fix(frontend): stop a cleared number field being read as zero

frontend/src/features/settings/SettingsPanel.test.tsx

@@ -355,4 +355,102 @@ describe("SettingsPanel", () => {
     expect(screen.getByRole("status")).toHaveTextContent("Save the folder setting before downloading");
     expect(onDownloadGGUF).not.toHaveBeenCalled();
   });
+  it("does not read a cleared number field as zero", async () => {
+    // Number("") is 0. Clearing a field to retype it wrote a real zero into
+    // the draft: below the server's minimum for the context window, and for
+    // the seed a *valid* value that silently turned "-1, keep replies varied"
+    // into a pinned seed.
+    const user = userEvent.setup();
+    const onSave = vi.fn<(settings: CortexSettings) => Promise<void>>().mockResolvedValue();
+    const settings: CortexSettings = {
+      models: { chat: "local-chat:7b", title: null, translation: "translategemma:4b" },
+      generation: { temperature: 0.7, num_ctx: 4096, seed: -1, system_instructions: "", bypass_system_prompt: false },
+    };
+    const models: ModelResponse = {
+      required_models: [],
+      optional_models: [],
+      installed_models: ["local-chat:7b"],
+      models: [{ name: "local-chat:7b" }],
+      connection: { success: true, status: "connected", message: "Connected." },
+    };
+    render(
+      <SettingsPanel
+        settings={settings}
+        memos={[]}
+        saving={false}
+        memoryBusy={false}
+        onSave={onSave}
+        onAddMemory={vi.fn<(memo: string) => Promise<void>>().mockResolvedValue()}
+        onReplaceMemory={vi.fn<(memos: string[]) => Promise<void>>().mockResolvedValue()}
+        onClearMemory={vi.fn<() => Promise<void>>().mockResolvedValue()}
+        models={models}
+        modelBusy={false}
+        modelProgress={null}
+        setupUrl="https://ollama.com/download"
+        onCheckModels={vi.fn<() => Promise<void>>().mockResolvedValue()}
+        onPullModel={vi.fn<(model: string) => Promise<void>>().mockResolvedValue()}
+        llamacppStatus={{ state: "idle", binary_present: false, loaded_model: null, last_error: null, models_directory: "" }}
+        onDownloadGGUF={vi.fn().mockResolvedValue(undefined)}
+        onClose={vi.fn()}
+      />,
+    );
+
+    await user.click(screen.getByRole("button", { name: /AI Model/ }));
+    await user.clear(screen.getByLabelText("Context window"));
+    await user.clear(screen.getByLabelText("Seed"));
+    await user.click(screen.getByRole("button", { name: "Save settings" }));
+
+    await waitFor(() => expect(onSave).toHaveBeenCalled());
+    expect(onSave).toHaveBeenCalledWith(expect.objectContaining({
+      generation: expect.objectContaining({ num_ctx: 4096, seed: -1 }),
+    }));
+  });
+
+  it("still accepts a retyped number", async () => {
+    const user = userEvent.setup();
+    const onSave = vi.fn<(settings: CortexSettings) => Promise<void>>().mockResolvedValue();
+    const settings: CortexSettings = {
+      models: { chat: "local-chat:7b", title: null, translation: "translategemma:4b" },
+      generation: { temperature: 0.7, num_ctx: 4096, seed: -1, system_instructions: "", bypass_system_prompt: false },
+    };
+    const models: ModelResponse = {
+      required_models: [],
+      optional_models: [],
+      installed_models: ["local-chat:7b"],
+      models: [{ name: "local-chat:7b" }],
+      connection: { success: true, status: "connected", message: "Connected." },
+    };
+    render(
+      <SettingsPanel
+        settings={settings}
+        memos={[]}
+        saving={false}
+        memoryBusy={false}
+        onSave={onSave}
+        onAddMemory={vi.fn<(memo: string) => Promise<void>>().mockResolvedValue()}
+        onReplaceMemory={vi.fn<(memos: string[]) => Promise<void>>().mockResolvedValue()}
+        onClearMemory={vi.fn<() => Promise<void>>().mockResolvedValue()}
+        models={models}
+        modelBusy={false}
+        modelProgress={null}
+        setupUrl="https://ollama.com/download"
+        onCheckModels={vi.fn<() => Promise<void>>().mockResolvedValue()}
+        onPullModel={vi.fn<(model: string) => Promise<void>>().mockResolvedValue()}
+        llamacppStatus={{ state: "idle", binary_present: false, loaded_model: null, last_error: null, models_directory: "" }}
+        onDownloadGGUF={vi.fn().mockResolvedValue(undefined)}
+        onClose={vi.fn()}
+      />,
+    );
+
+    await user.click(screen.getByRole("button", { name: /AI Model/ }));
+    const seed = screen.getByLabelText("Seed");
+    await user.clear(seed);
+    await user.type(seed, "42");
+    await user.click(screen.getByRole("button", { name: "Save settings" }));
+
+    await waitFor(() => expect(onSave).toHaveBeenCalled());
+    expect(onSave).toHaveBeenCalledWith(expect.objectContaining({
+      generation: expect.objectContaining({ seed: 42 }),
+    }));
+  });
 });

frontend/src/features/settings/SettingsPanel.tsx

@@ -87,6 +87,23 @@ const sections: { id: SettingsSection; label: string; detail: string }[] = [
   { id: "system", label: "System", detail: "Runtime and installed models" },
 ];
 
+type NumericField = "num_ctx" | "seed";
+
+/**
+ * Read a number input, or null when it holds nothing usable.
+ *
+ * `Number("")` is 0, so clearing a field to retype it used to write a real
+ * zero into the draft. For the context window that is below the server's
+ * minimum and the save was rejected; for the seed it is a *valid* value, so
+ * it silently turned "-1, keep replies varied" into a pinned seed. An empty
+ * field means the user is mid-edit, not that they chose zero.
+ */
+function readNumericInput(raw: string): number | null {
+  if (raw.trim() === "") return null;
+  const value = Number(raw);
+  return Number.isFinite(value) ? value : null;
+}
+
 export function SettingsPanel({
   settings,
   memos,
@@ -132,6 +149,29 @@ export function SettingsPanel({
 
   const update = (next: Partial<CortexSettings>) => setDraft((current) => ({ ...current, ...next }));
 
+  // What the user has literally typed into a number field, while they are
+  // typing it. The saved settings hold numbers, so a field bound straight to
+  // them can never be empty -- clearing it to retype snapped the old value
+  // back and the new digits appended to it ("-1" + "42" = -142). Keeping the
+  // raw text lets the box be empty mid-edit without ever writing a number
+  // nobody chose; `commitNumber` drops the override on blur so the field
+  // re-syncs to whatever was actually saved.
+  const [numericInputs, setNumericInputs] = useState<Partial<Record<NumericField, string>>>({});
+
+  const editNumber = (field: NumericField, raw: string, commit: (value: number) => void) => {
+    setNumericInputs((current) => ({ ...current, [field]: raw }));
+    const value = readNumericInput(raw);
+    if (value !== null) commit(value);
+  };
+
+  const commitNumber = (field: NumericField) =>
+    setNumericInputs((current) => {
+      if (current[field] === undefined) return current;
+      const next = { ...current };
+      delete next[field];
+      return next;
+    });
+
   const chooseChatModel = (chat: string) => update({ models: { ...modelSettings, chat, title: null } });
 
   const setTranslationEnabled = (enabled: boolean) => {
@@ -268,10 +308,27 @@ export function SettingsPanel({
                 </div>
                 <div className="settings-field-row">
                   <label className="field-label" htmlFor="num-ctx">Context window
-                    <input id="num-ctx" type="number" min="2048" max="65536" step="1024" value={generation.num_ctx ?? 8192} onChange={(event) => update({ generation: { ...generation, num_ctx: Number(event.target.value) } })} />
+                    <input
+                      id="num-ctx"
+                      type="number"
+                      min="2048"
+                      max="65536"
+                      step="1024"
+                      value={numericInputs.num_ctx ?? String(generation.num_ctx ?? 8192)}
+                      onChange={(event) => editNumber("num_ctx", event.target.value, (num_ctx) => update({ generation: { ...generation, num_ctx } }))}
+                      onBlur={() => commitNumber("num_ctx")}
+                    />
                   </label>
                   <label className="field-label" htmlFor="seed">Seed
-                    <input id="seed" type="number" min="-1" max="2147483647" value={generation.seed ?? -1} onChange={(event) => update({ generation: { ...generation, seed: Number(event.target.value) } })} />
+                    <input
+                      id="seed"
+                      type="number"
+                      min="-1"
+                      max="2147483647"
+                      value={numericInputs.seed ?? String(generation.seed ?? -1)}
+                      onChange={(event) => editNumber("seed", event.target.value, (seed) => update({ generation: { ...generation, seed } }))}
+                      onBlur={() => commitNumber("seed")}
+                    />
                   </label>
                 </div>