diff --git a/.changeset/fresh-turtles-stand.md b/.changeset/fresh-turtles-stand.md
new file mode 100644
index 0000000000..b33b0f4a24
--- /dev/null
+++ b/.changeset/fresh-turtles-stand.md
@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Internal refactor of error handling
diff --git a/packages/cli/src/lib/errors.ts b/packages/cli/src/lib/errors.ts
index ef97270569..aee6d3f575 100644
--- a/packages/cli/src/lib/errors.ts
+++ b/packages/cli/src/lib/errors.ts
@@ -14,15 +14,10 @@
  * limitations under the License.
  */
 
+import { CustomErrorBase, isError, stringifyError } from '@backstage/errors';
 import chalk from 'chalk';
 
-export class CustomError extends Error {
-  get name(): string {
-    return this.constructor.name;
-  }
-}
-
-export class ExitCodeError extends CustomError {
+export class ExitCodeError extends CustomErrorBase {
   readonly code: number;
 
   constructor(code: number, command?: string) {
@@ -35,14 +30,33 @@ export class ExitCodeError extends CustomError {
   }
 }
 
-export function exitWithError(error: Error): never {
-  if (error instanceof ExitCodeError) {
-    process.stderr.write(`\n${chalk.red(error.message)}\n\n`);
-    process.exit(error.code);
-  } else {
-    process.stderr.write(`\n${chalk.red(`${error.stack}`)}\n\n`);
-    process.exit(1);
-  }
+function exit(message: string, code: number = 1): never {
+  process.stderr.write(`\n${chalk.red(message)}\n\n`);
+  process.exit(code);
 }
 
-export class NotFoundError extends CustomError {}
+export function exitWithError(error: unknown): never {
+  if (!isError(error)) {
+    process.stderr.write(`\n${chalk.red(stringifyError(error))}\n\n`);
+    process.exit(1);
+  }
+
+  switch (error.name) {
+    case 'InputError':
+      return exit(error.message, 74 /* input/output error */);
+    case 'NotFoundError':
+      return exit(error.message, 127 /* command not found */);
+    case 'NotImplementedError':
+      return exit(error.message, 64 /* command line usage error */);
+    case 'AuthenticationError':
+    case 'NotAllowedError':
+      return exit(error.message, 77 /* permissino denied */);
+    case 'ExitCodeError':
+      return exit(
+        error.message,
+        'code' in error && typeof error.code === 'number' ? error.code : 1,
+      );
+    default:
+      return exit(stringifyError(error), 1);
+  }
+}
diff --git a/packages/cli/src/lib/removed.ts b/packages/cli/src/lib/removed.ts
deleted file mode 100644
index 063882be18..0000000000
--- a/packages/cli/src/lib/removed.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Copyright 2025 The Backstage Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-export function removed(message?: string) {
-  return () => {
-    console.error(
-      message
-        ? `This command has been removed, ${message}`
-        : 'This command has been removed',
-    );
-    process.exit(1);
-  };
-}
diff --git a/packages/cli/src/lib/versioning/packages.test.ts b/packages/cli/src/lib/versioning/packages.test.ts
index 78fb1d1f5e..de6e7e1ed2 100644
--- a/packages/cli/src/lib/versioning/packages.test.ts
+++ b/packages/cli/src/lib/versioning/packages.test.ts
@@ -17,8 +17,8 @@
 import * as runObj from '../run';
 import * as yarn from './yarn';
 import { fetchPackageInfo, mapDependencies } from './packages';
-import { NotFoundError } from '../errors';
 import { createMockDirectory } from '@backstage/backend-test-utils';
+import { NotFoundError } from '@backstage/errors';
 
 jest.mock('../run', () => {
   return {
diff --git a/packages/cli/src/lib/versioning/packages.ts b/packages/cli/src/lib/versioning/packages.ts
index 7a75189a5f..223f6b8aab 100644
--- a/packages/cli/src/lib/versioning/packages.ts
+++ b/packages/cli/src/lib/versioning/packages.ts
@@ -16,9 +16,9 @@
 
 import { minimatch } from 'minimatch';
 import { getPackages } from '@manypkg/get-packages';
-import { NotFoundError } from '../errors';
 import { detectYarnVersion } from './yarn';
 import { execFile } from '../run';
+import { NotFoundError } from '@backstage/errors';
 
 const DEP_TYPES = [
   'dependencies',
diff --git a/packages/cli/src/modules/new/index.ts b/packages/cli/src/modules/new/index.ts
index 6802077507..120e77c7c0 100644
--- a/packages/cli/src/modules/new/index.ts
+++ b/packages/cli/src/modules/new/index.ts
@@ -16,7 +16,7 @@
 import { createCliPlugin } from '../../wiring/factory';
 import { Command } from 'commander';
 import { lazy } from '../../lib/lazy';
-import { removed } from '../../lib/removed';
+import { NotImplementedError } from '@backstage/errors';
 
 export default createCliPlugin({
   pluginId: 'new',
@@ -71,7 +71,9 @@ export default createCliPlugin({
       description: 'Create a new Backstage app',
       deprecated: true,
       execute: async () => {
-        removed("use 'backstage-cli new' instead")();
+        throw new NotImplementedError(
+          `This command has been removed, use 'backstage-cli new' instead`,
+        );
       },
     });
     reg.addCommand({
@@ -79,7 +81,9 @@ export default createCliPlugin({
       description: 'Create a new Backstage plugin',
       deprecated: true,
       execute: async () => {
-        removed("use 'backstage-cli new' instead")();
+        throw new NotImplementedError(
+          `This command has been removed, use 'backstage-cli new' instead`,
+        );
       },
     });
   },
diff --git a/packages/cli/src/wiring/CliInitializer.ts b/packages/cli/src/wiring/CliInitializer.ts
index 778700fe6b..15ac9837d0 100644
--- a/packages/cli/src/wiring/CliInitializer.ts
+++ b/packages/cli/src/wiring/CliInitializer.ts
@@ -21,7 +21,7 @@ import { Command } from 'commander';
 import { version } from '../lib/version';
 import chalk from 'chalk';
 import { exitWithError } from '../lib/errors';
-import { assertError } from '@backstage/errors';
+import { ForwardedError } from '@backstage/errors';
 import { isPromise } from 'util/types';
 
 type UninitializedFeature = CliFeature | Promise<{ default: CliFeature }>;
@@ -126,8 +126,7 @@ export class CliInitializer {
                 },
               });
               process.exit(0);
-            } catch (error) {
-              assertError(error);
+            } catch (error: unknown) {
               exitWithError(error);
             }
           });
@@ -142,11 +141,7 @@ export class CliInitializer {
     });
 
     process.on('unhandledRejection', rejection => {
-      if (rejection instanceof Error) {
-        exitWithError(rejection);
-      } else {
-        exitWithError(new Error(`Unknown rejection: '${rejection}'`));
-      }
+      exitWithError(new ForwardedError('Unhandled rejection', rejection));
     });
 
     program.parse(process.argv);