tai/research/shell-multiplexer-auto-attach/fishshell-docs-4-9-status.md

# status - query fish runtime information

## Metadata

| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | shell-multiplexer-auto-attach |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | status - query fish runtime information |
| Source URL | https://fishshell.com/docs/4.9/cmds/status.html |
| Source publisher / author | fish-shell project (fishshell.com) |
| Source type | vendor docs |
| Source date (published) | Unknown — not stated |
| Date researched | 2026-10-10 |
| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
| Research method | web search synthesis |
| Confidence | High |
| Status | Active |

## Summary

fish has no `$-`-style variable at all; the equivalent of bash/zsh's `case "$-" in *i*)` interactivity check is the `status is-interactive` subcommand (short form `status -i` / `--is-interactive`), which succeeds (exit 0) when fish is connected to a keyboard — i.e. actually interactive, independent of how it was started. A separate `status is-login` (`-l`/`--is-login`) checks login-shell status. Both subcommands are documented identically across every version mirror checked, from fish 3.1 through 4.9.

## Key findings

- `status is-interactive` is the single, direct fish replacement for the bash/zsh `case "$-" in *i*)` guard used in `PLEXER_BASHRC_BLOCK` — same semantic question ("is this shell actually interactive"), different syntax entirely.
- `status is-login` exists as a separate, distinct check — not needed by tai's plexer hook (which only cares about interactivity, not login status) but confirms fish does expose that distinction too, the same way bash's `shopt login_shell` does.
- Behavior is stable and identically worded across fish 3.1, 3.3, 3.4, 3.6, 4.0, 4.1, 4.2, 4.3, 4.4, and 4.9 doc mirrors — this is a long-established, non-fragile part of fish's interface.

## Pros / strengths

- Official vendor documentation, cross-checked across ten version mirrors with word-for-word consistent behavior — as safe a primitive as `isatty` to build on.

## Cons / limitations / caveats

- Unlike `$-`, which is a variable any shell code can inspect without a subcommand call, `status is-interactive` is a command invocation; this is a fish idiom difference, not a limitation, but worth noting since it changes how the guard composes with other conditions (fish's `if cond1; and cond2; and cond3` chaining, rather than a single `&&`-joined test expression).

## Relevance to tai

Directly the basis for the `status is-interactive` guard at the top of `FISH_PLEXER_BLOCK` in tai.py — the single most load-bearing line in that block, since `config.fish` (unlike `.bashrc`/`.zshrc`) is sourced on every fish startup regardless of interactivity (see fishshell-docs-3-4-index-initialization-files.md), making this guard do work that bash/zsh get for free from their rc files only being read for interactive shells in the first place.

## Changelog

| Date | Change |
|---|---|
| 2026-10-10 | Initial dossier created. |