diff --git a/frontend/src/assets/components.css b/frontend/src/assets/components.css
new file mode 100644
index 0000000..2330227
--- /dev/null
+++ b/frontend/src/assets/components.css
@@ -0,0 +1,114 @@
+/* Shared component styles — the house recipes, in one place.
+ * ===========================================================================
+ *
+ * WHY THIS FILE EXISTS
+ *
+ * `.btn-primary` was defined five times, in five scoped stylesheets, and all
+ * five had drifted: three paddings, three font sizes, three disabled opacities,
+ * and one view with no disabled style at all (#2273). Nothing detected that,
+ * because a scoped duplicate is invisible to every tool — it isn't a rule
+ * violation, isn't a broken reference, and isn't a recorded snippet.
+ *
+ * GEOMETRY LIVES HERE; the class names are the app's existing ones so no
+ * template changes. Every value is a design-system token, so a palette or scale
+ * change moves the buttons rather than stranding a copy that no longer matches.
+ *
+ * MIGRATION NOTE — this file is deliberately safe to land ahead of the removals.
+ * These are plain selectors (specificity 0,1,0); a Vue `<style scoped>` rule
+ * compiles to `.btn-primary[data-v-…]` (0,2,0) and therefore WINS. So a view
+ * still carrying its own copy is unaffected until that copy is deleted, and
+ * every intermediate state of the migration is coherent.
+ */
+
+/* --- the shared shape ---------------------------------------------------- */
+
+.btn-primary,
+.btn-secondary,
+.btn-ghost,
+.btn-danger {
+  padding: var(--fs-space-2) var(--fs-space-4);   /* 8px 16px */
+  border: none;
+  border-radius: var(--fs-radius-md);             /* 8px — the system's button radius */
+  font-family: var(--fs-font-body);
+  font-size: var(--fs-size-label);                /* 12px */
+  font-weight: var(--fs-weight-medium);           /* 500 — the heaviest the system goes */
+  line-height: var(--fs-leading-body);
+  white-space: nowrap;
+  cursor: pointer;
+  transition: background var(--fs-dur-fast) var(--fs-ease),
+              border-color var(--fs-dur-fast) var(--fs-ease),
+              color var(--fs-dur-fast) var(--fs-ease);
+}
+
+/* One rule, so a disabled button can never look enabled in one view and
+ * disabled in another — which is exactly what ProjectListView shipped, having
+ * no disabled style at all. */
+.btn-primary:disabled,
+.btn-secondary:disabled,
+.btn-ghost:disabled,
+.btn-danger:disabled {
+  opacity: var(--fs-disabled-opacity);
+  cursor: not-allowed;
+}
+
+.btn-primary:focus-visible,
+.btn-secondary:focus-visible,
+.btn-ghost:focus-visible,
+.btn-danger:focus-visible {
+  outline: none;
+  box-shadow: var(--fs-focus-ring);
+}
+
+/* --- variants ------------------------------------------------------------ */
+
+/* The accent is deliberately ABSENT from every filled variant. Action colours
+ * are universal across the family so a Save button looks identical in every
+ * app — the accent is identity, not action. */
+.btn-primary {
+  background: var(--color-action-primary);
+  color: var(--fs-text-on-action);
+}
+.btn-primary:not(:disabled):hover {
+  background: var(--color-action-primary-hover);
+}
+
+.btn-secondary {
+  background: var(--color-action-secondary);
+  color: var(--fs-text-on-action);
+}
+.btn-secondary:not(:disabled):hover {
+  background: var(--color-action-secondary-hover);
+}
+
+/* Ghost is an OUTLINE, which is why its border and the tertiary action colour
+ * are the same token rather than two values that happen to match. Hover moves
+ * the BORDER, not the text to the accent — SnippetDetailView tinted the label
+ * with the accent on hover, which the house style reserves for identity and
+ * active state, not for general chrome. */
+.btn-ghost {
+  background: none;
+  border: var(--fs-border);
+  color: var(--color-text);
+}
+.btn-ghost:not(:disabled):hover {
+  border: var(--fs-border-hover);
+  background: var(--color-hover);
+}
+
+/* Destructive is NOT the error colour: an error is a failure that happened, a
+ * destructive action is one about to happen. Pair with an icon. */
+.btn-danger {
+  background: var(--color-action-destructive);
+  color: var(--fs-text-on-action);
+}
+.btn-danger:not(:disabled):hover {
+  background: var(--color-action-destructive-hover);
+}
+
+/* --- size modifiers ------------------------------------------------------ */
+
+.btn-small,
+.btn-sm {
+  padding: var(--fs-space-1) var(--fs-space-3);   /* 4px 12px */
+  font-size: var(--fs-size-tiny);
+}
diff --git a/frontend/src/main.ts b/frontend/src/main.ts
index cb8becd..865c447 100644
--- a/frontend/src/main.ts
+++ b/frontend/src/main.ts
@@ -3,6 +3,8 @@ import { createPinia } from "pinia";
 import App from "./App.vue";
 import router from "./router";
 import "./assets/theme.css";
+// After theme.css — it consumes the tokens declared there.
+import "./assets/components.css";
 import "./assets/prose.css";
 
 const app = createApp(App);
diff --git a/frontend/src/views/DesignSystemsView.vue b/frontend/src/views/DesignSystemsView.vue
index 76fd9f8..805f859 100644
--- a/frontend/src/views/DesignSystemsView.vue
+++ b/frontend/src/views/DesignSystemsView.vue
@@ -1262,47 +1262,6 @@ textarea.input {
 
 /* Buttons ---------------------------------------------------------------- */
 
-.btn-primary,
-.btn-ghost,
-.btn-danger {
-  border-radius: var(--radius-sm);
-  padding: 0.45rem 0.9rem;
-  font: inherit;
-  font-size: 0.85rem;
-  cursor: pointer;
-  border: 1px solid transparent;
-}
-
-.btn-primary {
-  background: var(--color-action-primary);
-  color: var(--fs-text-on-action);
-}
-
-.btn-primary:not(:disabled):hover {
-  background: var(--color-action-primary-hover);
-}
-
-.btn-ghost {
-  background: none;
-  border-color: var(--color-border);
-  color: var(--color-text-secondary);
-}
-
-.btn-danger {
-  background: var(--color-action-destructive);
-  color: #E8E4D8;
-}
-
-.btn-small {
-  padding: 0.25rem 0.55rem;
-  font-size: 0.75rem;
-}
-
-.btn-primary:disabled,
-.btn-ghost:disabled {
-  opacity: 0.5;
-  cursor: not-allowed;
-}
 
 
 .row-actions {
diff --git a/frontend/src/views/DesignView.vue b/frontend/src/views/DesignView.vue
index 8c142c9..21d3f46 100644
--- a/frontend/src/views/DesignView.vue
+++ b/frontend/src/views/DesignView.vue
@@ -12,11 +12,12 @@
  * every specimen below is either a REAL component imported from the app, or a
  * real token read from the browser, or it is explicitly marked as missing.
  *
- * Buttons are the case where that bites. Rule 65 specifies four variants, but
- * `.btn-primary` is defined four separate times in four `<style scoped>` blocks
- * and 30 of 54 SFCs carry their own button CSS (#2273). There is no shared
- * button to import, so rendering one here would just make this a fifth copy.
- * It is reported as a gap instead.
+ * Buttons WERE the case where that bit: `.btn-primary` was defined five times
+ * in five `<style scoped>` blocks, all five drifted, and this page reported it
+ * as a gap because drawing a look-alike would have made it a sixth copy.
+ * `assets/components.css` is now the single definition (#2273), so the
+ * specimens below are the app's real classes — they cannot drift from the app
+ * without drifting the app itself.
  */
 import { computed, onMounted, ref } from "vue";
 
@@ -225,25 +226,24 @@ const TYPE_SPECIMENS = [
       </div>
     </section>
 
-    <!-- The honest gap. -->
+    <!-- No longer a gap: these are the app's real classes, from the shared
+         sheet. Nothing here is a look-alike — change components.css and these
+         specimens change with it, which is the only way this page stays true. -->
     <section class="design-section">
       <h2>Buttons</h2>
-      <div class="gap-notice">
-        <strong>Not implemented as a shared component.</strong>
-        <p>
-          Rule 65 specifies four variants. In practice <code>.btn-primary</code> is
-          defined four separate times in four <code>&lt;style scoped&gt;</code>
-          blocks, and 30 of 54 single-file components carry their own button CSS.
-          There is no shared button to render here, and drawing one would make
-          this page a fifth copy of it — the exact drift this surface exists to
-          catch. Tracked as issue #2273.
-        </p>
+      <div class="button-specimens">
+        <button class="btn-primary">Save</button>
+        <button class="btn-secondary">Detect</button>
+        <button class="btn-ghost">Cancel</button>
+        <button class="btn-danger">Delete</button>
+        <button class="btn-primary" disabled>Disabled</button>
+        <button class="btn-ghost btn-small">Small</button>
       </div>
       <ul class="spec-list">
         <li v-for="b in RULEBOOK_BUTTONS" :key="b.name">
           <span class="spec-name">{{ b.name }}</span>
           <span class="spec-detail">{{ b.spec }}</span>
-          <span class="spec-status missing">missing</span>
+          <span class="spec-status ok">shared</span>
         </li>
       </ul>
     </section>
@@ -361,6 +361,17 @@ const TYPE_SPECIMENS = [
 
 /* Gaps ------------------------------------------------------------------- */
 
+/* Layout only. The buttons inside style themselves from the shared sheet —
+   adding any appearance rule here would recreate the copy this section
+   just stopped being. */
+.button-specimens {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: var(--fs-space-3);
+  margin-bottom: 1rem;
+}
+
 .gap-notice {
   background: var(--color-surface);
   border: 1px solid var(--color-border);
diff --git a/frontend/src/views/ProjectListView.vue b/frontend/src/views/ProjectListView.vue
index f4f3d8a..9e8d2c1 100644
--- a/frontend/src/views/ProjectListView.vue
+++ b/frontend/src/views/ProjectListView.vue
@@ -284,20 +284,6 @@ function overallPct(project: Project): { total: number; pct: number } {
 
 /* Moss action-primary per Hybrid — list-view utility action,
    not a brand moment. Empty-state .empty-action below keeps accent. */
-.btn-primary {
-  padding: 0.45rem 1rem;
-  background: var(--color-action-primary);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.9rem;
-  font-family: inherit;
-  transition: background 0.15s;
-}
-.btn-primary:hover {
-  background: var(--color-action-primary-hover);
-}
 
 .filter-tabs {
   display: flex;
diff --git a/frontend/src/views/SettingsView.vue b/frontend/src/views/SettingsView.vue
index 390ecca..dc7b975 100644
--- a/frontend/src/views/SettingsView.vue
+++ b/frontend/src/views/SettingsView.vue
@@ -2600,37 +2600,9 @@ function formatUserDate(iso: string): string {
 .btn-danger-outline:disabled { opacity: 0.5; cursor: default; }
 
 /* Filled destructive: Oxblood action-destructive */
-.btn-danger {
-  padding: 0.4rem 0.9rem;
-  background: var(--color-action-destructive);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.875rem;
-  font-family: inherit;
-  white-space: nowrap;
-  transition: background 0.15s;
-}
-.btn-danger:hover:not(:disabled) { background: var(--color-action-destructive-hover); }
-.btn-danger:disabled { opacity: 0.5; cursor: default; }
 
 /* Secondary: Bronze action-secondary — alternate paths (Detect, Test,
    Refresh, Add slot, etc.). Outline form for visual lightness. */
-.btn-secondary {
-  padding: 0.4rem 0.9rem;
-  background: var(--color-action-secondary);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.875rem;
-  font-family: inherit;
-  white-space: nowrap;
-  transition: background 0.15s;
-}
-.btn-secondary:hover:not(:disabled) { background: var(--color-action-secondary-hover); }
-.btn-secondary:disabled { opacity: 0.6; cursor: default; }
 
 /* DB maintenance last-run summary */
 .db-maint-last { margin-top: 1rem; }
@@ -3148,20 +3120,6 @@ function formatUserDate(iso: string): string {
 
 /* ── Groups tab ──────────────────────────────────────────────── */
 /* Moss action-primary per Hybrid */
-.btn-primary {
-  padding: 0.4rem 0.9rem;
-  background: var(--color-action-primary);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.875rem;
-  font-family: inherit;
-  white-space: nowrap;
-  transition: background 0.15s;
-}
-.btn-primary:disabled { opacity: 0.6; cursor: default; }
-.btn-primary:hover:not(:disabled) { background: var(--color-action-primary-hover); }
 
 .input-field {
   width: 100%;
diff --git a/frontend/src/views/SnippetDetailView.vue b/frontend/src/views/SnippetDetailView.vue
index 70cd7cd..28ffed9 100644
--- a/frontend/src/views/SnippetDetailView.vue
+++ b/frontend/src/views/SnippetDetailView.vue
@@ -249,34 +249,6 @@ async function confirmDelete() {
   flex-shrink: 0;
 }
 
-.btn-ghost {
-  padding: 0.35rem 0.8rem;
-  border: 1px solid var(--color-border);
-  background: transparent;
-  color: var(--color-text);
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.85rem;
-  font-family: inherit;
-  transition: border-color 0.15s, color 0.15s;
-}
-.btn-ghost:hover {
-  border-color: var(--color-primary);
-  color: var(--color-primary);
-}
-.btn-danger {
-  padding: 0.35rem 0.8rem;
-  border: none;
-  background: var(--color-action-destructive, #6B2118);
-  color: var(--fs-text-on-action);
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.85rem;
-  font-family: inherit;
-}
-.btn-danger:hover {
-  opacity: 0.9;
-}
 
 .when-to-use {
   margin: 0.75rem 0 1.25rem;
diff --git a/frontend/src/views/SnippetEditorView.vue b/frontend/src/views/SnippetEditorView.vue
index c672fe6..01774b7 100644
--- a/frontend/src/views/SnippetEditorView.vue
+++ b/frontend/src/views/SnippetEditorView.vue
@@ -572,37 +572,6 @@ function cancel() {
   gap: 0.5rem;
   margin-top: 0.25rem;
 }
-.btn-primary {
-  padding: 0.5rem 1.1rem;
-  background: var(--color-action-primary);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.9rem;
-  font-family: inherit;
-  transition: background 0.15s;
-}
-.btn-primary:hover:not(:disabled) {
-  background: var(--color-action-primary-hover);
-}
-.btn-primary:disabled {
-  opacity: 0.5;
-  cursor: default;
-}
-.btn-secondary {
-  padding: 0.5rem 1.1rem;
-  background: var(--color-bg-secondary);
-  color: var(--color-text);
-  border: 1px solid var(--color-border);
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.9rem;
-  font-family: inherit;
-}
-.btn-secondary:hover {
-  background: var(--color-bg);
-}
 
 @media (max-width: 600px) {
   .field-row,
diff --git a/frontend/src/views/SnippetListView.vue b/frontend/src/views/SnippetListView.vue
index 6f7606b..b4b95b1 100644
--- a/frontend/src/views/SnippetListView.vue
+++ b/frontend/src/views/SnippetListView.vue
@@ -543,21 +543,6 @@ function usageTitle(s: SnippetListItem): string {
 }
 
 /* Moss action-primary per Hybrid — utility action, not a brand moment. */
-.btn-primary {
-  padding: 0.45rem 1rem;
-  background: var(--color-action-primary);
-  color: var(--fs-text-on-action);
-  border: none;
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.9rem;
-  font-family: inherit;
-  transition: background 0.15s;
-  white-space: nowrap;
-}
-.btn-primary:hover {
-  background: var(--color-action-primary-hover);
-}
 
 .search-row {
   margin-bottom: 1.25rem;
@@ -870,21 +855,6 @@ function usageTitle(s: SnippetListItem): string {
   gap: 0.5rem;
   align-items: center;
 }
-.btn-ghost {
-  padding: 0.4rem 0.85rem;
-  border: 1px solid var(--color-border);
-  background: transparent;
-  color: var(--color-text);
-  border-radius: var(--radius-sm);
-  cursor: pointer;
-  font-size: 0.9rem;
-  font-family: inherit;
-  transition: border-color 0.15s, color 0.15s;
-}
-.btn-ghost:hover {
-  border-color: var(--color-primary);
-  color: var(--color-primary);
-}
 
 /* Selected card = 2px accent border per the design system (featured/active). */
 .snippet-card.selected {
@@ -931,10 +901,6 @@ function usageTitle(s: SnippetListItem): string {
   flex: 1;
   min-width: 0;
 }
-.select-bar .btn-primary:disabled {
-  opacity: 0.5;
-  cursor: default;
-}
 
 /* Merge modal */
 .modal-overlay {