feat: Introduce new SDK support for Copilot CLI sessions and models #3577

DonJayamanne · 2026-02-09T06:53:10Z

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Copilot

Pull request overview

Introduces an opt-in path to run Copilot CLI chat sessions and model resolution via the new @github/copilot-sdk, while keeping the existing CLI SDK implementation as the default/fallback.

Changes:

Add a new advanced setting (chat.advanced.cli.sdk.enabled) and a selector service to choose between old vs new CLI SDK implementations.
Route Copilot CLI session + model services through delegating implementations to support both SDKs.
Add new @github/copilot-sdk dependency and update session history retrieval to be async.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
src/platform/configuration/common/configurationService.ts	Adds a config key to gate new Copilot CLI SDK usage.
src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts	Updates session history retrieval to await the now-async API.
src/extension/chatSessions/vscode-node/chatSessions.ts	Wires new selector/delegating services into DI for Copilot CLI chat sessions.
src/extension/agents/copilotcli/node/sdk/delegatingSessionService.ts	Adds delegating session service that routes to old/new implementations.
src/extension/agents/copilotcli/node/sdk/delegatingModels.ts	Adds delegating model service that routes to old/new implementations.
src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts	Implements session management using `@github/copilot-sdk` client sessions.
src/extension/agents/copilotcli/node/sdk/copilotcliSession.ts	Wraps `@github/copilot-sdk` session events into the existing ICopilotCLISession contract.
src/extension/agents/copilotcli/node/sdk/copilotcliModels.ts	Implements model listing/default model via `CopilotClient.listModels()`.
src/extension/agents/copilotcli/node/sdk/copilotClientManager.ts	Introduces a manager to create/start/stop a `CopilotClient`.
src/extension/agents/copilotcli/node/copilotcliSession.ts	Makes `getChatHistory()` async on the legacy session implementation.
src/extension/agents/copilotcli/node/copilotCliSdkSelector.ts	Adds selector service based on the new config key.
package.json	Adds `@github/copilot-sdk` dependency.
package-lock.json	Locks `@github/copilot-sdk` and its transitive dependencies.

Comments suppressed due to low confidence (2)

src/extension/agents/copilotcli/node/sdk/copilotClientManager.ts:71

Same logging issue here: pass the caught error as the first argument to logService.error(...) and the context string as the second, so stack/details are preserved and log formatting is consistent.

				this.logService.trace('[CopilotClientManager] CopilotClient stopped');
			} catch (error) {
				this.logService.error('[CopilotClientManager] Failed to stop CopilotClient', error);
			}

src/extension/agents/copilotcli/node/sdk/copilotcliModels.ts:32

ILogService.error expects the Error (or error string) as the first parameter, and an optional context message second. These calls currently pass the context string first and the error object second, which usually loses stack/details. Consider swapping the arguments to preserve exception details.

		// Eagerly fetch available models so that they're ready when needed.
		this._availableModels.value.catch(error => {
			this.logService.error('[NewSdkCopilotCLIModels] Failed to fetch available models', error);
		});

src/extension/agents/copilotcli/node/sdk/delegatingSessionService.ts

Copilot · 2026-02-09T06:59:05Z

src/extension/agents/copilotcli/node/sdk/delegatingSessionService.ts

+		this._oldService = this._register(instantiationService.createInstance(CopilotCLISessionService));
+		this._newService = this._register(instantiationService.createInstance(NewSdkCopilotCLISessionService));
+
+		// Forward change events from both services
+		this._register(this._oldService.onDidChangeSessions(() => this._onDidChangeSessions.fire()));
+		this._register(this._newService.onDidChangeSessions(() => this._onDidChangeSessions.fire()));
+	}


The delegating session service eagerly creates both the old and new session services. Both implementations set up filesystem watchers on the same session-state directory and forward onDidChangeSessions, which can cause duplicated change events and unnecessary overhead even when only one SDK is in use. Consider lazily instantiating the inactive service (or centralizing file watching in the delegator) to avoid duplicate watchers/events.

src/extension/agents/copilotcli/node/sdk/delegatingModels.ts

src/extension/agents/copilotcli/node/sdk/copilotcliSession.ts

src/extension/agents/copilotcli/node/sdk/copilotClientManager.ts

src/extension/agents/copilotcli/node/sdk/copilotcliModels.ts

src/extension/agents/copilotcli/node/sdk/copilotcliSession.ts

Copilot · 2026-02-09T06:59:06Z

package.json

 		"@github/blackbird-external-ingest-utils": "^0.2.0",
 		"@github/copilot": "^0.0.400",
+		"@github/copilot-sdk": "^0.1.22",


Adding @github/copilot-sdk introduces a nested dependency on @github/copilot@0.0.403 while the repo currently depends on @github/copilot@^0.0.400 at the top level. This will typically result in two Copilot CLI binaries being installed (larger install footprint and potentially confusing runtime behavior). Consider aligning the root @github/copilot version (or using an override/resolution) so npm can dedupe to a single version.

Under discussion

src/extension/agents/copilotcli/node/sdk/delegatingSessionService.ts

Copilot

Pull request overview

Copilot reviewed 14 out of 15 changed files in this pull request and generated 9 comments.

Copilot · 2026-02-12T19:31:26Z

src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts

+		toolCalls: Map<string, ToolCall>,
+	): NewSdkRefCountedSession {
+		const unsubscribeToolStart = sdkSession.on('tool.execution_start', (event) => {
+			toolCalls.set(event.id, event.data as unknown as ToolCall);


toolCalls is later accessed via toolCalls.get(toolCallId) (from permReq.toolCallId), but this listener stores entries under event.id. If event.id is not the same as event.data.toolCallId, permission handling/edit tracking will fail to find the tool call (affecting auto-approval and edit tracking). Store tool calls keyed by the tool-call id (e.g. event.data.toolCallId) to match the lookup path.

Suggested change

toolCalls.set(event.id, event.data as unknown as ToolCall);

const toolCallId = (event as { data: { toolCallId?: string } }).data.toolCallId ?? event.id;

toolCalls.set(toolCallId, event.data as unknown as ToolCall);

Copilot · 2026-02-12T19:31:27Z

package.nls.json

 	"github.copilot.config.cli.customAgents.enabled": "Enable Custom Agents for Background Agents.",
 	"github.copilot.config.cli.mcp.enabled": "Enable Model Context Protocol (MCP) server for Background Agents.",
 	"github.copilot.config.cli.branchSupport.enabled": "Enable branch support for Background Agents.",
+	"github.copilot.config.cli.sdk.enabled": "Enable the new SDK for Background Agents.",


DelegatingCopilotCLIModels / DelegatingCopilotCLISessionService evaluate the SDK selector once on first access and require a reload for changes to take effect, but this setting description doesn’t mention that. Consider adding “Requires VS Code reload” (similar to the sessionController setting) to avoid confusing users who toggle it at runtime.

Suggested change

"github.copilot.config.cli.sdk.enabled": "Enable the new SDK for Background Agents.",

"github.copilot.config.cli.sdk.enabled": "Enable the new SDK for Background Agents. Requires VS Code reload.",

Copilot · 2026-02-12T19:31:27Z

src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts

+		const [model, history] = await Promise.all([
+			(existingSession ? (_sessionModel.get(copilotcliSessionId) ?? await existingSession.object.getSelectedModelId()) : _sessionModel.get(copilotcliSessionId)) ?? await this.getCustomAgentModel(defaultAgent, token) ?? defaultModel,
+			existingSession?.object?.getChatHistory() || []
+		]);


The Promise.all([...]) here doesn’t actually run model resolution and history loading in parallel because the first array element contains await expressions and is evaluated sequentially before Promise.all executes. Consider turning the model computation into a Promise (e.g., an async IIFE) so history loading can overlap with model selection, or just compute them sequentially without Promise.all for clarity.

Suggested change

const [model, history] = await Promise.all([

(existingSession ? (_sessionModel.get(copilotcliSessionId) ?? await existingSession.object.getSelectedModelId()) : _sessionModel.get(copilotcliSessionId)) ?? await this.getCustomAgentModel(defaultAgent, token) ?? defaultModel,

existingSession?.object?.getChatHistory() || []

]);

const modelPromise = (async () => {

return (existingSession ? (_sessionModel.get(copilotcliSessionId) ?? await existingSession.object.getSelectedModelId()) : _sessionModel.get(copilotcliSessionId)) ?? await this.getCustomAgentModel(defaultAgent, token) ?? defaultModel;

})();

const historyPromise = existingSession?.object?.getChatHistory() ?? Promise.resolve([]);

const [model, history] = await Promise.all([modelPromise, historyPromise]);

Copilot · 2026-02-12T19:31:27Z

src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts

+	public async createSession({ model, workingDirectory, isolationEnabled, agent }: { model?: string; workingDirectory?: Uri; isolationEnabled?: boolean; agent?: SweCustomAgent }, token: CancellationToken): Promise<NewSdkRefCountedSession> {
+		const client = await raceCancellationError(this.copilotClientManager.getClient(), token);
+		const { config, toolCalls, sessionOptions } = await this._buildSessionConfig({ model, workingDirectory, isolationEnabled, token });
+
+		const sdkSession = await client.createSession(config);
+		this.logService.trace(`[NewSdkSessionService] Created new CopilotCLI session ${sdkSession.sessionId}.`);
+
+		return this._wrapSdkSession(sdkSession, sessionOptions, model, toolCalls);
+	}
+
+	public async getSession(sessionId: string, { model, workingDirectory, isolationEnabled, readonly: _readonly, agent }: { model?: string; workingDirectory?: Uri; isolationEnabled?: boolean; readonly: boolean; agent?: SweCustomAgent }, token: CancellationToken): Promise<NewSdkRefCountedSession | undefined> {
+		const lock = this.sessionMutexForGetSession.get(sessionId) ?? new Mutex();
+		this.sessionMutexForGetSession.set(sessionId, lock);
+		const lockDisposable = await lock.acquire(token);
+		if (!lockDisposable || this._store.isDisposed || token.isCancellationRequested) {
+			lockDisposable?.dispose();
+			return;
+		}
+
+		try {
+			const existing = this._sessionWrappers.get(sessionId);
+			if (existing) {
+				this.logService.trace(`[NewSdkSessionService] Reusing CopilotCLI session ${sessionId}.`);
+				existing.acquire();
+				return existing;
+			}
+
+			const client = await raceCancellationError(this.copilotClientManager.getClient(), token);
+			const { config, toolCalls, sessionOptions } = await this._buildSessionConfig({ model, workingDirectory, isolationEnabled, token });
+
+			const sdkSession = await client.resumeSession(sessionId, config);
+			return this._wrapSdkSession(sdkSession, sessionOptions, model, toolCalls);
+		} finally {


agent is accepted in createSession/getSession but never used when building the new SDK SessionConfig. This means selecting a custom agent in the UI (passed via agent) won’t affect the session when the new SDK flag is enabled. Please wire agent into the new SDK configuration/selection mechanism (equivalent to old SDK’s selectedCustomAgent / selectCustomAgent) so behavior matches the existing implementation.

Copilot · 2026-02-12T19:31:28Z

src/extension/agents/copilotcli/node/sdk/copilotcliSession.ts

+	/**
+	 * Note: The new SDK does not support emitting synthetic events on the session.
+	 * This is a no-op. If delegation context is needed, use SessionConfig.systemMessage instead.
+	 */
+	addUserMessage(_content: string): void {
+		this.logService.trace('[NewSdkCopilotCLISession] addUserMessage is not supported by the new SDK — using no-op');
+	}
+
+	/**
+	 * Note: The new SDK does not support emitting synthetic events on the session.
+	 * This is a no-op. If delegation context is needed, use SessionConfig.systemMessage instead.
+	 */
+	addUserAssistantMessage(_content: string): void {
+		this.logService.trace('[NewSdkCopilotCLISession] addUserAssistantMessage is not supported by the new SDK — using no-op');
+	}


addUserMessage / addUserAssistantMessage are no-ops in the new SDK wrapper, but existing features (e.g. delegation to cloud via recordPushToSession) rely on these synthetic messages being added so they appear in session history. If the new SDK can’t emit events, consider maintaining a local synthetic history (merged in getChatHistory) or another mechanism so delegation metadata and other synthetic turns aren’t lost when the new SDK is enabled.

Copilot · 2026-02-12T19:31:28Z

src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts

+export class NewSdkCopilotCLISessionService extends Disposable implements ICopilotCLISessionService {
+	declare _serviceBrand: undefined;
+
+	private _sessionWrappers = new DisposableMap<string, NewSdkRefCountedSession>();
+
+	private readonly _onDidChangeSessions = new Emitter<void>();
+	public readonly onDidChangeSessions = this._onDidChangeSessions.event;


This PR introduces a full new SDK-backed session/model stack (new files under node/sdk/) but there are no unit tests covering the new path (e.g., tool-call tracking for permission requests, agent selection, listSessions mapping). There are already unit tests for the old CopilotCLISessionService; adding analogous tests for the new services would help prevent regressions behind the feature flag.

Copilot · 2026-02-12T19:31:28Z

package.json

 		"@github/copilot": "^0.0.406",
+		"@github/copilot-sdk": "^0.1.22",
 		"@google/genai": "^1.22.0",


Adding @github/copilot-sdk introduces its own dependency on @github/copilot (package-lock shows @github/copilot-sdk/node_modules/@github/copilot@0.0.403) while this repo depends on @github/copilot@^0.0.406. This can lead to duplicated CLI binaries and potentially different runtime behavior between old vs new SDK paths. Consider aligning the @github/copilot version via an overrides entry (or upgrading the SDK) so both stacks use the same Copilot CLI version.

Copilot · 2026-02-12T19:31:28Z

src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts

+		// We'd need to resume the session or track working directories ourselves.
+		// For now return undefined — the delegating service can fall back to the old SDK path.


This comment says the delegating service can “fall back to the old SDK path”, but DelegatingCopilotCLISessionService chooses old vs new SDK once and then forwards calls to that implementation only. Either update the comment to reflect the current behavior, or implement an explicit fallback strategy when the new SDK can’t provide the working directory.

Suggested change

// We'd need to resume the session or track working directories ourselves.

// For now return undefined — the delegating service can fall back to the old SDK path.

// We'd need to resume the session or track working directories ourselves to reconstruct it.

// For now, this implementation does not provide a working directory and always returns undefined.

src/extension/agents/copilotcli/node/sdk/copilotcliSessionService.ts

DonJayamanne requested a review from Copilot February 9, 2026 06:53

Copilot started reviewing on behalf of DonJayamanne February 9, 2026 06:53 View session

Copilot AI reviewed Feb 9, 2026

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DonJayamanne closed this Feb 12, 2026

DonJayamanne force-pushed the don/technological-amphibian branch from bcc899d to 9ed39d6 Compare February 12, 2026 18:29

Adopt the new Github Copilot SDK

d28e2b6

DonJayamanne reopened this Feb 12, 2026

DonJayamanne requested a review from Copilot February 12, 2026 19:23

Copilot started reviewing on behalf of DonJayamanne February 12, 2026 19:23 View session

Copilot AI reviewed Feb 12, 2026

View reviewed changes

Updates

24f405b

	toolCalls.set(event.id, event.data as unknown as ToolCall);
	const toolCallId = (event as { data: { toolCallId?: string } }).data.toolCallId ?? event.id;
	toolCalls.set(toolCallId, event.data as unknown as ToolCall);

	"github.copilot.config.cli.sdk.enabled": "Enable the new SDK for Background Agents.",
	"github.copilot.config.cli.sdk.enabled": "Enable the new SDK for Background Agents. Requires VS Code reload.",

-		const [model, history] = await Promise.all([
-			(existingSession ? (_sessionModel.get(copilotcliSessionId) ?? await existingSession.object.getSelectedModelId()) : _sessionModel.get(copilotcliSessionId)) ?? await this.getCustomAgentModel(defaultAgent, token) ?? defaultModel,
-			existingSession?.object?.getChatHistory() || []
-		]);
+		const modelPromise = (async () => {
+			return (existingSession ? (_sessionModel.get(copilotcliSessionId) ?? await existingSession.object.getSelectedModelId()) : _sessionModel.get(copilotcliSessionId)) ?? await this.getCustomAgentModel(defaultAgent, token) ?? defaultModel;
+		})();
+		const historyPromise = existingSession?.object?.getChatHistory() ?? Promise.resolve([]);
+		const [model, history] = await Promise.all([modelPromise, historyPromise]);

		// We'd need to resume the session or track working directories ourselves.
		// For now return undefined — the delegating service can fall back to the old SDK path.

feat: Introduce new SDK support for Copilot CLI sessions and models #3577

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feat: Introduce new SDK support for Copilot CLI sessions and models #3577

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