Initial scaffold: Elsa 3.5 custom API server with sample Shout activity

- src/Elsa.CustomServer: minimal ASP.NET Core 8 host referencing Elsa 3.5 NuGets
- Activities auto-registered via AddActivitiesFrom<Program>() — drop new files under Activities/
- Sqlite persistence for workflow definitions + runtime
- Multi-stage Dockerfile targeting linux/amd64, ASP.NET 8 runtime, port 8080
- Forwarded-headers configured so URLs come out https:// behind Traefik
- CORS wide-open so the standalone Studio (different origin) can talk to us

.dockerignore

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+**/bin
+**/obj
+**/App_Data
+**/*.db
+**/*.db-*
+.git
+.gitignore
+.vscode
+.idea
+deploy.json
+README.md

.gitignore

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+## .NET
+bin/
+obj/
+*.user
+*.suo
+.vs/
+
+## Rider / VS Code
+.idea/
+.vscode/
+
+## Runtime / build output
+publish/
+out/
+TestResults/
+
+## macOS / Linux
+.DS_Store
+
+## Elsa runtime state
+App_Data/
+*.db
+*.db-*
+*.sqlite
+*.sqlite-journal
+
+## Coolify config carries the app UUID and env values, keep it local
+deploy.json

Dockerfile

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+# Elsa Custom Server — Docker image
+# Multi-stage build so the final image only carries the ASP.NET runtime.
+
+FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+WORKDIR /source
+
+# Restore first for better layer caching.
+COPY src/Elsa.CustomServer/Elsa.CustomServer.csproj src/Elsa.CustomServer/
+RUN dotnet restore src/Elsa.CustomServer/Elsa.CustomServer.csproj
+
+# Then copy the rest and publish.
+COPY src/ src/
+RUN dotnet publish src/Elsa.CustomServer/Elsa.CustomServer.csproj \
+    -c Release -o /app/publish --no-restore /p:UseAppHost=false
+
+FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS runtime
+WORKDIR /app
+COPY --from=build /app/publish ./
+
+# Ensure the SQLite DB and any workflow blobs land on a writable path we can volume-mount.
+RUN mkdir -p /app/App_Data && chmod 777 /app/App_Data
+VOLUME ["/app/App_Data"]
+
+# Kestrel binds to whatever HTTP_PORTS says; keep the container port fixed so Coolify
+# can wire Traefik consistently.
+ENV ASPNETCORE_URLS=http://+:8080
+ENV HTTP_PORTS=8080
+
+EXPOSE 8080
+ENTRYPOINT ["dotnet", "Elsa.CustomServer.dll"]

README.md

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+# Elsa Custom Server
+
+Custom Elsa Workflows API server. Extends stock Elsa 3.x with our own activities.
+
+## Where activities live
+
+`src/Elsa.CustomServer/Activities/*.cs` — anything marked `[Activity(...)]` under this
+folder is auto-registered via `AddActivitiesFrom<Program>()` in `Program.cs`.
+
+To add a new node type in the Studio designer:
+
+1. Drop a new file under `Activities/`.
+2. Inherit from `CodeActivity`, `CodeActivity<T>`, or `Activity` for triggerable ones.
+3. Rebuild and redeploy — Studio picks it up automatically the next time it fetches
+   the activity descriptors.
+
+Example — see `Activities/Shout.cs`.
+
+## Local run
+
+```sh
+dotnet run --project src/Elsa.CustomServer
+```
+
+Listens on http://localhost:8080; API root is `/elsa/api`.
+
+## Docker
+
+```sh
+docker build -t elsa-custom-server .
+docker run --rm -p 8080:8080 \
+  -e Identity__Tokens__SigningKey="$(openssl rand -base64 64)" \
+  elsa-custom-server
+```
+
+## Deployment
+
+Coolify builds this image from the Dockerfile at repo root when the app is created
+with `build_pack: "dockerfile"`. The Studio (separate container running the stock
+`elsaworkflows/elsa-studio-v3` image) needs its `BACKEND__URL` env var pointed at
+this server's `/elsa/api`.

src/Elsa.CustomServer/Activities/Shout.cs

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+using Elsa.Extensions;
+using Elsa.Workflows;
+using Elsa.Workflows.Attributes;
+using Elsa.Workflows.Models;
+
+namespace Elsa.CustomServer.Activities;
+
+/// Sample custom activity — appears in the Studio toolbox under the "Custom" category.
+[Activity("Custom", "Shout", "Uppercases a string and returns it.", Kind = ActivityKind.Task)]
+public class Shout : CodeActivity<string>
+{
+    [Input(Description = "The text to shout.")]
+    public Input<string> Text { get; set; } = default!;
+
+    protected override void Execute(ActivityExecutionContext context)
+    {
+        var input = context.Get(Text) ?? string.Empty;
+        var result = input.ToUpperInvariant() + "!";
+        context.SetResult(result);
+    }
+}

src/Elsa.CustomServer/Elsa.CustomServer.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>Elsa.CustomServer</RootNamespace>
+    <AssemblyName>Elsa.CustomServer</AssemblyName>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Elsa 3.x meta packages. Kept on the latest 3.x line so the Studio (elsa-studio-v3) can talk to us. -->
+    <PackageReference Include="Elsa" Version="3.5.0" />
+    <PackageReference Include="Elsa.Http" Version="3.5.0" />
+    <PackageReference Include="Elsa.Identity" Version="3.5.0" />
+    <PackageReference Include="Elsa.Scheduling" Version="3.5.0" />
+    <PackageReference Include="Elsa.Workflows.Api" Version="3.5.0" />
+    <PackageReference Include="Elsa.EntityFrameworkCore" Version="3.5.0" />
+    <PackageReference Include="Elsa.EntityFrameworkCore.Sqlite" Version="3.5.0" />
+    <PackageReference Include="Elsa.CSharp" Version="3.5.0" />
+    <PackageReference Include="Elsa.JavaScript" Version="3.5.0" />
+    <PackageReference Include="Elsa.Liquid" Version="3.5.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Folder Include="App_Data\" />
+  </ItemGroup>
+
+</Project>

src/Elsa.CustomServer/Program.cs

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+using System.Text.Encodings.Web;
+using Elsa.EntityFrameworkCore.Extensions;
+using Elsa.EntityFrameworkCore.Modules.Management;
+using Elsa.EntityFrameworkCore.Modules.Runtime;
+using Elsa.Extensions;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.HttpOverrides;
+
+var builder = WebApplication.CreateBuilder(args);
+var configuration = builder.Configuration;
+var identitySection = configuration.GetSection("Identity");
+var identityTokenSection = identitySection.GetSection("Tokens");
+
+builder.Services.AddElsa(elsa =>
+{
+    elsa
+        // Discovers everything in this assembly decorated with [Activity] — including anything you drop under Activities/.
+        .AddActivitiesFrom<Program>()
+        .UseIdentity(identity =>
+        {
+            identity.TokenOptions = options => identityTokenSection.Bind(options);
+            identity.UseConfigurationBasedUserProvider(options => identitySection.Bind(options));
+            identity.UseConfigurationBasedApplicationProvider(options => identitySection.Bind(options));
+            identity.UseConfigurationBasedRoleProvider(options => identitySection.Bind(options));
+        })
+        .UseDefaultAuthentication()
+        .UseWorkflowManagement(m => m.UseEntityFrameworkCore(ef => ef.UseSqlite()))
+        .UseWorkflowRuntime(r => r.UseEntityFrameworkCore(ef => ef.UseSqlite()))
+        .UseScheduling()
+        .UseWorkflowsApi()
+        .UseHttp(http => http.ConfigureHttpOptions = options => configuration.GetSection("Http").Bind(options))
+        .UseCSharp()
+        .UseJavaScript()
+        .UseLiquid(liquid => liquid.FluidOptions = options => options.Encoder = HtmlEncoder.Default);
+});
+
+// Studio (whichever host) is on a different origin, so allow it in.
+builder.Services.AddCors(cors => cors.AddDefaultPolicy(p => p
+    .AllowAnyHeader()
+    .AllowAnyMethod()
+    .AllowAnyOrigin()
+    .WithExposedHeaders("x-elsa-workflow-instance-id")));
+
+builder.Services.AddHealthChecks();
+
+// Traefik terminates TLS in front of us; without this, self-generated URLs come out as http://
+builder.Services.Configure<ForwardedHeadersOptions>(o =>
+{
+    o.ForwardedHeaders = ForwardedHeaders.All;
+    o.KnownNetworks.Clear();
+    o.KnownProxies.Clear();
+});
+
+var app = builder.Build();
+
+app.UseForwardedHeaders();
+app.UseCors();
+app.UseRouting();
+app.UseAuthentication();
+app.UseAuthorization();
+app.UseWorkflowsApi();
+app.UseWorkflows();
+app.UseJsonSerializationErrorHandler();
+app.MapHealthChecks("/health");
+app.MapGet("/", () => Results.Ok(new { name = "Elsa Custom Server", status = "ok" }));
+
+app.Run();

src/Elsa.CustomServer/appsettings.Development.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Debug",
+      "Microsoft.AspNetCore": "Information"
+    }
+  }
+}

src/Elsa.CustomServer/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning",
+      "Microsoft.EntityFrameworkCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+  "ConnectionStrings": {
+    "Sqlite": "Data Source=App_Data/elsa.sqlite.db;Cache=Shared;"
+  },
+  "Http": {
+    "BaseUrl": "https://elsa-api.tes.gd",
+    "BasePath": "/workflows"
+  },
+  "Identity": {
+    "Tokens": {
+      "SigningKey": "CHANGE_ME_VIA_ENV_Identity__Tokens__SigningKey",
+      "AccessTokenLifetime": "1:00:00",
+      "RefreshTokenLifetime": "1.00:00:00"
+    },
+    "Roles": [
+      {
+        "Id": "admin",
+        "Name": "Administrator",
+        "Permissions": [ "*" ]
+      }
+    ],
+    "Users": [
+      {
+        "Id": "admin",
+        "Name": "admin",
+        "Email": "admin@elsa.local",
+        "HashedPassword": "",
+        "HashedPasswordSalt": "",
+        "Roles": [ "admin" ]
+      }
+    ],
+    "Applications": []
+  }
+}