feat: defer entry spot derivation to backtest run (BT-005)

- Remove async refresh_workspace_seeded_units from date change handlers
- Date changes now only call on_form_change() (updates cost estimates, marks results stale)
- Entry spot is derived only when user clicks Run button
- Form remains responsive during configuration
- No more API errors when changing dates while configuring other fields

app/pages/backtests.py

@@ -5,7 +5,7 @@ from datetime import date, datetime
 from typing import TYPE_CHECKING, Any
 
 from fastapi.responses import RedirectResponse
-from nicegui import run, ui
+from nicegui import ui
 
 from app.domain.backtesting_math import asset_quantity_from_workspace_config
 from app.models.backtest import ProviderRef
@@ -784,32 +784,6 @@ def _render_backtests_page(workspace_id: str | None = None) -> None:
                 logger.warning(f"Failed to save backtest settings for workspace {workspace_id}: {e}")
                 return None
 
-        async def refresh_workspace_seeded_units() -> None:
-            """Derive entry spot asynchronously and update units when dates change."""
-            validation_label.set_text("")
-            progress_label.set_text("Fetching entry spot...")
-
-            try:
-                # Run derive_entry_spot in background thread
-                entry_spot, entry_error = await run.io_bound(derive_entry_spot)
-
-                if workspace_id and config is not None and config.gold_value is not None and entry_spot is not None:
-                    units_input.value = asset_quantity_from_workspace_config(
-                        config, entry_spot=entry_spot, symbol=get_symbol_from_dataset()
-                    )
-                update_cost_estimate()
-                render_seeded_summary(entry_spot=entry_spot, entry_spot_error=entry_error)
-                if entry_error:
-                    validation_label.set_text(entry_error)
-                    render_result_state("Scenario validation failed", entry_error, tone="warning")
-                    return
-                validation_error = validate_current_scenario(entry_spot=entry_spot)
-                if validation_error:
-                    validation_label.set_text(validation_error)
-                    render_result_state("Scenario validation failed", validation_error, tone="warning")
-            finally:
-                progress_label.set_text("")
-
         def on_form_change() -> None:
             """Handle form changes with minimal API calls."""
             validation_label.set_text("")
@@ -1061,13 +1035,14 @@ def _render_backtests_page(workspace_id: str | None = None) -> None:
                 update_cost_estimate()
 
         # Wire up event handlers
-        # Only call expensive derive_entry_spot on date changes
+        # Date changes should NOT trigger expensive derive_entry_spot API call
+        # Entry spot derivation happens when user clicks Run
         data_source_select.on_value_change(lambda e: on_form_change())
         dataset_select.on_value_change(lambda e: (update_date_range_hint(), on_form_change()))
         schema_select.on_value_change(lambda e: on_form_change())
         symbol_select.on_value_change(lambda e: update_date_range_hint())
-        start_input.on_value_change(lambda e: refresh_workspace_seeded_units())
+        start_input.on_value_change(lambda e: on_form_change())
-        end_input.on_value_change(lambda e: refresh_workspace_seeded_units())
+        end_input.on_value_change(lambda e: on_form_change())
         # Don't trigger API calls on these changes
         start_price_input.on_value_change(lambda e: mark_results_stale())
         template_select.on_value_change(lambda e: mark_results_stale())

docs/roadmap/ROADMAP.yaml

@@ -13,7 +13,6 @@ notes:
   - Pre-alpha policy: we may cut or replace old features without backward compatibility until alpha is declared.
   - Alpha migration policy: once alpha is declared, compatibility only needs to move forward; backward migrations are not required.
 priority_queue:
-  - BT-005
   - BT-004
   - EXEC-002
   - DATA-DB-005
@@ -25,6 +24,7 @@ priority_queue:
   - GCF-001
   - DATA-DB-006
 recently_completed:
+  - BT-005
   - CORE-003
   - CONV-001
   - DATA-DB-004
@@ -50,7 +50,6 @@ recently_completed:
   - CORE-002B
 states:
   backlog:
-    - BT-005
     - BT-004
     - DATA-DB-005
     - DATA-DB-006
@@ -63,6 +62,7 @@ states:
     - GCF-001
   in_progress: []
   done:
+    - BT-005
     - CORE-003
     - CONV-001
     - DATA-DB-003

docs/roadmap/done/BT-005-defer-entry-spot-derivation.yaml

@@ -1,6 +1,6 @@
 id: BT-005
 title: Defer Entry Spot Derivation to Backtest Run
-status: backlog
+status: done
 priority: P1
 effort: S
 depends_on: []
@@ -14,9 +14,7 @@ acceptance_criteria:
   - Clear loading indicator shows when entry spot is being fetched during run.
   - Previous entry spot value is retained until new one is derived.
 notes:
-  Current behavior calls derive_entry_spot on every date change which causes
+  Removed async refresh_workspace_seeded_units from date change handlers.
-  API errors if user is still configuring other fields.
+  Entry spot derivation now only happens inside run_read_only_scenario when
-  
+  the user clicks Run. Form changes now call on_form_change() which only
-  The refresh_workspace_seeded_units function should not be called on date changes.
+  updates cost estimates and marks results stale.
-  Entry spot derivation should happen inside start_backtest or as a separate
-  explicit "fetch spot" button if user wants to preview.