Programs run via terminal(background=true, pty=true) can block forever when
they probe their terminal — device-status (ESC[5n), window-size (ESC[18t),
cursor-position (ESC[6n), or DEC private-mode (ESC[?N$p) queries — because
nothing on the PTY master side answers, and the raw query bytes leak into
captured output.
- tools/pty_query_responder.py: incremental byte scanner that strips the
handled queries from PTY output (chunk splits included) and produces
bounded replies; everything else passes through untouched.
- tools/process_registry.py: wire the responder into _pty_reader_loop
(POSIX only — ConPTY answers its own queries); flush partial escape
tails at end-of-stream.
- tests mirror the codex fixtures plus a live-PTY E2E where a subprocess
blocks on ESC[6n until answered.
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