diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 2721111..af7cea1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -2,7 +2,6 @@ name: CI
 
 on:
   pull_request:
-    branches: [main]
   push:
     branches: [main]
 
diff --git a/Dockerfile b/Dockerfile
index 2afe51e..8fd6f9f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,14 +1,16 @@
 # Stage 1 — Install dependencies
 FROM node:24.21.0-bookworm-slim AS deps
-RUN npm install -g pnpm@12.3.2
 WORKDIR /app
+COPY scripts/install-verified.mjs ./scripts/
+RUN node scripts/install-verified.mjs pnpm@12.3.2
 COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
 RUN pnpm install --frozen-lockfile
 
 # Stage 2 — Build TypeScript and prune dev dependencies
 FROM node:24.21.0-bookworm-slim AS build
-RUN npm install -g pnpm@12.3.2
 WORKDIR /app
+COPY scripts/install-verified.mjs ./scripts/
+RUN node scripts/install-verified.mjs pnpm@12.3.2
 COPY --from=deps /app/node_modules ./node_modules
 COPY package.json pnpm-lock.yaml pnpm-workspace.yaml tsconfig.json ./
 COPY src/ ./src/
diff --git a/renovate.json b/renovate.json
index ffd7bb4..9fa1e1b 100644
--- a/renovate.json
+++ b/renovate.json
@@ -13,7 +13,7 @@
       "description": "Track the pnpm version installed in the Dockerfile.",
       "customType": "regex",
       "managerFilePatterns": ["/^Dockerfile$/"],
-      "matchStrings": ["npm install -g (?<depName>pnpm)@(?<currentValue>\\S+)"],
+      "matchStrings": ["install-verified\\.mjs (?<depName>pnpm)@(?<currentValue>\\S+)"],
       "datasourceTemplate": "npm"
     }
   ],
@@ -22,6 +22,11 @@
       "description": "Keep the Node version in .node-version and the Dockerfile in one PR.",
       "matchPackageNames": ["node"],
       "groupName": "node"
+    },
+    {
+      "description": "Keep the pnpm version in package.json and the Dockerfile in one PR.",
+      "matchPackageNames": ["pnpm"],
+      "groupName": "pnpm"
     }
   ]
 }
diff --git a/scripts/install-verified.mjs b/scripts/install-verified.mjs
new file mode 100644
index 0000000..60097bc
--- /dev/null
+++ b/scripts/install-verified.mjs
@@ -0,0 +1,51 @@
+import { createHash, createVerify } from 'node:crypto';
+import { execFileSync } from 'node:child_process';
+import { writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+const REGISTRY = 'https://registry.npmjs.org';
+
+const spec = process.argv[2];
+if (!spec || !spec.includes('@')) {
+  console.error('usage: install-verified.mjs <package>@<version>');
+  process.exit(1);
+}
+
+const at = spec.lastIndexOf('@');
+const name = spec.slice(0, at);
+const version = spec.slice(at + 1);
+
+async function getJson(url) {
+  const response = await fetch(url);
+  if (!response.ok) throw new Error(`${url} responded ${response.status}`);
+  return response.json();
+}
+
+function toPem(key) {
+  return `-----BEGIN PUBLIC KEY-----\n${key.match(/.{1,64}/g).join('\n')}\n-----END PUBLIC KEY-----`;
+}
+
+const { dist } = await getJson(`${REGISTRY}/${name}/${version}`);
+const signature = dist.signatures?.[0];
+if (!signature) throw new Error(`${spec} has no registry signature`);
+
+const { keys } = await getJson(`${REGISTRY}/-/npm/v1/keys`);
+const signingKey = keys.find((candidate) => candidate.keyid === signature.keyid);
+if (!signingKey) throw new Error(`no registry key for ${signature.keyid}`);
+
+const signed = createVerify('SHA256')
+  .update(`${name}@${version}:${dist.integrity}`)
+  .verify(toPem(signingKey.key), signature.sig, 'base64');
+if (!signed) throw new Error(`${spec} failed registry signature verification`);
+
+const tarball = Buffer.from(await (await fetch(dist.tarball)).arrayBuffer());
+const digest = `sha512-${createHash('sha512').update(tarball).digest('base64')}`;
+if (digest !== dist.integrity)
+  throw new Error(`${spec} tarball does not match the signed integrity`);
+
+const path = join(tmpdir(), `${name.replace('/', '-')}-${version}.tgz`);
+writeFileSync(path, tarball);
+execFileSync('npm', ['install', '-g', path], { stdio: 'inherit' });
+
+console.log(`verified and installed ${spec}`);
diff --git a/vitest.config.ts b/vitest.config.mts
similarity index 100%
rename from vitest.config.ts
rename to vitest.config.mts