diff --git a/lua/diffs/highlight.lua b/lua/diffs/highlight.lua
index 836a9f4..0c226ae 100644
--- a/lua/diffs/highlight.lua
+++ b/lua/diffs/highlight.lua
@@ -245,7 +245,7 @@ local function highlight_vim_syntax(
   pcall(vim.api.nvim_buf_delete, scratch, { force = true })
 
   local hunk_line_count = #hunk.lines
-  local col_off = (hunk.prefix_width or 1) - 1
+  local col_off = (hunk.prefix_width or 1) + (hunk.quote_width or 0) - 1
   local extmark_count = 0
   for _, span in ipairs(spans) do
     local adj = span.line - leading_offset
@@ -273,6 +273,7 @@ end
 function M.highlight_hunk(bufnr, ns, hunk, opts)
   local p = opts.highlights.priorities
   local pw = hunk.prefix_width or 1
+  local qw = hunk.quote_width or 0
   local use_ts = hunk.lang and opts.highlights.treesitter.enabled
   local use_vim = not use_ts and hunk.ft and opts.highlights.vim.enabled
 
@@ -329,9 +330,9 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     end
 
     extmark_count =
-      highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, pw, covered_lines, p)
+      highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, pw + qw, covered_lines, p)
     extmark_count = extmark_count
-      + highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, pw, covered_lines, p)
+      + highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, pw + qw, covered_lines, p)
 
     if hunk.header_context and hunk.header_context_col then
       local header_extmarks = highlight_text(
@@ -370,11 +371,11 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       header_map[i] = hunk.header_start_line - 1 + i
     end
     extmark_count = extmark_count
-      + highlight_treesitter(bufnr, ns, hunk.header_lines, 'diff', header_map, 0, nil, p, pw > 1)
+      + highlight_treesitter(bufnr, ns, hunk.header_lines, 'diff', header_map, qw, nil, p, qw > 0 or pw > 1)
   end
 
   local at_raw_line
-  if pw > 1 and opts.highlights.treesitter.enabled then
+  if (qw > 0 or pw > 1) and opts.highlights.treesitter.enabled then
     local at_buf_line = hunk.start_line - 1
     at_raw_line = vim.api.nvim_buf_get_lines(bufnr, at_buf_line, at_buf_line + 1, false)[1]
   end
@@ -420,7 +421,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
   end
 
   if
-    pw > 1
+    (qw > 0 or pw > 1)
     and hunk.header_start_line
     and hunk.header_lines
     and #hunk.header_lines > 0
@@ -429,35 +430,37 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     for i = 0, #hunk.header_lines - 1 do
       local buf_line = hunk.header_start_line - 1 + i
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-        end_col = #hunk.header_lines[i + 1],
+        end_col = #hunk.header_lines[i + 1] + qw,
         hl_group = 'DiffsClear',
         priority = p.clear,
       })
 
-      local hline = hunk.header_lines[i + 1]
-      if hline:match('^index ') then
-        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-          end_col = 5,
-          hl_group = '@keyword.diff',
-          priority = p.syntax,
-        })
-        local dot_pos = hline:find('%.%.', 1, false)
-        if dot_pos then
-          local rest = hline:sub(dot_pos + 2)
-          local hash = rest:match('^(%x+)')
-          if hash then
-            pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, dot_pos + 1, {
-              end_col = dot_pos + 1 + #hash,
-              hl_group = '@constant.diff',
-              priority = p.syntax,
-            })
+      if pw > 1 then
+        local hline = hunk.header_lines[i + 1]
+        if hline:match('^index ') then
+          pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, qw, {
+            end_col = 5 + qw,
+            hl_group = '@keyword.diff',
+            priority = p.syntax,
+          })
+          local dot_pos = hline:find('%.%.', 1, false)
+          if dot_pos then
+            local rest = hline:sub(dot_pos + 2)
+            local hash = rest:match('^(%x+)')
+            if hash then
+              pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, dot_pos + 1 + qw, {
+                end_col = dot_pos + 1 + #hash + qw,
+                hl_group = '@constant.diff',
+                priority = p.syntax,
+              })
+            end
           end
         end
       end
     end
   end
 
-  if pw > 1 and at_raw_line then
+  if (qw > 0 or pw > 1) and at_raw_line then
     local at_buf_line = hunk.start_line - 1
     pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, at_buf_line, 0, {
       end_col = #at_raw_line,
@@ -465,7 +468,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       priority = p.clear,
     })
     if opts.highlights.treesitter.enabled then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, at_buf_line, 0, {
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, at_buf_line, qw, {
         end_col = #at_raw_line,
         hl_group = '@attribute.diff',
         priority = p.syntax,
@@ -482,9 +485,16 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     })
   end
 
+  local raw_body_lines
+  if qw > 0 then
+    raw_body_lines =
+      vim.api.nvim_buf_get_lines(bufnr, hunk.start_line, hunk.start_line + #hunk.lines, false)
+  end
+
   for i, line in ipairs(hunk.lines) do
     local buf_line = hunk.start_line + i - 1
     local line_len = #line
+    local raw_len = raw_body_lines and #raw_body_lines[i] or nil
     local prefix = line:sub(1, pw)
     local has_add = prefix:find('+', 1, true) ~= nil
     local has_del = prefix:find('-', 1, true) ~= nil
@@ -505,22 +515,30 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       if opts.hide_prefix then
         local virt_hl = (opts.highlights.background and line_hl) or nil
         pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-          virt_text = { { string.rep(' ', pw), virt_hl } },
+          virt_text = { { string.rep(' ', pw + qw), virt_hl } },
           virt_text_pos = 'overlay',
         })
       end
 
-      if pw > 1 then
+      if qw > 0 or pw > 1 then
+        local prefix_end = pw + qw
+        if raw_len and prefix_end > raw_len then
+          prefix_end = raw_len
+        end
         pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-          end_col = pw,
+          end_col = prefix_end,
           hl_group = 'DiffsClear',
           priority = p.clear,
         })
         for ci = 0, pw - 1 do
           local ch = line:sub(ci + 1, ci + 1)
           if ch == '+' or ch == '-' then
-            pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, ci, {
-              end_col = ci + 1,
+            local char_col = ci + qw
+            if raw_len and char_col >= raw_len then
+              break
+            end
+            pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, char_col, {
+              end_col = char_col + 1,
               hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
               priority = p.syntax,
             })
@@ -537,8 +555,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       end
 
       if is_marker and line_len > pw then
-        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
-          end_col = line_len,
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw + qw, {
+          end_col = line_len + qw,
           hl_group = 'DiffsConflictMarker',
           priority = p.char_bg,
         })
@@ -556,8 +574,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
             char_hl,
             line:sub(span.col_start + 1, span.col_end)
           )
-          local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
-            end_col = span.col_end,
+          local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start + qw, {
+            end_col = span.col_end + qw,
             hl_group = char_hl,
             priority = p.char_bg,
           })
@@ -570,8 +588,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     end
 
     if line_len > pw and covered_lines[buf_line] then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
-        end_col = line_len,
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw + qw, {
+        end_col = line_len + qw,
         hl_group = 'DiffsClear',
         priority = p.clear,
       })
diff --git a/lua/diffs/parser.lua b/lua/diffs/parser.lua
index a32e563..c512ac5 100644
--- a/lua/diffs/parser.lua
+++ b/lua/diffs/parser.lua
@@ -13,6 +13,7 @@
 ---@field file_new_start integer?
 ---@field file_new_count integer?
 ---@field prefix_width integer
+---@field quote_width integer
 ---@field repo_root string?
 
 local M = {}
@@ -135,6 +136,17 @@ function M.parse_buffer(bufnr)
   local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
   local repo_root = get_repo_root(bufnr)
 
+  local quote_prefix = nil
+  local quote_width = 0
+  for _, l in ipairs(lines) do
+    local qp = l:match('^(>+ )diff %-%-') or l:match('^(>+ )@@ %-')
+    if qp then
+      quote_prefix = qp
+      quote_width = #qp
+      break
+    end
+  end
+
   ---@type diffs.Hunk[]
   local hunks = {}
 
@@ -172,6 +184,7 @@ function M.parse_buffer(bufnr)
   local old_remaining = nil
   ---@type integer?
   local new_remaining = nil
+  local current_quote_width = 0
 
   local function flush_hunk()
     if hunk_start and #hunk_lines > 0 then
@@ -184,6 +197,7 @@ function M.parse_buffer(bufnr)
         header_context_col = hunk_header_context_col,
         lines = hunk_lines,
         prefix_width = hunk_prefix_width,
+        quote_width = current_quote_width,
         file_old_start = file_old_start,
         file_old_count = file_old_count,
         file_new_start = file_new_start,
@@ -209,19 +223,29 @@ function M.parse_buffer(bufnr)
   end
 
   for i, line in ipairs(lines) do
-    local diff_git_file = line:match('^diff %-%-git a/.+ b/(.+)$')
-      or line:match('^diff %-%-combined (.+)$')
-      or line:match('^diff %-%-cc (.+)$')
-    local neogit_file = line:match('^modified%s+(.+)$')
-      or (not line:match('^new file mode') and line:match('^new file%s+(.+)$'))
-      or (not line:match('^deleted file mode') and line:match('^deleted%s+(.+)$'))
-      or line:match('^renamed%s+(.+)$')
-      or line:match('^copied%s+(.+)$')
-    local bare_file = not hunk_start and line:match('^([^%s]+%.[^%s]+)$')
-    local filename = line:match('^[MADRCU%?!]%s+(.+)$') or diff_git_file or neogit_file or bare_file
+    local logical = line
+    if quote_prefix then
+      if line:sub(1, quote_width) == quote_prefix then
+        logical = line:sub(quote_width + 1)
+      elseif line:match('^>+$') then
+        logical = ''
+      end
+    end
+
+    local diff_git_file = logical:match('^diff %-%-git a/.+ b/(.+)$')
+      or logical:match('^diff %-%-combined (.+)$')
+      or logical:match('^diff %-%-cc (.+)$')
+    local neogit_file = logical:match('^modified%s+(.+)$')
+      or (not logical:match('^new file mode') and logical:match('^new file%s+(.+)$'))
+      or (not logical:match('^deleted file mode') and logical:match('^deleted%s+(.+)$'))
+      or logical:match('^renamed%s+(.+)$')
+      or logical:match('^copied%s+(.+)$')
+    local bare_file = not hunk_start and logical:match('^([^%s]+%.[^%s]+)$')
+    local filename = logical:match('^[MADRCU%?!]%s+(.+)$') or diff_git_file or neogit_file or bare_file
     if filename then
       flush_hunk()
       current_filename = filename
+      current_quote_width = (logical ~= line) and quote_width or 0
       local cache_key = (repo_root or '') .. '\0' .. filename
       local cached = ft_lang_cache[cache_key]
       if cached then
@@ -243,13 +267,13 @@ function M.parse_buffer(bufnr)
       hunk_prefix_width = 1
       header_start = i
       header_lines = {}
-    elseif line:match('^@@+') then
+    elseif logical:match('^@@+') then
       flush_hunk()
       hunk_start = i
-      local at_prefix = line:match('^(@@+)')
+      local at_prefix = logical:match('^(@@+)')
       hunk_prefix_width = #at_prefix - 1
       if #at_prefix == 2 then
-        local hs, hc, hs2, hc2 = line:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
+        local hs, hc, hs2, hc2 = logical:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
         if hs then
           file_old_start = tonumber(hs)
           file_old_count = tonumber(hc) or 1
@@ -259,31 +283,31 @@ function M.parse_buffer(bufnr)
           new_remaining = file_new_count
         end
       else
-        local hs, hc = line:match('%-(%d+),?(%d*)')
+        local hs, hc = logical:match('%-(%d+),?(%d*)')
         if hs then
           file_old_start = tonumber(hs)
           file_old_count = tonumber(hc) or 1
           old_remaining = file_old_count
         end
-        local hs2, hc2 = line:match('%+(%d+),?(%d*) @@')
+        local hs2, hc2 = logical:match('%+(%d+),?(%d*) @@')
         if hs2 then
           file_new_start = tonumber(hs2)
           file_new_count = tonumber(hc2) or 1
           new_remaining = file_new_count
         end
       end
-      local at_end, context = line:match('^(@@+.-@@+%s*)(.*)')
+      local at_end, context = logical:match('^(@@+.-@@+%s*)(.*)')
       if context and context ~= '' then
         hunk_header_context = context
-        hunk_header_context_col = #at_end
+        hunk_header_context_col = #at_end + current_quote_width
       end
       if hunk_count then
         hunk_count = hunk_count + 1
       end
     elseif hunk_start then
-      local prefix = line:sub(1, 1)
+      local prefix = logical:sub(1, 1)
       if prefix == ' ' or prefix == '+' or prefix == '-' then
-        table.insert(hunk_lines, line)
+        table.insert(hunk_lines, logical)
         if old_remaining and (prefix == ' ' or prefix == '-') then
           old_remaining = old_remaining - 1
         end
@@ -291,7 +315,7 @@ function M.parse_buffer(bufnr)
           new_remaining = new_remaining - 1
         end
       elseif
-        line == ''
+        logical == ''
         and old_remaining
         and old_remaining > 0
         and new_remaining
@@ -301,11 +325,11 @@ function M.parse_buffer(bufnr)
         old_remaining = old_remaining - 1
         new_remaining = new_remaining - 1
       elseif
-        line == ''
-        or line:match('^[MADRC%?!]%s+')
-        or line:match('^diff ')
-        or line:match('^index ')
-        or line:match('^Binary ')
+        logical == ''
+        or logical:match('^[MADRC%?!]%s+')
+        or logical:match('^diff ')
+        or logical:match('^index ')
+        or logical:match('^Binary ')
       then
         flush_hunk()
         current_filename = nil
@@ -315,7 +339,7 @@ function M.parse_buffer(bufnr)
       end
     end
     if header_start and not hunk_start then
-      table.insert(header_lines, line)
+      table.insert(header_lines, logical)
     end
   end
 
diff --git a/spec/email_quote_spec.lua b/spec/email_quote_spec.lua
new file mode 100644
index 0000000..afd0206
--- /dev/null
+++ b/spec/email_quote_spec.lua
@@ -0,0 +1,472 @@
+require('spec.helpers')
+local parser = require('diffs.parser')
+local highlight = require('diffs.highlight')
+
+describe('email-quoted diffs', function()
+  local function create_buffer(lines)
+    local bufnr = vim.api.nvim_create_buf(false, true)
+    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+    return bufnr
+  end
+
+  local function delete_buffer(bufnr)
+    if vim.api.nvim_buf_is_valid(bufnr) then
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end
+  end
+
+  describe('parser', function()
+    it('parses a fully email-quoted unified diff', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.py',
+        '> +++ b/foo.py',
+        '> @@ -0,0 +1,3 @@',
+        '> +from typing import Annotated, final',
+        '> +',
+        '> +class Foo:',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('foo.py', hunks[1].filename)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal('+from typing import Annotated, final', hunks[1].lines[1])
+      assert.are.equal(2, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('parses a quoted diff embedded in an email reply', function()
+      local bufnr = create_buffer({
+        'Looks good, one nit:',
+        '',
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -0,0 +1,3 @@',
+        '> +from typing import Annotated, final',
+        '> +',
+        '> +class Foo:',
+        '',
+        'Maybe rename Foo to Bar?',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('foo.py', hunks[1].filename)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal(2, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('sets quote_width = 0 on normal (unquoted) diffs', function()
+      local bufnr = create_buffer({
+        'diff --git a/bar.lua b/bar.lua',
+        '@@ -1,2 +1,2 @@',
+        '-old_line',
+        '+new_line',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(0, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('treats bare > lines as empty quoted lines', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -1,3 +1,3 @@',
+        '> -old',
+        '>',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal('-old', hunks[1].lines[1])
+      assert.are.equal(' ', hunks[1].lines[2])
+      assert.are.equal('+new', hunks[1].lines[3])
+      delete_buffer(bufnr)
+    end)
+
+    it('handles deeply nested quotes', function()
+      local bufnr = create_buffer({
+        '>> diff --git a/foo.py b/foo.py',
+        '>> @@ -0,0 +1,2 @@',
+        '>> +line1',
+        '>> +line2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(3, hunks[1].quote_width)
+      assert.are.equal('+line1', hunks[1].lines[1])
+      delete_buffer(bufnr)
+    end)
+
+    it('adjusts header_context_col for quote width', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -1,2 +1,2 @@ def hello():',
+        '> -old',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('def hello():', hunks[1].header_context)
+      assert.are.equal(#'@@ -1,2 +1,2 @@ ' + 2, hunks[1].header_context_col)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not false-positive on prose containing > diff', function()
+      local bufnr = create_buffer({
+        '> diff between approaches is small',
+        '> I think we should go with option A',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(0, #hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('stores header lines stripped of quote prefix', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.lua b/foo.lua',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.lua',
+        '> +++ b/foo.lua',
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.is_not_nil(hunks[1].header_lines)
+      for _, hline in ipairs(hunks[1].header_lines) do
+        assert.is_nil(hline:match('^> '))
+      end
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('highlight', function()
+    local ns
+
+    before_each(function()
+      ns = vim.api.nvim_create_namespace('diffs_email_test')
+      vim.api.nvim_set_hl(0, 'DiffsClear', { fg = 0xc0c0c0, bg = 0x1e1e1e })
+      vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = 0x1a3a1a })
+      vim.api.nvim_set_hl(0, 'DiffsDelete', { bg = 0x3a1a1a })
+      vim.api.nvim_set_hl(0, 'DiffsConflictMarker', { fg = 0x808080, bold = true })
+    end)
+
+    local function get_extmarks(bufnr)
+      return vim.api.nvim_buf_get_extmarks(bufnr, ns, 0, -1, { details = true })
+    end
+
+    local function default_opts(overrides)
+      local opts = {
+        hide_prefix = false,
+        highlights = {
+          background = true,
+          gutter = false,
+          context = { enabled = false, lines = 0 },
+          treesitter = {
+            enabled = true,
+            max_lines = 500,
+          },
+          vim = {
+            enabled = false,
+            max_lines = 200,
+          },
+          intra = {
+            enabled = false,
+            algorithm = 'default',
+            max_lines = 500,
+          },
+          priorities = {
+            clear = 198,
+            syntax = 199,
+            line_bg = 200,
+            char_bg = 201,
+          },
+        },
+      }
+      if overrides then
+        if overrides.highlights then
+          opts.highlights = vim.tbl_deep_extend('force', opts.highlights, overrides.highlights)
+        end
+        for k, v in pairs(overrides) do
+          if k ~= 'highlights' then
+            opts[k] = v
+          end
+        end
+      end
+      return opts
+    end
+
+    it('applies DiffsClear on email-quoted header lines covering full buffer width', function()
+      local buf_lines = {
+        '> diff --git a/foo.lua b/foo.lua',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.lua',
+        '> +++ b/foo.lua',
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      }
+      local bufnr = create_buffer(buf_lines)
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 5,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+        header_start_line = 1,
+        header_lines = {
+          'diff --git a/foo.lua b/foo.lua',
+          'index abc1234..def5678 100644',
+          '--- a/foo.lua',
+          '+++ b/foo.lua',
+        },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local header_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and mark[2] < 4 then
+          table.insert(header_clears, { row = mark[2], col = mark[3], end_col = d.end_col })
+        end
+      end
+      assert.is_true(#header_clears > 0)
+      for _, c in ipairs(header_clears) do
+        assert.are.equal(0, c.col)
+        local buf_line_len = #buf_lines[c.row + 1]
+        assert.are.equal(buf_line_len, c.end_col)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('applies body prefix DiffsClear covering [0, pw+qw)', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local prefix_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and d.end_col == 3 and mark[3] == 0 then
+          table.insert(prefix_clears, { row = mark[2] })
+        end
+      end
+      assert.are.equal(2, #prefix_clears)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('clamps body prefix DiffsClear on bare > lines (1-byte buffer line)', function()
+      local bufnr = create_buffer({
+        '> @@ -1,3 +1,3 @@',
+        '> -old',
+        '>',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        ft = 'lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '-old', ' ', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local bare_line_row = 2
+      local bare_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and mark[2] == bare_line_row and mark[3] == 0 then
+          table.insert(bare_clears, { end_col = d.end_col })
+        end
+      end
+      assert.are.equal(1, #bare_clears)
+      assert.are.equal(1, bare_clears[1].end_col)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('applies per-char @diff.plus/@diff.minus at ci + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local diff_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.hl_group == '@diff.plus' or d.hl_group == '@diff.minus') then
+          table.insert(diff_marks, { row = mark[2], col = mark[3], end_col = d.end_col, hl = d.hl_group })
+        end
+      end
+      assert.is_true(#diff_marks >= 2)
+      for _, dm in ipairs(diff_marks) do
+        assert.are.equal(2, dm.col)
+        assert.are.equal(3, dm.end_col)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('offsets treesitter extmarks by pw + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,2 @@',
+        '>  local x = 1',
+        '> +local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local ts_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group and d.hl_group:match('^@.*%.lua$') then
+          table.insert(ts_marks, { row = mark[2], col = mark[3] })
+        end
+      end
+      assert.is_true(#ts_marks > 0)
+      for _, tm in ipairs(ts_marks) do
+        assert.is_true(tm.col >= 3)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('offsets intra-line char span extmarks by qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -hello world',
+        '> +hello earth',
+      })
+
+      local hunk = {
+        filename = 'test.txt',
+        ft = nil,
+        lang = nil,
+        start_line = 1,
+        lines = { '-hello world', '+hello earth' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({ highlights = { intra = { enabled = true, algorithm = 'default', max_lines = 500 } } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      local char_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.hl_group == 'DiffsAddText' or d.hl_group == 'DiffsDeleteText') then
+          table.insert(char_marks, { row = mark[2], col = mark[3], end_col = d.end_col })
+        end
+      end
+      if #char_marks > 0 then
+        for _, cm in ipairs(char_marks) do
+          assert.is_true(cm.col >= 2)
+        end
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('does not produce duplicate extmarks with syntax_only + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,2 @@',
+        '>  local x = 1',
+        '> +local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts({ syntax_only = true }))
+
+      local extmarks = get_extmarks(bufnr)
+      local line_bg_count = 0
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.line_hl_group == 'DiffsAdd' then
+          line_bg_count = line_bg_count + 1
+        end
+      end
+      assert.are.equal(1, line_bg_count)
+
+      delete_buffer(bufnr)
+    end)
+  end)
+end)