This document specifies the terminal UX of check and fmt. Command semantics live in CLI-Design.md; staging lives in ROADMAP.md.

Implementation status. v0.9 item 1 (event stream + plain renderer) is implemented, in internal/cli/render: check, fmt and check --format-before-check's formatter pass render through the plain renderer (see "Non-TTY fallback" and "Issues output"). Engine terminal events carry the matched Files, and runlog.Writer.Name() exposes the run uid used in the failures section. Item 2 (--format human|sarif|json and color) is implemented: color applies to human only, when stdout is a terminal and NO_COLOR is empty (see "Issues output"). Item 4 (filtered linters list / actions list) is implemented, in internal/cli/list.go, with per-linter file counts from engine.Matches (pkg/trunk/engine/match.go). Item 3 (TTY live view) is implemented, in internal/cli/render/live.go, screen.go and detect.go: with it all four v0.9 items are done. UI carries no compatibility constraint with trunk: the former file:line severity [rule] message lines and the N issue(s) in M file(s) summary are gone; stable machine output is --format json|sarif.

check and fmt emit an event stream (linter started, files in progress, finished, finding, failure). The human, sarif, json and github renderers consume it; the TTY live view is one consumer among others and holds no business logic: it is a decorator over the chosen renderer (render.NewLive), not a fourth format. Besides Running and the terminal events, the engine emits additive Planned, JobDone and Install* events that the live view needs (job totals, per-job completion, downloads); the plain renderers ignore them.

Implemented. The live area is drawn on stderr when stderr is a terminal, --no-progress is not set and TERM is not dumb; otherwise the plain progress lines of "Non-TTY fallback" are emitted unchanged. It is erased before the stdout report is written, so the report is byte-identical to the non-live one. Final mockup:

Checking  39% ⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ 12/31 · 3.2s
  markdownlint   ⣿⣿⣷⠀⠀ 7/47
    ⠋ docs/architecture/cache.md
    ⠙ pkg/trunk/config/ARCHITECTURE.md
  golangci-lint  ⠹
    pkg/trunk/actions/run.go, pkg/trunk/actions/run_log.go (+151)
↓ shfmt          ⠛ 4.1/12 MB

(⠛ stands for whichever Sand frame is current. The header verb is padded to 10 columns, Checking or Formatting, Installing while planned installs are unfinished.)

Rules:

• Header. Verb Checking or Formatting depending on the command (Installing while tool downloads are pending), percentage, braille bar spanning the full terminal width minus fixed prefix/suffix, done/total, elapsed time. No worker count. The bar is recomputed every frame, and the terminal size is read every 100 ms tick, so a resize is picked up without a SIGWINCH handler; below 40 columns the bar disappears and the counter stays. Elapsed is %.1fs under a minute, 1m04s after.
• Total. Units of work known once a linter is planned: one per file for per-file linters, one per batch invocation, plus the installs (so the bar does not sit at 0 during downloads). The total is fixed up front (the planned installs are announced before the first starts); a failed linter's unfinished jobs are credited so the bar still reaches 100%.
• Braille. 8 glyph states per cell (the blank braille U+2800, then ⣀ ⣄ ⣤ ⣦ ⣶ ⣷ ⣿; an empty cell is truly empty) = 7 sub-steps per character (100 columns = 700 steps; the 5-character mini-bar = 35 steps). ASCII fallback ([=== ], |/-\, v for the install glyph, ... for …, - for ·, one step per cell) with --ascii, and automatically when the locale is not UTF-8: the first non-empty of LC_ALL, LC_CTYPE, LANG must contain utf-8 or utf8 (case-insensitive), no locale at all means ASCII. TERM=dumb does not draw the live view at all (plain lines instead).
• Per-worker tree. A linter processing file by file shows a 5-character braille mini-bar plus done/total, then one line per in-flight file with a spinner. A batch linter (a single invocation over many files) shows ONLY its spinner on the linter line (no "batch" label); the files are listed on a single line a, b (+N). Long paths are shortened in the middle.
• Install rows. The ↓ glyph occupies the indentation slot (no padding before it) so linter names stay aligned with those of running linters; dedicated Sand spinner; byte progress 4.1/12 MB when Content-Length is known, spinner alone otherwise. The row is removed when the install ends (the linter row appears with its first running file). No color in the live area yet: the glyph carries the information. Known gaps: no "waiting for runtime node" state (the download layer does not expose its runtime-before-tool ordering), and the different color for install rows is deferred.
• Height. --live-height <n> and env var RTUNK_LIVE_HEIGHT; default is half the terminal height, minimum 3 lines (bar + 2); overflow is folded into a last +N workers line (hidden linter blocks and install rows). Both flags exist on check and fmt. Deliberately absent from the config file in v1 (avoid mixing rtunk keys with trunk-compatible config).

Dots:

⠋ ⠙ ⠹ ⠸ ⠼ ⠴ ⠦ ⠧ ⠇ ⠏

DotsVariant:

⣼ ⣹ ⢻ ⠿ ⡟ ⣏ ⣧ ⣶

Sand:

⠁ ⠂ ⠄ ⡀ ⡈ ⡐ ⡠ ⣀ ⣁ ⣂ ⣄ ⣌ ⣔ ⣤ ⣥ ⣦ ⣮ ⣶ ⣷ ⣿ ⡿ ⠿ ⢟ ⠟ ⡛ ⠛ ⠫ ⢋ ⠋ ⠍ ⡉ ⠉ ⠑ ⠡ ⢁

The frame index is computed from the clock (frames[t/interval % len(frames)]) so all rows of the same kind stay in sync; 80 ms per frame for Dots, 70 ms for Sand. DotsVariant is unused.

License note. These frame sets come from the author's reference (spinner variants from Zed). Licensing for rtunk is to be confirmed (Zed is GPL, but a list of braille characters is trivial).

No redraw, no spinner: one stderr line per finished linter, then the report on stdout. Honors NO_COLOR and --no-progress (a flag trunk also has; on check and fmt, it suppresses only the per-linter progress lines, not warnings or errors). Implemented.

Progress line format: ✔|▲|-|✖ <linter> done|skipped|failed <detail>.

Every issue line is printed: NO folding of repeated issues, NO per-rule summary, NO leading total (the totals are in the closing verdict). Within a file the location, severity and message columns are aligned.

.agents/skills/git-commit/SKILL.md                                 (9)
  22:0   low   Fenced code blocks should have a language specified   markdownlint/MD040
  32:0   low   Fenced code blocks should have a language specified   markdownlint/MD040
  ...

pkg/trunk/download/shim.go                                         (2)
  57:3   high  QF1012: Use fmt.Fprintf(...) instead of WriteString(fmt.Sprintf(...))   golangci-lint2/staticcheck
  59:2   high  QF1012: Use fmt.Fprintf(...) instead of WriteString(fmt.Sprintf(...))   golangci-lint2/staticcheck

FAILURES
  ✖ gitleaks   failed to run   rtunk logs show 3f9a2c
    download: https://example.com/gitleaks_darwin_arm64: unrecognized archive format

Checked 232 files with 6 linters in 14.2s
✖ 27 issues (5 high · 4 medium · 18 low) · 1 failure

Rules:

• File header = bold path plus issue count, no position.
• linter/rule in dim at the end of the line.
• Severity colored with a glyph (✖ high red, ▲ medium yellow, · low dim) while keeping the words high/medium/low (trunk compatibility and no-color mode).
• Failures in their own section, with the log uid (link to rtunk logs show).
• Summary at the bottom.
• Files in alphabetical order, issues sorted by line.
• Deferred: clickable OSC 8 links, sort by severity.

Implemented by the plain renderer: severity maps error to high, warning to medium, anything else to low; issue lines are line:col high|medium|low message linter/rule. Skipped linters get one Skipped N linters: ... line before the footer. The footer is Checked N files with M linters in Ts, followed by a verdict: ✔ no issues, or ✖ N issues (a high · b medium · c low) · F failures. fmt reports REFORMATTED N files (WOULD REFORMAT with --check) plus a verdict.

Color (implemented, human only) is emitted only when stdout is a terminal (ModeCharDevice) and NO_COLOR is empty; the severity glyphs are added only then. Output outside a terminal is byte-identical to the uncolored report, and stderr progress lines are never colored.

Neither bubbletea nor a progress-bar library. A hand-written renderer: a single goroutine redrawing the live area at about 10 Hz with ANSI sequences (cursor up, erase line), one Write per redraw. The frame is a pure function of state, size, clock and glyph set (live.go); screen.go only moves the cursor. The terminal size comes from a stdlib syscall ioctl on stderr (termsize_unix.go; 80x24 elsewhere) instead of golang.org/x/term, which is not a dependency. Lines are truncated to the width minus one column (no auto-wrap). The cursor is never hidden, so Ctrl+C only erases the area and re-raises SIGINT for the default termination. The current go.mod dependencies are only kong, yaml.v3 and testify.

Implemented (internal/cli/list.go). Replaces trunk's flat 130-line listing (most of it empty) and the former * name description format (gone, breaking) with a grouped output:

Enabled
  ✔ [email protected]            153 go files
  ✔ [email protected]      47 markdown files
Available for this repo (not enabled)
  ◯ golangci-lint           153 go files
  ◯ gitleaks                230 files
(97 other linters — rtunk linters list --all)

Enable one with: rtunk linters enable <id>

• Groups. Enabled (✔, id@version with the pinned version, shown even with 0 matching files), then Available for this repo (not enabled) (◯, linters matching at least one repository file, or suggested by suggest_if). Groups are separated by a blank line. With --all, a third group Other (linters matching no file, and linters matching files that suggest_if does not suggest) replaces the parenthetical, which otherwise reads (N other linters — rtunk linters list --all) (linter for N = 1).
• Counts. From every file of the repository (git ls-files -co --exclude-standard in git, a walk skipping .git otherwise), matched with the linter's files: criteria. The label is N <type> files for a linter with a single non-ALL file type (2 go files, 1 markdown file), else N files. Names are padded to align.
• actions list has two groups only, Enabled and Available (not enabled) (actions have no matching files and no --all), and the footer Enable one with: rtunk actions enable <id>.
• --format json prints {"enabled": [...], "available": [...], "other": [...]}, entries being {id, version, files, description}; other is only filled with --all, arrays are never null, and files is omitted for actions.
• Override notes. A linter enabled or re-pinned by a local override file gets (from <file>) after its count, one kept off by lint.disabled (disabled by <file>); JSON items gain enabled_by / disabled_by. The picker rows carry the same notes.
• Color. Only on a terminal and without NO_COLOR: bold headers, green enabled marks, dimmed linters matching 0 files. Plain text when piped. No ASCII fallback.
• Interactive picker (linters enable / actions enable without id). Full-screen on the alternate screen (terminal restored on exit), same groups as list with blank lines between. Scrolls to the terminal height and follows resizes; ↓ N more counts items below the viewport. Type to filter on id (backspace edits; filter: line shows (visible/total)), up/down move, space toggles, enter confirms, esc or ctrl-c cancels (q is typed into the filter). 0-file linters are dimmed.

1. Event stream + plain renderer (needed for CI and tests). Implemented.
2. --format human|sarif|json and color. Implemented.
3. TTY live view. Implemented.
4. Filtered linters list / actions list. Implemented.

All four items are implemented. Later: color themes (including a distinct install-row color), detailed byte-progress style, a "waiting for runtime" install state.

• CLI Design
• Run Flows
• Command Reference