diff --git a/scripts/test.sh b/scripts/test.sh
index 462ab4df9..6f00b8706 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -280,7 +280,7 @@ CBM_TEST_BINARY="$WATCHDOG_BINARY" bash "$ROOT/tests/test_worker_watchdog.sh"
 # still exits nonzero for the user-facing tool error, but the supervisor must
 # preserve that response instead of misreporting exit_nonzero as a file crash.
 echo "=== Step 5c: worker error-response transport regression ==="
-bash "$ROOT/tests/test_worker_error_response.sh"
+CBM_TEST_BINARY="$WATCHDOG_BINARY" bash "$ROOT/tests/test_worker_error_response.sh"
 
 # Step 5d (#1388) is DELIBERATELY NOT GATING HERE — see
 # tests/test_hook_conflict_notice.sh for the full what-was-tried record.
diff --git a/tests/test_hook_conflict_notice.sh b/tests/test_hook_conflict_notice.sh
index b28b42493..e44b0f327 100644
--- a/tests/test_hook_conflict_notice.sh
+++ b/tests/test_hook_conflict_notice.sh
@@ -24,7 +24,7 @@
 set -euo pipefail
 
 ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-BINARY="${ROOT}/build/c/codebase-memory-mcp"
+BINARY="${CBM_TEST_BINARY:-${ROOT}/build/c/codebase-memory-mcp}"
 if [[ ! -x "${BINARY}" && -x "${BINARY}.exe" ]]; then
   BINARY="${BINARY}.exe"
 fi
diff --git a/tests/test_worker_error_response.sh b/tests/test_worker_error_response.sh
index 12ef481f3..5a28fb7da 100755
--- a/tests/test_worker_error_response.sh
+++ b/tests/test_worker_error_response.sh
@@ -6,7 +6,11 @@
 set -euo pipefail
 
 ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-BINARY="${ROOT}/build/c/codebase-memory-mcp"
+# scripts/test.sh builds into $BUILD_DIR, which is NOT build/c on every leg (the
+# Linux containers use build/linux-arm64 / build/linux-amd64). Honour the binary
+# the caller built, exactly as test_parent_watchdog.sh and test_worker_watchdog.sh
+# do; the build/c default keeps a bare manual invocation working.
+BINARY="${CBM_TEST_BINARY:-${ROOT}/build/c/codebase-memory-mcp}"
 if [[ ! -x "${BINARY}" && -x "${BINARY}.exe" ]]; then
   BINARY="${BINARY}.exe"
 fi