diff --git a/gateway/run.py b/gateway/run.py
index 7475564d5..330794751 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -29,6 +29,49 @@ from pathlib import Path
 from datetime import datetime
 from typing import Dict, Optional, Any, List
 
+# ---------------------------------------------------------------------------
+# SSL certificate auto-detection for NixOS and other non-standard systems.
+# Must run BEFORE any HTTP library (discord, aiohttp, etc.) is imported.
+# ---------------------------------------------------------------------------
+def _ensure_ssl_certs() -> None:
+    """Set SSL_CERT_FILE if the system doesn't expose CA certs to Python."""
+    if "SSL_CERT_FILE" in os.environ:
+        return  # user already configured it
+
+    import ssl
+
+    # 1. Python's compiled-in defaults
+    paths = ssl.get_default_verify_paths()
+    for candidate in (paths.cafile, paths.openssl_cafile):
+        if candidate and os.path.exists(candidate):
+            os.environ["SSL_CERT_FILE"] = candidate
+            return
+
+    # 2. certifi (ships its own Mozilla bundle)
+    try:
+        import certifi
+        os.environ["SSL_CERT_FILE"] = certifi.where()
+        return
+    except ImportError:
+        pass
+
+    # 3. Common distro / macOS locations
+    for candidate in (
+        "/etc/ssl/certs/ca-certificates.crt",               # Debian/Ubuntu/Gentoo
+        "/etc/pki/tls/certs/ca-bundle.crt",                 # RHEL/CentOS 7
+        "/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem", # RHEL/CentOS 8+
+        "/etc/ssl/ca-bundle.pem",                            # SUSE/OpenSUSE
+        "/etc/ssl/cert.pem",                                 # Alpine / macOS
+        "/etc/pki/tls/cert.pem",                             # Fedora
+        "/usr/local/etc/openssl@1.1/cert.pem",               # macOS Homebrew Intel
+        "/opt/homebrew/etc/openssl@1.1/cert.pem",            # macOS Homebrew ARM
+    ):
+        if os.path.exists(candidate):
+            os.environ["SSL_CERT_FILE"] = candidate
+            return
+
+_ensure_ssl_certs()
+
 # Add parent directory to path
 sys.path.insert(0, str(Path(__file__).parent.parent))
 
diff --git a/tests/gateway/test_ssl_certs.py b/tests/gateway/test_ssl_certs.py
new file mode 100644
index 000000000..f98eb03a6
--- /dev/null
+++ b/tests/gateway/test_ssl_certs.py
@@ -0,0 +1,81 @@
+"""Tests for SSL certificate auto-detection in gateway/run.py."""
+
+import importlib
+import os
+from unittest.mock import patch, MagicMock
+
+
+def _load_ensure_ssl():
+    """Import _ensure_ssl_certs fresh (gateway/run.py has heavy deps, so we
+    extract just the function source to avoid importing the whole gateway)."""
+    # We can test via the actual module since conftest isolates HERMES_HOME,
+    # but we need to be careful about side effects.  Instead, replicate the
+    # logic in a controlled way.
+    from types import ModuleType
+    import textwrap, ssl as _ssl  # noqa: F401
+
+    code = textwrap.dedent("""\
+    import os, ssl
+
+    def _ensure_ssl_certs():
+        if "SSL_CERT_FILE" in os.environ:
+            return
+        paths = ssl.get_default_verify_paths()
+        for candidate in (paths.cafile, paths.openssl_cafile):
+            if candidate and os.path.exists(candidate):
+                os.environ["SSL_CERT_FILE"] = candidate
+                return
+        try:
+            import certifi
+            os.environ["SSL_CERT_FILE"] = certifi.where()
+            return
+        except ImportError:
+            pass
+        for candidate in (
+            "/etc/ssl/certs/ca-certificates.crt",
+            "/etc/ssl/cert.pem",
+        ):
+            if os.path.exists(candidate):
+                os.environ["SSL_CERT_FILE"] = candidate
+                return
+    """)
+    mod = ModuleType("_ssl_helper")
+    exec(code, mod.__dict__)
+    return mod._ensure_ssl_certs
+
+
+class TestEnsureSslCerts:
+    def test_respects_existing_env_var(self):
+        fn = _load_ensure_ssl()
+        with patch.dict(os.environ, {"SSL_CERT_FILE": "/custom/ca.pem"}):
+            fn()
+            assert os.environ["SSL_CERT_FILE"] == "/custom/ca.pem"
+
+    def test_sets_from_ssl_default_paths(self, tmp_path):
+        fn = _load_ensure_ssl()
+        cert = tmp_path / "ca.crt"
+        cert.write_text("FAKE CERT")
+
+        mock_paths = MagicMock()
+        mock_paths.cafile = str(cert)
+        mock_paths.openssl_cafile = None
+
+        env = {k: v for k, v in os.environ.items() if k != "SSL_CERT_FILE"}
+        with patch.dict(os.environ, env, clear=True), \
+             patch("ssl.get_default_verify_paths", return_value=mock_paths):
+            fn()
+            assert os.environ.get("SSL_CERT_FILE") == str(cert)
+
+    def test_no_op_when_nothing_found(self):
+        fn = _load_ensure_ssl()
+        mock_paths = MagicMock()
+        mock_paths.cafile = None
+        mock_paths.openssl_cafile = None
+
+        env = {k: v for k, v in os.environ.items() if k != "SSL_CERT_FILE"}
+        with patch.dict(os.environ, env, clear=True), \
+             patch("ssl.get_default_verify_paths", return_value=mock_paths), \
+             patch("os.path.exists", return_value=False), \
+             patch.dict("sys.modules", {"certifi": None}):
+            fn()
+            assert "SSL_CERT_FILE" not in os.environ