Remove the Ghostty engine (#63)

## Summary

Removes the optional Ghostty (`libghostty-vt`) terminal engine. The
builtin engine is now the only engine.

## Why

- **Builtin already covers it.** Ghostty advertised only `Vt52Keyboard`.
Builtin advertises that plus grapheme clusters, row rendition, DRCS,
kitty keyboard, modifyOtherKeys, Win32 input, and
Sixel/iTerm2/ConEmu/kitty images (see `docs/parity-status.md`). On all
13 vt benchmark workloads the two engines produced identical screens
except one `styled` row, which is a builtin bug (a combining mark after
a space is dropped) and is not fixed here.
- **Ghostty was opt-in only.** It sat behind
`experimental.terminalEngine`; builtin was the default.
- **Upgrading to 1.4 would have been a regression.** libghostty-vt 1.4.0
makes Windows ingest about 6x slower on any workload that fills
scrollback (`scrolling`: 29 → 5 MB/s). The cause is upstream commit
`60b43068c` ("reclaim pooled and compressed page memory on Windows"),
which calls `DiscardVirtualMemory` on every recycled page. Disabling
that one change brought 1.4 back to 35 MB/s.

## What changed

- **Code:** deleted `src/Devolutions.Terminal.Ghostty`,
`tests/Devolutions.Terminal.Ghostty.Tests`, `native/ghostty`,
`.github/workflows/build-ghostty.yml` and `docs/ghostty-engine.md`.
- **Settings:** removed `experimental.terminalEngine` (global and per
profile) and the two engine pickers in the settings editor. A settings
file that still selects `"ghostty"` loads as builtin, and saving leaves
the key untouched because saves are diff-based. Tests cover this.
- **Packaging:** `ghostty-vt.dll`/`libghostty-vt.so`/`.dylib` and
`THIRD-PARTY-NOTICES-GHOSTTY.txt` are no longer shipped or checked in
the MSIX, Linux, macOS or NuGet payloads. `GHOSTTY_LIBRARY` is gone from
`macos/package.env`.
- **Native restore:** `NativeLibraries.targets` and
`Restore-NativeLibraries.ps1` now only build `dt-pty-host`, for
Linux/macOS RIDs; Windows builds skip the restore step entirely. The Zig
pin (unchanged at 0.16.0) moves to `native/zig.json`.
- **CI:** cache keys now hash `native/zig.json` and are bumped to
`native-v3`, so old caches containing Ghostty sources and binaries
aren't restored.
- **Benchmarks:** the `vt` suite replaces the `ghostty-vt`/`ghostty`
targets with a `control` target. It runs FNV-1a over the same bytes, a
serial loop whose speed follows the core clock, and `-Baseline` now
gates on builtin/control. `-RequireBeatGhostty`, `-GhosttyBench`,
`--no-gate` and the screen-equivalence check are removed.
- **Docs:** the Ghostty comparison moved to
`docs/history/ghostty-comparison-benchmarks.md`, with a shorter current
`docs/performance-benchmarks.md` in its place. README, AGENTS,
CONTRIBUTING, NOTICE, parity-status, release, macOS and renderer docs
are updated.

## Testing

- **Build and tests:** `dotnet build Devolutions.Terminal.slnx -c
Release` gives 0 warnings and 0 errors. `dotnet test` passes 3,170 tests
with 11 skipped (Windows x64).
- **Package self-tests:** `Test-ConPtyPublishLayout.ps1`,
`Test-MacOsLegalNotices.ps1` and `Test-PackageBuild.ps1` pass locally.
- **Native restore:** a forced `linux-x64` restore downloads Zig 0.16.0
from `native/zig.json` and builds `dt-pty-host`. A `win-x64` restore is
a no-op.
- **Bench:** a `-Baseline` comparison between two runs works. Absolute
builtin speed moved −3.4% while builtin/control moved +2.1%, so the
control absorbs machine drift.

## Reviewer notes

- **macOS and Linux packaging scripts** were syntax-checked only (`bash
-n`, PowerShell parser). This PR's CI is their first real run, and
`Test-MacOsPackagingMetadata.ps1` needs `plutil`.
- **Intentional "ghostty" mentions:** the bench workload descriptions
still credit `ghostty-gen` as the source of the corpus shapes, and the
corpus bytes are unchanged so saved baselines stay comparable.
`winterm-ghostty` comments refer to an unrelated prior-art project.
- **Branch name:** it still says "1.4 upgrade" because the work started
as that upgrade. The upgrade edits were discarded in favor of the
removal.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: mamoreau-devolutions

.github/workflows/build-ghostty.yml

@@ -6,11 +6,7 @@ on:
       - "**"
     tags:
       - "v*"
-    paths-ignore:
-      - ".github/workflows/build-ghostty.yml"
   pull_request:
-    paths-ignore:
-      - ".github/workflows/build-ghostty.yml"
   workflow_dispatch:
     inputs:
       version:
@@ -142,12 +138,10 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
           # Never restore native sources or reuse binaries built from different inputs.
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -199,7 +193,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: artifacts/tools
-          key: zig-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/Zig.ps1', 'native/ghostty/ghostty-upstream.json') }}
+          key: zig-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/Zig.ps1', 'native/zig.json') }}
 
       - name: Build dt-pty-host for every Unix RID
         shell: pwsh
@@ -233,7 +227,7 @@ jobs:
         with:
           path: |
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -337,11 +331,9 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ matrix.rid }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ matrix.rid }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -378,11 +370,9 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -411,11 +401,9 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -460,11 +448,9 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4

.github/workflows/build-terminal.yml

@@ -57,11 +57,9 @@ jobs:
         with:
           path: |
             artifacts/tools
-            artifacts/ghostty-src
-            native/ghostty/*/*
             native/linux-pty/*/dt-pty-host
             native/noto-emoji/NotoColorEmoji.ttf
-          key: native-v2-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/ghostty/ghostty-upstream.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
+          key: native-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('native/**/*.ps1', 'native/zig.json', 'native/linux-pty/dt-pty-host.c', 'native/noto-emoji/noto-emoji.json') }}
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v4
@@ -72,7 +70,7 @@ jobs:
         shell: pwsh
         run: ./scripts/Install-IsebergTestPowerShell.ps1
 
-      # A native cache miss downloads Zig and compiles Ghostty; keep that out of the test budget.
+      # A native cache miss downloads Zig and compiles dt-pty-host; keep that out of the test budget.
       - name: Restore native libraries
         timeout-minutes: 30
         shell: pwsh

.github/workflows/test-iseberg.yml

@@ -27,10 +27,6 @@ Thumbs.db
 .DS_Store
 
 ## Native libraries built from source (see native/Restore-NativeLibraries.ps1)
-native/ghostty/**/*.dll
-native/ghostty/**/*.so
-native/ghostty/**/*.dylib
-native/ghostty/**/*.sha256
 native/linux-pty/**/dt-pty-host
 native/linux-pty/**/dt-pty-host.exe
 native/noto-emoji/NotoColorEmoji.ttf

.gitignore

@@ -47,11 +47,11 @@ already the primary scripting language for Windows packaging in this repo
 ## Native helpers
 
 - Linux/macOS PTY host: `native/linux-pty` (`dt-pty-host.c`)
-- Ghostty VT library: `native/ghostty`
 - Windows Explorer/toast helpers: `native/windows-shell`
 
-`dotnet build` restores these for the host RID automatically
-(`-p:SkipNativeRestore=true` to skip).
+`dotnet build` restores `dt-pty-host` for Linux/macOS host RIDs automatically
+(Zig version pinned in `native/zig.json`; `-p:SkipNativeRestore=true` to
+skip). Windows builds have nothing to restore.
 
 ## Platform packaging entry points
 

AGENTS.md

@@ -69,13 +69,13 @@ Do not point that tool at this repository.
 ## Native helpers
 
 - Linux/macOS PTY host: `native/linux-pty` (`dt-pty-host.c`; Zig `cc` on Linux, Apple clang on macOS)
-- Ghostty VT library: `native/ghostty` (Zig build of pinned Ghostty)
 - Windows Explorer/toast helpers: `native/windows-shell` (MSVC, gitignored `bin/`)
 
-`dotnet build` restores Ghostty and `dt-pty-host` for the host RID (Zig is
-downloaded into `artifacts/tools` on first use; a system `zig` of a different
-minor version than the pinned one is ignored, so it does not break the build). See
-[`native/ghostty/README.md`](native/ghostty/README.md). Pass
+`dotnet build` restores `dt-pty-host` for Linux/macOS host RIDs; Windows builds
+have nothing to restore. The Zig version is pinned in
+[`native/zig.json`](native/zig.json); Zig is downloaded into `artifacts/tools`
+on first use, and a system `zig` of a different minor version than the pinned
+one is ignored, so it does not break the build. Pass
 `-p:SkipNativeRestore=true` to skip.
 
 ## macOS
@@ -88,7 +88,7 @@ dotnet test Devolutions.Terminal.slnx
 pwsh scripts/Build-MacOsPackage.ps1 osx-arm64 2026.3.0 artifacts/packages
 ```
 
-`dotnet build` restores Ghostty and `dt-pty-host` for `osx-arm64` / `osx-x64`.
+`dotnet build` restores `dt-pty-host` for `osx-arm64` / `osx-x64`.
 The PTY host is compiled with Apple clang against the macOS 13 SDK. App-bundle
 packaging is Darwin-only; release builds are signed and notarized with a
 Developer ID identity (see [docs/macos.md](docs/macos.md) and

CONTRIBUTING.md

@@ -3,7 +3,6 @@
     <Project Path="src/Devolutions.Terminal.Connection/Devolutions.Terminal.Connection.csproj" />
     <Project Path="src/Devolutions.Terminal.Control/Devolutions.Terminal.Control.csproj" />
     <Project Path="src/Devolutions.Terminal.Core/Devolutions.Terminal.Core.csproj" />
-    <Project Path="src/Devolutions.Terminal.Ghostty/Devolutions.Terminal.Ghostty.csproj" />
     <Project Path="src/Devolutions.Terminal.Render/Devolutions.Terminal.Render.csproj" />
     <Project Path="src/Devolutions.Terminal.Settings/Devolutions.Terminal.Settings.csproj" />
     <Project Path="src/Devolutions.Terminal.Broker/Devolutions.Terminal.Broker.csproj" />
@@ -27,7 +26,6 @@
     <Project Path="tests/Devolutions.Terminal.Connection.Tests/Devolutions.Terminal.Connection.Tests.csproj" />
     <Project Path="tests/Devolutions.Terminal.Control.Tests/Devolutions.Terminal.Control.Tests.csproj" />
     <Project Path="tests/Devolutions.Terminal.Core.Tests/Devolutions.Terminal.Core.Tests.csproj" />
-    <Project Path="tests/Devolutions.Terminal.Ghostty.Tests/Devolutions.Terminal.Ghostty.Tests.csproj" />
     <Project Path="tests/Devolutions.Terminal.Render.Tests/Devolutions.Terminal.Render.Tests.csproj" />
     <Project Path="tests/Devolutions.Terminal.Settings.Tests/Devolutions.Terminal.Settings.Tests.csproj" />
     <Project Path="tests/Devolutions.Terminal.Broker.Tests/Devolutions.Terminal.Broker.Tests.csproj" />

Devolutions.Terminal.slnx

@@ -17,11 +17,6 @@ See the license in the Cascadia Code repository.
 Vendored under `native/noto-emoji/`. Licensed under the SIL Open Font License
 1.1. See `native/noto-emoji/LICENSE`.
 
-## Ghostty (`libghostty-vt`)
-
-Pinned native VT engine binaries under `native/ghostty/`. See
-`native/ghostty/LICENSE` and `docs/ghostty-engine.md`.
-
 ## AppImage type-2 runtime
 
 Linux AppImage packages embed a pinned type-2 runtime. See

NOTICE.md

@@ -5,7 +5,7 @@ as a self-contained **NativeAOT** desktop app, and rendered with **Avalonia 12**
 
 - **ConPTY** on Windows and a real **forkpty** transport on Linux and macOS
 - Azure Cloud Shell for remote Azure sessions
-- selectable built-in or **Ghostty** VT engine
+- a built-in VT engine written in C#
 - Windows Terminal-compatible `settings.json`, actions, keybindings, and `dt` CLI
 - source-integrated **Iseberg** PowerShell ISE profiles, with execution in an
   owned PowerShell subprocess and a NativeAOT desktop
@@ -104,18 +104,13 @@ windows is unavailable, and persisted layouts are neither restored nor saved.
 It is the per-launch equivalent of Windows Terminal's
 `compatibility.isolatedMode` setting, which Windows Terminal 1.23 removed.
 
-Set `"experimental.terminalEngine": "ghostty"` to use the pinned
-`libghostty-vt` engine globally. A profile can override it with `"builtin"` or
-`"ghostty"`. ConPTY remains the Windows process transport for both engines.
-
 The compiled-XAML settings editor is documented in
 [docs/settings-editor.md](docs/settings-editor.md).
 
 ## Architecture
 
 ```
 Devolutions.Terminal.Core         VT parser + text buffer + terminal engine
-Devolutions.Terminal.Ghostty      NativeAOT-safe libghostty-vt engine adapter
 Devolutions.Terminal.Render       Immutable plans + HarfBuzz/Skia glyph renderer
 Devolutions.Terminal.Connection   ConPTY + Linux PTY + Azure Cloud Shell + browser shell
 Devolutions.Terminal.Settings     Layered Windows Terminal-compatible JSON settings

README.md

@@ -3,9 +3,8 @@
 > [!NOTE]
 > Windows local sessions use the bundled Microsoft ConPTY runtime, including
 > `OpenConsole.exe`, rather than the OS copy that filters Sixel on some Windows
-> builds. With the built-in engine, Sixel producers such as `Get-XKCD -Show`
-> can render inline images. Other transports must likewise preserve graphics
-> payloads; the optional Ghostty engine does not expose image resources.
+> builds. Sixel producers such as `Get-XKCD -Show` can therefore render inline
+> images. Other transports must likewise preserve graphics payloads.
 
 `Devolutions.Terminal.Core` parses advanced string protocols without depending on Avalonia,
 Skia, Win32, or an image codec. It exposes decoded Sixel pixels and bounded
@@ -140,7 +139,6 @@ delete or reset does not paint stale cached pixels.
 - kitty cell/z-index/number-targeted deletes (`d=c/x/y/z/n`) — silent no-op;
   the cursor for `f=100` images without `r` stays put because Core retains codec
   bytes without decoding dimensions
-- Ghostty image projection (the pinned C ABI exposes no image resources)
 
 These gaps avoid remote I/O and renderer/input dependencies while keeping every
 implemented parser and downloadable resource path bounded.