Real root cause of the blank mobile terminal (the FN-7692 remeasure guard did not
fix it and is reverted here). styles.css has a mobile-only reset
`@media (max-width: 768px) { * { max-width: 100% } }` to prevent horizontal
overflow. That universal selector also matches xterm's hidden character-measurement
subtree (`.xterm-helpers` / `.xterm-char-measure-element`). That subtree's containing
block (`.xterm-helpers`) is a 0x0 absolutely-positioned box, so `max-width: 100%`
resolves to `max-width: 0` and hard-caps xterm's character-cell measurement at 0.
FitAddon.fit() then proposes 0 columns/rows and `.xterm-screen` (plus the WebGL
canvas) collapses to 0x0 — the prompt streams in and is written into xterm's row DOM
but paints into a zero-size box, so the terminal is blank. Mobile-only, which is why
desktop always rendered fine.
Reproduced live via mobile emulation: `.xterm-char-measure-element` measured 0 while
an identical monospace span in the same container measured ~295px; `max-width: none`
on the measure element restored ~295px, and reopening the terminal with the exemption
active rendered the prompt with `.xterm-screen` sized 369x760. No amount of
remeasure/refit can fix this — the CSS re-caps the measurement to 0 every time — so
the FN-7692 CharSizeService guard is removed.
- Exempt `.xterm-helpers` / `.xterm-char-measure-element` from the mobile max-width
reset in styles.css (covers both TerminalModal and SessionTerminal)
- Revert the ineffective FN-7692 remeasure guard and its tests
- Update changeset (patch) and the docs/solutions write-up to the real root cause
Note: root cause + fix validated in the automation browser via mobile emulation
(393px, iPhone UA, forced touch), not a physical device.
Fusion-Task-Id: FN-7693
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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