microsoft · rogerbarreto · May 7, 2026 · May 7, 2026
diff --git a/docs/decisions/0026-hosted-session-identity-context.md b/docs/decisions/0026-hosted-session-identity-context.md
@@ -0,0 +1,82 @@
+---
+status: accepted
+contact: rogerbarreto
+date: 2026-05-07
+deciders: rogerbarreto
+consulted: []
+informed: []
+---
+
+# Hosted session identity context for Foundry Hosting
+
+## Context and Problem Statement
+
+Server-hosted Foundry agents need a way to scope per-user state (most notably `FoundryMemoryProvider` memories) by the end user that initiated the request. The Foundry platform already injects `x-agent-user-isolation-key` and `x-agent-chat-isolation-key` headers on every Responses request, but the agent-framework hosting layer did not surface those values to `AIContextProvider` instances. The provider's `stateInitializer` only received an `AgentSession?` with no identity attached, so per-user scoping was impossible without out-of-band plumbing.
+
+## Decision Drivers
+
+- Memory and any future user-private context must be partitioned per end user without per-sample boilerplate.
+- The identity must be **read-only** from the perspective of `AIContextProvider`s, so a buggy or hostile provider cannot escalate or leak across users.
+- The persisted session must validate against the live request on every resume to defend against session-id leak and in-process tampering.
+- The change must work for every existing hosted-agent type (`ChatClientAgent`, `FoundryAgent`, future ones) without per-type refactoring of cast-heavy code paths in `Microsoft.Agents.AI`.
+- Local Docker debugging must remain possible when the platform headers are absent.
+
+## Considered Options
+
+1. **`HostedSessionContext` stored in `AgentSessionStateBag`, exposed via a public read accessor and an `internal` setter.** Hosting writes once on session creation and validates on every resume.
+2. **Specialised `HostedAgentSession : AgentSession` wrapper** that carries `UserId`/`ChatId` properties, with `GetService<ChatClientAgentSession>()` as the unwrap escape hatch.
+3. **New property on `AgentSession` base class** (`HostedSessionContext? HostedContext { get; internal set; }`).
+4. **AsyncLocal middleware** that reads the headers and stuffs them into a per-request `AsyncLocal<HostedSessionContext>` consumed by the provider.
+
+For the source of identity:
+- A. The platform-injected `IsolationContext` exposed by `ResponseContext.Isolation` (typed `UserIsolationKey`/`ChatIsolationKey`).
+- B. The OpenAI Responses spec's top-level `request.User` field.
+- C. A custom HTTP header `x-client-user`.
+
+## Decision Outcome
+
+**Option 1** was chosen for the storage shape, sourced from **Option A** (`ResponseContext.Isolation`).
+
+Rationale:
+
+- **Wrapper rejected (Option 2).** `ChatClientAgentSession` is `sealed` and `ChatClientAgent` rejects any other session type via direct `is not ChatClientAgentSession` checks at multiple call sites. Wrapping would force non-trivial refactors across `Microsoft.Agents.AI` and a corresponding repeat for every other agent type.
+- **Base-class property rejected (Option 3).** Leaks "hosted" semantics into the universal `AgentSession` abstraction used by Durable, A2A, and CopilotStudio agents that have no notion of a hosted user.
+- **AsyncLocal rejected (Option 4).** Surfaces the concept only locally, requires every consumer to re-implement the bridge, and cannot be enforced as read-only.
+- **`request.User` rejected (Option B).** Set by the caller, not the platform. Forging it client-side trivially defeats per-user partitioning.
+- **`x-client-user` rejected (Option C).** Non-standard, requires custom HTTP plumbing, and duplicates the platform-provided isolation contract.
+
+Implementation summary in `Microsoft.Agents.AI.Foundry.Hosting`:
+
+| Type | Visibility | Purpose |
+|---|---|---|
+| `HostedSessionContext` | public sealed | Captures `UserId` and `ChatId` (both required, non-whitespace). |
+| `HostedSessionContextExtensions.GetHostedContext` | public | Read accessor for `AIContextProvider`s. |
+| `HostedSessionContextExtensions.SetHostedContext` | internal | Writer reserved for the hosting assembly. Backed by `AgentSessionStateBag` under a well-known key for serialisation. |
+| `HostedSessionIsolationKeyProvider` (abstract) | public | DI-resolvable factory. Async signature: `ValueTask<HostedSessionContext?> GetKeysAsync(ResponseContext, CreateResponse, CancellationToken)`. |
+| `PlatformHostedSessionIsolationKeyProvider` | internal sealed | Default implementation. Maps `context.Isolation.UserIsolationKey` and `context.Isolation.ChatIsolationKey`. Returns `null` when either is absent. |
+
+Behaviour added to `AgentFrameworkResponseHandler.CreateAsync`:
+
+1. Resolve `HostedSessionIsolationKeyProvider` from DI; fall back to `PlatformHostedSessionIsolationKeyProvider`.
+2. Call `GetKeysAsync(context, request, cancellationToken)`. A `null` result throws `InvalidOperationException` (becomes 500). A null/whitespace `UserId` or `ChatId` is rejected by `HostedSessionContext`'s constructor.
+3. Fresh sessions (no incoming `previous_response_id`/conversation id) are tagged via `SetHostedContext`.
+4. Resumed sessions must already carry a `HostedSessionContext` whose `UserId` and `ChatId` match the resolved values exactly. Mismatch (including missing-on-resume and any field difference) throws `ResponsesApiException` with status 403 and body `Hosted session identity context mismatch`.
+
+## Consequences
+
+Positive:
+
+- Per-user memory partitioning works out of the box for any agent that consumes a `Microsoft.Agents.AI.Foundry.FoundryMemoryProvider` configured to read `session.GetHostedContext().UserId`.
+- Cross-user session-id leak and in-process tampering of the persisted identity both surface as a 403 with a deliberately uninformative body.
+- The identity is opaque to the framework, matching the platform's semantics. The framework never inspects user identity; the `IsolationContext` keys are pre-partitioned per agent.
+
+Negative:
+
+- Every existing hosted sample fails locally without a `HostedSessionIsolationKeyProvider` registered, because the platform headers are absent outside the platform. Mitigated by shipping `Hosted_Shared_Contributor_Setup` with `DevTemporaryLocalSessionIsolationKeyProvider` and `AddDevTemporaryLocalContributorSetup`, and migrating all 9 existing responses samples.
+- Sessions persisted before this change cannot be resumed (they lack a `HostedSessionContext` and 403 on first resume). This is a deliberate trade-off to enforce the strict contract uniformly.
+
+## Out of scope
+
+- Per-request `User` field on `CreateResponse` is intentionally not consumed; only the platform `IsolationContext` headers carry trustworthy identity.
+- Generic (non-Foundry) hosting layers can re-define an equivalent type if needed; nothing in this ADR is moved into `Microsoft.Agents.AI.Hosting` because `Microsoft.Agents.AI.Foundry.Hosting` does not depend on it.
+- HMAC tamper signatures over the persisted context are not implemented; comparison against `ResponseContext.Isolation` on every request is sufficient because the platform sets those headers at the trust boundary.
diff --git a/dotnet/agent-framework-dotnet.slnx b/dotnet/agent-framework-dotnet.slnx
@@ -319,9 +319,15 @@
   <Folder Name="/Samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/">
     <Project Path="samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/HostedMcpTools.csproj" />
   </Folder>
+  <Folder Name="/Samples/04-hosting/FoundryHostedAgents/responses/Hosted-MemoryAgent/">
+    <Project Path="samples/04-hosting/FoundryHostedAgents/responses/Hosted-MemoryAgent/HostedMemoryAgent.csproj" />
+  </Folder>
   <Folder Name="/Samples/04-hosting/FoundryHostedAgents/responses/Hosted-Observability/">
     <Project Path="samples/04-hosting/FoundryHostedAgents/responses/Hosted-Observability/HostedObservability.csproj" />
   </Folder>
+  <Folder Name="/Samples/04-hosting/FoundryHostedAgents/responses/Hosted_Shared_Contributor_Setup/">
+    <Project Path="samples/04-hosting/FoundryHostedAgents/responses/Hosted_Shared_Contributor_Setup/Hosted_Shared_Contributor_Setup.csproj" />
+  </Folder>
   <Folder Name="/Samples/04-hosting/FoundryHostedAgents/responses/Hosted-Toolbox/">
     <Project Path="samples/04-hosting/FoundryHostedAgents/responses/Hosted-Toolbox/HostedToolbox.csproj" />
   </Folder>

diff --git a/...hosting/FoundryHostedAgents/responses/Hosted-ChatClientAgent/HostedChatClientAgent.csproj b/...hosting/FoundryHostedAgents/responses/Hosted-ChatClientAgent/HostedChatClientAgent.csproj
@@ -18,6 +18,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry.Hosting\Microsoft.Agents.AI.Foundry.Hosting.csproj" />
+    <ProjectReference Include="..\Hosted_Shared_Contributor_Setup\Hosted_Shared_Contributor_Setup.csproj" />
   </ItemGroup>
 
   <!-- For end-users: uncomment the PackageReference below and remove the ProjectReference above

diff --git a/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-ChatClientAgent/Program.cs b/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-ChatClientAgent/Program.cs
@@ -4,6 +4,7 @@
 using Azure.Core;
 using Azure.Identity;
 using DotNetEnv;
+using Hosted_Shared_Contributor_Setup;
 using Microsoft.Agents.AI;
 using Microsoft.Agents.AI.Foundry.Hosting;
 
@@ -40,6 +41,7 @@ You are a helpful AI assistant hosted as a Foundry Hosted Agent.
 // Host the agent as a Foundry Hosted Agent using the Responses API.
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddFoundryResponses(agent);
+builder.Services.AddDevTemporaryLocalContributorSetup(); // Local Docker debugging only - must not be used in production.
 
 var app = builder.Build();
 app.MapFoundryResponses();
@@ -51,48 +53,3 @@ You are a helpful AI assistant hosted as a Foundry Hosted Agent.
 }
 
 app.Run();
-
-/// <summary>
-/// A <see cref="TokenCredential"/> for local Docker debugging only.
-///
-/// When debugging and testing a hosted agent in a local Docker container, Azure CLI
-/// and other interactive credentials are not available. This credential reads a
-/// pre-fetched bearer token from the <c>AZURE_BEARER_TOKEN</c> environment variable.
-///
-/// This should NOT be used in production — tokens expire (~1 hour) and cannot be refreshed.
-/// In production, the Foundry platform injects a managed identity automatically.
-///
-/// Generate a token on your host and pass it to the container:
-///   export AZURE_BEARER_TOKEN=$(az account get-access-token --resource https://ai.azure.com --query accessToken -o tsv)
-///   docker run -e AZURE_BEARER_TOKEN=$AZURE_BEARER_TOKEN ...
-/// </summary>
-internal sealed class DevTemporaryTokenCredential : TokenCredential
-{
-    private const string EnvironmentVariable = "AZURE_BEARER_TOKEN";
-    private readonly string? _token;
-
-    public DevTemporaryTokenCredential()
-    {
-        this._token = Environment.GetEnvironmentVariable(EnvironmentVariable);
-    }
-
-    public override AccessToken GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken)
-    {
-        return this.GetAccessToken();
-    }
-
-    public override ValueTask<AccessToken> GetTokenAsync(TokenRequestContext requestContext, CancellationToken cancellationToken)
-    {
-        return new ValueTask<AccessToken>(this.GetAccessToken());
-    }
-
-    private AccessToken GetAccessToken()
-    {
-        if (string.IsNullOrEmpty(this._token) || this._token == "DefaultAzureCredential")
-        {
-            throw new CredentialUnavailableException($"{EnvironmentVariable} environment variable is not set.");
-        }
-
-        return new AccessToken(this._token, DateTimeOffset.UtcNow.AddHours(1));
-    }
-}
diff --git a/...es/04-hosting/FoundryHostedAgents/responses/Hosted-FoundryAgent/HostedFoundryAgent.csproj b/...es/04-hosting/FoundryHostedAgents/responses/Hosted-FoundryAgent/HostedFoundryAgent.csproj
@@ -18,6 +18,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry.Hosting\Microsoft.Agents.AI.Foundry.Hosting.csproj" />
+    <ProjectReference Include="..\Hosted_Shared_Contributor_Setup\Hosted_Shared_Contributor_Setup.csproj" />
   </ItemGroup>
 
   <!-- For end-users: uncomment the PackageReference below and remove the ProjectReference above

diff --git a/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-FoundryAgent/Program.cs b/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-FoundryAgent/Program.cs
@@ -5,6 +5,7 @@
 using Azure.Core;
 using Azure.Identity;
 using DotNetEnv;
+using Hosted_Shared_Contributor_Setup;
 using Microsoft.Agents.AI.Foundry;
 using Microsoft.Agents.AI.Foundry.Hosting;
 
@@ -33,6 +34,7 @@
 // Host the agent as a Foundry Hosted Agent using the Responses API.
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddFoundryResponses(agent);
+builder.Services.AddDevTemporaryLocalContributorSetup(); // Local Docker debugging only - must not be used in production.
 
 var app = builder.Build();
 app.MapFoundryResponses();
@@ -44,48 +46,3 @@
 }
 
 app.Run();
-
-/// <summary>
-/// A <see cref="TokenCredential"/> for local Docker debugging only.
-///
-/// When debugging and testing a hosted agent in a local Docker container, Azure CLI
-/// and other interactive credentials are not available. This credential reads a
-/// pre-fetched bearer token from the <c>AZURE_BEARER_TOKEN</c> environment variable.
-///
-/// This should NOT be used in production — tokens expire (~1 hour) and cannot be refreshed.
-/// In production, the Foundry platform injects a managed identity automatically.
-///
-/// Generate a token on your host and pass it to the container:
-///   export AZURE_BEARER_TOKEN=$(az account get-access-token --resource https://ai.azure.com --query accessToken -o tsv)
-///   docker run -e AZURE_BEARER_TOKEN=$AZURE_BEARER_TOKEN ...
-/// </summary>
-internal sealed class DevTemporaryTokenCredential : TokenCredential
-{
-    private const string EnvironmentVariable = "AZURE_BEARER_TOKEN";
-    private readonly string? _token;
-
-    public DevTemporaryTokenCredential()
-    {
-        this._token = Environment.GetEnvironmentVariable(EnvironmentVariable);
-    }
-
-    public override AccessToken GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken)
-    {
-        return this.GetAccessToken();
-    }
-
-    public override ValueTask<AccessToken> GetTokenAsync(TokenRequestContext requestContext, CancellationToken cancellationToken)
-    {
-        return new ValueTask<AccessToken>(this.GetAccessToken());
-    }
-
-    private AccessToken GetAccessToken()
-    {
-        if (string.IsNullOrEmpty(this._token) || this._token == "DefaultAzureCredential")
-        {
-            throw new CredentialUnavailableException($"{EnvironmentVariable} environment variable is not set.");
-        }
-
-        return new AccessToken(this._token, DateTimeOffset.UtcNow.AddHours(1));
-    }
-}
diff --git a/...amples/04-hosting/FoundryHostedAgents/responses/Hosted-LocalTools/HostedLocalTools.csproj b/...amples/04-hosting/FoundryHostedAgents/responses/Hosted-LocalTools/HostedLocalTools.csproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFrameworks>net10.0</TargetFrameworks>
@@ -20,6 +20,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry.Hosting\Microsoft.Agents.AI.Foundry.Hosting.csproj" />
+    <ProjectReference Include="..\Hosted_Shared_Contributor_Setup\Hosted_Shared_Contributor_Setup.csproj" />
   </ItemGroup>
 
   <!-- For end-users: uncomment the PackageReference below and remove the ProjectReference above

diff --git a/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-LocalTools/Program.cs b/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-LocalTools/Program.cs
@@ -11,6 +11,7 @@
 using Azure.Core;
 using Azure.Identity;
 using DotNetEnv;
+using Hosted_Shared_Contributor_Setup;
 using Microsoft.Agents.AI;
 using Microsoft.Agents.AI.Foundry.Hosting;
 using Microsoft.Extensions.AI;
@@ -112,6 +113,7 @@ politely let them know you specialize in Seattle hotel recommendations.
 
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddFoundryResponses(agent);
+builder.Services.AddDevTemporaryLocalContributorSetup(); // Local Docker debugging only - must not be used in production.
 
 var app = builder.Build();
 app.MapFoundryResponses();
@@ -126,39 +128,3 @@ politely let them know you specialize in Seattle hotel recommendations.
 // ── Types ────────────────────────────────────────────────────────────────────
 
 internal sealed record Hotel(string Name, int PricePerNight, double Rating, string Location);
-
-/// <summary>
-/// A <see cref="TokenCredential"/> for local Docker debugging only.
-/// Reads a pre-fetched bearer token from the <c>AZURE_BEARER_TOKEN</c> environment variable
-/// once at startup. This should NOT be used in production.
-///
-/// Generate a token on your host and pass it to the container:
-///   export AZURE_BEARER_TOKEN=$(az account get-access-token --resource https://ai.azure.com --query accessToken -o tsv)
-///   docker run -e AZURE_BEARER_TOKEN=$AZURE_BEARER_TOKEN ...
-/// </summary>
-internal sealed class DevTemporaryTokenCredential : TokenCredential
-{
-    private const string EnvironmentVariable = "AZURE_BEARER_TOKEN";
-    private readonly string? _token;
-
-    public DevTemporaryTokenCredential()
-    {
-        this._token = Environment.GetEnvironmentVariable(EnvironmentVariable);
-    }
-
-    public override AccessToken GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken)
-        => this.GetAccessToken();
-
-    public override ValueTask<AccessToken> GetTokenAsync(TokenRequestContext requestContext, CancellationToken cancellationToken)
-        => new(this.GetAccessToken());
-
-    private AccessToken GetAccessToken()
-    {
-        if (string.IsNullOrEmpty(this._token) || this._token == "DefaultAzureCredential")
-        {
-            throw new CredentialUnavailableException($"{EnvironmentVariable} environment variable is not set.");
-        }
-
-        return new AccessToken(this._token, DateTimeOffset.UtcNow.AddHours(1));
-    }
-}
diff --git a/...et/samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/HostedMcpTools.csproj b/...et/samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/HostedMcpTools.csproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFrameworks>net10.0</TargetFrameworks>
@@ -21,6 +21,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
     <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Foundry.Hosting\Microsoft.Agents.AI.Foundry.Hosting.csproj" />
+    <ProjectReference Include="..\Hosted_Shared_Contributor_Setup\Hosted_Shared_Contributor_Setup.csproj" />
   </ItemGroup>
 
   <!-- For end-users: uncomment the PackageReference below and remove the ProjectReference above

diff --git a/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/Program.cs b/dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted-McpTools/Program.cs
@@ -19,6 +19,7 @@
 using Azure.Core;
 using Azure.Identity;
 using DotNetEnv;
+using Hosted_Shared_Contributor_Setup;
 using Microsoft.Agents.AI;
 using Microsoft.Agents.AI.Foundry.Hosting;
 using Microsoft.Extensions.AI;
@@ -81,6 +82,7 @@ Be concise and provide direct answers with relevant links.
 // Host the agent as a Foundry Hosted Agent using the Responses API.
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddFoundryResponses(agent);
+builder.Services.AddDevTemporaryLocalContributorSetup(); // Local Docker debugging only - must not be used in production.
 
 var app = builder.Build();
 app.MapFoundryResponses();
@@ -92,39 +94,3 @@ Be concise and provide direct answers with relevant links.
 }
 
 app.Run();
-
-/// <summary>
-/// A <see cref="TokenCredential"/> for local Docker debugging only.
-/// Reads a pre-fetched bearer token from the <c>AZURE_BEARER_TOKEN</c> environment variable
-/// once at startup. This should NOT be used in production.
-///
-/// Generate a token on your host and pass it to the container:
-///   export AZURE_BEARER_TOKEN=$(az account get-access-token --resource https://ai.azure.com --query accessToken -o tsv)
-///   docker run -e AZURE_BEARER_TOKEN=$AZURE_BEARER_TOKEN ...
-/// </summary>
-internal sealed class DevTemporaryTokenCredential : TokenCredential
-{
-    private const string EnvironmentVariable = "AZURE_BEARER_TOKEN";
-    private readonly string? _token;
-
-    public DevTemporaryTokenCredential()
-    {
-        this._token = Environment.GetEnvironmentVariable(EnvironmentVariable);
-    }
-
-    public override AccessToken GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken)
-        => this.GetAccessToken();
-
-    public override ValueTask<AccessToken> GetTokenAsync(TokenRequestContext requestContext, CancellationToken cancellationToken)
-        => new(this.GetAccessToken());
-
-    private AccessToken GetAccessToken()
-    {
-        if (string.IsNullOrEmpty(this._token) || this._token == "DefaultAzureCredential")
-        {
-            throw new CredentialUnavailableException($"{EnvironmentVariable} environment variable is not set.");
-        }
-
-        return new AccessToken(this._token, DateTimeOffset.UtcNow.AddHours(1));
-    }
-}