fix: honor trans backend config for ssh

scripts/src/ssh.test.ts

@@ -1,10 +1,15 @@
 import { createHash } from "node:crypto";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
 import { describe, expect, test } from "bun:test";
+import type { UniDeskConfig } from "./config";
 import {
   createPosixApplyPatchFileSystem,
   createSshStdoutForwarder,
   formatSshStdoutTruncationHint,
   parseSshInvocation,
+  sshCaptureBackendPlan,
   sshStdoutStreamMaxBytes,
   sshStdoutTruncationHint,
   windowsFsReadOnlyScript,
@@ -15,6 +20,12 @@ function sha256Hex(text: string): string {
   return createHash("sha256").update(text, "utf8").digest("hex");
 }
 
+function minimalConfig(publicHost = "203.0.113.10"): UniDeskConfig {
+  return {
+    network: { publicHost },
+  } as UniDeskConfig;
+}
+
 describe("ssh windows PowerShell safety prelude", () => {
   test("shadows ConvertTo-Json and strips filesystem ETS metadata", () => {
     const prelude = windowsPowerShellScriptPrelude("C:\\test");
@@ -193,6 +204,52 @@ describe("ssh stdout bounded streaming", () => {
   });
 });
 
+describe("ssh backend selection", () => {
+  test("uses trans YAML backend-core preference without runtime docker detection", () => {
+    const dir = mkdtempSync(join(tmpdir(), "unidesk-trans-config-"));
+    const configPath = join(dir, "trans.ymal");
+    writeFileSync(configPath, [
+      "version: 1",
+      "kind: UniDeskTransConfig",
+      "ssh:",
+      "  backend: backend-core",
+      "",
+    ].join("\n"));
+    try {
+      const plan = sshCaptureBackendPlan(minimalConfig(), { UNIDESK_TRANS_CONFIG_PATH: configPath } as NodeJS.ProcessEnv);
+
+      expect(plan.backend).toBe("local-backend-core-broker");
+      expect(plan.remoteHost).toBeNull();
+      expect(plan.reason).toBe(`configured:${configPath}#ssh.backend`);
+      expect(plan.localBackendCore.backendCoreContainer).toBe(true);
+      expect(plan.localBackendCore.source).toBe(`${configPath}#ssh.backend`);
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
+  test("uses trans YAML frontend websocket preference when configured", () => {
+    const dir = mkdtempSync(join(tmpdir(), "unidesk-trans-config-"));
+    const configPath = join(dir, "trans.ymal");
+    writeFileSync(configPath, [
+      "version: 1",
+      "kind: UniDeskTransConfig",
+      "ssh:",
+      "  backend: frontend-websocket",
+      "",
+    ].join("\n"));
+    try {
+      const plan = sshCaptureBackendPlan(minimalConfig("198.51.100.4"), { UNIDESK_TRANS_CONFIG_PATH: configPath } as NodeJS.ProcessEnv);
+
+      expect(plan.backend).toBe("remote-frontend-websocket");
+      expect(plan.remoteHost).toBe("198.51.100.4");
+      expect(plan.reason).toBe(`configured:${configPath}#ssh.backend`);
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+});
+
 describe("ssh removed shell aliases", () => {
   test("reports route-aware replacement examples for trans script", () => {
     const previousEntrypoint = process.env.UNIDESK_SSH_ENTRYPOINT;