diff --git a/.changeset/thirty-poems-shop.md b/.changeset/thirty-poems-shop.md
new file mode 100644
index 0000000..9380199
--- /dev/null
+++ b/.changeset/thirty-poems-shop.md
@@ -0,0 +1,5 @@
+---
+'thatopen-services': minor
+---
+
+Surface structured API errors via a new RequestError class
diff --git a/src/cli/commands/publish.ts b/src/cli/commands/publish.ts
index d31130f..3408561 100644
--- a/src/cli/commands/publish.ts
+++ b/src/cli/commands/publish.ts
@@ -10,6 +10,7 @@ import {
 import { createBundleZip } from '../lib/zip';
 import { declarationsPath, readDeclarations } from '../lib/declarations';
 import { EngineServicesClient } from '../../core/client';
+import { RequestError } from '../../core/request-error';
 
 export const publishCommand = new Command('publish')
   .description('Build and publish the project to the ThatOpen platform')
@@ -148,21 +149,31 @@ export const publishCommand = new Command('publish')
 
         console.log('Published successfully!');
       } catch (err) {
-        const message = (err as Error).message || String(err);
-        if (message.includes('401') || message.includes('403')) {
-          console.error(
-            'Authentication failed. Check your token with `thatopen login`.',
-          );
-        } else if (
-          message.includes('fetch') ||
-          message.includes('ECONNREFUSED')
-        ) {
-          console.error(
-            'Could not connect to the platform. Is the API URL correct?',
-          );
-          console.error(`  API URL: ${config.apiUrl}`);
+        if (err instanceof RequestError) {
+          if (err.code === 'LIMIT_EXCEEDED') {
+            console.error(err.message);
+          } else if (err.status === 401) {
+            console.error(
+              'Authentication failed. Check your token with `thatopen login`.',
+            );
+          } else if (err.status === 403) {
+            console.error(`Permission denied: ${err.message}`);
+          } else {
+            console.error('Upload failed:', err.message);
+          }
         } else {
-          console.error('Upload failed:', message);
+          const message = (err as Error).message || String(err);
+          if (
+            message.includes('fetch') ||
+            message.includes('ECONNREFUSED')
+          ) {
+            console.error(
+              'Could not connect to the platform. Is the API URL correct?',
+            );
+            console.error(`  API URL: ${config.apiUrl}`);
+          } else {
+            console.error('Upload failed:', message);
+          }
         }
         process.exit(1);
       }
diff --git a/src/cli/templates/test/src/main.ts b/src/cli/templates/test/src/main.ts
index 3fd3e32..91182a4 100644
--- a/src/cli/templates/test/src/main.ts
+++ b/src/cli/templates/test/src/main.ts
@@ -797,7 +797,12 @@ async function runAllTests(resultsEl: HTMLElement, client: PlatformClient, compo
         try {
           await client.abortExecution(result.executionId);
         } catch (err) {
-          if (!(err instanceof Error && err.message.includes("4"))) throw err;
+          const status =
+            err && typeof err === "object" && "status" in err
+              ? Number((err as { status?: number }).status)
+              : 0;
+          const is4xx = status >= 400 && status < 500;
+          if (!is4xx) throw err;
         }
       }),
     );
@@ -886,7 +891,12 @@ async function runAllTests(resultsEl: HTMLElement, client: PlatformClient, compo
         try {
           await client.abortExecution(result.executionId);
         } catch (err) {
-          if (!(err instanceof Error && err.message.includes("4"))) throw err;
+          const status =
+            err && typeof err === "object" && "status" in err
+              ? Number((err as { status?: number }).status)
+              : 0;
+          const is4xx = status >= 400 && status < 500;
+          if (!is4xx) throw err;
         }
       }),
     );
diff --git a/src/core/client.test.ts b/src/core/client.test.ts
index 75b8665..d228e1e 100644
--- a/src/core/client.test.ts
+++ b/src/core/client.test.ts
@@ -224,6 +224,30 @@ describe('EngineServicesClient — HTTP contract', () => {
         client.executeComponent('comp-1', { projectId: 'foreign' }),
       ).rejects.toThrow(/403/);
     });
+
+    it('throws a RequestError exposing status, code and details from the body', async () => {
+      const body = JSON.stringify({
+        message: 'Components limit reached (10/10).',
+        code: 'LIMIT_EXCEEDED',
+        details: { limitType: 'componentsPerAccount', current: 10, max: 10 },
+      });
+      fetchMock.mockResolvedValue({
+        ok: false,
+        status: 403,
+        statusText: 'Forbidden',
+        text: async () => body,
+        json: async () => JSON.parse(body),
+      } as unknown as Response);
+      const client = new EngineServicesClient(TOKEN, API);
+      await expect(client.executeComponent('comp-1', {})).rejects.toMatchObject(
+        {
+          name: 'RequestError',
+          status: 403,
+          code: 'LIMIT_EXCEEDED',
+          message: 'Components limit reached (10/10).',
+        },
+      );
+    });
   });
 
   describe('file version metadata', () => {
diff --git a/src/core/client.ts b/src/core/client.ts
index 7f3e332..d0e0cc5 100644
--- a/src/core/client.ts
+++ b/src/core/client.ts
@@ -22,6 +22,7 @@ import {
   Metadata,
 } from '../types/files';
 import { ThatOpenContext } from '../types/context';
+import { RequestError } from './request-error';
 
 declare global {
   interface Window {
@@ -340,9 +341,11 @@ export class EngineServicesClient {
         const textResponse = await response
           .text()
           .then((text) => text)
-          .catch(() => undefined);
-        throw new Error(
-          `Request failed with status ${response.status}: ${response.statusText} - ${textResponse}`,
+          .catch(() => '');
+        throw new RequestError(
+          response.status,
+          response.statusText,
+          textResponse,
         );
       }
 
diff --git a/src/core/request-error.test.ts b/src/core/request-error.test.ts
new file mode 100644
index 0000000..30e4f0d
--- /dev/null
+++ b/src/core/request-error.test.ts
@@ -0,0 +1,66 @@
+import { describe, it, expect } from 'vitest';
+import { RequestError } from './request-error';
+
+describe('RequestError', () => {
+  it('extracts message, code and details from a structured JSON body', () => {
+    const body = JSON.stringify({
+      message: 'Components limit reached (10/10).',
+      code: 'LIMIT_EXCEEDED',
+      details: { limitType: 'componentsPerAccount', current: 10, max: 10 },
+    });
+    const err = new RequestError(403, 'Forbidden', body);
+    expect(err.status).toBe(403);
+    expect(err.code).toBe('LIMIT_EXCEEDED');
+    expect(err.details).toEqual({
+      limitType: 'componentsPerAccount',
+      current: 10,
+      max: 10,
+    });
+    expect(err.message).toBe('Components limit reached (10/10).');
+    expect(err.body).toBe(body);
+  });
+
+  it('leaves code and details undefined when the body has only a message', () => {
+    const err = new RequestError(404, 'Not Found', JSON.stringify({
+      message: 'Item not found',
+    }));
+    expect(err.message).toBe('Item not found');
+    expect(err.code).toBeUndefined();
+    expect(err.details).toBeUndefined();
+  });
+
+  it('falls back to a status line when the body is not JSON', () => {
+    const err = new RequestError(502, 'Bad Gateway', '<html>error</html>');
+    expect(err.message).toBe('Bad Gateway (502)');
+    expect(err.code).toBeUndefined();
+    expect(err.details).toBeUndefined();
+    expect(err.body).toBe('<html>error</html>');
+  });
+
+  it('falls back to a status line for an empty body', () => {
+    const err = new RequestError(500, 'Internal Server Error', '');
+    expect(err.message).toBe('Internal Server Error (500)');
+  });
+
+  it('falls back when the JSON body is not an object', () => {
+    const err = new RequestError(400, 'Bad Request', '"just a string"');
+    expect(err.message).toBe('Bad Request (400)');
+    expect(err.code).toBeUndefined();
+  });
+
+  it('ignores non-string message and code fields', () => {
+    const err = new RequestError(400, 'Bad Request', JSON.stringify({
+      message: 123,
+      code: { nested: true },
+    }));
+    expect(err.message).toBe('Bad Request (400)');
+    expect(err.code).toBeUndefined();
+  });
+
+  it('is an instance of Error and RequestError with the right name', () => {
+    const err = new RequestError(403, 'Forbidden', '');
+    expect(err).toBeInstanceOf(Error);
+    expect(err).toBeInstanceOf(RequestError);
+    expect(err.name).toBe('RequestError');
+  });
+});
diff --git a/src/core/request-error.ts b/src/core/request-error.ts
new file mode 100644
index 0000000..fd48aff
--- /dev/null
+++ b/src/core/request-error.ts
@@ -0,0 +1,58 @@
+/**
+ * Parses an API error body. The platform returns `{ message, code?, details? }`
+ * as JSON on failures; non-JSON bodies (proxies, gateways, plain text) yield an
+ * empty result so the caller falls back to the status line.
+ */
+function parseErrorBody(body: string): {
+  message?: string;
+  code?: string;
+  details?: unknown;
+} {
+  try {
+    const json: unknown = JSON.parse(body);
+    if (json && typeof json === 'object') {
+      const obj = json as Record<string, unknown>;
+      return {
+        message: typeof obj.message === 'string' ? obj.message : undefined,
+        code: typeof obj.code === 'string' ? obj.code : undefined,
+        details: obj.details,
+      };
+    }
+  } catch {}
+  return {};
+}
+
+/**
+ * Error thrown by {@link EngineServicesClient} when the platform API responds
+ * with a non-2xx status. Exposes the HTTP `status` and — when the API returns a
+ * structured JSON body — its `code` and `details`, so callers can react to
+ * specific failures (e.g. `code === 'LIMIT_EXCEEDED'`) instead of string-
+ * matching the message.
+ *
+ * @example
+ * ```ts
+ * try {
+ *   await client.createComponent(props);
+ * } catch (err) {
+ *   if (err instanceof RequestError && err.code === 'LIMIT_EXCEEDED') {
+ *     console.error(err.message); // "Components limit reached (10/10)..."
+ *   }
+ * }
+ * ```
+ */
+export class RequestError extends Error {
+  readonly status: number;
+  readonly code?: string;
+  readonly details?: unknown;
+  readonly body: string;
+
+  constructor(status: number, statusText: string, body: string) {
+    const parsed = parseErrorBody(body);
+    super(parsed.message ?? `${statusText || 'Request failed'} (${status})`);
+    this.name = 'RequestError';
+    this.status = status;
+    this.code = parsed.code;
+    this.details = parsed.details;
+    this.body = body;
+  }
+}
diff --git a/src/index.ts b/src/index.ts
index 8cf8eac..3e76f8e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,6 @@
 export * from './core/client';
 export * from './core/platform-client';
+export * from './core/request-error';
 export * from './types/items';
 export * from './types/base';
 export * from './types/execution';