diff --git a/plugins/memory/mem0/__init__.py b/plugins/memory/mem0/__init__.py
index cfe97916d6..acbaadd388 100644
--- a/plugins/memory/mem0/__init__.py
+++ b/plugins/memory/mem0/__init__.py
@@ -12,7 +12,6 @@ from __future__ import annotations
 import atexit
 import json
 import logging
-import os
 import threading
 import time
 from contextlib import suppress
@@ -79,11 +78,22 @@ def _load_config() -> dict:
     Layering avoids a silent failure when the JSON file exists but lacks fields
     like ``api_key`` that the user set in ``.env``."""
     from hermes_constants import get_hermes_home
-    config = {"mode": os.environ.get("MEM0_MODE", "platform"), "api_key": get_secret("MEM0_API_KEY", ""), "host": os.environ.get("MEM0_HOST", ""), "agent_id": os.environ.get("MEM0_AGENT_ID", "hermes"), "oss": {}}
-    if os.environ.get("MEM0_USER_ID"):  # only when explicitly configured, so initialize() can fall back to the gateway-native id
-        config["user_id"] = os.environ["MEM0_USER_ID"]
+    # Identity (user/agent id), host and mode are .env values like the key: read them through the
+    # profile scope too, or a secondary profile's memories land in the default profile's account.
+    config = {"mode": get_secret("MEM0_MODE", "") or "platform", "host": get_secret("MEM0_HOST", "") or "",
+              "agent_id": get_secret("MEM0_AGENT_ID", "") or "hermes", "oss": {}}
+    if user_id := get_secret("MEM0_USER_ID", ""):  # only when explicitly configured, so initialize() can fall back to the gateway-native id
+        config["user_id"] = user_id
     file_cfg = _read_mem0_json(get_hermes_home() / "mem0.json")
     config.update({k: v for k, v in file_cfg.items() if v is not None and v != ""})
+    # MEM0_API_KEY authenticates the Platform and self-hosted HTTP backends; pure OSS mode builds its
+    # backend from the local ``oss`` config and has no platform credential to resolve. Decide after
+    # mem0.json overrode the env fallback so a scope-less multiplex caller can load an OSS config
+    # without weakening fail-closed reads for credentialed modes.
+    if config.get("mode", "platform") == "oss":
+        config.setdefault("api_key", "")
+    elif not config.get("api_key"):
+        config["api_key"] = get_secret("MEM0_API_KEY", "")
     return config
 
 
diff --git a/tests/plugins/memory/test_mem0_v3.py b/tests/plugins/memory/test_mem0_v3.py
index 870d8d49dd..c1a1160143 100644
--- a/tests/plugins/memory/test_mem0_v3.py
+++ b/tests/plugins/memory/test_mem0_v3.py
@@ -5,6 +5,7 @@ import threading
 import time
 import pytest
 
+from agent import secret_scope
 import plugins.memory.mem0 as mem0_plugin
 from plugins.memory.mem0 import Mem0MemoryProvider
 
@@ -309,6 +310,59 @@ class TestMem0V3Config:
 
 class TestMem0ModeSwitch:
 
+    def test_oss_mode_initializes_without_unscoped_platform_key(
+        self, monkeypatch, tmp_path
+    ):
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+        monkeypatch.delenv("MEM0_API_KEY", raising=False)
+        (tmp_path / "mem0.json").write_text(
+            json.dumps(
+                {
+                    "mode": "oss",
+                    "oss": {"vector_store": {"provider": "qdrant"}},
+                }
+            )
+        )
+
+        token = secret_scope.set_secret_scope(None)
+        secret_scope.set_multiplex_active(True)
+        try:
+            provider = Mem0MemoryProvider()
+            provider._create_backend = lambda: None  # type: ignore[method-assign]
+            provider.initialize("test")
+            available = provider.is_available()
+        finally:
+            secret_scope.set_multiplex_active(False)
+            secret_scope.reset_secret_scope(token)
+
+        assert provider._mode == "oss"
+        assert provider._api_key == ""
+        assert available is True
+
+    def test_platform_config_still_fails_closed_without_profile_scope(
+        self, monkeypatch, tmp_path
+    ):
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+        monkeypatch.delenv("MEM0_API_KEY", raising=False)
+
+        token = secret_scope.set_secret_scope(None)
+        secret_scope.set_multiplex_active(True)
+        try:
+            with pytest.raises(secret_scope.UnscopedSecretError):
+                Mem0MemoryProvider().is_available()
+        finally:
+            secret_scope.set_multiplex_active(False)
+            secret_scope.reset_secret_scope(token)
+
+    def test_file_api_key_still_overrides_environment(self, monkeypatch, tmp_path):
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+        monkeypatch.setenv("MEM0_API_KEY", "env-key")
+        (tmp_path / "mem0.json").write_text(
+            json.dumps({"api_key": "file-key"})
+        )
+
+        assert mem0_plugin._load_config()["api_key"] == "file-key"
+
     def test_default_mode_is_platform(self, monkeypatch, tmp_path):
         monkeypatch.setenv("HERMES_HOME", str(tmp_path))
         monkeypatch.setenv("MEM0_API_KEY", "test-key")
@@ -453,5 +507,3 @@ class TestSelfHostedConfig:
     def test_load_config_reads_mem0_host_env(self, monkeypatch):
         monkeypatch.setenv("MEM0_HOST", "http://localhost:8888")
         assert mem0_plugin._load_config()["host"] == "http://localhost:8888"
-
-