diff --git a/apps/server/src/terminal/PtyAdapter.test.ts b/apps/server/src/terminal/PtyAdapter.test.ts
new file mode 100644
index 00000000000..f4ac9516537
--- /dev/null
+++ b/apps/server/src/terminal/PtyAdapter.test.ts
@@ -0,0 +1,34 @@
+import { assert, describe, it } from "@effect/vitest";
+import * as Schema from "effect/Schema";
+
+import * as PtyAdapter from "./PtyAdapter.ts";
+
+const isPtySpawnError = Schema.is(PtyAdapter.PtySpawnError);
+
+describe("PtySpawnError", () => {
+  it("derives messages from structural context while preserving the full cause chain", () => {
+    const spawnCause = new Error("spawn /bin/zsh ENOENT");
+    const adapterError = new PtyAdapter.PtySpawnError({
+      adapter: "node-pty",
+      shell: "/bin/zsh",
+      cause: spawnCause,
+    });
+    const managerError = new PtyAdapter.PtySpawnError({
+      adapter: "terminal-manager",
+      attemptedShells: ["/bin/zsh -o nopromptsp", "/bin/bash"],
+      cause: adapterError,
+    });
+
+    assert(isPtySpawnError(managerError));
+    assert.strictEqual(
+      managerError.message,
+      "Failed to spawn PTY process with terminal-manager. Tried shells: /bin/zsh -o nopromptsp, /bin/bash.",
+    );
+    assert.strictEqual(
+      adapterError.message,
+      "Failed to spawn PTY process '/bin/zsh' with node-pty.",
+    );
+    assert.strictEqual(managerError.cause, adapterError);
+    assert.strictEqual(adapterError.cause, spawnCause);
+  });
+});
diff --git a/apps/server/src/terminal/PtyAdapter.ts b/apps/server/src/terminal/PtyAdapter.ts
index dafb6f12f4f..67147035bb5 100644
--- a/apps/server/src/terminal/PtyAdapter.ts
+++ b/apps/server/src/terminal/PtyAdapter.ts
@@ -25,9 +25,7 @@ export class PtySpawnError extends Schema.TaggedErrorClass<PtySpawnError>()("Pty
       this.attemptedShells === undefined || this.attemptedShells.length === 0
         ? ""
         : ` Tried shells: ${this.attemptedShells.join(", ")}.`;
-    const causeMessage =
-      this.cause instanceof Error && this.cause.message.length > 0 ? ` ${this.cause.message}` : "";
-    return `Failed to spawn PTY process${shell} with ${this.adapter}.${attemptedShells}${causeMessage}`;
+    return `Failed to spawn PTY process${shell} with ${this.adapter}.${attemptedShells}`;
   }
 }