feat(copilotcli): Add auto model configuration

[DonJayamanne]

Co-authored-by: Copilot copilot@github.com

Fixes #311779

[Copilot]

Pull request overview

This PR adds “auto” model support for Copilot CLI and introduces a user setting to enable/disable exposing that option through the language model provider, addressing #311779.

Changes:

• Add github.copilot.chat.cli.autoModel.enabled setting (default: true) and wire it into Copilot CLI model resolution/model listing.
• Update CopilotCLIModels to cache resolved LanguageModelChatInformation and prepend an auto entry when enabled.
• Expand vitest coverage around model resolution and provideLanguageModelChatInformation behaviors (auth/no-auth, pending fetch, auth changes, setting toggle).

Show a summary per file

File	Description
extensions/copilot/src/platform/configuration/common/configurationService.ts	Adds a new advanced config key for enabling/disabling the auto model option in Copilot CLI.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts	Implements the auto model entry, caches resolved model infos, and applies the new setting in the LM provider surface.
extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotCliModels.spec.ts	Adds/updates tests for auto model resolution, provider behaviors, and the new config setting.
extensions/copilot/package.nls.json	Adds localized description string for the new setting.
extensions/copilot/package.json	Exposes the new setting in the extension’s configuration contribution.

Copilot's findings

Comments suppressed due to low confidence (3)

extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts:106

• resolveModel short-circuits auto by returning the original input string (preserving casing/whitespace). Callers (e.g. prompt-file model resolution) expect a canonical model id; returning Auto/AUTO can leak through to SDK selection and fail if the SDK expects auto. Trim/lowercase first, and return the canonical 'auto' id when enabled.

	async resolveModel(modelId: string): Promise<string | undefined> {
		if (modelId.toLowerCase() === 'auto' && this.configurationService.getConfig(ConfigKey.Advanced.CLIAutoModelEnabled)) {
			return modelId;
		}
		const models = await this.getModels();
		modelId = modelId.trim().toLowerCase();
		return models.find(m => m.id.toLowerCase() === modelId || m.name.toLowerCase() === modelId)?.id;

extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts:167

• provideLanguageModelChatInformation returns _resolvedModelInfos as-is once fetched, so toggling chat.cli.autoModel.enabled at runtime won’t take effect (auto may remain present/absent until an auth change). Consider filtering/prepending auto on each call based on the current setting, or listen for configuration changes to rebuild _resolvedModelInfos and fire _onDidChange.

			provideLanguageModelChatInformation: async (_options, _token) => {
				const autoModelEnabled = this.configurationService.getConfig(ConfigKey.Advanced.CLIAutoModelEnabled);
				if (!this._authenticationService.anyGitHubSession || !this._resolvedModelInfos) {
					return autoModelEnabled ? [buildAutoModel()] : [];
				}
				return this._resolvedModelInfos;
			},

extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts:206

• When chat.cli.autoModel.enabled is disabled, _buildModelInfos no longer marks any SDK model as default (isDefault is omitted for all non-auto models). This can result in no default model being surfaced to the language model service. Preserve the previous behavior by marking the first SDK model as default when auto is disabled (and ensure only one model is default at a time).

	private _buildModelInfos(models: CopilotCLIModelInfo[]): vscode.LanguageModelChatInformation[] {
		const isReasoningEffortEnabled = this.configurationService.getConfig(ConfigKey.Advanced.CLIThinkingEffortEnabled);
		const isAutoModelEnabled = this.configurationService.getConfig(ConfigKey.Advanced.CLIAutoModelEnabled);
		const modelsInfo: vscode.LanguageModelChatInformation[] = models.map((model, index) => {
			const multiplier = model.multiplier === undefined ? undefined : `${model.multiplier}x`;
			return {
				id: model.id,
				name: model.name,
				family: model.id,
				version: '',
				maxInputTokens: model.maxInputTokens ?? model.maxContextWindowTokens,
				maxOutputTokens: model.maxOutputTokens ?? 0,
				multiplier,
				multiplierNumeric: model.multiplier,
				isUserSelectable: true,
				configurationSchema: isReasoningEffortEnabled ? buildConfigurationSchema(model) : undefined,
				capabilities: {
					imageInput: model.supportsVision,
					toolCalling: true
				},
				targetChatSessionType: 'copilotcli'
			};
		});
		if (isAutoModelEnabled) {
			modelsInfo.unshift(buildAutoModel(models[0]));
		}
		return modelsInfo;

• Files reviewed: 5/5 changed files
• Comments generated: 2

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Screenshot Changes

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