fix: use max_completion_tokens for Azure reasoning models

Author: qiosun

packages/opencode/src/provider/provider.ts

@@ -791,6 +791,26 @@ export namespace Provider {
           opts.signal = combined
         }
 
+        // Reasoning models require max_completion_tokens instead of max_tokens
+        // when using openai-compatible provider
+        // Check if model has reasoning capability OR has reasoningEffort option
+        const isReasoningModel =
+          model.capabilities.reasoning || (model.options && "reasoningEffort" in model.options)
+        if (model.api.npm === "@ai-sdk/azure" && isReasoningModel) {
+          if (opts.body && typeof opts.body === "string") {
+            try {
+              const body = JSON.parse(opts.body)
+              if (body.max_tokens !== undefined) {
+                body.max_completion_tokens = body.max_tokens
+                delete body.max_tokens
+                opts.body = JSON.stringify(body)
+              }
+            } catch (e) {
+              // Ignore JSON parse errors
+            }
+          }
+        }
+
         return fetchFn(input, {
           ...opts,
           // @ts-ignore see here: https://github.com/oven-sh/bun/issues/16682