diff --git a/generator/package.json b/generator/package.json
index ca988ea..3529181 100644
--- a/generator/package.json
+++ b/generator/package.json
@@ -3,7 +3,7 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "generate": "bun ./src/index.ts",
+    "generate": "bun ./src/index.ts --snapshot=${INTROSPECTION_SNAPSHOT:-../../clients/.introspection/snapshot.json}",
     "start": "bun ./src/index.ts"
   },
   "devDependencies": {
diff --git a/generator/src/fetch.ts b/generator/src/fetch.ts
index 3952c15..2d7ec33 100644
--- a/generator/src/fetch.ts
+++ b/generator/src/fetch.ts
@@ -36,12 +36,34 @@ export type IntrospectPayload = {
   }[];
 };
 
-export let getEndpointVersions = async (url: string) =>
-  (await fetch(new URL('/metorial/introspect/versions', url)).then(res => res.json())) as {
-    versions: { version: string; displayVersion: string; isCurrent: boolean }[];
-  };
+export type IntrospectVersions = {
+  versions: { version: string; displayVersion: string; isCurrent: boolean }[];
+};
+
+export type IntrospectionSnapshot = {
+  versions: IntrospectVersions;
+  endpoints: Record<string, IntrospectPayload>;
+};
+
+export let getEndpointVersions = async (url: string, snapshot?: IntrospectionSnapshot) => {
+  if (snapshot) return snapshot.versions;
+
+  return (await fetch(new URL('/metorial/introspect/versions', url)).then(res =>
+    res.json()
+  )) as IntrospectVersions;
+};
+
+export let getEndpoints = async (
+  url: string,
+  version: string,
+  snapshot?: IntrospectionSnapshot
+) => {
+  if (snapshot) {
+    let payload = snapshot.endpoints[version];
+    if (!payload) throw new Error(`Missing introspection snapshot for ${version}.`);
+    return payload;
+  }
 
-export let getEndpoints = async (url: string, version: string) => {
   return (await fetch(
     new URL(`/metorial/introspect/endpoints?version=${version}`, url)
   ).then(res => res.json())) as IntrospectPayload;
diff --git a/generator/src/index.ts b/generator/src/index.ts
index ee6b120..ee12efb 100644
--- a/generator/src/index.ts
+++ b/generator/src/index.ts
@@ -1,7 +1,7 @@
 import path from 'node:path';
 import { $ } from 'bun';
 import { emitCatalogGo } from './emit/catalog.go';
-import { getEndpoints, getEndpointVersions } from './fetch';
+import { getEndpoints, getEndpointVersions, type IntrospectionSnapshot } from './fetch';
 import { joinManifest } from './join';
 import { loadManifest } from './manifest';
 
@@ -16,14 +16,21 @@ let args = process.argv.slice(2);
 let urlArg = args.find(arg => !arg.startsWith('-'));
 let urls = urlArg ? urlArg.split(',') : defaultUrls;
 
-let workingUrl = await resolveUrl(urls);
+// An explicit URL (argument or API_URL) wins over --snapshot so a running instance can be used.
+let snapshotPath = args.find(arg => arg.startsWith('--snapshot='))?.slice('--snapshot='.length);
+let snapshot =
+  snapshotPath && !urlArg && !process.env.API_URL
+    ? ((await Bun.file(path.resolve(snapshotPath)).json()) as IntrospectionSnapshot)
+    : undefined;
+
+let workingUrl = snapshot ? 'snapshot' : await resolveUrl(urls);
 if (!workingUrl) {
   throw new Error(`None of the API URLs are reachable: ${urls.join(', ')}`);
 }
 
 let manifestPath = path.join(repoRoot, 'manifest/admin.yaml');
 let manifest = await loadManifest(manifestPath);
-let versions = await getEndpointVersions(workingUrl);
+let versions = await getEndpointVersions(workingUrl, snapshot);
 let version =
   versions.versions.find(item => item.version === manifest.apiVersion) ||
   versions.versions.find(item => item.version.includes('magnetar'));
@@ -32,7 +39,7 @@ if (!version) {
   throw new Error(`API at ${workingUrl} does not expose ${manifest.apiVersion}`);
 }
 
-let payload = await getEndpoints(workingUrl, version.version);
+let payload = await getEndpoints(workingUrl, version.version, snapshot);
 let catalog = joinManifest({
   manifest,
   endpoints: payload.endpoints,