diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8018dbf9..78dea457 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -466,11 +466,18 @@ jobs:
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
           HELPER_PATH="/tmp/create-virtual-display"
+          MANIFEST_PATH="/tmp/cmux-ui-test-display-harness.json"
+
+          rm -f "$MANIFEST_PATH"
+          trap 'rm -f "$MANIFEST_PATH"' EXIT
 
           clang -framework Foundation -framework CoreGraphics \
             -o "$HELPER_PATH" scripts/create-virtual-display.m
 
-          CMUX_UI_TEST_DISPLAY_HELPER_BINARY_PATH="$HELPER_PATH" \
+          cat >"$MANIFEST_PATH" <<EOF
+          {"helperBinaryPath":"$HELPER_PATH"}
+          EOF
+
           xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
             -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
             -disableAutomaticPackageResolution \
diff --git a/.github/workflows/test-e2e.yml b/.github/workflows/test-e2e.yml
index 2fc23e61..9e06603e 100644
--- a/.github/workflows/test-e2e.yml
+++ b/.github/workflows/test-e2e.yml
@@ -209,13 +209,17 @@ jobs:
 
           if [ "$TEST_FILTER" = "DisplayResolutionRegressionUITests" ]; then
             HELPER_PATH="/tmp/create-virtual-display"
+            MANIFEST_PATH="/tmp/cmux-ui-test-display-harness.json"
+
+            rm -f "$MANIFEST_PATH"
+            trap 'rm -f "$MANIFEST_PATH"' EXIT
 
             clang -framework Foundation -framework CoreGraphics \
               -o "$HELPER_PATH" scripts/create-virtual-display.m
 
-            DISPLAY_ENV_PREFIX=(
-              CMUX_UI_TEST_DISPLAY_HELPER_BINARY_PATH="$HELPER_PATH"
-            )
+            cat >"$MANIFEST_PATH" <<EOF
+            {"helperBinaryPath":"$HELPER_PATH"}
+            EOF
           fi
 
           # Start recording right before the test (after build/resolve).
diff --git a/cmuxUITests/DisplayResolutionRegressionUITests.swift b/cmuxUITests/DisplayResolutionRegressionUITests.swift
index a504c634..1cc5aecf 100644
--- a/cmuxUITests/DisplayResolutionRegressionUITests.swift
+++ b/cmuxUITests/DisplayResolutionRegressionUITests.swift
@@ -127,10 +127,23 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
             return
         }
         if let externalHarness = loadExternalHarnessFromEnvironment(env) ?? loadExternalHarnessFromManifest(env) {
-            displayReadyPath = externalHarness.readyPath
-            displayIDPath = externalHarness.displayIDPath
-            displayStartPath = externalHarness.startPath
-            displayDonePath = externalHarness.donePath
+            if let helperBinaryPath = externalHarness.helperBinaryPath, !helperBinaryPath.isEmpty {
+                self.helperBinaryPath = helperBinaryPath
+                try launchDisplayHelper()
+                return
+            }
+            guard let readyPath = externalHarness.readyPath, !readyPath.isEmpty,
+                  let displayIDPath = externalHarness.displayIDPath, !displayIDPath.isEmpty,
+                  let startPath = externalHarness.startPath, !startPath.isEmpty,
+                  let donePath = externalHarness.donePath, !donePath.isEmpty else {
+                throw NSError(domain: "DisplayResolutionRegressionUITests", code: 3, userInfo: [
+                    NSLocalizedDescriptionKey: "Incomplete external display harness configuration"
+                ])
+            }
+            displayReadyPath = readyPath
+            self.displayIDPath = displayIDPath
+            displayStartPath = startPath
+            displayDonePath = donePath
             if let logPath = externalHarness.logPath, !logPath.isEmpty {
                 helperLogPath = logPath
             }
@@ -162,7 +175,8 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
             displayIDPath: displayIDPath,
             startPath: startPath,
             donePath: donePath,
-            logPath: env["CMUX_UI_TEST_DISPLAY_LOG_PATH"]
+            logPath: env["CMUX_UI_TEST_DISPLAY_LOG_PATH"],
+            helperBinaryPath: nil
         )
     }
 
@@ -394,10 +408,11 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
     }
 
     private struct ExternalDisplayHarness: Decodable {
-        let readyPath: String
-        let displayIDPath: String
-        let startPath: String
-        let donePath: String
+        let readyPath: String?
+        let displayIDPath: String?
+        let startPath: String?
+        let donePath: String?
         let logPath: String?
+        let helperBinaryPath: String?
     }
 }