From 7ea84e9936e454fe1138b35d5d05faf98678165c Mon Sep 17 00:00:00 2001
From: JeongHeon Woo <contact@wookingwoo.com>
Date: Mon, 15 Dec 2025 23:21:27 +0900
Subject: [PATCH 1/3] fix(langchain-openai): fix operator precedence in
 reasoning initialization

---
 libs/langchain-openai/src/chat_models.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libs/langchain-openai/src/chat_models.ts b/libs/langchain-openai/src/chat_models.ts
index 70dfa17d45b2..143a17c70df3 100644
--- a/libs/langchain-openai/src/chat_models.ts
+++ b/libs/langchain-openai/src/chat_models.ts
@@ -799,9 +799,10 @@ export abstract class BaseChatOpenAI<
     this.audio = fields?.audio;
     this.modalities = fields?.modalities;
     this.reasoning =
-      fields?.reasoning ?? fields?.reasoningEffort
+      fields?.reasoning ??
+      (fields?.reasoningEffort
         ? { effort: fields.reasoningEffort }
-        : undefined;
+        : undefined);
     this.maxTokens = fields?.maxCompletionTokens ?? fields?.maxTokens;
     this.disableStreaming = fields?.disableStreaming === true;
     this.streaming = fields?.streaming === true;

From 490bf47ee120a5d73791e004d0e78d9eeb7f24da Mon Sep 17 00:00:00 2001
From: JeongHeon Woo <contact@wookingwoo.com>
Date: Tue, 16 Dec 2025 08:22:23 +0000
Subject: [PATCH 2/3] test(openai): add tests for reasoning field
 initialization

---
 .../src/tests/chat_models.test.ts             | 57 +++++++++++++++++--
 1 file changed, 52 insertions(+), 5 deletions(-)

diff --git a/libs/langchain-openai/src/tests/chat_models.test.ts b/libs/langchain-openai/src/tests/chat_models.test.ts
index d2ce79a5fae2..3b72ed760154 100644
--- a/libs/langchain-openai/src/tests/chat_models.test.ts
+++ b/libs/langchain-openai/src/tests/chat_models.test.ts
@@ -574,13 +574,60 @@ describe("ChatOpenAI", () => {
     });
   });
 
-  test("can be constructed with reasoningEffort", async () => {
-    const model = new ChatOpenAI({
-      model: "gpt-4o-2024-08-06",
-      reasoningEffort: "low",
+  describe("reasoning field initialization", () => {
+    it("can be constructed with reasoningEffort", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-4o-2024-08-06",
+        reasoningEffort: "low",
+      });
+
+      expect(model.reasoning).toEqual({ effort: "low" });
+    });
+
+    it("can be constructed with explicit reasoning object", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-5.2-2025-12-11",
+        reasoning: { effort: "medium" },
+      });
+
+      expect(model.reasoning).toEqual({ effort: "medium" });
+    });
+
+    it("reasoning takes precedence over reasoningEffort", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-5.2-2025-12-11",
+        reasoning: { effort: "high" },
+        reasoningEffort: "low",
+      });
+
+      expect(model.reasoning).toEqual({ effort: "high" });
     });
 
-    expect(model.reasoning).toEqual({ effort: "low" });
+    it("reasoning is undefined when neither field is provided", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-5.2-2025-12-11",
+      });
+
+      expect(model.reasoning).toBeUndefined();
+    });
+
+    it("reasoning is undefined when reasoningEffort is undefined", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-5.2-2025-12-11",
+        reasoningEffort: undefined,
+      });
+
+      expect(model.reasoning).toBeUndefined();
+    });
+
+    it("reasoning is undefined when reasoningEffort is null", async () => {
+      const model = new ChatOpenAI({
+        model: "gpt-5.2-2025-12-11",
+        reasoningEffort: null as any,
+      });
+
+      expect(model.reasoning).toBeUndefined();
+    });
   });
 
   test("specifying streaming=false disables streaming", async () => {

From a7e1cfb2c75425d6cffb733711c88ed52d6390ce Mon Sep 17 00:00:00 2001
From: Hunter Lovell <40191806+hntrl@users.noreply.github.com>
Date: Mon, 22 Dec 2025 15:20:24 -0800
Subject: [PATCH 3/3] Create neat-candles-share.md

---
 .changeset/neat-candles-share.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/neat-candles-share.md

diff --git a/.changeset/neat-candles-share.md b/.changeset/neat-candles-share.md
new file mode 100644
index 000000000000..8100578b50c0
--- /dev/null
+++ b/.changeset/neat-candles-share.md
@@ -0,0 +1,5 @@
+---
+"@langchain/openai": patch
+---
+
+fix operator precedence in reasoning initialization