fix(sdk): emit replacement chat projection deltas

Co-authored-by: openclaw-clawsweeper[bot] <280122609+openclaw-clawsweeper[bot]@users.noreply.github.com>

packages/sdk/src/client.ts

@@ -219,15 +219,23 @@ function isTerminalRunEvent(event: OpenClawEvent): boolean {
 function normalizeChatProjectionEvent(
   event: OpenClawEvent,
   projection: ChatProjection,
+  previousText: string | undefined,
 ): OpenClawEvent {
   const text = readChatProjectionText(projection.payload);
+  const isReplacement = Boolean(
+    previousText && text !== undefined && !text.startsWith(previousText),
+  );
   return {
     ...event,
     type: projection.state === "delta" ? "assistant.delta" : "run.completed",
     data:
       projection.state === "delta"
         ? text !== undefined
-          ? { delta: text }
+          ? {
+              text,
+              delta: isReplacement ? text : text.slice(previousText?.length ?? 0),
+              ...(isReplacement ? { replace: true } : {}),
+            }
           : event.data
         : { phase: "end", ...(text !== undefined ? { outputText: text } : {}) },
   };
@@ -335,20 +343,30 @@ export class OpenClaw {
     const replayEvents = this.replaySnapshot(runId);
     let hasCanonicalAssistantRunEvent = replayEvents.some(isAssistantRunEvent);
     let hasTerminalRunEvent = replayEvents.some(isTerminalRunEvent);
+    let previousChatProjectionText: string | undefined;
     const toRunStreamEvent = (event: OpenClawEvent): OpenClawEvent | undefined => {
       const chatProjection = readChatProjection(event);
       if (chatProjection?.state === "delta") {
         if (hasCanonicalAssistantRunEvent) {
           return undefined;
         }
-        return normalizeChatProjectionEvent(event, chatProjection);
+        const runEvent = normalizeChatProjectionEvent(
+          event,
+          chatProjection,
+          previousChatProjectionText,
+        );
+        const text = readChatProjectionText(chatProjection.payload);
+        if (text !== undefined) {
+          previousChatProjectionText = text;
+        }
+        return runEvent;
       }
       if (chatProjection?.state === "final") {
         if (hasTerminalRunEvent) {
           return undefined;
         }
         hasTerminalRunEvent = true;
-        return normalizeChatProjectionEvent(event, chatProjection);
+        return normalizeChatProjectionEvent(event, chatProjection, previousChatProjectionText);
       }
       if (isAssistantRunEvent(event)) {
         hasCanonicalAssistantRunEvent = true;

packages/sdk/src/index.test.ts

@@ -499,20 +499,34 @@ describe("OpenClaw SDK", () => {
           payload: {
             runId: "run_chat_only",
             sessionKey: "chat-only",
-            state: "final",
+            state: "delta",
             message: {
               role: "assistant",
-              content: [{ type: "text", text: "hello again" }],
+              content: [{ type: "text", text: "reset" }],
               timestamp: ts + 2,
             },
           },
         });
         fake.emit({
-          event: "custom.debug",
+          event: "chat",
           seq: 4,
           payload: {
             runId: "run_chat_only",
-            ts: ts + 3,
+            sessionKey: "chat-only",
+            state: "final",
+            message: {
+              role: "assistant",
+              content: [{ type: "text", text: "reset" }],
+              timestamp: ts + 3,
+            },
+          },
+        });
+        fake.emit({
+          event: "custom.debug",
+          seq: 5,
+          payload: {
+            runId: "run_chat_only",
+            ts: ts + 4,
             data: { ok: true },
           },
         });
@@ -534,7 +548,7 @@ describe("OpenClaw SDK", () => {
         done: false,
         value: {
           type: "assistant.delta",
-          data: { delta: "hello" },
+          data: { text: "hello", delta: "hello" },
           raw: { event: "chat" },
         },
       });
@@ -544,17 +558,27 @@ describe("OpenClaw SDK", () => {
         done: false,
         value: {
           type: "assistant.delta",
-          data: { delta: "hello again" },
+          data: { text: "hello again", delta: " again" },
           raw: { event: "chat" },
         },
       });
 
       const third = await iterator.next();
       expect(third).toMatchObject({
+        done: false,
+        value: {
+          type: "assistant.delta",
+          data: { text: "reset", delta: "reset", replace: true },
+          raw: { event: "chat" },
+        },
+      });
+
+      const fourth = await iterator.next();
+      expect(fourth).toMatchObject({
         done: false,
         value: {
           type: "run.completed",
-          data: { phase: "end", outputText: "hello again" },
+          data: { phase: "end", outputText: "reset" },
           raw: { event: "chat" },
         },
       });