@@ -8,10 +8,10 @@
 
 Public surface in this preview:
 
-- `SquadAgent` — sealed `AIAgent` wrapper over the Copilot-backed inner agent.
-- `SquadAgentOptions` — team root, CLI path/args, environment, token, logging, and instruction settings.
+- `SquadAgent` — sealed `AIAgent` wrapper over the Copilot-backed inner agent. Supports both non-streaming and streaming via `RunStreamingAsync`.
+- `SquadAgentOptions` — team root, CLI path/args, environment, token, logging, instruction settings, and a `ConfigureCopilotClient` delegate for advanced SDK customization.
 - `SquadConnectionFactory` — parses PATH or `squad://` connection strings into options.
-- `SquadServiceCollectionExtensions` — registers `SquadAgent` and base `AIAgent` in DI.
+- `SquadServiceCollectionExtensions` — registers `SquadAgent` and base `AIAgent` in DI, with standard and keyed overloads.
 
 Repository: <https://github.com/bradygaster/squad>
 
@@ -56,13 +56,77 @@ var response = await squad.RunAsync("What can this Squad team do?", session);
 Console.WriteLine(response.Text);
 ```
 
+## Streaming
+
+`SquadAgent` supports streaming via the MAF `RunStreamingAsync` method. The inner Copilot-backed agent streams response updates as they arrive from the CLI process:
+
+```csharp
+var squad = host.Services.GetRequiredService<SquadAgent>();
+var session = await squad.CreateSessionAsync();
+
+await foreach (var update in squad.RunStreamingAsync("Summarize the team.", session))
+{
+    Console.Write(update.Text);
+}
+```
+
+## Keyed DI
+
+Register multiple Squad teams in the same DI container using .NET 8+ keyed services:
+
+```csharp
+builder.Services.AddKeyedSquadAgent("research", o =>
+{
+    o.SquadFolderPath = @"C:\research-team";
+});
+
+builder.Services.AddKeyedSquadAgent("platform", o =>
+{
+    o.SquadFolderPath = @"C:\platform-team";
+});
+
+// Resolve in a minimal API endpoint:
+app.MapGet("/ask-research", async ([FromKeyedServices("research")] SquadAgent agent) =>
+{
+    var session = await agent.CreateSessionAsync();
+    var response = await agent.RunAsync("What's the latest?", session);
+    return response.Text;
+});
+```
+
+Keyed registrations include `AddKeyedSquadAgent` overloads for service key, optional connection-string name, and lifetime. Keyed and non-keyed registrations can coexist.
+
+## Advanced: ConfigureCopilotClient (BYOK)
+
+Use `ConfigureCopilotClient` to customize the underlying `CopilotClientOptions` after Squad applies its standard values. This is the extension point for injecting custom environment variables, providing a BYOK token, or tuning SDK settings:
+
+```csharp
+builder.Services.AddSquadAgent(o =>
+{
+    o.SquadFolderPath = @"C:\team";
+    o.ConfigureCopilotClient = clientOpts =>
+    {
+        // Inject a BYOK token from your own credential store
+        clientOpts.GitHubToken = myVault.GetSecret("copilot-token");
+
+        // Add custom environment variables for the CLI process
+        clientOpts.Environment = new Dictionary<string, string>
+        {
+            ["MY_CUSTOM_VAR"] = "value"
+        };
+    };
+});
+```
+
+> **Routing guard:** Squad enforces a hard routing gate — if the delegate changes `Cwd`, `CliPath`, or `CliArgs`, the original values are restored and a warning is logged. Configure these via `SquadAgentOptions` instead.
+
 ## GitHub Copilot authentication
 
 The default path mirrors the base GitHub Copilot SDK examples: leave `GitHubToken` and `GitHubTokenProvider` unset, then run with a locally signed-in GitHub Copilot user. For local development, sign in before running the app, for example with `gh auth login`, the Copilot CLI sign-in flow, or a Copilot-supported local sign-in that the SDK runtime can access.
 
 The SDK documents the credential priority order in [Authenticate Copilot SDK](https://github.com/github/copilot-sdk/blob/main/docs/auth/authenticate.md) and the broader [authentication overview](https://github.com/github/copilot-sdk/blob/main/docs/auth/index.md). Explicit tokens and environment variables are supported by the SDK, but they are not required for the minimal happy path.
 
-Use `GitHubTokenProvider` only when the host owns token retrieval, such as Key Vault, managed identity, or CI secret flow scenarios. Use `GitHubToken` only when you already have a Copilot-supported token in process and cannot use a provider callback. In both cases, treat these as advanced escape hatches and never hardcode tokens.
+Use `GitHubTokenProvider` only when the host owns token retrieval, such as Key Vault, managed identity, or CI secret flow scenarios. Use `GitHubToken` only when you already have a Copilot-supported token in process and cannot use a provider callback. Use `ConfigureCopilotClient` when you need full control over the SDK's `CopilotClientOptions`, including BYOK token injection.
 
 ## Aspire / configuration path
 
@@ -86,17 +150,26 @@ Parsed URI query keys: `teamRoot`, `cliPath`, `cwd`, `cliArgs` (semicolon-separa
 | `SquadFolderPath` | Squad team root; PATH connection strings set this and `Cwd`. |
 | `CliPath` / `CliArgs` | Override the Copilot CLI executable and add extra CLI flags. |
 | `Cwd` | Working directory for the Copilot CLI process; defaults to `SquadFolderPath`. |
-| `Environment` | Additional environment variables for the CLI process. Avoid user-controlled values. |
-| `GitHubToken` | Advanced direct token escape hatch; redacted by `ToString()`. |
+| `Environment` | Additional environment variables for the CLI process. Excluded from JSON serialization; token-pattern keys are redacted in `ToString()`. |
+| `GitHubToken` | Advanced direct token escape hatch; excluded from JSON serialization and redacted by `ToString()`. |
 | `GitHubTokenProvider` | Advanced callback for secure token retrieval; wins over `GitHubToken`. |
+| `ConfigureCopilotClient` | Advanced delegate for customizing `CopilotClientOptions`. Routing properties are guarded; see BYOK section. |
 | `TraceEvents` | Enables verbose SDK logging and emits a startup warning when enabled. |
 | `AgentName` | Display name for the resulting `AIAgent`; defaults to `Squad`. |
 | `Instructions` | Optional system instructions passed to the inner Copilot agent. |
 
+## Security
+
+- **Credential redaction:** `GitHubToken` and `Environment` values whose keys match `*TOKEN*`, `*KEY*`, `*SECRET*`, `*HMAC*`, `*PASSWORD*`, or `*CREDENTIAL*` are always redacted in `ToString()` output.
+- **JSON safety:** `GitHubToken`, `GitHubTokenProvider`, `Environment`, and `ConfigureCopilotClient` are marked `[JsonIgnore]` and will not appear in JSON serialization output.
+- **Routing guard:** The `ConfigureCopilotClient` delegate cannot change `Cwd`, `CliPath`, or `CliArgs` — changes are silently restored to prevent routing the agent to an unintended CLI process.
+- **TraceEvents warning:** Enabling `TraceEvents` logs a startup warning because verbose SDK traces may include sensitive operational details.
+- **Avoid hardcoded tokens:** Never embed tokens in source code. Use `GitHubTokenProvider` for production token retrieval from Key Vault, managed identity, or similar secure stores.
+
 ## Notes for v0.1-preview
 
 - Default DI lifetime is scoped. An overload accepts any `ServiceLifetime`.
-- DI registers both `SquadAgent` and base `AIAgent`.
+- DI registers both `SquadAgent` and base `AIAgent` (non-keyed). Keyed DI registers both `SquadAgent` and `AIAgent` under the same key.
 - Multi-targeting and Aspire telemetry remain candidates for a later preview.
 - The package does not validate that `SquadFolderPath` exists; consumers should validate their deployment paths.
 - `TraceEvents` can log sensitive operational details. Keep it off unless debugging.
 
@@ -65,8 +65,21 @@ private SquadAgent(CopilotClient copilotClient, SquadAgentOptions options, ILogg
             options.AgentName, options.SquadFolderPath);
     }
 
+    // ── Extensibility seam ──────────────────────────────────────────────
+    // CreateCopilotClient is the single factory method that translates
+    // SquadAgentOptions into a live CopilotClient. Three extension points
+    // feed into it:
+    //   1. GitHubTokenProvider / GitHubToken — credential override.
+    //   2. ConfigureCopilotClient — BYOK delegate for advanced SDK tuning.
+    //   3. Connection-string binding (handled before this method by the
+    //      SquadAgentOptionsConfigurator).
+    // Any future credential-store or model-property hooks should integrate
+    // through SquadAgentOptions and be applied inside this method.
+    // ────────────────────────────────────────────────────────────────────
     private static CopilotClient CreateCopilotClient(SquadAgentOptions options, ILoggerFactory? loggerFactory)
     {
+        var logger = loggerFactory?.CreateLogger<SquadAgent>();
+
         // Resolve token: provider takes precedence over direct property
         string? resolvedToken = null;
         if (options.GitHubTokenProvider is not null)
@@ -110,6 +123,60 @@ private static CopilotClient CreateCopilotClient(SquadAgentOptions options, ILog
             clientOptions.Logger = loggerFactory.CreateLogger<CopilotClient>();
         }
 
+        // ── BYOK / ConfigureCopilotClient delegate ─────────────────────
+        // Allow consumers to customize the CopilotClientOptions after Squad
+        // applies its standard values. After the delegate runs, snapshot and
+        // restore routing-critical properties to prevent accidental or
+        // malicious changes that would route the agent to a different CLI
+        // process. (Picard Condition 1: hard routing gate.)
+        if (options.ConfigureCopilotClient is not null)
+        {
+            // Snapshot routing properties before the delegate runs
+            var snapshotCwd = clientOptions.Cwd;
+            var snapshotCliPath = clientOptions.CliPath;
+            var snapshotCliArgs = clientOptions.CliArgs;
+
+            options.ConfigureCopilotClient(clientOptions);
+
+            // Restore routing properties if changed (SC-3: post-delegate warning)
+            bool restored = false;
+            if (!string.Equals(clientOptions.Cwd, snapshotCwd, StringComparison.Ordinal))
+            {
+                logger?.LogWarning(
+                    "ConfigureCopilotClient delegate changed Cwd from '{Original}' to '{Changed}'; " +
+                    "restoring original value to preserve Squad routing.",
+                    snapshotCwd, clientOptions.Cwd);
+                clientOptions.Cwd = snapshotCwd;
+                restored = true;
+            }
+
+            if (!string.Equals(clientOptions.CliPath, snapshotCliPath, StringComparison.Ordinal))
+            {
+                logger?.LogWarning(
+                    "ConfigureCopilotClient delegate changed CliPath from '{Original}' to '{Changed}'; " +
+                    "restoring original value to preserve Squad routing.",
+                    snapshotCliPath, clientOptions.CliPath);
+                clientOptions.CliPath = snapshotCliPath;
+                restored = true;
+            }
+
+            if (!ReferenceEquals(clientOptions.CliArgs, snapshotCliArgs))
+            {
+                logger?.LogWarning(
+                    "ConfigureCopilotClient delegate replaced CliArgs; " +
+                    "restoring original value to preserve Squad routing.");
+                clientOptions.CliArgs = snapshotCliArgs;
+                restored = true;
+            }
+
+            if (restored)
+            {
+                logger?.LogWarning(
+                    "One or more routing properties were restored after ConfigureCopilotClient delegate ran. " +
+                    "To set Cwd, CliPath, or CliArgs, configure them on SquadAgentOptions instead.");
+            }
+        }
+
         return new CopilotClient(clientOptions);
     }
 
 
@@ -1,3 +1,6 @@
+using System.Text.Json.Serialization;
+using GitHub.Copilot.SDK;
+
 namespace Squad.Agents.AI;
 
 /// <summary>
@@ -37,6 +40,14 @@ public sealed class SquadAgentOptions
     /// <summary>
     /// Gets additional environment variables injected into the CLI process.
     /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This dictionary is excluded from JSON serialization to prevent credential leakage.
+    /// Values for keys matching token/secret patterns are redacted in <see cref="ToString"/>.
+    /// </para>
+    /// <para>Avoid placing user-controlled values in this dictionary.</para>
+    /// </remarks>
+    [JsonIgnore]
     public IDictionary<string, string?> Environment { get; } = new Dictionary<string, string?>();
 
     /// <summary>
@@ -46,7 +57,7 @@ public sealed class SquadAgentOptions
     /// The value is ignored by JSON serialization and redacted by <see cref="ToString"/>, but still lives in the options object.
     /// Prefer leaving this unset for local signed-in user authentication; use <see cref="GitHubTokenProvider"/> for production hosts that retrieve tokens dynamically.
     /// </remarks>
-    [System.Text.Json.Serialization.JsonIgnore]
+    [JsonIgnore]
     public string? GitHubToken { get; set; }
 
     /// <summary>
@@ -55,6 +66,7 @@ public sealed class SquadAgentOptions
     /// <remarks>
     /// When set, this provider takes precedence over <see cref="GitHubToken"/>.
     /// </remarks>
+    [JsonIgnore]
     public Func<CancellationToken, ValueTask<string?>>? GitHubTokenProvider { get; set; }
 
     /// <summary>
@@ -75,13 +87,66 @@ public sealed class SquadAgentOptions
     /// </summary>
     public string? Instructions { get; set; }
 
+    /// <summary>
+    /// Gets or sets a delegate that customizes the underlying <see cref="CopilotClientOptions"/> after Squad
+    /// applies its standard values. Use this for advanced scenarios such as injecting custom environment
+    /// variables, setting timeouts, or providing a custom logger to the Copilot SDK.
+    /// </summary>
+    /// <remarks>
+    /// <para><b>Security note:</b> Do not override <c>Cwd</c>, <c>CliPath</c>, or <c>CliArgs</c> through this
+    /// delegate — Squad enforces routing invariants and will restore its own values if they are changed.
+    /// A warning is logged when this occurs.</para>
+    /// <para>The delegate has full read/write access to <see cref="CopilotClientOptions"/>, including
+    /// <c>GitHubToken</c>. If the delegate replaces the token, the replacement takes effect.
+    /// Document this as the final authority on token value.</para>
+    /// </remarks>
+    /// <example>
+    /// <code>
+    /// options.ConfigureCopilotClient = clientOpts =>
+    /// {
+    ///     clientOpts.Environment["MY_CUSTOM_VAR"] = "custom-value";
+    /// };
+    /// </code>
+    /// </example>
+    [JsonIgnore]
+    public Action<CopilotClientOptions>? ConfigureCopilotClient { get; set; }
+
+    private static readonly string[] TokenPatterns = { "TOKEN", "KEY", "SECRET", "HMAC", "PASSWORD", "CREDENTIAL" };
+
+    private static bool IsTokenKey(string key)
+    {
+        var upper = key.ToUpperInvariant();
+        foreach (var pattern in TokenPatterns)
+        {
+            if (upper.Contains(pattern))
+                return true;
+        }
+        return false;
+    }
+
     /// <summary>
     /// Returns a diagnostic representation with sensitive values redacted.
     /// </summary>
+    /// <remarks>
+    /// <para><c>GitHubToken</c> is always shown as <c>[REDACTED]</c>.</para>
+    /// <para><c>Environment</c> values whose keys match token/secret patterns
+    /// (<c>*TOKEN*</c>, <c>*KEY*</c>, <c>*SECRET*</c>, <c>*HMAC*</c>, <c>*PASSWORD*</c>, <c>*CREDENTIAL*</c>)
+    /// are shown as <c>[REDACTED]</c>; other environment entries show their value.</para>
+    /// </remarks>
     /// <returns>A string containing non-secret option values.</returns>
     public override string ToString()
     {
+        var envDisplay = "{}";
+        if (Environment.Count > 0)
+        {
+            var entries = Environment.Select(kvp =>
+                IsTokenKey(kvp.Key)
+                    ? $"{kvp.Key}=[REDACTED]"
+                    : $"{kvp.Key}={kvp.Value}");
+            envDisplay = $"{{ {string.Join(", ", entries)} }}";
+        }
+
         return $"SquadAgentOptions {{ SquadFolderPath = {SquadFolderPath}, AgentName = {AgentName}, " +
-               $"GitHubToken = [REDACTED], TraceEvents = {TraceEvents} }}";
+               $"GitHubToken = [REDACTED], Environment = {envDisplay}, TraceEvents = {TraceEvents} }}";
     }
 }