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Problem: Neovim can permanently stop accepting keyboard input after a large paste, or after any sufficiently large input burst. The screen still redraws and honours window resize, but typed keys have no effect and the session must be killed. A paste that triggers the freeze is applied only partially. Root cause: `src/nvim/os/input.c` holds `input_buffer[INPUT_BUFFER_SIZE]` (16386 bytes), compacted left rather than used as a ring: - `input_get()` drains the buffer by advancing `input_read_pos`, but never rewinds the cursors when it empties (`input_read_pos == input_write_pos`). - The only rewind lives in `input_enqueue_raw()`, which `input_enqueue()` reaches only inside `while (input_space() >= 19 && ptr < end)` (19 is the maximum expansion of one `<x>` key form). So once input fills the buffer to within 19 bytes of the top and is then fully drained, the cursors are pinned near the top with `input_space() < 19`. The gate never reopens, `input_enqueue()` never rewinds, and all further input is silently dropped: `input_available()` stays 0 and the editor blocks forever in `state_enter()` → `input_get()`. Redraw and resize run on independent paths, which is why the UI looks alive while the keyboard is ignored. Solution: Rewind the read/write cursors when the buffer is empty, at the start of `input_enqueue()`. The reset moves no data in the empty case and guarantees the space gate can reopen; the non-empty case self-heals as the editor drains. Test case: A reproducer (no terminal required; drives `nvim --embed` over msgpack-RPC via `nvim_input`) floods the input buffer, lets the editor drain it, then probes with `:qa!`. It shows a sharp threshold at `INPUT_BUFFER_SIZE − 18`: | `--fill` | master | with this fix | |----------|-----------|---------------| | ≤ 16367 | quits | quits | | ≥ 16368 | **hangs** | quits | - On current `master`, the freeze reproduces at `fill=16368`; the patched build quits for every fill up to 100000. - Interactive: a ~40 kB bracketed paste into Insert mode or a `:terminal` no longer freezes.