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vastgrid

Where vastgrid opens files

vastgrid opens huge CSV, TSV, Parquet, JSON Lines and Excel files, and DataFrames, in six places. Each shows the same grid, DataGrid of vastgrid, with the same document, session and commands, and talks to its engine with the same messages. What differs is the engine, how the messages travel, and what the host does with the cells you write.

The entries

Section titled “The entries”
Entry Get it Where the data is read Engine Messages travel
Browser page /open/ on this site in the browser, in a Web Worker vastgrid-js workerTransport
React component npm install vastgrid and an engine where the app puts its engine vastgrid-js, vastgrid-duckdb or your own localTransport, workerTransport, httpTransport or serverFunctionTransport
Command line npx vastgrid-cli <file> DuckDB, in the command (Node.js) vastgrid-duckdb httpTransport
VS Code the extension vastgrid-vscode DuckDB, in the extension (Node.js) vastgrid-duckdb workerTransport over the webview’s messages
MCP App npx vastgrid-mcp <folder> DuckDB, in the MCP server (Node.js) vastgrid-duckdb the App’s tool calls
Notebook pip install vastgrid DuckDB, in the kernel (Python) vastgrid (Python) workerTransport over the widget’s messages

Formats

Section titled “Formats”
Entry CSV, TSV JSON Lines JSON Parquet Excel DataFrames
Browser page yes yes yes .xlsx, .xlsm
React component as its engine reads
Command line yes, also compressed yes yes yes .xlsx, .xlsm
VS Code yes, also compressed yes yes .xlsx, .xlsm
MCP App yes, also compressed yes yes yes .xlsx, .xlsm
Notebook yes, also compressed yes yes yes .xlsx pandas, Polars, PyArrow, DuckDB relations

Every entry opens the sheets of a workbook, hidden ones marked, and a file of any size. Parquet files are read in place, a row range at a time; the others are read into DuckDB, or into the memory engine within its memory limit (maxBytes, see Large files in the browser).

Editing, saving and exporting

Section titled “Editing, saving and exporting”
Entry Edits cells Saves into the file Exports
Browser page yes no: the file stays in the browser CSV, TSV, JSON, Excel, downloaded
React component when the engine writes when the engine saves (capabilities.save) the engine’s formats
Command line yes CSV and TSV, with --save (⌘S or Ctrl+S) CSV, TSV, Parquet, JSON, Excel, downloaded
VS Code yes, with undo and redo on VS Code’s stack CSV and TSV, with VS Code’s Save; Save As writes any format CSV, TSV, Parquet, JSON, Excel, where a save dialog says
MCP App yes, the person and the agent alike CSV and TSV, with --save CSV, TSV, Parquet, JSON, Excel, written on the server
Notebook yes no: the notebook reads the written cells (grid.to_pandas()) CSV, TSV, Parquet, JSON, Excel, downloaded or by grid.export

A save writes only the edited fields of a CSV or TSV file and keeps every other byte: the byte order mark, the quoting, the delimiters, the line breaks and the encoding. A file that changed on disk since it was read is not saved over. Written cells that are not saved stay with the engine until it stops. Editing cells covers both.

One grid in every entry

Section titled “One grid in every entry”

Each entry makes a store with createGridStore (vastgrid/core) over its transport and shows it with <DataGrid store={store}>; nothing in the grid knows which entry it is in.

  • Transports. workerTransport takes anything with postMessage and message events, not only a Web Worker: VS Code’s webview and the notebook’s widget carry the messages over their own channels with it. The command line uses httpTransport, and the MCP App implements Transport over its tools. See The store and transports.
  • Capabilities. The grid offers what the engine answers it can do: the Save button and ⌘S only with capabilities.save, exports in the formats of capabilities.export. VS Code saves by itself, so its webview’s engine answers save false and the editor’s dirty state follows the file.
  • The document. onDocumentChange gives the host the view: the MCP App keeps the agent’s grid in step with it, and the notebook reads it as grid.plan.
  • Keys and themes. The grid’s keys work where the host leaves them to it: VS Code acts on its own keys of saving, Undo and Redo and gives them to the grid as commands, and a notebook skips its keys while the grid has the focus. The grid follows the host’s theme, light or dark.