagnostics): true,
	// ... keep in sync with the server build
}
if !supported[method] {
	return fmt.Errorf("method %q not supported by this server build", method)
}
res, err := client.Call(ctx, method, params)

When it happens

Trigger: A client on a newer protocol calling a method this server build doesn't have; a typo'd, renamed, or differently-cased method string; whitespace padding around the method name.

Common situations: Version skew after upgrading the client library but not the server; copy-pasted method names; custom methods not registered server-side.

Related errors

• at node %d (kind %v): %w
• %w: unknown message type: %d
• unknown method: %s
• Unsupported OS: ${os}
• Unsupported ARCH: ${arch}

AI-assisted analysis of microsoft/typescript-go@1bcfa18d79 (2026-08-16). Data as JSON: /api/errors/693462345edeeb72. Report an issue: GitHub.