Log OAuth env when launching fast-agent subprocess

app.py

@@ -40,7 +40,18 @@ def _start_fast_agent() -> subprocess.Popen[str]:
         "--instance-scope",
         "request",
     ]
-    return subprocess.Popen(command, text=True)
+    print(
+        (
+            "[STARTUP DEBUG] launching fast-agent "
+            f"FAST_AGENT_SERVE_OAUTH={os.getenv('FAST_AGENT_SERVE_OAUTH')!r} "
+            f"FAST_AGENT_OAUTH_SCOPES={os.getenv('FAST_AGENT_OAUTH_SCOPES')!r} "
+            f"FAST_AGENT_OAUTH_RESOURCE_URL={os.getenv('FAST_AGENT_OAUTH_RESOURCE_URL')!r} "
+            f"command={' '.join(command)}"
+        ),
+        file=sys.stderr,
+        flush=True,
+    )
+    return subprocess.Popen(command, text=True, env=dict(os.environ))
 
 
 async def _wait_for_upstream(timeout_seconds: float = 30.0) -> None: