Welcome to mantis

mantis lets you browse, read, and review a codebase right in your terminal — instantly. Point it at a folder and start moving through your files with the arrow keys (or your mouse), with syntax highlighting, rendered markdown, fuzzy search, and git diff/blame/history always one keystroke away.

💡 New here? You only need two things to get started: the Installation page, then the Quick Start. Everything else is optional.

What makes it nice

• ⚡ Lightweight & instant. One small binary, no runtime dependencies, and nothing to configure before your first run. It opens in milliseconds, even over SSH.
• 🌳 A real tree view. Navigate folders with the keyboard or mouse, respecting your .gitignore.
• 🔍 Fuzzy & full-text search. Jump to any file by name (Ctrl+T), or search across the contents of every file (Ctrl+F) — fzf-style, as you type.
• 🎨 Readable files. Syntax highlighting for source code, rendered markdown, and JSON pretty-printing.
• 🔧 Git built in. Per-line blame, working-tree diffs, file history, and status-colored tree entries — no plugins required.
• ⌨️ Discoverable. Press ? for help or Ctrl+P for a searchable command palette. You don’t have to memorize anything.

Try it in five seconds

mantis          # open the current directory
mantis path/to/dir  # open a specific directory
mantis file.md      # open a single file directly

Press ? any time for in-app help, and Ctrl+c to quit.

Where to go next

Why mantis?

There are a lot of ways to look at code. So why mantis?

Because mantis is built for one job — moving through a codebase and reading it, with git context one keystroke away — and it does that job with zero setup. It is deliberately not a full editor, and that focus is what keeps it fast and simple.

💡 The short version: reach for mantis when you want to explore a repo, read a file, or check a diff without launching a heavyweight editor. When you actually need to change something, press e to jump into your $EDITOR.

At a glance

Compared to Vim / Neovim

Vim and Neovim are superb editors. But to get the everyday browsing experience mantis gives you out of the box — a file tree, a fuzzy finder, full-text search, git signs, inline blame, and side-by-side diffs — you have to assemble and maintain a stack of plugins:

• a tree plugin (nvim-tree, neo-tree),
• a fuzzy finder (telescope, fzf.vim),
• git integration (vim-fugitive, gitsigns),

…plus a plugin manager and the config glue to hold it together. Curated configs like LazyVim make this easier, but they are large, opinionated systems with their own learning curve and maintenance.

And then there’s the modal learning curve itself: modes, motions, registers, and muscle memory that take real time to build.

mantis skips all of that. There’s no init.lua, no plugin manager, and no modes — just arrow keys (or hjkl if you prefer) and your mouse. Everything listed above already works the moment you run it.

🧭 Love Vim? Keep it. mantis is the browser you open first; e hands the file straight to your editor when it’s time to write.

Compared to VS Code

VS Code is a great IDE. But it’s an Electron application — it bundles a whole web browser, so it’s slow to launch and memory-hungry just to glance at a file or review a diff. On a remote machine over SSH, that gets even more painful.

mantis is a tiny native binary. It opens instantly, sips memory, and runs happily inside any terminal — local or remote. When you only need to read code or review a change, you don’t need to boot an IDE for it.

When mantis is the right tool

• ✅ Exploring an unfamiliar repository
• ✅ Reading source, docs, or markdown
• ✅ Reviewing a diff or checking who changed a line (blame)
• ✅ Working on a remote server over SSH
• ✅ Anytime you want something that opens now

For heavy, sustained editing — refactors, LSP, debugging — use your editor. mantis gets you there fast with e, and is waiting when you come back.

Installation

One-liner install (recommended)

Linux / macOS

The fastest way to get mantis — no Rust toolchain required — is the install script. It detects your OS/arch, downloads the matching prebuilt binary, verifies its SHA-256 checksum, and installs it onto your PATH:

curl -fsSL https://raw.githubusercontent.com/ansromanov/mantis/main/install.sh | sh

You can tweak the install with environment variables:

# install a specific release instead of the latest
MANTIS_VERSION=v0.2.0 curl -fsSL https://raw.githubusercontent.com/ansromanov/mantis/main/install.sh | sh

# install into a directory of your choice
MANTIS_INSTALL_DIR="$HOME/bin" curl -fsSL https://raw.githubusercontent.com/ansromanov/mantis/main/install.sh | sh

Prefer to read before piping to a shell? Download install.sh, inspect it, then run sh install.sh.

Windows (PowerShell)

Run this in a PowerShell window — curl is not needed, Invoke-WebRequest (irm) is built into PowerShell:

irm https://raw.githubusercontent.com/ansromanov/mantis/main/install.ps1 | iex

From cmd.exe:

powershell -ExecutionPolicy Bypass -c "irm https://raw.githubusercontent.com/ansromanov/mantis/main/install.ps1 | iex"

The script downloads mantis.exe, verifies its SHA-256 checksum, installs it to %CARGO_HOME%\bin (if Rust is present) or %LOCALAPPDATA%\Programs\mantis, and adds the directory to your user PATH. It also generates PowerShell tab completions (install to %CARGO_HOME%\completions\mantis.ps1).

You can override the install location:

$env:MANTIS_VERSION    = 'v0.2.0'          # install a specific version
$env:MANTIS_INSTALL_DIR = "$HOME\bin"       # install to a custom directory
irm https://raw.githubusercontent.com/ansromanov/mantis/main/install.ps1 | iex

Via cargo install

If you have the Rust toolchain installed, the simplest way to install mantis is:

cargo install mantis

This compiles and places the mantis binary in ~/.cargo/bin (which should already be on your PATH after a standard rustup install).

To install directly from the git repository without a crates.io release:

cargo install --git https://github.com/ansromanov/mantis

From source (Rust toolchain required)

git clone https://github.com/ansromanov/mantis.git
cd mantis
cargo build --release
# binary is at target/release/mantis

Or, if you have just:

just install   # builds --release and copies mantis to ~/.cargo/bin

Prerequisites

• Rust (stable toolchain)
• A terminal that supports 24-bit color

Prebuilt binaries

If you’d rather not use the install script, prebuilt binaries are attached to every release:

Download the appropriate binary for your platform from the latest release, make it executable (chmod +x on Linux/macOS), and place it somewhere on your PATH (e.g. /usr/local/bin or ~/.cargo/bin).

Each release also ships a SHA256SUMS file so you can verify your download:

sha256sum --check --ignore-missing SHA256SUMS

Via package managers

Homebrew (macOS / Linux)

The formula lives in this repository, so tap it by URL, then install:

brew tap ansromanov/mantis https://github.com/ansromanov/mantis
brew install mantis

The formula installs the prebuilt binary for your platform (Apple Silicon, Intel, Linux x86_64, and Linux arm64) — no Rust toolchain required. It is bumped automatically on every release, so brew upgrade mantis always tracks the latest version.

The explicit URL is needed because the repository is named mantis, not homebrew-mantis; Homebrew’s short brew tap user/repo form only resolves the homebrew--prefixed name.

The formula installs bash, zsh, and fish completions plus the man page automatically — no extra steps needed.

Manual: completions and man page

After installing mantis from any method, you can generate completions and the man page at any time:

# Shell completions
mantis --completions bash > /usr/local/share/bash-completion/completions/mantis
mantis --completions zsh  > /usr/local/share/zsh/site-functions/_mantis
mantis --completions fish > /usr/local/share/fish/vendor_completions.d/mantis.fish
mantis --completions powershell > ~/.config/powershell/completions/mantis.ps1

# Man page
mantis --print-man-page > /usr/local/share/man/man1/mantis.1

The one-liner install script (install.sh) does this automatically when it can write to the appropriate share/ directories.

Other package managers

Coming soon — Scoop, and more are on the roadmap.

Quick Start

This page walks you through your first few minutes with mantis. No prior terminal expertise required — if you can run one command and press arrow keys, you’re set.

📦 Don’t have it yet? See Installation first, then come back.

1. Open something

Open the folder you’re currently in:

mantis

Or point it at a folder or a single file:

mantis ~/projects/my-app   # a directory
mantis README.md           # one file

You’ll see two panels: the file tree on the left, and the content of the selected file on the right.

2. Move around

You don’t need to learn anything special — use the arrow keys, or your mouse.

🖱️ Prefer the mouse? Click a row to select it, click a folder to fold/unfold, and use the scroll wheel in whichever panel your cursor is over.

3. Find a file fast

Two kinds of search, both fzf-style (just start typing to filter):

• Press Ctrl+T to search by file name.
• Press Ctrl+F to search inside files (full-text).

Use ↑ / ↓ to pick a result and Enter to open it. Press Esc to close search. Inside the popup, Tab switches between name and content search.

4. Peek at git

If you’re inside a git repository, you get this for free:

• Tree entries are colored by git status (new, modified, deleted).
• Press Ctrl+b to toggle blame — see who last touched each line.
• Press H (while the tree is focused) for the history of the current file, then pick a revision to view its diff.
• Press Ctrl+D for git mode: show only changed files, with their diffs.

There’s a whole page on this — see Git Features.

5. When you can’t remember a key

You never have to memorize the keymap:

• Press F1 (or ?) for in-app help with all the keybindings.
• Press Ctrl+P for the command palette — type what you want to do (e.g. “blame”, “theme”), and it shows the action and its shortcut.

6. Make it yours (optional)

• Press t (while the tree is focused) to switch themes live (monokai, solarized, catppuccin, and more).
• Want different colors or keybindings permanently? That all lives in a small mantis.toml file — see Configuration.

That’s the whole core experience. From here:

• Usage & Keybindings — the complete key reference
• Git Features — blame, diffs, and history in depth
• Configuration — themes and custom keys

Release Digests

v0.17: faster navigation, richer review, and broader language support

Version 0.17 makes the command palette the quickest route into a repository, adds a commit-oriented review flow, and expands the file types that mantis can read well out of the box. Everything below is available with the default configuration.

One palette for commands, files, content, and lines

Press Ctrl+P to open the command palette. Its first character chooses what you are looking for:

The palette remembers which commands you use. With an empty query, your most recent command and the most useful recent commands appear first; that ranking gradually gives more weight to what you use now. Set palette_pin_recent = false or palette_frequent_count = 0 in mantis.toml if you prefer an unpinned palette.

Plugins can also add actions to this same palette. Plugin authors can use the register_commands protocol action; see Plugin Development for the message format and lifecycle rules.

Review a change since any revision

Use Compare against a revision from Ctrl+P to review the current working tree against a branch, tag, commit hash, or revspec such as HEAD~3. Select a suggestion or type the revision and press Enter. The tree then contains only files changed since that revision, and selecting a file opens its diff. The status bar displays the selected comparison base.

There is also a repository-wide commit browser. Press L while the tree has focus, or run Browse repository commits from the palette. Type to filter by hash, author, or subject, select a commit, and press Enter to begin a compare review from that commit. Press Esc or Ctrl+D to leave compare mode.

See Git Features for the full git workflow.

Fold structured data and shell scripts

The bundled JSON, YAML, and shell language providers are enabled by default. Open a .json, .yaml/.yml, .sh, .bash, or .zsh file, focus the content pane, place the active line on a foldable section, and press Space to collapse or expand it.

• JSON folds multi-line objects and arrays. Use the existing JSON pretty-print command first when viewing minified JSON.
• YAML folds indentation-based sections.
• Shell folding recognizes function and compound blocks while ignoring braces in comments, quoted strings, and heredocs.

The providers can be disabled individually under [plugins] in mantis.toml; Plugins lists their names.

More files highlighted without setup

TOML, TypeScript/TSX, and Dockerfile syntax packs now ship enabled. Open a .toml, .ts, .tsx, .mts, .cts, or .jsx file, or a Dockerfile or Containerfile, and mantis selects the matching highlighting automatically. This includes common configuration files such as Cargo.toml, pyproject.toml, and mantis.toml.

For every bundled provider and syntax pack, including how to opt out, see Plugins.

v0.16: review tools and language-aware reading

Version 0.16 focused on making code review more legible while adding folding for the languages most commonly encountered in a repository.

Compare a revision and inspect blame in context

To review all changes since a branch, tag, hash, or revspec, run Compare against a revision from Ctrl+P, choose or type the revision, and press Enter. The changed-file tree and each file’s diff stay scoped to that base; press Ctrl+D to return to normal browsing.

With a tracked file open, press Ctrl+b to open the full-file blame pane. It follows the content cursor and shows the hash, author, date, and subject for each line. Press B in the content pane when you only need the active line’s blame summary. The Git Features guide covers both workflows.

Fold Rust, Python, and Go

The bundled Rust, Python, and Go providers add fold regions for .rs, .py, and .go files. Focus the content pane, move to a foldable declaration or block, and press Space to collapse or reopen it. Folding stays available alongside the ordinary syntax highlighting and can be disabled per provider in mantis.toml if needed.

Faster discovery and safer diagnostics

The command palette now presents categories, descriptions, match highlights, and context when an action cannot apply. Press Ctrl+P, type an action name, and use the displayed shortcut or Enter to run it.

Use Report a bug (save diagnostics locally) from the palette to create a local, reviewable report, or Toggle telemetry to opt into the local-only usage log. Neither feature uploads data. See Telemetry & Bug Reports for the saved locations and contents.

v0.15: navigation and compatibility polish

Version 0.15 was a focused stability release rather than a new interaction mode. Large trees avoid an unnecessary deep scan when nothing is expanded, so starting a repository and moving through its top level is more responsive.

Visual selection now remains visible on the active line, making it easier to keep your place while copying or inspecting a range. Existing configuration files using older git_mode and renamed keymap fields continue to load without spurious warnings; consult Configuration when you are ready to migrate to the current names.

v0.14: pager mode, powerful search, and familiar keys

Version 0.14 made mantis more useful in command pipelines and easier to learn for users coming from common editors.

Use mantis as a terminal pager

Pipe a diff, log, or any text into mantis to browse it interactively:

git diff | mantis
git log -p | mantis
kubectl logs pod | mantis

Diff-shaped input opens in a navigable side-by-side view. For other input, use --language when you want to force syntax highlighting. See Pager mode for behavior and platform details.

Tune a search without changing its query

In content search or the in-file search bar, press Ctrl+A for case-sensitive matching, Ctrl+W for whole-word matching, and Ctrl+R for a regular expression. The active [Aa], [\b], and [.*] indicators show which constraints are in effect. Press the same shortcut again to turn it off.

Learn the editor-style defaults

The shipped keymap uses familiar editor-style bindings: Ctrl+P opens the palette, Ctrl+T finds files, Ctrl+F searches contents, Ctrl+G goes to a line, and Ctrl+D opens the changed-file review view. Press ? or F1 for the structured help overlay, then use its tabs to browse key groups. All of these bindings remain remappable in mantis.toml.

Plugin authors should update manifests to mantis_protocol = "3" when using the protocol-3 request/response, key-consumption, or provider-priority features; Plugin Development has the compatibility details.

v0.13: a more dependable everyday viewer

Version 0.13 improved the tools used to orient yourself in a repository and made plugin failures easier to diagnose.

Preview themes and use a scrollable help overlay

Press t in the tree to open the theme picker. Moving through its entries previews each theme immediately; press Enter to keep it or Esc to return to the original theme. The Themes page explains persistent theme configuration.

Press ? or F1 whenever you need a reminder. Help is scrollable, and its Git section collects the status, diff, blame, and history shortcuts in one place.

Rely on safer sessions and clearer plugin failures

Each workspace keeps independent session state, so multiple mantis instances no longer overwrite one another’s restored view. Bundled plugins are embedded with the application rather than relying on a local build at startup, and old retired shell plugins are removed during upgrade.

If a process plugin exits unexpectedly, mantis keeps its recent stderr and points to a local plugin log. Open the plugin picker with p in the tree to check its status; Plugins explains how to enable, disable, and configure plugins.

Usage & Keybindings

Basic usage

mantis                    # view the current directory
mantis path/to/dir        # view a specific directory
mantis file.md            # open a single file directly
mantis --completions bash # generate shell completions (bash, zsh, fish, powershell)
mantis --print-man-page   # print the man page
mantis --language rust < file # force syntax highlighting for piped stdin
mantis --update           # self-update to the latest release
mantis --help             # print help (or -h)
mantis --version          # print version (or -V)

Press ? or F1 for in-app help, and q to quit.

Pager mode

When no <path> is given and stdin is piped rather than a terminal, mantis reads stdin instead of walking a directory:

git diff | mantis          # navigable side-by-side diff
kubectl logs pod | mantis  # highlighted, searchable log output
curl -s https://example.com/file.py | mantis --language python

Diff-shaped input (a diff --git/diff --cc header, an @@ - hunk header, or a --- /+++ file-marker pair) renders through the same side-by-side diff view as git mode, starting in side-by-side layout regardless of the [git.diff] side_by_side setting. Anything else is syntax-highlighted: pass --language <name> (e.g. --language rust) to force it, otherwise mantis sniffs the first line the way syntect detects shebangs and mode lines.

The tree pane collapses (there is no path driving the view) and focus starts in the content pane, but the tree is still there — drag the splitter or press Tab to browse the working directory alongside the piped content. Keyboard input keeps working normally even though stdin is consumed by the piped data: mantis reads keys from the controlling terminal (Unix: /dev/tty, Windows: CONIN$) instead, the same trick less uses. Input is read to EOF before the UI starts, so very large piped input delays the first frame rather than streaming incrementally.

Terminal compatibility

The main panels require at least 80 columns to remain usable. At smaller sizes, mantis shows a resize message instead of rendering clipped tree and content panes.

Keyboard enhancement

Every default binding uses plain Ctrl+letter, a bare/Shift letter, or a named key — combinations that work identically on every terminal and OS. Ctrl+Shift combinations are deliberately not used: kitty reserves ctrl+shift for its own shortcuts (kitty_mod), Windows Terminal binds Ctrl+Shift+P/Ctrl+Shift+F itself, and legacy terminals (macOS Terminal.app, plain xterm, many SSH setups) can’t even distinguish them from plain Ctrl. Modifier bindings are matched case-insensitively, so CapsLock or a stray Shift never breaks a shortcut.

On terminals with the kitty keyboard protocol (CSI-u), mantis additionally matches bindings by physical key position, so shortcuts work on non-Latin keyboard layouts.

¹ iTerm2 supports CSI-u (disambiguation + event types) but may not report alternate keys for all keyboard layouts.

² xterm supports mouse events but the generic mouse protocol (SGR 1006) lacks drag and release tracking. Enable xterm-mouse in tmux or `XTerm*decTerminalID:

280` for full SGR mouse.

On terminals without keyboard enhancement, mantis shows a one-time notice and notes the limitation in the in-app help (? → Getting started).

The best terminals for full mantis keyboard support are kitty, WezTerm, Ghostty, Alacritty 0.15+, and Windows Terminal.

Session persistence

mantis automatically remembers your workspace state across restarts: expanded directories, the last open file, scroll position, and git mode. State is cached outside the project tree (~/.local/state/mantis/ or %APPDATA%\mantis\) so it survives re-clones and never writes dotfiles into the repository. Each workspace root gets its own file under the sessions/ subdirectory. To reset the session for a directory, quit and delete its file from the sessions/ subdirectory in the state directory.

💡 Can’t remember a key? Press ? or F1 for the help overlay, or Ctrl+P to open the command palette and search for an action by name — it shows you the shortcut too. New to mantis? Start with the Quick Start.

Bindings are editor-style (VS Code / Sublime conventions) and fully remappable — see Keybindings for the complete list, the macOS (Cmd) variants, and the tree:/content: scoping syntax. The tables below cover the shipped defaults; single letters (q, p, t, …) only work while the tree panel is focused — the content pane’s letter keyspace is kept free, apart from the vim motions below, for future editing features. Any action not listed with a content-pane key is still reachable from the command palette (Ctrl+P).

Global

These work no matter which panel is focused.

Tree panel

Bookmarks are stored per workspace and restored across sessions. Use the bookmarks picker to fuzzy-filter the pinned files, then press Enter to open one. The default bindings are tree-scoped; you can change them in mantis.toml.

Content panel

The content pane has a line cursor (visible as a highlighted full-width row). Use Up/Down to move it, then press B to show a single-line blame bar for the highlighted line.

When full-file blame is toggled on (Ctrl+b), the tree panel is replaced by a dedicated blame pane listing every line’s commit hash, author, date, and subject, kept in sync with the content cursor. Clicking a row in the blame pane jumps the cursor there and opens the single-line blame bar.

Word wrap, line numbers, JSON pretty-print, CSV/TSV table view, side-by-side diff, and the staged/unstaged diff cycle have no default content-pane key — use the command palette (Ctrl+P) or bind one yourself in mantis.toml.

CSV and TSV table view

.csv and .tsv files are parsed (supporting RFC 4180 quotes and escaped characters) and rendered as aligned tables with Unicode box-drawing borders and headers. Like JSON pretty-printing, table formatting respects prettify_size_limit (files exceeding the limit show as raw text). You can toggle between table view and raw text using the command palette (Ctrl+P → “Toggle CSV/TSV table view”) or by binding toggle_table_view in mantis.toml. Wide tables can be scrolled horizontally with Left/Right.

Rendered plugin content and line numbers

mantis has no built-in markdown renderer; install and enable the markdown plugin (p in-app, or [plugins.markdown] in mantis.toml) for rendered Markdown. When a plugin renders a file’s content, line numbers are hidden in the gutter. This is by design: rendered content collapses blank lines, strips code fences, and restructures formatting, so rendered-line numbers don’t correspond to source-file line numbers.

When the markdown plugin is active and rendering a file, you can press M (or run “Toggle markdown render (markdown plugin)” from the command palette) to toggle between the raw file content and the rendered view.

Git features

Tree colors

Files and folders in the tree are colored by their git status:

A directory takes the color of the most significant change inside it.

Status bar

The status bar shows a git summary when inside a repository:

[branch  +ahead -behind  N changed]

Git mode and diff navigation

Side-by-side diff and the staged/unstaged diff cycle have no default key — use the command palette (Ctrl+P) or bind one in mantis.toml.

Search popup

Three search entry points cover different needs:

• Ctrl+T — global fuzzy file-name picker. Opens the same file-name search from either panel, regardless of focus. Use this when you want to jump to any file in the project by name.
• / — context-sensitive: in the tree panel it filters file names inline; in the content panel (with a file open) it opens the in-file search bar; otherwise it falls back to the file-name picker.
• Ctrl+F (or f in the tree panel) — fuzzy content search across all files (or changed files in git mode).

Open any search popup and just start typing to filter. In git mode (Ctrl+D), searches are automatically scoped to only the changed files — the popup title shows “(changed files)” to make this visible.

The toggles apply to content search (f) and the in-file search bar (/); the active options are shown as highlighted [Aa] [\b] [.*] indicators.

Command palette

Press Ctrl+P to open a searchable list of every action, each shown next to its current keybinding. Type to fuzzy-filter (e.g. “blame”, “theme”, “json”), navigate with Up/Down, and press Enter to run the highlighted command. It’s the fastest way to discover what mantis can do without memorizing keys.

Commands that don’t apply to the current state (e.g. “Toggle JSON pretty-print” with no JSON file open, or “Toggle blame” outside a git repo) are shown dimmed with the reason in place of their description. Selecting one anyway sets a status-bar message explaining why it didn’t run, instead of silently doing nothing.

Prefix routing

The palette is also a unified quick-open: type one of these characters as the first character of the query to switch what it searches:

In the file/content modes, Tab toggles between the two (just like the standalone search overlay), and Enter opens the selected result. Backspace on an empty routed query — or Esc — returns to the commands list; a second Esc closes the palette.

Reporting a bug

Run “Report a bug (save diagnostics locally)” from the command palette to open an interactive modal where you can write a description and preview the collected diagnostics. Submitting the modal (Ctrl+S or Ctrl+Enter) saves the report locally, attempts to open the GitHub issue creator in your browser prefilled with the report, and falls back to copying the report to your clipboard if needed. See Telemetry & Bug Reports for exactly what the report contains.

Git mode history

H (while the tree is focused) opens the file’s git history in both normal and git mode. The diff of a selected commit stays on screen and won’t be replaced by live file-watcher updates. Press Esc or reload (Ctrl+r/F5) to return to the current file (or the working-tree diff in git mode).

Open in your editor

Press Ctrl+e (or e while the tree is focused) with a file open to launch it in your editor. mantis uses $VISUAL, then $EDITOR, preferring nano over vim when neither is set. The TUI suspends while the editor runs and resumes when you exit; the file is reloaded afterwards so you see your changes.

💡 $EDITOR can include arguments — e.g. export EDITOR="code --wait" opens the file in VS Code and waits for you to close the tab before returning.

To override the editor without setting environment variables, add to mantis.toml:

[general]
editor = "code --wait"

When $VISUAL and $EDITOR are both unset and no config override exists, mantis probes for nano, then vim, and shows a status-bar hint on return so you know how to change it.

Status bar

The status bar at the bottom of the screen shows context-sensitive information about the open file:

• Ln N — the active (highlighted) line number, 1-indexed.
• [Language] — the detected syntax name from syntect (e.g. [Rust], [Python], [TOML]). Hidden when the file type is not recognised or when viewing a diff.
• Scroll percentage — how far through the file the content pane is scrolled.
• Encoding and line endings — shown when I (file info) is toggled on.

Code folding

Press Space to fold or unfold the block at the cursor. A fold gutter appears in the content pane when foldable regions are detected, and the status bar shows fold stats. Fold regions come from two sources: a built-in YAML indentation detector, and language plugins that supply per-file-type regions over the plugin protocol. Plugin regions override the built-in output for their file extension.

Note that folding for a mainstream language like Rust (.rs) or Go (.go) can be provided by a language provider plugin — the bundled rust and go plugins register this way. You must explicitly enable such plugins in mantis.toml (or via the plugin manager popup) for folding to work on those files.

Objects and arrays in .json files can be folded the same way, via the bundled json plugin (also opt-in). It folds against the pretty-printed view below, so regions line up whether or not the file was originally minified.

JSON pretty-printing

Viewing a JSON file? Use the command palette (Ctrl+P → “Toggle JSON pretty-print”) to reformat it with indentation for easier reading, and again to return to the raw text. Handy for minified .json. There’s no default key for this — bind toggle_pretty_json in mantis.toml if you want one. JSON pretty-printing itself is always core, not a plugin concern — the json plugin only adds fold regions on top of it.

JSON Lines

Files ending in .jsonl or .ndjson are shown as one compact object per line. Press Space on an object to expand it into formatted JSON in place; press Space again to collapse it. Invalid or partially-written lines remain visible as plain text, which keeps mixed structured logs readable.

Secret masking

Credential-shaped files such as .env, .pem, credentials, and kubeconfig are masked by default. Values use a fixed-width placeholder so their length is not exposed. Use the command palette action Toggle secret reveal to reveal or mask the current file for the session; the value is never persisted.

Set content.mask_secrets = false to disable this protection.

Use the command palette action Open JSON query bar to filter or project JSON and JSONL. The supported subset includes .a.b[0], .items[], {name, image} and select(.level == "error"). Invalid queries keep the last valid result; press Esc to restore the unfiltered view.

Log follow mode

When viewing log files (detected via .log extension or level/timestamp sniffing), mantis automatically enables log mode.

• Press F to toggle log follow mode.
• When follow mode is enabled and pinned (default), mantis auto-scrolls to the tail when new logs are appended to the file.
• Navigating upwards (e.g., Up/k, PageUp) will temporarily unpin follow mode to let you read earlier lines. Navigating to the bottom (e.g., G/End) will re-pin follow mode.
• Press & to open the filter bar. Typing a query will filter the visible log lines to only those containing the query.

Mouse

• Click a tree row to select it — opens a file, or folds/unfolds a directory.
• Double-click a directory to make it the new tree root.
• Click a pane to focus it.
• Scroll wheel scrolls whichever pane is under the cursor.
• Double-click a breadcrumb segment to navigate to that directory.
• In the search and history popups, single-click selects an entry and double-click activates it.
• Right-click a tree row or the content pane to open a context menu at the cursor. Tree menus offer open, open in editor / default app, reveal in file manager, copy absolute/relative path, expand/collapse (directory), and expand/collapse all. Content menus offer copy selection/line/file, word wrap and raw-markdown toggles, and reveal-in-tree. Navigate with the mouse or j/k/arrows, activate with Enter or a left-click, and dismiss with Esc or a click anywhere else.

Worktree switcher

When a repository has multiple linked worktrees, use the command palette and choose Open worktree switcher. The picker shows each worktree’s branch and changed-file count; type to filter, then press Enter to switch the tree to that worktree. The status bar shows the total worktree count when more than one is available.

Git Features

mantis has comprehensive git support built in. Inside any git repository you get status colors, blame, file history, and a dedicated diff-review mode out of the box.

All git data — repo info for the status bar, per-path status for tree coloring, blame annotations, and file diffs — is provided natively via the git CLI.

ℹ️ All git features need git on your PATH and the file to be tracked in a repository.

Git status colors

Whenever mantis can read git status, tree entries are tinted by their state — new, modified, deleted, or ignored — so you can see at a glance what’s changed without doing anything. Control this with git_status in your config (see Configuration).

The status bar also shows how far the current branch is from its upstream when a tracking branch exists, using the familiar ↑3 ↓1 summary.

Git blame

Press Ctrl+b with a file open to toggle full-file blame. The tree panel is replaced by a dedicated blame pane listing every line’s short commit hash, author, relative date, and subject. Navigate it with the usual tree keys (↑/↓, PageUp/PageDown, g/G) — they move the cursor through the file instead of the tree selection while the pane is open. Press Ctrl+b again (or Esc) to close it and return to the tree.

Press B with the content panel focused to toggle a single-line blame bar at the bottom of the tree panel, showing the commit hash, author, date, and subject for the current cursor line.

Blame is disabled while you’re viewing a diff (it only annotates real file content).

Visual-line blame

For inspecting a specific range rather than the whole file, press V with a file open to enter visual-line mode. The first visible line is selected; extend the selection a line at a time with j/k (or ↑/↓), jump to the top/bottom of the file with g/G, and page with PageUp/PageDown. The selected lines are highlighted with a distinct background.

Press b while in visual-line mode to open a blame panel scoped to the selection: each line in the range is listed with its short commit hash, author, relative date, and content. Press b again to dismiss the panel, and Esc to leave visual-line mode entirely. Like the inline gutter, this is unavailable while viewing a diff.

Git file history

With a file open in the content panel, press H to open an fzf-style list of the commits that touched it. Type to fuzzy-filter, navigate with ↑/↓, and press Enter (or double-click) to load the diff of that revision against your current working tree into the content panel — additions in green, deletions in red.

Repository commit log

Press L while the tree is focused, or use the command palette (Ctrl+P) to run Browse repository commits, to search the repository-wide commit log. The picker shows each commit’s short hash, date, author, and subject. Type to filter by hash, author, or subject; select a commit and press Enter to review all changes since it in compare mode. Press Esc to close the picker.

Git mode

Press Ctrl+D to switch the tree to show only files with uncommitted changes (modified, new, deleted, or renamed). Selecting a file shows its working-tree diff in the content panel instead of the file contents. The tree title displays a [git] badge while active — perfect for reviewing everything you’re about to commit.

Press F (while the tree is focused) inside git mode to toggle between the tree view (directories intact) and a flat, depth-0 list of every changed file with relative paths. Press F again to return to the tree view (a no-op outside git mode).

When the working tree is clean (no uncommitted changes), the tree panel shows a “Working tree clean” placeholder instead of an empty list, so you can tell at a glance that there is simply nothing to review. If the current directory is not a git repository, the placeholder says “Not a git repository” instead. Press Ctrl+D to exit git mode in either case.

All directories containing changes are auto-expanded when entering git mode. Diffs refresh on the 30-second auto-reload tick and on manual r.

git_status controls whether tree entries are coloured by git status at startup:

git_status = true        # colour tree entries by git status (default: true)
git_show_deleted = false # show ghost nodes for deleted tracked files (default: false)

Compare mode

To review changes against something other than the working tree’s usual baseline, open the command palette and run Compare against a revision. A picker overlay opens with three tabs — Commits (default), Tags, and Branches — switchable with the Left/Right arrow keys. Each tab shows only items of that category, plus HEAD shortcuts (HEAD, HEAD~1, HEAD~2) that appear in all tabs. Start typing to fuzzy-filter the list, or enter any revision (a commit hash, tag, branch name, or something like HEAD~3) freely — press Enter to select the highlighted item, or when no items match, the typed text is used as a raw revspec. mantis switches into git mode: the tree shows only files changed between that revision and your working tree, and opening a file shows git diff <rev> -- <file> instead of the usual working-tree diff. The status bar shows a [compare: <rev>] badge while active.

Press Ctrl+D to leave compare mode and return to full browsing.

Using mantis as git’s pager

mantis can read a diff from stdin (see Pager mode), so it works as a drop-in side-by-side pager for git diff, git show, and git log -p:

git diff | mantis                      # one-off
GIT_PAGER=mantis git log -p            # one-off, any pager-using command
git config --global core.pager mantis  # every git command, permanently

Configuration

💡 Configuration is optional. mantis works great with no config at all. Come here when you want to change colors, remap a key, or set a default behavior.

mantis reads a mantis.toml file. It first looks for one in the directory being viewed (and its ancestors), then falls back to the global config at $XDG_CONFIG_HOME/mantis/mantis.toml (or ~/.config/mantis/mantis.toml). A project-local file overrides the global one, so a repository can ship its own defaults.

Defaults vs. your config

Configuration has two layers:

• Built-in defaults ship inside mantis and supply every value. You don’t have to set anything.
• Your mantis.toml overrides only the keys you set; everything else falls through to the defaults.

On first run mantis creates a tiny stub mantis.toml (just a header comment) next to a read-only mantis.default.toml in your config directory. mantis.default.toml lists every option with comments and is refreshed on every upgrade, so it always documents the current set of options. Your own mantis.toml is never modified by an upgrade — edit it freely.

When you change a setting at runtime (e.g. switching theme), mantis saves only the keys that differ from the defaults back to your mantis.toml, keeping it small. To see all available options, open mantis.default.toml; to change one, copy that line into your mantis.toml.

Live reload

mantis watches your mantis.toml while running. Saving the file re-reads it and hot-reloads most settings (theme, keybindings, tree/content display options) immediately — the status bar shows mantis.toml reloaded, or the specific problem if the file failed to parse or contains unknown keys. Changes to [plugins] entries can’t be applied to an already-running plugin process, so those show mantis.toml changed — restart to apply instead and take effect on the next launch.

Options

Options are grouped into tables by area. A few general keys sit at the top level (they must appear before the first [table] header); everything else lives under [tree], [content], [search], or [git].

Migrated from flat keys? Older configs used flat top-level keys (show_hidden, tree_width, git_status, …). Those still load — they are folded into the grouped tables automatically — but the grouped form below is canonical. mantis.default.toml is refreshed to the grouped layout on upgrade.

# top-level (must precede any [table])
recent_files_count = 10      # number of recently opened files to remember
palette_pin_recent = true    # pin the last-used command atop the Ctrl+P palette
palette_frequent_count = 3   # most-used commands pinned below it; 0 disables

[general]
editor = "code --wait"       # external editor command; overrides $VISUAL / $EDITOR
                             #   When unset, falls back to $VISUAL, then $EDITOR,
                             #   then probes for nano before falling back to vim

[tree]
show_hidden = false          # show dotfiles / hidden entries
width = 20                   # tree panel width as a percentage (5-95) of terminal width
independent_scroll = false   # PageUp/Down scroll the viewport, not the selection
indent_guides = true         # draw indentation guide lines (│)
icons = false                # Nerd Font file-type icons (icon map from a plugin)

[content]
word_wrap = false            # wrap long lines in the content pane
line_numbers = true          # show the line-number gutter
scrollbar = true             # show a scrollbar
scroll_percentage = true     # show scroll-position percentage
watch = false                # auto-reload the open file when it changes on disk
follow_tail_auto = false     # auto-enable follow mode for log files
mask_secrets = true          # mask credential-shaped values by default
log_colorizing = true        # enable log level and timestamp colorizing
image_preview = true          # render images inline on Kitty-graphics terminals (Ghostty, Kitty, WezTerm)
show_file_info = true        # encoding + line-ending info in the status bar
prettify_size_limit = 10485760  # max bytes for JSON/YAML pretty-printing and CSV/TSV tables;
                                 #   larger files show as raw text (10 MiB default)

[search]
in_file_search = true        # enable in-file incremental search via `/`
context_lines = 0            # trailing context lines shown after each match
keep_query = false           # restore the last query when reopening search

[git]
status = true                # show git status colours/markers in the tree
show_untracked = true        # include untracked (??) files
show_ignored = false         # include ignored (!!) files
show_deleted = false         # ghost nodes for deleted tracked files
ignore_gitignore = false     # respect .gitignore when listing files

[git.diff]
mode = "all"                 # default diff source: "all" (vs HEAD) | "staged" | "unstaged"
side_by_side = false         # start the diff view in side-by-side layout

[telemetry]
enabled = false              # anonymous, local-only usage log — see Telemetry & Bug Reports

Keybindings

Every keybinding is remappable. Each action takes a list of key specs, so an action can have several shortcuts. A spec is a single character ("q", "?", "0") or a named key (Up, Down, Left, Right, Enter, Tab, Esc, Backspace, PageUp, PageDown, Home, End, Space, F1-F12), optionally prefixed with modifiers: "ctrl+c", "alt+.", "cmd+p" (cmd / super / command are all accepted, and map to the platform’s Cmd/Super key).

Panel scoping. A spec can also carry a tree: or content: prefix (e.g. "tree:q") to restrict it to that panel; unprefixed specs fire regardless of focus. The shipped defaults scope single-letter shortcuts to the tree panel so the content pane’s letter keyspace stays free for future editing features — only a small movement set (j k h l g G 0 n N) and modifier/F-key/named-key combos work as content-pane defaults. You can still bind a bare letter to a content-view action yourself; user overrides always take effect regardless of scope.

Keyboard layouts. Keybinding specs are written with Latin characters (e.g. "ctrl+p"). On terminals that support the kitty keyboard protocol (kitty, WezTerm, foot, ghostty, and others), mantis automatically uses the physical key position instead of the layout-translated character, so ctrl+p works correctly even on non-Latin layouts (Russian, Hebrew, etc.). Terminals without kitty protocol fall back to the logical character — bindings may not trigger as expected on non-Latin layouts in those terminals.

No Ctrl+Shift combinations. Ctrl+Shift shortcuts are unsupported: kitty reserves ctrl+shift as its own shortcut prefix (kitty_mod), Windows Terminal binds Ctrl+Shift+P/Ctrl+Shift+F for its palette and search, and legacy terminals can’t distinguish ctrl+shift+<letter> from ctrl+<letter> at all. Modifier+letter specs are therefore case-insensitive: "ctrl+P", "ctrl+shift+p", and "ctrl+p" all mean the same binding, which also fires with CapsLock on or Shift held. (Char case still encodes Shift for unmodified keys: "G" is Shift+G.)

Defaults are editor-style (VS Code / Sublime conventions), with vim motions kept as tree-panel secondaries:

[keys]
# global
quit = ["ctrl+c", "tree:q"]
help = ["F1", "?"]
command_palette = ["ctrl+p", "tree:P"]
reload = ["ctrl+r", "F5", "tree:r"]
switch_panel = ["Tab"]
toggle_hidden = ["tree:."]
theme_picker = ["tree:t"]
plugin_picker = ["tree:p"]
open_in_editor = ["ctrl+e", "tree:e"]
copy_path = ["tree:y"]
copy_relative_path = ["tree:Y"]
copy_line = ["content:y"]
copy_file = ["content:Y"]
toggle_watch = ["tree:W"]
recent_files = ["ctrl+o"]
toggle_bookmark = ["tree:B"]
bookmarks = ["tree:b"]
file_history = ["tree:H"]
goto_line = ["ctrl+g"]
git_mode_toggle = ["ctrl+d"]
git_mode_flat_toggle = ["tree:F"]

# search
search_files = ["/"]          # contextual: tree filter / in-file search
find_files = ["ctrl+t"]
search_content = ["ctrl+f", "tree:f"]

# navigation (shared by tree and content panes)
nav_up = ["Up", "k"]
nav_down = ["Down", "j"]

# tree pane
tree_expand = ["Enter", "Right", "l"]
tree_collapse = ["Left", "h"]
tree_up_dir = ["Backspace"]
tree_collapse_all = ["-"]
tree_expand_all = ["="]
tree_width_grow = ["]"]     # increase tree pane width
tree_width_shrink = ["["]   # decrease tree pane width
fold_toggle = ["Space"]

# content pane
content_left = ["Left"]
content_right = ["Right"]
content_top = ["ctrl+Home", "g", "tree:Home"]
content_bottom = ["ctrl+End", "G", "tree:End"]
content_page_up = ["PageUp"]
content_page_down = ["PageDown"]
content_reset_col = ["Home", "0"]
# toggle_wrap, toggle_line_numbers, toggle_pretty_json, toggle_table_view,
# toggle_diff_side_by_side, and toggle_diff_staged have no default binding —
# they're reachable from the command palette (Ctrl+P); bind them here
# if you'd like a dedicated key.
toggle_blame = ["ctrl+b"]
blame_line = ["content:B"]
# with the blame pane open, opens the file as it was at the commit on the
# active line (takes precedence over open_external's "o" while blame is open)
blame_open_commit = ["o"]

# diff view
diff_hunk_next = ["n"]
diff_hunk_prev = ["N"]
# in a revision diff, toggles between the diff and the full file content
# at that revision
toggle_file_revision = ["ctrl+u"]

macOS. Keymap::default() layers Cmd-primary bindings for the most frequent actions on top of the table above, keeping every ctrl+ binding as a fallback (Terminal.app/iTerm2 intercept most cmd+ shortcuts before mantis sees them; kitty/WezTerm/Ghostty forward them): find_files = ["cmd+t", "ctrl+t"], command_palette = ["cmd+p", "ctrl+p", "tree:P"], search_content = ["cmd+f", "ctrl+f", "tree:f"], reload = ["cmd+r", "ctrl+r", "F5", "tree:r"], recent_files = ["cmd+o", "ctrl+o"], content_top = ["cmd+Up", "ctrl+Home", "g", "tree:Home"], content_bottom = ["cmd+Down", "ctrl+End", "G", "tree:End"], content_reset_col = ["cmd+Left", "Home", "0"]. goto_line and git_mode_toggle stay on ctrl on every platform.

Command palette ranking

When you open the command palette with ctrl+p without typing a query, commands are ranked by frecency — a blend of how often and how recently each command has been used — rather than shown in a fixed order. Each use adds 1 to a command’s score, and scores decay by 10% per day since last use, so a command used heavily last month gradually yields to one used a few times this week. The most recently used command is pinned at the top; the highest-scoring commands follow it. Type any character to switch to the usual fuzzy search, which ignores this ordering.

Two options control the ranking:

# palette_pin_recent = true   # pin the last-used command at the top (default: true)
# palette_frequent_count = 3  # how many most-used commands to pin below it; 0 disables (default: 3)

Pinned entries are marked with a ★ prefix in the palette. Usage data is persisted across sessions in the state directory alongside session history.

Status bar

Segments in the status bar can be placed on the left or right side. Left segments render at column 0; right segments are right-anchored as a block with spaces between. When the terminal is too narrow, low-priority segments are dropped from both sides.

Default mode (both left and right unset): all segments are visible. The historical default places ["lnum", "type", "git", "version"] on the right, everything else on the left.

Explicit allowlist mode (either left or right set): only the listed segment ids render, on their configured side, in the order you specify. Unlisted segments are hidden. Set both to empty lists for an empty bar.

[statusbar]
# left = ["badges", "scroll", "lnum", "type", "fileinfo", "git", "errors", "folds", "message"]
# right = ["lnum", "type", "git", "version"]

Valid ids: badges scroll lnum type jsonpath fileinfo git errors folds message version. There is no keybinding-hint segment — the ?/F1 help overlay and the command palette are the discovery surfaces for bindings.

Theme

Themes live under a [theme] table and have their own page: see Themes for the presets, the live picker (t), and every role you can override.

Themes

Press t for an fzf-style picker to switch themes live, or set one in config. Built-in presets: default, monokai, solarized, catppuccin, synthwave84.

Configure under a [theme] table in your mantis.toml. name selects a preset as the base; each role then overrides it. A role takes a color name (cyan, lightyellow, reset) or a hex value (#aabbcc); syntax is a syntect theme name for file contents. Anything left unset keeps the preset’s value.

Presets ship their own background color; the default theme leaves it transparent (the terminal’s background). Set transparent_background = true to keep a preset’s colors but use your terminal’s background instead.

[theme]
name = "catppuccin"           # built-in preset to start from
auto_detect = true            # true = pick vscode-light or default preset based on terminal background

# Optional per-role overrides on top of the preset:
transparent_background = false  # true = use terminal's background instead of the preset's
background = "reset"         # panel backgrounds (reset = terminal default)
accent = "cyan"               # focused borders, primary highlights
accent_alt = "yellow"      # popup chrome, keys, prompts
dim = "darkgray"           # unfocused borders, gutters, hints, rules
text = "white"             # emphasized / default text
dir = "blue"               # directory entries in the tree
file = "reset"             # file entries in the tree
selection_bg = "darkgray"  # selected row / status bar background
selection_fg = "yellow"    # selected row foreground in popups
active_line_bg = "#3a5a5a" # active line cursor highlight (default: selection_bg)
heading1 = "lightcyan"     # markdown H1 / table headers
heading2 = "lightyellow"   # markdown H2
heading3 = "lightgreen"    # markdown H3
code = "lightyellow"       # inline code / code blocks
diff_add = "green"         # added lines in a diff
diff_del = "red"           # removed lines in a diff
git_clean = "green"        # statusbar git indicator: clean working tree
git_dirty = "yellow"       # statusbar git indicator: uncommitted changes
git_conflict = "red"       # statusbar git indicator: conflict / detached HEAD
git_progress = "#ff8700"   # statusbar git indicator: rebase / merge in progress
breadcrumb_fg = "cyan"     # breadcrumb path bar foreground (default: accent)
breadcrumb_bg = "reset"    # breadcrumb path bar background (default: background)
syntax = "base16-ocean.dark"

The background role controls panel backgrounds. When set to reset (the default), the terminal’s own background shows through. Each preset ships a preferred background color that you can override or disable with transparent_background. On top of presets, live theme switching instantly re-applies the current file with the new syntax highlighting theme.

Telemetry & Bug Reports

mantis ships two local-only diagnostic features: an opt-in usage telemetry log and an on-demand bug report command. Neither sends anything anywhere — both write files to your machine that you can inspect, delete, or choose to share when filing an issue.

Bug reports

Open the command palette (Ctrl+P) and run “Report a bug (save diagnostics locally)”. This opens a modal dialog where you can write a description of the bug and preview the diagnostic report below it.

When you submit the report (via Ctrl+S or Ctrl+Enter), mantis:

1. Saves the report as markdown under the state directory (~/.local/state/mantis/bug-reports/ on Linux/macOS, %APPDATA%\mantis\bug-reports\ on Windows).
2. Attempts to open your default browser to create a new GitHub issue pre-filled with your description and the diagnostic report.
3. If the report exceeds the URL length limit (~6KB) or if the browser fails to open, it copies the full report to your clipboard so you can paste it manually, updating the status bar with instructions.

The report contains, in full:

• app version and release date
• OS, architecture, OS version, and whether the session runs under WSL
• terminal identity: the TERM, TERM_PROGRAM, TERM_PROGRAM_VERSION, and COLORTERM environment variables, terminal size, and booleans for Windows Terminal / SSH sessions
• workspace shape: visible node/file/directory counts, tree depth, number of expanded directories, walk-error count, and whether it is a git repo
• open-file facts: extension, size, line count, encoding, line endings, detected syntax name, and JSON/diff/memory-mapped flags — never the name
• which config keys differ from defaults (key paths only, never values), the theme name, and the plugin count
• whether telemetry is enabled

It deliberately contains no personal data: no absolute paths, no file or directory names, no file content, no config values, no plugin names, and no environment variables beyond the terminal whitelist above.

Telemetry

Telemetry is disabled by default. Toggle it from the command palette (Ctrl+P → “Toggle telemetry”) — the status bar confirms the new state and the setting persists to mantis.toml:

[telemetry]
enabled = true

You can also set this key by hand instead of using the palette.

When enabled, whitelisted events are appended to a local JSONL log under <state dir>/telemetry/. Each session writes to a fresh, timestamped file events-<epoch>.jsonl (one file per session), rotated at 1 MiB within a session; at most five files (one active plus four rotated) are kept across sessions. When disabled — the default — no events are recorded and no files or threads are created. Data never leaves your machine; there is no upload endpoint.

Complete event schema

Events are a closed set; each line also carries ts_ms, milliseconds since the session started (no wall-clock timestamps).

Raw keystrokes, search queries, palette query text, file names, and paths are never recorded — the event types above cannot carry them. To stop collecting, set enabled = false (or remove the key); to erase history, delete the telemetry/ directory from the state dir.

Plugins

mantis supports two kinds of plugins: process plugins (subprocess-based) and syntax plugins (syntax definitions loaded into the highlighter).

Process plugins are standalone executables that hook into app events and issue actions back to the viewer. They run in separate processes; mantis talks to them over stdin/stdout using newline-delimited JSON, so a plugin can be any executable — a compiled binary, a Python script, or anything that can read stdin and write stdout.

Syntax plugins provide .sublime-syntax files that are loaded into the built-in syntect highlighter at startup. They add syntax highlighting for new file types without modifying the core binary.

Installing a plugin

Plugins live in the default plugin directory:

• Linux / macOS: ~/.config/mantis/plugins/ (or $XDG_CONFIG_HOME/mantis/plugins/ if that variable is set)
• Windows: %APPDATA%\mantis\plugins\

Process plugins

Drop the executable there and make it executable (chmod +x my-plugin.sh on Unix).

Syntax plugins

.sublime-syntax files placed in {plugin_dir}/syntaxes/ are auto-discovered at startup. They are installed automatically by mantis’s first-run setup.

Registering a plugin

Process plugins

Add a [plugins] section to your mantis.toml:

[plugins]
my-plugin = { path = "my-plugin.sh", enabled = true }

• path — path to the executable. Relative paths are resolved against the default plugin directory above. Absolute paths are used as-is.
• enabled — set to false to keep the entry without loading the plugin.

You can register as many plugins as you like:

[plugins]
git-stats   = { path = "git-stats.sh" }
file-logger = { path = "/usr/local/bin/mantis-file-logger" }
dev-tools   = { path = "dev-tools.py", enabled = false }

Syntax plugins

Syntax plugins can also be registered explicitly in mantis.toml with kind = "syntax":

[plugins]
terraform = { kind = "syntax", syntax_file = "syntaxes/terraform.sublime-syntax",
              extensions = ["tf", "tfvars"] }
toml = { kind = "syntax", syntax_file = "syntaxes/toml.sublime-syntax",
         extensions = ["toml"] }
typescript = { kind = "syntax", syntax_file = "syntaxes/typescript.sublime-syntax",
               extensions = ["ts", "tsx", "mts", "cts", "jsx"] }
dockerfile = { kind = "syntax", syntax_file = "syntaxes/dockerfile.sublime-syntax",
               extensions = ["dockerfile"] }
nginx = { kind = "syntax", syntax_file = "syntaxes/nginx.sublime-syntax" }
justfile = { kind = "syntax", syntax_file = "syntaxes/justfile.sublime-syntax" }

• kind — "syntax" for syntax-definition plugins (default: "process").
• syntax_file — path to the .sublime-syntax file. Relative paths are resolved against the plugin directory.
• extensions — file extensions this syntax should match (optional; the syntax definition itself also declares its own extensions).

Syntax plugins are not spawned as subprocesses. Their syntax definitions are loaded into the highlighter alongside the built-in language set.

What plugins can do

Plugins receive lifecycle and hook events from mantis and can respond with actions:

| Action | Effect | |—|—|—| | show_message | Displays a message in the status bar | | open_file | Opens a file in the content panel | | set_content | Replaces content panel with ANSI-escaped lines | | set_icon_map | Sets file-type icon glyphs (requires Nerd Font) | | register_language_provider | Declares file extensions and capabilities | | set_fold_regions | Provides fold regions for a file | | set_status_facts | Provides a short status-bar summary for a file | | register_commands | Adds commands to the Ctrl-P command palette |

Each action has specific parameters; see Plugin Development for the full protocol reference.

Protocol version

mantis and plugins communicate over an IPC protocol identified by a version string. Each plugin declares its protocol version in plugin.toml via the tv_protocol field. At startup mantis validates that every discovered plugin matches the host protocol version — plugins with a mismatched version are silently skipped. The init event sent to each plugin includes the host protocol version so the plugin can verify compatibility dynamically.

Current protocol version: "2" (bumped from "1" for the 0.8 release).

Upgrading from 0.7: Plugins written for protocol "1" must update tv_protocol = "2" in their plugin.toml and handle the new protocol_version field on the init event to remain compatible with 0.8+.

Lifecycle

1. mantis starts, reads [plugins] from config, and spawns each enabled plugin.
2. Each plugin receives an init event (with the active theme name and host protocol version).
3. As you use mantis, plugins receive hook events (on_file_open,
4. When you quit, each plugin receives on_quit then shutdown, and mantis waits for each subprocess to exit.

Plugin stderr is discarded (/dev/null). Write debug output to a log file instead.

Example: status-bar clock

A minimal shell plugin that shows the current time in the status bar on every file open:

#!/usr/bin/env bash
# ~/.config/mantis/plugins/clock.sh

while IFS= read -r line; do
    event=$(echo "$line" | python3 -c "import sys,json; print(json.load(sys.stdin).get('event',''))")
    case "$event" in
        on_file_open|init)
            ts=$(date +"%H:%M:%S")
            printf '{"event":"action","action":"show_message","params":{"message":"%s"}}\n' "$ts"
            ;;
        shutdown) exit 0 ;;
    esac
done

Register it:

[plugins]
clock = { path = "clock.sh" }

Bundled plugins

mantis ships with several bundled Rust plugins. Each is a workspace member compiled alongside mantis and installed on first run.

Bundled syntax plugins

mantis also bundles syntax-only plugins that provide highlighting for additional file types without spawning a subprocess.

All bundled plugins are compiled as workspace members and installed to the plugin directory the first time mantis creates its global config. They are all enabled by default. If you want to disable a bundled plugin, explicitly set enabled = false in your mantis.toml:

[plugins.rust]
enabled = false

Note: Git features are built into mantis natively — no plugin required. Git status colors, blame, file history (H, while the tree is focused), and working-tree diffs all work without any plugin enabled.

Auto-removal of retired plugins

When upgrading from a pre-0.8 install (which used shell-script plugins), superseded files (git-diff.sh, git-log.sh, iconize.sh) and their [plugins] config entries are silently removed on first launch. User-authored plugins are never touched.

Plugin Registry

mantis supports a git-backed plugin registry for discovering and installing third-party plugins. The registry is a plain git repository containing an index.json file that lists available plugins. No HTTP library is used — mantis uses git clone and git pull to sync the registry.

How it works

1. On first access, mantis clones the registry repository into the local cache at ~/.config/mantis/registry/.
2. On subsequent access, mantis refreshes the cache from the pinned main branch with git pull --ff-only.
3. The index.json file is parsed to build the list of available plugins.

Registry refreshes that cannot be fast-forwarded are recovered by cloning a fresh main checkout and replacing the cache only after the clone contains a valid index.json. If recovery fails, the previous cache is preserved when possible and the error is reported to the caller.

Bundled plugins (such as the built-in python language provider at plugins/python/) are not listed in the registry — they ship with mantis and are installed automatically at startup. See Plugin Development for how bundled plugins are structured.

Default registry

The default registry is hosted at:

https://github.com/ansromanov/mantis-plugins

To use a different registry, set the MANTIS_PLUGIN_REGISTRY environment variable:

export MANTIS_PLUGIN_REGISTRY="https://github.com/your-org/your-plugin-registry"

Cache location

The registry cache lives at:

Override with the MANTIS_PLUGIN_REGISTRY_DIR environment variable:

export MANTIS_PLUGIN_REGISTRY_DIR="/custom/path/to/registry"

index.json format

The registry repository must contain an index.json file at its root with the following structure:

{
  "plugins": [
    {
      "name": "git-tools",
      "description": "git diff/log integration",
      "repo": "https://github.com/example/tv-git-tools",
      "tag": "v0.1.0",
      "sha256": "<64 lowercase hexadecimal characters>"
    },
    {
      "name": "markdown-preview",
      "description": "Live markdown preview panel",
      "repo": "https://github.com/example/tv-md-preview",
      "tag": "v0.2.0",
      "sha256": "<64 lowercase hexadecimal characters>"
    }
  ]
}

Fields

Trust and consent

Registry entries are metadata only; a plugin must be verified before its artifact is installed. The host compares the downloaded artifact with the entry’s sha256 value and refuses a mismatch or a missing digest.

Discovered third-party plugin manifests are disabled by default. Discovery does not execute plugin code; the user must explicitly enable a plugin from the plugin manager or configuration. The manifest’s permissions field is advisory and describes requested access for review—it is not a sandbox.

Searching

Use the plugin picker in mantis (accessible via the plugin overlay) to search the registry by name or description. The search is case-insensitive and matches substrings in both name and description fields.

Resolution

To look up a specific plugin by name (e.g. for installation), mantis uses exact case-sensitive matching against the name field in index.json.

Hosting your own registry

To create your own plugin registry:

1. Create a new git repository.
2. Add an index.json file following the format above.
3. Push to a git remote (GitHub, GitLab, self-hosted, etc.).
4. Set MANTIS_PLUGIN_REGISTRY to your repository URL.

Example — create a minimal registry:

mkdir my-plugin-registry
cd my-plugin-registry
git init
cat > index.json << 'EOF'
{
  "plugins": [
    {
      "name": "my-plugin",
      "description": "My custom mantis plugin",
      "repo": "https://github.com/me/mantis-my-plugin",
      "tag": "v1.0.0"
    }
  ]
}
EOF
git add index.json
git commit -m "initial registry"
git remote add origin https://github.com/me/my-plugin-registry
git push -u origin main

Then point mantis at it:

export MANTIS_PLUGIN_REGISTRY="https://github.com/me/my-plugin-registry"

Tip: Make sure the repository is accessible without authentication for mantis to clone it. Public GitHub repos work out of the box.

Development

Prerequisites

• Rust (stable toolchain)
• just (optional, for the justfile recipes)

Commands

Or use the justfile shortcuts:

Before committing

1. cargo fmt --all — check formatting
2. cargo clippy --all-targets -- -D warnings — no warnings
3. cargo test — all tests pass
4. cargo check — no type errors
5. No debug println!, dbg!, or commented-out code

Project structure

src/
├── main.rs             # Entry: terminal setup, event loop, dispatch
├── lib.rs              # Crate root, re-exports the modules below
├── app/                # App state and input handling
│   ├── mod.rs          #   core App state + overlays
│   ├── key_handlers/   #   keyboard dispatch (incl. open-in-editor)
│   ├── mouse_handlers.rs #  click/scroll handling
│   ├── navigation.rs   #   tree movement & expand/collapse
│   ├── content_pos.rs  #   scroll / wrap position math
│   └── file_ops.rs     #   load files, JSON pretty-print, reloads
├── ui/                 # ratatui rendering
│   ├── mod.rs          #   layout & frame composition
│   ├── tree.rs         #   tree panel
│   ├── content/        #   content panel (incl. blame gutter, diffs)
│   ├── popups/         #   search / history / palette / help popups
│   └── statusbar.rs    #   status bar
├── config/             # mantis.toml deserialization, keybinding parsing
├── command_palette.rs  # Ctrl+P action list + fuzzy matching
├── search.rs           # fuzzy file + full-text content search
├── selection.rs        # text selection model
├── tree.rs             # Flat Vec<TreeNode> from ignore::WalkBuilder
├── file.rs             # Binary file detection (null-byte check)
├── virtual_file.rs     # memory-mapped, lazily indexed large files
├── theme.rs            # Theme struct + presets, color parsing
├── git.rs              # Shells out to `git` for log/diff/blame
├── highlight.rs        # syntect syntax highlighting → ratatui styles
└── release_info.rs     # bundled "what's new" release metadata

End-to-End (E2E) & Functional Testing

To ensure that releases do not introduce regressions (especially regarding terminal rendering, PTY initialization, and UI interactivity across different terminals), mantis uses a combination of automated and manual E2E/functional testing.

1. Test Dataset (e2e/data/)

A dedicated test dataset is located in the e2e/data/ directory. It contains static sample files representing different edge cases and supported file types:

• rust_sample.rs: Rust code structure to verify syntax highlighting, search, and line numbers.
• json_sample.json: Minified JSON to verify automatic pretty-printing.
• yaml_sample.yml: Nested YAML with anchors (&) and aliases (*) to verify indentation-based folding and counts.
• python_sample.py: Python source file.
• markdown_sample.md: Markdown document.
• long_lines.txt: Extremely long lines of text to verify word-wrapping behavior.
• crlf_sample.txt: Text file with Windows (\r\n) line endings to verify normalization to LF.
• bom_utf8_sample.txt: UTF-8 file with a Byte Order Mark (BOM) to verify BOM detection.
• binary_sample.bin: Binary data containing NUL bytes to verify binary placeholder rendering.

2. Automated E2E Testing

Automated E2E tests are split into two parts:

A. Cargo Integration Tests (tests/e2e_tests.rs)

Runs programmatically using a simulated App state and a TestBackend to verify file parsing, encoding detection, search matching, and folding logic.

B. Whole-Binary TUI Smoke Test (scripts/ci-e2e.py)

Spawns the compiled mantis binary under a pseudo-terminal (PTY) in Python, sets the terminal size, waits for it to render the TUI screen, verifies file tree listings, and exits cleanly with a simulated q keystroke. This verifies real-world raw-mode terminal initialization.

Running Automated E2E Tests

To run all automated E2E tests locally:

just test-e2e

These tests are also run automatically in CI on every Pull Request (in ci.yml) and push to main (in main.yml).

3. Manual Testing Checklist

Run through these verification steps on your target terminals before a release:

• Windows Terminal (PowerShell & WSL)
• iTerm2
• Ghostty
• Alacritty

Launch Command

Launch mantis targeting the test dataset directory:

cargo run -- ./e2e/data

Checklist Steps

See the per-terminal checklists in e2e/checklists/*.md (section “4. New Features”) for detailed step-by-step coverage of items 10–15.

Plugin Development

This page describes how to write both kinds of mantis plugins: process plugins (subprocess-based) and syntax plugins (.sublime-syntax files). See Plugins for how to install and configure plugins.

Plugin manifest (plugin.toml)

Every plugin must have a plugin.toml manifest file in its own subdirectory of the plugin directory (see Plugins for where that is). The manifest is how mantis discovers the plugin and learns its entry point, version, and other metadata.

Schema

name = "git-tools"                   # Required: plugin name (shown in picker)
version = "0.1.0"                    # Required: semver recommended
description = "git diff on open"     # Optional: one-line description
author = "ansromanov"                # Optional: author name/handle
entry = "run.sh"                     # Required: executable relative to this dir
mantis_protocol = "3"                # Required: IPC protocol version (tv_protocol still accepted, see below)
platforms = ["linux", "macos"]       # Optional: OS filter (default: all)
events = ["on_file_open"]            # Optional: events to subscribe to (empty/absent = all, for back-compat)
permissions = ["run_git"]            # Optional: required permissions (advisory)

Fields:

Protocol version

The mantis_protocol field (or its tv_protocol alias) must match the host’s expected protocol version. Plugins declaring a mismatched version are silently skipped during discovery. The host protocol version is also sent to each plugin on the init event (see below) so the plugin can verify compatibility dynamically.

Discovery

On startup mantis scans every subdirectory of the plugin directory for plugin.toml. Each discovered manifest produces a (name, PluginEntry) pair that appears in the plugin picker. Discovered plugins default to disabled — no code runs without explicit user opt-in via the picker or mantis.toml.

If a plugin is also declared in [plugins] in mantis.toml, the explicit config entry takes precedence (allowing the user to override the entry path, enable it, or set its kind).

Process plugins

The protocol for subprocess-based plugins.

Protocol overview

A process plugin is any executable that:

1. Reads newline-delimited JSON objects from stdin (events from mantis).
2. Writes newline-delimited JSON objects to stdout (actions back to mantis).
3. Exits cleanly when it receives shutdown (or when stdin closes).

mantis spawns each plugin as a subprocess with stdin, stdout, and stderr all piped. A background reader thread drains each plugin’s stdout and a background writer thread handles stdin so the mantis event loop never blocks on plugin I/O. A third background thread drains stderr: it keeps the most recent line in memory and appends sanitized output to a rotating log file under the state directory (plugin-logs/<name>.log, capped at 64 KB). If the plugin exits unexpectedly, that last line and log path are surfaced in the “exited unexpectedly” message and as a badge in the plugin picker.

Events: tv → plugin (stdin)

Each event is one JSON object on a single line. Unknown fields are ignored.

init

Sent once immediately after spawn, before any user interaction. Includes the host protocol version so the plugin can verify it is compatible.

{
  "event": "init",
  "theme": "default",
  "colors": {
    "heading1": "#5fd7ff", "heading2": "#ffffaf", "heading3": "#afffaf",
    "accent": "#00ffff", "dim": "#767676", "code": "#ffffaf", "text": "#ffffff"
  },
  "protocol_version": "2"
}

The protocol_version field is present only on init. If the value does not match what the plugin expects, the plugin should exit gracefully or fall back to a compatible subset of features.

The colors field carries the active theme’s actual colors for seven roles (heading1, heading2, heading3, accent, dim, code, text) as #rrggbb hex strings, resolved from the theme’s real definition — including custom themes from mantis.toml. Plugins should use these directly (e.g. as truecolor ANSI, \x1b[38;2;R;G;Bm) instead of hardcoding a palette per theme name, so any theme renders correctly without the plugin needing to know it by name. colors may be absent from an older host; fall back to a built-in default palette in that case.

on_file_open

Sent when the user opens a file in the content panel.

{"event":"on_file_open","path":"/absolute/path/to/file"}

on_keypress

Sent on every keypress, including inside overlays. The key field uses human-readable notation: "q", "ctrl+c", "Enter".

{"event":"on_keypress","key":"ctrl+p"}

Key consumption (protocol 3+). A plugin that has on_keypress in its manifest events list may reply with a key_handled action to claim the keypress:

{"event":"action","action":"key_handled","params":{"handled":true}}

When at least one subscribed plugin replies handled: true, mantis waits up to one tick (~16ms) after dispatching on_keypress before deciding whether to also run its own normal-mode key handling for that key. If any reply arrives with handled: true within that window, mantis swallows the key — no built-in binding fires for it. If multiple subscribed plugins reply, the first handled: true response the host receives within the window wins and the key is consumed exactly once; a plugin that doesn’t reply within the window is treated as not having handled the key. Plugins that never send key_handled behave exactly as under protocol 2 — the keypress always falls through to normal handling.

on_selection_change

Sent when the tree cursor moves to a different entry or the content cursor moves to a different source line. path is absent if the tree is empty. When the selection refers to an open text file, line contains its zero-based physical source line; tree-only selections omit it.

{"event":"on_selection_change","path":"/absolute/path/to/entry","line":12}

on_theme_change

Sent when the user switches themes at runtime (via the theme picker or command palette). The theme field carries the new theme name exactly as configured, and colors carries its resolved colors (same shape as on init; see above).

{
  "event": "on_theme_change",
  "theme": "monokai",
  "colors": {
    "heading1": "#5fd7ff", "heading2": "#ffd787", "heading3": "#afd787",
    "accent": "#af87d7", "dim": "#6c6c6c", "code": "#ffd787", "text": "#ffffff"
  }
}

command (protocol 3+)

Sent when the user selects one of the plugin’s palette commands (see the register_commands action below). params.id is the command’s stable id exactly as the plugin registered it.

{"event":"command","params":{"id":"my-plugin.do-thing"}}

on_quit

Sent when the user initiates a quit (before shutdown). Use this to do any final work before the process is torn down.

{"event":"on_quit"}

shutdown

Sent as the final event. mantis closes stdin immediately after sending this. Exit cleanly in response.

{"event":"shutdown"}

Requests: mantis ⇄ plugin (protocol 3+)

Protocol 2 is one-way and fire-and-forget in both directions: the host emits events, the plugin emits actions, and neither side can ask the other for something and wait for a specific reply. Protocol 3 adds a correlated request/response pair on top of the existing event/action stream, used for capabilities that need an answer to a specific question (e.g. “fold regions for this file, now”) rather than a broadcast the plugin may or may not act on.

Host → plugin request, sent on stdin like any other event:

{"event":"request","id":42,"method":"fold_regions","params":{"path":"/absolute/path/to/file"}}

Plugin → host response, sent on stdout as its own line, alongside (but distinct from) action lines:

{"event":"response","id":42,"result":{"regions":[[0,5],[10,20]]}}

or, on failure:

{"event":"response","id":42,"error":{"message":"failed to parse file"}}

Rules:

• id is chosen by the host per outstanding request and must be echoed back unchanged in the response. IDs are not reused while a request is outstanding.
• Exactly one of result / error must be present.
• The host applies a per-plugin timeout to each request (a bounded number of ticks). If no response arrives in time, the host treats it as an error, logs it the same way as a plugin_error (see below), and does not kill the plugin — a slow or missed response degrades gracefully rather than being fatal.
• request/response is additive to the existing event/action stream, not a replacement: set_fold_regions pushed unprompted still works exactly as in protocol 2 for plugins that don’t implement requests. The host only sends request events to plugins that declared protocol 3 in their manifest.

This is the surface the reserved hover, diagnostics, and definition capabilities are expected to use once implemented — each as a method name on the same request/response pair, gated by the corresponding capability in register_language_provider.

Actions: plugin → tv (stdout)

Respond with action objects on stdout. Each object must be on a single line. Lines that are not valid JSON or that lack "event":"action" are silently ignored.

show_message

Displays a message in the mantis status bar.

{"event":"action","action":"show_message","params":{"message":"hello from plugin"}}

plugin_error (protocol 3+)

Reports a failure that isn’t tied to a specific request/response pair (for example, a subscription-only plugin that failed to act on a broadcast event). Distinct from show_message: it is recorded in the plugin’s rotating log file (plugin-logs/<name>.log) and surfaced with error styling in the status bar and plugin picker, rather than treated as routine status text.

{"event":"action","action":"plugin_error","params":{"message":"failed to parse file","context":"on_file_open"}}

Fields:

• message — human-readable error description.
• context — optional free-form string naming the event/method that failed (advisory, shown alongside the message).

open_file

Opens a file in the content panel.

{"event":"action","action":"open_file","params":{"path":"/tmp/output.txt"}}

set_content

Replaces the content panel with the given lines. Each line is a string that may contain ANSI escape codes for colour and styling. mantis parses the ANSI codes with its built-in parser and displays them as styled text. Handy for plugins that generate rich output (e.g. markdown renderers, linters).

{"event":"action","action":"set_content","params":{"lines":["\u001b[32mgreen line\u001b[0m","plain line"]}}

set_icon_map

Sets the file-type icon glyphs used in the tree. Requires icons = true in mantis.toml and a Nerd Font terminal. Keys in icons are file extensions (lowercase) or full filenames for extensionless files (e.g. "dockerfile").

{"event":"action","action":"set_icon_map","params":{"dir_open":"","dir_closed":"","fallback":"","icons":{"rs":"","py":"","dockerfile":""}}}

Fields:

• dir_open — glyph for open directories
• dir_closed — glyph for closed directories
• fallback — glyph used when no extension key matches
• icons — map of extension/filename → glyph

Once icons are active, the tree’s ▶/▼ expand/collapse arrows are suppressed — the dir_open/dir_closed glyph substitutes as the expansion indicator instead.

register_commands (protocol 3+)

Contributes commands to the Ctrl-P command palette. Typically sent once in response to init. Registered commands appear in the palette after the built-in commands (they participate in fuzzy search but not in frecency ranking) and are always applicable. When the user selects one, the host sends a command event back to the plugin with the command’s id (see the events section above).

{"event":"action","action":"register_commands","params":{"commands":[
  {"id":"my-plugin.do-thing","name":"Do the thing","category":"Plugin","description":"runs the thing"}
]}}

Fields per command:

• id — stable identifier, echoed back in the command event on selection. Prefix it with your plugin name to avoid collisions with built-in action ids.
• name — display name shown in the palette.
• category — optional grouping label shown as a dimmed prefix.
• description — optional one-line description shown dim after the name.

Re-registration replaces the plugin’s previous command list entirely; sending an empty commands array clears it.

Language providers

A process plugin can declare itself as a language provider by responding to the init event with a register_language_provider action. This tells mantis which file extensions the plugin handles and what capabilities it provides. fold is implemented via push (set_fold_regions); highlight is formally reserved (see below). The reserved capabilities (hover, diagnostics, definition) are expected to slot in as request/response methods (see Requests: mantis ⇄ plugin) once implemented, without a protocol break.

Provider contract

The language provider contract between mantis and a plugin follows a strict lifecycle:

1. Registration. Immediately after receiving init, the plugin sends register_language_provider to declare its extensions and capabilities. Registration is expected once per plugin — re-registration overwrites the previous registration entirely.

2. File routing. When the user opens a file whose extension matches a registered provider, mantis routes relevant events (on_file_open, on_selection_change) and capability-driven state requests to that provider. When exactly one provider matches an extension+capability pair, it is used. When more than one provider registers the same extension+capability (protocol 3+), the registration with the higher priority wins; ties break by registration order (first registered wins). The first time this happens for a given extension+capability pair, mantis shows a one-time status-bar warning naming both plugins, so the conflict isn’t silent. Two providers can register the same extension without conflicting as long as they declare different capabilities — e.g. the bundled yaml plugin owns fold for .yaml/.yml while the bundled k8s plugin owns status_facts for the same extensions. fold and status_facts drive backend state (fold regions, status-bar text, respectively); highlight is reserved for future use (see below).

3. Response. For each declared capability, the plugin should respond to file-related events with the corresponding action:

   • fold → respond with set_fold_regions when a matching file is opened (see below).
   • status_facts → respond with set_status_facts when a matching file is opened (see below).
   • highlight → reserved for future use.

4. Lifetime. Provider registrations persist for the entire plugin session. When a plugin exits or is deactivated, its registrations are removed. If the plugin sends set_fold_regions for a file before it is opened, mantis caches the regions and applies them when the file is opened later.

5. Capability gating. mantis enforces capability checks at runtime. For example, set_fold_regions is only accepted when the sender has a registered provider with the fold capability for that file’s extension. Unknown capability strings are silently ignored, so existing providers remain compatible with future protocol extensions.

register_language_provider

Sent by the plugin immediately after receiving init. Declares the file extensions and capabilities the plugin provides. mantis stores the registration and uses it to route the correct events and display-state updates for each open file.

{"event":"action","action":"register_language_provider","params":{
  "extensions": ["py", "pyi"],
  "capabilities": ["fold"],
  "priority": 10
}}

Fields:

• extensions — lowercase file extensions (no leading dot) this provider handles.
• capabilities — one or more of "highlight", "fold", or "status_facts". Reserved for future use: "hover", "diagnostics", "definition".
• priority — optional signed integer, default 0 (protocol 3+). Used only to break ties when two providers register the same extension+capability pair; higher wins. Absent on protocol 2 plugins, which are treated as priority 0.

On highlight: it remains declared but formally reserved as of protocol 3 — mantis accepts the registration and never dispatches anything for it. Real syntax highlighting is intentionally not routed through language providers; it flows through syntax plugins (.sublime-syntax files loaded into syntect, see Syntax plugins below) or the built-in highlighter. This was evaluated as part of the #296 capability audit and re-confirmed for v3: provider-driven highlighting would mean re-deriving styled spans over IPC per file/edit, which the syntect path already does locally and faster. Revisit only if a concrete plugin use case needs highlighting decisions syntect’s grammar model can’t express.

After registering, mantis sends on_file_open whenever a matching file is opened. The plugin should respond with the appropriate action for each declared capability (e.g. set_fold_regions for "fold").

set_fold_regions

Provides fold regions for a file. Plugin-supplied regions override the built-in YAML indentation-based folding (the reference implementation) for that file. Each region is a [start_line, end_line] pair (0-indexed, inclusive). When the named file is currently open the regions are applied immediately; when it is not yet open they are cached and applied the next time the file is opened.

Fold regions from a plugin are only accepted when mantis has a registered language provider with the fold capability for the file’s extension. Regions from unregistered plugins or for unmatched extensions are silently discarded.

{"event":"action","action":"set_fold_regions","params":{
  "path": "/absolute/path/to/file",
  "regions": [[0, 5], [10, 20]]
}}

set_status_facts

Provides a short, plugin-owned summary string shown in the status bar alongside the fold-count segment when the named file is the one currently open — e.g. 3 pubs · 12 fns for a Rust file, or a Kubernetes resource’s identity (Deployment/nginx (default)). Unlike set_fold_regions, this carries free text rather than a structured value, so the host does not interpret it beyond displaying it.

Status facts from a plugin are only accepted when mantis has a registered language provider with the status_facts capability for the file’s extension. An empty text clears any previously set fact for that path (useful when a provider detects the file no longer qualifies, e.g. a YAML file that stopped looking like a Kubernetes manifest after an edit).

{"event":"action","action":"set_status_facts","params":{
  "path": "/absolute/path/to/file",
  "text": "Deployment/nginx (default)"
}}

Rules

• One JSON object per line. No pretty-printing, no multi-line objects.
• Stdout is for actions only. Don’t write debug output there — it will break the protocol. Write to stderr instead: mantis captures it for crash diagnostics (the last line and a rotating on-disk log), but does not otherwise act on it.
• Exit on shutdown. When stdin closes or you receive shutdown, exit. Do not loop forever waiting for more input.
• Idempotent reads. mantis may send multiple on_file_open events for the same path if the user reopens a file.
• No blocking. Actions are drained non-blockingly every tick. Sending many actions in rapid succession is fine; they are buffered and processed in order.

State teardown contract

Every set_* action a plugin sends registers a contribution in the host’s plugin_contributions map (HashMap<String, PluginContributions>). When the plugin is disabled via the plugin picker or its process exits unexpectedly, the host automatically tears down all state that plugin produced — no per-plugin special cases needed.

What gets torn down:

After clearing, if the disabled plugin had rendered content for the current file, the file is reloaded from disk and falls back to core rendering (markdown, JSON pretty-print, or plain-text with syntax highlighting).

Plugin authors: There is nothing you need to do to opt in — registration is automatic. If you write a new set_* action in the host code, you must also stamp it in PluginContributions (in src/plugin/types.rs) and handle its teardown in App::teardown_plugin_contributions (in src/app/mod.rs). Without this, the disabled plugin’s output would persist on screen, violating the invariant: disabled plugin = zero observable effect.

Minimal Rust example

All bundled plugins are Rust crates under plugins/. The simplest possible plugin responds to init with a status message:

use std::io::{self, BufRead, Write};

fn main() {
    let stdin = io::stdin();
    let stdout = io::stdout();

    for line in stdin.lock().lines() {
        let line = match line {
            Ok(l) => l,
            Err(_) => break,
        };
        let trimmed = line.trim();
        if trimmed.is_empty() {
            continue;
        }
        let msg: serde_json::Value = match serde_json::from_str(trimmed) {
            Ok(v) => v,
            Err(_) => continue,
        };
        match msg["event"].as_str().unwrap_or("") {
            "init" => {
                let response = serde_json::json!({
                    "event": "action",
                    "action": "show_message",
                    "params": {"message": "hello from plugin"}
                });
                let _ = writeln!(stdout.lock(), "{}",
                    serde_json::to_string(&response).unwrap());
            }
            "shutdown" => break,
            _ => {}
        }
    }
}

Architecture notes

• src/plugin/ owns the subprocess lifecycle, the background reader thread per plugin, manifest parsing, binary install, and syntax discovery.
• PluginManager (src/plugin/manager.rs) collects plugin actions into an internal buffer; App::tick() drains them via drain_plugin_actions() in src/app/refresh.rs.
• Hook dispatch (on_file_open, on_keypress, on_selection_change) happens in src/app/file_ops.rs, src/app/key_handlers/, and src/app/navigation.rs respectively.
• Plugin config deserialization lives in src/config/mod.rs under the plugins key.
• Bundled plugins are declared in BUNDLED_PLUGINS (src/plugin/install.rs) as (name, binary_name) pairs and built as workspace-member Rust crates under plugins/. The install_bundled_plugins() function finds and copies compiled binaries to the plugin directory on first run. The python plugin is a language-provider example: it registers for py/pyi with fold capability at init and sends set_fold_regions on on_file_open using the shared mantis::fold_detectors::indent_fold detector. The json plugin follows the same shape for .json files, using mantis::fold_detectors::brace_fold_with_brackets (a brace_fold variant that also folds […] arrays) run against the same pretty-printed text core renders by default, rather than the raw file — otherwise fold-region line numbers would not line up with what’s on screen for minified JSON. The yaml plugin follows the same shape for yaml/yml files, using the shared mantis::fold_detectors::yaml_fold detector — the same algorithm the built-in crate::yaml_fold::detect_fold_regions re-exports.

Syntax plugins

Syntax plugins provide .sublime-syntax files that extend the built-in syntect-based highlighter. No subprocess is spawned.

How they work

A syntax plugin is simply a .sublime-syntax file (Sublime Text syntax definition format, YAML-based). At startup:

1. Files in {plugin_dir}/syntaxes/ are auto-discovered and loaded.
2. Explicit [plugins] entries with kind = "syntax" are also loaded.
3. Each syntax definition is added to the SyntaxSet so syntect associates its declared file extensions with highlights.

Writing a syntax definition

The .sublime-syntax format is documented in the Sublime Text docs. A minimal syntax file looks like:

%YAML 1.2
---
name: My Language
file_extensions: [ext1, ext2]
scope: source.my_lang

contexts:
  main:
    - match: '#.*'
      scope: comment.line.number-sign.my_lang
    - match: '\b(keyword)\b'
      scope: keyword.control.my_lang

The file_extensions key tells syntect which files to highlight with this syntax. The scope key defines the base scope for highlighting, and contexts define the matching rules.

Bundled syntax plugins

mantis ships with a terraform.sublime-syntax file that is automatically installed to {plugin_dir}/syntaxes/ on first run. It provides syntax highlighting for .tf and .tfvars files (Terraform / HCL). Enable it by:

[plugins]
terraform = { kind = "syntax", syntax_file = "syntaxes/terraform.sublime-syntax",
              extensions = ["tf", "tfvars"] }

Or simply leave it in the syntaxes/ directory for auto-discovery (no config entry needed).

Architecture notes

• src/highlight.rs::with_extra_syntaxes() loads extra syntax definitions into the syntax set.
• src/plugin.rs::load_extra_syntaxes() collects syntax plugins from config entries and the syntaxes/ directory.
• Syntax definitions are loaded once at startup and shared between the main thread’s Highlighter and the background loader thread’s Highlighter.

Plugin Capability Matrix

Audit of the plugin protocol (v2) as of 0.12.x: what the protocol declares, what the host actually implements, and what the bundled plugins use. This is the “take stock” pass after the 0.8 plugin work (issue #296). For the protocol itself — message formats, examples, contribution/teardown rules — see Plugin Development.

Capabilities

Capabilities are declared by a plugin in its register_language_provider action and stored as Capability variants (src/plugin/types.rs). The host routes them via PluginManager::provider_for (src/plugin/manager.rs).

Note on highlight: real syntax highlighting flows through syntax plugins (kind = "syntax", a .sublime-syntax file fed to syntect — see the bundled terraform plugin), not through language-provider capabilities. The highlight capability is documented as reserved for future provider-driven highlighting; today registering it has no effect.

Actions

Every action the host accepts, dispatched in App::handle_plugin_action (src/app/refresh.rs). Unknown actions are silently ignored.

Teardown status: every stateful set_* action stamps PluginContributions and is cleared by App::teardown_plugin_contributions (src/app/mod.rs). No teardown gaps were found in this audit.

Protocol v1 git actions (set_file_statuses, set_blame_data, set_status_bar_git_info) were removed in 0.11.22 along with the retired shell-script git plugins; git features are built in. They are listed in the version history in Plugin Development only.

Bundled plugins

Gaps and follow-ups

1. Reserved capabilities (hover, diagnostics, definition) are unimplementable in protocol v2 — they need id-correlated request/response. Tracked in the protocol v3 proposal (issue #481), which names this audit as its precursor.
2. The language-provider fold pipeline has bundled consumers — register_language_provider + Capability::Fold + set_fold_regions are used by the bundled rust (issue #599), go (issue #600), python (issue #601), json (issue #604), sh (issue #605), and yaml (issue #603) language provider plugins. The rust and go plugins register the fold capability for .rs and .go files via the shared brace_fold detector (#598); the python plugin uses the shared indent_fold detector; the json plugin uses brace_fold_with_brackets, a brace_fold variant that also folds […] arrays; the sh plugin uses shell_brace_fold, a shell-specific variant that handles # line comments, single/double quoted strings, and heredocs; the yaml plugin uses the shared yaml_fold detector — the same algorithm the built-in crate::yaml_fold::detect_fold_regions re-exports, so plugin-enabled and built-in YAML folding agree. Built-in YAML folding (compute_file_load in src/app/loader.rs) is unchanged in this phase — it still dispatches to yaml_fold::detect_fold_regions directly, and the plugin’s regions only take over when the plugin is enabled (existing override precedence in handle_plugin_set_fold_regions). Retiring the built-in dispatch is a separate follow-up (issue #603 phase 2), deferred until bundled plugins have a default-enabled mechanism. Known limitation: provider routing is extension-based; extensionless scripts with a #!/bin/bash shebang won’t route to the plugin. Shebang routing is a host/protocol gap (see #605).
3. Capability::Highlight is declared but routes to nothing. Either implement provider-driven highlighting in v3 or re-document it as reserved alongside hover/diagnostics/definition. Not yet tracked in a dedicated issue; candidate checklist item for #481.
4. status_facts/set_status_facts (0.18.x) resolves the protocol gap that blocked issue #606 (k8s manifest awareness): the epic’s “per-language statusbar facts” item (originally #482, merged into #602) had no protocol surface, and #606 was filed as a proposal rather than a build order for exactly that reason. The new capability is deliberately generic free text, not a structured breadcrumb — the bundled k8s plugin uses it for both candidate features from #606 (resource identity and multi-doc per-kind counts) combined into one string, rather than adding a second breadcrumb capability. Not yet solved: per-cursor “which resource is the viewport in right now” needs the host to send line/cursor position on on_selection_change, which the protocol still doesn’t carry — the k8s plugin reports the first resource in the file instead of the one under the cursor. That’s a separate, still-open protocol gap.

Roadmap

Last updated: 2026-07-03. Living document — the epics linked below are the source of truth for status; this page explains the why and the sequencing.

Positioning: the reading tool for the AI era

mantis’s pitch has always been a fast way to read code without launching an editor. The opportunity in front of it: in agent-driven development, humans write less and read more. Every coding-agent session produces diffs someone must review, logs someone must check, YAML someone must sanity-check. Editors are optimized for writing; mantis can own the reading and reviewing half of the loop — for humans and for the agents themselves.

Vision: mantis is the review cockpit for humans working with AI agents, and the fastest repo-reading surface for the agents themselves.

Personas

1. Backend engineer — reads unfamiliar services, reviews PRs and agent diffs, jumps between code and JSON/YAML fixtures.
2. DevOps / SRE — lives over SSH; reads k8s manifests, Terraform, .envs, and logs; needs instant startup on remote boxes.
3. AI engineer / agent operator — runs coding agents; wants to watch what the agent changes in real time, feed context into prompts, and give agents tools they can call.

Non-goals (the moat)

Every feature below stays read-only and zero-config by default. mantis will not grow: editing, LSP/IntelliSense, an embedded terminal, a debugger, or a plugin-language runtime. When a feature needs to write, it hands off (to $EDITOR, to the clipboard, to stdout).

The four pillars

1. Agent review cockpit

Epic: #469

The highest-leverage new surface. The primitives already exist (file watcher, git status/diff, side-by-side rendering) — this pillar composes them:

• Prompt-ready copy — copy selection/file as a fenced markdown block with language and path:line header; the format every agent prompt wants.
• Diff-first startup — mantis --diff [base] opens straight into git mode against HEAD, a branch, or a range (main...).
• Watch mode / review dashboard — mantis --review: a changed-files panel that refreshes while the agent edits; hunk-walking across files; per-file “seen” marks.
• Session summary — on quit, a plain-text list of files/hunks reviewed.

2. Machine interface

Epic: #470

Make mantis useful to the agents themselves. mantis is already a library crate; expose it without the TUI:

• Headless JSON CLI — mantis cat --range … --json, mantis search --json, mantis tree --json, mantis blame --json.
• MCP server — mantis mcp exposing file-slice, search, diff, blame, and tree tools to any MCP-capable client.
• Remote-control socket — mantis --listen <socket> so an external agent can drive a running viewer (“show the user this diff”).
• Protocol hygiene — rename the plugin manifest’s tv_protocol field to mantis_protocol (with back-compat) before third-party plugins multiply.

3. DevOps reader

Epic: #471

mantis’s home turf is the terminal over SSH; teach it operational data, not just code:

• Log follow mode (tail-style) with level/timestamp colorizing and a filter bar; JSONL rendering for structured logs.
• JSON path breadcrumb and a jq-style query bar.
• CSV/TSV table view (#71).
• Secret masking for .env/credential-shaped files with a reveal toggle.
• Remote browsing over SSH (#359) — sequenced after log mode; it multiplies everything else in this pillar.

4. Reading UX polish

Epic: #472

Continuous ergonomics investment: theme live preview, scrollable help, onboarding hints, regex/case search toggles, sticky scroll, bookmarks, a context menu, a jump-back navigation stack, line wrap, search result counts.

This pillar is where the overlay count keeps growing (about, blame, and now help all render scrollable popups; bookmarks and the context menu add more). Each new scrollable overlay is a prompt to check whether the ad hoc xxx_scroll field + inline key/mouse match introduced for help should graduate into a shared ScrollState-style helper (see AGENTS.md → Consistency & performance) rather than being copied a third time.

5. Language intelligence (Rust · Python · Go)

Epic: #482

Syntax highlighting already covers these; this pillar adds language-aware reading, built in and zero-config like the shipped YAML folding:

• Code folding for Rust/Go (brace-based) and Python (indentation-based) — starter issue #483.
• Symbol outline / go-to-symbol fuzzy picker (regex-based, deliberately not tree-sitter — binary size is a feature).
• Scope context in the breadcrumb, which also feeds sticky scroll (#199).

6. File-type coverage via plugins

Epic: #485

Beyond the three built-in languages, coverage grows through plugins in two tiers. Syntax packs (.sublime-syntax, terraform-style): TOML, TypeScript/TSX, and Dockerfile bundled first (#486), then Protobuf/GraphQL/Jinja2/nginx and friends via the registry. Rich viewers (process plugins): a Jupyter .ipynb renderer and a GGUF/safetensors model-metadata viewer headline the AI persona; Parquet/SQLite previews and a PEM/JWT decoder serve DevOps. Rich viewers are blocked on the 64 KB plugin content cap (#449).

Cross-cutting: plugin system hardening

The plugin system is the extension surface for pillars 2, 3, and 5, and a July 2026 review filed its prerequisites: ship bundled plugins in releases (#477), remove the startup cargo build fallback (#478 — security), plugin stderr diagnostics (#479), a registry trust model before the install UI ships (#480), and protocol v3 (request/response, key consumption, provider priorities — #481).

Engineering principles

Every change — feature, fix, refactor — is planned before it’s coded, not improvised diff-by-diff. Two questions guide that planning, in order:

1. Does this shape already exist somewhere in the app? (an overlay, a picker, a scroll offset, a clamp). If yes, reuse or extend it instead of writing a parallel copy.
2. Will this shape recur? If a second consumer is foreseeable (the next overlay, the next picker), design the shared primitive now so the second consumer extends it instead of duplicating it. If not, keep it local — this is not license to abstract on the first use case.

AGENTS.md → “Consistency & performance” is the enforced version of this for Rust code; this section states the intent behind that rule so it stays legible as the codebase (and this roadmap) grows.

Sequencing

First two bets: prompt-ready copy (days of work, immediate daily-use hook for the AI crowd) and log follow mode (biggest persona expansion per unit of effort — the machinery is ~80% built).

North-star metrics

• Time-to-first-render stays under 50 ms — every feature is gated on this.
• Weekly installs (Homebrew / install script).
• Share of sessions using git/diff mode — are we becoming the review tool?
• MCP tool-call volume, once shipped.