diff --git a/src/deeptrust/agents/livekit.py b/src/deeptrust/agents/livekit.py
index 91f08c7..d3665ad 100644
--- a/src/deeptrust/agents/livekit.py
+++ b/src/deeptrust/agents/livekit.py
@@ -190,6 +190,30 @@ def listen(
     return stop
 
 
+# The API's metadata limits, checked here so a bad config fails once, not every request.
+MAX_CONFIG_KEYS = 32
+MAX_CONFIG_VALUE = 1024
+MAX_PROMPT = 65536
+
+
+def _config_attributes(config: dict[str, str | None]) -> dict[str, str]:
+    attributes = {f"deeptrust_{k}": str(v) for k, v in config.items() if v}
+    if len(attributes) > MAX_CONFIG_KEYS:
+        raise ValueError(f"config has more than {MAX_CONFIG_KEYS} keys")
+    for key, value in attributes.items():
+        limit = MAX_PROMPT if key == "deeptrust_prompt" else MAX_CONFIG_VALUE
+        if len(value) > limit:
+            raise ValueError(f"config {key} is longer than {limit} characters")
+    return attributes
+
+
+async def tag_call(room: Any, **config: str | None) -> None:
+    """Tag the call with what it ran on (test_name, prompt_id, llm, ...). Call after
+    ``ctx.connect()``; every participant sees it, so send ``prompt_id``, not
+    ``prompt``, with browser callers."""
+    await room.local_participant.set_attributes(_config_attributes(config))
+
+
 def attach(
     agent_session: Any,
     dt: DeepTrust,
@@ -200,6 +224,7 @@ def attach(
     user: User | None = None,
     interrupt: bool = True,
     on_analysis: Callable[[Any], None] | None = None,
+    config: dict[str, str | None] | None = None,
 ) -> Any:
     """Wire a LiveKit AgentSession to DeepTrust. Returns the DeepTrust session.
 
@@ -215,10 +240,17 @@ def attach(
     When the session closes, the DeepTrust call is ended so post-call
     processing starts at once.
 
+    Pass ``config`` to record what the call ran on (see ``tag_call``).
+
     Returns the DeepTrust session, so the transcript and findings remain
     reachable.
     """
-    call = dt.session(external_id=external_id, user=user, platform="livekit")
+    call = dt.session(
+        external_id=external_id,
+        user=user,
+        platform="livekit",
+        metadata=dict(_config_attributes(config or {})),
+    )
     spawn = _spawner()
     delivery = _Delivery(agent_session, agent, interrupt)
     stop = delivery.listen(room, spawn) if room is not None else None
diff --git a/tests/test_adapters.py b/tests/test_adapters.py
index f8fc3dd..261ba59 100644
--- a/tests/test_adapters.py
+++ b/tests/test_adapters.py
@@ -9,6 +9,7 @@
 import asyncio
 import json
 from dataclasses import dataclass
+from types import SimpleNamespace
 from typing import Any
 
 import httpx
@@ -17,7 +18,7 @@
 
 from deeptrust.agents import DeepTrust
 from deeptrust.agents.elevenlabs import Monitor, _read_turn, contextual_update_command
-from deeptrust.agents.livekit import attach, listen
+from deeptrust.agents.livekit import attach, listen, tag_call
 from deeptrust.agents.vapi import (
     SECRET_HEADER,
     Bridge,
@@ -176,6 +177,51 @@ async def settle() -> None:
         await asyncio.sleep(0.01)
 
 
+async def test_livekit_tag_call_sets_deeptrust_attributes() -> None:
+    room = FakeRoom()
+    set_to: dict[str, str] = {}
+
+    async def set_attributes(attributes: dict[str, str]) -> None:
+        set_to.update(attributes)
+
+    room.local_participant = SimpleNamespace(set_attributes=set_attributes)
+    await tag_call(
+        room, test_name="gpt-4o-vs-gpt-4.1", llm="openai/gpt-4.1", stt=None, tts=""
+    )
+
+    assert set_to == {
+        "deeptrust_test_name": "gpt-4o-vs-gpt-4.1",
+        "deeptrust_llm": "openai/gpt-4.1",
+    }
+
+
+def test_livekit_config_over_the_api_limits_fails_up_front() -> None:
+    dt = DeepTrust(api_key="dt_test", base_url=BASE)
+    with pytest.raises(ValueError):
+        attach(FakeSession(), dt, external_id="r", config={"llm": "x" * 1025})
+    with pytest.raises(ValueError):
+        attach(FakeSession(), dt, external_id="r", config={"prompt": "x" * 65537})
+    attach(FakeSession(), dt, external_id="r", config={"prompt": "x" * 5000})
+
+
+@respx.mock
+async def test_livekit_attach_sends_the_config_as_metadata() -> None:
+    route = respx.post(f"{BASE}/agents/analyze").mock(
+        return_value=httpx.Response(
+            200, json={"session_id": "sess_1", "job_id": "job_1", "findings": []}
+        )
+    )
+    lk = FakeSession()
+    dt = DeepTrust(api_key="dt_test", base_url=BASE)
+    attach(lk, dt, external_id="room-1", config={"test_name": "t1", "llm": None})
+
+    await lk.say("user", "hello")
+    await settle()
+
+    sent = json.loads(route.calls.last.request.content)
+    assert sent["metadata"] == {"deeptrust_test_name": "t1"}
+
+
 @respx.mock
 async def test_livekit_analyses_caller_turns_and_delivers_once() -> None:
     route = respx.post(f"{BASE}/agents/analyze").mock(