fix(desktop): resolve login shell when loading env (#26449)

Co-authored-by: Brendan Allan <14191578+Brendonovich@users.noreply.github.com>

packages/desktop/src/main/shell-env.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test"
 
-import { isNushell, mergeShellEnv, parseShellEnv } from "./shell-env"
+import { isNushell, mergeShellEnv, parseShellEnv, resolveUserShell } from "./shell-env"
 
 describe("shell env", () => {
   test("parseShellEnv supports null-delimited pairs", () => {
@@ -34,6 +34,13 @@ describe("shell env", () => {
     expect(env.OPENCODE_CLIENT).toBe("desktop")
   })
 
+  test("resolveUserShell falls back to the login shell before /bin/sh", () => {
+    expect(resolveUserShell("/custom/env-shell", "/bin/zsh")).toBe("/custom/env-shell")
+    expect(resolveUserShell(undefined, "/bin/zsh")).toBe("/bin/zsh")
+    expect(resolveUserShell(undefined, "unknown")).toBe("/bin/sh")
+    expect(resolveUserShell(undefined, undefined)).toBe("/bin/sh")
+  })
+
   test("isNushell handles path and binary name", () => {
     expect(isNushell("nu")).toBe(true)
     expect(isNushell("/opt/homebrew/bin/nu")).toBe(true)

packages/desktop/src/main/shell-env.ts

@@ -1,4 +1,5 @@
 import { spawnSync } from "node:child_process"
+import { userInfo } from "node:os"
 import { basename } from "node:path"
 import { getLogger } from "./logging"
 
@@ -6,8 +7,17 @@ const TIMEOUT = 5_000
 
 type Probe = { type: "Loaded"; value: Record<string, string> } | { type: "Timeout" } | { type: "Unavailable" }
 
+export function resolveUserShell(envShell: string | undefined, loginShell: string | null | undefined) {
+  const resolvedLoginShell = loginShell && loginShell !== "unknown" ? loginShell : undefined
+  return envShell || resolvedLoginShell || "/bin/sh"
+}
+
 export function getUserShell() {
-  return process.env.SHELL || "/bin/sh"
+  try {
+    return resolveUserShell(process.env.SHELL, userInfo().shell)
+  } catch {
+    return resolveUserShell(process.env.SHELL, undefined)
+  }
 }
 
 export function parseShellEnv(out: Buffer) {