diff --git a/pyproject.toml b/pyproject.toml
index 4141faac8..cdecce13f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -59,7 +59,7 @@ dev = [
 # Install with: pip install -e ".[langchain]"
 # Versions auto-updated by scripts/update_langchain_versions.py
 langchain = [
-    "langchain>=1.3.4,<1.4",
+    "langchain>=1.3.9,<1.4",
     "langchain-core>=1.4.3,<1.5",
     "langchain-community>=0.4.2,<0.5",
     "langchain-openai>=1.3.0,<1.4",
diff --git a/requirements.txt b/requirements.txt
index aba3b5760..7e2d871bf 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,7 +8,7 @@ pandas==3.0.3
 tomlkit==0.14.0
 
 # LangChain integration
-langchain==1.3.4
+langchain==1.3.9
 langchain-core==1.4.3
 langchain-community==0.4.2
 langchain-openai==1.3.0
diff --git a/templates/consumer-repo/tools/requirements-llm.txt b/templates/consumer-repo/tools/requirements-llm.txt
index 19979b6ea..01afd9699 100644
--- a/templates/consumer-repo/tools/requirements-llm.txt
+++ b/templates/consumer-repo/tools/requirements-llm.txt
@@ -7,7 +7,7 @@
 # - Use strict X.Y.Z pins for direct workflow dependencies.
 # - Do not pin `langchain-core` directly here; let the selected `langchain`
 #   release resolve a mutually compatible core version.
-langchain==1.3.4
+langchain==1.3.9
 langchain-community==0.4.2
 langchain-openai==1.3.0
 langchain-anthropic==1.4.4
diff --git a/tools/requirements-llm.txt b/tools/requirements-llm.txt
index 19979b6ea..01afd9699 100644
--- a/tools/requirements-llm.txt
+++ b/tools/requirements-llm.txt
@@ -7,7 +7,7 @@
 # - Use strict X.Y.Z pins for direct workflow dependencies.
 # - Do not pin `langchain-core` directly here; let the selected `langchain`
 #   release resolve a mutually compatible core version.
-langchain==1.3.4
+langchain==1.3.9
 langchain-community==0.4.2
 langchain-openai==1.3.0
 langchain-anthropic==1.4.4