Fix Codex reasoning summary boundary preservation

src/supervisor/agents/codex/canonicalMapping.test.ts

@@ -1343,12 +1343,43 @@ describe("mapCodexNotification — streaming deltas", () => {
     expect(text[0]).toMatchObject({ type: "content.delta", stream: "reasoning_text" });
     const summary = mapCodexNotification(
       "item/reasoning/summaryTextDelta",
-      { threadId: "x", itemId: "rs-1", delta: "summary" },
+      { threadId: "x", itemId: "rs-1", delta: "summary", summaryIndex: 0 },
       state,
     );
     expect(summary[0]).toMatchObject({ type: "content.delta", stream: "reasoning_text" });
   });
 
+  it("preserves boundaries between indexed reasoning summary parts", () => {
+    const state = createCodexMapperState("t-codex");
+    mapCodexNotification(
+      "item/started",
+      { threadId: "x", itemId: "rs-1", item: { id: "rs-1", type: "reasoning" } },
+      state,
+    );
+
+    const events = [
+      ...mapCodexNotification(
+        "item/reasoning/summaryTextDelta",
+        { threadId: "x", itemId: "rs-1", delta: "**Planning sidebar**", summaryIndex: 0 },
+        state,
+      ),
+      ...mapCodexNotification(
+        "item/reasoning/summaryTextDelta",
+        { threadId: "x", itemId: "rs-1", delta: "**Refining", summaryIndex: 1 },
+        state,
+      ),
+      ...mapCodexNotification(
+        "item/reasoning/summaryTextDelta",
+        { threadId: "x", itemId: "rs-1", delta: " removal**", summaryIndex: 1 },
+        state,
+      ),
+    ];
+
+    expect(
+      events.flatMap((event) => (event.type === "content.delta" ? [event.delta] : [])).join(""),
+    ).toBe("**Planning sidebar**\n\n**Refining removal**");
+  });
+
   it("maps MCP tool progress into the existing tool payload", () => {
     const state = createCodexMapperState("t-codex");
     mapCodexNotification(

src/supervisor/agents/codex/canonicalMapping/dispatch.ts

@@ -91,6 +91,7 @@ export function mapCodexNotification(
     state.commandOutputSeenSet.clear();
     state.fileChangeOutputMap.clear();
     state.fileChangePathMap.clear();
+    state.reasoningSummaryIndexMap.clear();
     return events;
   }
 
@@ -260,6 +261,7 @@ export function mapCodexNotification(
       state.commandOutputSeenSet.delete(codexItemId);
       state.fileChangeOutputMap.delete(codexItemId);
       state.fileChangePathMap.delete(codexItemId);
+      state.reasoningSummaryIndexMap.delete(codexItemId);
       return events;
     }
     const itemType = state.itemTypeMap.get(codexItemId) ?? canonicalTypeFor(item.type ?? item.kind);
@@ -300,6 +302,7 @@ export function mapCodexNotification(
     state.commandOutputSeenSet.delete(codexItemId);
     state.fileChangeOutputMap.delete(codexItemId);
     state.fileChangePathMap.delete(codexItemId);
+    state.reasoningSummaryIndexMap.delete(codexItemId);
     return events;
   }
 
@@ -310,6 +313,15 @@ export function mapCodexNotification(
     if (!delta) return [];
     const codexItemId = readItemId(params);
     if (!codexItemId) return [];
+    let contentDelta = delta;
+    const summaryIndex = params?.summaryIndex;
+    if (method === "item/reasoning/summaryTextDelta" && typeof summaryIndex === "number") {
+      const previousIndex = state.reasoningSummaryIndexMap.get(codexItemId);
+      if (previousIndex !== summaryIndex) {
+        if (previousIndex !== undefined) contentDelta = `\n\n${delta}`;
+        state.reasoningSummaryIndexMap.set(codexItemId, summaryIndex);
+      }
+    }
     let internalId = state.itemIdMap.get(codexItemId);
     const opened: RuntimeEvent[] = [];
     if (!internalId) {
@@ -349,7 +361,7 @@ export function mapCodexNotification(
         threadId,
         itemId: internalId,
         stream,
-        delta,
+        delta: contentDelta,
       },
     ];
   }

src/supervisor/agents/codex/canonicalMappingState.ts

@@ -16,6 +16,8 @@ export interface CodexMapperState {
   fileChangeOutputMap: Map<string, string>;
   /** Last path emitted for a file-change item, to avoid duplicate updates. */
   fileChangePathMap: Map<string, string>;
+  /** Last streamed reasoning summary index, used to preserve summary-part boundaries. */
+  reasoningSummaryIndexMap: Map<string, number>;
   /** Current chat item that mirrors the provider's active goal state. */
   goalItemId?: string;
   /** Provider-created timestamp for the current goal, when reported. */
@@ -34,6 +36,7 @@ export function createCodexMapperState(threadId: string): CodexMapperState {
     commandOutputSeenSet: new Set(),
     fileChangeOutputMap: new Map(),
     fileChangePathMap: new Map(),
+    reasoningSummaryIndexMap: new Map(),
   };
 }