feat: add xhigh thinking level support for gpt-5.2 models

- Add supportsXhigh() function to ai package for checking xhigh support
- Clamp xhigh to high for OpenAI models that don't support it
- Update coding-agent to use centralized supportsXhigh()
- gpt-5.2, gpt-5.2-codex now show xhigh in thinking selector

Closes #236

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- **xhigh thinking level support**: Added `supportsXhigh()` function to check if a model supports xhigh reasoning level. Also clamps xhigh to high for OpenAI models that don't support it. ([#236](https://github.com/badlogic/pi-mono/pull/236) by [@theBucky](https://github.com/theBucky))
+
 ## [0.23.5] - 2025-12-19
 
 ### Added

packages/ai/src/models.ts

@@ -43,3 +43,14 @@ export function calculateCost<TApi extends Api>(model: Model<TApi>, usage: Usage
 	usage.cost.total = usage.cost.input + usage.cost.output + usage.cost.cacheRead + usage.cost.cacheWrite;
 	return usage.cost;
 }
+
+/** Models that support xhigh thinking level */
+const XHIGH_MODELS = new Set(["gpt-5.1-codex-max", "gpt-5.2", "gpt-5.2-codex"]);
+
+/**
+ * Check if a model supports xhigh thinking level.
+ * Currently only certain OpenAI models support this.
+ */
+export function supportsXhigh<TApi extends Api>(model: Model<TApi>): boolean {
+	return XHIGH_MODELS.has(model.id);
+}

packages/ai/src/stream.ts

@@ -1,4 +1,5 @@
 import { ThinkingLevel } from "@google/genai";
+import { supportsXhigh } from "./models.js";
 import { type AnthropicOptions, streamAnthropic } from "./providers/anthropic.js";
 import { type GoogleOptions, streamGoogle } from "./providers/google.js";
 import { type OpenAICompletionsOptions, streamOpenAICompletions } from "./providers/openai-completions.js";
@@ -155,13 +156,13 @@ function mapOptionsForApi<TApi extends Api>(
 		case "openai-completions":
 			return {
 				...base,
-				reasoningEffort: options?.reasoning,
+				reasoningEffort: supportsXhigh(model) ? options?.reasoning : clampReasoning(options?.reasoning),
 			} satisfies OpenAICompletionsOptions;
 
 		case "openai-responses":
 			return {
 				...base,
-				reasoningEffort: options?.reasoning,
+				reasoningEffort: supportsXhigh(model) ? options?.reasoning : clampReasoning(options?.reasoning),
 			} satisfies OpenAIResponsesOptions;
 
 		case "google-generative-ai": {

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- **xhigh thinking level for gpt-5.2 models**: The thinking level selector and shift+tab cycling now show xhigh option for gpt-5.2 and gpt-5.2-codex models (in addition to gpt-5.1-codex-max). ([#236](https://github.com/badlogic/pi-mono/pull/236) by [@theBucky](https://github.com/theBucky))
+
 ### Fixed
 
 - **Hooks wrap custom tools**: Custom tools are now executed through the hook wrapper, so `tool_call`/`tool_result` hooks can observe, block, and modify custom tool executions (consistent with hook type docs).

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

@@ -15,7 +15,7 @@
 
 import type { Agent, AgentEvent, AgentState, AppMessage, Attachment, ThinkingLevel } from "@mariozechner/pi-agent-core";
 import type { AssistantMessage, Message, Model, TextContent } from "@mariozechner/pi-ai";
-import { isContextOverflow } from "@mariozechner/pi-ai";
+import { isContextOverflow, supportsXhigh } from "@mariozechner/pi-ai";
 import { getModelsPath } from "../config.js";
 import { type BashResult, executeBash as executeBashCommand } from "./bash-executor.js";
 import { calculateContextTokens, compact, shouldCompact } from "./compaction.js";
@@ -102,9 +102,6 @@ export interface SessionStats {
 // 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"];
 
@@ -670,8 +667,7 @@ export class AgentSession {
 	 * 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}`));
+		return this.model ? supportsXhigh(this.model) : false;
 	}
 
 	/**