Add a reasoning-off setting (-1 reasoning budget)

Models like DeepSeek V4 Flash reason by default, and the reasoning budget
setting could only ever add thinking tokens - there was no value that turned
thinking off. A negative budget now sends `reasoning: {effort: "none"}`.

Uses effort:none rather than exclude:true deliberately - exclude still thinks
and still bills, it only hides the trace.

Zero keeps its old meaning (send no `reasoning` field at all) so endpoints that
reject unknown fields, like the default Ollama one, are unaffected. Reusing the
existing int column this way avoids a migration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UeQVy5bEjLhfgWNc27Efet

backend/app/models.py

@@ -307,7 +307,8 @@ class Settings(Base):
     # and left reasoning models with nothing after their thinking.
     max_output_tokens: Mapped[int] = mapped_column(Integer, default=800)
     # Separate thinking budget for reasoning models (OpenRouter-style
-    # `reasoning: {max_tokens}`); 0 = param not sent. Added on top of
+    # `reasoning: {max_tokens}`); 0 = param not sent, -1 = reasoning explicitly
+    # off (`reasoning: {effort: none}`). Added on top of
     # max_output_tokens so story output keeps its full budget.
     reasoning_max_tokens: Mapped[int] = mapped_column(Integer, default=0)
     context_token_budget: Mapped[int] = mapped_column(Integer, default=16384)

backend/app/providers/openai_compatible.py

@@ -39,7 +39,8 @@ class OpenAICompatibleProvider(Provider):
         self.api_mode = api_mode  # "chat" | "completion"
         # Thinking budget for reasoning models, on top of max_tokens. 0 = the
         # `reasoning` param is not sent (endpoints that don't know it may
-        # reject unknown fields).
+        # reject unknown fields); negative = explicitly ask the endpoint to
+        # turn reasoning off.
         self.reasoning_max_tokens = reasoning_max_tokens
 
     def _headers(self) -> dict:
@@ -50,8 +51,18 @@ class OpenAICompatibleProvider(Provider):
 
     def _apply_reasoning_budget(self, body: dict) -> None:
         """Give reasoning models their own thinking budget (OpenRouter-style),
-        raising max_tokens so the actual output keeps its full budget."""
-        if self.reasoning_max_tokens > 0 and self.api_mode == "chat":
+        raising max_tokens so the actual output keeps its full budget.
+
+        A negative budget means the opposite: send `effort: "none"` to switch
+        reasoning off on models that do it by default (DeepSeek V4 Flash, say).
+        That's distinct from `exclude: true`, which still thinks — and bills —
+        but hides the trace. Zero stays "send nothing at all" so endpoints that
+        reject unknown fields (Ollama) keep working."""
+        if self.api_mode != "chat":
+            return
+        if self.reasoning_max_tokens < 0:
+            body["reasoning"] = {"effort": "none"}
+        elif self.reasoning_max_tokens > 0:
             body["reasoning"] = {"max_tokens": self.reasoning_max_tokens}
             body["max_tokens"] += self.reasoning_max_tokens
 

backend/app/schemas.py

@@ -375,7 +375,8 @@ class SettingsUpdate(BaseModel):
     api_mode: Annotated[str, Field(max_length=20)] | None = None
     temperature: Annotated[float, Field(ge=0, le=5)] | None = None
     max_output_tokens: Annotated[int, Field(ge=1, le=100_000)] | None = None
-    reasoning_max_tokens: Annotated[int, Field(ge=0, le=100_000)] | None = None
+    # -1 = explicitly off (sends `reasoning: {effort: none}`); 0 = send nothing.
+    reasoning_max_tokens: Annotated[int, Field(ge=-1, le=100_000)] | None = None
     context_token_budget: Annotated[int, Field(ge=256, le=200_000)] | None = None
     narrator_prompt: Prose | None = None
     stream: bool | None = None

backend/tests/test_reasoning_param.py

@@ -0,0 +1,45 @@
+"""What the provider puts in the `reasoning` request field for each budget
+setting: a positive budget asks for thinking, 0 stays silent, -1 turns it off.
+
+    python -m pytest tests/test_reasoning_param.py -v
+"""
+from app.providers.openai_compatible import OpenAICompatibleProvider
+
+
+def _body(reasoning_max_tokens, api_mode="chat", max_tokens=1000):
+    provider = OpenAICompatibleProvider(
+        "https://openrouter.ai/api/v1", "k", "deepseek/deepseek-v4-flash-0731",
+        api_mode, reasoning_max_tokens,
+    )
+    body = {"max_tokens": max_tokens}
+    provider._apply_reasoning_budget(body)
+    return body
+
+
+def test_zero_sends_nothing():
+    """Ollama and friends reject unknown fields — 0 must stay silent."""
+    assert "reasoning" not in _body(0)
+
+
+def test_positive_budget_adds_thinking_tokens():
+    body = _body(500)
+    assert body["reasoning"] == {"max_tokens": 500}
+    # the story output keeps its own full budget on top of the thinking budget
+    assert body["max_tokens"] == 1500
+
+
+def test_negative_turns_reasoning_off():
+    body = _body(-1)
+    assert body["reasoning"] == {"effort": "none"}
+    # "off" must not inflate the output budget
+    assert body["max_tokens"] == 1000
+
+
+def test_off_is_not_merely_excluded():
+    """`exclude: true` still thinks and still bills; we want it actually off."""
+    assert _body(-1)["reasoning"].get("exclude") is None
+
+
+def test_completion_mode_never_sends_reasoning():
+    for budget in (-1, 0, 500):
+        assert "reasoning" not in _body(budget, api_mode="completion")

frontend/src/pages/Settings.jsx

@@ -167,12 +167,15 @@ export default function Settings() {
       </div>
       <label className="field">
         <span className="label">Reasoning budget (tokens)</span>
-        <input type="number" min="0" value={settings.reasoning_max_tokens}
-          onChange={(e) => setField('reasoning_max_tokens', Number(e.target.value))} />
+        <input type="number" min="-1" value={settings.reasoning_max_tokens}
+          onChange={(e) => setField(
+            'reasoning_max_tokens', Math.max(-1, Number(e.target.value)))} />
         <span className="label" style={{ marginTop: 4 }}>
           For reasoning models: separate thinking budget on top of max output tokens,
-          and thinking is shown collapsed above each response. 0 = off (nothing extra
-          is sent — keep 0 for endpoints/models without reasoning support).
+          and thinking is shown collapsed above each response. 0 = nothing extra is
+          sent (keep 0 for endpoints without reasoning support, e.g. Ollama).
+          −1 = actively turn reasoning off, for models that think by default
+          (DeepSeek V4 Flash) — saves the thinking tokens rather than just hiding them.
         </span>
       </label>