The measurement identified realized surfaces by counting shell processes, which
is what was available while probing. morning-driver, building against this
document, found a cheaper and stronger test in the sdef: `working directory` is
readable on a terminal, and a surface with no shell process reports it EMPTY -
exactly the ghost signature the broken creation API produces.
That turns "has this surface been realized" from an inference into a
machine-checkable question, which is the guard anything driving Ghostty needs
before it types into a pane.
The same property answers one of the document's own open questions: it goes
empty when a shell exits and returns when the prompt is back, so "has this pane
returned to a prompt" can be polled rather than guessed at with a delay.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011eKRzhD1RqY2MxvDEkrJAM
Kjell Tore Guttormsen
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