diff --git a/README.md b/README.md
index 80a2650..3ffbc38 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ Typst, Markdown, etc.)—diagnostics included.
 
 - Async compilation via `vim.system()`
 - Built-in presets for Typst, LaTeX (latexmk, pdflatex, tectonic), Markdown,
-  GitHub-flavored Markdown, AsciiDoc, PlantUML, Mermaid, and Quarto
+  GitHub-flavored Markdown, AsciiDoc, and Quarto
 - Compiler errors via `vim.diagnostic` or quickfix
 - Previewer auto-close on buffer deletion
 
diff --git a/doc/preview.txt b/doc/preview.txt
index 383a8f5..0e54a62 100644
--- a/doc/preview.txt
+++ b/doc/preview.txt
@@ -11,7 +11,7 @@ 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.
+AsciiDoc, Quarto) and supports fully custom providers.
 See |preview-presets|.
 
 ==============================================================================
@@ -180,8 +180,6 @@ override individual fields by passing a table instead: >lua
   `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)
 
 ==============================================================================
diff --git a/flake.nix b/flake.nix
index 636f4d0..4ae4479 100644
--- a/flake.nix
+++ b/flake.nix
@@ -19,9 +19,9 @@
     {
       formatter = forEachSystem (pkgs: pkgs.nixfmt-tree);
 
-      devShells = forEachSystem (pkgs:
-        let
-          devTools = [
+      devShells = forEachSystem (pkgs: {
+        default = pkgs.mkShell {
+          packages = [
             (pkgs.luajit.withPackages (
               ps: with ps; [
                 busted
@@ -32,24 +32,9 @@
             pkgs.stylua
             pkgs.selene
             pkgs.lua-language-server
+            pkgs.plantuml
           ];
-        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
-            ];
-          };
-        });
+        };
+      });
     };
 }
diff --git a/lua/preview/init.lua b/lua/preview/init.lua
index 7cb982b..322b893 100644
--- a/lua/preview/init.lua
+++ b/lua/preview/init.lua
@@ -105,12 +105,6 @@ function M.setup(opts)
     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, {
     debug = debug,
     providers = providers,
diff --git a/lua/preview/presets.lua b/lua/preview/presets.lua
index 1b5333e..e7c51e3 100644
--- a/lua/preview/presets.lua
+++ b/lua/preview/presets.lua
@@ -302,37 +302,6 @@ M.plantuml = {
   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',