diff --git a/src/interfaze/_client.py b/src/interfaze/_client.py
index 128ead9..c0a83b3 100644
--- a/src/interfaze/_client.py
+++ b/src/interfaze/_client.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import os
-from typing import Any, Dict, Optional
+from typing import Any, Dict, Optional, Union
 
 from openai import AsyncOpenAI, OpenAI
 
@@ -46,6 +46,17 @@ def _build_headers(
     return headers
 
 
+# OpenAI() fills `organization` / `project` from OPENAI_ORG_ID / OPENAI_PROJECT_ID and sends them
+# as OpenAI-Organization / OpenAI-Project headers. Those are OpenAI account ids, so keep them off
+# Interfaze requests unless they were passed in explicitly.
+# This only covers the client built here: one derived via client.openai.with_options(...) or
+# .copy() goes back through the constructor with organization/project None, so it reads the
+# env vars again and sends them.
+def _drop_openai_env_ids(client: Union[OpenAI, AsyncOpenAI], kwargs: Dict[str, Any]) -> None:
+    client.organization = kwargs.get("organization")
+    client.project = kwargs.get("project")
+
+
 class Interfaze:
     def __init__(
         self,
@@ -68,6 +79,7 @@ def __init__(
             ),
             **kwargs,
         )
+        _drop_openai_env_ids(self.openai, kwargs)
         self.chat = Chat(self.openai)
         self.models = self.openai.models
         self.tasks = Tasks(self.chat.completions)
@@ -95,6 +107,7 @@ def __init__(
             ),
             **kwargs,
         )
+        _drop_openai_env_ids(self.openai, kwargs)
         self.chat = AsyncChat(self.openai)
         self.models = self.openai.models
         self.tasks = AsyncTasks(self.chat.completions)
diff --git a/tests/test_chat.py b/tests/test_chat.py
index c072e21..0e8b7ea 100644
--- a/tests/test_chat.py
+++ b/tests/test_chat.py
@@ -146,6 +146,33 @@ def test_default_headers_omit_control_flags_when_unset():
     assert "x-admin-key" not in h
 
 
+@respx.mock
+def test_openai_org_and_project_env_not_sent(monkeypatch):
+    monkeypatch.setenv("OPENAI_ORG_ID", "org-from-env")
+    monkeypatch.setenv("OPENAI_PROJECT_ID", "proj_from_env")
+    route = mock_json(BASIC)
+    Interfaze(api_key="t").chat.completions.create(messages=[{"role": "user", "content": "x"}])
+    h = last_headers(route)
+    assert "openai-organization" not in h and "openai-project" not in h
+
+    asyncio.run(
+        AsyncInterfaze(api_key="t").chat.completions.create(messages=[{"role": "user", "content": "x"}])
+    )
+    h = last_headers(route)
+    assert "openai-organization" not in h and "openai-project" not in h
+
+
+@respx.mock
+def test_explicit_openai_org_and_project_still_sent(monkeypatch):
+    monkeypatch.setenv("OPENAI_ORG_ID", "org-from-env")
+    route = mock_json(BASIC)
+    Interfaze(api_key="t", organization="org-explicit", project="proj_explicit").chat.completions.create(
+        messages=[{"role": "user", "content": "x"}]
+    )
+    h = last_headers(route)
+    assert h["openai-organization"] == "org-explicit" and h["openai-project"] == "proj_explicit"
+
+
 @respx.mock
 def test_per_request_extra_headers_override_client_default():
     route = mock_json(BASIC)