diff --git a/server/typescript/packages/cli/src/commands/docs.ts b/server/typescript/packages/cli/src/commands/docs.ts
index 1cbd70023..695581538 100644
--- a/server/typescript/packages/cli/src/commands/docs.ts
+++ b/server/typescript/packages/cli/src/commands/docs.ts
@@ -33,6 +33,7 @@ import type {
 } from "@metaobjectsdev/codegen-ts";
 import { docsFile, apiDocsFile } from "@metaobjectsdev/codegen-ts/generators";
 import { composeRegistry, coreProviders, renderCoreMetamodelDocs } from "@metaobjectsdev/metadata";
+import type { MetaDataTypeProvider } from "@metaobjectsdev/metadata";
 import { generateSite, SITE_TEMPLATE_NAMES, SITE_ASSET_NAMES, readSiteFile } from "@metaobjectsdev/docs-site";
 
 type DocsLayout = "flat" | "package";
@@ -260,7 +261,7 @@ export async function docsCommand(args: string[], cwd: string): Promise<number>
   // WITHOUT building the markdown GenContext — decoupled and one fewer failure
   // surface. Combined with --model/--api it is emitted after them (below).
   if (flags.site && docsCfg.surfaces.length === 0) {
-    return emitSite(metaRoot, outDir);
+    return emitSite(metaRoot, outDir, configProviders);
   }
 
   // Load metadata standalone — same loader path as migrate/gen. Threads any
@@ -427,7 +428,7 @@ export async function docsCommand(args: string[], cwd: string): Promise<number>
 
   // SITE surface (additive) — emit after the markdown surfaces so both coexist.
   if (flags.site) {
-    const siteRc = await emitSite(metaRoot, outDir);
+    const siteRc = await emitSite(metaRoot, outDir, configProviders);
     if (siteRc !== 0) return siteRc;
   }
 
@@ -496,7 +497,11 @@ async function scaffoldSiteCommand(metaRoot: string): Promise<number> {
  * templates/assets into `<metaRoot>/codegen/docs-site/` (via `--scaffold-site`),
  * those win over the bundled defaults.
  */
-async function emitSite(metaRoot: string, outDir: string): Promise<number> {
+async function emitSite(
+  metaRoot: string,
+  outDir: string,
+  configProviders?: readonly MetaDataTypeProvider[],
+): Promise<number> {
   const siteOutDir = resolvePath(outDir, "site");
   const sourceDirs = [join(metaRoot, DEFAULT_METADATA_DIR)];
   // Scaffold-and-own: when the consumer has copied templates/assets into
@@ -511,6 +516,10 @@ async function emitSite(metaRoot: string, outDir: string): Promise<number> {
       stamp: new Date().toISOString().slice(0, 10),
       commit: "",
       core: { n: 15 },
+      // Thread any consumer providers from metaobjects.config.ts so the site's
+      // own loader resolves custom field/view/object subtypes — same providers
+      // the markdown surfaces get via loadMemory.
+      ...(configProviders !== undefined ? { extraProviders: configProviders } : {}),
       ...(existsSync(ownedTemplates) ? { templatesDir: ownedTemplates } : {}),
       ...(existsSync(ownedAssets) ? { assetsDir: ownedAssets } : {}),
     });
diff --git a/server/typescript/packages/cli/test/docs-command.test.ts b/server/typescript/packages/cli/test/docs-command.test.ts
index 044dac357..8a6dbf28e 100644
--- a/server/typescript/packages/cli/test/docs-command.test.ts
+++ b/server/typescript/packages/cli/test/docs-command.test.ts
@@ -437,6 +437,19 @@ describe("meta docs --site — HTML documentation site", () => {
     const b = await readFile(join(out2, "site", "index.html"), "utf8");
     expect(a).toBe(b);
   });
+
+  test("--site threads metaobjects.config.ts providers so custom-subtype metadata renders", async () => {
+    const root = await customTypeProject();
+    const out = join(root, "out-site-custom");
+
+    // Place uses field.geopoint, resolvable ONLY via the provider declared in
+    // metaobjects.config.ts. The site surface has its OWN loader (docs-site's
+    // loadModel); before it threaded the config providers, this rejected the
+    // unknown subtype and returned non-zero.
+    const code = await docsCommand([root, "--site", "--out", out], root);
+    expect(code).toBe(0);
+    expect(existsSync(join(out, "site", "index.html"))).toBe(true);
+  });
 });
 
 describe("meta docs --scaffold-site — own your theme", () => {
diff --git a/server/typescript/packages/docs-site/src/index.ts b/server/typescript/packages/docs-site/src/index.ts
index 318904da4..06ce1064a 100644
--- a/server/typescript/packages/docs-site/src/index.ts
+++ b/server/typescript/packages/docs-site/src/index.ts
@@ -1,3 +1,4 @@
 export { generateSite } from "./site.js";
 export type { SiteOptions, SiteResult } from "./site.js";
 export { SITE_TEMPLATE_NAMES, SITE_ASSET_NAMES, readSiteFile } from "./scaffold.js";
+export type { MetaDataTypeProvider } from "@metaobjectsdev/metadata";
diff --git a/server/typescript/packages/docs-site/src/load.ts b/server/typescript/packages/docs-site/src/load.ts
index 4d4a077c5..bd32dc003 100644
--- a/server/typescript/packages/docs-site/src/load.ts
+++ b/server/typescript/packages/docs-site/src/load.ts
@@ -2,7 +2,7 @@ import { mkdtempSync, rmSync, symlinkSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { basename, join, resolve } from "node:path";
 import { MetaDataLoader, composeRegistry, coreTypesProvider, dbProvider, docProvider, promptProvider, uiProvider } from "@metaobjectsdev/metadata";
-import type { MetaData, MetaRoot } from "@metaobjectsdev/metadata";
+import type { MetaData, MetaRoot, MetaDataTypeProvider } from "@metaobjectsdev/metadata";
 
 export interface LoadedModel {
   root: MetaRoot;
@@ -10,8 +10,19 @@ export interface LoadedModel {
   sourceDirs: string[];
 }
 
-/** Load N metadata source dirs into ONE root via a staging dir of symlinks. */
-export async function loadModel(sourceDirs: string[]): Promise<LoadedModel> {
+/**
+ * Load N metadata source dirs into ONE root via a staging dir of symlinks.
+ *
+ * `extraProviders` are consumer-supplied metamodel providers, composed AFTER
+ * the built-in bundle (core-types + db + doc + prompt + ui) — mirroring
+ * `loadMemory`'s `providers` option — so a site can document metadata that uses
+ * custom field/view/object subtypes (e.g. a project's `metaobjects.config.ts`
+ * `providers`). Defaults to none, so config-less callers are unchanged.
+ */
+export async function loadModel(
+  sourceDirs: string[],
+  extraProviders: readonly MetaDataTypeProvider[] = [],
+): Promise<LoadedModel> {
   const staging = mkdtempSync(join(tmpdir(), "metadocs-"));
   try {
     const usedBasenames = new Set<string>();
@@ -23,7 +34,7 @@ export async function loadModel(sourceDirs: string[]): Promise<LoadedModel> {
       usedBasenames.add(baseName);
       symlinkSync(resolve(dir), join(staging, baseName));
     }
-    const registry = composeRegistry([coreTypesProvider, dbProvider, docProvider, promptProvider, uiProvider]);
+    const registry = composeRegistry([coreTypesProvider, dbProvider, docProvider, promptProvider, uiProvider, ...extraProviders]);
     const result = await MetaDataLoader.fromDirectory(staging, { registry, strict: false });
     if (result.errors.length > 0) {
       throw new Error(`metadata load failed:\n${result.errors.map((e) => String(e)).join("\n")}`);
diff --git a/server/typescript/packages/docs-site/src/site.ts b/server/typescript/packages/docs-site/src/site.ts
index 9d498509a..7a080124e 100644
--- a/server/typescript/packages/docs-site/src/site.ts
+++ b/server/typescript/packages/docs-site/src/site.ts
@@ -2,6 +2,7 @@ import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
 import { dirname, join, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 import { render, InMemoryProvider } from "@metaobjectsdev/render";
+import type { MetaDataTypeProvider } from "@metaobjectsdev/metadata";
 import { loadModel } from "./load.js";
 import { LinkGraph, fqnOf } from "./link-graph.js";
 import { CoverageTracker } from "./coverage.js";
@@ -34,6 +35,10 @@ export interface SiteOptions {
   templatesDir?: string;
   /** Override dir for assets; if a file of the same basename exists here, it wins over the bundled assets/ dir. */
   assetsDir?: string | undefined;
+  /** Consumer-supplied metamodel providers, composed AFTER the built-in bundle
+   *  (core-types + db + doc + prompt + ui) so a site can document metadata that
+   *  uses custom field/view/object subtypes. Mirrors loadMemory's `providers`. */
+  extraProviders?: readonly MetaDataTypeProvider[];
 }
 
 export interface SiteResult {
@@ -131,7 +136,7 @@ function buildNavHtml(
 
 export async function generateSite(opts: SiteOptions): Promise<SiteResult> {
   // 1. Load + graph + comments
-  const loaded = await loadModel(opts.sourceDirs);
+  const loaded = await loadModel(opts.sourceDirs, opts.extraProviders);
   const g = new LinkGraph(loaded);
   const docs = harvestComments(opts.sourceDirs);
   const cov = new CoverageTracker();
diff --git a/server/typescript/packages/docs-site/test/provider-extension.test.ts b/server/typescript/packages/docs-site/test/provider-extension.test.ts
new file mode 100644
index 000000000..32ba5cc4b
--- /dev/null
+++ b/server/typescript/packages/docs-site/test/provider-extension.test.ts
@@ -0,0 +1,75 @@
+import { expect, test } from "bun:test";
+import { existsSync, mkdtempSync, mkdirSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { TypeId, TYPE_FIELD, MetaField } from "@metaobjectsdev/metadata";
+import type { MetaDataTypeProvider } from "@metaobjectsdev/metadata";
+import { generateSite } from "../src/site";
+import { loadModel } from "../src/load";
+
+// A consumer-supplied provider registering a custom field subtype the built-in
+// bundle (core-types/db/doc/prompt/ui) does not know — mirrors how an adopter
+// ships custom vocabulary via metaobjects.config.ts `providers`.
+function geoProvider(): MetaDataTypeProvider {
+  return {
+    id: "test-geo",
+    dependencies: ["metaobjects-core-types"],
+    registerTypes(registry) {
+      registry.register({
+        typeId: new TypeId(TYPE_FIELD, "geopoint"),
+        description: "A geographic point field",
+        factory: (typeId, name) => new MetaField(typeId, name),
+        childRules: [],
+        attributes: [],
+      });
+    },
+  };
+}
+
+// Metadata whose `field.geopoint` resolves ONLY when geoProvider is registered.
+function customTypeDir(): string {
+  const root = mkdtempSync(join(tmpdir(), "docs-extra-prov-"));
+  const acme = join(root, "acme");
+  mkdirSync(acme, { recursive: true });
+  writeFileSync(
+    join(acme, "place.yaml"),
+    [
+      "metadata:",
+      "  package: acme::geo",
+      "  children:",
+      "    - object.value:",
+      "        name: Place",
+      "        children:",
+      "          - field.string: { name: name }",
+      "          - field.geopoint: { name: location }",
+      "",
+    ].join("\n"),
+    "utf8",
+  );
+  return acme;
+}
+
+test("loadModel: a custom subtype fails without its provider, resolves with extraProviders", async () => {
+  const dir = customTypeDir();
+  // Without the provider the loader rejects the unknown subtype (the exact
+  // failure a consumer hit running docs over metadata with custom view/field types).
+  await expect(loadModel([dir])).rejects.toThrow(/geopoint|not registered|Unknown type/i);
+  // Threading the provider through extraProviders resolves it.
+  const model = await loadModel([dir], [geoProvider()]);
+  expect(model.root.objects().map((o) => o.name)).toContain("Place");
+});
+
+test("generateSite: extraProviders lets a site document custom-subtype metadata", async () => {
+  const dir = customTypeDir();
+  const out = mkdtempSync(join(tmpdir(), "docs-extra-out-"));
+  const r = await generateSite({
+    sourceDirs: [dir],
+    outDir: out,
+    title: "Fixture",
+    stamp: "2026-01-01",
+    commit: "abc1234",
+    extraProviders: [geoProvider()],
+  });
+  expect(existsSync(join(out, "index.html"))).toBe(true);
+  expect(r.dangling).toEqual([]);
+});