fix: support thinking.type "adaptive" for latest Claude Code

Claude Code now sends thinking.type: "adaptive" (with optional
budget_tokens) instead of always "enabled"/"disabled". Added the
new variant to the Zod schema and translation logic.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/translation/anthropic-to-codex.ts

@@ -19,6 +19,10 @@ function mapThinkingToEffort(
   thinking: AnthropicMessagesRequest["thinking"],
 ): string | undefined {
   if (!thinking || thinking.type === "disabled") return undefined;
+  if (thinking.type === "adaptive") {
+    // adaptive: use budget_tokens if provided, otherwise let Codex decide
+    return thinking.budget_tokens ? budgetToEffort(thinking.budget_tokens) : undefined;
+  }
   return budgetToEffort(thinking.budget_tokens);
 }
 

src/types/anthropic.ts

@@ -59,6 +59,11 @@ const AnthropicThinkingDisabledSchema = z.object({
   type: z.literal("disabled"),
 });
 
+const AnthropicThinkingAdaptiveSchema = z.object({
+  type: z.literal("adaptive"),
+  budget_tokens: z.number().int().positive().optional(),
+});
+
 export const AnthropicMessagesRequestSchema = z.object({
   model: z.string(),
   max_tokens: z.number().int().positive(),
@@ -77,7 +82,11 @@ export const AnthropicMessagesRequestSchema = z.object({
     })
     .optional(),
   thinking: z
-    .union([AnthropicThinkingEnabledSchema, AnthropicThinkingDisabledSchema])
+    .union([
+      AnthropicThinkingEnabledSchema,
+      AnthropicThinkingDisabledSchema,
+      AnthropicThinkingAdaptiveSchema,
+    ])
     .optional(),
   // Tool-related fields (accepted for compatibility, not forwarded to Codex)
   tools: z.array(z.object({