fix(ssh): survive csh/tcsh login shells when running multiline relay commands

src/main/ssh/ssh-connection-utils.ts

@@ -95,7 +95,14 @@ export function shellEscape(s: string): string {
 export function wrapRemoteCommandForPosixShell(command: string): string {
   // Why: sshd asks the user's login shell to parse exec commands. Orca emits
   // POSIX sh snippets; `exec` avoids leaving that shell around for relay bridges.
-  return `exec /bin/sh -c ${shellEscape(command)}`
+  if (!command.includes('\n')) {
+    return `exec /bin/sh -c ${shellEscape(command)}`
+  }
+  // Why: csh/tcsh login shells re-parse each line of a quoted multiline
+  // argument and never reach /bin/sh (#8701). Collapse to one line and let
+  // /bin/sh rebuild the script; eval keeps stdin free for streaming commands.
+  const encoded = command.replace(/\\/g, '\\\\').replace(/\n/g, '\\n')
+  return `exec /bin/sh -c ${shellEscape(`eval "$(printf %b ${shellEscape(encoded)})"`)}`
 }
 
 export type SshExecOptions = {

src/main/ssh/ssh-remote-command-wrapping.test.ts

@@ -0,0 +1,81 @@
+import { spawnSync } from 'node:child_process'
+import { describe, expect, it } from 'vitest'
+import { wrapRemoteCommandForPosixShell } from './ssh-connection-utils'
+
+// Why: sshd hands the wrapped command string to the user's login shell with
+// `-c`, so running `<shell> -c <wrapped>` locally reproduces the remote parse
+// exactly — including the csh/tcsh multiline re-parse failure from #8701.
+const LOGIN_SHELLS = ['/bin/sh', '/bin/bash', '/bin/zsh', '/bin/dash', '/bin/csh', '/bin/tcsh']
+const availableShells =
+  process.platform === 'win32'
+    ? []
+    : LOGIN_SHELLS.filter((shell) => spawnSync(shell, ['-c', 'exit 0']).status === 0)
+
+function runViaLoginShell(
+  loginShell: string,
+  wrapped: string,
+  input?: string
+): { stdout: string; status: number | null } {
+  const result = spawnSync(loginShell, ['-c', wrapped], {
+    encoding: 'utf8',
+    ...(input !== undefined ? { input } : {}),
+    timeout: 5000
+  })
+  expect(result.error).toBeUndefined()
+  return { stdout: result.stdout, status: result.status }
+}
+
+describe('wrapRemoteCommandForPosixShell', () => {
+  it('keeps single-line commands in the plain /bin/sh -c form', () => {
+    expect(wrapRemoteCommandForPosixShell('echo "${SHELL:-/bin/sh}"')).toBe(
+      `exec /bin/sh -c 'echo "\${SHELL:-/bin/sh}"'`
+    )
+  })
+
+  it('emits a single-line wrapper for multiline scripts', () => {
+    const wrapped = wrapRemoteCommandForPosixShell('echo one\necho two\n')
+    expect(wrapped).not.toContain('\n')
+    expect(wrapped.startsWith('exec /bin/sh -c ')).toBe(true)
+  })
+
+  describe.each(availableShells)('under a %s login shell', (loginShell) => {
+    it('runs a multiline script with quotes, backslashes, and expansions intact', () => {
+      const script = [
+        'echo START',
+        `name='it'\\''s %s here'`,
+        'for cand in "$HOME" /nonexistent',
+        'do',
+        '  [ -e "$cand" ] && echo "found: $cand \\\\ $name"',
+        'done',
+        'echo END'
+      ].join('\n')
+
+      const { stdout, status } = runViaLoginShell(
+        loginShell,
+        wrapRemoteCommandForPosixShell(script)
+      )
+      expect(status).toBe(0)
+      expect(stdout).toContain('START')
+      expect(stdout).toContain(`found: ${process.env.HOME} \\ it's %s here`)
+      expect(stdout).toContain('END')
+    })
+
+    it('propagates the script exit code', () => {
+      const { status } = runViaLoginShell(
+        loginShell,
+        wrapRemoteCommandForPosixShell('echo one\nexit 42\n')
+      )
+      expect(status).toBe(42)
+    })
+
+    it('leaves stdin available to the script', () => {
+      const { stdout, status } = runViaLoginShell(
+        loginShell,
+        wrapRemoteCommandForPosixShell('read line\necho "got: $line"\n'),
+        'stream-me\n'
+      )
+      expect(status).toBe(0)
+      expect(stdout).toContain('got: stream-me')
+    })
+  })
+})

src/main/ssh/ssh-remote-node-resolution.test.ts

@@ -258,6 +258,37 @@ describe('resolveRemoteNodePath', () => {
     )
   })
 
+  it('uses -c and the csh which builtin for tcsh login shells', async () => {
+    execCommandMock
+      .mockResolvedValueOnce('\n') // path probe: empty
+      .mockResolvedValueOnce('/bin/tcsh') // $SHELL
+      .mockResolvedValueOnce('/home/u/.local/bin/node\n') // which node
+      .mockResolvedValueOnce('v20.20.2\n')
+
+    await expect(resolveRemoteNodePath(conn)).resolves.toBe('/home/u/.local/bin/node')
+
+    // Why: csh/tcsh reject the combined `-lc` flag and have no `command` builtin.
+    expect(execCommandMock).toHaveBeenNthCalledWith(3, conn, `'/bin/tcsh' -c 'which node'`, {
+      wrapCommand: false,
+      timeoutMs: 8_000
+    })
+  })
+
+  it('uses -c and the csh which builtin for csh login shells', async () => {
+    execCommandMock
+      .mockResolvedValueOnce('\n') // path probe: empty
+      .mockResolvedValueOnce('/bin/csh') // $SHELL
+      .mockResolvedValueOnce('/usr/local/bin/node\n') // which node
+      .mockResolvedValueOnce('v20.20.2\n')
+
+    await expect(resolveRemoteNodePath(conn)).resolves.toBe('/usr/local/bin/node')
+
+    expect(execCommandMock).toHaveBeenNthCalledWith(3, conn, `'/bin/csh' -c 'which node'`, {
+      wrapCommand: false,
+      timeoutMs: 8_000
+    })
+  })
+
   it('uses /bin/sh when the remote shell expansion falls back to it', async () => {
     execCommandMock
       .mockResolvedValueOnce('\n') // path probe: empty

src/main/ssh/ssh-remote-node-resolution.ts

@@ -148,9 +148,11 @@ async function tryResolveViaLoginShell(
       return null
     }
 
+    // Why: csh/tcsh have no `command` builtin; `which` is their PATH resolver.
+    const probe = isCshFamilyShell(shell) ? 'which node' : 'command -v node'
     const nodePath = await execCommand(
       conn,
-      buildCommandInShell(shell, 'command -v node'),
+      buildCommandInShell(shell, probe),
       commandOptions({ wrapCommand: false, timeoutMs: LOGIN_SHELL_PROBE_TIMEOUT_MS }, options)
     )
     const candidate = nodePath.trim().split('\n')[0]
@@ -171,11 +173,18 @@ async function tryResolveViaLoginShell(
   return null
 }
 
+function isCshFamilyShell(shell: string): boolean {
+  const shellName = shell.split('/').at(-1)
+  return shellName === 'csh' || shellName === 'tcsh'
+}
+
 function buildCommandInShell(shell: string, command: string): string {
   const shellName = shell.split('/').at(-1)
   // Why: dash and POSIX sh do not require `-l`; when $SHELL falls back to
-  // /bin/sh, prefer a portable command over login-shell semantics.
-  const mode = shellName === 'sh' || shellName === 'dash' ? '-c' : '-lc'
+  // /bin/sh, prefer a portable command over login-shell semantics. csh/tcsh
+  // reject the combined `-lc` flag outright (#8701); their non-login shells
+  // still read .cshrc, where EDA/HPC farms set PATH.
+  const mode = shellName === 'sh' || shellName === 'dash' || isCshFamilyShell(shell) ? '-c' : '-lc'
   return `${shellEscape(shell)} ${mode} ${shellEscape(command)}`
 }