doc: add plug mappings for merge conflict resolution

feat(conflict): detect and resolve inline merge conflict markers

README.md

@@ -18,7 +18,9 @@ syntax highlighting.
 - Vim syntax fallback for languages without a treesitter parser
 - Hunk header context highlighting (`@@ ... @@ function foo()`)
 - Character-level (intra-line) diff highlighting for changed characters
-- Configurable debouncing, max lines, and diff prefix concealment
+- Inline merge conflict detection, highlighting, and resolution keymaps
+- Configurable debouncing, max lines, diff prefix concealment, blend alpha, and
+  highlight overrides
 
 ## Requirements
 
@@ -41,12 +43,11 @@ luarocks install diffs.nvim
 
 ## Known Limitations
 
-- **Incomplete syntax context**: Treesitter parses each diff hunk in isolation
-  without surrounding code context. When a hunk shows lines added to an existing
-  block (e.g., adding a plugin inside `return { ... }`), the parser doesn't see
-  the `return` statement and may produce incorrect highlighting. This is
-  inherent to parsing code fragments—no diff tooling solves this without
-  significant complexity.
+- **Incomplete syntax context**: Treesitter parses each diff hunk in isolation.
+  To improve accuracy, `diffs.nvim` reads lines from disk before and after each
+  hunk for parsing context (`highlights.context`, enabled by default with 25
+  lines). This resolves most boundary issues. Set
+  `highlights.context.enabled = false` to disable.
 
 - **Syntax flashing**: `diffs.nvim` hooks into the `FileType fugitive` event
   triggered by `vim-fugitive`, at which point the buffer is preliminarily
@@ -63,12 +64,17 @@ luarocks install diffs.nvim
     compatible, but both plugins modifying line highlights may produce
     unexpected results
   - [`git-conflict.nvim`](https://github.com/akinsho/git-conflict.nvim) -
-    conflict marker highlighting may overlap with `diffs.nvim`
+    `diffs.nvim` now includes built-in conflict resolution; disable one or the
+    other to avoid overlap
 
 # Acknowledgements
 
 - [`vim-fugitive`](https://github.com/tpope/vim-fugitive)
 - [`codediff.nvim`](https://github.com/esmuellert/codediff.nvim)
 - [`diffview.nvim`](https://github.com/sindrets/diffview.nvim)
+- [`difftastic`](https://github.com/Wilfred/difftastic)
+- [`mini.diff`](https://github.com/echasnovski/mini.diff)
+- [`gitsigns.nvim`](https://github.com/lewis6991/gitsigns.nvim)
+- [`git-conflict.nvim`](https://github.com/akinsho/git-conflict.nvim)
 - [@phanen](https://github.com/phanen) - diff header highlighting, unknown
-  filetype fix, shebang/modeline detection
+  filetype fix, shebang/modeline detection, treesitter injection support

doc/diffs.nvim.txt

@@ -20,6 +20,7 @@ Features: ~
 - Blended diff background colors that preserve syntax visibility
 - Optional diff prefix (`+`/`-`/` `) concealment
 - Gutter (line number) highlighting
+- Inline merge conflict marker detection, highlighting, and resolution
 
 ==============================================================================
 REQUIREMENTS                                              *diffs-requirements*
@@ -56,24 +57,43 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
       highlights = {
         background = true,
         gutter = true,
+        blend_alpha = 0.6,
+        context = {
+          enabled = true,
+          lines = 25,
+        },
         treesitter = {
           enabled = true,
           max_lines = 500,
         },
         vim = {
           enabled = false,
-          max_lines = 500,
+          max_lines = 200,
         },
         intra = {
           enabled = true,
           algorithm = 'default',
           max_lines = 500,
         },
+        overrides = {},
       },
       fugitive = {
         horizontal = 'du',
         vertical = 'dU',
       },
+      conflict = {
+        enabled = true,
+        disable_diagnostics = true,
+        show_virtual_text = true,
+        keymaps = {
+          ours = 'doo',
+          theirs = 'dot',
+          both = 'dob',
+          none = 'don',
+          next = ']x',
+          prev = '[x',
+        },
+      },
     }
 <
                                                               *diffs.Config*
@@ -102,6 +122,10 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Fugitive status buffer keymap options.
                              See |diffs.FugitiveConfig| for fields.
 
+        {conflict}           (table, default: see below)
+                             Inline merge conflict resolution options.
+                             See |diffs.ConflictConfig| for fields.
+
                                                           *diffs.Highlights*
     Highlights table fields: ~
         {background}         (boolean, default: true)
@@ -113,6 +137,17 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Highlight line numbers with matching colors.
                              Only visible if line numbers are enabled.
 
+        {blend_alpha}        (number, default: 0.6)
+                             Alpha value for character-level blend intensity.
+                             Controls how strongly changed characters stand
+                             out from the line-level background. Must be
+                             between 0 and 1 (inclusive). Higher values
+                             produce more vivid character-level highlights.
+
+        {context}            (table, default: see below)
+                             Syntax parsing context options.
+                             See |diffs.ContextConfig| for fields.
+
         {treesitter}         (table, default: see below)
                              Treesitter highlighting options.
                              See |diffs.TreesitterConfig| for fields.
@@ -125,6 +160,27 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Character-level (intra-line) diff highlighting.
                              See |diffs.IntraConfig| for fields.
 
+        {overrides}          (table, default: {})
+                             Map of highlight group names to highlight
+                             definitions (see |nvim_set_hl()|). Applied
+                             after all computed groups without `default`,
+                             so overrides always win over both computed
+                             defaults and colorscheme definitions.
+
+                                                      *diffs.ContextConfig*
+    Context config fields: ~
+        {enabled}            (boolean, default: true)
+                             Read lines from disk before and after each hunk
+                             to provide surrounding syntax context. Improves
+                             accuracy at hunk boundaries where incomplete
+                             constructs (e.g., a function definition with no
+                             body) would otherwise confuse the parser.
+
+        {lines}              (integer, default: 25)
+                             Number of context lines to read in each
+                             direction. Lines are read with early exit —
+                             cost scales with this value, not file size.
+
                                                     *diffs.TreesitterConfig*
     Treesitter config fields: ~
         {enabled}            (boolean, default: true)
@@ -188,6 +244,9 @@ COMMANDS                                                      *diffs-commands*
     code language, plus diff header highlighting for `diff --git`, `---`,
     `+++`, and `@@` lines.
 
+    If a `diffs://` window already exists in the current tabpage, the new
+    diff replaces its buffer instead of creating another split.
+
     Parameters: ~
         {revision}  (string, optional) Git revision to diff against.
                     Defaults to HEAD.
@@ -205,6 +264,63 @@ COMMANDS                                                      *diffs-commands*
 :Ghdiff [revision]                                                  *:Ghdiff*
     Like |:Gdiff| but explicitly opens in a horizontal split.
 
+==============================================================================
+MAPPINGS                                                     *diffs-mappings*
+
+                                                        *<Plug>(diffs-gdiff)*
+<Plug>(diffs-gdiff)     Show unified diff against HEAD in a horizontal
+                        split. Equivalent to |:Gdiff| with no arguments.
+
+                                                       *<Plug>(diffs-gvdiff)*
+<Plug>(diffs-gvdiff)    Show unified diff against HEAD in a vertical
+                        split. Equivalent to |:Gvdiff| with no arguments.
+
+Example configuration: >lua
+    vim.keymap.set('n', '<leader>gd', '<Plug>(diffs-gdiff)')
+    vim.keymap.set('n', '<leader>gD', '<Plug>(diffs-gvdiff)')
+<
+
+                                              *<Plug>(diffs-conflict-ours)*
+<Plug>(diffs-conflict-ours)
+                        Accept current (ours) change. Replaces the
+                        conflict block with ours content.
+
+                                            *<Plug>(diffs-conflict-theirs)*
+<Plug>(diffs-conflict-theirs)
+                        Accept incoming (theirs) change. Replaces the
+                        conflict block with theirs content.
+
+                                              *<Plug>(diffs-conflict-both)*
+<Plug>(diffs-conflict-both)
+                        Accept both changes (ours then theirs).
+
+                                              *<Plug>(diffs-conflict-none)*
+<Plug>(diffs-conflict-none)
+                        Reject both changes (delete entire block).
+
+                                              *<Plug>(diffs-conflict-next)*
+<Plug>(diffs-conflict-next)
+                        Jump to next conflict marker. Wraps around.
+
+                                              *<Plug>(diffs-conflict-prev)*
+<Plug>(diffs-conflict-prev)
+                        Jump to previous conflict marker. Wraps around.
+
+Example configuration: >lua
+    vim.keymap.set('n', 'co', '<Plug>(diffs-conflict-ours)')
+    vim.keymap.set('n', 'ct', '<Plug>(diffs-conflict-theirs)')
+    vim.keymap.set('n', 'cb', '<Plug>(diffs-conflict-both)')
+    vim.keymap.set('n', 'cn', '<Plug>(diffs-conflict-none)')
+    vim.keymap.set('n', ']x', '<Plug>(diffs-conflict-next)')
+    vim.keymap.set('n', '[x', '<Plug>(diffs-conflict-prev)')
+<
+
+Diff buffer mappings: ~
+                                                              *diffs-q*
+    q               Close the diff window. Available in all `diffs://`
+                    buffers created by |:Gdiff|, |:Gvdiff|, |:Ghdiff|,
+                    or the fugitive status keymaps.
+
 ==============================================================================
 FUGITIVE STATUS KEYMAPS                                   *diffs-fugitive*
 
@@ -254,6 +370,94 @@ Configuration: ~
                              Keymap for unified diff in vertical split.
                              Set to `false` to disable.
 
+==============================================================================
+CONFLICT RESOLUTION                                          *diffs-conflict*
+
+diffs.nvim detects inline merge conflict markers (`<<<<<<<`/`=======`/
+`>>>>>>>`) in working files and provides highlighting and resolution keymaps.
+Both standard and diff3 (`|||||||`) formats are supported.
+
+Conflict regions are detected automatically on `BufReadPost` and re-scanned
+on `TextChanged`. When all conflicts in a buffer are resolved, highlighting
+is removed and diagnostics are re-enabled.
+
+Configuration: ~
+                                                      *diffs.ConflictConfig*
+>lua
+    vim.g.diffs = {
+      conflict = {
+        enabled = true,
+        disable_diagnostics = true,
+        show_virtual_text = true,
+        keymaps = {
+          ours = 'doo',
+          theirs = 'dot',
+          both = 'dob',
+          none = 'don',
+          next = ']x',
+          prev = '[x',
+        },
+      },
+    }
+<
+    Fields: ~
+        {enabled}            (boolean, default: true)
+                             Enable conflict marker detection and
+                             resolution. Set to `false` to disable
+                             entirely.
+
+        {disable_diagnostics} (boolean, default: true)
+                             Suppress LSP diagnostics on buffers with
+                             conflict markers. Markers produce syntax
+                             errors that clutter the diagnostic list.
+                             Diagnostics are re-enabled when all conflicts
+                             are resolved. Set `false` to leave
+                             diagnostics alone.
+
+        {show_virtual_text}  (boolean, default: true)
+                             Show virtual text labels (" current" and
+                             " incoming") at the end of `<<<<<<<` and
+                             `>>>>>>>` marker lines.
+
+        {keymaps}            (table, default: see above)
+                             Buffer-local keymaps for conflict resolution
+                             and navigation. Each value accepts a string
+                             (custom key) or `false` (disabled).
+
+                                                  *diffs.ConflictKeymaps*
+    Keymap fields: ~
+        {ours}               (string|false, default: 'doo')
+                             Accept current (ours) change.
+
+        {theirs}             (string|false, default: 'dot')
+                             Accept incoming (theirs) change.
+
+        {both}               (string|false, default: 'dob')
+                             Accept both changes (ours then theirs).
+
+        {none}               (string|false, default: 'don')
+                             Reject both changes (delete entire block).
+
+        {next}               (string|false, default: ']x')
+                             Jump to next conflict marker. Wraps around.
+
+        {prev}               (string|false, default: '[x')
+                             Jump to previous conflict marker. Wraps
+                             around.
+
+User events: ~
+                                                   *DiffsConflictResolved*
+    DiffsConflictResolved   Fired when the last conflict in a buffer is
+                            resolved. Useful for triggering custom actions
+                            (e.g., auto-staging the file). >lua
+                                vim.api.nvim_create_autocmd('User', {
+                                  pattern = 'DiffsConflictResolved',
+                                  callback = function()
+                                    print('all conflicts resolved!')
+                                  end,
+                                })
+<
+
 ==============================================================================
 API                                                                *diffs-api*
 
@@ -305,14 +509,15 @@ KNOWN LIMITATIONS                                       *diffs-limitations*
 
 Incomplete Syntax Context ~
                                                       *diffs-syntax-context*
-Treesitter parses each diff hunk in isolation without surrounding code
-context. When a hunk shows lines added to an existing block (e.g., adding a
-plugin inside `return { ... }`), the parser doesn't see the `return`
-statement and may produce incorrect or unusual highlighting.
+Treesitter parses each diff hunk in isolation. To provide surrounding code
+context, diffs.nvim reads lines from disk before and after each hunk
+(see |diffs.ContextConfig|, enabled by default). This resolves most boundary
+issues where incomplete constructs (e.g., a function definition at the edge
+of a hunk with no body) would confuse the parser.
 
-This is inherent to parsing code fragments. No diff tooling solves this
-problem without significant complexity—the parser simply doesn't have enough
-information to understand the full syntactic structure.
+Set `highlights.context.enabled = false` to disable context padding. In rare
+cases, context padding may not help if the relevant surrounding code is very
+far from the hunk boundaries.
 
 Syntax Highlighting Flash ~
                                                              *diffs-flash*
@@ -350,8 +555,9 @@ conflict:
       modifying line highlights may produce unexpected results.
 
   - git-conflict.nvim (akinsho/git-conflict.nvim)
-      Provides conflict marker highlighting that may overlap with
-      diffs.nvim's highlighting in conflict scenarios.
+      Provides conflict marker highlighting and resolution keymaps.
+      diffs.nvim now has built-in conflict resolution (see
+      |diffs-conflict|). Disable one or the other to avoid overlap.
 
 If you experience visual conflicts, try disabling the conflicting plugin's
 diff-related features.
@@ -359,9 +565,15 @@ diff-related features.
 ==============================================================================
 HIGHLIGHT GROUPS                                          *diffs-highlights*
 
-diffs.nvim defines custom highlight groups. Fugitive unified diff groups use
-`default = true`, so colorschemes can override them. Diff mode groups are
-always derived from the corresponding `Diff*` groups.
+diffs.nvim defines custom highlight groups. All groups use `default = true`,
+so colorschemes can override them by defining the group before the plugin
+loads.
+
+All derived groups are computed by alpha-blending a source color into the
+`Normal` background. Line-level groups blend at 40% alpha for a subtle tint;
+character-level groups blend at 60% for more contrast. Line-number groups
+combine both: background from the line-level blend, foreground from the
+character-level blend.
 
 Fugitive unified diff highlights: ~
                                                                   *DiffsAdd*
@@ -374,23 +586,54 @@ Fugitive unified diff highlights: ~
 
                                                                 *DiffsAddNr*
     DiffsAddNr          Line number for `+` lines. Foreground from
-                        `diffAdded`, background from `DiffsAdd`.
+                        `DiffsAddText`, background from `DiffsAdd`.
 
                                                              *DiffsDeleteNr*
     DiffsDeleteNr       Line number for `-` lines. Foreground from
-                        `diffRemoved`, background from `DiffsDelete`.
+                        `DiffsDeleteText`, background from `DiffsDelete`.
 
                                                               *DiffsAddText*
     DiffsAddText        Character-level background for changed characters
                         within `+` lines. Derived by blending `diffAdded`
-                        foreground with `Normal` background at 70% alpha.
+                        foreground with `Normal` background at 60% alpha.
                         Only sets `bg`, so treesitter foreground colors show
                         through.
 
                                                            *DiffsDeleteText*
     DiffsDeleteText     Character-level background for changed characters
                         within `-` lines. Derived by blending `diffRemoved`
-                        foreground with `Normal` background at 70% alpha.
+                        foreground with `Normal` background at 60% alpha.
+
+Conflict highlights: ~
+                                                        *DiffsConflictOurs*
+    DiffsConflictOurs   Background for "ours" (current) content lines.
+                        Derived by blending `DiffAdd` background with
+                        `Normal` at 40% alpha (green tint).
+
+                                                      *DiffsConflictTheirs*
+    DiffsConflictTheirs Background for "theirs" (incoming) content lines.
+                        Derived by blending `DiffChange` background with
+                        `Normal` at 40% alpha.
+
+                                                        *DiffsConflictBase*
+    DiffsConflictBase   Background for base (ancestor) content lines in
+                        diff3 conflicts. Derived by blending `DiffText`
+                        background with `Normal` at 30% alpha (muted).
+
+                                                      *DiffsConflictMarker*
+    DiffsConflictMarker Dimmed foreground with bold for `<<<<<<<`,
+                        `=======`, `>>>>>>>`, and `|||||||` marker lines.
+
+                                                      *DiffsConflictOursNr*
+    DiffsConflictOursNr Line number for "ours" content lines. Foreground
+                        from higher-alpha blend, background from line-level
+                        blend.
+
+                                                    *DiffsConflictTheirsNr*
+    DiffsConflictTheirsNr Line number for "theirs" content lines.
+
+                                                      *DiffsConflictBaseNr*
+    DiffsConflictBaseNr Line number for base content lines (diff3).
 
 Diff mode window highlights: ~
 These are used for |winhighlight| remapping in `&diff` windows.
@@ -416,6 +659,16 @@ To customize these in your colorscheme: >lua
     vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = '#2e4a3a' })
     vim.api.nvim_set_hl(0, 'DiffsDiffDelete', { link = 'DiffDelete' })
 <
+Or via `highlights.overrides` in config: >lua
+    vim.g.diffs = {
+      highlights = {
+        overrides = {
+          DiffsAdd = { bg = '#2e4a3a' },
+          DiffsDiffDelete = { link = 'DiffDelete' },
+        },
+      },
+    }
+<
 
 ==============================================================================
 HEALTH CHECK                                                 *diffs-health*
@@ -433,7 +686,8 @@ ACKNOWLEDGEMENTS                                     *diffs-acknowledgements*
 - vim-fugitive (https://github.com/tpope/vim-fugitive)
 - codediff.nvim (https://github.com/esmuellert/codediff.nvim)
 - diffview.nvim (https://github.com/sindrets/diffview.nvim)
-- @phanen (https://github.com/phanen) - diff header highlighting
+- @phanen (https://github.com/phanen) - diff header highlighting,
+  treesitter injection support
 
 ==============================================================================
  vim:tw=78:ts=8:ft=help:norl:

lua/diffs/commands.lua

@@ -3,6 +3,27 @@ local M = {}
 local git = require('diffs.git')
 local dbg = require('diffs.log').dbg
 
+---@return integer?
+function M.find_diffs_window()
+  local tabpage = vim.api.nvim_get_current_tabpage()
+  for _, win in ipairs(vim.api.nvim_tabpage_list_wins(tabpage)) do
+    if vim.api.nvim_win_is_valid(win) then
+      local buf = vim.api.nvim_win_get_buf(win)
+      local name = vim.api.nvim_buf_get_name(buf)
+      if name:match('^diffs://') then
+        return win
+      end
+    end
+  end
+  return nil
+end
+
+---@param bufnr integer
+function M.setup_diff_buf(bufnr)
+  vim.diagnostic.enable(false, { bufnr = bufnr })
+  vim.keymap.set('n', 'q', '<cmd>close<CR>', { buffer = bufnr })
+end
+
 ---@param diff_lines string[]
 ---@param hunk_position { hunk_header: string, offset: integer }
 ---@return integer?
@@ -96,9 +117,16 @@ function M.gdiff(revision, vertical)
     vim.api.nvim_buf_set_var(diff_buf, 'diffs_repo_root', repo_root)
   end
 
-  vim.cmd(vertical and 'vsplit' or 'split')
-  vim.api.nvim_win_set_buf(0, diff_buf)
+  local existing_win = M.find_diffs_window()
+  if existing_win then
+    vim.api.nvim_set_current_win(existing_win)
+    vim.api.nvim_win_set_buf(existing_win, diff_buf)
+  else
+    vim.cmd(vertical and 'vsplit' or 'split')
+    vim.api.nvim_win_set_buf(0, diff_buf)
+  end
 
+  M.setup_diff_buf(diff_buf)
   dbg('opened diff buffer %d for %s against %s', diff_buf, rel_path, revision)
 
   vim.schedule(function()
@@ -190,8 +218,14 @@ function M.gdiff_file(filepath, opts)
     vim.api.nvim_buf_set_var(diff_buf, 'diffs_old_filepath', old_rel_path)
   end
 
-  vim.cmd(opts.vertical and 'vsplit' or 'split')
-  vim.api.nvim_win_set_buf(0, diff_buf)
+  local existing_win = M.find_diffs_window()
+  if existing_win then
+    vim.api.nvim_set_current_win(existing_win)
+    vim.api.nvim_win_set_buf(existing_win, diff_buf)
+  else
+    vim.cmd(opts.vertical and 'vsplit' or 'split')
+    vim.api.nvim_win_set_buf(0, diff_buf)
+  end
 
   if opts.hunk_position then
     local target_line = M.find_hunk_line(diff_lines, opts.hunk_position)
@@ -201,6 +235,7 @@ function M.gdiff_file(filepath, opts)
     end
   end
 
+  M.setup_diff_buf(diff_buf)
   dbg('opened diff buffer %d for %s (%s)', diff_buf, rel_path, diff_label)
 
   vim.schedule(function()
@@ -244,9 +279,16 @@ function M.gdiff_section(repo_root, opts)
   vim.api.nvim_buf_set_name(diff_buf, 'diffs://' .. diff_label .. ':all')
   vim.api.nvim_buf_set_var(diff_buf, 'diffs_repo_root', repo_root)
 
-  vim.cmd(opts.vertical and 'vsplit' or 'split')
-  vim.api.nvim_win_set_buf(0, diff_buf)
+  local existing_win = M.find_diffs_window()
+  if existing_win then
+    vim.api.nvim_set_current_win(existing_win)
+    vim.api.nvim_win_set_buf(existing_win, diff_buf)
+  else
+    vim.cmd(opts.vertical and 'vsplit' or 'split')
+    vim.api.nvim_win_set_buf(0, diff_buf)
+  end
 
+  M.setup_diff_buf(diff_buf)
   dbg('opened section diff buffer %d (%s)', diff_buf, diff_label)
 
   vim.schedule(function()

lua/diffs/conflict.lua

@@ -0,0 +1,438 @@
+---@class diffs.ConflictRegion
+---@field marker_ours integer
+---@field ours_start integer
+---@field ours_end integer
+---@field marker_base integer?
+---@field base_start integer?
+---@field base_end integer?
+---@field marker_sep integer
+---@field theirs_start integer
+---@field theirs_end integer
+---@field marker_theirs integer
+
+local M = {}
+
+local ns = vim.api.nvim_create_namespace('diffs-conflict')
+
+---@type table<integer, true>
+local attached_buffers = {}
+
+---@type table<integer, boolean>
+local diagnostics_suppressed = {}
+
+local PRIORITY_LINE_BG = 200
+
+---@param lines string[]
+---@return diffs.ConflictRegion[]
+function M.parse(lines)
+  local regions = {}
+  local state = 'idle'
+  ---@type table?
+  local current = nil
+
+  for i, line in ipairs(lines) do
+    local idx = i - 1
+
+    if state == 'idle' then
+      if line:match('^<<<<<<<') then
+        current = { marker_ours = idx, ours_start = idx + 1 }
+        state = 'in_ours'
+      end
+    elseif state == 'in_ours' then
+      if line:match('^|||||||') then
+        current.ours_end = idx
+        current.marker_base = idx
+        current.base_start = idx + 1
+        state = 'in_base'
+      elseif line:match('^=======') then
+        current.ours_end = idx
+        current.marker_sep = idx
+        current.theirs_start = idx + 1
+        state = 'in_theirs'
+      elseif line:match('^<<<<<<<') then
+        current = { marker_ours = idx, ours_start = idx + 1 }
+      elseif line:match('^>>>>>>>') then
+        current = nil
+        state = 'idle'
+      end
+    elseif state == 'in_base' then
+      if line:match('^=======') then
+        current.base_end = idx
+        current.marker_sep = idx
+        current.theirs_start = idx + 1
+        state = 'in_theirs'
+      elseif line:match('^<<<<<<<') then
+        current = { marker_ours = idx, ours_start = idx + 1 }
+        state = 'in_ours'
+      elseif line:match('^>>>>>>>') then
+        current = nil
+        state = 'idle'
+      end
+    elseif state == 'in_theirs' then
+      if line:match('^>>>>>>>') then
+        current.theirs_end = idx
+        current.marker_theirs = idx
+        table.insert(regions, current)
+        current = nil
+        state = 'idle'
+      elseif line:match('^<<<<<<<') then
+        current = { marker_ours = idx, ours_start = idx + 1 }
+        state = 'in_ours'
+      end
+    end
+  end
+
+  return regions
+end
+
+---@param bufnr integer
+---@return diffs.ConflictRegion[]
+local function parse_buffer(bufnr)
+  local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+  return M.parse(lines)
+end
+
+---@param bufnr integer
+---@param regions diffs.ConflictRegion[]
+---@param config diffs.ConflictConfig
+local function apply_highlights(bufnr, regions, config)
+  vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
+
+  for _, region in ipairs(regions) do
+    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_ours, 0, {
+      end_row = region.marker_ours + 1,
+      hl_group = 'DiffsConflictMarker',
+      hl_eol = true,
+      priority = PRIORITY_LINE_BG,
+    })
+
+    if config.show_virtual_text then
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_ours, 0, {
+        virt_text = { { ' (current)', 'DiffsConflictMarker' } },
+        virt_text_pos = 'eol',
+      })
+    end
+
+    for line = region.ours_start, region.ours_end - 1 do
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+        end_row = line + 1,
+        hl_group = 'DiffsConflictOurs',
+        hl_eol = true,
+        priority = PRIORITY_LINE_BG,
+      })
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+        number_hl_group = 'DiffsConflictOursNr',
+        priority = PRIORITY_LINE_BG,
+      })
+    end
+
+    if region.marker_base then
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_base, 0, {
+        end_row = region.marker_base + 1,
+        hl_group = 'DiffsConflictMarker',
+        hl_eol = true,
+        priority = PRIORITY_LINE_BG,
+      })
+
+      for line = region.base_start, region.base_end - 1 do
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+          end_row = line + 1,
+          hl_group = 'DiffsConflictBase',
+          hl_eol = true,
+          priority = PRIORITY_LINE_BG,
+        })
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+          number_hl_group = 'DiffsConflictBaseNr',
+          priority = PRIORITY_LINE_BG,
+        })
+      end
+    end
+
+    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_sep, 0, {
+      end_row = region.marker_sep + 1,
+      hl_group = 'DiffsConflictMarker',
+      hl_eol = true,
+      priority = PRIORITY_LINE_BG,
+    })
+
+    for line = region.theirs_start, region.theirs_end - 1 do
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+        end_row = line + 1,
+        hl_group = 'DiffsConflictTheirs',
+        hl_eol = true,
+        priority = PRIORITY_LINE_BG,
+      })
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
+        number_hl_group = 'DiffsConflictTheirsNr',
+        priority = PRIORITY_LINE_BG,
+      })
+    end
+
+    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_theirs, 0, {
+      end_row = region.marker_theirs + 1,
+      hl_group = 'DiffsConflictMarker',
+      hl_eol = true,
+      priority = PRIORITY_LINE_BG,
+    })
+
+    if config.show_virtual_text then
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_theirs, 0, {
+        virt_text = { { ' (incoming)', 'DiffsConflictMarker' } },
+        virt_text_pos = 'eol',
+      })
+    end
+  end
+end
+
+---@param cursor_line integer
+---@param regions diffs.ConflictRegion[]
+---@return diffs.ConflictRegion?
+local function find_conflict_at_cursor(cursor_line, regions)
+  for _, region in ipairs(regions) do
+    if cursor_line >= region.marker_ours and cursor_line <= region.marker_theirs then
+      return region
+    end
+  end
+  return nil
+end
+
+---@param bufnr integer
+---@param region diffs.ConflictRegion
+---@param replacement string[]
+local function replace_region(bufnr, region, replacement)
+  vim.api.nvim_buf_set_lines(
+    bufnr,
+    region.marker_ours,
+    region.marker_theirs + 1,
+    false,
+    replacement
+  )
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+local function refresh(bufnr, config)
+  local regions = parse_buffer(bufnr)
+  if #regions == 0 then
+    vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
+    if diagnostics_suppressed[bufnr] then
+      pcall(vim.diagnostic.reset, nil, bufnr)
+      pcall(vim.diagnostic.enable, true, { bufnr = bufnr })
+      diagnostics_suppressed[bufnr] = nil
+    end
+    vim.api.nvim_exec_autocmds('User', { pattern = 'DiffsConflictResolved' })
+    return
+  end
+  apply_highlights(bufnr, regions, config)
+  if config.disable_diagnostics and not diagnostics_suppressed[bufnr] then
+    pcall(vim.diagnostic.enable, false, { bufnr = bufnr })
+    diagnostics_suppressed[bufnr] = true
+  end
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_ours(bufnr, config)
+  if not vim.api.nvim_get_option_value('modifiable', { buf = bufnr }) then
+    vim.notify('[diffs.nvim]: buffer is not modifiable', vim.log.levels.WARN)
+    return
+  end
+  local regions = parse_buffer(bufnr)
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local region = find_conflict_at_cursor(cursor[1] - 1, regions)
+  if not region then
+    return
+  end
+  local lines = vim.api.nvim_buf_get_lines(bufnr, region.ours_start, region.ours_end, false)
+  replace_region(bufnr, region, lines)
+  refresh(bufnr, config)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_theirs(bufnr, config)
+  if not vim.api.nvim_get_option_value('modifiable', { buf = bufnr }) then
+    vim.notify('[diffs.nvim]: buffer is not modifiable', vim.log.levels.WARN)
+    return
+  end
+  local regions = parse_buffer(bufnr)
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local region = find_conflict_at_cursor(cursor[1] - 1, regions)
+  if not region then
+    return
+  end
+  local lines = vim.api.nvim_buf_get_lines(bufnr, region.theirs_start, region.theirs_end, false)
+  replace_region(bufnr, region, lines)
+  refresh(bufnr, config)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_both(bufnr, config)
+  if not vim.api.nvim_get_option_value('modifiable', { buf = bufnr }) then
+    vim.notify('[diffs.nvim]: buffer is not modifiable', vim.log.levels.WARN)
+    return
+  end
+  local regions = parse_buffer(bufnr)
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local region = find_conflict_at_cursor(cursor[1] - 1, regions)
+  if not region then
+    return
+  end
+  local ours = vim.api.nvim_buf_get_lines(bufnr, region.ours_start, region.ours_end, false)
+  local theirs = vim.api.nvim_buf_get_lines(bufnr, region.theirs_start, region.theirs_end, false)
+  local combined = {}
+  for _, l in ipairs(ours) do
+    table.insert(combined, l)
+  end
+  for _, l in ipairs(theirs) do
+    table.insert(combined, l)
+  end
+  replace_region(bufnr, region, combined)
+  refresh(bufnr, config)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_none(bufnr, config)
+  if not vim.api.nvim_get_option_value('modifiable', { buf = bufnr }) then
+    vim.notify('[diffs.nvim]: buffer is not modifiable', vim.log.levels.WARN)
+    return
+  end
+  local regions = parse_buffer(bufnr)
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local region = find_conflict_at_cursor(cursor[1] - 1, regions)
+  if not region then
+    return
+  end
+  replace_region(bufnr, region, {})
+  refresh(bufnr, config)
+end
+
+---@param bufnr integer
+function M.goto_next(bufnr)
+  local regions = parse_buffer(bufnr)
+  if #regions == 0 then
+    return
+  end
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local cursor_line = cursor[1] - 1
+  for _, region in ipairs(regions) do
+    if region.marker_ours > cursor_line then
+      vim.api.nvim_win_set_cursor(0, { region.marker_ours + 1, 0 })
+      return
+    end
+  end
+  vim.api.nvim_win_set_cursor(0, { regions[1].marker_ours + 1, 0 })
+end
+
+---@param bufnr integer
+function M.goto_prev(bufnr)
+  local regions = parse_buffer(bufnr)
+  if #regions == 0 then
+    return
+  end
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local cursor_line = cursor[1] - 1
+  for i = #regions, 1, -1 do
+    if regions[i].marker_ours < cursor_line then
+      vim.api.nvim_win_set_cursor(0, { regions[i].marker_ours + 1, 0 })
+      return
+    end
+  end
+  vim.api.nvim_win_set_cursor(0, { regions[#regions].marker_ours + 1, 0 })
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+local function setup_keymaps(bufnr, config)
+  local km = config.keymaps
+
+  local maps = {
+    { km.ours, '<Plug>(diffs-conflict-ours)' },
+    { km.theirs, '<Plug>(diffs-conflict-theirs)' },
+    { km.both, '<Plug>(diffs-conflict-both)' },
+    { km.none, '<Plug>(diffs-conflict-none)' },
+    { km.next, '<Plug>(diffs-conflict-next)' },
+    { km.prev, '<Plug>(diffs-conflict-prev)' },
+  }
+
+  for _, map in ipairs(maps) do
+    if map[1] then
+      vim.keymap.set('n', map[1], map[2], { buffer = bufnr })
+    end
+  end
+end
+
+---@param bufnr integer
+function M.detach(bufnr)
+  vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
+  attached_buffers[bufnr] = nil
+
+  if diagnostics_suppressed[bufnr] then
+    pcall(vim.diagnostic.reset, nil, bufnr)
+    pcall(vim.diagnostic.enable, true, { bufnr = bufnr })
+    diagnostics_suppressed[bufnr] = nil
+  end
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.attach(bufnr, config)
+  if attached_buffers[bufnr] then
+    return
+  end
+
+  local buftype = vim.api.nvim_get_option_value('buftype', { buf = bufnr })
+  if buftype ~= '' then
+    return
+  end
+
+  local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+  local has_marker = false
+  for _, line in ipairs(lines) do
+    if line:match('^<<<<<<<') then
+      has_marker = true
+      break
+    end
+  end
+  if not has_marker then
+    return
+  end
+
+  attached_buffers[bufnr] = true
+
+  local regions = M.parse(lines)
+  apply_highlights(bufnr, regions, config)
+  setup_keymaps(bufnr, config)
+
+  if config.disable_diagnostics then
+    pcall(vim.diagnostic.enable, false, { bufnr = bufnr })
+    diagnostics_suppressed[bufnr] = true
+  end
+
+  vim.api.nvim_create_autocmd({ 'TextChanged', 'TextChangedI' }, {
+    buffer = bufnr,
+    callback = function()
+      if not attached_buffers[bufnr] then
+        return true
+      end
+      refresh(bufnr, config)
+    end,
+  })
+
+  vim.api.nvim_create_autocmd('BufWipeout', {
+    buffer = bufnr,
+    callback = function()
+      attached_buffers[bufnr] = nil
+      diagnostics_suppressed[bufnr] = nil
+    end,
+  })
+end
+
+---@return integer
+function M.get_namespace()
+  return ns
+end
+
+return M

lua/diffs/debug.lua

@@ -18,14 +18,16 @@ function M.dump()
       end_col = details.end_col,
       hl_group = details.hl_group,
       priority = details.priority,
+      hl_eol = details.hl_eol,
       line_hl_group = details.line_hl_group,
       number_hl_group = details.number_hl_group,
       virt_text = details.virt_text,
     }
-    if not by_line[row] then
-      by_line[row] = { text = lines[row + 1] or '', marks = {} }
+    local key = tostring(row)
+    if not by_line[key] then
+      by_line[key] = { text = lines[row + 1] or '', marks = {} }
     end
-    table.insert(by_line[row].marks, entry)
+    table.insert(by_line[key].marks, entry)
   end
 
   local all_ns_marks = vim.api.nvim_buf_get_extmarks(bufnr, -1, 0, -1, { details = true })

lua/diffs/diff.lua

@@ -137,7 +137,12 @@ local function char_diff_pair(old_line, new_line, del_idx, add_idx, diff_opts)
   local old_text = table.concat(old_bytes, '\n') .. '\n'
   local new_text = table.concat(new_bytes, '\n') .. '\n'
 
-  local char_hunks = byte_diff(old_text, new_text, diff_opts)
+  local char_opts = diff_opts
+  if diff_opts and diff_opts.linematch then
+    char_opts = { algorithm = diff_opts.algorithm }
+  end
+
+  local char_hunks = byte_diff(old_text, new_text, char_opts)
 
   for _, ch in ipairs(char_hunks) do
     if ch.old_count > 0 then

lua/diffs/highlight.lua

@@ -3,15 +3,53 @@ local M = {}
 local dbg = require('diffs.log').dbg
 local diff = require('diffs.diff')
 
+---@param filepath string
+---@param from_line integer
+---@param count integer
+---@return string[]
+local function read_line_range(filepath, from_line, count)
+  if count <= 0 then
+    return {}
+  end
+  local f = io.open(filepath, 'r')
+  if not f then
+    return {}
+  end
+  local result = {}
+  local line_num = 0
+  for line in f:lines() do
+    line_num = line_num + 1
+    if line_num >= from_line then
+      table.insert(result, line)
+      if #result >= count then
+        break
+      end
+    end
+  end
+  f:close()
+  return result
+end
+
+local PRIORITY_CLEAR = 198
+local PRIORITY_SYNTAX = 199
+local PRIORITY_LINE_BG = 200
+local PRIORITY_CHAR_BG = 201
+
 ---@param bufnr integer
 ---@param ns integer
 ---@param hunk diffs.Hunk
 ---@param col_offset integer
 ---@param text string
 ---@param lang string
+---@param context_lines? string[]
 ---@return integer
-local function highlight_text(bufnr, ns, hunk, col_offset, text, lang)
-  local ok, parser_obj = pcall(vim.treesitter.get_string_parser, text, lang)
+local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines)
+  local parse_text = text
+  if context_lines and #context_lines > 0 then
+    parse_text = text .. '\n' .. table.concat(context_lines, '\n')
+  end
+
+  local ok, parser_obj = pcall(vim.treesitter.get_string_parser, parse_text, lang)
   if not ok or not parser_obj then
     return 0
   end
@@ -29,24 +67,26 @@ local function highlight_text(bufnr, ns, hunk, col_offset, text, lang)
   local extmark_count = 0
   local header_line = hunk.start_line - 1
 
-  for id, node, metadata in query:iter_captures(trees[1]:root(), text) do
-    local capture_name = '@' .. query.captures[id] .. '.' .. lang
-    local sr, sc, er, ec = node:range()
+  for id, node, metadata in query:iter_captures(trees[1]:root(), parse_text) do
+    local sr, sc, _, ec = node:range()
+    if sr == 0 then
+      local capture_name = '@' .. query.captures[id] .. '.' .. lang
 
-    local buf_sr = header_line + sr
-    local buf_er = header_line + er
-    local buf_sc = col_offset + sc
-    local buf_ec = col_offset + ec
+      local buf_sr = header_line
+      local buf_er = header_line
+      local buf_sc = col_offset + sc
+      local buf_ec = col_offset + ec
 
-    local priority = lang == 'diff' and (tonumber(metadata.priority) or 100) or 200
+      local priority = lang == 'diff' and (tonumber(metadata.priority) or 100) or PRIORITY_SYNTAX
 
-    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
-      end_row = buf_er,
-      end_col = buf_ec,
-      hl_group = capture_name,
-      priority = priority,
-    })
-    extmark_count = extmark_count + 1
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
+        end_row = buf_er,
+        end_col = buf_ec,
+        hl_group = capture_name,
+        priority = priority,
+      })
+      extmark_count = extmark_count + 1
+    end
   end
 
   return extmark_count
@@ -58,16 +98,21 @@ end
 
 ---@param bufnr integer
 ---@param ns integer
----@param hunk diffs.Hunk
 ---@param code_lines string[]
----@param col_offset integer?
+---@param lang string
+---@param line_map table<integer, integer>
+---@param col_offset integer
+---@param covered_lines? table<integer, true>
 ---@return integer
-local function highlight_treesitter(bufnr, ns, hunk, code_lines, col_offset)
-  local lang = hunk.lang
-  if not lang then
-    return 0
-  end
-
+local function highlight_treesitter(
+  bufnr,
+  ns,
+  code_lines,
+  lang,
+  line_map,
+  col_offset,
+  covered_lines
+)
   local code = table.concat(code_lines, '\n')
   if code == '' then
     return 0
@@ -79,54 +124,50 @@ local function highlight_treesitter(bufnr, ns, hunk, code_lines, col_offset)
     return 0
   end
 
-  local trees = parser_obj:parse()
+  local trees = parser_obj:parse(true)
   if not trees or #trees == 0 then
     dbg('parse returned no trees for lang: %s', lang)
     return 0
   end
 
-  local query = vim.treesitter.query.get(lang, 'highlights')
-  if not query then
-    dbg('no highlights query for lang: %s', lang)
-    return 0
-  end
-
-  if hunk.header_context and hunk.header_context_col then
-    local header_line = hunk.start_line - 1
-    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, header_line, hunk.header_context_col, {
-      end_col = hunk.header_context_col + #hunk.header_context,
-      hl_group = 'Normal',
-      priority = 199,
-    })
-    local header_extmarks =
-      highlight_text(bufnr, ns, hunk, hunk.header_context_col, hunk.header_context, lang)
-    if header_extmarks > 0 then
-      dbg('header %s:%d applied %d extmarks', hunk.filename, hunk.start_line, header_extmarks)
-    end
-  end
-
-  col_offset = col_offset or 1
-
   local extmark_count = 0
-  for id, node, metadata in query:iter_captures(trees[1]:root(), code) do
-    local capture_name = '@' .. query.captures[id] .. '.' .. lang
-    local sr, sc, er, ec = node:range()
+  parser_obj:for_each_tree(function(tree, ltree)
+    local tree_lang = ltree:lang()
+    local query = vim.treesitter.query.get(tree_lang, 'highlights')
+    if not query then
+      return
+    end
 
-    local buf_sr = hunk.start_line + sr
-    local buf_er = hunk.start_line + er
-    local buf_sc = sc + col_offset
-    local buf_ec = ec + col_offset
+    for id, node, metadata in query:iter_captures(tree:root(), code) do
+      local capture = query.captures[id]
+      if capture ~= 'spell' and capture ~= 'nospell' then
+        local capture_name = '@' .. capture .. '.' .. tree_lang
+        local sr, sc, er, ec = node:range()
 
-    local priority = lang == 'diff' and (tonumber(metadata.priority) or 100) or 200
+        local buf_sr = line_map[sr]
+        if buf_sr then
+          local buf_er = line_map[er] or buf_sr
 
-    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
-      end_row = buf_er,
-      end_col = buf_ec,
-      hl_group = capture_name,
-      priority = priority,
-    })
-    extmark_count = extmark_count + 1
-  end
+          local buf_sc = sc + col_offset
+          local buf_ec = ec + col_offset
+
+          local priority = tree_lang == 'diff' and (tonumber(metadata.priority) or 100)
+            or PRIORITY_SYNTAX
+
+          pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
+            end_row = buf_er,
+            end_col = buf_ec,
+            hl_group = capture_name,
+            priority = priority,
+          })
+          extmark_count = extmark_count + 1
+          if covered_lines then
+            covered_lines[buf_sr] = true
+          end
+        end
+      end
+    end
+  end)
 
   return extmark_count
 end
@@ -176,8 +217,10 @@ end
 ---@param ns integer
 ---@param hunk diffs.Hunk
 ---@param code_lines string[]
+---@param covered_lines? table<integer, true>
+---@param leading_offset? integer
 ---@return integer
-local function highlight_vim_syntax(bufnr, ns, hunk, code_lines)
+local function highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, leading_offset)
   local ft = hunk.ft
   if not ft then
     return 0
@@ -187,6 +230,8 @@ local function highlight_vim_syntax(bufnr, ns, hunk, code_lines)
     return 0
   end
 
+  leading_offset = leading_offset or 0
+
   local scratch = vim.api.nvim_create_buf(false, true)
   vim.api.nvim_buf_set_lines(scratch, 0, -1, false, code_lines)
   vim.api.nvim_set_option_value('bufhidden', 'wipe', { buf = scratch })
@@ -213,15 +258,22 @@ local function highlight_vim_syntax(bufnr, ns, hunk, code_lines)
 
   vim.api.nvim_buf_delete(scratch, { force = true })
 
+  local hunk_line_count = #hunk.lines
   local extmark_count = 0
   for _, span in ipairs(spans) do
-    local buf_line = hunk.start_line + span.line - 1
-    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
-      end_col = span.col_end,
-      hl_group = span.hl_name,
-      priority = 200,
-    })
-    extmark_count = extmark_count + 1
+    local adj = span.line - leading_offset
+    if adj >= 1 and adj <= hunk_line_count then
+      local buf_line = hunk.start_line + adj - 1
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
+        end_col = span.col_end,
+        hl_group = span.hl_name,
+        priority = PRIORITY_SYNTAX,
+      })
+      extmark_count = extmark_count + 1
+      if covered_lines then
+        covered_lines[buf_line] = true
+      end
+    end
   end
 
   return extmark_count
@@ -248,21 +300,101 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     use_vim = false
   end
 
-  local apply_syntax = use_ts or use_vim
+  ---@type table<integer, true>
+  local covered_lines = {}
 
-  ---@type string[]
-  local code_lines = {}
-  if apply_syntax then
-    for _, line in ipairs(hunk.lines) do
-      table.insert(code_lines, line:sub(2))
+  local ctx_cfg = opts.highlights.context
+  local context = (ctx_cfg and ctx_cfg.enabled) and ctx_cfg.lines or 0
+  local leading = {}
+  local trailing = {}
+  if (use_ts or use_vim) and context > 0 and hunk.file_new_start and hunk.repo_root then
+    local filepath = vim.fs.joinpath(hunk.repo_root, hunk.filename)
+    local lead_from = math.max(1, hunk.file_new_start - context)
+    local lead_count = hunk.file_new_start - lead_from
+    if lead_count > 0 then
+      leading = read_line_range(filepath, lead_from, lead_count)
     end
+    local trail_from = hunk.file_new_start + (hunk.file_new_count or 0)
+    trailing = read_line_range(filepath, trail_from, context)
   end
 
   local extmark_count = 0
   if use_ts then
-    extmark_count = highlight_treesitter(bufnr, ns, hunk, code_lines)
+    ---@type string[]
+    local new_code = {}
+    ---@type table<integer, integer>
+    local new_map = {}
+    ---@type string[]
+    local old_code = {}
+    ---@type table<integer, integer>
+    local old_map = {}
+
+    for _, pad_line in ipairs(leading) do
+      table.insert(new_code, pad_line)
+      table.insert(old_code, pad_line)
+    end
+
+    for i, line in ipairs(hunk.lines) do
+      local prefix = line:sub(1, 1)
+      local stripped = line:sub(2)
+      local buf_line = hunk.start_line + i - 1
+
+      if prefix == '+' then
+        new_map[#new_code] = buf_line
+        table.insert(new_code, stripped)
+      elseif prefix == '-' then
+        old_map[#old_code] = buf_line
+        table.insert(old_code, stripped)
+      else
+        new_map[#new_code] = buf_line
+        table.insert(new_code, stripped)
+        table.insert(old_code, stripped)
+      end
+    end
+
+    for _, pad_line in ipairs(trailing) do
+      table.insert(new_code, pad_line)
+      table.insert(old_code, pad_line)
+    end
+
+    extmark_count = highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, 1, covered_lines)
+    extmark_count = extmark_count
+      + highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, 1, covered_lines)
+
+    if hunk.header_context and hunk.header_context_col then
+      local header_line = hunk.start_line - 1
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, header_line, hunk.header_context_col, {
+        end_col = hunk.header_context_col + #hunk.header_context,
+        hl_group = 'DiffsClear',
+        priority = PRIORITY_CLEAR,
+      })
+      local header_extmarks = highlight_text(
+        bufnr,
+        ns,
+        hunk,
+        hunk.header_context_col,
+        hunk.header_context,
+        hunk.lang,
+        new_code
+      )
+      if header_extmarks > 0 then
+        dbg('header %s:%d applied %d extmarks', hunk.filename, hunk.start_line, header_extmarks)
+      end
+      extmark_count = extmark_count + header_extmarks
+    end
   elseif use_vim then
-    extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines)
+    ---@type string[]
+    local code_lines = {}
+    for _, pad_line in ipairs(leading) do
+      table.insert(code_lines, pad_line)
+    end
+    for _, line in ipairs(hunk.lines) do
+      table.insert(code_lines, line:sub(2))
+    end
+    for _, pad_line in ipairs(trailing) do
+      table.insert(code_lines, pad_line)
+    end
+    extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, #leading)
   end
 
   if
@@ -271,18 +403,15 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     and #hunk.header_lines > 0
     and opts.highlights.treesitter.enabled
   then
+    ---@type table<integer, integer>
+    local header_map = {}
+    for i = 0, #hunk.header_lines - 1 do
+      header_map[i] = hunk.header_start_line - 1 + i
+    end
     extmark_count = extmark_count
-      + highlight_treesitter(bufnr, ns, {
-        filename = hunk.filename,
-        start_line = hunk.header_start_line - 1,
-        lang = 'diff',
-        lines = hunk.header_lines,
-        header_lines = {},
-      }, hunk.header_lines, 0)
+      + highlight_treesitter(bufnr, ns, hunk.header_lines, 'diff', header_map, 0)
   end
 
-  local syntax_applied = extmark_count > 0
-
   ---@type diffs.IntraChanges?
   local intra = nil
   local intra_cfg = opts.highlights.intra
@@ -334,22 +463,27 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       })
     end
 
-    if line_len > 1 and syntax_applied then
+    if line_len > 1 and covered_lines[buf_line] then
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 1, {
         end_col = line_len,
-        hl_group = 'Normal',
-        priority = 198,
+        hl_group = 'DiffsClear',
+        priority = PRIORITY_CLEAR,
       })
     end
 
     if opts.highlights.background and is_diff_line then
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-        end_col = line_len,
+        end_row = buf_line + 1,
         hl_group = line_hl,
         hl_eol = true,
-        number_hl_group = opts.highlights.gutter and number_hl or nil,
-        priority = 199,
+        priority = PRIORITY_LINE_BG,
       })
+      if opts.highlights.gutter then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
+          number_hl_group = number_hl,
+          priority = PRIORITY_LINE_BG,
+        })
+      end
     end
 
     if char_spans_by_line[i] then
@@ -367,7 +501,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
         local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
           end_col = span.col_end,
           hl_group = char_hl,
-          priority = 201,
+          priority = PRIORITY_CHAR_BG,
         })
         if not ok then
           dbg('char extmark FAILED: %s', err)

lua/diffs/init.lua

@@ -11,9 +11,16 @@
 ---@field algorithm string
 ---@field max_lines integer
 
+---@class diffs.ContextConfig
+---@field enabled boolean
+---@field lines integer
+
 ---@class diffs.Highlights
 ---@field background boolean
 ---@field gutter boolean
+---@field blend_alpha? number
+---@field overrides? table<string, table>
+---@field context diffs.ContextConfig
 ---@field treesitter diffs.TreesitterConfig
 ---@field vim diffs.VimConfig
 ---@field intra diffs.IntraConfig
@@ -22,12 +29,27 @@
 ---@field horizontal string|false
 ---@field vertical string|false
 
+---@class diffs.ConflictKeymaps
+---@field ours string|false
+---@field theirs string|false
+---@field both string|false
+---@field none string|false
+---@field next string|false
+---@field prev string|false
+
+---@class diffs.ConflictConfig
+---@field enabled boolean
+---@field disable_diagnostics boolean
+---@field show_virtual_text boolean
+---@field keymaps diffs.ConflictKeymaps
+
 ---@class diffs.Config
 ---@field debug boolean
 ---@field debounce_ms integer
 ---@field hide_prefix boolean
 ---@field highlights diffs.Highlights
 ---@field fugitive diffs.FugitiveConfig
+---@field conflict diffs.ConflictConfig
 
 ---@class diffs
 ---@field attach fun(bufnr?: integer)
@@ -80,6 +102,10 @@ local default_config = {
   highlights = {
     background = true,
     gutter = true,
+    context = {
+      enabled = true,
+      lines = 25,
+    },
     treesitter = {
       enabled = true,
       max_lines = 500,
@@ -98,6 +124,19 @@ local default_config = {
     horizontal = 'du',
     vertical = 'dU',
   },
+  conflict = {
+    enabled = true,
+    disable_diagnostics = true,
+    show_virtual_text = true,
+    keymaps = {
+      ours = 'doo',
+      theirs = 'dot',
+      both = 'dob',
+      none = 'don',
+      next = ']x',
+      prev = '[x',
+    },
+  },
 }
 
 ---@type diffs.Config
@@ -183,13 +222,19 @@ local function compute_highlight_groups()
   local blended_add = blend_color(add_bg, bg, 0.4)
   local blended_del = blend_color(del_bg, bg, 0.4)
 
-  local blended_add_text = blend_color(add_fg, bg, 0.7)
-  local blended_del_text = blend_color(del_fg, bg, 0.7)
+  local alpha = config.highlights.blend_alpha or 0.6
+  local blended_add_text = blend_color(add_fg, bg, alpha)
+  local blended_del_text = blend_color(del_fg, bg, alpha)
 
+  vim.api.nvim_set_hl(0, 'DiffsClear', { default = true, fg = normal.fg or 0xc0c0c0 })
   vim.api.nvim_set_hl(0, 'DiffsAdd', { default = true, bg = blended_add })
   vim.api.nvim_set_hl(0, 'DiffsDelete', { default = true, bg = blended_del })
-  vim.api.nvim_set_hl(0, 'DiffsAddNr', { default = true, fg = add_fg, bg = blended_add })
-  vim.api.nvim_set_hl(0, 'DiffsDeleteNr', { default = true, fg = del_fg, bg = blended_del })
+  vim.api.nvim_set_hl(0, 'DiffsAddNr', { default = true, fg = blended_add_text, bg = blended_add })
+  vim.api.nvim_set_hl(
+    0,
+    'DiffsDeleteNr',
+    { default = true, fg = blended_del_text, bg = blended_del }
+  )
   vim.api.nvim_set_hl(0, 'DiffsAddText', { default = true, bg = blended_add_text })
   vim.api.nvim_set_hl(0, 'DiffsDeleteText', { default = true, bg = blended_del_text })
 
@@ -205,10 +250,51 @@ local function compute_highlight_groups()
   local diff_change = resolve_hl('DiffChange')
   local diff_text = resolve_hl('DiffText')
 
-  vim.api.nvim_set_hl(0, 'DiffsDiffAdd', { bg = diff_add.bg })
-  vim.api.nvim_set_hl(0, 'DiffsDiffDelete', { fg = diff_delete.fg, bg = diff_delete.bg })
-  vim.api.nvim_set_hl(0, 'DiffsDiffChange', { bg = diff_change.bg })
-  vim.api.nvim_set_hl(0, 'DiffsDiffText', { bg = diff_text.bg })
+  vim.api.nvim_set_hl(0, 'DiffsDiffAdd', { default = true, bg = diff_add.bg })
+  vim.api.nvim_set_hl(
+    0,
+    'DiffsDiffDelete',
+    { default = true, fg = diff_delete.fg, bg = diff_delete.bg }
+  )
+  vim.api.nvim_set_hl(0, 'DiffsDiffChange', { default = true, bg = diff_change.bg })
+  vim.api.nvim_set_hl(0, 'DiffsDiffText', { default = true, bg = diff_text.bg })
+
+  local change_bg = diff_change.bg or 0x3a3a4a
+  local text_bg = diff_text.bg or 0x4a4a5a
+  local change_fg = diff_change.fg or diff_text.fg or 0x80a0c0
+
+  local blended_ours = blend_color(add_bg, bg, 0.4)
+  local blended_theirs = blend_color(change_bg, bg, 0.4)
+  local blended_base = blend_color(text_bg, bg, 0.3)
+  local blended_ours_nr = blend_color(add_fg, bg, alpha)
+  local blended_theirs_nr = blend_color(change_fg, bg, alpha)
+  local blended_base_nr = blend_color(change_fg, bg, 0.4)
+
+  vim.api.nvim_set_hl(0, 'DiffsConflictOurs', { default = true, bg = blended_ours })
+  vim.api.nvim_set_hl(0, 'DiffsConflictTheirs', { default = true, bg = blended_theirs })
+  vim.api.nvim_set_hl(0, 'DiffsConflictBase', { default = true, bg = blended_base })
+  vim.api.nvim_set_hl(0, 'DiffsConflictMarker', { default = true, fg = 0x808080, bold = true })
+  vim.api.nvim_set_hl(
+    0,
+    'DiffsConflictOursNr',
+    { default = true, fg = blended_ours_nr, bg = blended_ours }
+  )
+  vim.api.nvim_set_hl(
+    0,
+    'DiffsConflictTheirsNr',
+    { default = true, fg = blended_theirs_nr, bg = blended_theirs }
+  )
+  vim.api.nvim_set_hl(
+    0,
+    'DiffsConflictBaseNr',
+    { default = true, fg = blended_base_nr, bg = blended_base }
+  )
+
+  if config.highlights.overrides then
+    for group, hl in pairs(config.highlights.overrides) do
+      vim.api.nvim_set_hl(0, group, hl)
+    end
+  end
 end
 
 local function init()
@@ -230,11 +316,21 @@ local function init()
     vim.validate({
       ['highlights.background'] = { opts.highlights.background, 'boolean', true },
       ['highlights.gutter'] = { opts.highlights.gutter, 'boolean', true },
+      ['highlights.blend_alpha'] = { opts.highlights.blend_alpha, 'number', true },
+      ['highlights.overrides'] = { opts.highlights.overrides, 'table', true },
+      ['highlights.context'] = { opts.highlights.context, 'table', true },
       ['highlights.treesitter'] = { opts.highlights.treesitter, 'table', true },
       ['highlights.vim'] = { opts.highlights.vim, 'table', true },
       ['highlights.intra'] = { opts.highlights.intra, 'table', true },
     })
 
+    if opts.highlights.context then
+      vim.validate({
+        ['highlights.context.enabled'] = { opts.highlights.context.enabled, 'boolean', true },
+        ['highlights.context.lines'] = { opts.highlights.context.lines, 'number', true },
+      })
+    end
+
     if opts.highlights.treesitter then
       vim.validate({
         ['highlights.treesitter.enabled'] = { opts.highlights.treesitter.enabled, 'boolean', true },
@@ -287,9 +383,41 @@ local function init()
     })
   end
 
+  if opts.conflict then
+    vim.validate({
+      ['conflict.enabled'] = { opts.conflict.enabled, 'boolean', true },
+      ['conflict.disable_diagnostics'] = { opts.conflict.disable_diagnostics, 'boolean', true },
+      ['conflict.show_virtual_text'] = { opts.conflict.show_virtual_text, 'boolean', true },
+      ['conflict.keymaps'] = { opts.conflict.keymaps, 'table', true },
+    })
+
+    if opts.conflict.keymaps then
+      local keymap_validator = function(v)
+        return v == false or type(v) == 'string'
+      end
+      for _, key in ipairs({ 'ours', 'theirs', 'both', 'none', 'next', 'prev' }) do
+        vim.validate({
+          ['conflict.keymaps.' .. key] = {
+            opts.conflict.keymaps[key],
+            keymap_validator,
+            'string or false',
+          },
+        })
+      end
+    end
+  end
+
   if opts.debounce_ms and opts.debounce_ms < 0 then
     error('diffs: debounce_ms must be >= 0')
   end
+  if
+    opts.highlights
+    and opts.highlights.context
+    and opts.highlights.context.lines
+    and opts.highlights.context.lines < 0
+  then
+    error('diffs: highlights.context.lines must be >= 0')
+  end
   if
     opts.highlights
     and opts.highlights.treesitter
@@ -314,6 +442,13 @@ local function init()
   then
     error('diffs: highlights.intra.max_lines must be >= 1')
   end
+  if
+    opts.highlights
+    and opts.highlights.blend_alpha
+    and (opts.highlights.blend_alpha < 0 or opts.highlights.blend_alpha > 1)
+  then
+    error('diffs: highlights.blend_alpha must be >= 0 and <= 1')
+  end
 
   config = vim.tbl_deep_extend('force', default_config, opts)
   log.set_enabled(config.debug)
@@ -436,4 +571,10 @@ function M.get_fugitive_config()
   return config.fugitive
 end
 
+---@return diffs.ConflictConfig
+function M.get_conflict_config()
+  init()
+  return config.conflict
+end
+
 return M

lua/diffs/parser.lua

@@ -8,6 +8,11 @@
 ---@field lines string[]
 ---@field header_start_line integer?
 ---@field header_lines string[]?
+---@field file_old_start integer?
+---@field file_old_count integer?
+---@field file_new_start integer?
+---@field file_new_count integer?
+---@field repo_root string?
 
 local M = {}
 
@@ -132,6 +137,14 @@ function M.parse_buffer(bufnr)
   local header_start = nil
   ---@type string[]
   local header_lines = {}
+  ---@type integer?
+  local file_old_start = nil
+  ---@type integer?
+  local file_old_count = nil
+  ---@type integer?
+  local file_new_start = nil
+  ---@type integer?
+  local file_new_count = nil
 
   local function flush_hunk()
     if hunk_start and #hunk_lines > 0 then
@@ -143,6 +156,11 @@ function M.parse_buffer(bufnr)
         header_context = hunk_header_context,
         header_context_col = hunk_header_context_col,
         lines = hunk_lines,
+        file_old_start = file_old_start,
+        file_old_count = file_old_count,
+        file_new_start = file_new_start,
+        file_new_count = file_new_count,
+        repo_root = repo_root,
       }
       if hunk_count == 1 and header_start and #header_lines > 0 then
         hunk.header_start_line = header_start
@@ -154,6 +172,10 @@ function M.parse_buffer(bufnr)
     hunk_header_context = nil
     hunk_header_context_col = nil
     hunk_lines = {}
+    file_old_start = nil
+    file_old_count = nil
+    file_new_start = nil
+    file_new_count = nil
   end
 
   for i, line in ipairs(lines) do
@@ -174,6 +196,13 @@ function M.parse_buffer(bufnr)
     elseif line:match('^@@.-@@') then
       flush_hunk()
       hunk_start = i
+      local hs, hc, hs2, hc2 = line:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
+      if hs then
+        file_old_start = tonumber(hs)
+        file_old_count = tonumber(hc) or 1
+        file_new_start = tonumber(hs2)
+        file_new_count = tonumber(hc2) or 1
+      end
       local prefix, context = line:match('^(@@.-@@%s*)(.*)')
       if context and context ~= '' then
         hunk_header_context = context

plugin/diffs.lua

@@ -30,6 +30,15 @@ vim.api.nvim_create_autocmd('BufReadCmd', {
   end,
 })
 
+vim.api.nvim_create_autocmd('BufReadPost', {
+  callback = function(args)
+    local conflict_config = require('diffs').get_conflict_config()
+    if conflict_config.enabled then
+      require('diffs.conflict').attach(args.buf, conflict_config)
+    end
+  end,
+})
+
 vim.api.nvim_create_autocmd('OptionSet', {
   pattern = 'diff',
   callback = function()
@@ -40,3 +49,36 @@ vim.api.nvim_create_autocmd('OptionSet', {
     end
   end,
 })
+
+local cmds = require('diffs.commands')
+vim.keymap.set('n', '<Plug>(diffs-gdiff)', function()
+  cmds.gdiff(nil, false)
+end, { desc = 'Unified diff (horizontal)' })
+vim.keymap.set('n', '<Plug>(diffs-gvdiff)', function()
+  cmds.gdiff(nil, true)
+end, { desc = 'Unified diff (vertical)' })
+
+local function conflict_action(fn)
+  local bufnr = vim.api.nvim_get_current_buf()
+  local config = require('diffs').get_conflict_config()
+  fn(bufnr, config)
+end
+
+vim.keymap.set('n', '<Plug>(diffs-conflict-ours)', function()
+  conflict_action(require('diffs.conflict').resolve_ours)
+end, { desc = 'Accept current (ours) change' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-theirs)', function()
+  conflict_action(require('diffs.conflict').resolve_theirs)
+end, { desc = 'Accept incoming (theirs) change' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-both)', function()
+  conflict_action(require('diffs.conflict').resolve_both)
+end, { desc = 'Accept both changes' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-none)', function()
+  conflict_action(require('diffs.conflict').resolve_none)
+end, { desc = 'Reject both changes' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-next)', function()
+  require('diffs.conflict').goto_next(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to next conflict' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-prev)', function()
+  require('diffs.conflict').goto_prev(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to previous conflict' })

spec/conflict_spec.lua

@@ -0,0 +1,688 @@
+local conflict = require('diffs.conflict')
+local helpers = require('spec.helpers')
+
+local function default_config(overrides)
+  local cfg = {
+    enabled = true,
+    disable_diagnostics = false,
+    show_virtual_text = true,
+    keymaps = {
+      ours = 'doo',
+      theirs = 'dot',
+      both = 'dob',
+      none = 'don',
+      next = ']x',
+      prev = '[x',
+    },
+  }
+  if overrides then
+    cfg = vim.tbl_deep_extend('force', cfg, overrides)
+  end
+  return cfg
+end
+
+local function create_file_buffer(lines)
+  local bufnr = vim.api.nvim_create_buf(false, false)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+  return bufnr
+end
+
+local function get_extmarks(bufnr)
+  return vim.api.nvim_buf_get_extmarks(bufnr, conflict.get_namespace(), 0, -1, { details = true })
+end
+
+describe('conflict', function()
+  describe('parse', function()
+    it('parses a single conflict', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+      assert.are.equal(0, regions[1].marker_ours)
+      assert.are.equal(1, regions[1].ours_start)
+      assert.are.equal(2, regions[1].ours_end)
+      assert.are.equal(2, regions[1].marker_sep)
+      assert.are.equal(3, regions[1].theirs_start)
+      assert.are.equal(4, regions[1].theirs_end)
+      assert.are.equal(4, regions[1].marker_theirs)
+    end)
+
+    it('parses multiple conflicts', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+        'normal line',
+        '<<<<<<< HEAD',
+        'c',
+        '=======',
+        'd',
+        '>>>>>>> feat',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(2, #regions)
+      assert.are.equal(0, regions[1].marker_ours)
+      assert.are.equal(6, regions[2].marker_ours)
+    end)
+
+    it('parses diff3 format', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '||||||| base',
+        'local x = 0',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+      assert.are.equal(2, regions[1].marker_base)
+      assert.are.equal(3, regions[1].base_start)
+      assert.are.equal(4, regions[1].base_end)
+    end)
+
+    it('handles empty ours section', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+      assert.are.equal(1, regions[1].ours_start)
+      assert.are.equal(1, regions[1].ours_end)
+    end)
+
+    it('handles empty theirs section', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+      assert.are.equal(3, regions[1].theirs_start)
+      assert.are.equal(3, regions[1].theirs_end)
+    end)
+
+    it('returns empty for no markers', function()
+      local lines = { 'local x = 1', 'local y = 2' }
+      local regions = conflict.parse(lines)
+      assert.are.equal(0, #regions)
+    end)
+
+    it('discards malformed markers (no separator)', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(0, #regions)
+    end)
+
+    it('discards malformed markers (no end)', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(0, #regions)
+    end)
+
+    it('handles trailing text on marker lines', function()
+      local lines = {
+        '<<<<<<< HEAD (some text)',
+        'local x = 1',
+        '======= extra',
+        'local x = 2',
+        '>>>>>>> feature-branch/some-thing',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+    end)
+
+    it('handles empty base in diff3', function()
+      local lines = {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '||||||| base',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }
+      local regions = conflict.parse(lines)
+      assert.are.equal(1, #regions)
+      assert.are.equal(3, regions[1].base_start)
+      assert.are.equal(3, regions[1].base_end)
+    end)
+  end)
+
+  describe('highlighting', function()
+    after_each(function()
+      conflict.detach(vim.api.nvim_get_current_buf())
+    end)
+
+    it('applies extmarks for conflict regions', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config())
+
+      local extmarks = get_extmarks(bufnr)
+      assert.is_true(#extmarks > 0)
+
+      local has_ours = false
+      local has_theirs = false
+      local has_marker = false
+      for _, mark in ipairs(extmarks) do
+        local hl = mark[4] and mark[4].hl_group
+        if hl == 'DiffsConflictOurs' then
+          has_ours = true
+        end
+        if hl == 'DiffsConflictTheirs' then
+          has_theirs = true
+        end
+        if hl == 'DiffsConflictMarker' then
+          has_marker = true
+        end
+      end
+      assert.is_true(has_ours)
+      assert.is_true(has_theirs)
+      assert.is_true(has_marker)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('applies virtual text when enabled', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config({ show_virtual_text = true }))
+
+      local extmarks = get_extmarks(bufnr)
+      local virt_text_count = 0
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          virt_text_count = virt_text_count + 1
+        end
+      end
+      assert.are.equal(2, virt_text_count)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('does not apply virtual text when disabled', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config({ show_virtual_text = false }))
+
+      local extmarks = get_extmarks(bufnr)
+      local virt_text_count = 0
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          virt_text_count = virt_text_count + 1
+        end
+      end
+      assert.are.equal(0, virt_text_count)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('applies number_hl_group to content lines', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config())
+
+      local extmarks = get_extmarks(bufnr)
+      local has_ours_nr = false
+      local has_theirs_nr = false
+      for _, mark in ipairs(extmarks) do
+        local nr = mark[4] and mark[4].number_hl_group
+        if nr == 'DiffsConflictOursNr' then
+          has_ours_nr = true
+        end
+        if nr == 'DiffsConflictTheirsNr' then
+          has_theirs_nr = true
+        end
+      end
+      assert.is_true(has_ours_nr)
+      assert.is_true(has_theirs_nr)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('highlights base region in diff3', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '||||||| base',
+        'local x = 0',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config())
+
+      local extmarks = get_extmarks(bufnr)
+      local has_base = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group == 'DiffsConflictBase' then
+          has_base = true
+          break
+        end
+      end
+      assert.is_true(has_base)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('clears extmarks on detach', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config())
+      assert.is_true(#get_extmarks(bufnr) > 0)
+
+      conflict.detach(bufnr)
+      assert.are.equal(0, #get_extmarks(bufnr))
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('resolution', function()
+    local function make_conflict_buffer()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      return bufnr
+    end
+
+    it('resolve_ours keeps ours content', function()
+      local bufnr = make_conflict_buffer()
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_ours(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('local x = 1', lines[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('resolve_theirs keeps theirs content', function()
+      local bufnr = make_conflict_buffer()
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_theirs(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('local x = 2', lines[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('resolve_both keeps ours then theirs', function()
+      local bufnr = make_conflict_buffer()
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_both(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(2, #lines)
+      assert.are.equal('local x = 1', lines[1])
+      assert.are.equal('local x = 2', lines[2])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('resolve_none removes entire block', function()
+      local bufnr = make_conflict_buffer()
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_none(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('', lines[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('does nothing when cursor is outside conflict', function()
+      local bufnr = create_file_buffer({
+        'normal line',
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      conflict.resolve_ours(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(6, #lines)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('resolves one conflict among multiple', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+        'middle',
+        '<<<<<<< HEAD',
+        'c',
+        '=======',
+        'd',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_ours(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal('a', lines[1])
+      assert.are.equal('middle', lines[2])
+      assert.are.equal('<<<<<<< HEAD', lines[3])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('resolve_ours with empty ours section', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      conflict.resolve_ours(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('', lines[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('handles diff3 resolution (ignores base)', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '||||||| base',
+        'local x = 0',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+      conflict.resolve_theirs(bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('local x = 2', lines[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('navigation', function()
+    it('goto_next jumps to next conflict', function()
+      local bufnr = create_file_buffer({
+        'normal',
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+        'middle',
+        '<<<<<<< HEAD',
+        'c',
+        '=======',
+        'd',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      conflict.goto_next(bufnr)
+      assert.are.equal(2, vim.api.nvim_win_get_cursor(0)[1])
+
+      conflict.goto_next(bufnr)
+      assert.are.equal(8, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('goto_next wraps to first conflict', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      conflict.goto_next(bufnr)
+      assert.are.equal(1, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('goto_prev jumps to previous conflict', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+        'middle',
+        '<<<<<<< HEAD',
+        'c',
+        '=======',
+        'd',
+        '>>>>>>> feat',
+        'end',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 12, 0 })
+
+      conflict.goto_prev(bufnr)
+      assert.are.equal(7, vim.api.nvim_win_get_cursor(0)[1])
+
+      conflict.goto_prev(bufnr)
+      assert.are.equal(1, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('goto_prev wraps to last conflict', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      conflict.goto_prev(bufnr)
+      assert.are.equal(1, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('goto_next does nothing with no conflicts', function()
+      local bufnr = create_file_buffer({ 'normal line' })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      conflict.goto_next(bufnr)
+      assert.are.equal(1, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('lifecycle', function()
+    it('attach is idempotent', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      local cfg = default_config()
+      conflict.attach(bufnr, cfg)
+      local count1 = #get_extmarks(bufnr)
+      conflict.attach(bufnr, cfg)
+      local count2 = #get_extmarks(bufnr)
+      assert.are.equal(count1, count2)
+      conflict.detach(bufnr)
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('skips non-file buffers', function()
+      local bufnr = helpers.create_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_option_value('buftype', 'nofile', { buf = bufnr })
+
+      conflict.attach(bufnr, default_config())
+      assert.are.equal(0, #get_extmarks(bufnr))
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('skips buffers without conflict markers', function()
+      local bufnr = create_file_buffer({ 'local x = 1', 'local y = 2' })
+
+      conflict.attach(bufnr, default_config())
+      assert.are.equal(0, #get_extmarks(bufnr))
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('re-highlights when markers return after resolution', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      local cfg = default_config()
+      conflict.attach(bufnr, cfg)
+
+      assert.is_true(#get_extmarks(bufnr) > 0)
+
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+      conflict.resolve_ours(bufnr, cfg)
+      assert.are.equal(0, #get_extmarks(bufnr))
+
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, {
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_exec_autocmds('TextChanged', { buffer = bufnr })
+
+      assert.is_true(#get_extmarks(bufnr) > 0)
+
+      conflict.detach(bufnr)
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('detaches after last conflict resolved', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      conflict.attach(bufnr, default_config())
+
+      assert.is_true(#get_extmarks(bufnr) > 0)
+
+      vim.api.nvim_win_set_cursor(0, { 2, 0 })
+      conflict.resolve_ours(bufnr, default_config())
+
+      assert.are.equal(0, #get_extmarks(bufnr))
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/helpers.lua

@@ -12,6 +12,7 @@ local function ensure_parser(lang)
 end
 
 ensure_parser('lua')
+ensure_parser('vim')
 
 local M = {}
 

spec/highlight_spec.lua

@@ -7,8 +7,10 @@ describe('highlight', function()
 
     before_each(function()
       ns = vim.api.nvim_create_namespace('diffs_test')
+      local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
       local diff_add = vim.api.nvim_get_hl(0, { name = 'DiffAdd' })
       local diff_delete = vim.api.nvim_get_hl(0, { name = 'DiffDelete' })
+      vim.api.nvim_set_hl(0, 'DiffsClear', { fg = normal.fg or 0xc0c0c0 })
       vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = diff_add.bg })
       vim.api.nvim_set_hl(0, 'DiffsDelete', { bg = diff_delete.bg })
     end)
@@ -35,6 +37,7 @@ describe('highlight', function()
         highlights = {
           background = false,
           gutter = false,
+          context = { enabled = false, lines = 0 },
           treesitter = {
             enabled = true,
             max_lines = 500,
@@ -82,7 +85,7 @@ describe('highlight', function()
       delete_buffer(bufnr)
     end)
 
-    it('applies Normal extmarks to clear diff colors', function()
+    it('applies DiffsClear extmarks to clear diff colors', function()
       local bufnr = create_buffer({
         '@@ -1,1 +1,2 @@',
         ' local x = 1',
@@ -99,14 +102,46 @@ describe('highlight', function()
       highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
 
       local extmarks = get_extmarks(bufnr)
-      local has_normal = false
+      local has_clear = false
       for _, mark in ipairs(extmarks) do
-        if mark[4] and mark[4].hl_group == 'Normal' then
-          has_normal = true
+        if mark[4] and mark[4].hl_group == 'DiffsClear' then
+          has_clear = true
           break
         end
       end
-      assert.is_true(has_normal)
+      assert.is_true(has_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('produces treesitter captures on all lines with split parsing', function()
+      local bufnr = create_buffer({
+        '@@ -1,3 +1,3 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        ' return x',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '-local y = 2', '+local y = 3', ' return x' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local lines_with_ts = {}
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group and mark[4].hl_group:match('^@.*%.lua$') then
+          lines_with_ts[mark[2]] = true
+        end
+      end
+      assert.is_true(lines_with_ts[1] ~= nil)
+      assert.is_true(lines_with_ts[2] ~= nil)
+      assert.is_true(lines_with_ts[3] ~= nil)
+      assert.is_true(lines_with_ts[4] ~= nil)
       delete_buffer(bufnr)
     end)
 
@@ -185,6 +220,40 @@ describe('highlight', function()
       delete_buffer(bufnr)
     end)
 
+    it('highlights function keyword in header context', function()
+      local bufnr = create_buffer({
+        '@@ -5,3 +5,4 @@ function M.setup()',
+        ' local x = 1',
+        '+local y = 2',
+        ' return x',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        header_context = 'function M.setup()',
+        header_context_col = 18,
+        lines = { ' local x = 1', '+local y = 2', ' return x' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local has_keyword_function = false
+      for _, mark in ipairs(extmarks) do
+        if mark[2] == 0 and mark[4] and mark[4].hl_group then
+          local hl = mark[4].hl_group
+          if hl == '@keyword.function.lua' or hl == '@keyword.lua' then
+            has_keyword_function = true
+            break
+          end
+        end
+      end
+      assert.is_true(has_keyword_function)
+      delete_buffer(bufnr)
+    end)
+
     it('does not highlight header when no header_context', function()
       local bufnr = create_buffer({
         '@@ -10,3 +10,4 @@',
@@ -576,7 +645,7 @@ describe('highlight', function()
       local extmarks = get_extmarks(bufnr)
       local has_syntax_hl = false
       for _, mark in ipairs(extmarks) do
-        if mark[4] and mark[4].hl_group and mark[4].hl_group ~= 'Normal' then
+        if mark[4] and mark[4].hl_group and mark[4].hl_group ~= 'DiffsClear' then
           has_syntax_hl = true
           break
         end
@@ -610,7 +679,7 @@ describe('highlight', function()
       local extmarks = get_extmarks(bufnr)
       local has_syntax_hl = false
       for _, mark in ipairs(extmarks) do
-        if mark[4] and mark[4].hl_group and mark[4].hl_group ~= 'Normal' then
+        if mark[4] and mark[4].hl_group and mark[4].hl_group ~= 'DiffsClear' then
           has_syntax_hl = true
           break
         end
@@ -682,7 +751,7 @@ describe('highlight', function()
       delete_buffer(bufnr)
     end)
 
-    it('applies Normal blanking for vim fallback hunks', function()
+    it('applies DiffsClear blanking for vim fallback hunks', function()
       local orig_synID = vim.fn.synID
       local orig_synIDtrans = vim.fn.synIDtrans
       local orig_synIDattr = vim.fn.synIDattr
@@ -722,14 +791,14 @@ describe('highlight', function()
       vim.fn.synIDattr = orig_synIDattr
 
       local extmarks = get_extmarks(bufnr)
-      local has_normal = false
+      local has_clear = false
       for _, mark in ipairs(extmarks) do
-        if mark[4] and mark[4].hl_group == 'Normal' then
-          has_normal = true
+        if mark[4] and mark[4].hl_group == 'DiffsClear' then
+          has_clear = true
           break
         end
       end
-      assert.is_true(has_normal)
+      assert.is_true(has_clear)
       delete_buffer(bufnr)
     end)
 
@@ -765,7 +834,7 @@ describe('highlight', function()
       delete_buffer(bufnr)
     end)
 
-    it('line bg priority > Normal priority', function()
+    it('hl_eol background extmarks are multiline so hl_eol takes effect', function()
       local bufnr = create_buffer({
         '@@ -1,2 +1,1 @@',
         '-local x = 1',
@@ -787,20 +856,86 @@ describe('highlight', function()
       )
 
       local extmarks = get_extmarks(bufnr)
-      local normal_priority = nil
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.hl_group == 'DiffsAdd' or d.hl_group == 'DiffsDelete') then
+          assert.is_true(d.end_row > mark[2])
+        end
+      end
+      delete_buffer(bufnr)
+    end)
+
+    it('number_hl_group does not bleed to adjacent lines', function()
+      local bufnr = create_buffer({
+        '@@ -1,3 +1,3 @@',
+        ' local a = 0',
+        '-local x = 1',
+        '+local y = 2',
+        ' local b = 3',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local a = 0', '-local x = 1', '+local y = 2', ' local b = 3' },
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({ highlights = { background = true, gutter = true } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.number_hl_group then
+          local start_row = mark[2]
+          local end_row = d.end_row or start_row
+          assert.are.equal(start_row, end_row)
+        end
+      end
+      delete_buffer(bufnr)
+    end)
+
+    it('line bg priority > DiffsClear priority', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,1 @@',
+        '-local x = 1',
+        '+local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '-local x = 1', '+local y = 2' },
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({ highlights = { background = true } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      local clear_priority = nil
       local line_bg_priority = nil
       for _, mark in ipairs(extmarks) do
         local d = mark[4]
-        if d and d.hl_group == 'Normal' then
-          normal_priority = d.priority
+        if d and d.hl_group == 'DiffsClear' then
+          clear_priority = d.priority
         end
         if d and (d.hl_group == 'DiffsAdd' or d.hl_group == 'DiffsDelete') then
           line_bg_priority = d.priority
         end
       end
-      assert.is_not_nil(normal_priority)
+      assert.is_not_nil(clear_priority)
       assert.is_not_nil(line_bg_priority)
-      assert.is_true(line_bg_priority > normal_priority)
+      assert.is_true(line_bg_priority > clear_priority)
       delete_buffer(bufnr)
     end)
 
@@ -960,7 +1095,7 @@ describe('highlight', function()
       delete_buffer(bufnr)
     end)
 
-    it('enforces priority order: Normal < line bg < syntax < char bg', function()
+    it('enforces priority order: DiffsClear < syntax < line bg < char bg', function()
       vim.api.nvim_set_hl(0, 'DiffsAddText', { bg = 0x00FF00 })
       vim.api.nvim_set_hl(0, 'DiffsDeleteText', { bg = 0xFF0000 })
 
@@ -990,12 +1125,12 @@ describe('highlight', function()
       )
 
       local extmarks = get_extmarks(bufnr)
-      local priorities = { normal = {}, line_bg = {}, syntax = {}, char_bg = {} }
+      local priorities = { clear = {}, line_bg = {}, syntax = {}, char_bg = {} }
       for _, mark in ipairs(extmarks) do
         local d = mark[4]
         if d then
-          if d.hl_group == 'Normal' then
-            table.insert(priorities.normal, d.priority)
+          if d.hl_group == 'DiffsClear' then
+            table.insert(priorities.clear, d.priority)
           elseif d.hl_group == 'DiffsAdd' or d.hl_group == 'DiffsDelete' then
             table.insert(priorities.line_bg, d.priority)
           elseif d.hl_group == 'DiffsAddText' or d.hl_group == 'DiffsDeleteText' then
@@ -1006,19 +1141,215 @@ describe('highlight', function()
         end
       end
 
-      assert.is_true(#priorities.normal > 0)
+      assert.is_true(#priorities.clear > 0)
       assert.is_true(#priorities.line_bg > 0)
       assert.is_true(#priorities.syntax > 0)
       assert.is_true(#priorities.char_bg > 0)
 
-      local max_normal = math.max(unpack(priorities.normal))
+      local max_clear = math.max(unpack(priorities.clear))
       local min_line_bg = math.min(unpack(priorities.line_bg))
       local min_syntax = math.min(unpack(priorities.syntax))
       local min_char_bg = math.min(unpack(priorities.char_bg))
 
-      assert.is_true(max_normal < min_line_bg)
-      assert.is_true(min_line_bg < min_syntax)
-      assert.is_true(min_syntax < min_char_bg)
+      assert.is_true(max_clear < min_syntax)
+      assert.is_true(min_syntax < min_line_bg)
+      assert.is_true(min_line_bg < min_char_bg)
+      delete_buffer(bufnr)
+    end)
+
+    it('context padding produces no extmarks on padding lines', function()
+      local repo_root = '/tmp/diffs-test-context'
+      vim.fn.mkdir(repo_root, 'p')
+
+      local f = io.open(repo_root .. '/test.lua', 'w')
+      f:write('local M = {}\n')
+      f:write('function M.hello()\n')
+      f:write('  return "hi"\n')
+      f:write('end\n')
+      f:write('return M\n')
+      f:close()
+
+      local bufnr = create_buffer({
+        '@@ -3,1 +3,2 @@',
+        ' return "hi"',
+        '+"bye"',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '  return "hi"', '+"bye"' },
+        file_old_start = 3,
+        file_old_count = 1,
+        file_new_start = 3,
+        file_new_count = 2,
+        repo_root = repo_root,
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({ highlights = { context = { enabled = true, lines = 25 } } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      for _, mark in ipairs(extmarks) do
+        local row = mark[2]
+        assert.is_true(row >= 1 and row <= 2)
+      end
+
+      delete_buffer(bufnr)
+      os.remove(repo_root .. '/test.lua')
+      vim.fn.delete(repo_root, 'rf')
+    end)
+
+    it('context disabled matches behavior without padding', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        file_new_start = 1,
+        file_new_count = 2,
+        repo_root = '/nonexistent',
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({ highlights = { context = { enabled = false, lines = 0 } } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      assert.is_true(#extmarks > 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('gracefully handles missing file for context padding', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        file_new_start = 1,
+        file_new_count = 2,
+        repo_root = '/nonexistent/path',
+      }
+
+      assert.has_no.errors(function()
+        highlight.highlight_hunk(
+          bufnr,
+          ns,
+          hunk,
+          default_opts({ highlights = { context = { enabled = true, lines = 25 } } })
+        )
+      end)
+
+      local extmarks = get_extmarks(bufnr)
+      assert.is_true(#extmarks > 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('highlights treesitter injections', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+vim.cmd([[ echo 1 ]])',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+vim.cmd([[ echo 1 ]])' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local has_vim_capture = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group and mark[4].hl_group:match('^@.*%.vim$') then
+          has_vim_capture = true
+          break
+        end
+      end
+      assert.is_true(has_vim_capture)
+      delete_buffer(bufnr)
+    end)
+
+    it('includes captures from both base and injected languages', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+vim.cmd([[ echo 1 ]])',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+vim.cmd([[ echo 1 ]])' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local has_lua = false
+      local has_vim = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group then
+          if mark[4].hl_group:match('^@.*%.lua$') then
+            has_lua = true
+          end
+          if mark[4].hl_group:match('^@.*%.vim$') then
+            has_vim = true
+          end
+        end
+      end
+      assert.is_true(has_lua)
+      assert.is_true(has_vim)
+      delete_buffer(bufnr)
+    end)
+
+    it('filters @spell and @nospell captures from injections', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+vim.cmd([[ echo 1 ]])',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+vim.cmd([[ echo 1 ]])' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group then
+          assert.is_falsy(mark[4].hl_group:match('@spell'))
+          assert.is_falsy(mark[4].hl_group:match('@nospell'))
+        end
+      end
       delete_buffer(bufnr)
     end)
   end)
@@ -1052,6 +1383,7 @@ describe('highlight', function()
         highlights = {
           background = false,
           gutter = false,
+          context = { enabled = false, lines = 0 },
           treesitter = { enabled = true, max_lines = 500 },
           vim = { enabled = false, max_lines = 200 },
         },
@@ -1208,13 +1540,14 @@ describe('highlight', function()
         highlights = {
           background = false,
           gutter = false,
+          context = { enabled = false, lines = 0 },
           treesitter = { enabled = true, max_lines = 500 },
           vim = { enabled = false, max_lines = 200 },
         },
       }
     end
 
-    it('uses priority 200 for code languages', function()
+    it('uses priority 199 for code languages', function()
       local bufnr = create_buffer({
         '@@ -1,1 +1,2 @@',
         ' local x = 1',
@@ -1231,16 +1564,16 @@ describe('highlight', function()
       highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
 
       local extmarks = get_extmarks(bufnr)
-      local has_priority_200 = false
+      local has_priority_199 = false
       for _, mark in ipairs(extmarks) do
         if mark[4] and mark[4].hl_group and mark[4].hl_group:match('^@.*%.lua$') then
-          if mark[4].priority == 200 then
-            has_priority_200 = true
+          if mark[4].priority == 199 then
+            has_priority_199 = true
             break
           end
         end
       end
-      assert.is_true(has_priority_200)
+      assert.is_true(has_priority_199)
       delete_buffer(bufnr)
     end)
 
@@ -1278,7 +1611,7 @@ describe('highlight', function()
       end
       assert.is_true(#diff_extmark_priorities > 0)
       for _, priority in ipairs(diff_extmark_priorities) do
-        assert.is_true(priority < 200)
+        assert.is_true(priority < 199)
       end
       delete_buffer(bufnr)
     end)

spec/parser_spec.lua

@@ -421,5 +421,84 @@ describe('parser', function()
       os.remove(file_path)
       vim.fn.delete(repo_root, 'rf')
     end)
+
+    it('extracts file line numbers from @@ header', function()
+      local bufnr = create_buffer({
+        'M lua/test.lua',
+        '@@ -1,3 +1,4 @@',
+        ' local M = {}',
+        '+local new = true',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(1, hunks[1].file_old_start)
+      assert.are.equal(3, hunks[1].file_old_count)
+      assert.are.equal(1, hunks[1].file_new_start)
+      assert.are.equal(4, hunks[1].file_new_count)
+      delete_buffer(bufnr)
+    end)
+
+    it('extracts large line numbers from @@ header', function()
+      local bufnr = create_buffer({
+        'M lua/test.lua',
+        '@@ -100,20 +200,30 @@',
+        ' local M = {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(100, hunks[1].file_old_start)
+      assert.are.equal(20, hunks[1].file_old_count)
+      assert.are.equal(200, hunks[1].file_new_start)
+      assert.are.equal(30, hunks[1].file_new_count)
+      delete_buffer(bufnr)
+    end)
+
+    it('defaults count to 1 when omitted in @@ header', function()
+      local bufnr = create_buffer({
+        'M lua/test.lua',
+        '@@ -1 +1 @@',
+        ' local M = {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(1, hunks[1].file_old_start)
+      assert.are.equal(1, hunks[1].file_old_count)
+      assert.are.equal(1, hunks[1].file_new_start)
+      assert.are.equal(1, hunks[1].file_new_count)
+      delete_buffer(bufnr)
+    end)
+
+    it('stores repo_root on hunk when available', function()
+      local bufnr = create_buffer({
+        'M lua/test.lua',
+        '@@ -1,3 +1,4 @@',
+        ' local M = {}',
+        '+local new = true',
+        ' return M',
+      })
+      vim.api.nvim_buf_set_var(bufnr, 'diffs_repo_root', '/tmp/test-repo')
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('/tmp/test-repo', hunks[1].repo_root)
+      delete_buffer(bufnr)
+    end)
+
+    it('repo_root is nil when not available', function()
+      local bufnr = create_buffer({
+        'M lua/test.lua',
+        '@@ -1,3 +1,4 @@',
+        ' local M = {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.is_nil(hunks[1].repo_root)
+      delete_buffer(bufnr)
+    end)
   end)
 end)

spec/ux_spec.lua

@@ -0,0 +1,135 @@
+local commands = require('diffs.commands')
+local helpers = require('spec.helpers')
+
+local counter = 0
+
+local function create_diffs_buffer(name)
+  counter = counter + 1
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, {
+    'diff --git a/file.lua b/file.lua',
+    '--- a/file.lua',
+    '+++ b/file.lua',
+    '@@ -1,1 +1,2 @@',
+    ' local x = 1',
+    '+local y = 2',
+  })
+  vim.api.nvim_set_option_value('buftype', 'nowrite', { buf = bufnr })
+  vim.api.nvim_set_option_value('bufhidden', 'wipe', { buf = bufnr })
+  vim.api.nvim_set_option_value('swapfile', false, { buf = bufnr })
+  vim.api.nvim_set_option_value('modifiable', false, { buf = bufnr })
+  vim.api.nvim_set_option_value('filetype', 'diff', { buf = bufnr })
+  vim.api.nvim_buf_set_name(bufnr, name or ('diffs://unstaged:file_' .. counter .. '.lua'))
+  return bufnr
+end
+
+describe('ux', function()
+  describe('diagnostics', function()
+    it('disables diagnostics on diff buffers', function()
+      local bufnr = create_diffs_buffer()
+      commands.setup_diff_buf(bufnr)
+
+      assert.is_false(vim.diagnostic.is_enabled({ bufnr = bufnr }))
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end)
+
+    it('does not affect other buffers', function()
+      local diff_buf = create_diffs_buffer()
+      local normal_buf = helpers.create_buffer({ 'hello' })
+
+      commands.setup_diff_buf(diff_buf)
+
+      assert.is_true(vim.diagnostic.is_enabled({ bufnr = normal_buf }))
+      vim.api.nvim_buf_delete(diff_buf, { force = true })
+      helpers.delete_buffer(normal_buf)
+    end)
+  end)
+
+  describe('q keymap', function()
+    it('sets q keymap on diff buffer', function()
+      local bufnr = create_diffs_buffer()
+      commands.setup_diff_buf(bufnr)
+
+      local keymaps = vim.api.nvim_buf_get_keymap(bufnr, 'n')
+      local has_q = false
+      for _, km in ipairs(keymaps) do
+        if km.lhs == 'q' then
+          has_q = true
+          break
+        end
+      end
+      assert.is_true(has_q)
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end)
+
+    it('q closes the window', function()
+      local bufnr = create_diffs_buffer()
+      commands.setup_diff_buf(bufnr)
+
+      vim.cmd('split')
+      local win = vim.api.nvim_get_current_win()
+      vim.api.nvim_win_set_buf(win, bufnr)
+
+      local win_count_before = #vim.api.nvim_tabpage_list_wins(0)
+
+      vim.api.nvim_buf_call(bufnr, function()
+        vim.cmd('normal q')
+      end)
+
+      local win_count_after = #vim.api.nvim_tabpage_list_wins(0)
+      assert.equals(win_count_before - 1, win_count_after)
+    end)
+  end)
+
+  describe('window reuse', function()
+    it('returns nil when no diffs window exists', function()
+      local win = commands.find_diffs_window()
+      assert.is_nil(win)
+    end)
+
+    it('finds existing diffs:// window', function()
+      local bufnr = create_diffs_buffer()
+      vim.cmd('split')
+      local expected_win = vim.api.nvim_get_current_win()
+      vim.api.nvim_win_set_buf(expected_win, bufnr)
+
+      local found = commands.find_diffs_window()
+      assert.equals(expected_win, found)
+
+      vim.api.nvim_win_close(expected_win, true)
+    end)
+
+    it('ignores non-diffs buffers', function()
+      local normal_buf = helpers.create_buffer({ 'hello' })
+      vim.cmd('split')
+      local win = vim.api.nvim_get_current_win()
+      vim.api.nvim_win_set_buf(win, normal_buf)
+
+      local found = commands.find_diffs_window()
+      assert.is_nil(found)
+
+      vim.api.nvim_win_close(win, true)
+      helpers.delete_buffer(normal_buf)
+    end)
+
+    it('returns first diffs window when multiple exist', function()
+      local buf1 = create_diffs_buffer()
+      local buf2 = create_diffs_buffer()
+
+      vim.cmd('split')
+      local win1 = vim.api.nvim_get_current_win()
+      vim.api.nvim_win_set_buf(win1, buf1)
+
+      vim.cmd('split')
+      local win2 = vim.api.nvim_get_current_win()
+      vim.api.nvim_win_set_buf(win2, buf2)
+
+      local found = commands.find_diffs_window()
+      assert.is_not_nil(found)
+      assert.is_true(found == win1 or found == win2)
+
+      vim.api.nvim_win_close(win1, true)
+      vim.api.nvim_win_close(win2, true)
+    end)
+  end)
+end)