fix: token exchange support

litellm/proxy/auth_v2/authenticators/oauth.py

@@ -87,6 +87,7 @@ class OAuth2Authenticator(Authenticator):
             audience=token_audience,
             scopes=split_scope(body.get("scope")),
             claims=claims,
+            subject_token=token,
         )
 
     def challenge(self) -> str:

litellm/proxy/auth_v2/authenticators/utils.py

@@ -66,6 +66,7 @@ def credential_from_claims(
         scopes=split_scope(claims.get("scope")),
         claims=claims,
         credential_ref=CredentialRef(key_id=header.get("kid"), token_id=claims.get("jti")),
+        subject_token=token,
     )
 
 

litellm/proxy/auth_v2/models.py

@@ -97,6 +97,12 @@ class Credential(BaseModel):
     credential_ref: CredentialRef = Field(default_factory=CredentialRef)
     client_certificate: Optional[ClientCertificate] = None
 
+    # Raw bearer/access token as presented by the caller, retained so it can be
+    # used as the subject_token for downstream token exchange (RFC 8693) when
+    # calling LLM providers or MCP servers on the caller's behalf. None for
+    # schemes without an exchangeable token (API key, HTTP basic, mTLS).
+    subject_token: Optional[str] = None
+
 
 class Principal(BaseModel):
     """Normalized caller identity. Identity only, no policy/budget state."""