merge: resolve conflict with origin/main

Problem: the README and vimdoc presets list omitted `plantuml` and
`mermaid` after both were added.

Solution: add both presets to the vimdoc table and the README features
blurb.

README.md

@@ -11,10 +11,9 @@ Typst, Markdown, etc.)—diagnostics included.
 
 - Async compilation via `vim.system()`
 - Built-in presets for Typst, LaTeX (latexmk, pdflatex, tectonic), Markdown,
-  GitHub-flavored Markdown, AsciiDoc, and Quarto
+  GitHub-flavored Markdown, AsciiDoc, PlantUML, Mermaid, and Quarto
-- Compiler errors as native `vim.diagnostic`
+- Compiler errors via `vim.diagnostic` or quickfix
-- User events for extensibility (`PreviewCompileStarted`,
+- Previewer auto-close on buffer deletion
-  `PreviewCompileSuccess`, `PreviewCompileFailed`)
 
 ## Requirements
 
@@ -22,8 +21,18 @@ Typst, Markdown, etc.)—diagnostics included.
 
 ## Installation
 
-Install with your package manager of choice or via
+With lazy.nvim:
-[luarocks](https://luarocks.org/modules/barrettruth/preview.nvim):
+
+```lua
+{
+  'barrettruth/preview.nvim',
+  init = function()
+    vim.g.preview = { typst = true, latex = true }
+  end,
+}
+```
+
+Or via [luarocks](https://luarocks.org/modules/barrettruth/preview.nvim):
 
 ```
 luarocks install preview.nvim
@@ -40,7 +49,7 @@ luarocks install preview.nvim
 **Q: How do I define a custom provider?**
 
 ```lua
-require('preview').setup({
+vim.g.preview = {
   rst = {
     cmd = { 'rst2html' },
     args = function(ctx)
@@ -50,15 +59,15 @@ require('preview').setup({
       return ctx.file:gsub('%.rst$', '.html')
     end,
   },
-})
+}
 ```
 
 **Q: How do I override a preset?**
 
 ```lua
-require('preview').setup({
+vim.g.preview = {
   typst = { env = { TYPST_FONT_PATHS = '/usr/share/fonts' } },
-})
+}
 ```
 
 **Q: How do I automatically open the output file?**
@@ -68,7 +77,7 @@ open the output with `vim.ui.open()` after the first successful compilation in
 toggle/watch mode. For a specific application, pass a command table:
 
 ```lua
-require('preview').setup({
+vim.g.preview = {
   typst = { open = { 'sioyek', '--new-instance' } },
-})
+}
 ```

doc/preview.nvim.txt

@@ -1,274 +0,0 @@
-*preview.nvim.txt*                    Async document compilation for Neovim
-
-Author:  Barrett Ruth <br.barrettruth@gmail.com>
-License: MIT
-
-==============================================================================
-INTRODUCTION                                                    *preview.nvim*
-
-preview.nvim is an extensible framework for compiling documents asynchronously
-in Neovim. It provides a unified interface for any compilation workflow —
-LaTeX, Typst, Markdown, or anything else with a CLI compiler.
-
-The plugin ships with opt-in presets for common tools (Typst, LaTeX, Pandoc,
-AsciiDoc, Quarto) and supports fully custom providers.
-See |preview.nvim-presets|.
-
-==============================================================================
-REQUIREMENTS                                          *preview.nvim-requirements*
-
-- Neovim >= 0.11.0
-- A compiler binary for each configured provider (e.g. `typst`, `latexmk`)
-
-==============================================================================
-SETUP                                                  *preview.nvim-setup*
-
-Load preview.nvim with your package manager. For example, with lazy.nvim: >lua
-    {
-      'barrettruth/preview.nvim',
-    }
-<
-Call |preview.setup()| to configure providers before use.
-
-==============================================================================
-CONFIGURATION                                      *preview.nvim-configuration*
-
-Configure via `require('preview').setup()`.
-
-                                                            *preview.setup()*
-setup({opts?})
-
-  `opts` is a table where keys are preset names or filetypes. For each
-  key `k` with value `v` (excluding `debug`):
-
-  - If `k` is a preset name and `v` is `true`, the preset is registered
-    as-is under its filetype.
-  - If `k` is a preset name and `v` is a table, it is deep-merged with
-    the preset and registered under the preset's filetype.
-  - If `k` is not a preset name and `v` is a table, it is registered
-    directly as a custom provider keyed by filetype `k`.
-  - If `v` is `false`, the entry is skipped (no-op).
-
-  See |preview.nvim-presets| for available preset names.
-
-  Fields:~
-
-  `debug`            boolean|string   Enable debug logging. A string value
-                                    is treated as a log file path.
-                                    Default: `false`
-
-                                                    *preview.ProviderConfig*
-Provider fields:~
-
-  `cmd`              string[]         The compiler command (required).
-
-  `args`             string[]|function  Additional arguments. If a function,
-                                      receives a |preview.Context| and returns
-                                      a string[].
-
-  `cwd`              string|function   Working directory. If a function,
-                                      receives a |preview.Context|. Default:
-                                      git root or file directory.
-
-  `env`              table             Environment variables.
-
-  `output`           string|function   Output file path. If a function,
-                                      receives a |preview.Context|.
-
-  `error_parser`     function          Receives (output, |preview.Context|)
-                                      and returns vim.Diagnostic[].
-
-  `errors`           false|'diagnostic'|'quickfix'
-                                      How parse errors are reported.
-                                      `false` suppresses error handling.
-                                      `'quickfix'` populates the quickfix
-                                      list and opens it. Default:
-                                      `'diagnostic'`.
-
-  `clean`            string[]|function  Command to remove build artifacts.
-                                       If a function, receives a
-                                       |preview.Context|.
-
-  `open`             boolean|string[]   Open the output file after the first
-                                       successful compilation in toggle/watch
-                                       mode. `true` uses |vim.ui.open()|. A
-                                       string[] is run as a command with the
-                                       output path appended. When a string[]
-                                       is used the viewer process is tracked
-                                       and sent SIGTERM when the buffer is
-                                       deleted. `true` and single-instance
-                                       apps (e.g. Chrome) do not support
-                                       auto-close.
-
-  `reload`           boolean|string[]|function
-                                       Reload the output after recompilation.
-                                       `true` uses a built-in SSE server for
-                                       HTML files. A string[] is run as a
-                                       command. If a function, receives a
-                                       |preview.Context| and returns a
-                                       string[].
-
-                                                        *preview.Context*
-Context fields:~
-
-  `bufnr`   integer    Buffer number.
-  `file`    string     Absolute file path.
-  `root`    string     Project root (git root or file directory).
-  `ft`      string     Filetype.
-  `output`  string?    Resolved output file path (set after `output`
-                       is evaluated, available to `args` functions).
-
-Example enabling presets:~
->lua
-    require('preview').setup({ typst = true, latex = true, github = true })
-<
-
-Example overriding a preset field:~
->lua
-    require('preview').setup({
-      typst = { open = { 'sioyek', '--new-instance' } },
-    })
-<
-
-Example overriding the output path (e.g. latexmk `$out_dir`):~
->lua
-    require('preview').setup({
-      latex = {
-        output = function(ctx)
-          return 'build/' .. vim.fn.fnamemodify(ctx.file, ':t:r') .. '.pdf'
-        end,
-      },
-    })
-<
-
-Example with a fully custom provider (key is not a preset name):~
->lua
-    require('preview').setup({
-      rst = {
-        cmd = { 'rst2html' },
-        args = function(ctx)
-          return { ctx.file }
-        end,
-        output = function(ctx)
-          return ctx.file:gsub('%.rst$', '.html')
-        end,
-      },
-    })
-<
-
-==============================================================================
-PRESETS                                                *preview.nvim-presets*
-
-preview.nvim ships with pre-built provider configurations for common tools.
-Import them from `preview.presets`:
-
-  `presets.typst`              typst compile → PDF
-  `presets.latex`              latexmk -pdf → PDF (with clean support)
-  `presets.pdflatex`           pdflatex → PDF (single pass, no latexmk)
-  `presets.tectonic`           tectonic → PDF (Rust-based LaTeX engine)
-  `presets.markdown`           pandoc → HTML (standalone, embedded)
-  `presets.github`             pandoc → HTML (GitHub-styled, `-f gfm` input)
-  `presets.asciidoctor`        asciidoctor → HTML (AsciiDoc with SSE reload)
-  `presets.quarto`             quarto render → HTML (scientific publishing)
-
-Enable presets with `preset_name = true`:
->lua
-    require('preview').setup({ typst = true, latex = true, github = true })
-<
-
-Override individual fields by passing a table instead of `true`:
->lua
-    require('preview').setup({
-      typst = { env = { TYPST_FONT_PATHS = '/usr/share/fonts' } },
-    })
-<
-
-==============================================================================
-COMMANDS                                              *preview.nvim-commands*
-
-:Preview [subcommand]                                             *:Preview*
-
-    Subcommands:~
-
-    `toggle`     Toggle auto-compile on save (default if omitted).
-    `compile`    One-shot compile of the current buffer.
-    `clean`      Run the provider's clean command.
-    `open`       Open the last compiled output without recompiling.
-    `status`     Echo compilation status (idle, compiling, watching).
-
-==============================================================================
-API                                                        *preview.nvim-api*
-
-preview.toggle({bufnr?})                                  *preview.toggle()*
-    Toggle auto-compile for the buffer. When enabled, the buffer is
-    immediately compiled and automatically recompiled on each save
-    (`BufWritePost`). Call again to stop.
-
-preview.compile({bufnr?})                                *preview.compile()*
-    One-shot compile the document in the given buffer (default: current).
-
-preview.stop({bufnr?})                                      *preview.stop()*
-    Kill the active compilation process for the buffer. Programmatic
-    escape hatch — not exposed as a subcommand.
-
-preview.clean({bufnr?})                                    *preview.clean()*
-    Run the provider's clean command for the buffer.
-
-preview.open({bufnr?})                                      *preview.open()*
-    Open the last compiled output for the buffer without recompiling.
-
-preview.status({bufnr?})                                  *preview.status()*
-    Returns a |preview.Status| table.
-
-preview.statusline({bufnr?})                          *preview.statusline()*
-    Returns a short status string for statusline integration:
-    `'compiling'`, `'watching'`, or `''` (idle).
-
-                                                          *preview.Status*
-Status fields:~
-
-  `compiling`    boolean    Whether compilation is active.
-  `watching`     boolean    Whether auto-compile is active.
-  `provider`     string?    Name of the active provider.
-  `output_file`  string?    Path to the output file.
-
-preview.get_config()                                  *preview.get_config()*
-    Returns the resolved |preview.Config|.
-
-==============================================================================
-EVENTS                                                  *preview.nvim-events*
-
-preview.nvim fires User autocmds with structured data:
-
-`PreviewCompileStarted`  Compilation began.
-                        data: `{ bufnr, provider }`
-
-`PreviewCompileSuccess`  Compilation succeeded (exit code 0).
-                        data: `{ bufnr, provider, output }`
-
-`PreviewCompileFailed`   Compilation failed (non-zero exit).
-                        data: `{ bufnr, provider, code, stderr }`
-
-Example:~
->lua
-    vim.api.nvim_create_autocmd('User', {
-      pattern = 'PreviewCompileSuccess',
-      callback = function(args)
-        local data = args.data
-        vim.notify('Compiled ' .. data.output .. ' with ' .. data.provider)
-      end,
-    })
-<
-
-==============================================================================
-HEALTH                                                  *preview.nvim-health*
-
-Run `:checkhealth preview` to verify:
-
-- Neovim version >= 0.11.0
-- Each configured provider's binary is executable
-- Each configured provider's opener binary (if any) is executable
-- Each configured provider's filetype mapping is valid
-
-==============================================================================
- vim:tw=78:ts=8:ft=help:norl:

doc/preview.txt

@@ -0,0 +1,276 @@
+*preview.txt*                    Async document compilation for Neovim
+
+Author:  Barrett Ruth <br.barrettruth@gmail.com>
+License: MIT
+
+==============================================================================
+INTRODUCTION                                                    *preview.nvim*
+
+preview.nvim is an extensible framework for compiling documents asynchronously
+in Neovim. It provides a unified interface for any compilation workflow —
+LaTeX, Typst, Markdown, or anything else with a CLI compiler.
+
+The plugin ships with opt-in presets for common tools (Typst, LaTeX, Pandoc,
+AsciiDoc, PlantUML, Mermaid, Quarto) and supports fully custom providers.
+See |preview-presets|.
+
+==============================================================================
+CONTENTS                                                   *preview-contents*
+
+  1. Introduction ............................................. |preview.nvim|
+  2. Requirements ..................................... |preview-requirements|
+  3. Install ............................................... |preview-install|
+  4. Configuration ........................................... |preview-config|
+  5. Presets ............................................... |preview-presets|
+  6. Commands ............................................. |preview-commands|
+  7. Lua API ................................................... |preview-api|
+  8. Events ............................................... |preview-events|
+  9. Health ............................................... |preview-health|
+
+==============================================================================
+REQUIREMENTS                                           *preview-requirements*
+
+- Neovim >= 0.11.0
+- A compiler binary for each configured provider (e.g. `typst`, `latexmk`)
+
+==============================================================================
+INSTALL                                                      *preview-install*
+
+Install with lazy.nvim: >lua
+    { 'barrettruth/preview.nvim' }
+<
+
+No `setup()` call is needed. The plugin loads automatically when
+|vim.g.preview| is set. See |preview-config|.
+
+==============================================================================
+CONFIGURATION                                                *preview-config*
+
+Configure by setting |vim.g.preview| to a table where keys are preset names
+or filetypes. For each key `k` with value `v` (excluding `debug`):
+
+  - If `k` is a preset name and `v` is `true`, the preset is registered
+    as-is under its filetype.
+  - If `k` is a preset name and `v` is a table, it is deep-merged with
+    the preset and registered under the preset's filetype.
+  - If `k` is not a preset name and `v` is a table, it is registered
+    directly as a custom provider keyed by filetype `k`.
+  - If `v` is `false`, the entry is skipped (no-op).
+
+See |preview-presets| for available preset names.
+
+                                                    *preview.ProviderConfig*
+Provider fields: ~
+
+  {cmd}              (string[])         Compiler command (required).
+
+  {args}             (string[]|function) Additional arguments. If a function,
+                                        receives a |preview.Context| and
+                                        returns a string[].
+
+  {cwd}              (string|function)  Working directory. If a function,
+                                        receives a |preview.Context|.
+                                        Default: git root or file directory.
+
+  {env}              (table)            Environment variables.
+
+  {output}           (string|function)  Output file path. If a function,
+                                        receives a |preview.Context|.
+
+  {error_parser}     (function)         Receives (output, |preview.Context|)
+                                        and returns vim.Diagnostic[].
+
+  {errors}           (false|'diagnostic'|'quickfix')
+                                        How parse errors are reported.
+                                        `false` suppresses error handling.
+                                        `'quickfix'` populates the quickfix
+                                        list and opens it.
+                                        Default: `'diagnostic'`.
+
+  {clean}            (string[]|function) Command to remove build artifacts.
+                                        If a function, receives a
+                                        |preview.Context|.
+
+  {open}             (boolean|string[]) Open the output file after the first
+                                        successful compilation in toggle/watch
+                                        mode. `true` uses |vim.ui.open()|. A
+                                        string[] is run as a command with the
+                                        output path appended. When a string[]
+                                        is used the viewer process is tracked
+                                        and sent SIGTERM when the buffer is
+                                        deleted. `true` and single-instance
+                                        apps (e.g. Chrome) do not support
+                                        auto-close.
+
+  {reload}           (boolean|string[]|function)
+                                        Reload the output after recompilation.
+                                        `true` uses a built-in SSE server for
+                                        HTML files. A string[] is run as a
+                                        command. If a function, receives a
+                                        |preview.Context| and returns a
+                                        string[].
+
+  {detach}           (boolean)          When `true`, the viewer process opened
+                                        via a string[] `open` command is not
+                                        sent SIGTERM when the buffer is
+                                        deleted. Has no effect when `open` is
+                                        `true`. Default: `false`.
+
+                                                        *preview.Context*
+Context fields: ~
+
+  {bufnr}   (integer)   Buffer number.
+  {file}    (string)    Absolute file path.
+  {root}    (string)    Project root (git root or file directory).
+  {ft}      (string)    Filetype.
+  {output}  (string?)   Resolved output file path (set after `output`
+                        is evaluated, available to `args` functions).
+
+Global options: ~
+
+  {debug}   (boolean|string) Enable debug logging. A string value is treated
+                             as a log file path. Default: `false`.
+
+Example enabling presets: >lua
+    vim.g.preview = { typst = true, latex = true, github = true }
+<
+
+Example overriding a preset field: >lua
+    vim.g.preview = {
+      typst = { open = { 'sioyek', '--new-instance' } },
+    }
+<
+
+Example overriding the output path (e.g. latexmk `$out_dir`): >lua
+    vim.g.preview = {
+      latex = {
+        output = function(ctx)
+          return 'build/' .. vim.fn.fnamemodify(ctx.file, ':t:r') .. '.pdf'
+        end,
+      },
+    }
+<
+
+Example with a fully custom provider (key is not a preset name): >lua
+    vim.g.preview = {
+      rst = {
+        cmd = { 'rst2html' },
+        args = function(ctx)
+          return { ctx.file }
+        end,
+        output = function(ctx)
+          return ctx.file:gsub('%.rst$', '.html')
+        end,
+      },
+    }
+<
+
+==============================================================================
+PRESETS                                                    *preview-presets*
+
+Built-in provider configurations. Enable with `preset_name = true` or
+override individual fields by passing a table instead: >lua
+    vim.g.preview = { typst = true, latex = true, github = true }
+<
+
+  `typst`              typst compile → PDF
+  `latex`              latexmk -pdf → PDF (with clean support)
+  `pdflatex`           pdflatex → PDF (single pass, no latexmk)
+  `tectonic`           tectonic → PDF (Rust-based LaTeX engine)
+  `markdown`           pandoc → HTML (standalone, embedded)
+  `github`             pandoc → HTML (GitHub-styled, `-f gfm` input)
+  `asciidoctor`        asciidoctor → HTML (AsciiDoc with SSE reload)
+  `plantuml`           plantuml → SVG (UML diagrams, `.puml`)
+  `mermaid`            mmdc → SVG (Mermaid diagrams, `.mmd`)
+  `quarto`             quarto render → HTML (scientific publishing)
+
+==============================================================================
+COMMANDS                                                  *preview-commands*
+
+:Preview [subcommand]                                             *:Preview*
+
+    Subcommands: ~
+
+    `toggle`     Toggle auto-compile on save (default if omitted).
+    `compile`    One-shot compile of the current buffer.
+    `clean`      Run the provider's clean command.
+    `open`       Open the last compiled output without recompiling.
+    `status`     Echo compilation status (idle, compiling, watching).
+
+==============================================================================
+LUA API                                                        *preview-api*
+
+preview.toggle({bufnr?})                                  *preview.toggle()*
+    Toggle auto-compile for the buffer. When enabled, the buffer is
+    immediately compiled and automatically recompiled on each save
+    (`BufWritePost`). Call again to stop.
+
+preview.compile({bufnr?})                                *preview.compile()*
+    One-shot compile the document in the given buffer (default: current).
+
+preview.stop({bufnr?})                                      *preview.stop()*
+    Kill the active compilation process for the buffer. Programmatic
+    escape hatch — not exposed as a subcommand.
+
+preview.clean({bufnr?})                                    *preview.clean()*
+    Run the provider's clean command for the buffer.
+
+preview.open({bufnr?})                                      *preview.open()*
+    Open the last compiled output for the buffer without recompiling.
+
+preview.status({bufnr?})                                  *preview.status()*
+    Returns a |preview.Status| table.
+
+preview.statusline({bufnr?})                          *preview.statusline()*
+    Returns a short status string for statusline integration:
+    `'compiling'`, `'watching'`, or `''` (idle).
+
+preview.get_config()                                  *preview.get_config()*
+    Returns the resolved |preview.Config|.
+
+                                                          *preview.Status*
+Status fields: ~
+
+  {compiling}    (boolean)   Whether compilation is active.
+  {watching}     (boolean)   Whether auto-compile is active.
+  {provider}     (string?)   Name of the active provider.
+  {output_file}  (string?)   Path to the output file.
+
+==============================================================================
+EVENTS                                                      *preview-events*
+
+preview.nvim fires User autocmds with structured data:
+
+`PreviewCompileStarted`  Compilation began.
+                        data: `{ bufnr, provider }`
+
+`PreviewCompileSuccess`  Compilation succeeded (exit code 0).
+                        data: `{ bufnr, provider, output }`
+
+`PreviewCompileFailed`   Compilation failed (non-zero exit).
+                        data: `{ bufnr, provider, code, stderr }`
+
+Example: >lua
+    vim.api.nvim_create_autocmd('User', {
+      pattern = 'PreviewCompileSuccess',
+      callback = function(args)
+        local data = args.data
+        vim.notify('Compiled ' .. data.output .. ' with ' .. data.provider)
+      end,
+    })
+<
+
+==============================================================================
+HEALTH                                                      *preview-health*
+
+Run |:checkhealth| preview to verify your setup: >vim
+    :checkhealth preview
+<
+
+Checks: ~
+- Neovim version >= 0.11.0
+- Each configured provider's binary is executable
+- Each configured provider's opener binary (if any) is executable
+
+==============================================================================
+ vim:tw=78:ts=8:ft=help:norl:

flake.nix

@@ -19,9 +19,9 @@
     {
       formatter = forEachSystem (pkgs: pkgs.nixfmt-tree);
 
-      devShells = forEachSystem (pkgs: {
+      devShells = forEachSystem (pkgs:
-        default = pkgs.mkShell {
+        let
-          packages = [
+          devTools = [
             (pkgs.luajit.withPackages (
               ps: with ps; [
                 busted
@@ -33,7 +33,23 @@
             pkgs.selene
             pkgs.lua-language-server
           ];
-        };
+        in
-      });
+        {
+          default = pkgs.mkShell {
+            packages = devTools;
+          };
+          presets = pkgs.mkShell {
+            packages = devTools ++ [
+              pkgs.typst
+              pkgs.texliveMedium
+              pkgs.tectonic
+              pkgs.pandoc
+              pkgs.asciidoctor
+              pkgs.quarto
+              pkgs.plantuml
+              pkgs.mermaid-cli
+            ];
+          };
+        });
     };
 }

lua/preview/compiler.lua

@@ -291,7 +291,9 @@ function M.compile(bufnr, name, provider, ctx, opts)
       callback = function()
         M.stop(bufnr)
         stop_open_watcher(bufnr)
-        close_viewer(bufnr)
+        if not provider.detach then
+          close_viewer(bufnr)
+        end
         last_output[bufnr] = nil
       end,
     })
@@ -404,7 +406,9 @@ function M.compile(bufnr, name, provider, ctx, opts)
     once = true,
     callback = function()
       M.stop(bufnr)
-      close_viewer(bufnr)
+      if not provider.detach then
+        close_viewer(bufnr)
+      end
       last_output[bufnr] = nil
     end,
   })
@@ -507,7 +511,9 @@ function M.toggle(bufnr, name, provider, ctx_builder)
     callback = function()
       M.unwatch(bufnr)
       stop_open_watcher(bufnr)
-      close_viewer(bufnr)
+      if not provider.detach then
+        close_viewer(bufnr)
+      end
       opened[bufnr] = nil
     end,
   })

lua/preview/init.lua

@@ -10,6 +10,7 @@
 ---@field clean? string[]|fun(ctx: preview.Context): string[]
 ---@field open? boolean|string[]
 ---@field reload? boolean|string[]|fun(ctx: preview.Context): string[]
+---@field detach? boolean
 
 ---@class preview.Config
 ---@field debug boolean|string
@@ -101,6 +102,13 @@ function M.setup(opts)
     end, 'false, "diagnostic", or "quickfix"')
     vim.validate(prefix .. '.open', provider.open, { 'boolean', 'table' }, true)
     vim.validate(prefix .. '.reload', provider.reload, { 'boolean', 'table', 'function' }, true)
+    vim.validate(prefix .. '.detach', provider.detach, 'boolean', true)
+  end
+
+  if providers['plantuml'] then
+    vim.filetype.add({
+      extension = { puml = 'plantuml', pu = 'plantuml' },
+    })
   end
 
   config = vim.tbl_deep_extend('force', default_config, {
@@ -246,4 +254,8 @@ M._test = {
   end,
 }
 
+if vim.g.preview then
+  M.setup(vim.g.preview)
+end
+
 return M

lua/preview/presets.lua

@@ -271,6 +271,68 @@ M.asciidoctor = {
   reload = true,
 }
 
+---@type preview.ProviderConfig
+M.plantuml = {
+  ft = 'plantuml',
+  cmd = { 'plantuml' },
+  args = function(ctx)
+    return { '-tsvg', ctx.file }
+  end,
+  output = function(ctx)
+    return (ctx.file:gsub('%.puml$', '.svg'))
+  end,
+  error_parser = function(output)
+    local diagnostics = {}
+    for line in output:gmatch('[^\r\n]+') do
+      local lnum = line:match('^Error line (%d+) in file:')
+      if lnum then
+        table.insert(diagnostics, {
+          lnum = tonumber(lnum) - 1,
+          col = 0,
+          message = line,
+          severity = vim.diagnostic.severity.ERROR,
+        })
+      end
+    end
+    return diagnostics
+  end,
+  clean = function(ctx)
+    return { 'rm', '-f', (ctx.file:gsub('%.puml$', '.svg')) }
+  end,
+  open = true,
+}
+
+---@type preview.ProviderConfig
+M.mermaid = {
+  ft = 'mermaid',
+  cmd = { 'mmdc' },
+  args = function(ctx)
+    return { '-i', ctx.file, '-o', ctx.output }
+  end,
+  output = function(ctx)
+    return (ctx.file:gsub('%.mmd$', '.svg'))
+  end,
+  error_parser = function(output)
+    local diagnostics = {}
+    for line in output:gmatch('[^\r\n]+') do
+      local lnum = line:match('^%s*Parse error on line (%d+)')
+      if lnum then
+        table.insert(diagnostics, {
+          lnum = tonumber(lnum) - 1,
+          col = 0,
+          message = line,
+          severity = vim.diagnostic.severity.ERROR,
+        })
+      end
+    end
+    return diagnostics
+  end,
+  clean = function(ctx)
+    return { 'rm', '-f', (ctx.file:gsub('%.mmd$', '.svg')) }
+  end,
+  open = true,
+}
+
 ---@type preview.ProviderConfig
 M.quarto = {
   ft = 'quarto',