refactor: unify AddResult and RemovalResult into Result<T>

src/cli/aws/__tests__/transaction-search.test.ts

@@ -163,7 +163,8 @@ describe('enableTransactionSearch', () => {
       const result = await enableTransactionSearch('us-east-1', '123456789012');
 
       expect(result.success).toBe(false);
-      expect(result.error).toContain('Insufficient permissions to enable Application Signals');
+      // @ts-expect-error -- test accesses failure-branch field
+      expect(result.error.message).toContain('Insufficient permissions to enable Application Signals');
     });
 
     it('returns error when Application Signals fails with generic error', async () => {
@@ -172,7 +173,8 @@ describe('enableTransactionSearch', () => {
       const result = await enableTransactionSearch('us-east-1', '123456789012');
 
       expect(result.success).toBe(false);
-      expect(result.error).toContain('Failed to enable Application Signals');
+      // @ts-expect-error -- test accesses failure-branch field
+      expect(result.error.message).toContain('Failed to enable Application Signals');
     });
 
     it('returns error when CloudWatch Logs policy fails with AccessDenied', async () => {
@@ -184,7 +186,8 @@ describe('enableTransactionSearch', () => {
       const result = await enableTransactionSearch('us-east-1', '123456789012');
 
       expect(result.success).toBe(false);
-      expect(result.error).toContain('Insufficient permissions to configure CloudWatch Logs policy');
+      // @ts-expect-error -- test accesses failure-branch field
+      expect(result.error.message).toContain('Insufficient permissions to configure CloudWatch Logs policy');
     });
 
     it('returns error when trace destination fails', async () => {
@@ -195,7 +198,8 @@ describe('enableTransactionSearch', () => {
       const result = await enableTransactionSearch('us-east-1', '123456789012');
 
       expect(result.success).toBe(false);
-      expect(result.error).toContain('Failed to configure trace destination');
+      // @ts-expect-error -- test accesses failure-branch field
+      expect(result.error.message).toContain('Failed to configure trace destination');
     });
 
     it('returns error when indexing rule update fails', async () => {
@@ -215,7 +219,8 @@ describe('enableTransactionSearch', () => {
       const result = await enableTransactionSearch('us-east-1', '123456789012');
 
       expect(result.success).toBe(false);
-      expect(result.error).toContain('Failed to configure indexing rules');
+      // @ts-expect-error -- test accesses failure-branch field
+      expect(result.error.message).toContain('Failed to configure indexing rules');
     });
 
     it('does not proceed to later steps when an earlier step fails', async () => {

src/cli/aws/transaction-search.ts

@@ -1,3 +1,4 @@
+import type { Result } from '../../lib/types';
 import { getErrorMessage, isAccessDeniedError } from '../errors';
 import { getCredentialProvider } from './account';
 import { arnPrefix } from './partition';
@@ -14,10 +15,7 @@ import {
   XRayClient,
 } from '@aws-sdk/client-xray';
 
-export interface TransactionSearchEnableResult {
-  success: boolean;
-  error?: string;
-}
+export type TransactionSearchEnableResult = Result;
 
 const RESOURCE_POLICY_NAME = 'TransactionSearchXRayAccess';
 
@@ -44,9 +42,9 @@ export async function enableTransactionSearch(
   } catch (err: unknown) {
     const message = getErrorMessage(err);
     if (isAccessDeniedError(err)) {
-      return { success: false, error: `Insufficient permissions to enable Application Signals: ${message}` };
+      return { success: false, error: new Error(`Insufficient permissions to enable Application Signals: ${message}`) };
     }
-    return { success: false, error: `Failed to enable Application Signals: ${message}` };
+    return { success: false, error: new Error(`Failed to enable Application Signals: ${message}`) };
   }
 
   // Step 2: Create CloudWatch Logs resource policy for X-Ray (if needed)
@@ -80,9 +78,12 @@ export async function enableTransactionSearch(
   } catch (err: unknown) {
     const message = getErrorMessage(err);
     if (isAccessDeniedError(err)) {
-      return { success: false, error: `Insufficient permissions to configure CloudWatch Logs policy: ${message}` };
+      return {
+        success: false,
+        error: new Error(`Insufficient permissions to configure CloudWatch Logs policy: ${message}`),
+      };
     }
-    return { success: false, error: `Failed to configure CloudWatch Logs policy: ${message}` };
+    return { success: false, error: new Error(`Failed to configure CloudWatch Logs policy: ${message}`) };
   }
 
   const xrayClient = new XRayClient({ region, credentials });
@@ -96,9 +97,12 @@ export async function enableTransactionSearch(
   } catch (err: unknown) {
     const message = getErrorMessage(err);
     if (isAccessDeniedError(err)) {
-      return { success: false, error: `Insufficient permissions to configure trace destination: ${message}` };
+      return {
+        success: false,
+        error: new Error(`Insufficient permissions to configure trace destination: ${message}`),
+      };
     }
-    return { success: false, error: `Failed to configure trace destination: ${message}` };
+    return { success: false, error: new Error(`Failed to configure trace destination: ${message}`) };
   }
 
   // Step 4: Set indexing to 100% on the built-in Default rule (always exists, idempotent)
@@ -112,9 +116,9 @@ export async function enableTransactionSearch(
   } catch (err: unknown) {
     const message = getErrorMessage(err);
     if (isAccessDeniedError(err)) {
-      return { success: false, error: `Insufficient permissions to configure indexing rules: ${message}` };
+      return { success: false, error: new Error(`Insufficient permissions to configure indexing rules: ${message}`) };
     }
-    return { success: false, error: `Failed to configure indexing rules: ${message}` };
+    return { success: false, error: new Error(`Failed to configure indexing rules: ${message}`) };
   }
 
   return { success: true };

src/cli/commands/add/types.ts

@@ -1,3 +1,4 @@
+import type { Result } from '../../../lib/types';
 import type {
   GatewayAuthorizerType,
   ModelProvider,
@@ -41,12 +42,7 @@ export interface AddAgentOptions extends VpcOptions {
   json?: boolean;
 }
 
-export interface AddAgentResult {
-  success: boolean;
-  agentName?: string;
-  agentPath?: string;
-  error?: string;
-}
+export type AddAgentResult = Result<{ agentName?: string; agentPath?: string }>;
 
 // Gateway types
 export interface AddGatewayOptions {
@@ -68,11 +64,7 @@ export interface AddGatewayOptions {
   json?: boolean;
 }
 
-export interface AddGatewayResult {
-  success: boolean;
-  gatewayName?: string;
-  error?: string;
-}
+export type AddGatewayResult = Result<{ gatewayName?: string }>;
 
 // Gateway Target types
 export interface AddGatewayTargetOptions {
@@ -100,12 +92,7 @@ export interface AddGatewayTargetOptions {
   json?: boolean;
 }
 
-export interface AddGatewayTargetResult {
-  success: boolean;
-  toolName?: string;
-  sourcePath?: string;
-  error?: string;
-}
+export type AddGatewayTargetResult = Result<{ toolName?: string; sourcePath?: string }>;
 
 // Memory types (v2: no owner/user concept)
 export interface AddMemoryOptions {
@@ -119,11 +106,7 @@ export interface AddMemoryOptions {
   json?: boolean;
 }
 
-export interface AddMemoryResult {
-  success: boolean;
-  memoryName?: string;
-  error?: string;
-}
+export type AddMemoryResult = Result<{ memoryName?: string }>;
 
 // Credential types (v2: credential, no owner/user concept)
 export interface AddCredentialOptions {
@@ -140,8 +123,4 @@ export interface AddCredentialOptions {
 /** @deprecated Use AddCredentialOptions */
 export type AddIdentityOptions = AddCredentialOptions;
 
-export interface AddCredentialResult {
-  success: boolean;
-  credentialName?: string;
-  error?: string;
-}
+export type AddCredentialResult = Result<{ credentialName?: string }>;

src/cli/commands/create/action.ts

@@ -57,7 +57,7 @@ export async function createProject(options: CreateProjectOptions): Promise<Crea
 
     // Fail on errors
     if (!depCheck.passed) {
-      return { success: false, error: depCheck.errors.join('\n'), warnings: depWarnings };
+      return { success: false, error: new Error(depCheck.errors.join('\n')), warnings: depWarnings };
     }
   }
 
@@ -93,7 +93,7 @@ export async function createProject(options: CreateProjectOptions): Promise<Crea
       const gitResult = await initGitRepo(projectRoot);
       if (gitResult.status === 'error') {
         onProgress?.('Initialize git repository', 'error');
-        return { success: false, error: gitResult.message, warnings: depWarnings };
+        return { success: false, error: new Error(gitResult.message), warnings: depWarnings };
       }
       onProgress?.('Initialize git repository', 'done');
     }
@@ -104,7 +104,7 @@ export async function createProject(options: CreateProjectOptions): Promise<Crea
       warnings: depWarnings.length > 0 ? depWarnings : undefined,
     };
   } catch (err) {
-    return { success: false, error: getErrorMessage(err), warnings: depWarnings };
+    return { success: false, error: new Error(getErrorMessage(err)), warnings: depWarnings };
   }
 }
 
@@ -174,7 +174,7 @@ export async function createProjectWithAgent(options: CreateWithAgentOptions): P
 
   // Fail on errors
   if (!depCheck.passed) {
-    return { success: false, error: depCheck.errors.join('\n'), warnings: depWarnings };
+    return { success: false, error: new Error(depCheck.errors.join('\n')), warnings: depWarnings };
   }
 
   // First create the base project (skip dependency check since we already did it)
@@ -217,7 +217,7 @@ export async function createProjectWithAgent(options: CreateWithAgentOptions): P
         warnings: depWarnings.length > 0 ? depWarnings : undefined,
       };
     } catch (err) {
-      return { success: false, error: getErrorMessage(err), warnings: depWarnings };
+      return { success: false, error: new Error(getErrorMessage(err)), warnings: depWarnings };
     }
   }
 
@@ -310,7 +310,7 @@ export async function createProjectWithAgent(options: CreateWithAgentOptions): P
       warnings: depWarnings.length > 0 ? depWarnings : undefined,
     };
   } catch (err) {
-    return { success: false, error: getErrorMessage(err), warnings: depWarnings };
+    return { success: false, error: new Error(getErrorMessage(err)), warnings: depWarnings };
   }
 }
 

src/cli/commands/create/command.tsx

@@ -94,7 +94,7 @@ async function handleCreateCLI(options: CreateOptions): Promise<void> {
     const result = getDryRunInfo({ name: name!, projectName, cwd, language: options.language });
     if (options.json) {
       console.log(JSON.stringify(result));
-    } else {
+    } else if (result.success) {
       console.log('Dry run - would create:');
       for (const path of result.wouldCreate ?? []) {
         console.log(`  ${path}`);
@@ -158,7 +158,7 @@ async function handleCreateCLI(options: CreateOptions): Promise<void> {
       });
 
   if (options.json) {
-    console.log(JSON.stringify(result));
+    console.log(JSON.stringify(result.success ? result : { ...result, error: result.error.message }));
   } else if (result.success) {
     printCreateSummary(projectName!, result.agentName, options.language, options.framework);
     if (options.skipInstall) {
@@ -167,7 +167,7 @@ async function handleCreateCLI(options: CreateOptions): Promise<void> {
       );
     }
   } else {
-    console.error(result.error);
+    console.error(result.error.message);
   }
 
   process.exit(result.success ? 0 : 1);

src/cli/commands/create/types.ts

@@ -1,3 +1,4 @@
+import type { Result } from '../../../lib/types';
 import type { VpcOptions } from '../shared/vpc-utils';
 
 export interface CreateOptions extends VpcOptions {
@@ -28,12 +29,10 @@ export interface CreateOptions extends VpcOptions {
   json?: boolean;
 }
 
-export interface CreateResult {
-  success: boolean;
+export type CreateResult = Result<{
   projectPath?: string;
   agentName?: string;
-  error?: string;
   dryRun?: boolean;
   wouldCreate?: string[];
   warnings?: string[];
-}
+}> & { warnings?: string[] };

src/cli/commands/deploy/actions.ts

@@ -85,7 +85,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
       logger.finalize(false);
       return {
         success: false,
-        error: `Target "${options.target}" not found in aws-targets.json`,
+        error: new Error(`Target "${options.target}" not found in aws-targets.json`),
         logPath: logger.getRelativeLogPath(),
       };
     }
@@ -114,8 +114,9 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
       logger.finalize(false);
       return {
         success: false,
-        error:
-          'This will delete all deployed resources and the CloudFormation stack. Run with --yes to confirm teardown.',
+        error: new Error(
+          'This will delete all deployed resources and the CloudFormation stack. Run with --yes to confirm teardown.'
+        ),
         logPath: logger.getRelativeLogPath(),
       };
     }
@@ -169,7 +170,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
           errorResult?.error && typeof errorResult.error === 'string' ? errorResult.error : 'Identity setup failed';
         endStep('error', errorMsg);
         logger.finalize(false);
-        return { success: false, error: errorMsg, logPath: logger.getRelativeLogPath() };
+        return { success: false, error: new Error(errorMsg), logPath: logger.getRelativeLogPath() };
       }
       identityKmsKeyArn = identityResult.kmsKeyArn;
 
@@ -201,7 +202,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
         const errorMsg = 'OAuth credential setup failed. Check the log for details.';
         endStep('error', errorMsg);
         logger.finalize(false);
-        return { success: false, error: errorMsg, logPath: logger.getRelativeLogPath() };
+        return { success: false, error: new Error(errorMsg), logPath: logger.getRelativeLogPath() };
       }
 
       // Collect OAuth credential ARNs for deployed state
@@ -242,7 +243,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
     if (stackNames.length === 0) {
       endStep('error', 'No stacks found');
       logger.finalize(false);
-      return { success: false, error: 'No stacks found to deploy', logPath: logger.getRelativeLogPath() };
+      return { success: false, error: new Error('No stacks found to deploy'), logPath: logger.getRelativeLogPath() };
     }
     const stackName = stackNames[0]!;
     endStep('success');
@@ -259,7 +260,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
         logger.finalize(false);
         return {
           success: false,
-          error: 'AWS environment needs bootstrapping. Run with --yes to auto-bootstrap.',
+          error: new Error('AWS environment needs bootstrapping. Run with --yes to auto-bootstrap.'),
           logPath: logger.getRelativeLogPath(),
         };
       }
@@ -274,7 +275,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
       logger.finalize(false);
       return {
         success: false,
-        error: deployabilityCheck.message ?? 'Stack is not in a deployable state',
+        error: new Error(deployabilityCheck.message ?? 'Stack is not in a deployable state'),
         logPath: logger.getRelativeLogPath(),
       };
     }
@@ -359,7 +360,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
         logger.finalize(false);
         return {
           success: false,
-          error: `Stack teardown failed: ${teardownError}`,
+          error: new Error(`Stack teardown failed: ${teardownError}`),
           logPath: logger.getRelativeLogPath(),
         };
       }
@@ -639,8 +640,8 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
           agentNames,
           hasGateways,
         });
-        if (tsResult.error) {
-          logger.log(`Transaction search setup warning: ${tsResult.error}`, 'warn');
+        if (!tsResult.success) {
+          logger.log(`Transaction search setup warning: ${tsResult.error.message}`, 'warn');
         } else {
           notes.push(
             'Transaction search enabled. It takes ~10 minutes for transaction search to be fully active and for traces from invocations to be indexed.'
@@ -666,7 +667,7 @@ export async function handleDeploy(options: ValidatedDeployOptions): Promise<Dep
   } catch (err: unknown) {
     logger.log(getErrorMessage(err), 'error');
     logger.finalize(false);
-    return { success: false, error: getErrorMessage(err), logPath: logger.getRelativeLogPath() };
+    return { success: false, error: new Error(getErrorMessage(err)), logPath: logger.getRelativeLogPath() };
   } finally {
     if (toolkitWrapper) {
       await toolkitWrapper.dispose();