fix: Preserve error chains across error wrapping boundaries

src/cli/git.ts

@@ -19,7 +19,7 @@ function git(args: string[], cwd: string = process.cwd()): string {
     return execGitNonInteractive(args, { cwd });
   } catch (error) {
     const message = error instanceof Error ? error.message : String(error);
-    throw new Error(`Git command failed: git ${args.join(' ')}\n${message}`);
+    throw new Error(`Git command failed: git ${args.join(' ')}\n${message}`, { cause: error });
   }
 }
 

src/evals/index.ts

@@ -49,7 +49,7 @@ export function loadEvalFile(filePath: string): EvalFile {
   try {
     content = readFileSync(filePath, 'utf-8');
   } catch (error) {
-    throw new Error(`Failed to read ${filePath}: ${error}`);
+    throw new Error(`Failed to read ${filePath}: ${error}`, { cause: error });
   }
 
   let parsed: unknown;

src/sdk/analyze.ts

@@ -524,13 +524,14 @@ async function analyzeHunk(
             const errorMessage = error instanceof Error ? error.message : String(error);
             throw new WardenAuthenticationError(
               `Claude Code subprocess failed (${errorMessage}).\n` +
-              `This usually means the claude CLI cannot run in this environment.`
+              `This usually means the claude CLI cannot run in this environment.`,
+              { cause: error }
             );
           }
 
           // Authentication errors should surface immediately with helpful guidance
           if (isAuthenticationError(error)) {
-            throw new WardenAuthenticationError();
+            throw new WardenAuthenticationError(undefined, { cause: error });
           }
 
           // Don't retry if not a retryable error or we've exhausted retries

src/sdk/auth.ts

@@ -29,14 +29,16 @@ export function verifyAuth({ apiKey }: { apiKey?: string }): void {
     if (isNotFound) {
       throw new WardenAuthenticationError(
         'Claude Code CLI not found on PATH.\n' +
-        'Either install Claude Code (https://claude.ai/install.sh) or set an API key.'
+        'Either install Claude Code (https://claude.ai/install.sh) or set an API key.',
+        { cause: error }
       );
     }
     const detail =
       error instanceof ExecError ? error.stderr : (error as Error).message;
     throw new WardenAuthenticationError(
       `Claude Code CLI found but failed to execute: ${detail}\n` +
-      'Check that the claude binary has correct permissions and can run in this environment.'
+      'Check that the claude binary has correct permissions and can run in this environment.',
+      { cause: error }
     );
   }
 }

src/sdk/errors.ts

@@ -59,11 +59,11 @@ export function isSubprocessError(error: unknown): boolean {
 }
 
 export class WardenAuthenticationError extends Error {
-  constructor(sdkError?: string) {
+  constructor(sdkError?: string, options?: { cause?: unknown }) {
     const message = sdkError
       ? `Authentication failed: ${sdkError}\n${AUTH_ERROR_GUIDANCE}`
       : `Authentication required.${AUTH_ERROR_GUIDANCE}`;
-    super(message);
+    super(message, options);
     this.name = 'WardenAuthenticationError';
   }
 }

src/skills/remote.ts

@@ -308,7 +308,7 @@ function execGit(args: string[], options?: { cwd?: string }): string {
     return execGitNonInteractive(args, { cwd: options?.cwd });
   } catch (error) {
     const message = error instanceof Error ? error.message : String(error);
-    throw new SkillLoaderError(`Git command failed: git ${args.join(' ')}: ${message}`);
+    throw new SkillLoaderError(`Git command failed: git ${args.join(' ')}: ${message}`, { cause: error });
   }
 }
 

src/utils/exec.ts

@@ -8,10 +8,12 @@ export class ExecError extends Error {
     public readonly command: string,
     public readonly exitCode: number | null,
     public readonly stderr: string,
-    public readonly signal: string | null
+    public readonly signal: string | null,
+    public readonly code?: string,
+    options?: { cause?: unknown }
   ) {
     const details = stderr || (signal ? `Killed by signal ${signal}` : 'Unknown error');
-    super(`Command failed: ${command}\n${details}`);
+    super(`Command failed: ${command}\n${details}`, options);
     this.name = 'ExecError';
   }
 }
@@ -69,7 +71,7 @@ export function execNonInteractive(command: string, options?: ExecOptions): stri
   });
 
   if (result.error) {
-    throw new ExecError(command, null, result.error.message, null);
+    throw new ExecError(command, null, result.error.message, null, (result.error as NodeJS.ErrnoException).code, { cause: result.error });
   }
 
   if (result.status !== 0) {
@@ -103,7 +105,7 @@ export function execFileNonInteractive(
   const result = spawnSync(file, args, spawnOptions);
 
   if (result.error) {
-    throw new ExecError(command, null, result.error.message, null);
+    throw new ExecError(command, null, result.error.message, null, (result.error as NodeJS.ErrnoException).code, { cause: result.error });
   }
 
   if (result.status !== 0) {