--- ../test/test_proxy_chunked.py	2026-09-14 20:59:37.551679293 +0300
+++ ../test/test_proxy_chunked.py	2026-09-14 20:59:58.286308772 +0300
@@ -351,7 +351,9 @@
 # fake_upstream — live Rust HTTP mock (test/fake_upstream/)
 # ---------------------------------------------------------------------------
 
-FAKE_UPSTREAM_BIN = '/usr/local/bin/fake_upstream'
+FAKE_UPSTREAM_BIN = os.path.join(
+    os.path.dirname(__file__), 'fake_upstream/target/debug/fake_upstream'
+)
 
 # Graceful skip when the Rust mock binary is not built (e.g. local runs
 # without a Rust toolchain).  CI installs it via the "Build fake_upstream"