Add config dir to session options

dotnet/src/Client.cs

@@ -343,7 +343,8 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig? config = nul
             config?.OnPermissionRequest != null ? true : null,
             config?.Streaming == true ? true : null,
             config?.McpServers,
-            config?.CustomAgents);
+            config?.CustomAgents,
+            config?.ConfigDir);
 
         var response = await connection.Rpc.InvokeWithCancellationAsync<CreateSessionResponse>(
             "session.create", [request], cancellationToken);
@@ -922,7 +923,8 @@ private record CreateSessionRequest(
         bool? RequestPermission,
         bool? Streaming,
         Dictionary<string, object>? McpServers,
-        List<CustomAgentConfig>? CustomAgents);
+        List<CustomAgentConfig>? CustomAgents,
+        string? ConfigDir);
 
     private record ToolDefinition(
         string Name,

dotnet/src/Types.cs

@@ -293,6 +293,13 @@ public class SessionConfig
 {
     public string? SessionId { get; set; }
     public string? Model { get; set; }
+
+    /// <summary>
+    /// Override the default configuration directory location.
+    /// When specified, the session will use this directory for storing config and state.
+    /// </summary>
+    public string? ConfigDir { get; set; }
+
     public ICollection<AIFunction>? Tools { get; set; }
     public SystemMessageConfig? SystemMessage { get; set; }
     public List<string>? AvailableTools { get; set; }

dotnet/test/SessionTests.cs

@@ -322,4 +322,25 @@ public async Task Should_Receive_Session_Events()
 
         await session.DisposeAsync();
     }
+
+    [Fact]
+    public async Task Should_Create_Session_With_Custom_Config_Dir()
+    {
+        var customConfigDir = Path.Combine(Ctx.HomeDir, "custom-config");
+        var session = await Client.CreateSessionAsync(new SessionConfig { ConfigDir = customConfigDir });
+
+        Assert.Matches(@"^[a-f0-9-]+$", session.SessionId);
+
+        // Verify config.json was written to the custom config dir
+        var configPath = Path.Combine(customConfigDir, "github-copilot", "config.json");
+        Assert.True(File.Exists(configPath), $"Expected config.json at {configPath}");
+        var configContent = System.Text.Json.JsonDocument.Parse(await File.ReadAllTextAsync(configPath));
+        Assert.Equal(session.SessionId, configContent.RootElement.GetProperty("sessionId").GetString());
+
+        // Session should work normally with custom config dir
+        await session.SendAsync(new MessageOptions { Prompt = "What is 1+1?" });
+        var assistantMessage = await TestHelper.GetFinalAssistantMessageAsync(session);
+        Assert.NotNull(assistantMessage);
+        Assert.Contains("2", assistantMessage!.Data.Content);
+    }
 }

go/client.go

@@ -534,6 +534,10 @@ func (c *Client) CreateSession(config *SessionConfig) (*Session, error) {
 			}
 			params["customAgents"] = customAgents
 		}
+		// Add config directory override
+		if config.ConfigDir != "" {
+			params["configDir"] = config.ConfigDir
+		}
 	}
 
 	result, err := c.client.Request("session.create", params)

go/e2e/session_test.go

@@ -1,6 +1,8 @@
 package e2e
 
 import (
+	"encoding/json"
+	"os"
 	"regexp"
 	"strings"
 	"testing"
@@ -687,6 +689,52 @@ func TestSession(t *testing.T) {
 			t.Errorf("Expected assistant message to contain '300', got %v", assistantMessage.Data.Content)
 		}
 	})
+
+	t.Run("should create session with custom config dir", func(t *testing.T) {
+		ctx.ConfigureForTest(t)
+
+		customConfigDir := ctx.HomeDir + "/custom-config"
+		session, err := client.CreateSession(&copilot.SessionConfig{
+			ConfigDir: customConfigDir,
+		})
+		if err != nil {
+			t.Fatalf("Failed to create session with custom config dir: %v", err)
+		}
+
+		matched, _ := regexp.MatchString(`^[a-f0-9-]+$`, session.SessionID)
+		if !matched {
+			t.Errorf("Expected session ID to match UUID pattern, got %q", session.SessionID)
+		}
+
+		// Verify config.json was written to the custom config dir
+		configPath := customConfigDir + "/github-copilot/config.json"
+		configData, err := os.ReadFile(configPath)
+		if err != nil {
+			t.Fatalf("Failed to read config.json at %s: %v", configPath, err)
+		}
+		var configContent map[string]interface{}
+		if err := json.Unmarshal(configData, &configContent); err != nil {
+			t.Fatalf("Failed to parse config.json: %v", err)
+		}
+		if configContent["sessionId"] != session.SessionID {
+			t.Errorf("Expected config.json sessionId to be %q, got %v", session.SessionID, configContent["sessionId"])
+		}
+
+		// Session should work normally with custom config dir
+		_, err = session.Send(copilot.MessageOptions{Prompt: "What is 1+1?"})
+		if err != nil {
+			t.Fatalf("Failed to send message: %v", err)
+		}
+
+		assistantMessage, err := testharness.GetFinalAssistantMessage(session, 60*time.Second)
+		if err != nil {
+			t.Fatalf("Failed to get assistant message: %v", err)
+		}
+
+		if assistantMessage.Data.Content == nil || !strings.Contains(*assistantMessage.Data.Content, "2") {
+			t.Errorf("Expected assistant message to contain '2', got %v", assistantMessage.Data.Content)
+		}
+	})
 }
 
 func getSystemMessage(exchange testharness.ParsedHttpExchange) string {

go/types.go

@@ -144,6 +144,9 @@ type SessionConfig struct {
 	SessionID string
 	// Model to use for this session
 	Model string
+	// ConfigDir overrides the default configuration directory location.
+	// When specified, the session will use this directory for storing config and state.
+	ConfigDir string
 	// Tools exposes caller-implemented tools to the CLI
 	Tools []Tool
 	// SystemMessage configures system message customization

nodejs/src/client.ts

@@ -446,6 +446,7 @@ export class CopilotClient {
             streaming: config.streaming,
             mcpServers: config.mcpServers,
             customAgents: config.customAgents,
+            configDir: config.configDir,
         });
 
         const sessionId = (response as { sessionId: string }).sessionId;

nodejs/src/types.ts

@@ -324,6 +324,12 @@ export interface SessionConfig {
      */
     model?: string;
 
+    /**
+     * Override the default configuration directory location.
+     * When specified, the session will use this directory for storing config and state.
+     */
+    configDir?: string;
+
     /**
      * Tools exposed to the CLI server
      */

nodejs/test/e2e/session.test.ts

@@ -1,3 +1,4 @@
+import * as fs from "node:fs";
 import { describe, expect, it, onTestFinished } from "vitest";
 import { ParsedHttpExchange } from "../../../test/harness/replayingCapiProxy.js";
 import { CopilotClient } from "../../src/index.js";
@@ -334,6 +335,26 @@
         const assistantMessage = await getFinalAssistantMessage(session);
         expect(assistantMessage.data.content).toContain("300");
     });
+
+    it("should create session with custom config dir", async () => {
+        const customConfigDir = `${homeDir}/custom-config`;
+        const session = await client.createSession({
+            configDir: customConfigDir,
+        });
+
+        expect(session.sessionId).toMatch(/^[a-f0-9-]+$/);
+
+        // Verify config.json was written to the custom config dir
+        const configPath = `${customConfigDir}/github-copilot/config.json`;
+        expect(fs.existsSync(configPath)).toBe(true);
+        const configContent = JSON.parse(fs.readFileSync(configPath, "utf-8"));
+        expect(configContent).toHaveProperty("sessionId", session.sessionId);
+
+        // Session should work normally with custom config dir
+        await session.send({ prompt: "What is 1+1?" });
+        const assistantMessage = await getFinalAssistantMessage(session);
+        expect(assistantMessage.data.content).toContain("2");
+    });
 });
 
 function getSystemMessage(exchange: ParsedHttpExchange): string | undefined {

python/copilot/client.py

@@ -400,6 +400,11 @@ async def create_session(self, config: Optional[SessionConfig] = None) -> Copilo
                 self._convert_custom_agent_to_wire_format(agent) for agent in custom_agents
             ]
 
+        # Add config directory override if provided
+        config_dir = cfg.get("config_dir")
+        if config_dir:
+            payload["configDir"] = config_dir
+
         if not self._client:
             raise RuntimeError("Client not connected")
         response = await self._client.request("session.create", payload)

python/copilot/types.py

@@ -216,6 +216,9 @@ class SessionConfig(TypedDict, total=False):
     mcp_servers: Dict[str, MCPServerConfig]
     # Custom agent configurations for the session
     custom_agents: List[CustomAgentConfig]
+    # Override the default configuration directory location.
+    # When specified, the session will use this directory for storing config and state.
+    config_dir: str
 
 
 # Azure-specific provider options

python/e2e/test_session.py

@@ -360,6 +360,27 @@ def on_event(event):
         assistant_message = await get_final_assistant_message(session)
         assert "300" in assistant_message.data.content
 
+    async def test_should_create_session_with_custom_config_dir(self, ctx: E2ETestContext):
+        import json
+        import os
+
+        custom_config_dir = os.path.join(ctx.home_dir, "custom-config")
+        session = await ctx.client.create_session({"config_dir": custom_config_dir})
+
+        assert session.session_id
+
+        # Verify config.json was written to the custom config dir
+        config_path = os.path.join(custom_config_dir, "github-copilot", "config.json")
+        assert os.path.exists(config_path), f"Expected config.json at {config_path}"
+        with open(config_path) as f:
+            config_content = json.load(f)
+        assert config_content.get("sessionId") == session.session_id
+
+        # Session should work normally with custom config dir
+        await session.send({"prompt": "What is 1+1?"})
+        assistant_message = await get_final_assistant_message(session)
+        assert "2" in assistant_message.data.content
+
 
 def _get_system_message(exchange: dict) -> str:
     messages = exchange.get("request", {}).get("messages", [])

test/snapshots/session/should_create_session_with_custom_config_dir.yaml

@@ -0,0 +1,10 @@
+models:
+  - claude-sonnet-4.5
+conversations:
+  - messages:
+      - role: system
+        content: ${system}
+      - role: user
+        content: What is 1+1?
+      - role: assistant
+        content: 1 + 1 = 2