Codeman/.changeset/c4baa514.md

aicodeman, xterm-zerolag-input

aicodeman	xterm-zerolag-input
minor	minor

Zero-lag predictive echo for Codex sessions (mosh-style write-through prediction).

Codex's per-keystroke composer forced 1.12.2 to disable the local-echo overlay (issues #218/#219/#220/#222), leaving Codex typing at full round-trip latency on remote links. This release adds a second echo mode instead of re-enabling the first: every keystroke still goes to the PTY exactly as before (byte-identical wire behavior, pinned by vm-level and end-to-end trace-equality tests), while the new PredictiveEchoAddon in xterm-zerolag-input 0.2.0 paints the predicted glyph at the predicted cell. When the real echo lands, the prediction is confirmed and its span removed (an invisible swap); mispredictions self-heal via a two-pass mismatch cascade and a TTL.

• Reconciliation reads the parsed terminal buffer, never the raw stream: full-line redraws, ECH gap painting and tmux's in-place deltas all converge to the same cells. Confirmation requires the cell match PLUS a cursor advance, so placeholder glyphs and identical repaints never false-confirm; blank cells are neutral (codex clears its placeholder on the first echo).
• Predictions paint only while the cursor sits on the measured Codex composer row (/^› /, codex-cli 0.147): trust/approval modals and wrapped continuation rows get no ghosts, deliberately falling back to real echo.
• Ships as a SEPARATE vendor/xterm-predictive-echo.js bundle: the existing zerolag bundle is byte-identical (sha256-verified), and a missing or broken bundle degrades Codex to exact 1.12.2 behavior. The per-device localEchoEnabled toggle is the kill switch.
• Claude/Gemini/OpenCode/Antigravity keep buffer mode untouched; shell stays off.
• A post-build adversarial review added the anchor-hold rule: after an unpredicted wire edit (backspace into echoed text, cleared input, IME text commits) new predictions hold until the next parsed write, so a stale displayed cursor can never mis-anchor a run.
• Tests: 55 new package tests including replay suites driven by fixtures recorded from a real codex TUI through the production tmux+strip pipeline (scripts/dev/record-codex-frames.mjs) and a 500-iteration seeded fuzz; new vm policy/wire-neutrality suites; a 10-scenario Playwright E2E against real codex covering the #218/#219/#220/#222 retests, byte-identity, and a simulated 300ms-RTT run. The package test suite now runs in CI.