fix(settings): fail closed on blank loan input

app/pages/settings.py

@@ -53,20 +53,24 @@ def settings_page(workspace_id: str) -> None:
             return None
         return parsed if parsed > 0 else None
 
-    def as_non_negative_float(value: object) -> float:
+    def as_non_negative_float(value: object) -> float | None:
         try:
             parsed = float(value)
         except (TypeError, ValueError):
-            return 0.0
-        return max(parsed, 0.0)
+            return None
+        return parsed if parsed >= 0 else None
 
     def build_preview_config() -> PortfolioConfig:
+        parsed_loan_amount = as_non_negative_float(loan_amount.value)
+        if parsed_loan_amount is None:
+            raise ValueError("Loan amount must be zero or greater")
+
         return PortfolioConfig(
             gold_value=as_positive_float(gold_value.value),
             entry_price=as_positive_float(entry_price.value),
             gold_ounces=as_positive_float(gold_ounces.value),
             entry_basis_mode=str(entry_basis_mode.value),
-            loan_amount=as_non_negative_float(loan_amount.value),
+            loan_amount=parsed_loan_amount,
             margin_threshold=float(margin_threshold.value),
             monthly_budget=float(monthly_budget.value),
             ltv_warning=float(ltv_warning.value),
@@ -125,12 +129,14 @@ def settings_page(workspace_id: str) -> None:
                     step=0.01,
                 ).classes("w-full")
 
-                loan_amount = ui.number(
-                    "Loan amount ($)",
-                    value=config.loan_amount,
-                    min=0,
-                    step=1000,
-                ).classes("w-full")
+                loan_amount = (
+                    ui.input(
+                        "Loan amount ($)",
+                        value=str(config.loan_amount),
+                    )
+                    .props("type=number min=0 step=1000")
+                    .classes("w-full")
+                )
 
                 margin_threshold = ui.number(
                     "Margin call LTV threshold",
@@ -337,7 +343,7 @@ def settings_page(workspace_id: str) -> None:
             loan = as_non_negative_float(loan_amount.value)
             margin = as_positive_float(margin_threshold.value)
 
-            if collateral_value is not None and collateral_value > 0:
+            if collateral_value is not None and collateral_value > 0 and loan is not None:
                 ltv = (loan / collateral_value) * 100
                 buffer = ((margin or 0.0) - loan / collateral_value) * 100 if margin is not None else 0.0
                 ltv_display.set_text(f"{ltv:.1f}%")
@@ -346,9 +352,15 @@ def settings_page(workspace_id: str) -> None:
                 ltv_display.set_text("—")
                 buffer_display.set_text("—")
 
-            if margin is not None and ounces is not None and ounces > 0:
+            if loan is not None and margin is not None and ounces is not None and ounces > 0:
                 margin_price_display.set_text(f"${loan / (margin * ounces):,.2f}/oz")
-            elif margin is not None and price is not None and collateral_value is not None and collateral_value > 0:
+            elif (
+                loan is not None
+                and margin is not None
+                and price is not None
+                and collateral_value is not None
+                and collateral_value > 0
+            ):
                 implied_ounces = collateral_value / price
                 margin_price_display.set_text(f"${loan / (margin * implied_ounces):,.2f}/oz")
             else:

docs/roadmap/done/CORE-001D3A-alerts-settings-entrypoint-normalization.yaml

@@ -17,4 +17,5 @@ completed_notes:
   - Alert evaluation now compares thresholds through normalized Decimal-backed boundary values instead of ad-hoc `float(...)` extraction.
   - Settings save-status formatting now snapshots numeric boundary values through a named adapter before rendering.
   - Added focused regression tests for numeric-string coercion and bool fail-closed behavior in `tests/test_alerts.py` and `tests/test_settings.py`.
+  - Hardened `/{workspace_id}/settings` so blank loan input no longer silently saves as a zero-loan portfolio; the loan field now preserves blank state until validation and has a focused Playwright regression in `tests/test_settings_validation_playwright.py`.
   - Validated with focused pytest coverage, browser-visible Playwright coverage, and `make build` on local Docker.

tests/test_settings_validation_playwright.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from playwright.sync_api import expect, sync_playwright
+
+BASE_URL = "http://127.0.0.1:8000"
+
+
+def test_settings_reject_invalid_loan_amount_without_silent_zero_fallback() -> None:
+    with sync_playwright() as p:
+        browser = p.chromium.launch(headless=True)
+        page = browser.new_page(viewport={"width": 1440, "height": 1000})
+
+        page.goto(BASE_URL, wait_until="domcontentloaded", timeout=30000)
+        expect(page.locator("text=Create a private workspace URL").first).to_be_visible(timeout=10000)
+        page.get_by_role("button", name="Get started").click()
+        page.wait_for_url(f"{BASE_URL}/*", timeout=15000)
+        workspace_url = page.url
+
+        page.goto(f"{workspace_url}/settings", wait_until="domcontentloaded", timeout=30000)
+        expect(page.locator("text=Settings").first).to_be_visible(timeout=15000)
+        loan_input = page.get_by_label("Loan amount ($)")
+        loan_input.fill("")
+        loan_input.press("Tab")
+
+        expect(page.locator("text=INVALID").first).to_be_visible(timeout=15000)
+        expect(page.locator("text=Loan amount must be zero or greater").first).to_be_visible(timeout=15000)
+
+        page.get_by_role("button", name="Save settings").click()
+        expect(page.locator("text=Validation error: Loan amount must be zero or greater").first).to_be_visible(
+            timeout=15000
+        )
+
+        settings_text = page.locator("body").inner_text(timeout=15000)
+        assert "LTV=0.0%" not in settings_text
+        assert "RuntimeError" not in settings_text
+        assert "Server error" not in settings_text
+        assert "Traceback" not in settings_text
+
+        browser.close()