diff --git a/packages/app/src/App.tsx b/packages/app/src/App.tsx
index 13998cb..4aa5da2 100644
--- a/packages/app/src/App.tsx
+++ b/packages/app/src/App.tsx
@@ -9,6 +9,7 @@ import { LineagePage } from "./pages/LineagePage";
 import { LineageEntryPage } from "./pages/LineageEntryPage";
 import { DiffPage } from "./pages/DiffPage";
 import { CachePage } from "./pages/CachePage";
+import { CustomizationsPage } from "./pages/CustomizationsPage";
 import { EmptyStatePage } from "./pages/EmptyStatePage";
 import { ProjectsPage } from "./pages/ProjectsPage";
 import { api } from "./api";
@@ -55,6 +56,7 @@ export default function App() {
                 <Route path="lineage" element={<LineagePage />} />
                 <Route path="lineage/:hash" element={<LineageEntryPage />} />
                 <Route path="cache" element={<CachePage />} />
+                <Route path="customizations" element={<CustomizationsPage />} />
                 <Route path="diff/:alias" element={<DiffPage />} />
                 <Route path="diff/:alias/:va/:vb" element={<DiffPage />} />
                 <Route path="*" element={<Navigate to="catalog" replace />} />
diff --git a/packages/app/src/api.ts b/packages/app/src/api.ts
index 9ee30f4..1676c5e 100644
--- a/packages/app/src/api.ts
+++ b/packages/app/src/api.ts
@@ -7,6 +7,7 @@ import type {
   LineageLayout,
   DiffData,
   ResultCache,
+  Customizations,
   Projects,
 } from "./types";
 
@@ -132,6 +133,9 @@ export const api = {
   resultCache: (project: string): Promise<ResultCache> =>
     get(`/${project}/api/result_cache`),
 
+  customizations: (project: string): Promise<Customizations> =>
+    get(`/${project}/api/customizations`),
+
   deleteResultCache: (project: string, hash: string): Promise<{ ok: boolean; hash: string }> =>
     fetch(`/${project}/api/result_cache/${hash}`, { method: "DELETE" }).then((r) => {
       if (!r.ok) throw new Error(`delete failed: HTTP ${r.status}`);
diff --git a/packages/app/src/components/Header.tsx b/packages/app/src/components/Header.tsx
index 746c39e..4d9ccdb 100644
--- a/packages/app/src/components/Header.tsx
+++ b/packages/app/src/components/Header.tsx
@@ -81,6 +81,7 @@ export function Header() {
           <Link to={`/${project}/notebook`}>notebook</Link>
           <Link to={`/${project}/lineage`}>lineage</Link>
           <Link to={`/${project}/cache`}>cache</Link>
+          <Link to={`/${project}/customizations`}>customizations</Link>
           <Link to="/projects">projects</Link>
         </nav>
       )}
diff --git a/packages/app/src/pages/CustomizationsPage.tsx b/packages/app/src/pages/CustomizationsPage.tsx
new file mode 100644
index 0000000..1b6534f
--- /dev/null
+++ b/packages/app/src/pages/CustomizationsPage.tsx
@@ -0,0 +1,99 @@
+import { useEffect, useState } from "react";
+import { useParams } from "react-router-dom";
+import { api } from "../api";
+import { useSSE } from "../SSEContext";
+import type { CustomizationItem, Customizations } from "../types";
+
+const SECTIONS: { key: keyof Omit<Customizations, "project">; title: string; blurb: string }[] = [
+  {
+    key: "summary_stats",
+    title: "Summary stats",
+    blurb: "Per-column statistics computed by Buckaroo. def compute(col) -> ibis.Expr",
+  },
+  {
+    key: "display_klasses",
+    title: "Styling classes",
+    blurb: "ColAnalysis subclasses that control table rendering and pinned rows.",
+  },
+  {
+    key: "post_processings",
+    title: "Post-processing",
+    blurb: "Expression transformers offered in Buckaroo's post-processing dropdown. def process(expr) -> ibis.Expr | DataFrame",
+  },
+];
+
+function Section({ title, blurb, items }: { title: string; blurb: string; items: CustomizationItem[] }) {
+  const active = items.filter((i) => !i.disabled).length;
+  return (
+    <div className="cust-section">
+      <div className="cust-section-head">
+        <strong>{title}</strong>
+        <span className="meta">
+          {items.length === 0
+            ? "none"
+            : `${active} active${items.length - active ? ` · ${items.length - active} disabled` : ""}`}
+        </span>
+      </div>
+      <span className="meta cache-note">{blurb}</span>
+
+      {items.length === 0 ? (
+        <div className="nb-empty">none defined</div>
+      ) : (
+        items.map((item) => (
+          <details key={item.path} className="cust-item">
+            <summary>
+              <span className={`cust-name${item.disabled ? " muted" : ""}`}>{item.name}</span>
+              {item.disabled && <span className="cust-flag">disabled</span>}
+              <span className="meta cust-path" title={item.path}>
+                {item.path}
+              </span>
+            </summary>
+            <pre className="code">{item.source}</pre>
+          </details>
+        ))
+      )}
+    </div>
+  );
+}
+
+export function CustomizationsPage() {
+  const { project } = useParams<{ project: string }>();
+  const { version } = useSSE();
+  const [data, setData] = useState<Customizations | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState("");
+
+  useEffect(() => {
+    if (!project) return;
+    // Refetch on `version` bumps but keep the current data on screen — don't
+    // flip back to the loading state, so an SSE event doesn't flash the page.
+    api
+      .customizations(project)
+      .then((d) => { setData(d); setError(""); setLoading(false); })
+      .catch((e) => { setError(String(e)); setLoading(false); });
+  }, [project, version]);
+
+  return (
+    <main style={{ overflow: "auto" }}>
+      <div className="cache-pane">
+        <div className="cache-summary">
+          <strong>Catalog customizations</strong>
+          <span className="meta cache-note">
+            Project-wide Buckaroo customizations. They apply to every entry in the catalog and are loaded
+            into each session. Read-only here — edit via the MCP tools.
+          </span>
+        </div>
+
+        {loading ? (
+          <div className="meta" style={{ padding: 16 }}>loading…</div>
+        ) : error && !data ? (
+          <div className="error-banner">{error}</div>
+        ) : (
+          SECTIONS.map((s) => (
+            <Section key={s.key} title={s.title} blurb={s.blurb} items={data ? data[s.key] : []} />
+          ))
+        )}
+      </div>
+    </main>
+  );
+}
diff --git a/packages/app/src/styles.css b/packages/app/src/styles.css
index 5702d4a..5c1ae3f 100644
--- a/packages/app/src/styles.css
+++ b/packages/app/src/styles.css
@@ -514,6 +514,22 @@ table.cache-table .muted { color: var(--muted); }
 .del-btn:hover { background: #2a1b1b; color: #ffb4b4; border-color: #7a4a4a; }
 .del-btn:disabled { opacity: 0.5; cursor: default; }
 
+/* catalog customizations page */
+.cust-section { margin-bottom: 22px; }
+.cust-section-head { display: flex; align-items: baseline; gap: 12px; margin-bottom: 2px; }
+.cust-section-head strong { font-size: 14px; }
+.cust-section .cache-note { display: block; margin-bottom: 8px; }
+.cust-item { border: 1px solid var(--border); border-radius: 5px; margin-bottom: 6px; background: var(--panel, transparent); }
+.cust-item > summary { display: flex; align-items: baseline; gap: 10px; padding: 6px 10px; cursor: pointer; list-style: none; }
+.cust-item > summary::-webkit-details-marker { display: none; }
+.cust-item > summary::before { content: "▸"; color: var(--muted); font-size: 11px; }
+.cust-item[open] > summary::before { content: "▾"; }
+.cust-item .cust-name { font-weight: 600; font-family: ui-monospace, monospace; }
+.cust-item .cust-name.muted { color: var(--muted); font-weight: 400; text-decoration: line-through; }
+.cust-item .cust-path { margin-left: auto; font-family: ui-monospace, monospace; font-size: 11px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; max-width: 50%; }
+.cust-item .cust-flag { color: var(--muted); border: 1px solid var(--border); padding: 0 6px; border-radius: 10px; font-size: 11px; }
+.cust-item > pre.code { margin: 0; border-top: 1px solid var(--border); border-radius: 0 0 5px 5px; }
+
 /* projects management page */
 .projects-page { max-width: 600px; margin: 32px auto; padding: 16px; }
 .projects-page h2 { margin-top: 0; margin-bottom: 16px; }
diff --git a/packages/app/src/types.ts b/packages/app/src/types.ts
index 3be96ba..6834781 100644
--- a/packages/app/src/types.ts
+++ b/packages/app/src/types.ts
@@ -180,6 +180,20 @@ export interface ResultCache {
   total_formatted: string;
 }
 
+export interface CustomizationItem {
+  name: string;
+  path: string;
+  source: string;
+  disabled: boolean;
+}
+
+export interface Customizations {
+  project: string;
+  summary_stats: CustomizationItem[];
+  display_klasses: CustomizationItem[];
+  post_processings: CustomizationItem[];
+}
+
 export interface Projects {
   active: string | null;
   available: string[];
diff --git a/src/tallyman_companion/app.py b/src/tallyman_companion/app.py
index 9a7cefb..b8361e4 100644
--- a/src/tallyman_companion/app.py
+++ b/src/tallyman_companion/app.py
@@ -1007,6 +1007,23 @@ def api_result_cache(project: str):
             "total_formatted": _fmt_bytes(total),
         }
 
+    @app.get("/{project}/api/customizations")
+    def api_customizations(project: str):
+        """Project-wide buckaroo customizations: summary stats, display
+        klasses and post-processing functions, each with its source. These
+        are global to the catalog (one set per project), not per-entry."""
+        project = _validate_project(project)
+        from tallyman_core.display_klasses import list_display_klasses  # noqa: PLC0415
+        from tallyman_core.post_processing import list_post_processings  # noqa: PLC0415
+        from tallyman_core.summary_stats import list_stats  # noqa: PLC0415
+
+        return {
+            "project": project,
+            "summary_stats": list_stats(project),
+            "display_klasses": list_display_klasses(project),
+            "post_processings": list_post_processings(project),
+        }
+
     @app.delete("/{project}/api/result_cache/{content_hash}")
     async def api_delete_result_cache(project: str, content_hash: str):
         project = _validate_project(project)