Hex editor will not discard data if not saved.

nvim/README.md

@@ -199,7 +199,7 @@ Neovim's embedded terminal launches **fish** instead of your login shell, purely
 
 `<leader>h` toggles the current buffer between normal and hex-dump view (backed by `xxd`), rather than showing both simultaneously. That's deliberate: the hex dump is just ordinary buffer text under the hood, so editing it gets normal Neovim undo/redo for free, and nothing writes to disk until an explicit `:w` — same as any other file. A plugin doing a true live simultaneous hex+ASCII view was tried first, but it manages bytes with its own logic outside normal buffer editing, which is exactly why it had no undo at all.
 
-The mapping also makes sure the buffer is actually loaded in binary mode before toggling (re-reading it with `++bin` if not) — opening a real binary file without that causes Neovim to misinterpret raw bytes as text before `xxd` even runs, surfacing as a `CONVERSION ERROR` instead of a clean hex dump.
+The mapping also makes sure the buffer is actually loaded in binary mode before toggling (re-reading it with `++bin` if not) — opening a real binary file without that causes Neovim to misinterpret raw bytes as text before `xxd` even runs, surfacing as a `CONVERSION ERROR` instead of a clean hex dump. Since that reload discards whatever's currently in the buffer, `<leader>h` refuses to run it if there are unsaved changes — save (or explicitly discard with `:e!`) first.
 
 ## Formatting and linting
 

nvim/nvim.sh

@@ -1144,8 +1144,18 @@ return {
           -- rather than a clean hex dump, and it happens BEFORE xxd
           -- ever runs. Re-reading with ++bin loads the file correctly
           -- from scratch instead of operating on an already-misread
-          -- buffer. Forced (!) since there's nothing worth preserving
-          -- from a buffer that was misread as text in the first place.
+          -- buffer.
+          --
+          -- That reload is forced (!), which discards whatever's
+          -- currently in the buffer without asking -- refuse to do it
+          -- if there are unsaved changes rather than silently losing
+          -- them. Only relevant on this first switch into hex mode:
+          -- once vim.bo.binary is already true, no reload happens and
+          -- this check doesn't apply.
+          if vim.bo.modified then
+            vim.notify("Buffer has unsaved changes -- save first (or :e! to discard) before opening hex view", vim.log.levels.WARN)
+            return
+          end
           vim.cmd('edit! ++bin %')
         end
         vim.cmd('HexToggle')