diff --git a/src/web-search/progress-stream.ts b/src/web-search/progress-stream.ts
index f51a55efc6..e3889eb5bc 100644
--- a/src/web-search/progress-stream.ts
+++ b/src/web-search/progress-stream.ts
@@ -303,6 +303,10 @@ export async function* parseStreamWithProgress(
         }
         if (event.type === "done" || event.type === "incomplete") {
           heldTerminal = event;
+          // Response-byte inactivity ends once the adapter has produced a terminal event.
+          // From here the separate post-terminal drain guard owns the bounded wait for
+          // iterator cleanup, so leaving the inactivity timer armed creates a false timeout.
+          clearInactivity();
           continue;
         }
         await handoff.deliver(event);
diff --git a/tests/web-search/web-search-progress-stream.test.ts b/tests/web-search/web-search-progress-stream.test.ts
index ddb325b2fb..d36bb42594 100644
--- a/tests/web-search/web-search-progress-stream.test.ts
+++ b/tests/web-search/web-search-progress-stream.test.ts
@@ -215,10 +215,13 @@ describe("web-search streamed-body progress collector", () => {
     let returned = false;
     const parser: ParseStream = async function* () {
       yield { type: "done", usage: { inputTokens: 1, outputTokens: 2 } };
-      await sleep(20);
+      await sleep(30);
       returned = true;
     };
-    const iterator = parseStreamWithProgress(new Response(chunkStream([])), parser, { inactivityTimeoutMs: 100 });
+    const iterator = parseStreamWithProgress(new Response(chunkStream([])), parser, {
+      inactivityTimeoutMs: 10,
+      postTerminalDrainTimeoutMs: 100,
+    });
     const next = await iterator.next();
     expect(returned).toBe(true);
     expect(next.value).toEqual({ type: "done", usage: { inputTokens: 1, outputTokens: 2 } });