Fix z.ai thinking/reasoning params, fixes #688

Z.ai uses thinking: { type: "enabled" | "disabled" } instead of
OpenAI's reasoning_effort. Added thinkingFormat compat flag to handle
this. Thinking is now explicitly enabled/disabled based on user setting.

packages/ai/CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Added Vercel AI Gateway provider with model discovery and `AI_GATEWAY_API_KEY` env support ([#689](https://github.com/badlogic/pi-mono/pull/689) by [@timolins](https://github.com/timolins))
 
+### Fixed
+
+- Fixed z.ai thinking/reasoning: z.ai uses `thinking: { type: "enabled" }` instead of OpenAI's `reasoning_effort`. Added `thinkingFormat` compat flag to handle this. ([#688](https://github.com/badlogic/pi-mono/issues/688))
+
 ## [0.45.3] - 2026-01-13
 
 ## [0.45.2] - 2026-01-13

packages/ai/README.md

@@ -711,6 +711,7 @@ interface OpenAICompat {
   supportsDeveloperRole?: boolean;   // Whether provider supports `developer` role vs `system` (default: true)
   supportsReasoningEffort?: boolean; // Whether provider supports `reasoning_effort` (default: true)
   maxTokensField?: 'max_completion_tokens' | 'max_tokens';  // Which field name to use (default: max_completion_tokens)
+  thinkingFormat?: 'openai' | 'zai'; // Format for reasoning param: 'openai' uses reasoning_effort, 'zai' uses thinking: { type: "enabled" } (default: openai)
 }
 ```
 

packages/ai/scripts/generate-models.ts

@@ -440,6 +440,7 @@ async function loadModelsDevData(): Promise<Model<any>[]> {
 				},
 				compat: {
 					supportsDeveloperRole: false,
+					thinkingFormat: "zai",
 				},
 				contextWindow: m.limit?.context || 4096,
 				maxTokens: m.limit?.output || 4096,

packages/ai/src/models.generated.ts

@@ -10733,7 +10733,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text"],
 			cost: {
@@ -10751,7 +10751,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text"],
 			cost: {
@@ -10769,7 +10769,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text"],
 			cost: {
@@ -10787,7 +10787,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text", "image"],
 			cost: {
@@ -10805,7 +10805,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text"],
 			cost: {
@@ -10823,7 +10823,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text", "image"],
 			cost: {
@@ -10841,7 +10841,7 @@ export const MODELS = {
 			api: "openai-completions",
 			provider: "zai",
 			baseUrl: "https://api.z.ai/api/coding/paas/v4",
-			compat: {"supportsDeveloperRole":false},
+			compat: {"supportsDeveloperRole":false,"thinkingFormat":"zai"},
 			reasoning: true,
 			input: ["text"],
 			cost: {

packages/ai/src/providers/openai-completions.ts

@@ -404,7 +404,12 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 		params.tool_choice = options.toolChoice;
 	}
 
-	if (options?.reasoningEffort && model.reasoning && compat.supportsReasoningEffort) {
+	if (compat.thinkingFormat === "zai" && model.reasoning) {
+		// Z.ai uses binary thinking: { type: "enabled" | "disabled" }
+		// Must explicitly disable since z.ai defaults to thinking enabled
+		(params as any).thinking = { type: options?.reasoningEffort ? "enabled" : "disabled" };
+	} else if (options?.reasoningEffort && model.reasoning && compat.supportsReasoningEffort) {
+		// OpenAI-style reasoning_effort
 		params.reasoning_effort = options.reasoningEffort;
 	}
 
@@ -678,11 +683,14 @@ function mapStopReason(reason: ChatCompletionChunk.Choice["finish_reason"]): Sto
  * Returns a fully resolved OpenAICompat object with all fields set.
  */
 function detectCompatFromUrl(baseUrl: string): Required<OpenAICompat> {
+	const isZai = baseUrl.includes("api.z.ai");
+
 	const isNonStandard =
 		baseUrl.includes("cerebras.ai") ||
 		baseUrl.includes("api.x.ai") ||
 		baseUrl.includes("mistral.ai") ||
-		baseUrl.includes("chutes.ai");
+		baseUrl.includes("chutes.ai") ||
+		isZai;
 
 	const useMaxTokens = baseUrl.includes("mistral.ai") || baseUrl.includes("chutes.ai");
 
@@ -693,13 +701,14 @@ function detectCompatFromUrl(baseUrl: string): Required<OpenAICompat> {
 	return {
 		supportsStore: !isNonStandard,
 		supportsDeveloperRole: !isNonStandard,
-		supportsReasoningEffort: !isGrok,
+		supportsReasoningEffort: !isGrok && !isZai,
 		supportsUsageInStreaming: true,
 		maxTokensField: useMaxTokens ? "max_tokens" : "max_completion_tokens",
 		requiresToolResultName: isMistral,
 		requiresAssistantAfterToolResult: false, // Mistral no longer requires this as of Dec 2024
 		requiresThinkingAsText: isMistral,
 		requiresMistralToolIds: isMistral,
+		thinkingFormat: isZai ? "zai" : "openai",
 	};
 }
 
@@ -722,5 +731,6 @@ function getCompat(model: Model<"openai-completions">): Required<OpenAICompat> {
 			model.compat.requiresAssistantAfterToolResult ?? detected.requiresAssistantAfterToolResult,
 		requiresThinkingAsText: model.compat.requiresThinkingAsText ?? detected.requiresThinkingAsText,
 		requiresMistralToolIds: model.compat.requiresMistralToolIds ?? detected.requiresMistralToolIds,
+		thinkingFormat: model.compat.thinkingFormat ?? detected.thinkingFormat,
 	};
 }

packages/ai/src/types.ts

@@ -225,6 +225,8 @@ export interface OpenAICompat {
 	requiresThinkingAsText?: boolean;
 	/** Whether tool call IDs must be normalized to Mistral format (exactly 9 alphanumeric chars). Default: auto-detected from URL. */
 	requiresMistralToolIds?: boolean;
+	/** Format for reasoning/thinking parameter. "openai" uses reasoning_effort, "zai" uses thinking: { type: "enabled" }. Default: "openai". */
+	thinkingFormat?: "openai" | "zai";
 }
 
 // Model interface for the unified model system

packages/coding-agent/CHANGELOG.md

@@ -14,6 +14,7 @@
 ### Fixed
 
 - Fix API key resolution after model switches by using provider argument ([#691](https://github.com/badlogic/pi-mono/pull/691) by [@joshp123](https://github.com/joshp123))
+- Fixed z.ai thinking/reasoning: thinking toggle now correctly enables/disables thinking for z.ai models ([#688](https://github.com/badlogic/pi-mono/issues/688))
 
 ## [0.45.3] - 2026-01-13