diff --git a/harness/trajectory_replay/public_webarena/executor.py b/harness/trajectory_replay/public_webarena/executor.py
index c6dcec76b..2731e36db 100644
--- a/harness/trajectory_replay/public_webarena/executor.py
+++ b/harness/trajectory_replay/public_webarena/executor.py
@@ -325,23 +325,25 @@ def publish_layout(current_page: Any = action_page) -> None:
                     )
                 if navigation_response_observer is not None:
                     navigation_response_observer(response)
-                # BrowserTool returns after DOMContentLoaded, then gives ordinary
-                # background requests a short chance to settle.  Network idle is
-                # deliberately best effort: analytics or streaming requests must
-                # not turn a completed navigation into a failed replay action.
-                try:
-                    action_page.wait_for_load_state(
-                        "networkidle",
-                        timeout=min(action_remaining(), NAVIGATION_NETWORK_IDLE_TIMEOUT_MS),
-                    )
-                except Exception:
-                    pass
-                try:
+                # Settling is optional; reserve at least half the remaining
+                # action budget for layout and the required document observation.
+                # Both waits share this deadline so a busy network cannot consume
+                # the observation budget or start another full grace period.
+                settle_deadline = time.perf_counter() + action_remaining() / 2_000
+                settle_timeout = int((settle_deadline - time.perf_counter()) * 1_000)
+                if settle_timeout > 0:
+                    try:
+                        action_page.wait_for_load_state(
+                            "networkidle",
+                            timeout=min(settle_timeout, NAVIGATION_NETWORK_IDLE_TIMEOUT_MS),
+                        )
+                    except Exception:
+                        pass
+                settle_timeout = int((settle_deadline - time.perf_counter()) * 1_000)
+                if settle_timeout > 0:
                     action_page.wait_for_timeout(
-                        min(action_remaining(), NAVIGATION_RENDER_GRACE_MS)
+                        min(settle_timeout, NAVIGATION_RENDER_GRACE_MS)
                     )
-                except TimeoutError:
-                    pass
                 publish_layout()
                 limit = int(call.get("max_chars", 40_000))
                 if document_observer is None:
diff --git a/tests/trajectory_replay/public_webarena/test_executor.py b/tests/trajectory_replay/public_webarena/test_executor.py
index 5c0efad24..a919a0689 100644
--- a/tests/trajectory_replay/public_webarena/test_executor.py
+++ b/tests/trajectory_replay/public_webarena/test_executor.py
@@ -448,6 +448,64 @@ def wait_for_load_state(self, state, **kwargs):
     assert responses[0].status == 200
 
 
+@pytest.mark.parametrize("network_delay_ms", [50, 500, 5_000])
+@pytest.mark.parametrize("observation_ms", [300, 600])
+def test_navigation_reserves_observation_budget_without_extending_deadline(
+    monkeypatch, network_delay_ms, observation_ms
+):
+    clock = [0.0]
+    monkeypatch.setattr(
+        "harness.trajectory_replay.public_webarena.executor.time.perf_counter",
+        lambda: clock[0],
+    )
+
+    class TimedPage(FakePage):
+        def goto(self, url, **kwargs):
+            clock[0] += 0.05
+            return super().goto(url, **kwargs)
+
+        def wait_for_load_state(self, state, **kwargs):
+            allotted = kwargs["timeout"]
+            clock[0] += min(network_delay_ms, allotted) / 1_000
+            if network_delay_ms > allotted:
+                raise TimeoutError("streaming request is still open")
+
+        def wait_for_timeout(self, milliseconds):
+            clock[0] += milliseconds / 1_000
+
+    def observe(page, timeout, limit):
+        assert timeout >= 475
+        clock[0] += min(observation_ms, timeout) / 1_000
+        if observation_ms > timeout:
+            raise TimeoutError("document observation timed out")
+        return "Observed title", "Observed body"
+
+    trace = []
+
+    def run():
+        return execute_steps(
+            TimedPage(),
+            [{
+                "action": "navigate",
+                "url": "https://example.com",
+                "timeout_ms": 1_000,
+                "save_as": "page",
+            }],
+            document_observer=observe,
+            trace=trace,
+        )
+
+    # A genuinely slow observation must still fail within the original budget.
+    if observation_ms == 600 and network_delay_ms >= 500:
+        with pytest.raises(TimeoutError, match="document observation timed out"):
+            run()
+        assert trace[0]["status"] == "fail"
+    else:
+        assert run()["page"].endswith("Observed body")
+        assert trace[0]["status"] == "pass"
+    assert clock[0] <= 1.0
+
+
 def test_same_document_navigation_without_response_reloads_for_network_evidence():
     class SamePage(FakePage):
         def __init__(self):