diff --git a/dist/chunk-8gyk2127.js b/dist/chunk-73r9sqrg.js
similarity index 100%
rename from dist/chunk-8gyk2127.js
rename to dist/chunk-73r9sqrg.js
index 5060a96..6bfd9a2 100644
--- a/dist/chunk-8gyk2127.js
+++ b/dist/chunk-73r9sqrg.js
@@ -4,8 +4,8 @@ import { isatty } from "node:tty";
 var DEFAULT_PROTECTED_INPUT_MAXIMUM_BYTES = 65536;
 
 class ProtectedInputError extends Error {
-  code;
   name = "ProtectedInputError";
+  code;
   constructor(code, message) {
     super(message);
     this.code = code;
diff --git a/dist/chunk-k2mgjyx4.js b/dist/chunk-e5csbmsf.js
similarity index 100%
rename from dist/chunk-k2mgjyx4.js
rename to dist/chunk-e5csbmsf.js
index 13b23b7..188ab4f 100644
--- a/dist/chunk-k2mgjyx4.js
+++ b/dist/chunk-e5csbmsf.js
@@ -9,8 +9,8 @@ import { chmod, unlink } from "node:fs/promises";
 import { createServer, connect } from "node:net";
 import { dirname } from "node:path";
 class ControlSocketError extends Error {
-  code;
   name = "ControlSocketError";
+  code;
   constructor(code, message, options) {
     super(message, options);
     this.code = code;
diff --git a/dist/control-socket.js b/dist/control-socket.js
index 66952af..8ddec15 100644
--- a/dist/control-socket.js
+++ b/dist/control-socket.js
@@ -4,7 +4,7 @@ import {
   attachControlSocket,
   listenControlSocket,
   requestControlSocket
-} from "./chunk-k2mgjyx4.js";
+} from "./chunk-e5csbmsf.js";
 import"./chunk-xrgz1k0h.js";
 export {
   requestControlSocket,
diff --git a/dist/custody-rust.js b/dist/custody-rust.js
index 7d595ac..1cc4805 100644
--- a/dist/custody-rust.js
+++ b/dist/custody-rust.js
@@ -6,7 +6,7 @@ import {
   attachControlSocket,
   listenControlSocket,
   requestControlSocket
-} from "./chunk-k2mgjyx4.js";
+} from "./chunk-e5csbmsf.js";
 import {
   assertOwnedPath,
   ensurePrivateDirectory,
@@ -16,7 +16,7 @@ import {
   DEFAULT_PROTECTED_INPUT_MAXIMUM_BYTES,
   readProtectedDescriptor,
   readProtectedStdin
-} from "./chunk-8gyk2127.js";
+} from "./chunk-73r9sqrg.js";
 import {
   emitLocalCustodyFallback
 } from "./chunk-np3mgd4s.js";
@@ -36,10 +36,10 @@ var MAXIMUM_CONTROL_TIMEOUT_MS = 3600000;
 var publishNamePattern = /^[A-Za-z0-9][A-Za-z0-9._-]{0,126}$/u;
 
 class CustodySidecarNotFoundError extends Error {
+  name;
   platform;
   arch;
   binaryPath;
-  name;
   constructor(platform, arch, binaryPath) {
     super(`local-custody sidecar not found for ${platform}-${arch} at ${binaryPath}`);
     this.platform = platform;
@@ -50,8 +50,8 @@ class CustodySidecarNotFoundError extends Error {
 }
 
 class CustodySidecarTimeoutError extends Error {
-  timeoutMs;
   name;
+  timeoutMs;
   constructor(timeoutMs) {
     super(`local-custody sidecar did not respond within ${timeoutMs} ms`);
     this.timeoutMs = timeoutMs;
@@ -60,9 +60,9 @@ class CustodySidecarTimeoutError extends Error {
 }
 
 class CustodySidecarProtocolError extends Error {
+  name;
   reason;
   stdout;
-  name;
   constructor(reason, stdout) {
     super(`local-custody sidecar produced unparseable output: ${String(reason)}`);
     this.reason = reason;
@@ -72,9 +72,9 @@ class CustodySidecarProtocolError extends Error {
 }
 
 class CustodyError extends Error {
+  name;
   code;
   details;
-  name;
   constructor(code, details) {
     super(`local-custody sidecar op failed: ${code}`);
     this.code = code;
diff --git a/dist/index.js b/dist/index.js
index 1c7692f..bed9fad 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -9,7 +9,7 @@ import {
   attachControlSocket,
   listenControlSocket,
   requestControlSocket
-} from "./chunk-k2mgjyx4.js";
+} from "./chunk-e5csbmsf.js";
 import {
   PRIVATE_DIRECTORY_MODE,
   PRIVATE_FILE_MODE,
@@ -26,7 +26,7 @@ import {
   ProtectedInputError,
   readProtectedDescriptor,
   readProtectedStdin
-} from "./chunk-8gyk2127.js";
+} from "./chunk-73r9sqrg.js";
 // src/describe.ts
 var CUSTODY_ERROR_COPY = Object.freeze({
   "service-not-running": Object.freeze({
diff --git a/dist/protected-input.js b/dist/protected-input.js
index 0d43412..8b253b6 100644
--- a/dist/protected-input.js
+++ b/dist/protected-input.js
@@ -4,7 +4,7 @@ import {
   ProtectedInputError,
   readProtectedDescriptor,
   readProtectedStdin
-} from "./chunk-8gyk2127.js";
+} from "./chunk-73r9sqrg.js";
 export {
   readProtectedStdin,
   readProtectedDescriptor,
diff --git a/src/control-socket.ts b/src/control-socket.ts
index ecce33a..2b7fe38 100644
--- a/src/control-socket.ts
+++ b/src/control-socket.ts
@@ -22,8 +22,10 @@ export type ControlSocketErrorCode =
 /** A control request failure with a stable `code`. Messages are unchanged from earlier releases. */
 export class ControlSocketError extends Error {
   override readonly name = "ControlSocketError";
-  constructor(readonly code: ControlSocketErrorCode, message: string, options?: Readonly<{ cause?: unknown }>) {
+  readonly code: ControlSocketErrorCode;
+  constructor(code: ControlSocketErrorCode, message: string, options?: Readonly<{ cause?: unknown }>) {
     super(message, options);
+    this.code = code;
   }
 }
 
diff --git a/src/custody-rust.ts b/src/custody-rust.ts
index a57b02e..941fd0e 100644
--- a/src/custody-rust.ts
+++ b/src/custody-rust.ts
@@ -50,31 +50,43 @@ const publishNamePattern = /^[A-Za-z0-9][A-Za-z0-9._-]{0,126}$/u;
 
 export class CustodySidecarNotFoundError extends Error {
   override readonly name: "CustodySidecarNotFoundError";
+  readonly platform: string;
+  readonly arch: string;
+  readonly binaryPath: string;
   constructor(
-    readonly platform: string,
-    readonly arch: string,
-    readonly binaryPath: string,
+    platform: string,
+    arch: string,
+    binaryPath: string,
   ) {
     super(`local-custody sidecar not found for ${platform}-${arch} at ${binaryPath}`);
+    this.platform = platform;
+    this.arch = arch;
+    this.binaryPath = binaryPath;
     this.name = "CustodySidecarNotFoundError";
   }
 }
 
 export class CustodySidecarTimeoutError extends Error {
   override readonly name: "CustodySidecarTimeoutError";
-  constructor(readonly timeoutMs: number) {
+  readonly timeoutMs: number;
+  constructor(timeoutMs: number) {
     super(`local-custody sidecar did not respond within ${timeoutMs} ms`);
+    this.timeoutMs = timeoutMs;
     this.name = "CustodySidecarTimeoutError";
   }
 }
 
 export class CustodySidecarProtocolError extends Error {
   override readonly name: "CustodySidecarProtocolError";
+  readonly reason: unknown;
+  readonly stdout: string;
   constructor(
-    readonly reason: unknown,
-    readonly stdout: string,
+    reason: unknown,
+    stdout: string,
   ) {
     super(`local-custody sidecar produced unparseable output: ${String(reason)}`);
+    this.reason = reason;
+    this.stdout = stdout;
     this.name = "CustodySidecarProtocolError";
   }
 }
@@ -85,11 +97,15 @@ export class CustodySidecarProtocolError extends Error {
  */
 export class CustodyError extends Error {
   override readonly name: "CustodyError";
+  readonly code: string;
+  readonly details: Readonly<Record<string, unknown>>;
   constructor(
-    readonly code: string,
-    readonly details: Readonly<Record<string, unknown>>,
+    code: string,
+    details: Readonly<Record<string, unknown>>,
   ) {
     super(`local-custody sidecar op failed: ${code}`);
+    this.code = code;
+    this.details = details;
     this.name = "CustodyError";
   }
 }
diff --git a/src/protected-input.ts b/src/protected-input.ts
index f95ec38..e762803 100644
--- a/src/protected-input.ts
+++ b/src/protected-input.ts
@@ -8,8 +8,10 @@ export type ProtectedInputErrorCode = "protected-terminal" | "protected-unsafe-f
 /** A protected-input refusal with a stable `code` for `describeCustodyError`. */
 export class ProtectedInputError extends Error {
   override readonly name = "ProtectedInputError";
-  constructor(readonly code: ProtectedInputErrorCode, message: string) {
+  readonly code: ProtectedInputErrorCode;
+  constructor(code: ProtectedInputErrorCode, message: string) {
     super(message);
+    this.code = code;
   }
 }
 
diff --git a/tsconfig.json b/tsconfig.json
index 3259e95..b987955 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -18,6 +18,7 @@
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "useUnknownInCatchVariables": true,
+    "erasableSyntaxOnly": true,
     "allowImportingTsExtensions": true,
     "isolatedModules": true,
     "skipLibCheck": true,