diff --git a/crates/aionui-runtime/src/acp_tool_runtime/types.rs b/crates/aionui-runtime/src/acp_tool_runtime/types.rs
index 17a8caf78..b108e5f18 100644
--- a/crates/aionui-runtime/src/acp_tool_runtime/types.rs
+++ b/crates/aionui-runtime/src/acp_tool_runtime/types.rs
@@ -21,7 +21,7 @@ impl ManagedAcpToolId {
     pub fn version(self) -> &'static str {
         match self {
             Self::CodexAcp => "0.16.0",
-            Self::ClaudeAgentAcp => "0.47.0",
+            Self::ClaudeAgentAcp => "0.39.0",
         }
     }
 
@@ -225,7 +225,7 @@ mod tests {
     #[test]
     fn managed_acp_tool_versions_match_current_pins() {
         assert_eq!(ManagedAcpToolId::CodexAcp.version(), "0.16.0");
-        assert_eq!(ManagedAcpToolId::ClaudeAgentAcp.version(), "0.47.0");
+        assert_eq!(ManagedAcpToolId::ClaudeAgentAcp.version(), "0.39.0");
     }
 }