Add missing options to ResumeSessionConfig for parity with create (#376)

* Add missing options to ResumeSessionConfig for parity with create

- Add model, systemMessage, availableTools, excludedTools, configDir,
  and infiniteSessions to resume session config in all SDKs
- Update client implementations to pass new options to server
- Add "Resume Options" documentation section
- Bump @github/copilot dependency to ^0.0.403

* Update python/copilot/client.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix lint

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: friggeri

docs/guides/session-persistence.md

@@ -164,6 +164,37 @@ var session = await client.ResumeSessionAsync("user-123-task-456");
 await session.SendAndWaitAsync(new MessageOptions { Prompt = "What did we discuss earlier?" });
 ```
 
+## Resume Options
+
+When resuming a session, you can optionally reconfigure many settings. This is useful when you need to change the model, update tool configurations, or modify behavior.
+
+| Option | Description |
+|--------|-------------|
+| `model` | Change the model for the resumed session |
+| `systemMessage` | Override or extend the system prompt |
+| `availableTools` | Restrict which tools are available |
+| `excludedTools` | Disable specific tools |
+| `provider` | Re-provide BYOK credentials (required for BYOK sessions) |
+| `reasoningEffort` | Adjust reasoning effort level |
+| `streaming` | Enable/disable streaming responses |
+| `workingDirectory` | Change the working directory |
+| `configDir` | Override configuration directory |
+| `mcpServers` | Configure MCP servers |
+| `customAgents` | Configure custom agents |
+| `skillDirectories` | Directories to load skills from |
+| `disabledSkills` | Skills to disable |
+| `infiniteSessions` | Configure infinite session behavior |
+
+### Example: Changing Model on Resume
+
+```typescript
+// Resume with a different model
+const session = await client.resumeSession("user-123-task-456", {
+  model: "claude-sonnet-4",  // Switch to a different model
+  reasoningEffort: "high",   // Increase reasoning effort
+});
+```
+
 ## Using BYOK (Bring Your Own Key) with Resumed Sessions
 
 When using your own API keys, you must re-provide the provider configuration when resuming. API keys are never persisted to disk for security reasons.

dotnet/src/Client.cs

@@ -437,19 +437,25 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
 
         var request = new ResumeSessionRequest(
             sessionId,
+            config?.Model,
             config?.ReasoningEffort,
             config?.Tools?.Select(ToolDefinition.FromAIFunction).ToList(),
+            config?.SystemMessage,
+            config?.AvailableTools,
+            config?.ExcludedTools,
             config?.Provider,
             config?.OnPermissionRequest != null ? true : null,
             config?.OnUserInputRequest != null ? true : null,
             hasHooks ? true : null,
             config?.WorkingDirectory,
+            config?.ConfigDir,
             config?.DisableResume == true ? true : null,
             config?.Streaming == true ? true : null,
             config?.McpServers,
             config?.CustomAgents,
             config?.SkillDirectories,
-            config?.DisabledSkills);
+            config?.DisabledSkills,
+            config?.InfiniteSessions);
 
         var response = await InvokeRpcAsync<ResumeSessionResponse>(
             connection.Rpc, "session.resume", [request], cancellationToken);
@@ -1326,19 +1332,25 @@ internal record CreateSessionResponse(
 
     internal record ResumeSessionRequest(
         string SessionId,
+        string? Model,
         string? ReasoningEffort,
         List<ToolDefinition>? Tools,
+        SystemMessageConfig? SystemMessage,
+        List<string>? AvailableTools,
+        List<string>? ExcludedTools,
         ProviderConfig? Provider,
         bool? RequestPermission,
         bool? RequestUserInput,
         bool? Hooks,
         string? WorkingDirectory,
+        string? ConfigDir,
         bool? DisableResume,
         bool? Streaming,
         Dictionary<string, object>? McpServers,
         List<CustomAgentConfig>? CustomAgents,
         List<string>? SkillDirectories,
-        List<string>? DisabledSkills);
+        List<string>? DisabledSkills,
+        InfiniteSessionConfig? InfiniteSessions);
 
     internal record ResumeSessionResponse(
         string SessionId,

dotnet/src/Types.cs

@@ -770,7 +770,30 @@ public class SessionConfig
 
 public class ResumeSessionConfig
 {
+    /// <summary>
+    /// Model to use for this session. Can change the model when resuming.
+    /// </summary>
+    public string? Model { get; set; }
+
     public ICollection<AIFunction>? Tools { get; set; }
+
+    /// <summary>
+    /// System message configuration.
+    /// </summary>
+    public SystemMessageConfig? SystemMessage { get; set; }
+
+    /// <summary>
+    /// List of tool names to allow. When specified, only these tools will be available.
+    /// Takes precedence over ExcludedTools.
+    /// </summary>
+    public List<string>? AvailableTools { get; set; }
+
+    /// <summary>
+    /// List of tool names to disable. All other tools remain available.
+    /// Ignored if AvailableTools is specified.
+    /// </summary>
+    public List<string>? ExcludedTools { get; set; }
+
     public ProviderConfig? Provider { get; set; }
 
     /// <summary>
@@ -801,6 +824,11 @@ public class ResumeSessionConfig
     /// </summary>
     public string? WorkingDirectory { get; set; }
 
+    /// <summary>
+    /// Override the default configuration directory location.
+    /// </summary>
+    public string? ConfigDir { get; set; }
+
     /// <summary>
     /// When true, the session.resume event is not emitted.
     /// Default: false (resume event is emitted).
@@ -834,6 +862,11 @@ public class ResumeSessionConfig
     /// List of skill names to disable.
     /// </summary>
     public List<string>? DisabledSkills { get; set; }
+
+    /// <summary>
+    /// Infinite session configuration for persistent workspaces and automatic compaction.
+    /// </summary>
+    public InfiniteSessionConfig? InfiniteSessions { get; set; }
 }
 
 public class MessageOptions

go/client.go

@@ -681,9 +681,39 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	}
 
 	if config != nil {
+		if config.Model != "" {
+			params["model"] = config.Model
+		}
 		if config.ReasoningEffort != "" {
 			params["reasoningEffort"] = config.ReasoningEffort
 		}
+		if config.SystemMessage != nil {
+			systemMessage := make(map[string]any)
+
+			if config.SystemMessage.Mode != "" {
+				systemMessage["mode"] = config.SystemMessage.Mode
+			}
+
+			if config.SystemMessage.Mode == "replace" {
+				if config.SystemMessage.Content != "" {
+					systemMessage["content"] = config.SystemMessage.Content
+				}
+			} else {
+				if config.SystemMessage.Content != "" {
+					systemMessage["content"] = config.SystemMessage.Content
+				}
+			}
+
+			if len(systemMessage) > 0 {
+				params["systemMessage"] = systemMessage
+			}
+		}
+		if len(config.AvailableTools) > 0 {
+			params["availableTools"] = config.AvailableTools
+		}
+		if len(config.ExcludedTools) > 0 {
+			params["excludedTools"] = config.ExcludedTools
+		}
 		if len(config.Tools) > 0 {
 			toolDefs := make([]map[string]any, 0, len(config.Tools))
 			for _, tool := range config.Tools {
@@ -731,6 +761,10 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 		if config.WorkingDirectory != "" {
 			params["workingDirectory"] = config.WorkingDirectory
 		}
+		// Add config directory
+		if config.ConfigDir != "" {
+			params["configDir"] = config.ConfigDir
+		}
 		// Add disable resume flag
 		if config.DisableResume {
 			params["disableResume"] = true
@@ -774,6 +808,20 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 		if len(config.DisabledSkills) > 0 {
 			params["disabledSkills"] = config.DisabledSkills
 		}
+		// Add infinite sessions configuration
+		if config.InfiniteSessions != nil {
+			infiniteSessions := map[string]any{}
+			if config.InfiniteSessions.Enabled != nil {
+				infiniteSessions["enabled"] = *config.InfiniteSessions.Enabled
+			}
+			if config.InfiniteSessions.BackgroundCompactionThreshold != nil {
+				infiniteSessions["backgroundCompactionThreshold"] = *config.InfiniteSessions.BackgroundCompactionThreshold
+			}
+			if config.InfiniteSessions.BufferExhaustionThreshold != nil {
+				infiniteSessions["bufferExhaustionThreshold"] = *config.InfiniteSessions.BufferExhaustionThreshold
+			}
+			params["infiniteSessions"] = infiniteSessions
+		}
 	}
 
 	result, err := c.client.Request("session.resume", params)

go/types.go

@@ -399,8 +399,18 @@ type ToolResult struct {
 
 // ResumeSessionConfig configures options when resuming a session
 type ResumeSessionConfig struct {
+	// Model to use for this session. Can change the model when resuming.
+	Model string
 	// Tools exposes caller-implemented tools to the CLI
 	Tools []Tool
+	// SystemMessage configures system message customization
+	SystemMessage *SystemMessageConfig
+	// AvailableTools is a list of tool names to allow. When specified, only these tools will be available.
+	// Takes precedence over ExcludedTools.
+	AvailableTools []string
+	// ExcludedTools is a list of tool names to disable. All other tools remain available.
+	// Ignored if AvailableTools is specified.
+	ExcludedTools []string
 	// Provider configures a custom model provider
 	Provider *ProviderConfig
 	// ReasoningEffort level for models that support it.
@@ -415,6 +425,8 @@ type ResumeSessionConfig struct {
 	// WorkingDirectory is the working directory for the session.
 	// Tool operations will be relative to this directory.
 	WorkingDirectory string
+	// ConfigDir overrides the default configuration directory location.
+	ConfigDir string
 	// Streaming enables streaming of assistant message and reasoning chunks.
 	// When true, assistant.message_delta and assistant.reasoning_delta events
 	// with deltaContent are sent as the response is generated.
@@ -427,6 +439,8 @@ type ResumeSessionConfig struct {
 	SkillDirectories []string
 	// DisabledSkills is a list of skill names to disable
 	DisabledSkills []string
+	// InfiniteSessions configures infinite sessions for persistent workspaces and automatic compaction.
+	InfiniteSessions *InfiniteSessionConfig
 	// DisableResume, when true, skips emitting the session.resume event.
 	// Useful for reconnecting to a session without triggering resume-related side effects.
 	DisableResume bool

nodejs/package-lock.json

@@ -40,7 +40,7 @@
   "author": "GitHub",
   "license": "MIT",
   "dependencies": {
-    "@github/copilot": "^0.0.402",
+    "@github/copilot": "^0.0.403",
     "vscode-jsonrpc": "^8.2.1",
     "zod": "^4.3.6"
   },