fix(coding-agent): preserve session thinking for scoped model cycling

closes #1789

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Breaking Changes
+
+- Changed scoped model thinking semantics. Scoped entries without an explicit `:<thinking>` suffix now inherit the current session thinking level when selected, instead of applying a startup-captured default.
+
 ### Fixed
 
 - Fixed IME hardware cursor positioning in the custom extension editor (`ctx.ui.editor()` / extension editor dialog) by propagating focus to the internal `Editor`, preventing the terminal cursor from getting stuck at the bottom-right during composition.

packages/coding-agent/src/core/agent-session.ts

@@ -135,7 +135,7 @@ export interface AgentSessionConfig {
 	settingsManager: SettingsManager;
 	cwd: string;
 	/** Models to cycle through with Ctrl+P (from --models flag) */
-	scopedModels?: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }>;
+	scopedModels?: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>;
 	/** Resource loader for skills, prompts, themes, context files, system prompt */
 	resourceLoader: ResourceLoader;
 	/** SDK custom tools registered outside extensions */
@@ -215,7 +215,7 @@ export class AgentSession {
 	readonly sessionManager: SessionManager;
 	readonly settingsManager: SettingsManager;
 
-	private _scopedModels: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }>;
+	private _scopedModels: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>;
 
 	// Event subscription state
 	private _unsubscribeAgent?: () => void;
@@ -717,12 +717,12 @@ export class AgentSession {
 	}
 
 	/** Scoped models for cycling (from --models flag) */
-	get scopedModels(): ReadonlyArray<{ model: Model<any>; thinkingLevel: ThinkingLevel }> {
+	get scopedModels(): ReadonlyArray<{ model: Model<any>; thinkingLevel?: ThinkingLevel }> {
 		return this._scopedModels;
 	}
 
 	/** Update scoped models for cycling */
-	setScopedModels(scopedModels: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }>): void {
+	setScopedModels(scopedModels: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>): void {
 		this._scopedModels = scopedModels;
 	}
 
@@ -1338,9 +1338,9 @@ export class AgentSession {
 		return this._cycleAvailableModel(direction);
 	}
 
-	private async _getScopedModelsWithApiKey(): Promise<Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }>> {
+	private async _getScopedModelsWithApiKey(): Promise<Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>> {
 		const apiKeysByProvider = new Map<string, string | undefined>();
-		const result: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }> = [];
+		const result: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }> = [];
 
 		for (const scoped of this._scopedModels) {
 			const provider = scoped.model.provider;
@@ -1377,8 +1377,11 @@ export class AgentSession {
 		this.sessionManager.appendModelChange(next.model.provider, next.model.id);
 		this.settingsManager.setDefaultModelAndProvider(next.model.provider, next.model.id);
 
-		// Apply thinking level (setThinkingLevel clamps to model capabilities)
+		// Apply thinking level.
-		this.setThinkingLevel(next.thinkingLevel);
+		// - Explicit scoped model thinking level overrides current session level
+		// - Undefined scoped model thinking level inherits current session level
+		// setThinkingLevel clamps to model capabilities.
+		this.setThinkingLevel(next.thinkingLevel ?? this.thinkingLevel);
 
 		await this._emitModelSelect(next.model, currentModel, "cycle");
 

packages/coding-agent/src/core/sdk.ts

@@ -54,7 +54,7 @@ export interface CreateAgentSessionOptions {
 	/** Thinking level. Default: from settings, else 'medium' (clamped to model capabilities) */
 	thinkingLevel?: ThinkingLevel;
 	/** Models available for cycling (Ctrl+P in interactive mode) */
-	scopedModels?: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }>;
+	scopedModels?: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>;
 
 	/** Built-in tools to use. Default: codingTools [read, bash, edit, write] */
 	tools?: Tool[];

packages/coding-agent/src/main.ts

@@ -15,7 +15,6 @@ import { listModels } from "./cli/list-models.js";
 import { selectSession } from "./cli/session-picker.js";
 import { APP_NAME, getAgentDir, getModelsPath, VERSION } from "./config.js";
 import { AuthStorage } from "./core/auth-storage.js";
-import { DEFAULT_THINKING_LEVEL } from "./core/defaults.js";
 import { exportFromFile } from "./core/export-html/index.js";
 import type { LoadExtensionsResult } from "./core/extensions/index.js";
 import { KeybindingsManager } from "./core/keybindings.js";
@@ -488,12 +487,13 @@ function buildSessionOptions(
 		options.thinkingLevel = parsed.thinking;
 	}
 
-	// Scoped models for Ctrl+P cycling - fill in default thinking level for models without explicit level
+	// Scoped models for Ctrl+P cycling
+	// Keep thinking level undefined when not explicitly set in the model pattern.
+	// Undefined means "inherit current session thinking level" during cycling.
 	if (scopedModels.length > 0) {
-		const defaultThinkingLevel = settingsManager.getDefaultThinkingLevel() ?? DEFAULT_THINKING_LEVEL;
 		options.scopedModels = scopedModels.map((sm) => ({
 			model: sm.model,
-			thinkingLevel: sm.thinkingLevel ?? defaultThinkingLevel,
+			thinkingLevel: sm.thinkingLevel,
 		}));
 	}
 

packages/coding-agent/src/modes/interactive/components/model-selector.ts

@@ -23,7 +23,7 @@ interface ModelItem {
 
 interface ScopedModelItem {
 	model: Model<any>;
-	thinkingLevel: string;
+	thinkingLevel?: string;
 }
 
 type ModelScope = "all" | "scoped";

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -3307,13 +3307,11 @@ export class InteractiveMode {
 		// Helper to update session's scoped models (session-only, no persist)
 		const updateSessionModels = async (enabledIds: Set<string>) => {
 			if (enabledIds.size > 0 && enabledIds.size < allModels.length) {
-				// Use current session thinking level, not settings default
-				const currentThinkingLevel = this.session.thinkingLevel;
 				const newScopedModels = await resolveModelScope(Array.from(enabledIds), this.session.modelRegistry);
 				this.session.setScopedModels(
 					newScopedModels.map((sm) => ({
 						model: sm.model,
-						thinkingLevel: sm.thinkingLevel ?? currentThinkingLevel,
+						thinkingLevel: sm.thinkingLevel,
 					})),
 				);
 			} else {