diff --git a/packages/stage-pages/src/pages/devtools/io-tracer/components/io-tracer-chart.vue b/packages/stage-pages/src/pages/devtools/io-tracer/components/io-tracer-chart.vue
index 7ebfea7e1..12a6631fe 100644
--- a/packages/stage-pages/src/pages/devtools/io-tracer/components/io-tracer-chart.vue
+++ b/packages/stage-pages/src/pages/devtools/io-tracer/components/io-tracer-chart.vue
@@ -466,10 +466,10 @@ function autoFit() {
   hasUserInteracted = false
 }
 
-watch(() => props.turns, () => {
-  if (visibleSpans.value.length > 0 && !hasUserInteracted)
+watch(() => visibleSpans.value.length, (count) => {
+  if (count > 0 && !hasUserInteracted)
     autoFit()
-}, { deep: false })
+})
 
 defineExpose({ autoFit })
 
@@ -491,12 +491,7 @@ function spanDuration(span: IOSpan): string {
 
 function spanLabel(span: IOSpan): string {
   const subsystemLabel = SUBSYSTEM_CONFIG_MAP.get(span.subsystem)?.label ?? ''
-  const text = span.meta.text
-  if (text && typeof text === 'string') {
-    const short = text.length > 30 ? `${text.slice(0, 30)}…` : text
-    return `${subsystemLabel} · ${short}`
-  }
-  return `${subsystemLabel} · ${span.name}`
+  return `${subsystemLabel} / ${span.name}`
 }
 </script>
 
@@ -818,8 +813,8 @@ function spanLabel(span: IOSpan): string {
         <div v-if="hoveredSpan.span.meta.text" :class="['text-neutral-400 mt-1 break-words']">
           {{ hoveredSpan.span.meta.text.length > 80 ? `${hoveredSpan.span.meta.text.slice(0, 80)}…` : hoveredSpan.span.meta.text }}
         </div>
-        <div v-if="hoveredSpan.span.meta.reason" :class="['text-amber-300/80 mt-0.5']">
-          chunk: {{ hoveredSpan.span.meta.reason }}
+        <div v-if="hoveredSpan.span.meta.chunk_reason" :class="['text-amber-300/80 mt-0.5']">
+          chunk: {{ hoveredSpan.span.meta.chunk_reason }}
         </div>
       </div>
     </Teleport>
diff --git a/packages/stage-shared/src/perf/io-trace.ts b/packages/stage-shared/src/perf/io-trace.ts
index 22e2ebc24..bd23edefb 100644
--- a/packages/stage-shared/src/perf/io-trace.ts
+++ b/packages/stage-shared/src/perf/io-trace.ts
@@ -10,7 +10,6 @@ export const IOSpanNames = {
   InteractionTurn: 'Interaction turn',
   SpeechRecognition: 'Speech recognition',
   LLMInference: 'LLM inference',
-  TTSSegment: 'TTS segment',
   TTSSynthesis: 'TTS synthesis',
   AudioPlayback: 'Audio playback',
 } as const
diff --git a/packages/stage-ui/src/composables/use-io-trace-bridge.ts b/packages/stage-ui/src/composables/use-io-trace-bridge.ts
index dd7ce896a..69c36fcc1 100644
--- a/packages/stage-ui/src/composables/use-io-trace-bridge.ts
+++ b/packages/stage-ui/src/composables/use-io-trace-bridge.ts
@@ -2,66 +2,29 @@ import type { Span } from '@opentelemetry/api'
 import type { createSpeechPipeline } from '@proj-airi/pipelines-audio'
 
 import { IOAttributes, IOSpanNames, IOSubsystems } from '@proj-airi/stage-shared'
-import { onScopeDispose, watch } from 'vue'
+import { onScopeDispose } from 'vue'
 
 import { activeTurnSpan, startSpan } from './use-io-tracer'
 
 export function useIOTraceBridge(pipeline: ReturnType<typeof createSpeechPipeline>) {
   const cleanupFns: (() => void)[] = []
 
-  const segmentSpans = new Map<string, Span>()
   const synthesisSpans = new Map<string, Span>()
   const playbackSpans = new Map<string, Span>()
   const segmentReasons = new Map<string, string>()
 
-  let currentParent: Span | undefined
-  let hadSegments = false
-
-  const stopWatch = watch(activeTurnSpan, (newSpan) => {
-    if (newSpan) {
-      currentParent = newSpan
-      hadSegments = false
-    }
-  }, { immediate: true })
-
-  function tryCloseTurn() {
-    if (hadSegments && segmentSpans.size === 0) {
-      activeTurnSpan.value?.end()
-      activeTurnSpan.value = undefined
-    }
-  }
-
-  function closeSegment(segmentId: string) {
-    const segSpan = segmentSpans.get(segmentId)
-    if (segSpan) {
-      segSpan.end()
-      segmentSpans.delete(segmentId)
-    }
-  }
-
   cleanupFns.push(pipeline.on('onSegment', (segment) => {
     segmentReasons.set(segment.segmentId, segment.reason)
   }))
 
   cleanupFns.push(pipeline.on('onTtsRequest', (request) => {
-    let ttsSegmentSpan = segmentSpans.get(request.segmentId)
-    if (!ttsSegmentSpan) {
-      hadSegments = true
-      ttsSegmentSpan = startSpan(IOSpanNames.TTSSegment, currentParent, {
-        [IOAttributes.Subsystem]: IOSubsystems.TTS,
-        [IOAttributes.TTSSegmentId]: request.segmentId,
-        [IOAttributes.TTSText]: request.text,
-        [IOAttributes.TTSChunkReason]: segmentReasons.get(request.segmentId) ?? '',
-      })
-      segmentReasons.delete(request.segmentId)
-      segmentSpans.set(request.segmentId, ttsSegmentSpan)
-    }
-
-    const ttsSynthesisSpan = startSpan(IOSpanNames.TTSSynthesis, ttsSegmentSpan, {
+    const ttsSynthesisSpan = startSpan(IOSpanNames.TTSSynthesis, activeTurnSpan.value, {
       [IOAttributes.Subsystem]: IOSubsystems.TTS,
       [IOAttributes.TTSSegmentId]: request.segmentId,
       [IOAttributes.TTSText]: request.text,
+      [IOAttributes.TTSChunkReason]: segmentReasons.get(request.segmentId) ?? '',
     })
+    segmentReasons.delete(request.segmentId)
     synthesisSpans.set(request.segmentId, ttsSynthesisSpan)
   }))
 
@@ -74,8 +37,7 @@ export function useIOTraceBridge(pipeline: ReturnType<typeof createSpeechPipelin
   }))
 
   cleanupFns.push(pipeline.on('onPlaybackStart', (event) => {
-    const segSpan = segmentSpans.get(event.item.segmentId)
-    const playbackSpan = startSpan(IOSpanNames.AudioPlayback, segSpan, {
+    const playbackSpan = startSpan(IOSpanNames.AudioPlayback, activeTurnSpan.value, {
       [IOAttributes.Subsystem]: IOSubsystems.Playback,
       [IOAttributes.TTSSegmentId]: event.item.segmentId,
       [IOAttributes.TTSText]: event.item.text,
@@ -89,8 +51,6 @@ export function useIOTraceBridge(pipeline: ReturnType<typeof createSpeechPipelin
       playbackSpan.end()
       playbackSpans.delete(event.item.segmentId)
     }
-    closeSegment(event.item.segmentId)
-    tryCloseTurn()
   }))
 
   cleanupFns.push(pipeline.on('onPlaybackInterrupt', (event) => {
@@ -101,34 +61,22 @@ export function useIOTraceBridge(pipeline: ReturnType<typeof createSpeechPipelin
       playbackSpan.end()
       playbackSpans.delete(event.item.segmentId)
     }
-    closeSegment(event.item.segmentId)
-    tryCloseTurn()
-  }))
-
-  cleanupFns.push(pipeline.on('onPlaybackReject', (event) => {
-    closeSegment(event.item.segmentId)
-    tryCloseTurn()
   }))
 
   cleanupFns.push(pipeline.on('onIntentCancel', () => {
-    for (const [segmentId, span] of segmentSpans) {
-      span.setAttribute(IOAttributes.TTSCanceled, true)
-      span.end()
-      segmentSpans.delete(segmentId)
-    }
     for (const [segmentId, span] of synthesisSpans) {
+      span.setAttribute(IOAttributes.TTSCanceled, true)
       span.end()
       synthesisSpans.delete(segmentId)
     }
     for (const [segmentId, span] of playbackSpans) {
+      span.setAttribute(IOAttributes.TTSCanceled, true)
       span.end()
       playbackSpans.delete(segmentId)
     }
-    tryCloseTurn()
   }))
 
   onScopeDispose(() => {
-    stopWatch()
     for (const cleanup of cleanupFns)
       cleanup()
   })
diff --git a/packages/stage-ui/src/stores/chat.ts b/packages/stage-ui/src/stores/chat.ts
index 5c0f8def2..98eb523d4 100644
--- a/packages/stage-ui/src/stores/chat.ts
+++ b/packages/stage-ui/src/stores/chat.ts
@@ -449,23 +449,19 @@ export const useChatOrchestratorStore = defineStore('chat-orchestrator', () => {
         toolCalls: sessionMessagesForSend.filter(msg => msg.role === 'tool') as ToolMessage[],
       }, streamingMessageContext)
 
-      // TODO: Close turn span for zero-segment responses (tool-only, empty).
-      // Currently the bridge's tryCloseTurn() only fires after TTS playback,
-      // so turns without segments stay open until the next interaction.
-
       if (isForegroundSession()) {
         streamingMessage.value = { role: 'assistant', content: '', slices: [], tool_results: [] }
       }
     }
     catch (error) {
-      if (!hadExistingTurn && activeTurnSpan.value) {
-        activeTurnSpan.value.end()
-        activeTurnSpan.value = undefined
-      }
       console.error('Error sending message:', error)
       throw error
     }
     finally {
+      if (!hadExistingTurn && activeTurnSpan.value) {
+        activeTurnSpan.value.end()
+        activeTurnSpan.value = undefined
+      }
       sending.value = false
     }
   }
diff --git a/packages/stage-ui/src/stores/devtools/io-tracer.ts b/packages/stage-ui/src/stores/devtools/io-tracer.ts
index e8334bdd8..75cab71e2 100644
--- a/packages/stage-ui/src/stores/devtools/io-tracer.ts
+++ b/packages/stage-ui/src/stores/devtools/io-tracer.ts
@@ -111,16 +111,17 @@ export const useIOTracerStore = defineStore('devtools:io-tracer', () => {
     const subsystem = readable.attributes[IOAttributes.Subsystem] as IOSubsystem | undefined
 
     if (!subsystem) {
-      if (readable.name === IOSpanNames.TTSSegment) {
-        const turn = getOrCreateTurn()
-        const text = readable.attributes[IOAttributes.TTSText]
-        if (typeof text === 'string' && !turn.outputText)
-          turn.outputText = text
-      }
       notifyUpdate()
       return
     }
 
+    if (readable.name === IOSpanNames.TTSSynthesis) {
+      const turn = getOrCreateTurn()
+      const text = readable.attributes[IOAttributes.TTSText]
+      if (typeof text === 'string' && !turn.outputText)
+        turn.outputText = text
+    }
+
     const turn = getOrCreateTurn()
     const meta = attrsToMeta(readable.attributes)