devenv 2.1: Nix with zsh, fish, and nushell via libghostty - devenv

# devenv 2.1: Nix with zsh, fish, and nushell via libghostty - devenv Source: [https://devenv.sh/blog/2026/05/07/devenv-21-nix-with-zsh-fish-and-nushell-via-libghostty/](https://devenv.sh/blog/2026/05/07/devenv-21-nix-with-zsh-fish-and-nushell-via-libghostty/) [https://github.com/cachix/devenv/edit/main/docs/src/blog/posts/devenv-v2.1-nix-with-zsh-fish-and-nushell-via-libghostty.md](https://github.com/cachix/devenv/edit/main/docs/src/blog/posts/devenv-v2.1-nix-with-zsh-fish-and-nushell-via-libghostty.md)[devenv 2\.0](https://devenv.sh/blog/2026/03/05/devenv-20-a-fresh-interface-to-nix/)gave you hot reload, the status line, and instant cache hits, but`devenv shell`always dropped you into bash, and you still needed`direnv`for activation on`cd`\. [devenv 2\.1](https://github.com/cachix/devenv/releases/tag/v2.1)closes both gaps and adds structured handles for coding agents\. ## Every shell, first class ### Native zsh, fish, and nushell  [devenv 2\.1](https://github.com/cachix/devenv/releases/tag/v2.1)adds native support for**zsh**,**fish**, and**nushell**\([devenv\#2718](https://github.com/cachix/devenv/pull/2718)\) with rcfile generation, environment diff tracking, reload hooks, and prompt integration implemented per shell rather than shimmed through bash\. The shell is picked from`$SHELL`, or set explicitly: ``` $ devenv shell $ SHELL=/bin/zsh devenv shell ``` Closes[devenv\#36](https://github.com/cachix/devenv/issues/36)\(open since November 2022\),[devenv\#2487](https://github.com/cachix/devenv/issues/2487), and[devenv\#2592](https://github.com/cachix/devenv/issues/2592)\. ### libghostty under the hood The virtual terminal emulator was replaced with[libghostty](https://github.com/niclas-ahden/libghostty-rs), the terminal engine from[Ghostty](https://ghostty.org/), giving devenv a single VT parser that handles every shell the same way\. Building libghostty reliably on Nix took upstream patches in[libghostty\-rs\#27](https://github.com/Uzaaft/libghostty-rs/pull/27),[ghostty\#12364](https://github.com/ghostty-org/ghostty/pull/12364), and[ghostty\#12548](https://github.com/ghostty-org/ghostty/pull/12548)\. Thanks to the Ghostty maintainers for landing them\. ### Auto reload 2\.0 required`Ctrl\+Alt\+R`to apply environment changes after a rebuild, and that keybind clashed with reverse search on macOS\.[2\.1](https://github.com/cachix/devenv/releases/tag/v2.1)re evaluates in the background on file changes and applies the new environment at the next prompt \([devenv\#2595](https://github.com/cachix/devenv/issues/2595)\)\. ## Auto activation without direnv [`devenv hook`](https://devenv.sh/auto-activation/)replaces direnv for`cd`based activation\. Add one line to your shell config: BashZshFishNushell ~/\.bashrc ``` eval "$(devenv hook bash)" ``` ~/\.zshrc ``` eval "$(devenv hook zsh)" ``` ~/\.config/fish/config\.fish ``` devenv hook fish | source ``` config\.nu ``` devenv hook nu | save --force ~/.cache/devenv/hook.nu source ~/.cache/devenv/hook.nu ``` Activation happens on`cd`into a trusted directory and reverses on the way out\. No`\.envrc`, no external dependencies\. Trust is managed with`devenv allow`and`devenv revoke`\. ## For coding agents In 2\.0, an agent that wanted to restart your API after a config change had to kill the whole devenv session or scrape the TUI through ANSI codes\.[2\.1](https://github.com/cachix/devenv/releases/tag/v2.1)replaces that with structured handles\. ### Process management from the command line New subcommands act on a running`devenv up`\([devenv\#2621](https://github.com/cachix/devenv/issues/2621)\): ``` $ devenv processes list $ devenv processes status $ devenv processes logs api $ devenv processes restart api $ devenv processes stop worker $ devenv processes start worker ``` These work with the native process manager and are also exposed as MCP tools\. ### Quiet mode by default devenv detects agents via`CLAUDECODE`,`OPENCODE\_CLIENT`, and`AI\_AGENT`and switches to quiet mode automatically, suppressing TUI progress output that would waste tokens \([devenv\#2723](https://github.com/cachix/devenv/issues/2723)\)\. Override with`\-\-verbose`or`\-\-tui`\. ## OpenTelemetry trace export [devenv 2\.1](https://github.com/cachix/devenv/releases/tag/v2.1)exports OTLP traces \([devenv\#2415](https://github.com/cachix/devenv/issues/2415)\)\. Every Nix evaluation, derivation build, task run, and managed process becomes a span with attributes like`devenv\.activity\.kind`,`devenv\.derivation\_path`,`devenv\.url`, and`devenv\.outcome`\. Enable it through the new unified`\-\-trace\-to`flag: ``` $ devenv --trace-to otlp-grpc shell $ devenv --trace-to otlp-http-protobuf:http://localhost:4318 shell ``` Three OTLP formats are supported:`otlp\-grpc`\(built in\),`otlp\-http\-protobuf`, and`otlp\-http\-json`\(opt in via cargo features\)\. Endpoints can be set on the flag or via the standard`OTEL\_EXPORTER\_OTLP\_\*`variables\. Trace context propagates across process boundaries: spawned tasks, shell commands, and processes inherit`TRACEPARENT`and`TRACESTATE`, so instrumented children show up on the same trace as the parent`devenv up`run\. `\-\-trace\-to`replaces`\-\-trace\-output`and`\-\-trace\-format`with a single`\[format:\]destination`syntax, and accepts multiple destinations: ``` $ devenv --trace-to pretty:stderr --trace-to otlp-grpc shell $ DEVENV_TRACE_TO=json:file:/tmp/trace.json,otlp-grpc devenv shell ``` ## Tasks and processes `devenv tasks run`defaults to`before`mode, so dependencies run too \([devenv\#2551](https://github.com/cachix/devenv/issues/2551)\);`\-\-mode single`restores the old behavior\. The same`\-\-mode`flag now also controls which processes`devenv up`starts \([devenv\#2721](https://github.com/cachix/devenv/issues/2721)\)\. Tasks can print messages on shell entry by writing to`$DEVENV\_TASK\_OUTPUT\_FILE`\([devenv\#2500](https://github.com/cachix/devenv/issues/2500)\)\. ## And more **Nix 2\.34\.**Multithreaded tarball unpacking, evaluator performance improvements, and REPL enhancements\. **`require\_version`in devenv\.yaml\.**Enforce a minimum devenv CLI version for your project\. Set`require\_version: true`to match the modules version, or use a constraint string like`"\>=2\.1"`\([devenv\#2391](https://github.com/cachix/devenv/issues/2391)\)\. **ROCm support\.**New`nixpkgs\.rocmSupport`option for enabling ROCm in nixpkgs configuration\. **Full stack traces on error\.**`show\-trace`is now always enabled, so evaluation errors include the full stack trace instead of a truncated message suggesting a nonexistent`\-\-show\-trace`flag \([devenv\#2725](https://github.com/cachix/devenv/issues/2725)\)\. **Ctrl\+X to stop processes\.**Stop individual processes from the TUI while keeping them visible and restartable\. **Ctrl\+H to hide stopped processes\.**Toggle hiding stopped processes in the TUI to focus on what's still running\. Failed processes stay visible, and the process count shows how many are hidden \([devenv\#2692](https://github.com/cachix/devenv/issues/2692)\)\. **Port allocation fixes\.**Port values \(`config\.processes\.<name\>\.ports\.<port\>\.value`\) now resolve correctly in`devenv shell`and`devenv tasks run`, matching the ports allocated by`devenv up`\([devenv\#2710](https://github.com/cachix/devenv/issues/2710)\)\. Ports bound to`0\.0\.0\.0`or`\[::\]`are now detected, preventing multiple devenv instances from allocating the same port \([devenv\#2567](https://github.com/cachix/devenv/issues/2567)\)\. Strict port restarts no longer fail with "port already in use" during kernel socket teardown \([devenv\#2647](https://github.com/cachix/devenv/pull/2647)\)\. **Dozens of other bug fixes\.**File watcher deduplication, import precedence, eval cache consistency, process lifecycle fixes, and terminal compatibility improvements\. See the full[changelog](https://github.com/cachix/devenv/blob/main/CHANGELOG.md)for details\. ## Breaking changes - **`devenv tasks run`**now runs dependencies by default \(`before`mode instead of`single`\)\. Use`\-\-mode single`for the old behavior\. ## Final words [Open an issue](https://github.com/cachix/devenv/issues)or join the[Discord](https://discord.gg/naMgvexb6q)with feedback\. Domen