fix(cli): switch Windows console to UTF-8 on startup - #236
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…ee (#243) Reported on Windows 10 / v0.4.1: "UI is shaking and some line broken". **The shaking is frame tearing.** Ink paints by writing a whole frame to stdout — cursor home, every line, the trailing clear. On a terminal that renders as bytes arrive, the interval between the first line and the last is an interval where the screen holds half of the old frame and half of the new. That is not a Windows bug; macOS terminals just coalesce hard enough to hide it, which is how a cross-platform behaviour arrived as a Windows report. DEC private mode 2026 is the fix the terminal side already implemented: `CSI ? 2026 h` holds rendering until `CSI ? 2026 l`, so a frame appears whole or not at all. Every frame is now bracketed in one write — one, not three, because three would put the stream's own chunking between a marker and the frame it is meant to bracket. Sent unconditionally on a TTY, and safe to: an unrecognised DEC private mode is ignored, which is the whole point of "private", and it is why terminals without 2026 have taken these bytes from other TUIs for years. No probe, for the same reason `alt-screen.ts` does not probe — asking costs a round trip on a stdin something else is reading, and the fallback is exactly today's behaviour. `ATOMIC_AGENT_NO_SYNC_OUTPUT=1` opts out. Installed by patching `stdout.write` rather than by handing Ink a wrapper stream: Ink reads `columns`, `rows` and `resize` off that same object, and a proxy that forwards those subtly wrong breaks resize handling in a way far harder to see than tearing. **And there was a repaint going nowhere.** `useRotatingPlaceholder` ran its interval unconditionally, but the phrase is drawn only while the composer is empty. From the first character typed, the timer went on firing every four seconds — a `setState` at the root, a full Ink frame, for a string nobody could see — for the rest of the session. It is now gated on visibility, the same way `useSpinner` and `useAtomField` already were. The cheapest frame is the one that is never painted, and on a tearing terminal it is also the one that cannot flicker. **The broken line is not this.** That is glyph width under a non-UTF-8 Windows console code page, which PR #236 (`fix(cli): switch Windows console to UTF-8 on startup`) addresses directly. Deliberately left alone here so the two do not collide. I do not have a Windows 10 machine, so the tearing fix is reasoned and unit-tested rather than observed. The exact bytes reaching the terminal are asserted; whether Windows Terminal stops shaking needs someone on Windows to run the branch.
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Summary
On Windows, switch the console code page to UTF-8 (65001) at CLI startup so Cyrillic (and other non-ASCII) input, output and copy/paste no longer turn into mojibake.
Motivation
The Windows console defaults to the CP866 OEM code page, while Node and atomic-agent emit/consume UTF-8. The mismatch corrupts Russian text in three places at once:
╨Я╤А╨╕╨▓╨╡╤Вfor "Привет").Changes
src/cli/index.ts— addensureUtf8Console(), called at the top ofmain(). On Windows only it runschcp 65001 >nul(viaexecSync) and swallows failures (some hosts disallow changing the code page).Design constraint honored here: the fix does not touch
process.stdout/process.stderr. An earlier attempt that overrodewriteto emit raw UTF-8 bytes broke the interactive TUI (ink/readline frame rendering) — output lines "jumped" and the screen corrupted. Changing only the console code page fixes all three symptoms while leaving the stream mechanics untouched.Verification
npm run lint— clean.npm test— full suite: 20 failed / 5939 passed, identical to the pre-existingmainbaseline (same 20 environment-specific Windows failures; none introduced by this change).chcpreports65001; Russian input, output and copy/paste are correct.Notes
--use-env-proxyflag (documented separately); this change affects only the console code page.execSyncis wrapped in try/catch becausechcpcan fail on hosts that forbid changing the code page (non-interactive sessions, some terminals).