Fix laggy terminal sync during sidebar drags

.github/workflows/ci-macos-compat.yml

@@ -48,9 +48,10 @@ jobs:
           echo "Selected: $XCODE_APP"
           echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
           export DEVELOPER_DIR="$XCODE_DIR"
-          XCODE_VER="$(xcodebuild -version | head -1)"
+          XCODE_VERSION_OUTPUT="$(xcodebuild -version)"
+          XCODE_VER="${XCODE_VERSION_OUTPUT%%$'\n'*}"
           echo "XCODE_VER=$XCODE_VER" >> "$GITHUB_ENV"
-          echo "$XCODE_VER"
+          echo "$XCODE_VERSION_OUTPUT"
           xcrun --sdk macosx --show-sdk-path
           sw_vers
 

.github/workflows/ci.yml

@@ -385,3 +385,137 @@ jobs:
           CMUX_LAG_MAX_CHURN_P95_MS=35 \
           CMUX_LAG_KEY_EVENTS=180 \
           python3 tests/test_workspace_churn_up_arrow_lag.py
+
+  ui-display-resolution-regression:
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: warp-macos-15-arm64-6x
+    timeout-minutes: 25
+    steps:
+      - name: Checkout
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        with:
+          submodules: recursive
+
+      - name: Select Xcode
+        run: |
+          set -euo pipefail
+          if [ -d "/Applications/Xcode.app/Contents/Developer" ]; then
+            XCODE_DIR="/Applications/Xcode.app/Contents/Developer"
+          else
+            XCODE_APP="$(ls -d /Applications/Xcode*.app 2>/dev/null | sort | tail -n 1 || true)"
+            if [ -n "$XCODE_APP" ]; then
+              XCODE_DIR="$XCODE_APP/Contents/Developer"
+            else
+              echo "No Xcode.app found under /Applications" >&2
+              exit 1
+            fi
+          fi
+          echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
+          export DEVELOPER_DIR="$XCODE_DIR"
+          xcodebuild -version
+          xcrun --sdk macosx --show-sdk-path
+
+      - name: Download pre-built GhosttyKit.xcframework
+        run: ./scripts/download-prebuilt-ghosttykit.sh
+
+      - name: Install zig
+        run: |
+          ZIG_REQUIRED="0.15.2"
+          if command -v zig >/dev/null 2>&1 && zig version 2>/dev/null | grep -q "^${ZIG_REQUIRED}"; then
+            echo "zig ${ZIG_REQUIRED} already installed"
+          else
+            echo "Installing zig ${ZIG_REQUIRED} from tarball"
+            curl -fSL "https://ziglang.org/download/${ZIG_REQUIRED}/zig-aarch64-macos-${ZIG_REQUIRED}.tar.xz" -o /tmp/zig.tar.xz
+            tar xf /tmp/zig.tar.xz -C /tmp
+            sudo mkdir -p /usr/local/bin /usr/local/lib
+            sudo cp -f /tmp/zig-aarch64-macos-${ZIG_REQUIRED}/zig /usr/local/bin/zig
+            sudo cp -rf /tmp/zig-aarch64-macos-${ZIG_REQUIRED}/lib /usr/local/lib/zig
+            export PATH="/usr/local/bin:$PATH"
+            zig version
+          fi
+
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .ci-source-packages
+          key: spm-ui-display-resolution-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-ui-display-resolution-
+
+      - name: Resolve Swift packages
+        run: |
+          set -euo pipefail
+          SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
+          mkdir -p "$SOURCE_PACKAGES_DIR"
+
+          for attempt in 1 2 3; do
+            if xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
+              -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
+              -resolvePackageDependencies; then
+              exit 0
+            fi
+            if [ "$attempt" -eq 3 ]; then
+              echo "Failed to resolve Swift packages after 3 attempts" >&2
+              exit 1
+            fi
+            echo "Package resolution failed on attempt $attempt, retrying..."
+            sleep $((attempt * 5))
+          done
+
+      - name: Run display resolution churn UI regression
+        run: |
+          set -euo pipefail
+          SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
+          HARNESS_DIR="${RUNNER_TEMP}/cmux-display-churn-${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}"
+          mkdir -p "$HARNESS_DIR"
+          PREFIX="${HARNESS_DIR}/cmux-display-churn"
+          READY_PATH="${PREFIX}.ready"
+          DISPLAY_ID_PATH="${PREFIX}.id"
+          START_PATH="${PREFIX}.start"
+          DONE_PATH="${PREFIX}.done"
+          LOG_PATH="${PREFIX}.log"
+          MANIFEST_PATH="${HARNESS_DIR}/cmux-ui-test-display-harness.json"
+
+          rm -f "$READY_PATH" "$DISPLAY_ID_PATH" "$START_PATH" "$DONE_PATH" "$LOG_PATH" "$MANIFEST_PATH"
+
+          clang -framework Foundation -framework CoreGraphics \
+            -o /tmp/create-virtual-display scripts/create-virtual-display.m
+
+          /tmp/create-virtual-display \
+            --modes 1920x1080,1728x1117,1600x900,1440x810 \
+            --ready-path "$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 &
+          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="$LOG_PATH" \
+          xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
+            -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
+            -disableAutomaticPackageResolution \
+            -destination "platform=macOS" \
+            -only-testing:cmuxUITests/DisplayResolutionRegressionUITests \
+            test

.github/workflows/test-e2e.yml

@@ -108,6 +108,7 @@ jobs:
           fi
 
       - name: Create virtual display
+        if: ${{ inputs.test_filter != 'DisplayResolutionRegressionUITests' }}
         run: |
           set -euo pipefail
           echo "=== Display before ==="
@@ -204,8 +205,64 @@ jobs:
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
           ONLY_TESTING="-only-testing:cmuxUITests/$TEST_FILTER"
+          DISPLAY_ENV_PREFIX=()
+
+          if [ "$TEST_FILTER" = "DisplayResolutionRegressionUITests" ]; then
+            HARNESS_DIR="${RUNNER_TEMP}/cmux-display-churn-${{ github.run_id }}-${{ github.run_attempt }}"
+            mkdir -p "$HARNESS_DIR"
+            PREFIX="${HARNESS_DIR}/cmux-display-churn"
+            READY_PATH="${PREFIX}.ready"
+            DISPLAY_ID_PATH="${PREFIX}.id"
+            START_PATH="${PREFIX}.start"
+            DONE_PATH="${PREFIX}.done"
+            LOG_PATH="${PREFIX}.log"
+            MANIFEST_PATH="${HARNESS_DIR}/cmux-ui-test-display-harness.json"
+
+            rm -f "$READY_PATH" "$DISPLAY_ID_PATH" "$START_PATH" "$DONE_PATH" "$LOG_PATH" "$MANIFEST_PATH"
+
+            clang -framework Foundation -framework CoreGraphics \
+              -o /tmp/create-virtual-display scripts/create-virtual-display.m
+
+            /tmp/create-virtual-display \
+              --modes 1920x1080,1728x1117,1600x900,1440x810 \
+              --ready-path "$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"
+
+            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"
+            )
+          fi
 
-          # Start recording right before the test (after build/resolve)
+          # Start recording right before the test (after build/resolve).
+          # The display churn regression creates its own virtual display above,
+          # so recording must start after that harness is ready.
           if [ "$RECORD_VIDEO" = "true" ]; then
             DEVLIST=$( ffmpeg -f avfoundation -list_devices true -i "" 2>&1 || true )
             echo "Available devices:"
@@ -233,7 +290,7 @@ jobs:
           fi
 
           set +e
-          OUTPUT=$(xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
+          OUTPUT=$(env "${DISPLAY_ENV_PREFIX[@]}" xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux -configuration Debug \
             -clonedSourcePackagesDirPath "$SOURCE_PACKAGES_DIR" \
             -disableAutomaticPackageResolution \
             -destination "platform=macOS" \

GhosttyTabs.xcodeproj/project.pbxproj

@@ -76,6 +76,7 @@
 			B9000012A1B2C3D4E5F60719 /* AutomationSocketUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B9000011A1B2C3D4E5F60719 /* AutomationSocketUITests.swift */; };
 			B8F266236A1A3D9A45BD840F /* SidebarResizeUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 818DBCD4AB69EB72573E8138 /* SidebarResizeUITests.swift */; };
 			B8F266246A1A3D9A45BD840F /* SidebarHelpMenuUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B8F266256A1A3D9A45BD840F /* SidebarHelpMenuUITests.swift */; };
+			B8F266266A1A3D9A45BD840F /* DisplayResolutionRegressionUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B8F266276A1A3D9A45BD840F /* DisplayResolutionRegressionUITests.swift */; };
 			C0B4D9B0A1B2C3D4E5F60718 /* UpdatePillUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0B4D9B1A1B2C3D4E5F60718 /* UpdatePillUITests.swift */; };
 					B9000014A1B2C3D4E5F60719 /* JumpToUnreadUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B9000013A1B2C3D4E5F60719 /* JumpToUnreadUITests.swift */; };
 					B9000015A1B2C3D4E5F60719 /* MultiWindowNotificationsUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B9000016A1B2C3D4E5F60719 /* MultiWindowNotificationsUITests.swift */; };
@@ -231,6 +232,7 @@
 		A5001611 /* SessionPersistence.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SessionPersistence.swift; sourceTree = "<group>"; };
 		818DBCD4AB69EB72573E8138 /* SidebarResizeUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SidebarResizeUITests.swift; sourceTree = "<group>"; };
 		B8F266256A1A3D9A45BD840F /* SidebarHelpMenuUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SidebarHelpMenuUITests.swift; sourceTree = "<group>"; };
+		B8F266276A1A3D9A45BD840F /* DisplayResolutionRegressionUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DisplayResolutionRegressionUITests.swift; sourceTree = "<group>"; };
 		C0B4D9B1A1B2C3D4E5F60718 /* UpdatePillUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UpdatePillUITests.swift; sourceTree = "<group>"; };
 		A5001101 /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
 		IC000002 /* AppIcon.icon */ = {isa = PBXFileReference; lastKnownFileType = folder; path = AppIcon.icon; sourceTree = "<group>"; };
@@ -491,6 +493,7 @@
 							B9000016A1B2C3D4E5F60719 /* MultiWindowNotificationsUITests.swift */,
 							818DBCD4AB69EB72573E8138 /* SidebarResizeUITests.swift */,
 							B8F266256A1A3D9A45BD840F /* SidebarHelpMenuUITests.swift */,
+							B8F266276A1A3D9A45BD840F /* DisplayResolutionRegressionUITests.swift */,
 							D0E0F0B1A1B2C3D4E5F60718 /* BrowserPaneNavigationKeybindUITests.swift */,
 							D0E0F0B3A1B2C3D4E5F60718 /* BrowserOmnibarSuggestionsUITests.swift */,
 							FB100001A1B2C3D4E5F60718 /* BrowserImportProfilesUITests.swift */,
@@ -749,6 +752,7 @@
 							B9000015A1B2C3D4E5F60719 /* MultiWindowNotificationsUITests.swift in Sources */,
 							B8F266236A1A3D9A45BD840F /* SidebarResizeUITests.swift in Sources */,
 							B8F266246A1A3D9A45BD840F /* SidebarHelpMenuUITests.swift in Sources */,
+							B8F266266A1A3D9A45BD840F /* DisplayResolutionRegressionUITests.swift in Sources */,
 							D0E0F0B0A1B2C3D4E5F60718 /* BrowserPaneNavigationKeybindUITests.swift in Sources */,
 							D0E0F0B2A1B2C3D4E5F60718 /* BrowserOmnibarSuggestionsUITests.swift in Sources */,
 							FB100000A1B2C3D4E5F60718 /* BrowserImportProfilesUITests.swift in Sources */,

Resources/shell-integration/cmux-zsh-integration.zsh

@@ -143,9 +143,8 @@ _cmux_install_winch_guard() {
         [[ -n "$CMUX_TAB_ID" ]] || return 0
         [[ -n "$CMUX_PANEL_ID" ]] || return 0
 
-        # Keep a spacer line so prompt redraw during resize cannot clobber the
-        # tail of command output that was rendered immediately above the prompt.
-        builtin print -r -- ""
+        # Ghostty already marks prompt redraws on SIGWINCH. Writing to the PTY
+        # here grows the screen and makes resize look like a fresh prompt.
         return 0
     }