From d1413fc71edf753f19228ec2617bf90998c6a875 Mon Sep 17 00:00:00 2001
From: Rickylabs <eric.chautems@gmail.com>
Date: Thu, 2 Jul 2026 18:37:27 +0200
Subject: [PATCH 1/2] Add Deno toolchain support for TypeScript AppHosts

Extends the CLI TypeScript AppHost toolchain resolver to detect and drive
a Deno toolchain, mirroring the existing npm/bun/yarn/pnpm support.

- Detect Deno via a `packageManager: "deno@x"` hint or deno.lock/deno.json/
  deno.jsonc markers (before the npm package-lock fallback).
- Generate `deno install`, `deno check {appHostFile}` (native no-emit
  type-check), `deno run -A {appHostFile}`, and `deno run -A --check --watch
  {appHostFile}`. Deno is not permissive for package.json projects, so `-A`
  grants the host access the AppHost needs; `--check` makes each watch restart
  type-check to match the nodemon "typecheck && run" behavior. The native
  watcher replaces nodemon.
- Root delegate scripts use `deno task --cwd <dir> <script>` (Deno has no
  `run <script>` for package.json scripts).
- Register deno in CommandPathResolver, the missing-tool warning, and the E2E
  toolchain helpers; make the watch-mode banner assertion toolchain-aware
  (Deno prints "Watcher Process started." instead of nodemon's banner).
- Install a pinned Deno 2.9.0 in the e2e and polyglot-base Docker images.

The doctor tooling check needs no change as it drives off the resolver and
CommandPathResolver.
---
 .../TypeScriptAppHostToolchainResolver.cs     | 48 +++++++++++++++-
 .../Scaffolding/ScaffoldingService.cs         |  3 +
 src/Aspire.Cli/Utils/CommandPathResolver.cs   |  3 +-
 .../Utils/MissingJavaScriptToolWarning.cs     |  3 +-
 .../TypeScriptAppHostToolchainTestHelpers.cs  | 28 ++++++++-
 .../TypeScriptPolyglotTests.cs                |  5 +-
 .../TypeScriptAppHostToolingCheckTests.cs     |  2 +
 ...TypeScriptAppHostToolchainResolverTests.cs | 57 +++++++++++++++++++
 .../Utils/CommandPathResolverTests.cs         |  2 +
 .../MissingJavaScriptToolWarningTests.cs      |  1 +
 tests/Shared/Docker/Dockerfile.e2e            |  2 +
 .../Docker/Dockerfile.e2e-polyglot-base       |  4 +-
 12 files changed, 150 insertions(+), 8 deletions(-)

diff --git a/src/Aspire.Cli/Projects/TypeScriptAppHostToolchainResolver.cs b/src/Aspire.Cli/Projects/TypeScriptAppHostToolchainResolver.cs
index 407ce55fe9a..ea1c245a40f 100644
--- a/src/Aspire.Cli/Projects/TypeScriptAppHostToolchainResolver.cs
+++ b/src/Aspire.Cli/Projects/TypeScriptAppHostToolchainResolver.cs
@@ -15,7 +15,8 @@ internal enum TypeScriptAppHostToolchain
     Npm,
     Bun,
     Yarn,
-    Pnpm
+    Pnpm,
+    Deno
 }
 
 internal static class TypeScriptAppHostToolchainResolver
@@ -28,6 +29,9 @@ internal static class TypeScriptAppHostToolchainResolver
     private const string YarnConfigFileName = ".yarnrc.yml";
     private const string PackageLockFileName = "package-lock.json";
     private const string PnpmLockFileName = "pnpm-lock.yaml";
+    private const string DenoLockFileName = "deno.lock";
+    private const string DenoJsonFileName = "deno.json";
+    private const string DenoJsoncFileName = "deno.jsonc";
 
     public static bool IsTypeScriptLanguage(LanguageInfo? language)
     {
@@ -87,6 +91,21 @@ internal static TypeScriptAppHostToolchainResolution ResolveWithReason(Directory
                 return CreateLockFileResolution(TypeScriptAppHostToolchain.Yarn, YarnConfigFileName, candidateDirectory);
             }
 
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoLockFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoLockFileName, candidateDirectory);
+            }
+
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoJsonFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoJsonFileName, candidateDirectory);
+            }
+
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoJsoncFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoJsoncFileName, candidateDirectory);
+            }
+
             if (File.Exists(Path.Combine(candidateDirectory.FullName, PackageLockFileName)))
             {
                 return CreateLockFileResolution(TypeScriptAppHostToolchain.Npm, PackageLockFileName, candidateDirectory);
@@ -113,6 +132,7 @@ public static string GetCommandName(TypeScriptAppHostToolchain toolchain)
             TypeScriptAppHostToolchain.Bun => "bun",
             TypeScriptAppHostToolchain.Yarn => "yarn",
             TypeScriptAppHostToolchain.Pnpm => "pnpm",
+            TypeScriptAppHostToolchain.Deno => "deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -130,6 +150,7 @@ public static string GetDisplayName(TypeScriptAppHostToolchain toolchain)
             TypeScriptAppHostToolchain.Bun => "Bun",
             TypeScriptAppHostToolchain.Yarn => "Yarn",
             TypeScriptAppHostToolchain.Pnpm => "pnpm",
+            TypeScriptAppHostToolchain.Deno => "Deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -198,6 +219,13 @@ private static CommandSpec[] CreatePreExecuteCommands(TypeScriptAppHostToolchain
                     Command = "pnpm",
                     Args = ["exec", "tsc", "--noEmit", "-p", tsConfigFileName]
                 },
+                // Deno type-checks with its own compiler and config (deno.json), so there is no
+                // tsc/tsconfig step. `deno check` is the native no-emit type-check over the AppHost graph.
+                TypeScriptAppHostToolchain.Deno => new CommandSpec
+                {
+                    Command = "deno",
+                    Args = ["check", "{appHostFile}"]
+                },
                 _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
             }
         ];
@@ -222,6 +250,15 @@ private static CommandSpec CreateExecuteCommand(TypeScriptAppHostToolchain toolc
                 Command = "pnpm",
                 Args = ["exec", "tsx", "--tsconfig", tsConfigFileName, "{appHostFile}"]
             },
+            // Deno runs the AppHost as its own runtime (no tsx transpiler). Unlike Node/Bun, Deno is
+            // not permissive for package.json projects: APIs like Deno.env/Deno.serve throw NotCapable
+            // without flags (and error non-interactively rather than prompting). The AppHost needs
+            // full host access, so `-A` grants all permissions, mirroring how Node/Bun run unrestricted.
+            TypeScriptAppHostToolchain.Deno => new CommandSpec
+            {
+                Command = "deno",
+                Args = ["run", "-A", "{appHostFile}"]
+            },
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -275,6 +312,14 @@ private static CommandSpec CreateWatchCommand(TypeScriptAppHostToolchain toolcha
                     "--exec", $"pnpm exec tsc --noEmit -p {tsConfigFileName} && pnpm exec tsx --tsconfig {tsConfigFileName} \"{{appHostFile}}\""
                 ]
             },
+            // Deno has a native file watcher, so nodemon is unnecessary. `--check` makes each restart
+            // type-check before running, matching the nodemon "tsc --noEmit && run" behavior other
+            // toolchains emulate. `-A` grants full permissions as on the non-watch execute command.
+            TypeScriptAppHostToolchain.Deno => new CommandSpec
+            {
+                Command = "deno",
+                Args = ["run", "-A", "--check", "--watch", "{appHostFile}"]
+            },
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -344,6 +389,7 @@ private static bool TryParseToolchain(string packageManagerName, out TypeScriptA
             "bun" => TypeScriptAppHostToolchain.Bun,
             "yarn" => TypeScriptAppHostToolchain.Yarn,
             "pnpm" => TypeScriptAppHostToolchain.Pnpm,
+            "deno" => TypeScriptAppHostToolchain.Deno,
             _ => null
         };
 
diff --git a/src/Aspire.Cli/Scaffolding/ScaffoldingService.cs b/src/Aspire.Cli/Scaffolding/ScaffoldingService.cs
index 5aca9475e51..908671703af 100644
--- a/src/Aspire.Cli/Scaffolding/ScaffoldingService.cs
+++ b/src/Aspire.Cli/Scaffolding/ScaffoldingService.cs
@@ -382,6 +382,9 @@ private static string CreateRootDelegateScript(TypeScriptAppHostToolchain toolch
             TypeScriptAppHostToolchain.Pnpm => $"pnpm --dir {relativeAppHostDirectory} run {scriptName}",
             TypeScriptAppHostToolchain.Yarn => $"yarn --cwd {relativeAppHostDirectory} run {scriptName}",
             TypeScriptAppHostToolchain.Bun => $"bun --cwd {relativeAppHostDirectory} run {scriptName}",
+            // Deno has no `run <script>` for package.json scripts; `deno task` runs them and `--cwd`
+            // scopes the task to the nested AppHost package, mirroring npm's `--prefix`.
+            TypeScriptAppHostToolchain.Deno => $"deno task --cwd {relativeAppHostDirectory} {scriptName}",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
diff --git a/src/Aspire.Cli/Utils/CommandPathResolver.cs b/src/Aspire.Cli/Utils/CommandPathResolver.cs
index 9ca112acea2..dcb1cfab894 100644
--- a/src/Aspire.Cli/Utils/CommandPathResolver.cs
+++ b/src/Aspire.Cli/Utils/CommandPathResolver.cs
@@ -14,7 +14,8 @@ internal static class CommandPathResolver
         ["npx"] = new("Node.js", "https://nodejs.org/en/download"),
         ["bun"] = new("Bun", "https://bun.sh/docs/installation"),
         ["yarn"] = new("Yarn", "https://yarnpkg.com/getting-started/install"),
-        ["pnpm"] = new("pnpm", "https://pnpm.io/installation")
+        ["pnpm"] = new("pnpm", "https://pnpm.io/installation"),
+        ["deno"] = new("Deno", "https://docs.deno.com/runtime/getting_started/installation/")
     };
 
     /// <summary>
diff --git a/src/Aspire.Cli/Utils/MissingJavaScriptToolWarning.cs b/src/Aspire.Cli/Utils/MissingJavaScriptToolWarning.cs
index 6f5735451df..b912f6f7c18 100644
--- a/src/Aspire.Cli/Utils/MissingJavaScriptToolWarning.cs
+++ b/src/Aspire.Cli/Utils/MissingJavaScriptToolWarning.cs
@@ -15,7 +15,8 @@ internal static class MissingJavaScriptToolWarning
         "npx is not installed or not found in PATH.",
         "bun is not installed or not found in PATH.",
         "yarn is not installed or not found in PATH.",
-        "pnpm is not installed or not found in PATH."
+        "pnpm is not installed or not found in PATH.",
+        "deno is not installed or not found in PATH."
     ];
 
     public static bool IsMatch(IEnumerable<(OutputLineStream Stream, string Line)> lines)
diff --git a/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs b/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
index 0ae163641c6..0aa57cbd2b7 100644
--- a/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
+++ b/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
@@ -46,7 +46,7 @@ internal static void SetPackageManager(string projectRoot, string toolchain, boo
             return;
         }
 
-        foreach (var lockFileName in new[] { "package-lock.json", "bun.lock", "bun.lockb", "pnpm-lock.yaml", "yarn.lock" })
+        foreach (var lockFileName in new[] { "package-lock.json", "bun.lock", "bun.lockb", "pnpm-lock.yaml", "yarn.lock", "deno.lock" })
         {
             var lockFilePath = Path.Combine(projectRoot, lockFileName);
             if (File.Exists(lockFilePath))
@@ -80,6 +80,8 @@ internal static string GetTypeCheckCommand(string toolchain, string tsConfigFile
             "yarn" => $"yarn run tsc --noEmit -p {tsConfigFileName}",
             "pnpm" => $"pnpm exec tsc --noEmit -p {tsConfigFileName}",
             "npm" => $"npx --no-install tsc --noEmit -p {tsConfigFileName}",
+            // Deno type-checks with its own compiler over the AppHost graph; there is no tsc/tsconfig step.
+            "deno" => "deno check apphost.mts",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -87,7 +89,24 @@ internal static string GetTypeCheckCommand(string toolchain, string tsConfigFile
     /// Gets the script runner command for a toolchain.
     /// </summary>
     internal static string GetRunScriptCommand(string toolchain, string scriptName) =>
-        $"{GetCommandName(toolchain)} run {scriptName}";
+        NormalizeToolchain(toolchain) switch
+        {
+            // Deno runs package.json scripts via `deno task`, not `deno run` (which runs a file).
+            "deno" => $"deno task {scriptName}",
+            _ => $"{GetCommandName(toolchain)} run {scriptName}"
+        };
+
+    /// <summary>
+    /// Gets the console text that indicates watch mode is active for a toolchain.
+    /// Node-based toolchains use nodemon; Deno uses its native file watcher, which prints
+    /// a different banner.
+    /// </summary>
+    internal static string GetWatchModeReadyText(string toolchain) =>
+        NormalizeToolchain(toolchain) switch
+        {
+            "deno" => "Watcher Process started.",
+            _ => "Watching for file changes."
+        };
 
     /// <summary>
     /// Gets the primary lock file name a toolchain should produce after restore/install.
@@ -99,6 +118,7 @@ internal static string GetLockFileName(string toolchain) =>
             "yarn" => "yarn.lock",
             "pnpm" => "pnpm-lock.yaml",
             "npm" => "package-lock.json",
+            "deno" => "deno.lock",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -114,6 +134,7 @@ internal static string GetPackageManager(string toolchain) =>
             "yarn" => "yarn@4.14.1",
             "pnpm" => "pnpm@10.0.0",
             "npm" => "npm@10.0.0",
+            "deno" => "deno@2.9.0",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -132,6 +153,7 @@ internal static string GetDisplayName(string toolchain) =>
             "yarn" => "Yarn",
             "pnpm" => "pnpm",
             "npm" => "Node.js",
+            "deno" => "Deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -147,6 +169,7 @@ internal static string GetInstallationLink(string toolchain) =>
             "yarn" => "https://yarnpkg.com/getting-started/install",
             "pnpm" => "https://pnpm.io/installation",
             "npm" => "https://nodejs.org/en/download",
+            "deno" => "https://docs.deno.com/runtime/getting_started/installation/",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -180,6 +203,7 @@ private static string GetCommandName(string toolchain) =>
             "yarn" => "yarn",
             "pnpm" => "pnpm",
             "npm" => "npm",
+            "deno" => "deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
diff --git a/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptPolyglotTests.cs b/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptPolyglotTests.cs
index ff58a271311..1959ca724d6 100644
--- a/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptPolyglotTests.cs
+++ b/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptPolyglotTests.cs
@@ -22,7 +22,8 @@ public sealed class TypeScriptPolyglotTests(ITestOutputHelper output)
         "npm",
         "bun",
         "yarn",
-        "pnpm"
+        "pnpm",
+        "deno"
     };
 
     [Theory]
@@ -289,7 +290,7 @@ public async Task GeneratedAspireDevScript_StartsWatchMode_WithConfiguredToolcha
         await auto.TypeAsync(TypeScriptAppHostToolchainTestHelpers.GetRunScriptCommand(toolchain, "aspire:dev"));
         await auto.EnterAsync();
         await auto.WaitUntilAsync(
-            s => s.ContainsText("Watching for file changes."),
+            s => s.ContainsText(TypeScriptAppHostToolchainTestHelpers.GetWatchModeReadyText(toolchain)),
             timeout: TimeSpan.FromMinutes(2),
             description: $"{toolchain} watch mode to start");
 
diff --git a/tests/Aspire.Cli.Tests/Commands/TypeScriptAppHostToolingCheckTests.cs b/tests/Aspire.Cli.Tests/Commands/TypeScriptAppHostToolingCheckTests.cs
index d321df4070b..55fe005d90b 100644
--- a/tests/Aspire.Cli.Tests/Commands/TypeScriptAppHostToolingCheckTests.cs
+++ b/tests/Aspire.Cli.Tests/Commands/TypeScriptAppHostToolingCheckTests.cs
@@ -25,6 +25,7 @@ public sealed class TypeScriptAppHostToolingCheckTests(ITestOutputHelper outputH
     [InlineData("bun@1.2.0", nameof(TypeScriptAppHostToolchain.Bun))]
     [InlineData("yarn@4.14.1", nameof(TypeScriptAppHostToolchain.Yarn))]
     [InlineData("pnpm@10.12.1", nameof(TypeScriptAppHostToolchain.Pnpm))]
+    [InlineData("deno@2.9.0", nameof(TypeScriptAppHostToolchain.Deno))]
     public async Task CheckAsync_ReturnsPass_WhenConfiguredToolchainIsAvailable(string packageManagerSpec, string toolchainName)
     {
         var toolchain = Enum.Parse<TypeScriptAppHostToolchain>(toolchainName);
@@ -54,6 +55,7 @@ public async Task CheckAsync_ReturnsPass_WhenConfiguredToolchainIsAvailable(stri
     [InlineData("bun@1.2.0", nameof(TypeScriptAppHostToolchain.Bun), "Bun", "https://bun.sh/docs/installation")]
     [InlineData("yarn@4.14.1", nameof(TypeScriptAppHostToolchain.Yarn), "Yarn", "https://yarnpkg.com/getting-started/install")]
     [InlineData("pnpm@10.12.1", nameof(TypeScriptAppHostToolchain.Pnpm), "pnpm", "https://pnpm.io/installation")]
+    [InlineData("deno@2.9.0", nameof(TypeScriptAppHostToolchain.Deno), "Deno", "https://docs.deno.com/runtime/getting_started/installation/")]
     public async Task CheckAsync_ReturnsFail_WhenConfiguredToolchainIsMissing(
         string packageManagerSpec,
         string toolchainName,
diff --git a/tests/Aspire.Cli.Tests/Projects/TypeScriptAppHostToolchainResolverTests.cs b/tests/Aspire.Cli.Tests/Projects/TypeScriptAppHostToolchainResolverTests.cs
index fcc4e821c93..84440ad2694 100644
--- a/tests/Aspire.Cli.Tests/Projects/TypeScriptAppHostToolchainResolverTests.cs
+++ b/tests/Aspire.Cli.Tests/Projects/TypeScriptAppHostToolchainResolverTests.cs
@@ -22,6 +22,43 @@ public void Resolve_WhenPackageManagerIsBun_ReturnsBun()
         Assert.Equal(TypeScriptAppHostToolchain.Bun, toolchain);
     }
 
+    [Fact]
+    public void Resolve_WhenPackageManagerIsDeno_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"packageManager\": \"deno@2.9.0\" }");
+
+        var toolchain = TypeScriptAppHostToolchainResolver.Resolve(workspace.WorkspaceRoot, new TestEnvironment(), logger: null);
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, toolchain);
+    }
+
+    [Fact]
+    public void Resolve_WhenDenoLockExists_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"name\": \"apphost\" }");
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "deno.lock"), "{ \"version\": \"5\" }");
+
+        var resolution = TypeScriptAppHostToolchainResolver.ResolveWithReason(workspace.WorkspaceRoot, new TestEnvironment());
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, resolution.Toolchain);
+        Assert.Equal($"deno.lock found in {workspace.WorkspaceRoot.FullName}", resolution.Reason);
+    }
+
+    [Fact]
+    public void Resolve_WhenDenoJsonExists_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"name\": \"apphost\" }");
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "deno.json"), "{}");
+
+        var resolution = TypeScriptAppHostToolchainResolver.ResolveWithReason(workspace.WorkspaceRoot, new TestEnvironment());
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, resolution.Toolchain);
+        Assert.Equal($"deno.json found in {workspace.WorkspaceRoot.FullName}", resolution.Reason);
+    }
+
     [Fact]
     public void Resolve_WhenPnpmLockExists_ReturnsPnpm()
     {
@@ -346,6 +383,26 @@ public void ApplyToRuntimeSpec_WhenPnpmSelected_UsesPnpmTypeCheckCommands()
         Assert.Contains("pnpm exec tsc --noEmit -p tsconfig.apphost.json && pnpm exec tsx --tsconfig tsconfig.apphost.json \"{appHostFile}\"", runtimeSpec.WatchExecute?.Args ?? []);
     }
 
+    [Fact]
+    public void ApplyToRuntimeSpec_WhenDenoSelected_UsesDenoRunCommands()
+    {
+        var baseRuntimeSpec = CreateBaseRuntimeSpec();
+
+        var runtimeSpec = TypeScriptAppHostToolchainResolver.ApplyToRuntimeSpec(baseRuntimeSpec, TypeScriptAppHostToolchain.Deno);
+
+        Assert.Equal("TypeScript (Deno)", runtimeSpec.DisplayName);
+        Assert.Equal("deno", runtimeSpec.InstallDependencies?.Command);
+        Assert.Equal(["install"], runtimeSpec.InstallDependencies!.Args);
+        var preExecute = Assert.Single(runtimeSpec.PreExecute!);
+        Assert.Equal("deno", preExecute.Command);
+        Assert.Equal(["check", "{appHostFile}"], preExecute.Args);
+        Assert.Equal("deno", runtimeSpec.Execute.Command);
+        Assert.Equal(["run", "-A", "{appHostFile}"], runtimeSpec.Execute.Args);
+        Assert.Equal("deno", runtimeSpec.WatchExecute?.Command);
+        Assert.Equal(["run", "-A", "--check", "--watch", "{appHostFile}"], runtimeSpec.WatchExecute!.Args);
+        Assert.Equal("node", runtimeSpec.ExtensionLaunchCapability);
+    }
+
     private static RuntimeSpec CreateBaseRuntimeSpec()
     {
         return new RuntimeSpec
diff --git a/tests/Aspire.Cli.Tests/Utils/CommandPathResolverTests.cs b/tests/Aspire.Cli.Tests/Utils/CommandPathResolverTests.cs
index ae8f809d053..1d10b5572ea 100644
--- a/tests/Aspire.Cli.Tests/Utils/CommandPathResolverTests.cs
+++ b/tests/Aspire.Cli.Tests/Utils/CommandPathResolverTests.cs
@@ -16,6 +16,7 @@ public class CommandPathResolverTests
     [InlineData("bun.cmd", "bun is not installed or not found in PATH. Please install Bun and try again.")]
     [InlineData("yarn", "yarn is not installed or not found in PATH. Please install Yarn and try again.")]
     [InlineData("pnpm", "pnpm is not installed or not found in PATH. Please install pnpm and try again.")]
+    [InlineData("deno", "deno is not installed or not found in PATH. Please install Deno and try again.")]
     public void TryResolveCommand_WhenJavaScriptCommandIsMissing_ReturnsToolSpecificInstallMessage(string command, string expectedMessage)
     {
         static string? MissingCommandResolver(string _) => null;
@@ -57,6 +58,7 @@ public void TryResolveCommand_WhenCommandExists_ReturnsResolvedPath()
     [InlineData("bun", "https://bun.sh/docs/installation")]
     [InlineData("yarn", "https://yarnpkg.com/getting-started/install")]
     [InlineData("pnpm", "https://pnpm.io/installation")]
+    [InlineData("deno", "https://docs.deno.com/runtime/getting_started/installation/")]
     public void GetInstallationLink_WhenJavaScriptCommandKnown_ReturnsExpectedLink(string command, string expectedLink)
     {
         Assert.Equal(expectedLink, CommandPathResolver.GetInstallationLink(command));
diff --git a/tests/Aspire.Cli.Tests/Utils/MissingJavaScriptToolWarningTests.cs b/tests/Aspire.Cli.Tests/Utils/MissingJavaScriptToolWarningTests.cs
index 77ff2dba052..3051d8af99a 100644
--- a/tests/Aspire.Cli.Tests/Utils/MissingJavaScriptToolWarningTests.cs
+++ b/tests/Aspire.Cli.Tests/Utils/MissingJavaScriptToolWarningTests.cs
@@ -22,6 +22,7 @@ public class MissingJavaScriptToolWarningTests(ITestOutputHelper outputHelper)
     [InlineData("bun is not installed or not found in PATH. Please install Bun and try again.")]
     [InlineData("yarn is not installed or not found in PATH. Please install Yarn and try again.")]
     [InlineData("pnpm is not installed or not found in PATH. Please install pnpm and try again.")]
+    [InlineData("deno is not installed or not found in PATH. Please install Deno and try again.")]
     public void IsMatch_WhenJavaScriptToolIsMissing_ReturnsTrue(string message)
     {
         var lines = new[]
diff --git a/tests/Shared/Docker/Dockerfile.e2e b/tests/Shared/Docker/Dockerfile.e2e
index f63147d4d0d..88d2174b9eb 100644
--- a/tests/Shared/Docker/Dockerfile.e2e
+++ b/tests/Shared/Docker/Dockerfile.e2e
@@ -77,6 +77,8 @@ RUN curl -fsSL https://deb.nodesource.com/setup_22.x | bash - && \
     curl -fsSL https://bun.sh/install | bash && \
     ln -s /root/.bun/bin/bun /usr/local/bin/bun && \
     ln -s /root/.bun/bin/bunx /usr/local/bin/bunx && \
+    curl -fsSL https://deno.land/install.sh | sh -s v2.9.0 && \
+    ln -s /root/.deno/bin/deno /usr/local/bin/deno && \
     rm -rf /var/lib/apt/lists/*
 
 # Install Python and uv (needed for Python templates).
diff --git a/tests/Shared/Docker/Dockerfile.e2e-polyglot-base b/tests/Shared/Docker/Dockerfile.e2e-polyglot-base
index 0f149b668ce..c2464a333bd 100644
--- a/tests/Shared/Docker/Dockerfile.e2e-polyglot-base
+++ b/tests/Shared/Docker/Dockerfile.e2e-polyglot-base
@@ -1,7 +1,7 @@
 # Multi-stage Dockerfile for Aspire E2E testing (polyglot base variant).
 #
 # Includes: Docker CLI (via host socket mount), gh CLI,
-#           Node.js, Bun, Yarn, pnpm, Aspire install scripts.
+#           Node.js, Bun, Yarn, pnpm, Deno, Aspire install scripts.
 # Does NOT include .NET SDK or Java.
 #
 # Usage:
@@ -79,6 +79,8 @@ RUN curl -fsSL https://deb.nodesource.com/setup_22.x | bash - && \
     curl -fsSL https://bun.sh/install | bash && \
     ln -s /root/.bun/bin/bun /usr/local/bin/bun && \
     ln -s /root/.bun/bin/bunx /usr/local/bin/bunx && \
+    curl -fsSL https://deno.land/install.sh | sh -s v2.9.0 && \
+    ln -s /root/.deno/bin/deno /usr/local/bin/deno && \
     rm -rf /var/lib/apt/lists/*
 
 # --- Aspire CLI setup ---

From 13ca9492293d5222598a7b94ec2701aa8b661ded Mon Sep 17 00:00:00 2001
From: Adam Ratzman <adam@adamratzman.com>
Date: Mon, 6 Jul 2026 12:37:16 -0600
Subject: [PATCH 2/2] Fix Deno watch ready text in E2E helper

The E2E watch path runs deno task aspire:dev, which executes the scaffolded tsc --watch script. Wait for the TypeScript compiler watch banner instead of Deno's native watcher banner.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../TypeScriptAppHostToolchainTestHelpers.cs   | 16 ++++++++--------
 ...peScriptAppHostToolchainTestHelpersTests.cs | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)
 create mode 100644 tests/Aspire.Cli.EndToEnd.Tests/TypeScriptAppHostToolchainTestHelpersTests.cs

diff --git a/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs b/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
index 0aa57cbd2b7..1588543de36 100644
--- a/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
+++ b/tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs
@@ -98,15 +98,15 @@ internal static string GetRunScriptCommand(string toolchain, string scriptName)
 
     /// <summary>
     /// Gets the console text that indicates watch mode is active for a toolchain.
-    /// Node-based toolchains use nodemon; Deno uses its native file watcher, which prints
-    /// a different banner.
+    /// The E2E path runs the scaffolded <c>aspire:dev</c> package script for every toolchain,
+    /// so readiness comes from <c>tsc --watch</c>.
     /// </summary>
-    internal static string GetWatchModeReadyText(string toolchain) =>
-        NormalizeToolchain(toolchain) switch
-        {
-            "deno" => "Watcher Process started.",
-            _ => "Watching for file changes."
-        };
+    internal static string GetWatchModeReadyText(string toolchain)
+    {
+        _ = NormalizeToolchain(toolchain);
+
+        return "Watching for file changes.";
+    }
 
     /// <summary>
     /// Gets the primary lock file name a toolchain should produce after restore/install.
diff --git a/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptAppHostToolchainTestHelpersTests.cs b/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptAppHostToolchainTestHelpersTests.cs
new file mode 100644
index 00000000000..4a73c6f76cf
--- /dev/null
+++ b/tests/Aspire.Cli.EndToEnd.Tests/TypeScriptAppHostToolchainTestHelpersTests.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Aspire.Cli.EndToEnd.Tests.Helpers;
+using Xunit;
+
+namespace Aspire.Cli.EndToEnd.Tests;
+
+public sealed class TypeScriptAppHostToolchainTestHelpersTests
+{
+    [Fact]
+    public void GetWatchModeReadyText_WhenToolchainIsDeno_ReturnsTypeScriptCompilerWatchText()
+    {
+        var watchModeReadyText = TypeScriptAppHostToolchainTestHelpers.GetWatchModeReadyText("deno");
+
+        Assert.Equal("Watching for file changes.", watchModeReadyText);
+    }
+}