fix(agent): enhance service tier parsing for OpenAI provider

Signed-off-by: maddygoround <m.rathod@xsolla.com>

Author: maddygoround

crates/buzz-agent/src/config.rs

@@ -847,7 +847,10 @@ impl Config {
             hook_servers: parse_hook_servers_env("MCP_HOOK_SERVERS"),
             hints_enabled: parse_env("BUZZ_AGENT_NO_HINTS", 0u8)? == 0,
             thinking_effort: parse_thinking_effort(env("BUZZ_AGENT_THINKING_EFFORT").as_deref())?,
-            service_tier: parse_service_tier(env("BUZZ_AGENT_SERVICE_TIER").as_deref())?,
+            service_tier: parse_service_tier_for_provider(
+                provider,
+                env("BUZZ_AGENT_SERVICE_TIER").as_deref(),
+            )?,
         };
         cfg.validate()?;
         Ok(cfg)
@@ -992,6 +995,17 @@ pub fn parse_service_tier(raw: Option<&str>) -> Result<Option<OpenAiServiceTier>
     }
 }
 
+fn parse_service_tier_for_provider(
+    provider: Provider,
+    raw: Option<&str>,
+) -> Result<Option<OpenAiServiceTier>, String> {
+    if matches!(provider, Provider::OpenAi) {
+        parse_service_tier(raw)
+    } else {
+        Ok(None)
+    }
+}
+
 fn env(k: &str) -> Option<String> {
     std::env::var(k).ok()
 }
@@ -1401,6 +1415,14 @@ mod tests {
         assert_eq!(parse_service_tier(Some(" ")).unwrap(), None);
     }
 
+    #[test]
+    fn parse_service_tier_is_ignored_for_non_openai_providers() {
+        assert_eq!(
+            parse_service_tier_for_provider(Provider::Anthropic, Some("invalid")).unwrap(),
+            None
+        );
+    }
+
     #[test]
     fn parse_service_tier_rejects_unknown_value() {
         let err = parse_service_tier(Some("economy")).unwrap_err();