diff --git a/README.md b/README.md
index cd30484..1425288 100644
--- a/README.md
+++ b/README.md
@@ -129,6 +129,10 @@ npx matrix broker stop
 Expected result: the actor run command prints JSON with `ok: true` and the
 `echo` result from `GreeterActor`.
 
+Handler names are part of the Matrix actor contract: `static accepts = { echo:
+{} }` maps to `onEcho(payload)`. Do not implement `echo(payload)` directly; the
+CLI rejects that shape before it connects to the broker.
+
 If you need the HiveCast browser proof and `pnpm doctor:hivecast` reports
 missing Chromium:
 
diff --git a/packages/cli/README.md b/packages/cli/README.md
index a3b8ffd..22e27d3 100644
--- a/packages/cli/README.md
+++ b/packages/cli/README.md
@@ -25,6 +25,10 @@ matrix config set registry https://registry.npmjs.org/
 matrix registry doctor
 ```
 
+Actor handlers use Matrix handler naming: an accepted op named `echo` is
+implemented as `onEcho(payload)`, not `echo(payload)`. `matrix actor run`
+validates this before connecting to the broker.
+
 Direct runner credentials are resolved from explicit flags, environment
 variables, package-local `.matrix`, and `~/.matrix`:
 
diff --git a/packages/cli/package.json b/packages/cli/package.json
index b7d397e..163677d 100644
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@open-matrix/cli",
-  "version": "0.1.4",
+  "version": "0.1.5",
   "description": "Matrix package-author CLI.",
   "type": "module",
   "bin": {
diff --git a/packages/cli/src/commands/actor-run.ts b/packages/cli/src/commands/actor-run.ts
index 858997f..5d51bc7 100644
--- a/packages/cli/src/commands/actor-run.ts
+++ b/packages/cli/src/commands/actor-run.ts
@@ -4,6 +4,7 @@ import * as path from 'node:path';
 import { pathToFileURL } from 'node:url';
 
 import type { MatrixActor } from '@open-matrix/core/core/MatrixActor.js';
+import { toHandlerCase } from '@open-matrix/core/engine/utils/NameUtils';
 import { RequestReply } from '@open-matrix/core/engine/remoting/RequestReply.js';
 import { MatrixRuntime } from '@open-matrix/core/runtime/MatrixRuntime.js';
 import { NatsTransport } from '@open-matrix/core/transport/NatsTransport.js';
@@ -77,6 +78,7 @@ export async function actorRunCommand(
   }
   const exportName = options.export?.trim() || 'default';
   const ActorClass = await loadActorConstructor(entryPath, exportName);
+  validateActorHandlers(ActorClass);
   const mount = options.mount?.trim() || inferMountFromEntry(entryPath);
   if (!mount) {
     throw new Error('matrix actor run requires --mount <mount> when it cannot infer a mount from the entry file');
@@ -358,6 +360,28 @@ export async function loadActorConstructor(entryPath: string, exportName: string
   throw new Error(`No actor class found as export "${exportName}". Available exports: ${available.join(', ') || '(none)'}`);
 }
 
+export function validateActorHandlers(ActorClass: ActorConstructor): void {
+  const accepts = ActorClass.accepts;
+  if (!accepts || typeof accepts !== 'object' || Array.isArray(accepts)) {
+    return;
+  }
+
+  const prototype = ActorClass.prototype as Record<string, unknown>;
+  for (const op of Object.keys(accepts)) {
+    const handlerName = `on${toHandlerCase(op)}`;
+    if (typeof prototype[handlerName] === 'function') {
+      continue;
+    }
+    const directHandler = prototype[op];
+    const directHint = typeof directHandler === 'function'
+      ? ` Found ${op}(payload); Matrix actor handlers use ${handlerName}(payload) naming.`
+      : '';
+    throw new Error(
+      `MATRIX_ACTOR_HANDLER_MISSING: ${ActorClass.name} declares static accepts.${op} but does not define ${handlerName}(payload).${directHint}`,
+    );
+  }
+}
+
 async function loadPackageBootstrap(entryPath: string, exportName: string): Promise<PackageBootstrapFunction> {
   const moduleUrl = `${pathToFileURL(entryPath).href}?matrix_package_run=${Date.now()}-${Math.random().toString(16).slice(2)}`;
   const mod = await import(moduleUrl) as Record<string, unknown>;
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index 066f386..338b96d 100644
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -48,7 +48,7 @@ export function createProgram(): Command {
   program
     .name('matrix')
     .description('Matrix SDK CLI for package authors')
-    .version('0.1.4');
+    .version('0.1.5');
 
   const broker = program
     .command('broker')
diff --git a/packages/cli/tests/unit/actor-run.spec.ts b/packages/cli/tests/unit/actor-run.spec.ts
index 4a00ab3..cfb3d14 100644
--- a/packages/cli/tests/unit/actor-run.spec.ts
+++ b/packages/cli/tests/unit/actor-run.spec.ts
@@ -8,6 +8,7 @@ import {
   loadActorConstructor,
   resolveActorRunBroker,
   resolvePackageRunSpec,
+  validateActorHandlers,
 } from '../../src/commands/actor-run.js';
 
 describe('matrix actor run', () => {
@@ -64,6 +65,18 @@ describe('matrix actor run', () => {
     }
   });
 
+  it('rejects accepts ops without onXxx handlers before broker connection', async () => {
+    class BadActor {
+      static accepts = { echo: { description: 'Echo a message' } };
+      echo(): void {}
+    }
+
+    assert.throws(
+      () => validateActorHandlers(BadActor as any),
+      /MATRIX_ACTOR_HANDLER_MISSING: BadActor declares static accepts\.echo but does not define onEcho\(payload\).*Found echo\(payload\)/u,
+    );
+  });
+
   it('resolves broker URL, root, JWT, and seed from an explicit home without Host state', () => {
     const home = fs.mkdtempSync(path.join(os.tmpdir(), 'mx-actor-run-broker-'));
     try {