diff --git a/packages/stage-shared/src/index.ts b/packages/stage-shared/src/index.ts
index 703d521fb..638c77377 100644
--- a/packages/stage-shared/src/index.ts
+++ b/packages/stage-shared/src/index.ts
@@ -1,6 +1,7 @@
 export * from './env-vars'
 export * from './environment'
 export * from './export-csv'
+export * from './perf/io-trace'
 export * from './perf/tracer'
 export * from './url'
 export * from './window'
diff --git a/packages/stage-shared/src/perf/io-trace.ts b/packages/stage-shared/src/perf/io-trace.ts
new file mode 100644
index 000000000..6b65beca7
--- /dev/null
+++ b/packages/stage-shared/src/perf/io-trace.ts
@@ -0,0 +1,31 @@
+export const IOSubsystems = {
+  ASR: 'asr',
+  LLM: 'llm',
+  TTSChunking: 'tts-chunking',
+  TTSSynthesis: 'tts-synthesis',
+  Playback: 'playback',
+} as const
+
+export type IOSubsystem = (typeof IOSubsystems)[keyof typeof IOSubsystems]
+
+export interface IOSpan {
+  id: string
+  traceId: string
+  parentSpanId?: string
+  startTs: number
+  endTs?: number
+
+  ttsCorrelationId?: string
+  subsystem: IOSubsystem
+  name: string
+  meta: Record<string, any>
+}
+
+export interface IOTurn {
+  id: string
+  startTs: number
+  endTs?: number
+  inputText?: string
+  outputText?: string
+  spans: IOSpan[]
+}