Fix timeout config to check behavior version and update test expectations

Author: vcjana

aws/codegen-aws-sdk/src/test/kotlin/software/amazon/smithy/rustsdk/TimeoutConfigMergingTest.kt

@@ -159,6 +159,8 @@ class TimeoutConfigMergingTest {
                             &TimeoutConfig::builder()
                                 .read_timeout(Duration::from_secs(10))
                                 .connect_timeout(connect_timeout)
+                                .disable_operation_timeout()
+                                .disable_operation_attempt_timeout()
                                 .build(),
                             "read timeout overridden"
                         );

rust-runtime/aws-smithy-runtime/src/client/defaults.rs

@@ -220,6 +220,7 @@ pub fn default_timeout_config_plugin() -> Option<SharedRuntimePlugin> {
 pub fn default_timeout_config_plugin_v2(
     params: &DefaultPluginParams,
 ) -> Option<SharedRuntimePlugin> {
+    let behavior_version = params.behavior_version.unwrap_or_else(BehaviorVersion::latest);
     let is_aws_sdk = params.is_aws_sdk;
     Some(
         default_plugin("default_timeout_config_plugin", |components| {
@@ -228,15 +229,14 @@ pub fn default_timeout_config_plugin_v2(
             ))
         })
         .with_config(layer("default_timeout_config", |layer| {
-            let timeout_config = if is_aws_sdk {
-                // AWS SDK: Set connect_timeout, explicitly disable operation timeouts
+            #[allow(deprecated)]
+            let timeout_config = if is_aws_sdk && behavior_version.is_at_least(BehaviorVersion::v2025_08_07()) {
+                // AWS SDK with new behavior version: Set connect_timeout, leave operation timeouts unset
                 TimeoutConfig::builder()
                     .connect_timeout(Duration::from_millis(3100))
-                    .disable_operation_timeout()
-                    .disable_operation_attempt_timeout()
                     .build()
             } else {
-                // Non-AWS SDK: All timeouts disabled
+                // Old behavior versions or non-AWS SDK: All timeouts disabled
                 TimeoutConfig::disabled()
             };
             layer.store_put(timeout_config);