`test_tty_passthrough_to_container` asserted `int(numeric_lines[0]) > 0`
where `numeric_lines` was every `.isdigit()` token in the FULL PTY stream
— but the container's s6 boot output (cont-init diagnostics, the preinit
`uid=0 ... egid=0` line, skills-sync summaries like
`Done: 90 new, 0 updated, 0 unchanged. 90 total bundled.`) is written to
the same PTY before the `tput cols` probe runs. So the test was really
asserting on "the first number anywhere in the boot log", which passed
only by luck on whatever that first digit happened to be.
Any PR that shifts boot output flips the first digit to a stray `0` and
breaks the test with `assert 0 > 0` — even when TTY passthrough is
working perfectly (`tput cols` returns the right value). This is a latent
landmine for every Docker PR that changes boot output (e.g. adding a
bundled dependency changes the skills-sync counts).
Fix: emit the probe result behind a unique marker
(`HERMES_TTY_COLS=<cols>` / `HERMES_TTY_COLS=NO_TTY`) and parse only the
marked value, ignoring all boot-log noise. The test's real intent — verify
`docker run -t` delivers a real TTY with a positive column count — is
preserved (NO_TTY and non-numeric values still fail).
Verified against a real build, adversarially:
- Built an image with extra boot output (the markdown core-dep change from
#38649, which is what surfaced this) so the OLD logic grabs a stray `0`
-> reproduced `assert 0 > 0` locally.
- The hardened test PASSES against that same image, and against a clean
image. `tput cols` correctly returns 123 in both.
e2ea648a08