4 files changed, 25 insertions, 16 deletions
diff --git a/runtime/lua/vim/_meta/options.lua b/runtime/lua/vim/_meta/options.lua
index 36c0f583c7..c33753047f 100644
--- a/runtime/lua/vim/_meta/options.lua
+++ b/runtime/lua/vim/_meta/options.lua
@@ -7310,7 +7310,9 @@ vim.go.titleold = vim.o.titleold
 --- window.  This happens only when the 'title' option is on.
 ---
 --- When this option contains printf-style '%' items, they will be
---- expanded according to the rules used for 'statusline'.
+--- expanded according to the rules used for 'statusline'.  If it contains
+--- an invalid '%' format, the value is used as-is and no error or warning
+--- will be given when the value is set.
 --- This option cannot be set in a modeline when 'modelineexpr' is off.
 ---
 --- Example:
diff --git a/runtime/lua/vim/_meta/vimfn.lua b/runtime/lua/vim/_meta/vimfn.lua
index 4e5d3f5701..f40a94a442 100644
--- a/runtime/lua/vim/_meta/vimfn.lua
+++ b/runtime/lua/vim/_meta/vimfn.lua
@@ -10629,7 +10629,7 @@ function vim.fn.wait(timeout, condition, interval) end
 --- For example to make <c-j> work like <down> in wildmode, use: >vim
 ---     cnoremap <expr> <C-j> wildmenumode() ? "\<Down>\<Tab>" : "\<c-j>"
 --- <
---- (Note, this needs the 'wildcharm' option set appropriately).
+--- (Note: this needs the 'wildcharm' option set appropriately).
 ---
 --- @return any
 function vim.fn.wildmenumode() end
diff --git a/runtime/lua/vim/lsp/buf.lua b/runtime/lua/vim/lsp/buf.lua
index e3f4beeeb1..ccef314d86 100644
--- a/runtime/lua/vim/lsp/buf.lua
+++ b/runtime/lua/vim/lsp/buf.lua
@@ -829,11 +829,19 @@ local function on_code_action_results(results, opts)
     return
   end
 
-  ---@param item {action: lsp.Command|lsp.CodeAction}
+  ---@param item {action: lsp.Command|lsp.CodeAction, ctx: lsp.HandlerContext}
   local function format_item(item)
-    local title = item.action.title:gsub('\r\n', '\\r\\n')
-    return title:gsub('\n', '\\n')
+    local clients = vim.lsp.get_clients({ bufnr = item.ctx.bufnr })
+    local title = item.action.title:gsub('\r\n', '\\r\\n'):gsub('\n', '\\n')
+
+    if #clients == 1 then
+      return title
+    end
+
+    local source = vim.lsp.get_client_by_id(item.ctx.client_id).name
+    return ('%s [%s]'):format(title, source)
   end
+
   local select_opts = {
     prompt = 'Code actions:',
     kind = 'codeaction',
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index 76a18a409c..e3eef8901b 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -159,25 +159,24 @@ end
 ---@param encoding string utf-8|utf-16|utf-32| defaults to utf-16
 ---@return integer byte (utf-8) index of `encoding` index `index` in `line`
 function M._str_byteindex_enc(line, index, encoding)
-  local len = #line
-  if index > len then
-    -- LSP spec: if character > line length, default to the line length.
-    -- https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#position
-    return len
-  end
+  -- LSP spec: if character > line length, default to the line length.
+  -- https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#position
+  local len8 = #line
   if not encoding then
     encoding = 'utf-16'
   end
   if encoding == 'utf-8' then
-    if index then
+    if index and index <= len8 then
       return index
     else
-      return len
+      return len8
     end
-  elseif encoding == 'utf-16' then
-    return vim.str_byteindex(line, index, true)
+  end
+  local len32, len16 = vim.str_utfindex(line)
+  if encoding == 'utf-16' then
+    return index <= len16 and vim.str_byteindex(line, index, true) or len8
   elseif encoding == 'utf-32' then
-    return vim.str_byteindex(line, index)
+    return index <= len32 and vim.str_byteindex(line, index) or len8
   else
     error('Invalid encoding: ' .. vim.inspect(encoding))
   end