fix: patch TracerManager.init defaults to set correct OTEL service name

The previous sys.argv[0] override had no effect because Python evaluates
default arguments at import time — TracerManager.init(app_name=sys.argv[0])
captured the binary path (/usr/local/bin/openhands-agent-server) when the
module was first loaded. Now we patch __defaults__ directly so the correct
OTEL_SERVICE_NAME is used when Laminar.initialize() calls TracerManager.init().

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Zach Arnold

openhands-sdk/openhands/sdk/observability/laminar.py

@@ -1,5 +1,4 @@
 import os
-import sys
 from collections.abc import Callable
 from typing import (
     Any,
@@ -43,12 +42,19 @@ def maybe_init_laminar():
     ```
     """
     if should_enable_observability():
-        # Laminar.initialize() doesn't expose app_name but internally calls
-        # TracerManager.init(app_name=sys.argv[0]).  Override sys.argv[0]
-        # temporarily so the OTEL service.name resource attribute is correct.
+        # Laminar.initialize() calls TracerManager.init() without passing
+        # app_name, so it falls back to the default: sys.argv[0].  However,
+        # Python evaluates default arguments at *import time*, so the default
+        # is baked in as the binary path (e.g. /usr/local/bin/openhands-agent-server)
+        # before we can override sys.argv[0].
+        #
+        # Fix: patch TracerManager.init's default for app_name directly.
         service_name = os.environ.get('OTEL_SERVICE_NAME', 'openhands-agent-server')
-        saved_argv0 = sys.argv[0]
-        sys.argv[0] = service_name
+        from lmnr.opentelemetry_lib import TracerManager
+
+        _orig_defaults = TracerManager.init.__defaults__
+        # app_name is the first default (position 0)
+        TracerManager.init.__defaults__ = (service_name,) + _orig_defaults[1:]
         try:
             if _is_otel_backend_laminar():
                 Laminar.initialize()
@@ -62,7 +68,7 @@ def maybe_init_laminar():
                     ],
                 )
         finally:
-            sys.argv[0] = saved_argv0
+            TracerManager.init.__defaults__ = _orig_defaults
         # Wrap the TracerProvider's sampler to drop health-check spans.
         # This is the OTEL equivalent of DD_TRACE_SAMPLING_RULES.
         provider = trace.get_tracer_provider()

tests/sdk/test_laminar_service_name.py

@@ -0,0 +1,95 @@
+"""Test that maybe_init_laminar sets the correct OTEL service.name.
+
+Regression test for the bug where Laminar's TracerManager.init captured
+sys.argv[0] at *import time* (the binary path, e.g.
+/usr/local/bin/openhands-agent-server) and ignored the OTEL_SERVICE_NAME
+env var.
+"""
+
+import subprocess
+import sys
+import textwrap
+
+
+def test_service_name_uses_otel_env_var_not_argv():
+    """service.name should come from OTEL_SERVICE_NAME, not sys.argv[0].
+
+    Run in a subprocess to get a clean Python interpreter — OTEL and Laminar
+    are singleton-heavy and impossible to reset reliably in-process.
+    """
+    script = textwrap.dedent("""\
+        import os, sys
+
+        # Simulate the container: argv[0] is the installed console-script path
+        sys.argv[0] = "/usr/local/bin/openhands-agent-server"
+
+        os.environ["OTEL_SERVICE_NAME"] = "openhands-agent-server"
+        os.environ["OTEL_EXPORTER_OTLP_TRACES_ENDPOINT"] = "http://localhost:4317"
+
+        from openhands.sdk.observability.laminar import maybe_init_laminar
+        maybe_init_laminar()
+
+        from opentelemetry import trace
+        from opentelemetry.sdk.trace import TracerProvider as SdkTracerProvider
+        from opentelemetry.sdk.resources import SERVICE_NAME
+
+        provider = trace.get_tracer_provider()
+        assert isinstance(provider, SdkTracerProvider), (
+            f"Expected SdkTracerProvider, got {type(provider)}"
+        )
+        service = provider.resource.attributes.get(SERVICE_NAME)
+        assert service == "openhands-agent-server", (
+            f"Expected 'openhands-agent-server', got '{service}'"
+        )
+        # Must NOT contain the binary path
+        assert "/usr/local/bin" not in str(service), (
+            f"service.name leaked binary path: {service}"
+        )
+        print("OK")
+    """)
+    result = subprocess.run(
+        [sys.executable, '-c', script],
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+    assert result.returncode == 0, (
+        f'Subprocess failed:\nstdout: {result.stdout}\nstderr: {result.stderr}'
+    )
+    assert 'OK' in result.stdout
+
+
+def test_custom_service_name():
+    """A non-default OTEL_SERVICE_NAME should be respected."""
+    script = textwrap.dedent("""\
+        import os, sys
+
+        sys.argv[0] = "/usr/local/bin/openhands-agent-server"
+        os.environ["OTEL_SERVICE_NAME"] = "my-custom-service"
+        os.environ["OTEL_EXPORTER_OTLP_TRACES_ENDPOINT"] = "http://localhost:4317"
+
+        from openhands.sdk.observability.laminar import maybe_init_laminar
+        maybe_init_laminar()
+
+        from opentelemetry import trace
+        from opentelemetry.sdk.trace import TracerProvider as SdkTracerProvider
+        from opentelemetry.sdk.resources import SERVICE_NAME
+
+        provider = trace.get_tracer_provider()
+        assert isinstance(provider, SdkTracerProvider)
+        service = provider.resource.attributes.get(SERVICE_NAME)
+        assert service == "my-custom-service", (
+            f"Expected 'my-custom-service', got '{service}'"
+        )
+        print("OK")
+    """)
+    result = subprocess.run(
+        [sys.executable, '-c', script],
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+    assert result.returncode == 0, (
+        f'Subprocess failed:\nstdout: {result.stdout}\nstderr: {result.stderr}'
+    )
+    assert 'OK' in result.stdout