tui: vendor vt100 with a scroll-region scrollback fix#373
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Codex pins its input box with a top-anchored DECSTBM scroll region (ESC[1;Nr). Upstream vt100 0.16.2's Grid::scroll_up only pushes scrolled-off lines to scrollback when no region is active, so codex's entire conversation was dropped from scrollback and PTY scroll-up showed nothing/garbled. xterm and xterm.js (the web client) save whenever the region's top margin is row 0. Vendor vt100 under vendor/vt100 and patch scroll_up to match (scroll_top == 0) via [patch.crates-io]. No agentd code changes -- the TUI's existing scrollback now fills correctly. Verified codex scrollback goes from empty to populated; 220 tests pass. See specs/0017-pty-scrollback-is-real-terminal-history.md.
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Problem
Scrolling back a codex session in the TUI showed an empty/garbled history. Codex pins its input box with a top-anchored DECSTBM scroll region (
ESC[1;Nr), and upstreamvt1000.16.2'sGrid::scroll_uponly saves scrolled-off lines to scrollback when no scroll region is active — so codex's entire conversation scrolled off into nothing (maxsb == 0). xterm / xterm.js (the web client) save whenever the region's top margin is row 0, which is why the webui never had this bug.Fix
Vendor
vt100undervendor/vt100(wired via[patch.crates-io]) with a one-line change toGrid::scroll_up: save the scrolled-off line wheneverscroll_top == 0, matching xterm/xterm.js. No agentd code changes — the TUI's existing scrollback path now fills correctly.Design rationale:
specs/0017-pty-scrollback-is-real-terminal-history.md.Why this, not the message log
An earlier attempt (#328, closed) rendered scroll-up from the structured
Messagestream. That dropped the tool calls / command output / diffs that make up most of a coding session — a net regression (mainwas better). This keeps the full, faithful terminal history.Verification
maxsb0 → populated, clean and in order (was completely empty before).Binary
The patch affects the TUI's terminal emulation, so the relevant binary is
agent.agentd/agentd-mcp/ adapters rebuild against the patched crate but are behavior-unchanged.The fork change is isolated to
Grid::scroll_upand marked in-source as anagentd fork patch; worth upstreaming so the vendoring can eventually be dropped.🤖 Generated with Claude Code