diff --git a/.changeset/cold-onions-refuse.md b/.changeset/cold-onions-refuse.md
new file mode 100644
index 000000000..10c2805cd
--- /dev/null
+++ b/.changeset/cold-onions-refuse.md
@@ -0,0 +1,5 @@
+---
+"@browserbasehq/stagehand": patch
+---
+
+add support for codex models
diff --git a/packages/core/lib/v3/llm/aisdk.ts b/packages/core/lib/v3/llm/aisdk.ts
index a30656b8d..f036d0732 100644
--- a/packages/core/lib/v3/llm/aisdk.ts
+++ b/packages/core/lib/v3/llm/aisdk.ts
@@ -130,9 +130,11 @@ export class AISdkClient extends LLMClient {
 
     let objectResponse: Awaited<ReturnType<typeof generateObject>>;
     const isGPT5 = this.model.modelId.includes("gpt-5");
+    const isCodex = this.model.modelId.includes("codex");
     const usesLowReasoningEffort =
-      this.model.modelId.includes("gpt-5.1") ||
-      this.model.modelId.includes("gpt-5.2");
+      (this.model.modelId.includes("gpt-5.1") ||
+        this.model.modelId.includes("gpt-5.2")) &&
+      !isCodex;
     const isDeepSeek = this.model.modelId.includes("deepseek");
     // Kimi models only support temperature=1
     const isKimi = this.model.modelId.includes("kimi");
@@ -173,8 +175,12 @@ You must respond in JSON format. respond WITH JSON. Do not include any other tex
           providerOptions: isGPT5
             ? {
                 openai: {
-                  textVerbosity: "low", // Making these the default for gpt-5 for now
-                  reasoningEffort: usesLowReasoningEffort ? "low" : "minimal",
+                  textVerbosity: isCodex ? "medium" : "low", // codex models only support 'medium'
+                  reasoningEffort: isCodex
+                    ? "medium"
+                    : usesLowReasoningEffort
+                      ? "low"
+                      : "minimal",
                 },
               }
             : undefined,
diff --git a/packages/evals/lib/AISdkClientWrapped.ts b/packages/evals/lib/AISdkClientWrapped.ts
index 3b5dd5439..f5797859c 100644
--- a/packages/evals/lib/AISdkClientWrapped.ts
+++ b/packages/evals/lib/AISdkClientWrapped.ts
@@ -134,14 +134,15 @@ export class AISdkClientWrapped extends LLMClient {
 
     let objectResponse: Awaited<ReturnType<typeof generateObject>>;
     const isGPT5 = this.model.modelId.includes("gpt-5");
+    const isCodex = this.model.modelId.includes("codex");
     const usesLowReasoningEffort =
-      this.model.modelId.includes("gpt-5.1") ||
-      this.model.modelId.includes("gpt-5.2");
+      (this.model.modelId.includes("gpt-5.1") ||
+        this.model.modelId.includes("gpt-5.2")) &&
+      !isCodex;
     const isDeepSeek = this.model.modelId.includes("deepseek");
     // Kimi models only support temperature=1
     const isKimi = this.model.modelId.includes("kimi");
     const temperature = isKimi ? 1 : options.temperature;
-
     if (options.response_model) {
       if (isDeepSeek || isKimi) {
         const parsedSchema = JSON.stringify(
@@ -164,8 +165,12 @@ You must respond in JSON format. respond WITH JSON. Do not include any other tex
           providerOptions: isGPT5
             ? {
                 openai: {
-                  textVerbosity: "low", // Making these the default for gpt-5 for now
-                  reasoningEffort: usesLowReasoningEffort ? "low" : "minimal",
+                  textVerbosity: isCodex ? "medium" : "low", // codex models only support 'medium'
+                  reasoningEffort: isCodex
+                    ? "medium"
+                    : usesLowReasoningEffort
+                      ? "low"
+                      : "minimal",
                 },
               }
             : undefined,