behavior-stable-filter-foundation

name	behavior-stable-filter-foundation
description	Extract shared filter and loading primitives without changing HTMX or handler contracts.
domain	htmx-migration
confidence	high
source	earned

Context

Use this when several Razor Pages repeat the same filter card and loading overlay structure, but the migration must not disturb existing HTMX request flow or PageModel expectations.

Patterns

• Keep the slice view-only when possible: prefer shared partial markup and CSS helpers over handler or route changes.
• Preserve every existing hx-get, hx-target, hx-include, hx-push-url, route, and query parameter name.
• Reuse a shared loading partial inside the existing #loading-indicator wrapper so indicator IDs and HTMX hooks remain unchanged.
• Standardize filter card structure with additive CSS classes (filter-shell, filter-card, filter-row, filter-actions) instead of changing request wiring.
• Add hx-indicator only to existing filter triggers that already hit the same handler/target.
• Backstop with page-routing integration tests that assert full-page responses still render the filter host and HTMX requests still return only the list partial.

Examples

• baseball-history-web/Pages/Awards/Index.cshtml
• baseball-history-web/Pages/Postseason/Index.cshtml
• baseball-history-web/Pages/Salaries/Index.cshtml
• baseball-history-web/Pages/HallOfFame/Index.cshtml
• baseball-history-web/Pages/Shared/Components/_LoadingSpinner.cshtml
• baseball-history-web/wwwroot/css/site.css

Anti-Patterns

• Do not rename indicator IDs, list target IDs, routes, or query parameters as part of a cosmetic primitive pass.
• Do not move filter behavior into new handlers unless the existing request contracts are explicitly being redesigned.
• Do not fold pagination, modal host, alphabet navigation, or search host work into the same slice.