diff --git a/packages/pic/postinstall.mjs b/packages/pic/postinstall.mjs
index bfe9176..2992a44 100644
--- a/packages/pic/postinstall.mjs
+++ b/packages/pic/postinstall.mjs
@@ -1,5 +1,5 @@
-import { chmodSync, createWriteStream } from 'node:fs';
-import { resolve, dirname } from 'node:path';
+import { chmodSync, createWriteStream, readFileSync } from 'node:fs';
+import { resolve, dirname, join } from 'node:path';
 import { pipeline } from 'node:stream/promises';
 import { createGunzip } from 'node:zlib';
 import { fileURLToPath } from 'node:url';
@@ -17,13 +17,68 @@ if (!IS_LINUX && !IS_DARWIN) {
 const IS_ARM = process.arch === 'arm64' || process.arch === 'aarch64';
 const ARCH = IS_ARM ? 'arm64' : 'x86_64';
 const PLATFORM = IS_LINUX ? `${ARCH}-linux` : `${ARCH}-darwin`;
-const VERSION = '13.0.0';
-const DOWNLOAD_PATH = `https://github.com/dfinity/pocketic/releases/download/${VERSION}/pocket-ic-${PLATFORM}.gz`;
+const DEFAULT_VERSION = 'package:13.0.0';
 
 const TARGET_PATH = resolve(__dirname, 'pocket-ic');
 
+function resolveDownloadUrl() {
+  // INIT_CWD is set by npm/pnpm/yarn to the directory where install was invoked,
+  // i.e. the dependent project root where .pocket-ic-version would live.
+  const projectRoot = process.env.INIT_CWD ?? process.cwd();
+  const versionFilePath = join(projectRoot, '.pocket-ic-version');
+
+  let versionSpec = DEFAULT_VERSION;
+  try {
+    versionSpec = readFileSync(versionFilePath, 'utf8').trim();
+  } catch (error) {
+    if (error?.code !== 'ENOENT') {
+      throw error;
+    }
+    // No version file; use default.
+  }
+
+  const colonIdx = versionSpec.indexOf(':');
+  if (colonIdx === -1) {
+    throw new Error(
+      `.pocket-ic-version: invalid format "${versionSpec}". Expected "package:<version>" or "ic:<version>".`,
+    );
+  }
+
+  const source = versionSpec.slice(0, colonIdx);
+  const version = versionSpec.slice(colonIdx + 1).trim();
+
+  if (!version) {
+    throw new Error(
+      `.pocket-ic-version: missing version in "${versionSpec}". Expected "package:<version>" or "ic:<version>".`,
+    );
+  }
+
+  if (source === 'package') {
+    return `https://github.com/dfinity/pocketic/releases/download/${version}/pocket-ic-${PLATFORM}.gz`;
+  } else if (source === 'ic') {
+    return `https://github.com/dfinity/ic/releases/download/${version}/pocket-ic-${PLATFORM}.gz`;
+  } else {
+    throw new Error(
+      `.pocket-ic-version: unknown source "${source}". Expected "package" or "ic".`,
+    );
+  }
+}
+
 async function downloadPicBinary() {
-  const response = await fetch(DOWNLOAD_PATH);
+  const downloadUrl = resolveDownloadUrl();
+  const response = await fetch(downloadUrl);
+
+  if (!response.ok) {
+    throw new Error(
+      `Failed to download pocket-ic from ${downloadUrl}: HTTP ${response.status} ${response.statusText}`,
+    );
+  }
+
+  if (!response.body) {
+    throw new Error(
+      `Failed to download pocket-ic from ${downloadUrl}: response body is empty`,
+    );
+  }
 
   await pipeline(response.body, createGunzip(), createWriteStream(TARGET_PATH));