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SSH Welcome Banner Truncation - Fix Summary

Problem

SSH welcome banner (MOTD) was truncated when connecting via PTY mode - only 3 lines visible instead of the full 24-line welcome with ASCII art.

Root Cause

SshService.connect() called _getShellEnvironment() BEFORE creating the shell session. This method executed multiple remote commands (echo $SHELL, grep /etc/passwd, test -x, echo $HOME, echo $PATH) via _client.execute().

Each execute() opens a separate SSH channel. SSH servers send MOTD only on the first channel per connection. The exec channel consumed the MOTD, so the subsequent shell channel received none.

Evidence:

  • Direct shell() with PTY: 1418 bytes, 24 lines ✓
  • execute() then shell() on same client: 309 bytes, 3 lines ✗

Fix

File: lib/domain/services/ssh_service.dart

  1. Removed the _getShellEnvironment() method (lines 535-637)
  2. Changed shell creation from: 
    session = await _client!.shell(environment: await _getShellEnvironment());
    to: 
    session = await _client!.shell(
  pty: const SSHPtyConfig(type: 'xterm', width: 80, height: 24),
);
  3. Swapped fallback order: PTY first, non-PTY as fallback

The environment variables (SHELL, TERM, LANG, HOME, PATH) are no longer explicitly set, but the SSH server provides reasonable defaults via the user's shell initialization.

Verification

Test: test/integration/ssh_pty_comparison_test.dart

Before fix:

  • Non-PTY: 1418 chars, 24 lines ✓
  • PTY: 309 chars, 3 lines ✗

After fix:

  • Non-PTY: 1418 chars, 24 lines ✓
  • PTY: 1418 chars, 24 lines ✓

Impact

  • ✅ Full welcome banner now visible in all terminal modes
  • ✅ Simplified connection logic (fewer moving parts)
  • ✅ No pre-exec race conditions
  • ⚠️ Minor: Custom environment detection removed (TERM defaults to xterm-256color via PTY config)

Related Tests

  • test/integration/ssh_pty_comparison_test.dart - Primary regression test
  • test/integration/ssh_preexec_motd_test.dart - Demonstrates the bug pattern
  • test/integration/ssh_pty_diagnostic_test.dart - Diagnostic utilities