galaxy/specs/andy/ad-hoc/session-restore-wsl-msys2-pwd/TECH.md

Session Restore PWD for WSL and Git Bash — Tech Spec

See PRODUCT.md for user-visible behavior.

Context

When Warp saves a session snapshot it records the terminal's current working directory via TerminalView::active_session_path_if_local, which calls ShellLaunchData::maybe_convert_absolute_path on the raw Unix-style $PWD string the shell reports:

• For WSL, /home/user/projects → \\WSL$\<distro>\home\user\projects (Windows UNC path).
• For MSYS2/Git Bash, /c/Users/user/projects → C:\Users\user\projects (native drive path).

So by the time the path is written into TerminalSnapshot::cwd, it is already a Windows-native path.

Relevant files:

• crates/warp_terminal/src/shell/mod.rs (768–790) — ShellLaunchData::maybe_convert_absolute_path, which performs the Unix → Windows conversion at snapshot time.
• app/src/terminal/view.rs (6506–6528) — active_session_path_if_local, which calls maybe_convert_absolute_path and is the write path into the snapshot.
• app/src/pane_group/mod.rs (1533–1570) — session restore logic that reads TerminalSnapshot::cwd and computes startup_directory.

Why we store host-native paths in sqlite

The snapshot stores cwd as a Windows-native path rather than the guest-native Unix path for three reasons:

1. CreateProcessW requires it. lpCurrentDirectory must be a Windows path. Storing it host-native means no conversion is needed at restore time.
2. is_dir() works natively. Windows can stat \\WSL$\<distro>\... paths directly, letting the restore code verify the directory still exists without any extra logic.
3. Avoids per-shell branching at restore time. Storing the guest-native path and re-converting at restore time would require extracting the distro or MSYS2 executable from shell_launch_data again — exactly the logic that caused the original bug.

Root Cause

The restore code in pane_group/mod.rs was re-running the Unix→Windows conversion on cwd, passing the already-converted Windows path back into convert_wsl_to_windows_host_path / convert_msys2_to_windows_native_path. Both functions expect a Unix-style input; given a Windows path they fail and return None, so startup_directory was always None for WSL and MSYS2 sessions, causing the restored terminal to open in the shell's default directory instead of the saved one.

The TODO(CORE-3130) comment in the old WSL branch also noted that the resulting path was being ignored downstream — a sign the whole conversion was unnecessary.

Proposed Changes

app/src/pane_group/mod.rs

Replace the shell_launch_data-aware path conversion block with a direct PathBuf::from(cwd):

let startup_directory = terminal_snapshot
    .cwd
    .map(PathBuf::from)
    .filter(|path| path.is_dir());

CreateProcessW's lpCurrentDirectory accepts both forms:

• \\WSL$\<distro>\... UNC paths — wsl.exe translates these back to Linux paths on startup.
• Native C:\... drive paths — MSYS2's bash.exe maps them to the corresponding MSYS2 path (e.g. /c/...) via its own mount table on startup.

The chosen_shell / wsl_distro / msys2_executable locals derived from shell_launch_data are no longer needed for path conversion. chosen_shell (used only for AvailableShells::get_from_shell_launch_data) is retained in a simplified form; the other two are removed. The convert_msys2_to_windows_native_path, msys2_exe_to_root, and WindowsPath imports that were used solely for the now-deleted conversion are also removed.

Testing and Validation

• Behavior 2 (WSL): Open a WSL terminal, cd to a non-default directory (e.g. ~/projects), quit Warp, relaunch. Confirm the restored WSL tab opens in ~/projects.
• Behavior 3 (MSYS2/Git Bash): Open a Git Bash terminal, cd /c/Users/<user>/projects, quit Warp, relaunch. Confirm the restored tab opens in /c/Users/<user>/projects.
• Behavior 4 (missing directory): Delete the saved directory before relaunching. Confirm the tab opens without error, falling back to the shell default.
• Behavior 5 (unaffected shells): Verify PowerShell and Cmd session restore continues to work as before.