core: split message part updates into delta events for smoother streaming

Streaming text and reasoning content now uses incremental delta events instead of sending full message parts on each update. This reduces bandwidth and improves real-time response smoothness in the TUI.
2026-01-30 11:13:16 -05:00
parent d6fbd255b6
commit 498cbb2c26
7 changed files with 147 additions and 63 deletions
@@ -299,6 +299,24 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
          break
        }

+        case "message.part.delta": {
+          const parts = store.part[event.properties.messageID]
+          if (!parts) break
+          const result = Binary.search(parts, event.properties.partID, (p) => p.id)
+          if (!result.found) break
+          setStore(
+            "part",
+            event.properties.messageID,
+            produce((draft) => {
+              const part = draft[result.index]
+              const field = event.properties.field as keyof typeof part
+              const existing = part[field] as string | undefined
+              ;(part[field] as string) = (existing ?? "") + event.properties.delta
+            }),
+          )
+          break
+        }
+
        case "message.part.removed": {
          const parts = store.part[event.properties.messageID]
          const result = Binary.search(parts, event.properties.partID, (p) => p.id)