diff --git a/extensions/matrix/index.ts b/extensions/matrix/index.ts
index 10df32f7f79..b14ce2771e6 100644
--- a/extensions/matrix/index.ts
+++ b/extensions/matrix/index.ts
@@ -1,6 +1,6 @@
 import type { OpenClawPluginApi } from "openclaw/plugin-sdk";
 import { emptyPluginConfigSchema } from "openclaw/plugin-sdk";
-import { matrixPlugin } from "./src/channel.js";
+import { ensureMatrixCryptoRuntime } from "./src/matrix/deps.js";
 import { setMatrixRuntime } from "./src/runtime.js";
 
 const plugin = {
@@ -8,8 +8,10 @@ const plugin = {
   name: "Matrix",
   description: "Matrix channel plugin (matrix-js-sdk)",
   configSchema: emptyPluginConfigSchema(),
-  register(api: OpenClawPluginApi) {
+  async register(api: OpenClawPluginApi) {
     setMatrixRuntime(api.runtime);
+    await ensureMatrixCryptoRuntime();
+    const { matrixPlugin } = await import("./src/channel.js");
     api.registerChannel({ plugin: matrixPlugin });
   },
 };
diff --git a/extensions/matrix/src/matrix/deps.test.ts b/extensions/matrix/src/matrix/deps.test.ts
new file mode 100644
index 00000000000..7c5d17d1a95
--- /dev/null
+++ b/extensions/matrix/src/matrix/deps.test.ts
@@ -0,0 +1,74 @@
+import { describe, expect, it, vi } from "vitest";
+import { ensureMatrixCryptoRuntime } from "./deps.js";
+
+const logStub = vi.fn();
+
+describe("ensureMatrixCryptoRuntime", () => {
+  it("returns immediately when matrix SDK loads", async () => {
+    const runCommand = vi.fn();
+    const requireFn = vi.fn(() => ({}));
+
+    await ensureMatrixCryptoRuntime({
+      log: logStub,
+      requireFn,
+      runCommand,
+      resolveFn: () => "/tmp/download-lib.js",
+      nodeExecutable: "/usr/bin/node",
+    });
+
+    expect(requireFn).toHaveBeenCalledTimes(1);
+    expect(runCommand).not.toHaveBeenCalled();
+  });
+
+  it("bootstraps missing crypto runtime and retries matrix SDK load", async () => {
+    let bootstrapped = false;
+    const requireFn = vi.fn(() => {
+      if (!bootstrapped) {
+        throw new Error(
+          "Cannot find module '@matrix-org/matrix-sdk-crypto-nodejs-linux-x64-gnu' (required by matrix sdk)",
+        );
+      }
+      return {};
+    });
+    const runCommand = vi.fn(async () => {
+      bootstrapped = true;
+      return { code: 0, stdout: "", stderr: "" };
+    });
+
+    await ensureMatrixCryptoRuntime({
+      log: logStub,
+      requireFn,
+      runCommand,
+      resolveFn: () => "/tmp/download-lib.js",
+      nodeExecutable: "/usr/bin/node",
+    });
+
+    expect(runCommand).toHaveBeenCalledWith({
+      argv: ["/usr/bin/node", "/tmp/download-lib.js"],
+      cwd: "/tmp",
+      timeoutMs: 300_000,
+      env: { COREPACK_ENABLE_DOWNLOAD_PROMPT: "0" },
+    });
+    expect(requireFn).toHaveBeenCalledTimes(2);
+  });
+
+  it("rethrows non-crypto module errors without bootstrapping", async () => {
+    const runCommand = vi.fn();
+    const requireFn = vi.fn(() => {
+      throw new Error("Cannot find module '@vector-im/matrix-bot-sdk'");
+    });
+
+    await expect(
+      ensureMatrixCryptoRuntime({
+        log: logStub,
+        requireFn,
+        runCommand,
+        resolveFn: () => "/tmp/download-lib.js",
+        nodeExecutable: "/usr/bin/node",
+      }),
+    ).rejects.toThrow("Cannot find module '@vector-im/matrix-bot-sdk'");
+
+    expect(runCommand).not.toHaveBeenCalled();
+    expect(requireFn).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/extensions/matrix/src/matrix/deps.ts b/extensions/matrix/src/matrix/deps.ts
index 6941af8af68..c1e9957fe23 100644
--- a/extensions/matrix/src/matrix/deps.ts
+++ b/extensions/matrix/src/matrix/deps.ts
@@ -5,6 +5,27 @@ import { fileURLToPath } from "node:url";
 import { runPluginCommandWithTimeout, type RuntimeEnv } from "openclaw/plugin-sdk";
 
 const MATRIX_SDK_PACKAGE = "@vector-im/matrix-bot-sdk";
+const MATRIX_CRYPTO_DOWNLOAD_HELPER = "@matrix-org/matrix-sdk-crypto-nodejs/download-lib.js";
+
+function formatCommandError(result: { stderr: string; stdout: string }): string {
+  const stderr = result.stderr.trim();
+  if (stderr) {
+    return stderr;
+  }
+  const stdout = result.stdout.trim();
+  if (stdout) {
+    return stdout;
+  }
+  return "unknown error";
+}
+
+function isMissingMatrixCryptoRuntimeError(err: unknown): boolean {
+  const message = err instanceof Error ? err.message : String(err ?? "");
+  return (
+    message.includes("Cannot find module") &&
+    message.includes("@matrix-org/matrix-sdk-crypto-nodejs-")
+  );
+}
 
 export function isMatrixSdkAvailable(): boolean {
   try {
@@ -21,6 +42,51 @@ function resolvePluginRoot(): string {
   return path.resolve(currentDir, "..", "..");
 }
 
+export async function ensureMatrixCryptoRuntime(
+  params: {
+    log?: (message: string) => void;
+    requireFn?: (id: string) => unknown;
+    resolveFn?: (id: string) => string;
+    runCommand?: typeof runPluginCommandWithTimeout;
+    nodeExecutable?: string;
+  } = {},
+): Promise<void> {
+  const req = createRequire(import.meta.url);
+  const requireFn = params.requireFn ?? ((id: string) => req(id));
+  const resolveFn = params.resolveFn ?? ((id: string) => req.resolve(id));
+  const runCommand = params.runCommand ?? runPluginCommandWithTimeout;
+  const nodeExecutable = params.nodeExecutable ?? process.execPath;
+
+  try {
+    requireFn(MATRIX_SDK_PACKAGE);
+    return;
+  } catch (err) {
+    if (!isMissingMatrixCryptoRuntimeError(err)) {
+      throw err;
+    }
+  }
+
+  const scriptPath = resolveFn(MATRIX_CRYPTO_DOWNLOAD_HELPER);
+  params.log?.("matrix: crypto runtime missing; downloading platform library…");
+  const result = await runCommand({
+    argv: [nodeExecutable, scriptPath],
+    cwd: path.dirname(scriptPath),
+    timeoutMs: 300_000,
+    env: { COREPACK_ENABLE_DOWNLOAD_PROMPT: "0" },
+  });
+  if (result.code !== 0) {
+    throw new Error(`Matrix crypto runtime bootstrap failed: ${formatCommandError(result)}`);
+  }
+
+  try {
+    requireFn(MATRIX_SDK_PACKAGE);
+  } catch (err) {
+    throw new Error(
+      `Matrix crypto runtime remains unavailable after bootstrap: ${err instanceof Error ? err.message : String(err)}`,
+    );
+  }
+}
+
 export async function ensureMatrixSdkInstalled(params: {
   runtime: RuntimeEnv;
   confirm?: (message: string) => Promise<boolean>;