Function startInteractionSpan

src/utils/telemetry/sessionTracing.ts:176–235

(userPrompt: string)

 * Sets the interaction context for all subsequent operations.
 */
export function startInteractionSpan(userPrompt: string): Span {
  ensureCleanupInterval()

  // Start Perfetto span regardless of OTel tracing state
  const perfettoSpanId = isPerfettoTracingEnabled()
    ? startInteractionPerfettoSpan(userPrompt)
    : undefined

  if (!isAnyTracingEnabled()) {
    // Still track Perfetto span even if OTel is disabled
    if (perfettoSpanId) {
      const dummySpan = trace.getActiveSpan() || getTracer().startSpan('dummy')
      const spanId = getSpanId(dummySpan)
      const spanContextObj: SpanContext = {
        span: dummySpan,
        startTime: Date.now(),
        attributes: {},
        perfettoSpanId,
      }
      activeSpans.set(spanId, new WeakRef(spanContextObj))
      interactionContext.enterWith(spanContextObj)
      return dummySpan
    }
    return trace.getActiveSpan() || getTracer().startSpan('dummy')
  }

  const tracer = getTracer()
  const isUserPromptLoggingEnabled = isEnvTruthy(
    process.env.OTEL_LOG_USER_PROMPTS,
  )
  const promptToLog = isUserPromptLoggingEnabled ? userPrompt : '<REDACTED>'

  interactionSequence++

  const attributes = createSpanAttributes('interaction', {
    user_prompt: promptToLog,
    user_prompt_length: userPrompt.length,
    'interaction.sequence': interactionSequence,
  })

  const span = tracer.startSpan('claude_code.interaction', {
    attributes,
  })

  // Add experimental attributes (new_context)
  addBetaInteractionAttributes(span, userPrompt)

  const spanId = getSpanId(span)
  const spanContextObj: SpanContext = {
    span,
    startTime: Date.now(),
    attributes,
    perfettoSpanId,
  }
  activeSpans.set(spanId, new WeakRef(spanContextObj))

  interactionContext.enterWith(spanContextObj)