fix: 分页问题

packages/llm/llm/src/message.ts

@@ -2,7 +2,7 @@
 
 import { MessageId, type CallId } from './brand.ts'
 import { deepFreeze } from './call-config.ts'
-import type { ContentBlock, ToolResultBlock } from './types.ts'
+import type { ContentBlock, StreamChunk, ToolResultBlock } from './types.ts'
 
 /** Provider/model identity and adapter-private replay data for an assistant message. */
 export interface AssistantProvenance {
@@ -239,3 +239,23 @@ export function createToolResultMessage(input: ToolResultMessageInput): ToolResu
     }],
   })
 }
+
+/**
+ * Whether a stream chunk carries visible model output (the first-token
+ * boundary shared by client step timing and the whole-log sessionStats
+ * projection). Empty deltas (heartbeats, empty tool-call frames) do not count
+ * as a first token.
+ * @param chunk - the stream chunk to test.
+ * @returns true when the chunk contains a non-empty text/reasoning/tool delta.
+ */
+export function isTokenDelta(chunk: StreamChunk): 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
+  }
+}