diff --git a/package.json b/package.json
index 854dbc7..443f60b 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,9 @@
     "name": "hyperdag-protocol",
     "version": "0.0.0",
     "license": "Apache-2.0",
-    "scripts": {},
+    "scripts": {
+        "check:sdk-claims": "node scripts/check-sdk-claims.mjs"
+    },
     "private": true,
     "dependencies": {},
     "workspaces": [
@@ -12,4 +14,4 @@
         "nx": "22.5.1"
     },
     "nx": {}
-}
\ No newline at end of file
+}
diff --git a/scripts/check-sdk-claims.mjs b/scripts/check-sdk-claims.mjs
new file mode 100755
index 0000000..2ce979c
--- /dev/null
+++ b/scripts/check-sdk-claims.mjs
@@ -0,0 +1,108 @@
+#!/usr/bin/env node
+//
+// check-sdk-claims.mjs — does the README describe the SDK npm actually serves?
+//
+// WHY THIS EXISTS. This README advertises `@hyperdag/trustshell` and shows call
+// sites for it: "Drop-in npm client: `shell.evaluate(...)` for HAL". Nothing tied
+// that prose to the package. `shell.evaluate` did not exist on the client at all,
+// so a reader following the README got `TypeError: shell.evaluate is not a
+// function`, and the README stayed green forever because nothing could disagree
+// with it.
+//
+// THE DISTINCTION THIS CHECK EXISTS TO MAKE, and the one that is easy to miss:
+// it compares against the PUBLISHED PACKAGE, not against source. A fix merged to
+// the SDK's `main` does NOT make this README true — the README says "npm
+// install", so what npm serves is what a reader gets. A method can be real in
+// git and absent for every user, and that gap is invisible from either repo
+// alone. (Observed exactly that way on 2026-09-04: `evaluate` merged to the SDK's
+// main while npm still served 1.3.0 without it.)
+//
+// THREE OUTCOMES. 0 VERIFIED · 2 NOT_CHECKED · 1 FAILED. A registry we could not
+// reach is NOT_CHECKED, never FAILED and never a pass: this check's whole job is
+// to know what npm serves, so not knowing is not a verdict. That direction has
+// already cost this ecosystem real time — a guard that reports FAILED when it
+// simply could not look teaches readers its red is noise.
+
+import { execFileSync } from 'node:child_process';
+import { mkdtempSync, readFileSync, rmSync, readdirSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+const PKG = '@hyperdag/trustshell';
+const README = join(import.meta.dirname, '..', 'README.md');
+
+function notChecked(why, detail) {
+  console.log('check:sdk-claims — NOT_CHECKED');
+  console.log(`  ${why}`);
+  if (detail) console.log(`  ${detail}`);
+  console.log('  This says NOTHING about the README. Re-run where npm is reachable.');
+  process.exit(2);
+}
+
+// ---- what the README claims -------------------------------------------------
+const readme = readFileSync(README, 'utf8');
+const claimed = [
+  ...new Set(
+    [...readme.matchAll(/\b(?:shell|client)\.([a-zA-Z][a-zA-Z0-9]*)\s*\(/g)].map((m) => m[1])
+  ),
+];
+
+if (claimed.length === 0) {
+  // Not a pass. If the README stopped showing call sites, this check has nothing
+  // to compare and should say so rather than reporting a clean bill of health.
+  notChecked('the README contains no `shell.<method>(` call sites to check');
+}
+
+// ---- what npm actually serves ----------------------------------------------
+const work = mkdtempSync(join(tmpdir(), 'sdk-claims-'));
+let dts;
+try {
+  execFileSync('npm', ['pack', PKG, '--silent'], { cwd: work, stdio: ['ignore', 'pipe', 'pipe'] });
+  const tgz = readdirSync(work).find((f) => f.endsWith('.tgz'));
+  if (!tgz) throw new Error('npm pack produced no tarball');
+  execFileSync('tar', ['-xzf', tgz], { cwd: work });
+  dts = readFileSync(join(work, 'package', 'dist', 'lib', 'trustshell.d.ts'), 'utf8');
+} catch (err) {
+  rmSync(work, { recursive: true, force: true });
+  notChecked(`could not fetch ${PKG} from npm`, String(err?.message ?? err).split('\n')[0]);
+}
+
+const version = (() => {
+  try {
+    return JSON.parse(readFileSync(join(work, 'package', 'package.json'), 'utf8')).version;
+  } catch {
+    return 'unknown';
+  }
+})();
+
+// Method names as they appear on the declared class surface.
+const published = new Set(
+  [...dts.matchAll(/^\s{4}(?:readonly\s+)?([a-zA-Z][a-zA-Z0-9]*)\s*[(<]/gm)].map((m) => m[1])
+);
+rmSync(work, { recursive: true, force: true });
+
+if (published.size < 5) {
+  notChecked(
+    `parsed only ${published.size} methods from ${PKG}@${version} — the .d.ts shape probably moved`,
+    'Refusing to report a pass or a failure off a parse that clearly did not work.'
+  );
+}
+
+// ---- compare ----------------------------------------------------------------
+const phantom = claimed.filter((m) => !published.has(m));
+
+if (phantom.length > 0) {
+  console.log('check:sdk-claims — FAILED');
+  console.log(`  README.md advertises ${phantom.length} method(s) that ${PKG}@${version} does not expose:`);
+  for (const m of phantom) console.log(`    ✗ shell.${m}(...)`);
+  console.log('');
+  console.log(`  A reader following this README with \`npm install ${PKG}\` gets a TypeError.`);
+  console.log('  If the method exists on the SDK\'s main branch, it is NOT published yet —');
+  console.log('  merging is not shipping, and this README points at npm. Publish, or');
+  console.log('  change the README to describe the version people can actually install.');
+  console.log(`  Published surface: ${[...published].sort().join(', ')}`);
+  process.exit(1);
+}
+
+console.log('check:sdk-claims — VERIFIED');
+console.log(`  ${claimed.length} README call site(s) all exist on ${PKG}@${version}: ${claimed.sort().join(', ')}`);