Open Shell (Dlang runtime) :: Shell Architecture :: OpenShellOrg Docs

Open Shell (Dlang runtime)

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Stance pivot

OpenShellOrg previously documented advocate Nushell, do not reinvent. That stance applied while the gap was standards and companion libraries.

The gap is now session context, display layers, control plane, and syntax modes in one runtime — large enough to ship Open Shell as our shell in Dlang, with Nushell preserved as a compatibility mode baseline, not as the implementation host.

Nushell (Rust) remains credited and recommended for users who want upstream Nu only. Open Shell is for users who want OSO layers, context chrome, and room to improve formatting without waiting on upstream.

Repository

Primary: openshellorg/open-shell (planned) — Dlang, dub.sdl, {OSO} Certified target.

Not openshellorg/nushell fork as runtime (archived direction). Rust Nushell source tree is a reference corpus for nu mode parity.

Companion repos unchanged: shell-context, terminal (shell-host), prohelp, nu-emit, project-map.

Syntax modes (one session, swappable parser)

Mode id Role Notes

oso (default)

Open Shell native syntax + structured pipelines + OSO display/context layers

Product default. Formatting and UX may diverge from Nushell where we improve clarity

nu

Nushell compatibility

Reproduce upstream behavior/format as baseline; parity tests against Nushell releases

bash

POSIX/bash-ish classical syntax

Pipes, $VAR, &&, heredocs — eval shim; label in UI may say bash not UNIX

fish (planned)

fish-style friendly syntax subset

Later; same compatibility pattern

zsh (planned)

zsh extensions where distinct from bash mode

Later; avoid pretending one mode covers all POSIX dialects

Session stores $syntax-mode (name TBD). Prompt token shows mode: grey mode: oso / mode: nu / mode: bash.

Swap: display layers — Ctrl+PgUp/Ctrl+PgDn, mode selector on Ctrl+1.

Default vs compatibility (critical)

Default oso mode is not “Nushell with patches.”

It is the syntax and rendering we own — informed by Nushell’s structured pipeline model but free to change:

  • Table/list formatting and width rules

  • Error message shape and context hints

  • Literal syntax where OSO clarity wins

  • Integration with context tokens, prompt gutter, and overlay layers (first-class)

nu mode exists so scripts, docs, and muscle memory transfer. Implement by porting/reproducing Nushell semantics in D against upstream fixtures — not by shelling out to nu binary (except optional escape hatch for parity debugging).

Nushell as baseline (how)

Artifact Use

Nushell Rust repo @ pinned tag

Reference for parser/eval behavior in nu mode

Upstream test corpus / recorded sessions

Parity oracles (subset initially)

Open Shell oso mode

New tests; no requirement to match Nu output byte-for-byte

Display golden files

Separate per mode — nu mode tracks Nu; oso mode tracks OSO spec

Phase 0: document mode matrix + fixture layout in open-shell/tests/parity/nu/. Phase 1: minimal oso parser + pipeline + one builtin; stub nu mode parser fed by fixtures. Phase 2: context + layers in runtime (link display layers).

Dlang why

  • Consistent with project-map and OSO D libraries

  • Single language for shell runtime + shell-context + terminal protocol experiments (via dlang-supplemental interaction mods)

  • Long-running process + typed pipelines fit D well

Rust remains fine for nu-emit C API and small native tools; the shell REPL is D.

Relationship to other OSO products

Product Relationship

Display layers

Implemented inside open-shell + terminal host

Persistent context

Session $context in open-shell; libs in shell-context

prohelp

Optional; shell-agnostic sibling — auto-detect help in prompt gutter when installed (not bundled)

Thesis

Still true: separate transport from presentation — Open Shell is how we ship that

Non-goals (v0)

  • 100% Nushell language coverage on day one

  • Replacing every bashism in v1 bash mode

  • Bundling prohelp or Composio

  • Calling nu subprocess as the default execution path

Typography

Default terminal/cell font: Consolas (curated for OSO chrome visual language — not "any monospace"). Users and host chrome may override; see typography for fallback stack and rationale.

Prompt and host chrome