fix: preserve selected model during AI-initiated mode switches

When the AI agent uses the switch_mode tool, the user's selected model
should not change. Previously, handleModeSwitch would load mode-specific
API configurations even for AI-initiated switches, unexpectedly changing
the model mid-task.

This adds a preserveApiConfig option to handleModeSwitch and passes it
from SwitchModeTool so the current API config is preserved. User-initiated
mode switches from the UI continue to load per-mode configs as before.

Closes #12237

Author: roomote

src/core/tools/SwitchModeTool.ts

@@ -55,8 +55,9 @@ export class SwitchModeTool extends BaseTool<"switch_mode"> {
 				return
 			}
 
-			// Switch the mode using shared handler
-			await task.providerRef.deref()?.handleModeSwitch(mode_slug)
+			// Switch the mode using shared handler, preserving the current API config
+			// so the user's selected model doesn't change during AI-initiated switches.
+			await task.providerRef.deref()?.handleModeSwitch(mode_slug, { preserveApiConfig: true })
 
 			pushToolResult(
 				`Successfully switched from ${getModeBySlug(currentMode)?.name ?? currentMode} mode to ${

src/core/webview/ClineProvider.ts

@@ -1391,7 +1391,7 @@ export class ClineProvider
 	 * Handle switching to a new mode, including updating the associated API configuration
 	 * @param newMode The mode to switch to
 	 */
-	public async handleModeSwitch(newMode: Mode) {
+	public async handleModeSwitch(newMode: Mode, options?: { preserveApiConfig?: boolean }) {
 		const task = this.getCurrentTask()
 
 		if (task) {
@@ -1426,9 +1426,11 @@ export class ClineProvider
 
 		this.emit(RooCodeEventName.ModeChanged, newMode)
 
-		// If workspace lock is on, keep the current API config — don't load mode-specific config
+		// If workspace lock is on, or the caller explicitly requested preserving the current
+		// API config (e.g. AI-initiated mode switches via the switch_mode tool), keep the
+		// current API config — don't load mode-specific config.
 		const lockApiConfigAcrossModes = this.context.workspaceState.get("lockApiConfigAcrossModes", false)
-		if (lockApiConfigAcrossModes) {
+		if (lockApiConfigAcrossModes || options?.preserveApiConfig) {
 			await this.postStateToWebview()
 			return
 		}

src/core/webview/__tests__/ClineProvider.lockApiConfig.spec.ts

@@ -342,6 +342,28 @@ describe("ClineProvider - Lock API Config Across Modes", () => {
 			expect(activateProviderProfileSpy).not.toHaveBeenCalled()
 		})
 
+		it("skips mode-specific config lookup/load when preserveApiConfig option is true", async () => {
+			await mockContext.workspaceState.update("lockApiConfigAcrossModes", false)
+
+			const getModeConfigIdSpy = vi
+				.spyOn(provider.providerSettingsManager, "getModeConfigId")
+				.mockResolvedValue("architect-profile-id")
+			const listConfigSpy = vi
+				.spyOn(provider.providerSettingsManager, "listConfig")
+				.mockResolvedValue([
+					{ name: "architect-profile", id: "architect-profile-id", apiProvider: "anthropic" },
+				])
+			const activateProviderProfileSpy = vi
+				.spyOn(provider, "activateProviderProfile")
+				.mockResolvedValue(undefined)
+
+			await provider.handleModeSwitch("architect", { preserveApiConfig: true })
+
+			expect(getModeConfigIdSpy).not.toHaveBeenCalled()
+			expect(listConfigSpy).not.toHaveBeenCalled()
+			expect(activateProviderProfileSpy).not.toHaveBeenCalled()
+		})
+
 		it("keeps normal mode-specific lookup/load behavior when lockApiConfigAcrossModes is false", async () => {
 			await mockContext.workspaceState.update("lockApiConfigAcrossModes", false)