feat: add xhigh thinking level support for gpt-5.2 and gpt-5.2-codex

- Add XHIGH_MODELS constant and getAvailableThinkingLevels() to AgentSession
- Update ThinkingSelectorComponent to accept availableLevels parameter
- Both shift+tab cycling and /thinking command now show xhigh for supported models
- Update types.ts documentation to list supported models

packages/agent/src/types.ts

@@ -25,7 +25,7 @@ export interface Attachment {
 
 /**
  * Thinking/reasoning level for models that support it.
- * Note: "xhigh" is only supported by OpenAI codex-max models.
+ * Note: "xhigh" is only supported by OpenAI gpt-5.1-codex-max, gpt-5.2, and gpt-5.2-codex models.
  */
 export type ThinkingLevel = "off" | "minimal" | "low" | "medium" | "high" | "xhigh";
 

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

@@ -98,6 +98,19 @@ export interface SessionStats {
 	cost: number;
 }
 
+// ============================================================================
+// Constants
+// ============================================================================
+
+/** Models that support xhigh thinking level */
+const XHIGH_MODELS = ["gpt-5.1-codex-max", "gpt-5.2", "gpt-5.2-codex"];
+
+/** Standard thinking levels */
+const THINKING_LEVELS: ThinkingLevel[] = ["off", "minimal", "low", "medium", "high"];
+
+/** Thinking levels including xhigh (for supported models) */
+const THINKING_LEVELS_WITH_XHIGH: ThinkingLevel[] = ["off", "minimal", "low", "medium", "high", "xhigh"];
+
 // ============================================================================
 // AgentSession Class
 // ============================================================================
@@ -637,12 +650,7 @@ export class AgentSession {
 	cycleThinkingLevel(): ThinkingLevel | null {
 		if (!this.supportsThinking()) return null;
 
-		const modelId = this.model?.id || "";
+		const levels = this.getAvailableThinkingLevels();
-		const supportsXhigh = modelId.includes("codex-max");
-		const levels: ThinkingLevel[] = supportsXhigh
-			? ["off", "minimal", "low", "medium", "high", "xhigh"]
-			: ["off", "minimal", "low", "medium", "high"];
-
 		const currentIndex = levels.indexOf(this.thinkingLevel);
 		const nextIndex = (currentIndex + 1) % levels.length;
 		const nextLevel = levels[nextIndex];
@@ -651,6 +659,21 @@ export class AgentSession {
 		return nextLevel;
 	}
 
+	/**
+	 * Get available thinking levels for current model.
+	 */
+	getAvailableThinkingLevels(): ThinkingLevel[] {
+		return this.supportsXhighThinking() ? THINKING_LEVELS_WITH_XHIGH : THINKING_LEVELS;
+	}
+
+	/**
+	 * Check if current model supports xhigh thinking level.
+	 */
+	supportsXhighThinking(): boolean {
+		const modelId = this.model?.id || "";
+		return XHIGH_MODELS.some((m) => modelId === m || modelId.endsWith(`/${m}`));
+	}
+
 	/**
 	 * Check if current model supports thinking/reasoning.
 	 */

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

@@ -3,28 +3,40 @@ import { Container, type SelectItem, SelectList } from "@mariozechner/pi-tui";
 import { getSelectListTheme } from "../theme/theme.js";
 import { DynamicBorder } from "./dynamic-border.js";
 
+const LEVEL_DESCRIPTIONS: Record<ThinkingLevel, string> = {
+	off: "No reasoning",
+	minimal: "Very brief reasoning (~1k tokens)",
+	low: "Light reasoning (~2k tokens)",
+	medium: "Moderate reasoning (~8k tokens)",
+	high: "Deep reasoning (~16k tokens)",
+	xhigh: "Maximum reasoning (~32k tokens)",
+};
+
 /**
  * Component that renders a thinking level selector with borders
  */
 export class ThinkingSelectorComponent extends Container {
 	private selectList: SelectList;
 
-	constructor(currentLevel: ThinkingLevel, onSelect: (level: ThinkingLevel) => void, onCancel: () => void) {
+	constructor(
+		currentLevel: ThinkingLevel,
+		availableLevels: ThinkingLevel[],
+		onSelect: (level: ThinkingLevel) => void,
+		onCancel: () => void,
+	) {
 		super();
 
-		const thinkingLevels: SelectItem[] = [
+		const thinkingLevels: SelectItem[] = availableLevels.map((level) => ({
-			{ value: "off", label: "off", description: "No reasoning" },
+			value: level,
-			{ value: "minimal", label: "minimal", description: "Very brief reasoning (~1k tokens)" },
+			label: level,
-			{ value: "low", label: "low", description: "Light reasoning (~2k tokens)" },
+			description: LEVEL_DESCRIPTIONS[level],
-			{ value: "medium", label: "medium", description: "Moderate reasoning (~8k tokens)" },
+		}));
-			{ value: "high", label: "high", description: "Deep reasoning (~16k tokens)" },
-		];
 
 		// Add top border
 		this.addChild(new DynamicBorder());
 
 		// Create selector
-		this.selectList = new SelectList(thinkingLevels, 5, getSelectListTheme());
+		this.selectList = new SelectList(thinkingLevels, thinkingLevels.length, getSelectListTheme());
 
 		// Preselect current level
 		const currentIndex = thinkingLevels.findIndex((item) => item.value === currentLevel);

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

@@ -1301,6 +1301,7 @@ export class InteractiveMode {
 		this.showSelector((done) => {
 			const selector = new ThinkingSelectorComponent(
 				this.session.thinkingLevel,
+				this.session.getAvailableThinkingLevels(),
 				(level) => {
 					this.session.setThinkingLevel(level);
 					this.updateEditorBorderColor();