diff --git a/core/tests/test_api_client.cpp b/core/tests/test_api_client.cpp
index 456a32a..b03973e 100644
--- a/core/tests/test_api_client.cpp
+++ b/core/tests/test_api_client.cpp
@@ -463,7 +463,17 @@ void testPlatformBackendTimeout()
         const auto elapsed = std::chrono::steady_clock::now() - start;
         const long long ms = std::chrono::duration_cast<std::chrono::milliseconds>(elapsed).count();
 
-        const bool gave_up = !response.ok() && ms < 4000;
+        // 4000 was the old bound, chosen when nothing bounded the wait. The
+        // code now promises a hard ceiling of 2x the caller's budget
+        // (RequestDeadline in http_winhttp.cpp), so assert THAT -- 1400ms
+        // here, plus slack for a loaded runner. This is also the only signal
+        // that survives a green run: CTest prints nothing on success, so if
+        // WinHTTP's own erratic cancellation (measured at 1490-4506ms for
+        // this same 700ms budget) were doing the work instead of the
+        // watchdog, roughly half the attempts would land above this bound and
+        // say so, instead of quietly passing under a 4s ceiling.
+        constexpr long long kCeilingMs = 2500;
+        const bool gave_up = !response.ok() && ms < kCeilingMs;
         if (gave_up)
             ++timed_out;
 
@@ -480,7 +490,7 @@ void testPlatformBackendTimeout()
                      gave_up ? "gave up (expected)" : "WAITED OUT THE STALL");
 
         ST_ASSERT(!response.ok());
-        ST_ASSERT(ms < 4000);
+        ST_ASSERT(ms < kCeilingMs);
     }
     std::fprintf(stderr, "  [timeout-probe] %d/%d attempts honoured the %ldms timeout\n",
                  timed_out, kProbes, kTimeoutMs);