diff --git a/hud/eval/instrument.py b/hud/eval/instrument.py
index e950522c..94598f1f 100644
--- a/hud/eval/instrument.py
+++ b/hud/eval/instrument.py
@@ -1,6 +1,6 @@
-"""Auto-instrumentation for httpx to inject trace headers.
+"""Auto-instrumentation for httpx and aiohttp to inject trace headers.
 
-This module patches httpx clients to automatically add:
+This module patches HTTP clients to automatically add:
 - Trace-Id headers when inside an eval context
 - Authorization headers for HUD API calls
 """
@@ -8,9 +8,12 @@
 from __future__ import annotations
 
 import logging
-from typing import Any
+from typing import TYPE_CHECKING, Any
 from urllib.parse import urlparse
 
+if TYPE_CHECKING:
+    from types import SimpleNamespace
+
 from hud.settings import settings
 
 logger = logging.getLogger(__name__)
@@ -70,7 +73,7 @@ async def _async_httpx_request_hook(request: Any) -> None:
     _httpx_request_hook(request)
 
 
-def _instrument_client(client: Any) -> None:
+def _instrument_httpx_client(client: Any) -> None:
     """Add trace hook to an httpx client instance."""
     is_async = hasattr(client, "aclose")
     hook = _async_httpx_request_hook if is_async else _httpx_request_hook
@@ -93,7 +96,7 @@ def _patch_httpx() -> None:
 
     def _patched_async_init(self: Any, *args: Any, **kwargs: Any) -> None:
         _original_async_init(self, *args, **kwargs)
-        _instrument_client(self)
+        _instrument_httpx_client(self)
 
     httpx.AsyncClient.__init__ = _patched_async_init  # type: ignore[method-assign]
 
@@ -101,15 +104,65 @@ def _patched_async_init(self: Any, *args: Any, **kwargs: Any) -> None:
 
     def _patched_sync_init(self: Any, *args: Any, **kwargs: Any) -> None:
         _original_sync_init(self, *args, **kwargs)
-        _instrument_client(self)
+        _instrument_httpx_client(self)
 
     httpx.Client.__init__ = _patched_sync_init  # type: ignore[method-assign]
 
     logger.debug("httpx auto-instrumentation enabled")
 
 
-# Auto-patch httpx on module import
+def _patch_aiohttp() -> None:
+    """
+    Monkey-patch aiohttp to auto-instrument all ClientSession instances.
+    This is important for the Gemini client in particular, which uses aiohttp by default.
+    """
+    try:
+        import aiohttp
+    except ImportError:
+        logger.debug("aiohttp not installed, skipping auto-instrumentation")
+        return
+
+    async def on_request_start(
+        _session: aiohttp.ClientSession,
+        _trace_config_ctx: SimpleNamespace,
+        params: aiohttp.TraceRequestStartParams,
+    ) -> None:
+        """aiohttp trace hook that adds trace headers and auth to HUD requests."""
+        url_str = str(params.url)
+        if not _is_hud_url(url_str):
+            return
+
+        trace_headers = _get_trace_headers()
+        if trace_headers is not None:
+            for key, value in trace_headers.items():
+                params.headers[key] = value
+            logger.debug("Added trace headers to aiohttp request: %s", url_str)
+
+        has_auth = "authorization" in {k.lower() for k in params.headers}
+        if not has_auth and settings.api_key:
+            params.headers["Authorization"] = f"Bearer {settings.api_key}"
+            logger.debug("Added API key auth to aiohttp request: %s", url_str)
+
+    trace_config = aiohttp.TraceConfig()
+    trace_config.on_request_start.append(on_request_start)
+
+    _original_init = aiohttp.ClientSession.__init__
+
+    def _patched_init(self: aiohttp.ClientSession, *args: Any, **kwargs: Any) -> None:
+        existing_traces = kwargs.get("trace_configs") or []
+        if trace_config not in existing_traces:
+            existing_traces = [*list(existing_traces), trace_config]
+        kwargs["trace_configs"] = existing_traces
+        _original_init(self, *args, **kwargs)
+
+    aiohttp.ClientSession.__init__ = _patched_init  # type: ignore[method-assign]
+
+    logger.debug("aiohttp auto-instrumentation enabled")
+
+
+# Auto-patch on module import
 _patch_httpx()
+_patch_aiohttp()
 
 
-__all__ = ["_patch_httpx"]
+__all__ = ["_patch_aiohttp", "_patch_httpx"]