Enum ForwardError 

pub(crate) enum ForwardError {
    Transient(String),
    Fatal(String),
}

Phase B.6 (post-fix) — forward an open_new_window request to the already-running host and let this launcher exit 0.

The host writes <data-dir>/ipc-port after CEF init as port:token. We open a TCP connection to 127.0.0.1:port, send a minimal HTTP/1.1 POST to /ipc with the bearer token and a JSON body, and bail. We deliberately do NOT pull in reqwest: the launcher binary should stay tiny (~325 KB) and the protocol is fixed, so a hand-rolled request is the right tool.

Failure classification (codex P2 PR #598):

• Transient — port file missing / unreadable / malformed. The host is alive (pipe held) but mid-startup; caller exits 0 silently so the user isn’t punished for double-clicking quickly.
• Fatal — port file is readable, but the HTTP path failed (connect refused, write failed, timeout). Either a hung host or a non-running-instance source of ERROR_ACCESS_DENIED (namespace conflict, security descriptor failure). Caller surfaces the dialog so the user sees a real problem rather than a silent no-op.

Variants

Transient(String)

Fatal(String)