From 7fb1f50966def2a4d37a7f7c9c62f967b28c4592 Mon Sep 17 00:00:00 2001
From: Lawrence Chen <lawrencecchen@users.noreply.github.com>
Date: Wed, 18 Mar 2026 03:22:04 -0700
Subject: [PATCH] Launch display helper from inside the UI test sandbox

---
 .github/workflows/ci.yml                      | 47 ++-----------------
 .github/workflows/test-e2e.yml                | 47 ++-----------------
 .../DisplayResolutionRegressionUITests.swift  | 28 ++++++++---
 3 files changed, 28 insertions(+), 94 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d1fdec6d..8018dbf9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -465,53 +465,12 @@ jobs:
         run: |
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
-          PREFIX="/tmp/cmux-display-churn-${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}"
-          READY_PATH="${PREFIX}.ready"
-          DISPLAY_ID_PATH="${PREFIX}.id"
-          START_PATH="${PREFIX}.start"
-          DONE_PATH="${PREFIX}.done"
-          LOG_PATH="${PREFIX}.log"
-          MANIFEST_PATH="/tmp/cmux-ui-test-display-harness.json"
-
-          rm -f "$READY_PATH" "$DISPLAY_ID_PATH" "$START_PATH" "$DONE_PATH" "$LOG_PATH" "$MANIFEST_PATH"
+          HELPER_PATH="/tmp/create-virtual-display"
 
           clang -framework Foundation -framework CoreGraphics \
-            -o /tmp/create-virtual-display scripts/create-virtual-display.m
+            -o "$HELPER_PATH" scripts/create-virtual-display.m
 
-          /tmp/create-virtual-display \
-            --modes 1920x1080,1728x1117,1600x900,1440x810 \
-            --ready-path "$READY_PATH" \
-            --display-id-path "$DISPLAY_ID_PATH" \
-            --start-path "$START_PATH" \
-            --done-path "$DONE_PATH" \
-            --iterations 40 \
-            --interval-ms 40 \
-            >"$LOG_PATH" 2>&1 &
-          VDISPLAY_PID=$!
-          trap 'kill "$VDISPLAY_PID" >/dev/null 2>&1 || true; rm -f "$MANIFEST_PATH"' EXIT
-
-          for _ in {1..120}; do
-            [ -f "$READY_PATH" ] && break
-            sleep 0.25
-          done
-          [ -f "$READY_PATH" ] || {
-            echo "Display harness failed to start" >&2
-            cat "$LOG_PATH" >&2 || true
-            exit 1
-          }
-
-          cat >"$MANIFEST_PATH" <<EOF
-          {"readyPath":"$READY_PATH","displayIDPath":"$DISPLAY_ID_PATH","startPath":"$START_PATH","donePath":"$DONE_PATH","logPath":"$LOG_PATH"}
-          EOF
-          echo "Display harness manifest: $MANIFEST_PATH"
-          cat "$MANIFEST_PATH"
-
-          CMUX_UI_TEST_DISPLAY_READY_PATH="$READY_PATH" \
-          CMUX_UI_TEST_DISPLAY_ID_PATH="$DISPLAY_ID_PATH" \
-          CMUX_UI_TEST_DISPLAY_START_PATH="$START_PATH" \
-          CMUX_UI_TEST_DISPLAY_DONE_PATH="$DONE_PATH" \
-          CMUX_UI_TEST_DISPLAY_LOG_PATH="$LOG_PATH" \
-          CMUX_UI_TEST_DISPLAY_HARNESS_MANIFEST_PATH="$MANIFEST_PATH" \
+          CMUX_UI_TEST_DISPLAY_HELPER_BINARY_PATH="$HELPER_PATH" \
           xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
             -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
             -disableAutomaticPackageResolution \
diff --git a/.github/workflows/test-e2e.yml b/.github/workflows/test-e2e.yml
index e538b6c5..2fc23e61 100644
--- a/.github/workflows/test-e2e.yml
+++ b/.github/workflows/test-e2e.yml
@@ -208,54 +208,13 @@ jobs:
           DISPLAY_ENV_PREFIX=()
 
           if [ "$TEST_FILTER" = "DisplayResolutionRegressionUITests" ]; then
-            PREFIX="/tmp/cmux-display-churn-${{ github.run_id }}-${{ github.run_attempt }}"
-            READY_PATH="${PREFIX}.ready"
-            DISPLAY_ID_PATH="${PREFIX}.id"
-            START_PATH="${PREFIX}.start"
-            DONE_PATH="${PREFIX}.done"
-            LOG_PATH="${PREFIX}.log"
-            MANIFEST_PATH="/tmp/cmux-ui-test-display-harness.json"
-
-            rm -f "$READY_PATH" "$DISPLAY_ID_PATH" "$START_PATH" "$DONE_PATH" "$LOG_PATH" "$MANIFEST_PATH"
+            HELPER_PATH="/tmp/create-virtual-display"
 
             clang -framework Foundation -framework CoreGraphics \
-              -o /tmp/create-virtual-display scripts/create-virtual-display.m
-
-            /tmp/create-virtual-display \
-              --modes 1920x1080,1728x1117,1600x900,1440x810 \
-              --ready-path "$READY_PATH" \
-              --display-id-path "$DISPLAY_ID_PATH" \
-              --start-path "$START_PATH" \
-              --done-path "$DONE_PATH" \
-              --iterations 40 \
-              --interval-ms 40 \
-              >"$LOG_PATH" 2>&1 &
-            DISPLAY_VDISPLAY_PID=$!
-            trap 'kill "${DISPLAY_VDISPLAY_PID:-}" >/dev/null 2>&1 || true; rm -f "$MANIFEST_PATH"' EXIT
-
-            for _ in {1..120}; do
-              [ -f "$READY_PATH" ] && break
-              sleep 0.25
-            done
-            [ -f "$READY_PATH" ] || {
-              echo "Display harness failed to start" >&2
-              cat "$LOG_PATH" >&2 || true
-              exit 1
-            }
-
-            cat >"$MANIFEST_PATH" <<EOF
-          {"readyPath":"$READY_PATH","displayIDPath":"$DISPLAY_ID_PATH","startPath":"$START_PATH","donePath":"$DONE_PATH","logPath":"$LOG_PATH"}
-          EOF
-            echo "Display harness manifest: $MANIFEST_PATH"
-            cat "$MANIFEST_PATH"
+              -o "$HELPER_PATH" scripts/create-virtual-display.m
 
             DISPLAY_ENV_PREFIX=(
-              CMUX_UI_TEST_DISPLAY_READY_PATH="$READY_PATH"
-              CMUX_UI_TEST_DISPLAY_ID_PATH="$DISPLAY_ID_PATH"
-              CMUX_UI_TEST_DISPLAY_START_PATH="$START_PATH"
-              CMUX_UI_TEST_DISPLAY_DONE_PATH="$DONE_PATH"
-              CMUX_UI_TEST_DISPLAY_LOG_PATH="$LOG_PATH"
-              CMUX_UI_TEST_DISPLAY_HARNESS_MANIFEST_PATH="$MANIFEST_PATH"
+              CMUX_UI_TEST_DISPLAY_HELPER_BINARY_PATH="$HELPER_PATH"
             )
           fi
 
diff --git a/cmuxUITests/DisplayResolutionRegressionUITests.swift b/cmuxUITests/DisplayResolutionRegressionUITests.swift
index f508e09f..a504c634 100644
--- a/cmuxUITests/DisplayResolutionRegressionUITests.swift
+++ b/cmuxUITests/DisplayResolutionRegressionUITests.swift
@@ -19,14 +19,17 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
         continueAfterFailure = false
 
         let token = UUID().uuidString
+        let tempPrefix = FileManager.default.temporaryDirectory
+            .appendingPathComponent("cmux-ui-test-display-\(token)")
+            .path
         launchTag = "ui-tests-display-resolution-\(token.prefix(8))"
         diagnosticsPath = "/tmp/cmux-ui-test-display-churn-\(token).json"
-        displayReadyPath = "/tmp/cmux-ui-test-display-ready-\(token)"
-        displayIDPath = "/tmp/cmux-ui-test-display-id-\(token)"
-        displayStartPath = "/tmp/cmux-ui-test-display-start-\(token)"
-        displayDonePath = "/tmp/cmux-ui-test-display-done-\(token)"
-        helperBinaryPath = "/tmp/cmux-ui-test-display-helper-\(token)"
-        helperLogPath = "/tmp/cmux-ui-test-display-helper-\(token).log"
+        displayReadyPath = "\(tempPrefix).ready"
+        displayIDPath = "\(tempPrefix).id"
+        displayStartPath = "\(tempPrefix).start"
+        displayDonePath = "\(tempPrefix).done"
+        helperBinaryPath = "\(tempPrefix)-helper"
+        helperLogPath = "\(tempPrefix)-helper.log"
 
         removeTestArtifacts()
     }
@@ -118,6 +121,11 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
 
     private func prepareDisplayHarnessIfNeeded() throws {
         let env = ProcessInfo.processInfo.environment
+        if let helperBinaryPath = loadPrebuiltHelperBinaryPath(env) {
+            self.helperBinaryPath = helperBinaryPath
+            try launchDisplayHelper()
+            return
+        }
         if let externalHarness = loadExternalHarnessFromEnvironment(env) ?? loadExternalHarnessFromManifest(env) {
             displayReadyPath = externalHarness.readyPath
             displayIDPath = externalHarness.displayIDPath
@@ -133,6 +141,14 @@ final class DisplayResolutionRegressionUITests: XCTestCase {
         try launchDisplayHelper()
     }
 
+    private func loadPrebuiltHelperBinaryPath(_ env: [String: String]) -> String? {
+        guard let helperBinaryPath = env["CMUX_UI_TEST_DISPLAY_HELPER_BINARY_PATH"],
+              !helperBinaryPath.isEmpty else {
+            return nil
+        }
+        return helperBinaryPath
+    }
+
     private func loadExternalHarnessFromEnvironment(_ env: [String: String]) -> ExternalDisplayHarness? {
         guard let readyPath = env["CMUX_UI_TEST_DISPLAY_READY_PATH"], !readyPath.isEmpty,
               let displayIDPath = env["CMUX_UI_TEST_DISPLAY_ID_PATH"], !displayIDPath.isEmpty,