diff --git a/agent/anthropic_adapter.py b/agent/anthropic_adapter.py
index a81736496..74539cbc2 100644
--- a/agent/anthropic_adapter.py
+++ b/agent/anthropic_adapter.py
@@ -152,13 +152,17 @@ def _is_oauth_token(key: str) -> bool:
 
     Regular API keys start with 'sk-ant-api'. Everything else (setup-tokens
     starting with 'sk-ant-oat', managed keys, JWTs, etc.) needs Bearer auth.
+    Azure AI Foundry keys (non sk-ant- prefixed) should use x-api-key, not Bearer.
     """
     if not key:
         return False
     # Regular Console API keys use x-api-key header
     if key.startswith("sk-ant-api"):
         return False
-    # Everything else (setup-tokens, managed keys, JWTs) uses Bearer auth
+    # Azure AI Foundry keys don't start with sk-ant- at all — treat as regular API key
+    if not key.startswith("sk-ant-"):
+        return False
+    # Everything else (setup-tokens sk-ant-oat, managed keys, JWTs) uses Bearer auth
     return True
 
 
diff --git a/tests/agent/test_auxiliary_client.py b/tests/agent/test_auxiliary_client.py
index 35dcee7ad..28ef57289 100644
--- a/tests/agent/test_auxiliary_client.py
+++ b/tests/agent/test_auxiliary_client.py
@@ -310,7 +310,7 @@ class TestExpiredCodexFallback:
     def test_hermes_oauth_file_sets_oauth_flag(self, monkeypatch):
         """OAuth-style tokens should get is_oauth=True (token is not sk-ant-api-*)."""
         # Mock resolve_anthropic_token to return an OAuth-style token
-        with patch("agent.anthropic_adapter.resolve_anthropic_token", return_value="hermes-oauth-jwt-token"), \
+        with patch("agent.anthropic_adapter.resolve_anthropic_token", return_value="sk-ant-oat01-hermes-oauth-test"), \
              patch("agent.anthropic_adapter.build_anthropic_client") as mock_build:
             mock_build.return_value = MagicMock()
             from agent.auxiliary_client import _try_anthropic, AnthropicAuxiliaryClient
@@ -364,7 +364,7 @@ class TestExpiredCodexFallback:
 
     def test_claude_code_oauth_env_sets_flag(self, monkeypatch):
         """CLAUDE_CODE_OAUTH_TOKEN env var should get is_oauth=True."""
-        monkeypatch.setenv("CLAUDE_CODE_OAUTH_TOKEN", "cc-oauth-token-test")
+        monkeypatch.setenv("CLAUDE_CODE_OAUTH_TOKEN", "sk-ant-oat01-cc-oauth-test")
         monkeypatch.delenv("ANTHROPIC_TOKEN", raising=False)
         with patch("agent.anthropic_adapter.build_anthropic_client") as mock_build:
             mock_build.return_value = MagicMock()