diff --git a/cmux.xcodeproj/project.pbxproj b/cmux.xcodeproj/project.pbxproj
index 98844b5e0041..dd11ef68d7c2 100644
--- a/cmux.xcodeproj/project.pbxproj
+++ b/cmux.xcodeproj/project.pbxproj
@@ -12610,7 +12610,6 @@
 		};
 		D1FF50000000000000000001 /* Build Diff Sidecar */ = {
 			isa = PBXShellScriptBuildPhase;
-			alwaysOutOfDate = 1;
 			buildActionMask = 2147483647;
 			files = (
 			);
@@ -12635,11 +12634,11 @@
 			);
 			outputPaths = (
 				"$(TARGET_BUILD_DIR)/$(UNLOCALIZED_RESOURCES_FOLDER_PATH)/bin/cmux-diff-sidecar",
+				"$(TARGET_TEMP_DIR)/cmux-diff-sidecar.arch-$(ARCHS).min-$(MACOSX_DEPLOYMENT_TARGET).stamp",
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "\"${SRCROOT}/scripts/build-diff-sidecar.sh\"\n";
-		};
+			shellScript = "rm -f \"${TARGET_TEMP_DIR}\"/cmux-diff-sidecar.arch-*.min-*.stamp\nCMUX_DIFF_SIDECAR_ARCHS=\"${ARCHS}\" CMUX_DIFF_SIDECAR_MIN_MACOS=\"${MACOSX_DEPLOYMENT_TARGET}\" CMUX_DIFF_SIDECAR_STAMP=\"${TARGET_TEMP_DIR}/cmux-diff-sidecar.arch-${ARCHS}.min-${MACOSX_DEPLOYMENT_TARGET}.stamp\" \"${SRCROOT}/scripts/build-diff-sidecar.sh\"\n";		};
 		A9E030000000000000000009 /* Reject Bundled Provider Binaries */ = {
 			isa = PBXShellScriptBuildPhase;
 			alwaysOutOfDate = 1;
diff --git a/scripts/build-diff-sidecar.sh b/scripts/build-diff-sidecar.sh
index 13ec8d1689fd..3eb644445b21 100755
--- a/scripts/build-diff-sidecar.sh
+++ b/scripts/build-diff-sidecar.sh
@@ -96,3 +96,22 @@ chmod +x "$destination"
 if [[ "${CODE_SIGNING_ALLOWED:-YES}" != "NO" && -n "${EXPANDED_CODE_SIGN_IDENTITY:-}" ]]; then
   codesign --force --sign "$EXPANDED_CODE_SIGN_IDENTITY" "$destination" >/dev/null
 fi
+
+# Xcode's dependency-analysis output is keyed by the normal architecture and
+# deployment-target settings. The Xcode phase pins the script overrides to
+# those same build settings before invoking this script. The stamp is
+# intentionally optional so direct script callers retain override support.
+if [[ -n "${CMUX_DIFF_SIDECAR_STAMP:-}" ]]; then
+  stamp_tmp="$(mktemp "${CMUX_DIFF_SIDECAR_STAMP}.tmp.XXXXXX")"
+  cleanup_stamp_tmp() {
+    [[ -e "$stamp_tmp" ]] && rm -f "$stamp_tmp"
+  }
+  trap cleanup_stamp_tmp EXIT
+  {
+    printf 'requested_archs=%s\n' "$requested_archs"
+    printf 'min_macos=%s\n' "${CMUX_DIFF_SIDECAR_MIN_MACOS:-14.0}"
+    shasum -a 256 "$destination"
+  } > "$stamp_tmp"
+  mv -f "$stamp_tmp" "$CMUX_DIFF_SIDECAR_STAMP"
+  trap - EXIT
+fi