diff --git a/backend/app/contracts.py b/backend/app/contracts.py
index c44e885..9ec94e1 100644
--- a/backend/app/contracts.py
+++ b/backend/app/contracts.py
@@ -443,6 +443,7 @@ class ProviderPreset(Contract):
     name: str
     provider_type: ProviderType
     base_url: str
+    default_credential_id: str | None = None
     requires_credential: bool = True
 
 
diff --git a/backend/app/providers/credentials.py b/backend/app/providers/credentials.py
index 0340c3f..7430e6c 100644
--- a/backend/app/providers/credentials.py
+++ b/backend/app/providers/credentials.py
@@ -10,8 +10,17 @@ class CredentialResolver(Protocol):
 class EnvironmentCredentialResolver:
     """解析由桌面 Host 注入 Sidecar 进程的临时凭证上下文。"""
 
+    _development_aliases = {
+        "openai": "OPENAI_API_KEY",
+        "deepseek": "DEEPSEEK_API_KEY",
+    }
+
     def resolve(self, credential_id: str | None) -> str | None:
         if not credential_id:
             return None
         normalized = re.sub(r"[^A-Za-z0-9]", "_", credential_id).upper()
-        return os.getenv(f"AINOTE_CREDENTIAL_{normalized}")
+        injected = os.getenv(f"AINOTE_CREDENTIAL_{normalized}")
+        if injected:
+            return injected
+        alias = self._development_aliases.get(credential_id.lower())
+        return os.getenv(alias) if alias else None
diff --git a/backend/app/providers/factory.py b/backend/app/providers/factory.py
index e9f1947..38d1687 100644
--- a/backend/app/providers/factory.py
+++ b/backend/app/providers/factory.py
@@ -35,12 +35,14 @@ class ProviderFactory:
                 name="OpenAI",
                 provider_type=ProviderType.openai_chat,
                 base_url="https://api.openai.com/v1",
+                default_credential_id="openai",
             ),
             ProviderPreset(
                 preset_id="deepseek",
                 name="DeepSeek",
                 provider_type=ProviderType.openai_compatible,
                 base_url="https://api.deepseek.com",
+                default_credential_id="deepseek",
             ),
             ProviderPreset(
                 preset_id="ollama",
diff --git a/backend/app/providers/openai_compatible.py b/backend/app/providers/openai_compatible.py
index 24b07a3..11c9500 100644
--- a/backend/app/providers/openai_compatible.py
+++ b/backend/app/providers/openai_compatible.py
@@ -264,6 +264,11 @@ class OpenAICompatibleProvider(TurnStreamingMixin):
     def _headers(self) -> dict[str, str]:
         headers = {"Content-Type": "application/json"}
         api_key = self.credentials.resolve(self.credential_id)
+        if self.credential_id and not api_key:
+            raise ProviderError(
+                "PROVIDER_CREDENTIAL_MISSING",
+                f'Credential "{self.credential_id}" is not available in the AI Core process.',
+            )
         if api_key:
             headers["Authorization"] = f"Bearer {api_key}"
         return headers
diff --git a/backend/app/routes.py b/backend/app/routes.py
index 1fc1994..a14eccb 100644
--- a/backend/app/routes.py
+++ b/backend/app/routes.py
@@ -517,6 +517,7 @@ async def list_provider_models(provider_id: str) -> ProviderModelsResponse:
         models = await container.providers.list_models(provider_id)
     except ProviderError as exc:
         status_code = {
+            "PROVIDER_CREDENTIAL_MISSING": 422,
             "PROVIDER_AUTH_FAILED": 401,
             "MODEL_NOT_FOUND": 404,
             "PROVIDER_RATE_LIMITED": 429,
diff --git a/backend/tests/test_api.py b/backend/tests/test_api.py
index f107842..e7a825e 100644
--- a/backend/tests/test_api.py
+++ b/backend/tests/test_api.py
@@ -67,6 +67,7 @@ def test_provider_presets_include_openai_and_deepseek() -> None:
     assert by_id["openai"].base_url == "https://api.openai.com/v1"
     assert by_id["deepseek"].base_url == "https://api.deepseek.com"
     assert by_id["deepseek"].provider_type == ProviderType.openai_compatible
+    assert by_id["deepseek"].default_credential_id == "deepseek"
 
 
 def test_provider_presets_static_route_precedes_provider_id_route() -> None:
diff --git a/backend/tests/test_provider_adapters.py b/backend/tests/test_provider_adapters.py
index f6c5f45..781e818 100644
--- a/backend/tests/test_provider_adapters.py
+++ b/backend/tests/test_provider_adapters.py
@@ -12,6 +12,8 @@ from app.contracts import (
     ToolDefinition,
 )
 from app.providers.ollama import OllamaProvider
+from app.providers.base import ProviderError
+from app.providers.credentials import EnvironmentCredentialResolver
 from app.providers.openai_compatible import OpenAICompatibleProvider
 
 
@@ -156,6 +158,31 @@ def test_openai_compatible_fetches_and_maps_model_list() -> None:
     assert [item.model for item in models] == ["model-b", "model-a"]
 
 
+def test_environment_credentials_support_deepseek_development_alias(monkeypatch) -> None:
+    monkeypatch.setenv("DEEPSEEK_API_KEY", "secret-test-key")
+
+    assert EnvironmentCredentialResolver().resolve("deepseek") == "secret-test-key"
+
+
+def test_openai_compatible_rejects_missing_named_credential_before_request() -> None:
+    class EmptyCredentials:
+        def resolve(self, credential_id: str | None) -> str | None:
+            return None
+
+    provider = OpenAICompatibleProvider(
+        base_url="https://provider.test/v1",
+        credential_id="deepseek",
+        credentials=EmptyCredentials(),
+    )
+
+    try:
+        run(provider.list_models())
+    except ProviderError as error:
+        assert error.code == "PROVIDER_CREDENTIAL_MISSING"
+    else:
+        raise AssertionError("Missing credential should fail before the provider request")
+
+
 def test_ollama_maps_models_and_completion() -> None:
     def handler(request: httpx.Request) -> httpx.Response:
         if request.url.path == "/api/tags":