diff --git a/pyproject.toml b/pyproject.toml
index 30c4bb1..89df075 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,7 +57,7 @@ test = [
     "mcp>=1.27.0,<2.0.0",  # 2.0 removed mcp.server.fastmcp; migration tracked separately
     "a2a-sdk>=0.3.0,<1.0.0",
     "acp-sdk>=1.0.0",
-    "openai>=2.0.0",
+    "openai>=2.51.0",
     "google-genai>=1.0.0",
     "agntcy-acp>=1.5.0",
 ]
diff --git a/requirements.txt b/requirements.txt
index bb44c5c..371194f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -16,7 +16,7 @@ httpx>=0.28.1
 mcp>=1.27.0,<2.0.0
 a2a-sdk>=0.3.0,<1.0.0   # 0.3.x ships the JSON-RPC pydantic types we target
 acp-sdk>=1.0.0          # ACP models (server class is bypassed; see docs/PROTOCOL_SUPPORT.md)
-openai>=2.0.0           # ChatCompletionMessageToolCall (function-calling format)
+openai>=2.51.0           # ChatCompletionMessageToolCall (function-calling format)
 google-genai>=1.0.0     # Gemini FunctionCall / FunctionResponse
 agntcy-acp>=1.5.0       # AGNTCY Agent Connect Protocol (RunCreateStateless, MessageTextBlock)