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Set FUNCTIONS_WORKER_RUNTIME to custom if EnableMcpCustomHandlerPreview is set #4703

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Merged
soninaren merged 1 commit into from
Nov 6, 2025
Merged

Set FUNCTIONS_WORKER_RUNTIME to custom if EnableMcpCustomHandlerPreview is set #4703

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6 changes: 6 additions & 0 deletions src/Cli/func/Actions/HostActions/StartHostAction.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
using Microsoft.AspNetCore.Hosting;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Script;
using Microsoft.Azure.WebJobs.Script.Config;
using Microsoft.Azure.WebJobs.Script.Configuration;
using Microsoft.Azure.WebJobs.Script.Description;
using Microsoft.Azure.WebJobs.Script.WebHost;
Expand Down Expand Up @@ -367,6 +368,11 @@ private void UpdateEnvironmentVariables(IDictionary<string, string> secrets)
Environment.SetEnvironmentVariable($"AzureFunctionsJobHost__functions__{i}", EnabledFunctions[i]);
}
}

if (FeatureFlags.IsEnabled(Constants.EnableMcpCustomHandlerFeatureFlag, SystemEnvironment.Instance))
{
Environment.SetEnvironmentVariable(Constants.FunctionsWorkerRuntime, Constants.Languages.Custom);
}
}

/// <summary>
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1 change: 1 addition & 0 deletions src/Cli/func/Common/Constants.cs
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Expand Up @@ -95,6 +95,7 @@ internal static partial class Constants
public const string Dotnet = "dotnet";
public const string InProcDotNet8EnabledSetting = "FUNCTIONS_INPROC_NET8_ENABLED";
public const string AzureDevSessionsRemoteHostName = "AzureDevSessionsRemoteHostName";
public const string EnableMcpCustomHandlerFeatureFlag = "EnableMcpCustomHandlerPreview";

// forwardedHttpUrl sample format: https://n12abc3t-<port>.asse.devtunnels.ms/
public const string AzureDevSessionsPortSuffixPlaceholder = "<port>";
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10 changes: 4 additions & 6 deletions src/Cli/func/ConfigurationProfiles/McpCustomHandlerConfigurationProfile.cs
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Expand Up @@ -12,8 +12,6 @@ internal class McpCustomHandlerConfigurationProfile : IConfigurationProfile
{
// This feature flag enables MCP (Model Context Protocol) support for custom handlers
// This flag is not required locally, but is required when deploying to Azure environments.
private const string McpFeatureFlag = "EnableMcpCustomHandlerPreview";

public string Name { get; } = "mcp-custom-handler";

public async Task ApplyAsync(WorkerRuntime workerRuntime, bool force = false)
Expand Down Expand Up @@ -102,19 +100,19 @@ internal async Task ApplyLocalSettingsAsync(WorkerRuntime workerRuntime, bool fo
.Where(f => !string.IsNullOrWhiteSpace(f))
.ToList();

if (!flags.Contains(McpFeatureFlag, StringComparer.OrdinalIgnoreCase))
if (!flags.Contains(Constants.EnableMcpCustomHandlerFeatureFlag, StringComparer.OrdinalIgnoreCase))
{
flags.Add(McpFeatureFlag);
flags.Add(Constants.EnableMcpCustomHandlerFeatureFlag);
values[Constants.AzureWebJobsFeatureFlags] = string.Join(",", flags);
updatedFeatureFlag = true;

if (!hasFlagsKey)
{
SetupProgressLogger.Ok(Constants.LocalSettingsJsonFileName, $"Added feature flag '{McpFeatureFlag}'");
SetupProgressLogger.Ok(Constants.LocalSettingsJsonFileName, $"Added feature flag '{Constants.EnableMcpCustomHandlerFeatureFlag}'");
}
else
{
SetupProgressLogger.Ok(Constants.LocalSettingsJsonFileName, $"Appended feature flag '{McpFeatureFlag}'");
SetupProgressLogger.Ok(Constants.LocalSettingsJsonFileName, $"Appended feature flag '{Constants.EnableMcpCustomHandlerFeatureFlag}'");
}
}

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