Use direct DeepSeek as default model

.env.example

@@ -1,7 +1,7 @@
 # To run the AI Tutor app (FastAPI backend)
-# Default chat path: DeepSeek V4 Flash through OpenRouter, with Gemini 2.5
-# Flash as the local application fallback if the OpenRouter call fails.
-OPENROUTER_API_KEY=...
+# Default chat path: DeepSeek V4 Flash through the first-party DeepSeek API,
+# with Gemini 2.5 Flash as the local application fallback if DeepSeek fails.
+DEEPSEEK_API_KEY=...
 GEMINI_API_KEY=...
 # Gemini also accepts GOOGLE_API_KEY instead of GEMINI_API_KEY.
 GOOGLE_API_KEY=...
@@ -10,8 +10,7 @@ GOOGLE_API_KEY=...
 OPENAI_API_KEY=...
 ANTHROPIC_API_KEY=...
 COHERE_API_KEY=...
-# DEEPSEEK_API_KEY hits the first-party DeepSeek API (not the default path).
-DEEPSEEK_API_KEY=...
+OPENROUTER_API_KEY=...
 
 # Optional: trace agent/model/tool runs in LangSmith
 LANGSMITH_API_KEY=...

README.md

@@ -48,7 +48,7 @@ Want to build this AI tutor yourself, end to end? Our [**Full Stack AI Engineer
    cp .env.example .env  # then edit values
    ```
 
-   The chat model is provider-agnostic, configured in `provider:model` format. The default is `openrouter:deepseek/deepseek-v4-flash`, which uses OpenRouter first and falls back in-app to `google-genai:gemini-2.5-flash` when a Gemini key is configured. Set `OPENROUTER_API_KEY` plus `GEMINI_API_KEY` or `GOOGLE_API_KEY` for the default path. Optional provider keys include `OPENAI_API_KEY`, `ANTHROPIC_API_KEY`, and `DEEPSEEK_API_KEY` for non-default provider paths.
+   The chat model is provider-agnostic, configured in `provider:model` format. The default is `deepseek:deepseek-v4-flash`, which uses DeepSeek's first-party API and falls back in-app to `google-genai:gemini-2.5-flash` when a Gemini key is configured. Set `DEEPSEEK_API_KEY` plus `GEMINI_API_KEY` or `GOOGLE_API_KEY` for the default path. Optional provider keys include `OPENAI_API_KEY`, `ANTHROPIC_API_KEY`, and `OPENROUTER_API_KEY` for non-default provider paths.
    To trace requests in LangSmith, set `LANGSMITH_API_KEY`. The app enables tracing automatically when that key is present unless `LANGSMITH_TRACING=false` is set.
 
 ### LangSmith Agent Tracing

app/chat_service.py

@@ -72,7 +72,7 @@ from .provider_events import (
 from .config import (
     BM25_INDEX_PATH,
     COURSE_SOURCE_KEYS,
-    DEEPSEEK_OPENROUTER_MODEL_NAME,
+    DEEPSEEK_DIRECT_MODEL_NAME,
     DEFAULT_SELECTED_SOURCE_KEYS,
     DOCUMENT_DICT_PATH,
     GEMINI_FALLBACK_MODEL_NAME,
@@ -793,8 +793,8 @@ def _has_google_genai_key() -> bool:
     return bool(os.environ.get("GOOGLE_API_KEY") or os.environ.get("GEMINI_API_KEY"))
 
 
-def _has_openrouter_key() -> bool:
-    return bool(os.environ.get("OPENROUTER_API_KEY"))
+def _has_deepseek_key() -> bool:
+    return bool(os.environ.get("DEEPSEEK_API_KEY"))
 
 
 def _build_chat_model_client(provider_model: str, include_thoughts: bool = False):
@@ -898,15 +898,15 @@ def _build_chat_model_client(provider_model: str, include_thoughts: bool = False
 
 def build_chat_model(model_name: str, include_thoughts: bool = False):
     provider_model = normalize_model_name(model_name)
-    if provider_model != DEEPSEEK_OPENROUTER_MODEL_NAME:
+    if provider_model != DEEPSEEK_DIRECT_MODEL_NAME:
         return _build_chat_model_client(
             provider_model,
             include_thoughts=include_thoughts,
         )
-    if not _has_openrouter_key() and _has_google_genai_key():
+    if not _has_deepseek_key() and _has_google_genai_key():
         logger.warning(
-            "No OPENROUTER_API_KEY is set for %s; using Gemini fallback %s.",
-            DEEPSEEK_OPENROUTER_MODEL_NAME,
+            "No DEEPSEEK_API_KEY is set for %s; using Gemini fallback %s.",
+            DEEPSEEK_DIRECT_MODEL_NAME,
             GEMINI_FALLBACK_MODEL_NAME,
         )
         return _build_chat_model_client(
@@ -917,9 +917,9 @@ def build_chat_model(model_name: str, include_thoughts: bool = False):
     if not _has_google_genai_key():
         logger.warning(
             "Gemini fallback %s is configured for %s, but no GOOGLE_API_KEY or "
-            "GEMINI_API_KEY is set; using OpenRouter only.",
+            "GEMINI_API_KEY is set; using DeepSeek only.",
             GEMINI_FALLBACK_MODEL_NAME,
-            DEEPSEEK_OPENROUTER_MODEL_NAME,
+            DEEPSEEK_DIRECT_MODEL_NAME,
         )
         return model
     fallback = _build_chat_model_client(

app/config.py

@@ -69,14 +69,14 @@ KB_INDEX_PATH = f"{KB_DIR}/wiki/index.md"
 KB_AGENTS_PATH = f"{KB_DIR}/AGENTS.md"
 # In-git template, copied into data/kb/AGENTS.md by ensure_kb_agents_md().
 KB_AGENTS_TEMPLATE_PATH = "data/scraping_scripts/kb_agents_template.md"
-DEEPSEEK_OPENROUTER_MODEL_NAME = "openrouter:deepseek/deepseek-v4-flash"
+DEEPSEEK_DIRECT_MODEL_NAME = "deepseek:deepseek-v4-flash"
 GEMINI_FALLBACK_MODEL_NAME = "google-genai:gemini-2.5-flash"
-DEFAULT_MODEL_NAME = DEEPSEEK_OPENROUTER_MODEL_NAME
+DEFAULT_MODEL_NAME = DEEPSEEK_DIRECT_MODEL_NAME
 
 AVAILABLE_MODELS: tuple[dict[str, str], ...] = (
     {
-        "id": DEEPSEEK_OPENROUTER_MODEL_NAME,
-        "label": "DeepSeek V4 Flash (OpenRouter)",
+        "id": DEEPSEEK_DIRECT_MODEL_NAME,
+        "label": "DeepSeek V4 Flash",
     },
     {"id": GEMINI_FALLBACK_MODEL_NAME, "label": "Gemini 2.5 Flash"},
     {"id": "anthropic:claude-haiku-4-5", "label": "Claude Haiku 4.5"},
@@ -270,7 +270,7 @@ __all__ = [
     "DEFAULT_SELECTED_SOURCE_KEYS",
     "DEFAULT_SELECTED_SOURCES_UI",
     "DEFAULT_MODEL_NAME",
-    "DEEPSEEK_OPENROUTER_MODEL_NAME",
+    "DEEPSEEK_DIRECT_MODEL_NAME",
     "GEMINI_FALLBACK_MODEL_NAME",
     "BM25_INDEX_PATH",
     "DOCUMENT_DICT_PATH",

tests/manual_e2e_langsmith.md

@@ -13,7 +13,7 @@ Run commands from the repository root.
 Required local artifacts and environment:
 
 - `.env` contains `COHERE_API_KEY`
-- `.env` contains `OPENROUTER_API_KEY`
+- `.env` contains `DEEPSEEK_API_KEY`
 - `.env` contains `GEMINI_API_KEY` or `GOOGLE_API_KEY`
 - `.env` contains `LANGSMITH_API_KEY`
 - `.env` has `LANGSMITH_TRACING=true`
@@ -29,7 +29,7 @@ uv run dotenv -f .env run -- python - <<'PY'
 import os
 for key in [
     "COHERE_API_KEY",
-    "OPENROUTER_API_KEY",
+    "DEEPSEEK_API_KEY",
     "GEMINI_API_KEY",
     "GOOGLE_API_KEY",
     "LANGSMITH_API_KEY",
@@ -95,7 +95,7 @@ cat >/tmp/ai_tutor_e2e_payload.json <<'JSON'
     "transformers"
   ],
   "enabledTools": [],
-  "model": "openrouter:deepseek/deepseek-v4-flash",
+  "model": "deepseek:deepseek-v4-flash",
   "includeReasoning": true,
   "threadId": ""
 }

tests/test_api.py

@@ -75,8 +75,8 @@ class ApiTestCase(unittest.TestCase):
         )
         self.assertEqual(transformers["label"], "Transformers Docs")
         self.assertEqual(transformers["shortLabel"], "Transformers")
-        self.assertEqual(body["model"], "openrouter:deepseek/deepseek-v4-flash")
-        # DeepSeek via OpenRouter is the default model, so only local KB tools
+        self.assertEqual(body["model"], "deepseek:deepseek-v4-flash")
+        # DeepSeek direct is the default model, so only local KB tools
         # are exposed until a provider with built-in web tools is selected.
         tool_keys = {tool["key"] for tool in tools}
         self.assertNotIn("web_search", tool_keys)
@@ -958,7 +958,7 @@ def live_chat_payload(
         "sourceKeys": ["peft", "transformers"],
         "enabledTools": enabled_tools or [],
         "model": os.getenv(
-            "LIVE_API_E2E_MODEL", "openrouter:deepseek/deepseek-v4-flash"
+            "LIVE_API_E2E_MODEL", "deepseek:deepseek-v4-flash"
         ),
         "includeReasoning": False,
         "threadId": thread_id,

tests/test_chat_service.py

@@ -9,7 +9,7 @@ from unittest.mock import MagicMock, patch
 from langchain_core.messages import AIMessage, AIMessageChunk, HumanMessage, ToolMessage
 from langchain_core.runnables.fallbacks import RunnableWithFallbacks
 
-from app.config import DEEPSEEK_OPENROUTER_MODEL_NAME, GEMINI_FALLBACK_MODEL_NAME
+from app.config import DEEPSEEK_DIRECT_MODEL_NAME, GEMINI_FALLBACK_MODEL_NAME
 from app.chat_service import (
     THREAD_IDLE_TTL_SECONDS,
     _claim_kb_command_budget,
@@ -318,39 +318,40 @@ class ChatServiceTestCase(unittest.TestCase):
         self.assertGreater(reasoning.max_tokens, 8192)
         self.assertEqual(reasoning.thinking, {"type": "enabled", "budget_tokens": 2048})
 
-    def test_deepseek_openrouter_default_has_gemini_fallback(self) -> None:
+    def test_deepseek_direct_default_has_gemini_fallback(self) -> None:
         with patch.dict(
             os.environ,
             {
-                "OPENROUTER_API_KEY": "openrouter-test-key",
+                "DEEPSEEK_API_KEY": "deepseek-test-key",
                 "GEMINI_API_KEY": "gemini-test-key",
             },
             clear=True,
         ):
-            model = build_chat_model(DEEPSEEK_OPENROUTER_MODEL_NAME)
+            model = build_chat_model(DEEPSEEK_DIRECT_MODEL_NAME)
 
         self.assertIsInstance(model, RunnableWithFallbacks)
-        self.assertEqual(model.runnable.model_name, "deepseek/deepseek-v4-flash")
+        self.assertEqual(model.runnable.model_name, "deepseek-v4-flash")
+        self.assertEqual(str(model.runnable.openai_api_base), "https://api.deepseek.com")
         self.assertEqual(len(model.fallbacks), 1)
         self.assertEqual(
             model.fallbacks[0].model,
             GEMINI_FALLBACK_MODEL_NAME.partition(":")[2],
         )
 
-    def test_deepseek_openrouter_default_skips_fallback_without_gemini_key(
+    def test_deepseek_direct_default_skips_fallback_without_gemini_key(
         self,
     ) -> None:
         with patch.dict(
             os.environ,
-            {"OPENROUTER_API_KEY": "openrouter-test-key"},
+            {"DEEPSEEK_API_KEY": "deepseek-test-key"},
             clear=True,
         ):
-            model = build_chat_model(DEEPSEEK_OPENROUTER_MODEL_NAME)
+            model = build_chat_model(DEEPSEEK_DIRECT_MODEL_NAME)
 
         self.assertNotIsInstance(model, RunnableWithFallbacks)
-        self.assertEqual(model.model_name, "deepseek/deepseek-v4-flash")
+        self.assertEqual(model.model_name, "deepseek-v4-flash")
 
-    def test_deepseek_openrouter_default_uses_gemini_when_openrouter_key_missing(
+    def test_deepseek_direct_default_uses_gemini_when_deepseek_key_missing(
         self,
     ) -> None:
         with patch.dict(
@@ -358,7 +359,7 @@ class ChatServiceTestCase(unittest.TestCase):
             {"GEMINI_API_KEY": "gemini-test-key"},
             clear=True,
         ):
-            model = build_chat_model(DEEPSEEK_OPENROUTER_MODEL_NAME)
+            model = build_chat_model(DEEPSEEK_DIRECT_MODEL_NAME)
 
         self.assertNotIsInstance(model, RunnableWithFallbacks)
         self.assertEqual(model.model, GEMINI_FALLBACK_MODEL_NAME.partition(":")[2])

tests/test_config.py

@@ -11,9 +11,9 @@ import pytest
 from app import config
 
 
-def test_default_chat_model_prefers_deepseek_openrouter_with_gemini_fallback() -> None:
-    assert config.DEFAULT_MODEL_NAME == config.DEEPSEEK_OPENROUTER_MODEL_NAME
-    assert config.DEFAULT_MODEL_NAME == "openrouter:deepseek/deepseek-v4-flash"
+def test_default_chat_model_prefers_deepseek_direct_with_gemini_fallback() -> None:
+    assert config.DEFAULT_MODEL_NAME == config.DEEPSEEK_DIRECT_MODEL_NAME
+    assert config.DEFAULT_MODEL_NAME == "deepseek:deepseek-v4-flash"
     assert config.GEMINI_FALLBACK_MODEL_NAME == "google-genai:gemini-2.5-flash"
     assert config.AVAILABLE_MODELS[0]["id"] == config.DEFAULT_MODEL_NAME
     assert any(