Optionalseed: stringA seed string for deterministic trace ID generation. If provided (non-empty), the same seed will always generate the same trace ID. If empty or falsy, generates a random trace ID.
Using a seed is especially useful when trying to correlate external,
non-W3C compliant IDs with Langfuse trace IDs. This allows you to later
have a method available for scoring the Langfuse trace given only the
external ID by regenerating the same trace ID from the external ID.
A Promise that resolves to a 32-character lowercase hexadecimal string suitable for use as an OpenTelemetry trace ID.
// Deterministic trace ID from seed
const traceId1 = await createTraceId("my-session-123");
const traceId2 = await createTraceId("my-session-123");
console.log(traceId1 === traceId2); // true
// Random trace ID
const randomId1 = await createTraceId("");
const randomId2 = await createTraceId("");
console.log(randomId1 === randomId2); // false
// Use with spans
const span = startObservation("my-span", {}, {
parentSpanContext: {
traceId: await createTraceId("session-456"),
spanId: "0123456789abcdef",
traceFlags: 1
}
});
// Correlating external IDs with Langfuse traces
const externalId = "ext-12345-67890";
const traceId = await createTraceId(externalId);
// Later, when you need to score this trace, regenerate the same ID
const scoringTraceId = await createTraceId(externalId);
console.log(traceId === scoringTraceId); // true - can now find and score the trace
Creates a trace ID for OpenTelemetry spans.