fix(providers): emit block.start with empty text to avoid duplicate messages

saltbo · Copilot · saltbo · commit 17edc51913df · 2026-04-14T23:16:39.000-04:00
RelayRuntimeProvider's updateOrAppend() searches backwards for a part
with text=="" to fill in on block.done. Copilot was emitting block.start
with full text, causing block.done to find no empty slot and append a
second identical message.

Fix: emit block.start with text="" for text/thinking blocks, and
block.done with the full content — matching the streaming contract
Claude uses.

Co-authored-by: Copilot &lt;223556219+Copilot@users.noreply.github.com&gt;
diff --git a/packages/cli/src/providers/copilot.ts b/packages/cli/src/providers/copilot.ts
@@ -108,9 +108,8 @@ export function* mapCopilotEvent(event: SessionEvent, state: MapState): Generato
     case "assistant.reasoning": {
       const text = event.data.content;
       if (text) {
-        const block: ContentBlock = { type: "thinking", text };
-        yield { type: "block.start", block };
-        yield { type: "block.done", block };
+        yield { type: "block.start", block: { type: "thinking", text: "" } };
+        yield { type: "block.done", block: { type: "thinking", text } };
       }
       return;
     }
@@ -124,15 +123,15 @@ export function* mapCopilotEvent(event: SessionEvent, state: MapState): Generato
       }
 
       if (reasoningText) {
-        const block: ContentBlock = { type: "thinking", text: reasoningText };
-        yield { type: "block.start", block };
-        yield { type: "block.done", block };
+        // block.start with empty text → block.done with full text, matching the streaming
+        // contract that RelayRuntimeProvider expects (it fills in text on block.done)
+        yield { type: "block.start", block: { type: "thinking", text: "" } };
+        yield { type: "block.done", block: { type: "thinking", text: reasoningText } };
       }
 
       if (content) {
-        const block: ContentBlock = { type: "text", text: content };
-        yield { type: "block.start", block };
-        yield { type: "block.done", block };
+        yield { type: "block.start", block: { type: "text", text: "" } };
+        yield { type: "block.done", block: { type: "text", text: content } };
       }
 
       if (toolRequests) {
diff --git a/tests/providers/copilot.test.ts b/tests/providers/copilot.test.ts
@@ -64,7 +64,7 @@ describe("assistant.reasoning", () => {
     const event = { type: "assistant.reasoning", data: { content: "I am thinking" } } as SessionEvent;
     const events = collect(mapCopilotEvent(event, state));
     expect(events).toEqual([
-      { type: "block.start", block: { type: "thinking", text: "I am thinking" } },
+      { type: "block.start", block: { type: "thinking", text: "" } },
       { type: "block.done", block: { type: "thinking", text: "I am thinking" } },
     ]);
   });
@@ -107,7 +107,7 @@ describe("assistant.message with content only", () => {
     const state = makeState({ turnOpen: true });
     const event = { type: "assistant.message", data: { content: "Hello" } } as SessionEvent;
     const events = collect(mapCopilotEvent(event, state));
-    expect(events).toContainEqual({ type: "block.start", block: { type: "text", text: "Hello" } });
+    expect(events).toContainEqual({ type: "block.start", block: { type: "text", text: "" } });
     expect(events).toContainEqual({ type: "block.done", block: { type: "text", text: "Hello" } });
   });
 
@@ -143,7 +143,7 @@ describe("assistant.message with reasoningText and content", () => {
     } as SessionEvent;
     const events = collect(mapCopilotEvent(event, state)) as { type: string; block?: { type: string; text: string } }[];
     const thinkingStart = events.find((e) => e.type === "block.start" && e.block?.type === "thinking");
-    expect(thinkingStart?.block?.text).toBe("Thinking...");
+    expect(thinkingStart?.block?.text).toBe("");
   });
 
   it("emits block.start text with content", () => {
@@ -154,7 +154,7 @@ describe("assistant.message with reasoningText and content", () => {
     } as SessionEvent;
     const events = collect(mapCopilotEvent(event, state)) as { type: string; block?: { type: string; text: string } }[];
     const textStart = events.find((e) => e.type === "block.start" && e.block?.type === "text");
-    expect(textStart?.block?.text).toBe("Answer");
+    expect(textStart?.block?.text).toBe("");
   });
 });
 
