diff --git a/packages/opencode/src/provider/provider.ts b/packages/opencode/src/provider/provider.ts
index b11ca9368..77a02b861 100644
--- a/packages/opencode/src/provider/provider.ts
+++ b/packages/opencode/src/provider/provider.ts
@@ -815,6 +815,29 @@ export namespace Provider {
           opts.signal = combined
         }
 
+        // Reasoning models require max_completion_tokens instead of max_tokens
+        // when using openai-compatible or azure provider
+        const isOpenAICompatible =
+          model.api.npm === "@ai-sdk/openai-compatible" || model.api.npm === "@ai-sdk/azure"
+        if (isOpenAICompatible && model.capabilities.reasoning) {
+          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) {
+              log.warn("Failed to transform max_tokens parameter for reasoning model", {
+                providerID: model.providerID,
+                modelID: model.id,
+                error: e,
+              })
+            }
+          }
+        }
+
         return fetchFn(input, {
           ...opts,
           // @ts-ignore see here: https://github.com/oven-sh/bun/issues/16682