refactor: streamline TUI stream assembly updates

src/tui/tui-formatters.test.ts

@@ -87,4 +87,14 @@ describe("extractContentFromMessage", () => {
 
     expect(text).toBe("hello");
   });
+
+  it("renders error text when stopReason is error and content is not an array", () => {
+    const text = extractContentFromMessage({
+      role: "assistant",
+      stopReason: "error",
+      errorMessage: '429 {"error":{"message":"rate limit"}}',
+    });
+
+    expect(text).toContain("HTTP 429");
+  });
 });

src/tui/tui-stream-assembler.test.ts

@@ -65,4 +65,29 @@ describe("TuiStreamAssembler", () => {
 
     expect(finalText).toBe("Streamed");
   });
+
+  it("returns null when delta text is unchanged", () => {
+    const assembler = new TuiStreamAssembler();
+    const first = assembler.ingestDelta(
+      "run-4",
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "Repeat" }],
+      },
+      false,
+    );
+
+    expect(first).toBe("Repeat");
+
+    const second = assembler.ingestDelta(
+      "run-4",
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "Repeat" }],
+      },
+      false,
+    );
+
+    expect(second).toBeNull();
+  });
 });

src/tui/tui-stream-assembler.ts

@@ -27,10 +27,9 @@ export class TuiStreamAssembler {
     return state;
   }
 
-  ingestDelta(runId: string, message: unknown, showThinking: boolean): string | null {
+  private updateRunState(state: RunStreamState, message: unknown, showThinking: boolean) {
     const thinkingText = extractThinkingFromMessage(message);
     const contentText = extractContentFromMessage(message);
-    const state = this.getOrCreateRun(runId);
 
     if (thinkingText) {
       state.thinkingText = thinkingText;
@@ -45,29 +44,23 @@ export class TuiStreamAssembler {
       showThinking,
     });
 
-    if (!displayText || displayText === state.displayText) return null;
-
     state.displayText = displayText;
-    return displayText;
+  }
+
+  ingestDelta(runId: string, message: unknown, showThinking: boolean): string | null {
+    const state = this.getOrCreateRun(runId);
+    const previousDisplayText = state.displayText;
+    this.updateRunState(state, message, showThinking);
+
+    if (!state.displayText || state.displayText === previousDisplayText) return null;
+
+    return state.displayText;
   }
 
   finalize(runId: string, message: unknown, showThinking: boolean): string {
     const state = this.getOrCreateRun(runId);
-    const thinkingText = extractThinkingFromMessage(message);
+    this.updateRunState(state, message, showThinking);
-    const contentText = extractContentFromMessage(message);
+    const finalComposed = state.displayText;
-
-    if (thinkingText) {
-      state.thinkingText = thinkingText;
-    }
-    if (contentText) {
-      state.contentText = contentText;
-    }
-
-    const finalComposed = composeThinkingAndContent({
-      thinkingText: state.thinkingText,
-      contentText: state.contentText,
-      showThinking,
-    });
     const finalText = resolveFinalAssistantText({
       finalText: finalComposed,
       streamedText: state.displayText,