# cmux 0.53.0 · Changelog

[ Changelog](https://cmux.com/docs/changelog)


February 18, 2026

Changed

-   CLI commands are now workspace-relative: commands use `CMUX_WORKSPACE_ID` environment variable so background agents target their own workspace instead of the user's focused workspace
-   Remove all index-based CLI APIs in favor of short ID refs (`surface:1`, `pane:2`, `workspace:3`)
-   CLI `send` and `send-key` support `--workspace` and `--surface` flags for explicit targeting
-   CLI escape sequences (`\n`, `\r`, `\t`) in `send` payloads are now handled correctly
-   `--id-format` flag is respected in text output for all list commands

Fixed

-   Fix background agents sending input to the wrong workspace
-   Fix `close-surface` rejecting cross-workspace surface refs
-   Fix malformed surface/pane/workspace/window handles passing through without error
-   Fix `--window` flag being overridden by `CMUX_WORKSPACE_ID` environment variable

[ cmux 0.52.0](https://cmux.com/docs/changelog/0.52.0) [cmux 0.54.0 ](https://cmux.com/docs/changelog/0.54.0)

Canonical: https://cmux.com/docs/changelog/0.53.0

Documentation index: https://cmux.com/llms.txt