feat(web): turn speed metrics and composer context meter

Assistant footers and the stats line gain TTFT/tok-per-second readings
folded from step timings; context occupancy moves off the stats line onto
a composer ring whose panel shows a heuristic system/tools/messages
breakdown from the new token-meter contextBreakdown session projection.

packages/client/runtime/src/client/session-history/history-fold.ts

@@ -16,6 +16,8 @@ import type {
 } from '../sessions/conversation-context.ts'
 import type { ConversationPromptSnapshot } from '../sessions/request-inspection.ts'
 import { PartialAccumulator } from '../sessions/partial.ts'
+import type { AssistantStepMetadata } from '../sessions/assistant-timing.ts'
+import { indexAssistantStepTiming, settledAssistantTiming } from '../sessions/assistant-timing.ts'
 
 interface CallIndexEntry {
   name: string
@@ -30,11 +32,6 @@ interface FoldedContext {
   originSeq?: number
 }
 
-interface AssistantStepMetadata {
-  stepStartTime: number | null
-  firstTokenTime: number | null
-}
-
 /** Immutable conversation projections derived only from the history source. */
 export interface ConversationHistoryProjection {
   eventNodes: readonly ConversationNode[]
@@ -45,10 +42,6 @@ export interface ConversationHistoryProjection {
   codeDispatches: ReadonlyMap<string, readonly CodeSubCall[]>
 }
 
-function assistantStepKey(turn: number, step: number): string {
-  return `${turn}\u0000${step}`
-}
-
 // Trajectory owns surface-window reconstruction so its immutable ledger does
 // not depend on Chat's live fold adapter or Session's mutable state.
 /* jscpd:ignore-start */
@@ -72,18 +65,6 @@ function contextOriginKind(event: SessionEvent | undefined): ConversationContext
   return 'rewrite'
 }
 
-function isTokenDelta(chunk: SessionEvent<'assistant/chunk'>['data']['chunk']): boolean {
-  switch (chunk.type) {
-    case 'text-delta':
-    case 'reasoning-delta':
-      return chunk.text !== ''
-    case 'tool-call-delta':
-      return chunk.argumentsDelta !== '' || chunk.name !== undefined
-    default:
-      return false
-  }
-}
-
 function foldContexts(events: readonly SessionEvent[]): readonly FoldedContext[] {
   const replay: SessionEvent[] = []
   const surface = new SurfaceManager(replay)
@@ -362,6 +343,7 @@ export function projectConversationHistory(
       contextGeneration++
       if (activePrompt !== undefined) promptsByContext.set(contextGeneration, activePrompt)
     }
+    indexAssistantStepTiming(assistantSteps, event)
     if (event.type === 'request/header') {
       activeRequestConfig = event.data.header.config
       activePrompt = {
@@ -370,30 +352,10 @@ export function projectConversationHistory(
         tools: event.data.header.tools ?? [],
       }
       promptsByContext.set(contextGeneration, activePrompt)
-    } else if (event.type === 'step/start') {
-      assistantSteps.set(
-        assistantStepKey(event.data.turn, event.data.step),
-        { stepStartTime: event.time, firstTokenTime: null },
-      )
-    } else if (event.type === 'assistant/chunk' && isTokenDelta(event.data.chunk)) {
-      const key = assistantStepKey(event.data.turn, event.data.step)
-      const current = assistantSteps.get(key) ?? {
-        stepStartTime: null,
-        firstTokenTime: null,
-      }
-      if (current.firstTokenTime === null) {
-        assistantSteps.set(key, { ...current, firstTokenTime: event.time })
-      }
     } else if (event.type === 'assistant/message') {
       assistantTimings.set(
         event.seq,
-        {
-          ...(assistantSteps.get(assistantStepKey(event.data.turn, event.data.step)) ?? {
-            stepStartTime: null,
-            firstTokenTime: null,
-          }),
-          completedTime: event.time,
-        },
+        settledAssistantTiming(assistantSteps, event.data.turn, event.data.step, event.time),
       )
       if (activeRequestConfig !== undefined) {
         assistantRequestConfigs.set(event.seq, activeRequestConfig)

packages/client/runtime/src/client/sessions/assistant-timing.ts

@@ -0,0 +1,84 @@
+// Shared assistant step-timing fold: both transcript projections (the live
+// window adapter and the trajectory history fold) derive AssistantTiming from
+// the same step/start -> first token delta -> assistant/message sequence, so
+// the derivation lives once here instead of drifting per projection.
+
+import type { SessionEvent } from '@deepseek-ai/dsh-session/types'
+import type { AssistantTiming } from './conversation.ts'
+
+/** Pre-finalize timing boundaries for one assistant step (start + first token). */
+export interface AssistantStepMetadata {
+  stepStartTime: number | null
+  firstTokenTime: number | null
+}
+
+/**
+ * Composite map key for one assistant step.
+ * @param turn - turn number from the event payload.
+ * @param step - step number from the event payload.
+ * @returns collision-free `turn`/`step` key (NUL separator).
+ */
+export function assistantStepKey(turn: number, step: number): string {
+  return `${turn}\u0000${step}`
+}
+
+/**
+ * Whether a chunk carries visible model output (first-token boundary). Empty
+ * deltas (heartbeats, empty tool-call frames) do not count as a first token.
+ * @param chunk - the assistant/chunk payload.
+ * @returns true when the chunk contains a non-empty text/reasoning/tool delta.
+ */
+export function isTokenDelta(chunk: SessionEvent<'assistant/chunk'>['data']['chunk']): boolean {
+  switch (chunk.type) {
+    case 'text-delta':
+    case 'reasoning-delta':
+      return chunk.text !== ''
+    case 'tool-call-delta':
+      return chunk.argumentsDelta !== '' || chunk.name !== undefined
+    default:
+      return false
+  }
+}
+
+/**
+ * Fold one event into the per-step timing index: step/start opens the entry,
+ * the first non-empty token delta stamps first-token time once. Other event
+ * types are no-ops.
+ * @param steps - the mutable per-step index, keyed by {@link assistantStepKey}.
+ * @param event - the raw window event.
+ */
+export function indexAssistantStepTiming(steps: Map<string, AssistantStepMetadata>, event: SessionEvent): void {
+  if (event.type === 'step/start') {
+    steps.set(
+      assistantStepKey(event.data.turn, event.data.step),
+      { stepStartTime: event.time, firstTokenTime: null },
+    )
+  } else if (event.type === 'assistant/chunk' && isTokenDelta(event.data.chunk)) {
+    const key = assistantStepKey(event.data.turn, event.data.step)
+    const current = steps.get(key) ?? { stepStartTime: null, firstTokenTime: null }
+    if (current.firstTokenTime === null) {
+      steps.set(key, { ...current, firstTokenTime: event.time })
+    }
+  }
+}
+
+/**
+ * Settle one finalized assistant message's timing from its step entry; a step
+ * whose start or first token fell outside the window yields null boundaries.
+ * @param steps - the per-step index built by {@link indexAssistantStepTiming}.
+ * @param turn - the assistant/message turn number.
+ * @param step - the assistant/message step number.
+ * @param completedTime - the assistant/message event timestamp (epoch ms).
+ * @returns the node-ready timing record.
+ */
+export function settledAssistantTiming(
+  steps: ReadonlyMap<string, AssistantStepMetadata>,
+  turn: number,
+  step: number,
+  completedTime: number,
+): AssistantTiming {
+  return {
+    ...(steps.get(assistantStepKey(turn, step)) ?? { stepStartTime: null, firstTokenTime: null }),
+    completedTime,
+  }
+}

packages/client/runtime/src/client/sessions/transcript-adapter.ts

@@ -22,6 +22,8 @@ import type { COMPACT_CHECKPOINT_SOURCE } from '@deepseek-ai/dsh-compact/checkpo
 import type { ToolCallView, ToolEventView, ToolResultView } from '@deepseek-ai/dsh-client-connection/client'
 import type { CommandNode, CompactionSummaryNode, ConversationNode } from './conversation.ts'
 import { toAssistantBlocks } from './conversation.ts'
+import type { AssistantStepMetadata } from './assistant-timing.ts'
+import { indexAssistantStepTiming, settledAssistantTiming } from './assistant-timing.ts'
 
 /**
  * The compaction seam's checkpoint plugin, pinned to the seam's own declaration
@@ -50,6 +52,7 @@ function materializeNode(
   event: SessionEvent,
   callIndex: ReadonlyMap<string, CallIndexEntry>,
   resultView: ToolResultView | null,
+  stepTimings: ReadonlyMap<string, AssistantStepMetadata>,
 ): ConversationNode {
   switch (event.type) {
     case 'user/message':
@@ -71,6 +74,7 @@ function materializeNode(
         kind: 'assistant', seq: event.seq, time: event.time,
         turn: event.data.turn, step: event.data.step,
         blocks: toAssistantBlocks(event.data.message.content), usage: event.data.usage,
+        timing: settledAssistantTiming(stepTimings, event.data.turn, event.data.step, event.time),
       }
     case 'steering/message':
       return {
@@ -177,6 +181,8 @@ export class TranscriptAdapter {
   /** Transcript nodes in log order; copy-on-write so a published array never mutates. */
   private projected: ConversationNode[] = []
   private callIdx = new Map<string, CallIndexEntry>()
+  /** Per-step timing boundaries (step/start + first token delta), consumed when the step's assistant/message materializes. */
+  private stepTimings = new Map<string, AssistantStepMetadata>()
   /** Wire result views keyed by the tool/result event's seq (views ride the envelope, not the event). */
   private resultViews = new Map<number, ToolResultView>()
   /**
@@ -207,6 +213,7 @@ export class TranscriptAdapter {
     this.callIdx = new Map()
     this.resultViews.clear()
     this.commandIdx = new Map()
+    this.stepTimings = new Map()
     for (let i = 0; i < events.length; i++) {
       const event = events[i]
       /* v8 ignore next -- dense-array guard: i stays within events.length, so the undefined arm needs a sparse array no caller builds. */
@@ -214,6 +221,7 @@ export class TranscriptAdapter {
       this.eventIndex.set(event.seq, event)
       this.indexCall(event, views?.[i])
       this.indexCommand(event)
+      indexAssistantStepTiming(this.stepTimings, event)
     }
     // Indexes first, then project: a tool/result materializes against the
     // complete call index, and a checkpoint against the complete event index.
@@ -236,6 +244,7 @@ export class TranscriptAdapter {
   append(event: SessionEvent, view?: ToolEventView): void {
     this.eventIndex.set(event.seq, event)
     this.indexCall(event, view)
+    indexAssistantStepTiming(this.stepTimings, event)
     if (this.indexCommand(event)) this.rev++
     if (!isTranscriptEvent(event)) return
     this.projected = [...this.projected, this.materialize(event)]
@@ -274,7 +283,7 @@ export class TranscriptAdapter {
   private materialize(event: SessionEvent): ConversationNode {
     return isCompactCheckpoint(event)
       ? materializeCompaction(event, this.eventIndex)
-      : materializeNode(event, this.callIdx, this.resultViews.get(event.seq) ?? null)
+      : materializeNode(event, this.callIdx, this.resultViews.get(event.seq) ?? null, this.stepTimings)
   }
 
   /**

packages/client/runtime/tests/transcript-adapter.spec.ts

@@ -415,4 +415,48 @@ describe('TranscriptAdapter', () => {
       expect(nodes[1]).toMatchObject({ name: 'compact', outcome: { kind: 'success', text: '已压缩' } })
     })
   })
+
+  describe('assistant timing', () => {
+    const base = 1_700_000_000_000
+
+    it('derives step timing across a window rebuild (start + first token + completion)', () => {
+      const adapter = new TranscriptAdapter()
+      adapter.reset([
+        ev.turnStart(0, 0),
+        ev.user(1, '问'),
+        ev.stepStart(2, 0),
+        ev.chunkStart(3, 0),
+        ev.chunkText(4, 0, '答'),
+        ev.chunkText(5, 0, '案'),
+        ev.assistant(6, 0, '答案'),
+        ev.turnEnd(7, 0),
+      ])
+      const assistant = adapter.nodes().find(n => n.kind === 'assistant')
+      expect(assistant).toMatchObject({
+        timing: { stepStartTime: base + 2, firstTokenTime: base + 4, completedTime: base + 6 },
+      })
+    })
+
+    it('derives the same timing on the live append path, first token winning once', () => {
+      const adapter = new TranscriptAdapter()
+      adapter.reset([ev.user(0, '问')])
+      adapter.append(ev.stepStart(1, 0))
+      adapter.append(ev.chunkText(2, 0, '首'))
+      adapter.append(ev.chunkText(3, 0, '次'))
+      adapter.append(ev.assistant(4, 0, '首次'))
+      const assistant = adapter.nodes().find(n => n.kind === 'assistant')
+      expect(assistant).toMatchObject({
+        timing: { stepStartTime: base + 1, firstTokenTime: base + 2, completedTime: base + 4 },
+      })
+    })
+
+    it('soft-falls to null boundaries when the step opening fell outside the window', () => {
+      const adapter = new TranscriptAdapter()
+      adapter.reset([ev.assistant(100, 0, '被切窗的答案')])
+      const assistant = adapter.nodes().find(n => n.kind === 'assistant')
+      expect(assistant).toMatchObject({
+        timing: { stepStartTime: null, firstTokenTime: null, completedTime: base + 100 },
+      })
+    })
+  })
 })