diff --git a/news/changelog-1.7.md b/news/changelog-1.7.md
index 64c7451427..2d11fa630c 100644
--- a/news/changelog-1.7.md
+++ b/news/changelog-1.7.md
@@ -9,3 +9,11 @@ All changes included in 1.7:
 ## `quarto check`
 
 - ([#11608](https://github.com/quarto-dev/quarto-cli/pull/11608)): Do not issue error message when calling `quarto check info`.
+
+## Lua Filters and extensions
+
+- ([#11526](https://github.com/quarto-dev/quarto-cli/pull/11526)):
+  General improvements to the style and robustness of Quarto's Lua code.
+  This also provides a new public function `quarto.utils.is_empty_node`
+  that allows to check whether a node is empty, i.e., whether it's an
+  empty list, has no child nodes, and contains no text.
diff --git a/src/resources/filters/ast/customnodes.lua b/src/resources/filters/ast/customnodes.lua
index a36bf6a3a0..ca61ebc39b 100644
--- a/src/resources/filters/ast/customnodes.lua
+++ b/src/resources/filters/ast/customnodes.lua
@@ -337,13 +337,7 @@ _quarto.ast = {
         end
         local node = node_accessor(table)
         local t = pandoc.utils.type(value)
-        -- FIXME this is broken; that can only be "Block", "Inline", etc
-        if t == "Div" or t == "Span" then
-          local custom_data, t, kind = _quarto.ast.resolve_custom_data(value)
-          if custom_data ~= nil then
-            value = custom_data
-          end
-        end
+        quarto_assert(t ~= 'Div' and t ~= 'Span', "")
         if index > #node.content then
           _quarto.ast.grow_scaffold(node, index)
         end
diff --git a/src/resources/filters/common/error.lua b/src/resources/filters/common/error.lua
index 930af18b78..e27f9c0893 100644
--- a/src/resources/filters/common/error.lua
+++ b/src/resources/filters/common/error.lua
@@ -15,8 +15,15 @@ function fail(message, level)
   end
 end
 
-function internal_error()
-  fail("This is an internal error. Please file a bug report at https://github.com/quarto-dev/quarto-cli/", 5)
+function internal_error(msg, level)
+  fail((msg and (msg .. '\n') or '') ..
+    "This is an internal error. Please file a bug report at https://github.com/quarto-dev/quarto-cli/", level or 5)
+end
+
+function quarto_assert (test, msg, level)
+  if not test then
+    internal_error(msg, level or 6)
+  end
 end
 
 function currentFile() 
diff --git a/src/resources/filters/common/log.lua b/src/resources/filters/common/log.lua
index 584358be1f..67a736bbe9 100644
--- a/src/resources/filters/common/log.lua
+++ b/src/resources/filters/common/log.lua
@@ -5,6 +5,10 @@
 -- could write to named filed (e.g. <docname>.filter.log) and client could read warnings and delete (also delete before run)
 -- always append b/c multiple filters
 
+--- The default, built-in error function.
+-- The `error` global is redefined below.
+local builtin_error_function = error
+
 -- luacov: disable
 local function caller_info(offset)
   offset = offset or 3
@@ -27,6 +31,6 @@ end
 function fatal(message, offset)
   io.stderr:write(lunacolors.red("FATAL (" .. caller_info(offset) .. ") " ..message .. "\n"))
   -- TODO write stack trace into log, and then exit.
-  crash_with_stack_trace()  
+  builtin_error_function('FATAL QUARTO ERROR', offset)
 end
--- luacov: enable
\ No newline at end of file
+-- luacov: enable
diff --git a/src/resources/filters/common/pandoc.lua b/src/resources/filters/common/pandoc.lua
index d4b69ae859..e52a0de9cd 100644
--- a/src/resources/filters/common/pandoc.lua
+++ b/src/resources/filters/common/pandoc.lua
@@ -84,12 +84,14 @@ function inlinesToString(inlines)
   return pandoc.utils.stringify(pandoc.Span(inlines))
 end
 
+local InlinesMT = getmetatable(pandoc.Inlines{})
+
 -- lua string to pandoc inlines
 function stringToInlines(str)
   if str then
-    return pandoc.Inlines({pandoc.Str(str)})
+    return setmetatable({pandoc.Str(str)}, InlinesMT)
   else
-    return pandoc.Inlines({})
+    return setmetatable({}, InlinesMT)
   end
 end
 
@@ -98,27 +100,24 @@ end
 function markdownToInlines(str)
   if str then
     local doc = pandoc.read(str)
-    if #doc.blocks == 0 then
-      return pandoc.List({})
-    else
-      return doc.blocks[1].content
-    end
+    return pandoc.utils.blocks_to_inlines(doc.blocks)
   else
-    return pandoc.List()
+    return setmetatable({}, InlinesMT)
   end
 end
 
+
 function stripTrailingSpace(inlines)
-  -- we always convert to pandoc.List to ensure a uniform
+  -- we always convert to pandoc.Inlines to ensure a uniform
   -- return type (and its associated methods)
   if #inlines > 0 then
     if inlines[#inlines].t == "Space" then
-      return pandoc.List(tslice(inlines, 1, #inlines - 1))
+      return setmetatable(tslice(inlines, 1, #inlines - 1), InlinesMT)
     else
-      return pandoc.List(inlines)
+      return setmetatable(inlines, InlinesMT)
     end
   else
-    return pandoc.List(inlines)
+    return setmetatable(inlines, InlinesMT)
   end
 end
 
diff --git a/src/resources/pandoc/datadir/_utils.lua b/src/resources/pandoc/datadir/_utils.lua
index e2d986646e..2c9bd6d17f 100644
--- a/src/resources/pandoc/datadir/_utils.lua
+++ b/src/resources/pandoc/datadir/_utils.lua
@@ -265,59 +265,75 @@ local function get_type(v)
   return pandoc_type
 end
 
-local function as_inlines(v)
-  if v == nil then
-    return pandoc.Inlines({})
-  end
-  local t = pandoc.utils.type(v)
-  if t == "Inlines" then
-    ---@cast v pandoc.Inlines
-    return v
-  elseif t == "Blocks" then
-    return pandoc.utils.blocks_to_inlines(v)
-  elseif t == "Inline" then
-    return pandoc.Inlines({v})
-  elseif t == "Block" then
-    return pandoc.utils.blocks_to_inlines({v})
-  end
+--- Blocks metatable
+local BlocksMT = getmetatable(pandoc.Blocks{})
+--- Inlines metatable
+local InlinesMT = getmetatable(pandoc.Inlines{})
 
-  if type(v) == "table" then
-    local result = pandoc.Inlines({})
-    for i, v in ipairs(v) do
-      tappend(result, as_inlines(v))
+--- Turns the given object into a `Inlines` list.
+--
+-- Works mostly like `pandoc.Inlines`, but doesn't a do a full
+-- unmarshal/marshal roundtrip. This buys performance, at the cost of
+-- less thorough type checks.
+--
+-- NOTE: The input object might be modified *destructively*!
+local function as_inlines(obj)
+  local pt = pandoc.utils.type(obj)
+  if pt == 'Inlines' then
+    return obj
+  elseif pt == "Inline" then
+    -- Faster than calling pandoc.Inlines
+    return setmetatable({obj}, InlinesMT)
+  elseif pt == 'List' or pt == 'table' then
+    if obj[1] and pandoc.utils.type(obj[1]) == 'Block' then
+      return pandoc.utils.blocks_to_inlines(obj)
     end
-    return result
+    -- Faster than calling pandoc.Inlines
+    return setmetatable(obj, InlinesMT)
+  elseif pt == "Block" then
+    return pandoc.utils.blocks_to_inlines({obj})
+  elseif pt == "Blocks" then
+    return pandoc.utils.blocks_to_inlines(obj)
+  else
+    return pandoc.Inlines(obj or {})
   end
-
-  -- luacov: disable
-  fatal("as_inlines: invalid type " .. t)
-  return pandoc.Inlines({})
-  -- luacov: enable
 end
 
-local function as_blocks(v)
-  if v == nil then
-    return pandoc.Blocks({})
-  end
-  local t = pandoc.utils.type(v)
-  if t == "Blocks" then
-    return v
-  elseif t == "Inlines" then
-    return pandoc.Blocks({pandoc.Plain(v)})
-  elseif t == "Block" then
-    return pandoc.Blocks({v})
-  elseif t == "Inline" then
-    return pandoc.Blocks({pandoc.Plain(v)})
-  end
-
-  if type(v) == "table" then
-    return pandoc.Blocks(v)
+--- Turns the given object into a `Blocks` list.
+--
+-- Works mostly like `pandoc.Blocks`, but doesn't a do a full
+-- unmarshal/marshal roundtrip. This buys performance, at the cost of
+-- less thorough type checks.
+--
+-- NOTE: The input object might be modified *destructively*!
+--
+-- This might need some benchmarking.
+local function as_blocks(obj)
+  local pt = pandoc.utils.type(obj)
+  if pt == 'Blocks' then
+    return obj
+  elseif pt == 'Block' then
+    -- Assigning a metatable directly is faster than calling
+    -- `pandoc.Blocks`.
+    return setmetatable({obj}, BlocksMT)
+  elseif pt == 'Inline' then
+    return setmetatable({pandoc.Plain{obj}}, BlocksMT)
+  elseif pt == 'Inlines' then
+    if next(obj) then
+      return setmetatable({pandoc.Plain(obj)}, BlocksMT)
+    end
+    return setmetatable({}, BlocksMT)
+  elseif pt == 'List' or (pt == 'table' and obj[1]) then
+    if pandoc.utils.type(obj[1]) == 'Inline' then
+      obj = {pandoc.Plain(obj)}
+    end
+    return setmetatable(obj, BlocksMT)
+  elseif (pt == 'table' and obj.long) or pt == 'Caption' then
+    -- Looks like a Caption
+    return as_blocks(obj.long)
+  else
+    return pandoc.Blocks(obj or {})
   end
-
-  -- luacov: disable
-  fatal("as_blocks: invalid type " .. t)
-  return pandoc.Blocks({})
-  -- luacov: enable
 end
 
 local function match_fun(reset, ...)
@@ -557,6 +573,32 @@ local function match(...)
   return match_fun(reset, table.unpack(result))
 end
 
+--- Returns `true` iff the given AST node is empty.
+-- A node is considered "empty" if it's an empty list, table, or a node
+-- without any text or nested AST nodes.
+local function is_empty_node (node)
+  if not node then
+    return true
+  elseif type(node) == 'table' then
+    -- tables are considered empty if they don't have any fields.
+    return not next(node)
+  elseif node.content then
+    return not next(node.content)
+  elseif node.caption then
+    -- looks like an image, figure, or table
+    if node.caption.long then
+      return not next(node.caption.long)
+    end
+    return not next(node.caption)
+  elseif node.text then
+    -- looks like a code node or text node
+    return node.text ~= ''
+  else
+    -- Not sure what this is, but it's probably not empty.
+    return false
+  end
+end
+
 return {
   dump = dump,
   type = get_type,
@@ -567,6 +609,7 @@ return {
   },
   as_inlines = as_inlines,
   as_blocks = as_blocks,
+  is_empty_node = is_empty_node,
   match = match,
   add_to_blocks = function(blocks, block)
     if pandoc.utils.type(blocks) ~= "Blocks" then
diff --git a/src/resources/pandoc/datadir/init.lua b/src/resources/pandoc/datadir/init.lua
index 0cde1ccced..1dc45ed14b 100644
--- a/src/resources/pandoc/datadir/init.lua
+++ b/src/resources/pandoc/datadir/init.lua
@@ -2085,6 +2085,7 @@ quarto = {
     resolve_path_relative_to_document = resolvePath,
     as_inlines = utils.as_inlines,
     as_blocks = utils.as_blocks,
+    is_empty_node = utils.is_empty_node,
     string_to_blocks = utils.string_to_blocks,
     string_to_inlines = utils.string_to_inlines,
     render = utils.render,