diff --git a/CLAUDE.md b/CLAUDE.md
index 52db8d2..b7b7687 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -498,6 +498,15 @@ and `details()` (mobile/tablet `<details>` accordion). Both call the
 same internal `facet_form()` so the controls stay identical across
 viewports — only the wrapper differs.
 
+Macros take TWO base URLs: `base_url` (slugged shop home, for the
+"All" link) and `tag_base` (`request.shop.absolute_url(request,
+slug=False)` = `/s/{id}`, no shop slug). Category links MUST use
+`{tag_base}/tag/{slug}` so they match the `shop_tag_detail` route
+(`/s/{shop_id}/tag/{slug}`). Using the slugged URL produces
+`/s/{id}/{shop_slug}/tag/{slug}` which falls through to the
+`shop_slug` catch-all and silently renders the shop home instead of
+the filtered tag page (the 2.6b→2.6c defect).
+
 Every page that opts into categorization (operator picks `home_layout
 >= 1`, or tag detail page) includes BOTH variants in the markup. CSS
 hides one per viewport: `details.facet-details` hidden ≥800px, `aside
diff --git a/docs/tickets/mps-24.md b/docs/tickets/mps-24.md
index de078a4..4ce8042 100644
--- a/docs/tickets/mps-24.md
+++ b/docs/tickets/mps-24.md
@@ -319,6 +319,26 @@ picker is Phase 2).
 | `tests/test_models.py` | `TestTagSuggestPureFunctions` — 11 unit tests over tokenize / stem / cluster |
 | `tests/test_functional.py` | `test_suggest_clusters_renders_candidates`, `test_apply_suggestion_creates_tag_and_attaches_products`, `test_dismiss_suggestion_adds_to_stopwords`, `test_apply_suggestion_rejects_empty_input` |
 
+### Phase 2.6c — fix sidebar category links falling through to shop-home catch-all (shipped 2026-05-15)
+
+Defect from 2.6b operator review: clicking any category in the desktop
+sidebar navigated to a page that "looked exactly like home" (screenshots
+in chat). Root cause: the facet macro built category links as
+`{absolute_url}/tag/{slug}` where `absolute_url` includes the shop slug
+(`/s/{id}/{shop_slug}`). The resulting path `/s/{id}/{shop_slug}/tag/{slug}`
+does **not** match the tag detail route `/s/{shop_id}/tag/{slug}` — it
+falls through to the `shop_slug` catch-all (`/s/{shop_id}/{slug:.*}`)
+and renders the shop home / lanes, ignoring the tag entirely.
+
+Fix: `_facet_nav.j2` macros take a new `tag_base` arg =
+`request.shop.absolute_url(request, slug=False)` (= `/s/{id}`, no shop
+slug). Category links now build `{tag_base}/tag/{slug}` which matches
+`shop_tag_detail` exactly. The "All" link still uses the slugged
+`base_url` (shop home). All three call sites (shop_tag.j2, home.j2,
+shop.j2) updated. Regression test:
+`test_facet_category_link_renders_tag_detail_not_home` +
+hardened assertions in `test_tag_detail_renders_facet_sidebar`.
+
 ### Phase 2.6b — facet nav on shop home (layout 2) + mobile SERP rows under each lane (shipped 2026-05-15)
 
 Follow-up to 2.6 after operator review on tablet: layout 2 (sectioned
diff --git a/make_post_sell/templates/_facet_nav.j2 b/make_post_sell/templates/_facet_nav.j2
index 72a884d..36c2ae0 100644
--- a/make_post_sell/templates/_facet_nav.j2
+++ b/make_post_sell/templates/_facet_nav.j2
@@ -11,7 +11,12 @@
 
    Args:
      variant       — "sidebar" (desktop <aside>) or "details" (mobile <details>)
-     base_url      — shop absolute URL for "All" + tag links (no trailing slash)
+     base_url      — shop home URL for the "All" link (slug ok)
+     tag_base      — slug-LESS shop base (/s/{id}) so {tag_base}/tag/{slug}
+                     matches the shop_tag_detail route exactly. The route
+                     is /s/{shop_id}/tag/{slug} — a shop-slug segment in
+                     the path would fall through to the shop_slug
+                     catch-all and render the shop home instead.
      sort_options  — list of (key, label) tuples for the sort <select>
      sort_key      — currently selected sort key
      price_min     — current min in cents (int or None)
@@ -24,7 +29,7 @@
 {%- if cents is not none -%}{{ (cents / 100)|round(2) }}{%- endif -%}
 {% endmacro %}
 
-{% macro facet_form(base_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
+{% macro facet_form(base_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
 <form method="get" action="" class="facet-form">
 
   <section class="facet-section">
@@ -69,7 +74,7 @@
       </li>
       {% for t in facet_tags %}
       <li>
-        <a href="{{ base_url }}/tag/{{ t.slug }}"
+        <a href="{{ tag_base }}/tag/{{ t.slug }}"
            class="facet-tag{% if active_tag and active_tag.id == t.id %} facet-tag-active{% endif %}"
            rel="nofollow">{{ t.name }}</a>
       </li>
@@ -81,18 +86,18 @@
 </form>
 {% endmacro %}
 
-{% macro sidebar(base_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
+{% macro sidebar(base_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
 <aside class="facet-nav" aria-label="Filter and sort">
-  {{ facet_form(base_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+  {{ facet_form(base_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 </aside>
 {% endmacro %}
 
-{% macro details(base_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
+{% macro details(base_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) %}
 <details class="facet-details">
   <summary class="facet-details-summary">
     &#x1F50D; Filter &amp; sort
     {%- if price_min is not none or price_max is not none %} <span class="facet-details-active-mark">&bull;</span>{% endif -%}
   </summary>
-  {{ facet_form(base_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+  {{ facet_form(base_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 </details>
 {% endmacro %}
diff --git a/make_post_sell/templates/home.j2 b/make_post_sell/templates/home.j2
index c306629..94c14bd 100644
--- a/make_post_sell/templates/home.j2
+++ b/make_post_sell/templates/home.j2
@@ -81,6 +81,7 @@
 {% else %}
 
   {% set shop_url = request.shop.absolute_url(request) %}
+  {% set tag_base = request.shop.absolute_url(request, slug=False) %}
   {# MPS-24 Phase 2.6: when the operator opted into categorization
      (home_layout 1 chips or 2 lanes), give shoppers the full facet
      nav — sidebar on desktop, <details> accordion on mobile/tablet.
@@ -105,11 +106,11 @@
 
   {% if show_facet_nav %}
   {# Mobile/tablet: collapsed <details> facets above the grid. #}
-  {{ facet.details(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+  {{ facet.details(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
   <div class="tag-detail-layout">
 
     {# Desktop sidebar. #}
-    {{ facet.sidebar(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+    {{ facet.sidebar(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 
     <div class="tag-detail-content">
   {% endif %}
diff --git a/make_post_sell/templates/shop.j2 b/make_post_sell/templates/shop.j2
index 67e69b6..7ba79f2 100644
--- a/make_post_sell/templates/shop.j2
+++ b/make_post_sell/templates/shop.j2
@@ -12,6 +12,7 @@
 {% endif %}
 
 {% set shop_url = request.shop.absolute_url(request) %}
+{% set tag_base = request.shop.absolute_url(request, slug=False) %}
 {% set show_facet_nav = request.shop.home_layout and request.shop.home_layout >= 1 %}
 
 {# MPS-24: tag chip strip — shown on layout 1 (chips) and 2 (lanes). #}
@@ -32,11 +33,11 @@
 
 {% if show_facet_nav %}
 {# Mobile/tablet: collapsed <details> facets above the grid. #}
-{{ facet.details(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+{{ facet.details(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 <div class="tag-detail-layout">
 
   {# Desktop sidebar. #}
-  {{ facet.sidebar(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+  {{ facet.sidebar(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 
   <div class="tag-detail-content">
 {% endif %}
diff --git a/make_post_sell/templates/shop_tag.j2 b/make_post_sell/templates/shop_tag.j2
index 76693fc..6c0562a 100644
--- a/make_post_sell/templates/shop_tag.j2
+++ b/make_post_sell/templates/shop_tag.j2
@@ -4,6 +4,7 @@
 {% block content -%}
 
 {% set shop_url = request.shop.absolute_url(request) %}
+{% set tag_base = request.shop.absolute_url(request, slug=False) %}
 
 <section class="one-column tag-detail-header">
   <h1 class="type-headline-3">{{ active_tag.name }}</h1>
@@ -12,12 +13,12 @@
 
 {# Mobile/tablet: collapsed <details> facets above the grid (CSS hides
    it ≥800px where the sidebar takes over). #}
-{{ facet.details(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+{{ facet.details(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 
 <div class="tag-detail-layout">
 
   {# Desktop sidebar — hidden <800px via CSS. #}
-  {{ facet.sidebar(shop_url, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
+  {{ facet.sidebar(shop_url, tag_base, sort_options, sort_key, price_min, price_max, facet_tags, active_tag) }}
 
   <div class="tag-detail-content">
 
diff --git a/make_post_sell/tests/test_functional.py b/make_post_sell/tests/test_functional.py
index 76ca658..c3ddb88 100644
--- a/make_post_sell/tests/test_functional.py
+++ b/make_post_sell/tests/test_functional.py
@@ -8534,6 +8534,48 @@ class TestHomeLayoutAndTags(_AuthenticatedBase):
         # Both sidebar (desktop) and details accordion (mobile) render.
         self.assertIn('facet-nav', body)
         self.assertIn('facet-details', body)
+        # Regression: category links must hit the slug-LESS tag route
+        # (/s/{id}/tag/{slug}), NOT /s/{id}/{shop_slug}/tag/{slug}.
+        # The latter falls through to the shop_slug catch-all and
+        # renders the shop home instead of the filtered tag page.
+        self.assertIn(f'/s/{shop.id}/tag/math"', body)
+        self.assertNotIn(f'/s/{shop.id}/{shop.slug}/tag/', body)
+
+    def test_facet_category_link_renders_tag_detail_not_home(self):
+        """Clicking a sidebar category must land on the tag detail page
+        (filtered SERP), not fall through to the shop home catch-all."""
+        shop, product = self._make_shop_with_product("facet-route-shop")
+        # Layout 2 so the home renders the facet sidebar.
+        self.testapp.post(
+            f"/s/{shop.id}/settings",
+            {
+                "form_section": "home-layout-settings",
+                "home_layout": "2",
+                "home_layout_tag_limit": "5",
+                "home_layout_per_lane_limit": "10",
+                "submit": "Save Home Layout",
+            },
+        )
+        self.testapp.post(
+            f"/p/{product.id}/edit",
+            {
+                "title": product.title,
+                "description": "One. Two. Three. Four. Five. Six.",
+                "price": str(product.price),
+                "visibility": "1",
+                "tags": "Math",
+            },
+        )
+        # The shop home sidebar link must be the slug-less tag route.
+        res = self.testapp.get(f"/s/{shop.id}/{shop.slug}")
+        self.assertIn(f'/s/{shop.id}/tag/math"', res.body.decode())
+        # Following that exact route renders the tag detail SERP page,
+        # which carries the unique .tag-detail-header h1 (the shop home
+        # lanes view never emits that element).
+        res = self.testapp.get(f"/s/{shop.id}/tag/math")
+        body = res.body.decode()
+        self.assertIn('tag-detail-header', body)
+        self.assertIn('serp-list', body)
 
     def test_tag_detail_price_filter_narrows_grid(self):
         """?price_min and ?price_max remove products outside the range."""