microsoft · Mitch Denny (mitchdenny) · Jun 10, 2026 · Apr 20, 2026 · Apr 20, 2026 · Apr 20, 2026
diff --git a/Aspire.slnx b/Aspire.slnx
@@ -81,6 +81,7 @@
     <Project Path="src/Aspire.Hosting.Blazor/Aspire.Hosting.Blazor.csproj" />
     <Project Path="src/Aspire.Hosting.Yarp/Aspire.Hosting.Yarp.csproj" />
     <Project Path="src/Aspire.Hosting/Aspire.Hosting.csproj" />
+    <Project Path="src/Aspire.TerminalHost/Aspire.TerminalHost.csproj" />
     <Project Path="src/Aspire.TypeSystem/Aspire.TypeSystem.csproj" />
     <Project Path="src/Aspire.ProjectTemplates/Aspire.ProjectTemplates.csproj" />
   </Folder>
@@ -383,6 +384,10 @@
     <Project Path="playground/Stress/Stress.Empty/Stress.Empty.csproj" />
     <Project Path="playground/Stress/Stress.TelemetryService/Stress.TelemetryService.csproj" />
   </Folder>
+  <Folder Name="/playground/Terminals/">
+    <Project Path="playground/Terminals/Terminals.AppHost/Terminals.AppHost.csproj" />
+    <Project Path="playground/Terminals/Terminals.Repl/Terminals.Repl.csproj" />
+  </Folder>
   <Folder Name="/playground/Testing/">
     <Project Path="playground/Testing/Testing.Tests/Testing.Tests.csproj" />
   </Folder>
@@ -536,6 +541,7 @@
     <Project Path="tests/Aspire.Hosting.SqlServer.Tests/Aspire.Hosting.SqlServer.Tests.csproj" />
     <Project Path="tests/Aspire.Hosting.Testing.Tests/Aspire.Hosting.Testing.Tests.csproj" />
     <Project Path="tests/Aspire.Hosting.Tests/Aspire.Hosting.Tests.csproj" />
+    <Project Path="tests/Aspire.TerminalHost.Tests/Aspire.TerminalHost.Tests.csproj" />
     <Project Path="tests/Aspire.Hosting.Valkey.Tests/Aspire.Hosting.Valkey.Tests.csproj" />
     <Project Path="tests/Aspire.Hosting.Blazor.Tests/Aspire.Hosting.Blazor.Tests.csproj" />
     <Project Path="tests/Aspire.Hosting.Yarp.Tests/Aspire.Hosting.Yarp.Tests.csproj" />

diff --git a/Directory.Build.props b/Directory.Build.props
@@ -32,6 +32,7 @@
     <SkipAspireWorkloadManifest>true</SkipAspireWorkloadManifest>
 
     <DashboardPublishedArtifactsOutputDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsDir)', 'DashboardArtifacts', '$(Configuration)'))</DashboardPublishedArtifactsOutputDir>
+    <TerminalHostPublishedArtifactsOutputDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsDir)', 'TerminalHostArtifacts', '$(Configuration)'))</TerminalHostPublishedArtifactsOutputDir>
     <WorkloadsPackageSource>$(ArtifactsShippingPackagesDir)</WorkloadsPackageSource>
 
     <!-- Issue: https://github.com/microsoft/aspire/issues/8488 -->
@@ -55,6 +56,7 @@
     <!-- TODO: Need to figure out we can automatically detect target framework here. This property
                is specified to support dashboard path metadata generation on the inner loop. -->
     <AspireDashboardDir>$(MSBuildThisFileDirectory)/artifacts/bin/Aspire.Dashboard/$(Configuration)/net8.0/</AspireDashboardDir>
+    <AspireTerminalHostDir>$(MSBuildThisFileDirectory)/artifacts/bin/Aspire.TerminalHost/$(Configuration)/net8.0/</AspireTerminalHostDir>
   </PropertyGroup>
 
 </Project>
diff --git a/Directory.Packages.props b/Directory.Packages.props
@@ -101,9 +101,9 @@
     <PackageVersion Include="Grpc.AspNetCore" Version="2.80.0" />
     <PackageVersion Include="Grpc.Net.ClientFactory" Version="2.80.0" />
     <PackageVersion Include="Grpc.Tools" Version="2.80.0" />
-    <PackageVersion Include="Hex1b" Version="0.154.0" />
-    <PackageVersion Include="Hex1b.McpServer" Version="0.154.0" />
-    <PackageVersion Include="Hex1b.Tool" Version="0.154.0" />
+    <PackageVersion Include="Hex1b" Version="0.163.0" />
+    <PackageVersion Include="Hex1b.McpServer" Version="0.163.0" />
+    <PackageVersion Include="Hex1b.Tool" Version="0.163.0" />
     <PackageVersion Include="Humanizer.Core" Version="3.0.10" />
     <PackageVersion Include="KubernetesClient" Version="19.0.2" />
     <PackageVersion Include="JsonPatch.Net" Version="5.0.2" />

diff --git a/THIRD-PARTY-NOTICES.TXT b/THIRD-PARTY-NOTICES.TXT
@@ -194,3 +194,127 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+
+License notice for Cascadia Code
+----------------------------------------------------------------------------------------------
+
+Copyright (c) 2019 - Present, Microsoft Corporation,
+with Reserved Font Name Cascadia Code.
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
+
+
+License notice for xterm.js
+----------------------------------------------------------------------------------------------
+
+Copyright (c) 2017-2019, The xterm.js authors (https://github.com/xtermjs/xterm.js)
+Copyright (c) 2014-2016, SourceLair Private Company (https://www.sourcelair.com)
+Copyright (c) 2012-2013, Christopher Jeffrey (https://github.com/chjj/)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/docs/specs/with-terminal.md b/docs/specs/with-terminal.md
@@ -0,0 +1,166 @@
+# `WithTerminal()` — Aspire interactive terminal architecture
+
+**Status:** Implemented for Aspire 13.4 (Windows executables).
+**Issue:** [microsoft/aspire#16317](https://github.com/microsoft/aspire/issues/16317)
+**DCP integration:** [microsoft/dcp#133](https://github.com/microsoft/dcp/pull/133)
+
+## Goal
+
+Let an Aspire AppHost author opt any executable or container resource into
+interactive terminal access:
+
+```csharp
+builder.AddProject<Projects.MyAgent>("agent")
+    .WithReplicas(2)
+    .WithTerminal();
+```
+
+The dashboard then renders an xterm.js terminal per replica, and the CLI
+exposes the same session as `aspire terminal agent --replica 0`.
+
+## Process topology
+
+```text
+                                ┌────────────────────────────┐
+                                │  AppHost (dotnet run)      │
+                                │  - Aspire.Hosting          │
+                                │  - DCP control plane       │
+                                │  - per-replica:            │
+                                │    Aspire.TerminalHost     │  (1 process per replica)
+                                └─────────────┬──────────────┘
+                                              │ spawn
+                                              ▼
+┌──────────────────────┐                ┌───────────────────────┐                ┌────────────────────────┐
+│  DCP-launched        │   PTY          │  TerminalHost         │   HMP v1 UDS   │  Consumers             │
+│  replica process     │ ─────────────▶ │  (Hex1b HMP v1 broker) │ ─────────────▶ │  - Dashboard          │
+│  (executable, repl…) │ ◀───── stdin ─ │                       │ ◀───── input ─ │    /api/terminal proxy │
+└──────────────────────┘                └───────────────────────┘                │  - aspire CLI          │
+                                                                                  └────────────────────────┘
+```
+
+Three actors and three socket roles:
+
+| Actor          | Socket              | Direction                        | Lifetime |
+|----------------|---------------------|----------------------------------|----------|
+| **DCP**        | `producerUdsPath`   | DCP → host (PTY bytes + control) | Per replica |
+| **TerminalHost** | `consumerUdsPath` | host → consumers (broadcast)     | Per replica |
+| **TerminalHost** | `controlUdsPath`  | AppHost → host (lifecycle, stats)| Per replica |
+
+The producer/consumer split lets multiple consumers (dashboard + multiple CLI
+sessions) attach simultaneously without coupling DCP to consumer counts.
+
+## Wire protocol
+
+We do **not** define a custom protocol. The terminal traffic uses
+[Hex1b](https://github.com/dotnet/hex1b)'s `HMP v1` (Hex Multiplex Protocol,
+version 1), which already handles:
+
+- VT byte streaming with backpressure
+- Resize requests in both directions
+- Hello/StateSync replay so a late-attaching consumer sees the current
+  scrollback
+- Connection lifecycle (close, disconnect, reconnect)
+- Authenticated stream factory hooks (we only use Unix-socket transport
+  today)
+
+The `Hmp1WorkloadAdapter` is what the AppHost-side terminal host uses to
+multiplex DCP's PTY traffic to the consumer-facing listener; the
+`Hmp1PresentationAdapter` is what consumers (Dashboard WebSocket proxy and
+the CLI) use to attach.
+
+## Property contract (gRPC `ResourceService` snapshots)
+
+When `WithTerminal()` is applied to a resource, every replica snapshot
+emitted by the dashboard service carries four properties:
+
+| Key                       | Sensitivity     | Meaning                                      |
+|---------------------------|-----------------|----------------------------------------------|
+| `terminal.enabled`        | non-sensitive   | Marker. `"true"` when the replica has a PTY. |
+| `terminal.replicaIndex`   | non-sensitive   | 0-based stable index from `DcpInstancesAnnotation`. |
+| `terminal.replicaCount`   | non-sensitive   | Total replicas for the parent resource.      |
+| `terminal.consumerUdsPath`| **sensitive**   | The local UDS that consumers connect to.     |
+
+The consumer UDS path is marked `IsSensitive=true` so the dashboard UI masks
+the value in the property list. The path still rides the gRPC stream because
+the dashboard's WebSocket proxy needs it server-side to resolve
+`?resource=&replica=` query parameters into a real socket; the path is never
+echoed back to the browser.
+
+## Dashboard `/api/terminal` WebSocket endpoint
+
+Authenticated (`RequireAuthorization(FrontendAuthorizationDefaults.PolicyName)`)
+endpoint at `/api/terminal?resource=<displayName>&replica=<index>`.
+
+`TerminalWebSocketProxy` resolves the connection entirely server-side:
+
+1. `ITerminalConnectionResolver.ConnectAsync(resourceName, replicaIndex, ct)`
+   walks `IDashboardClient.GetResources()`, matches by `DisplayName` +
+   `TryGetTerminalReplicaInfo`, and connects via
+   `Hmp1Transports.ConnectUnixSocket(consumerUdsPath, ct)`.
+2. The proxy wraps the resulting stream in `Hmp1WorkloadAdapter` and runs
+   two pumps:
+   - **Inbound (browser → producer):** binary frames are forwarded as HMP v1
+     `Input` (keystrokes); text frames are parsed as JSON resize control
+     messages (`{"type":"resize","cols":N,"rows":N}`).
+   - **Outbound (producer → browser):** VT bytes from the producer become
+     binary WebSocket frames; resize hints from the producer become JSON
+     text frames.
+3. Frame type — not content — distinguishes keystroke from control. This
+   keeps the proxy's parser cheap and avoids ambiguity around binary input
+   that happens to look like JSON.
+4. Multi-fragment WS reads are reassembled in `ReassembledFrame` using
+   `ArrayPool<byte>`.
+
+The browser never sees `consumerUdsPath` and cannot induce the dashboard
+to connect to an arbitrary local socket — it can only ask for
+`(resource, replica)` pairs that are present in the resource snapshot
+stream.
+
+## CLI
+
+`aspire terminal <resource> [--replica N]` (`Aspire.Cli/Commands/TerminalCommand.cs`)
+opens its own `Hmp1PresentationAdapter` against the consumer UDS path
+returned by `IBackchannel.GetTerminalInfoAsync(resource, replica)` and
+renders frames into the host terminal via Hex1b's `Hex1bTerminal`. When the
+resource has more than one replica and the CLI is interactive, it prompts
+for a selection; in non-interactive mode the `--replica` flag is required.
+
+## DCP integration
+
+For each replica of a `WithTerminal()` resource, DCP allocates a pseudo-terminal
+when the executable (or container) spec carries a populated `terminal` block:
+
+```json
+{
+  "terminal": {
+    "udsPath":    "/run/user/1000/aspire/trmnl/<run-id>/<resource>-<idx>/producer.sock",
+    "socketMode": "connect",
+    "cols":       120,
+    "rows":       30
+  }
+}
+```
+
+`socketMode: "connect"` tells DCP to dial the named UDS (the TerminalHost
+process owns the listener). The dimensions are the initial PTY size; both
+sides exchange resize frames over HMP afterwards.
+
+Desktop PTY support is implemented across all three platforms (Unix98 `/dev/ptmx` on Linux and macOS; ConPTY on Windows). Container PTYs are tracked
+as a Phase 3 follow-up on the parent issue.
+
+## Files of interest
+
+| Concern                              | File                                                                |
+|--------------------------------------|---------------------------------------------------------------------|
+| Public API entry point               | `src/Aspire.Hosting/TerminalResourceBuilderExtensions.cs`           |
+| Per-resource hidden host resource    | `src/Aspire.Hosting/ApplicationModel/TerminalHostResource.cs`       |
+| DCP wire-up                          | `src/Aspire.Hosting/Dcp/ExecutableCreator.cs`                       |
+| Backchannel `GetTerminalInfoAsync`   | `src/Aspire.Hosting/Backchannel/AuxiliaryBackchannelRpcTarget.cs`   |
+| Snapshot stamping                    | `src/Aspire.Hosting/Dashboard/DashboardServiceData.cs`              |
+| TerminalHost process                 | `src/Aspire.TerminalHost/`                                          |
+| CLI command                          | `src/Aspire.Cli/Commands/TerminalCommand.cs`                        |
+| Dashboard WebSocket proxy            | `src/Aspire.Dashboard/Terminal/TerminalWebSocketProxy.cs`           |
+| Dashboard resolver                   | `src/Aspire.Dashboard/Terminal/DefaultTerminalConnectionResolver.cs`|
+| `TerminalView` (xterm.js host)       | `src/Aspire.Dashboard/Components/Controls/TerminalView.razor.*`     |
+| Property keys                        | `src/Shared/Model/KnownProperties.cs` (`Terminal.*`)                |
+| Playground sample                    | `playground/Terminals/Terminals.AppHost/AppHost.cs`                 |