add runtime logger to braintrust javaagent

Author: realark

braintrust-java-agent/bootstrap/src/main/java/dev/braintrust/system/AgentBootstrap.java

@@ -212,6 +212,9 @@ private static boolean isRunningAfterDatadogAgent(List<AgentKind> agents) {
     }
 
     private static void enableOtelSDKAutoconfiguration() {
+        // Silence agent-internal SLF4J output by default
+        setPropertyIfAbsent("org.slf4j.simpleLogger.log.dev.braintrust", "off");
+
         // Enable OTel SDK autoconfiguration. When anyone first calls
         // GlobalOpenTelemetry.get(), the SDK will be built using autoconfigure, which
         // discovers our BraintrustAutoConfigCustomizer via ServiceLoader and injects the

braintrust-java-agent/internal/build.gradle

@@ -20,6 +20,11 @@ dependencies {
   // SLF4J API — needed at compile time for Lombok's @Slf4j annotation
   implementation "org.slf4j:slf4j-api:${slf4jVersion}"
 
+  // SLF4J Simple binding — bundled so the agent always has a logging backend
+  // (avoids "SLF4J: No SLF4J providers were found" warnings). Log level is set
+  // to OFF by default via simplelogger.properties so agent internals stay silent.
+  runtimeOnly "org.slf4j:slf4j-simple:${slf4jVersion}"
+
   // ByteBuddy for bytecode manipulation — bundled as .classdata in BraintrustClassLoader
   implementation 'net.bytebuddy:byte-buddy:1.17.5'