diff --git a/packages/core/src/actions/ActionRunner.ts b/packages/core/src/actions/ActionRunner.ts
index b7b4cb71e6..205ed35a77 100644
--- a/packages/core/src/actions/ActionRunner.ts
+++ b/packages/core/src/actions/ActionRunner.ts
@@ -132,6 +132,23 @@ export interface ActionDef {
   execute?: string;
   /** Target URL or identifier (for type: 'url', 'modal', 'flow') */
   target?: string;
+  /**
+   * Action body (spec `ActionSchema.body` — `HookBodySchema`). Opaque here:
+   * bodies are a SERVER-side execution surface and this runner never
+   * interprets one.
+   *
+   * L2 (`language: 'js'`) is defined as a function body run inside an isolated
+   * VM enforcing declared capabilities, `timeoutMs` and `memoryMb`. A browser
+   * has no such isolate, so "enforcing" those client-side would be decoration.
+   * L1 (`language: 'expression'`) is formula-engine (CEL) source, a different
+   * dialect from this package's `${…}` ExpressionEvaluator — running it here
+   * would diverge silently rather than fail.
+   *
+   * Consumers dispatch bodies by registering a `script` handler that POSTs to
+   * `/api/v1/actions/{object}/{action}` (see app-shell's
+   * `useConsoleActionRuntime`); the server runs the body through its sandbox.
+   */
+  body?: unknown;
   /** For type: 'url' — where to open `target`. `'new-tab'` forces a new
    *  browser tab/window, `'self'` forces same-page navigation. When omitted,
    *  external URLs open in a new tab and relative URLs navigate in place.
@@ -701,8 +718,27 @@ export class ActionRunner {
    * Supports ${} template expressions referencing data, record, user context.
    */
   private async executeScript(action: ActionDef): Promise<ActionResult> {
-    const script = action.execute || action.target;
+    // `target` is the canonical binding; `execute` is its deprecated alias
+    // (@objectstack/spec ActionSchema). Canonical wins when both are present,
+    // matching the spec's own fold and ActionPreview's `target ?? execute`.
+    // Spec >=16.1 folds `execute` into `target` and drops it at parse, so this
+    // only bites on raw, unparsed metadata — where the two readers used to
+    // disagree. Alias-only authoring still works via the fallback.
+    const script = action.target || action.execute;
     if (!script) {
+      // A spec `body` IS a script — this runner just cannot run one (see the
+      // `body` field docs). Saying "no script provided" would send the author
+      // hunting for a missing field they actually wrote, so name the real
+      // cause and the remedy instead.
+      if (action.body != null) {
+        return {
+          success: false,
+          error:
+            'Action body must be executed server-side — this client runner does not interpret ' +
+            '`body` (sandboxed JS needs an isolated VM; expression bodies use the formula engine). ' +
+            'Register a `script` handler that POSTs to /api/v1/actions/{object}/{action}.',
+        };
+      }
       return { success: false, error: 'No script provided for script action' };
     }
 
diff --git a/packages/core/src/actions/__tests__/ActionRunner.test.ts b/packages/core/src/actions/__tests__/ActionRunner.test.ts
index e92ac1f69c..b16ec661f1 100644
--- a/packages/core/src/actions/__tests__/ActionRunner.test.ts
+++ b/packages/core/src/actions/__tests__/ActionRunner.test.ts
@@ -200,7 +200,7 @@ describe('ActionRunner', () => {
       expect(result.data).toBe(101);
     });
 
-    it('should evaluate script with string target fallback', async () => {
+    it('should evaluate script from the canonical target field', async () => {
       const result = await runner.execute({
         type: 'script',
         target: 'data.name',
@@ -209,12 +209,58 @@ describe('ActionRunner', () => {
       expect(result.data).toBe('Test');
     });
 
+    it('should prefer canonical target over the deprecated execute alias', async () => {
+      // Spec >=16.1 folds `execute` into `target` at parse, so the two keys only
+      // coexist on raw metadata. When they do, canonical wins — the same
+      // precedence ActionPreview and the spec's own fold already use.
+      const result = await runner.execute({
+        type: 'script',
+        target: 'data.name',
+        execute: 'record.id + 100',
+      });
+      expect(result.success).toBe(true);
+      expect(result.data).toBe('Test');
+    });
+
     it('should fail when no script provided', async () => {
       const result = await runner.execute({ type: 'script' });
       expect(result.success).toBe(false);
       expect(result.error).toContain('No script provided');
     });
 
+    it('should report a server-side body rather than claiming no script was provided', async () => {
+      // Spec-valid action: `body` IS the script, but bodies run server-side.
+      // The old message sent authors hunting for a field they had written.
+      const result = await runner.execute({
+        type: 'script',
+        body: { language: 'expression', source: 'input.amount > 1000' },
+      });
+      expect(result.success).toBe(false);
+      expect(result.error).toContain('server-side');
+      expect(result.error).not.toContain('No script provided');
+    });
+
+    it('should not interpret a js body client-side', async () => {
+      // L2 needs an isolated VM enforcing capabilities/timeout/memory — the
+      // browser has none, so this must refuse rather than approximate.
+      const result = await runner.execute({
+        type: 'script',
+        body: { language: 'js', source: 'return 1 + 1;', capabilities: [] },
+      });
+      expect(result.success).toBe(false);
+      expect(result.error).toContain('server-side');
+    });
+
+    it('should still evaluate a client-side target when a body is also present', async () => {
+      const result = await runner.execute({
+        type: 'script',
+        target: 'data.name',
+        body: { language: 'expression', source: 'input.amount > 1000' },
+      });
+      expect(result.success).toBe(true);
+      expect(result.data).toBe('Test');
+    });
+
     it('should return data as undefined for expressions referencing missing vars', async () => {
       const result = await runner.execute({
         type: 'script',