@@ -7,6 +7,7 @@ import * as Effect from "effect/Effect";
 import * as FileSystem from "effect/FileSystem";
 import * as Layer from "effect/Layer";
 import * as Path from "effect/Path";
+import { CliError } from "effect/cli";
 import { HttpClient } from "effect/http";
 import * as ChildProcessSpawner from "effect/process/ChildProcessSpawner";
 
@@ -690,7 +691,10 @@ it.layer(NodeServices.layer)("boot service install", (it) => {
       const other = yield* makeService(undefined, "1.2.3", path.join(otherHome, ".t3"));
       commands.length = 0;
       expect(yield* other.restart).toBe("skipped");
-      expect((yield* other.install().pipe(Effect.flip))._tag).toBe("BootServiceOtherBaseDirError");
+      const refused = yield* other.install().pipe(Effect.flip);
+      expect(refused._tag).toBe("BootServiceOtherBaseDirError");
+      // The CLI prints a user message without a stack trace.
+      expect(CliError.getUserMessage(refused)).toBe(refused.message);
       expect(yield* fs.readFileString(plan.unitPath)).toBe(unit);
       expect(commands).toEqual([]);
       expect((yield* other.status).otherBaseDir).toBe(baseDir);
 
@@ -9,6 +9,7 @@ import * as FileSystem from "effect/FileSystem";
 import * as Layer from "effect/Layer";
 import * as Option from "effect/Option";
 import * as Path from "effect/Path";
+import { CliError } from "effect/cli";
 import { HttpClient } from "effect/http";
 import * as Schema from "effect/Schema";
 
@@ -527,6 +528,11 @@ export class BootServiceOtherBaseDirError extends Schema.TaggedError<BootService
   override get message(): string {
     return `The T3 Code service on this machine serves ${this.installedBaseDir}, not ${this.baseDir}. Pass ${formatBootServiceBaseDirOption(this.installedBaseDir)} to manage it, or run \`t3 service uninstall ${formatBootServiceBaseDirOption(this.installedBaseDir)}\` first to move it; both data directories are kept.`;
   }
+
+  // A refusal the user fixes by rerunning, so the CLI prints the message, not a stack trace.
+  override get [CliError.userMessage]() {
+    return this.message;
+  }
 }
 
 export type BootServiceError =