diff --git a/runtime/lua/editorconfig.lua b/runtime/lua/editorconfig.lua
index 12a1548ee7..b743d01a94 100644
--- a/runtime/lua/editorconfig.lua
+++ b/runtime/lua/editorconfig.lua
@@ -130,7 +130,7 @@ function properties.indent_size(bufnr, val, opts)
     vim.bo[bufnr].shiftwidth = 0
     vim.bo[bufnr].softtabstop = 0
   else
-    local n = assert(tonumber(val), 'indent_size must be a number')
+    local n = assert(vim._tointeger(val), 'indent_size must be an integer')
     vim.bo[bufnr].shiftwidth = n
     vim.bo[bufnr].softtabstop = -1
     if not opts.tab_width then
@@ -141,17 +141,17 @@ end
 
 --- The display size of a single tab character. Sets the 'tabstop' option.
 function properties.tab_width(bufnr, val)
-  vim.bo[bufnr].tabstop = assert(tonumber(val), 'tab_width must be a number')
+  vim.bo[bufnr].tabstop = assert(vim._tointeger(val), 'tab_width must be an integer')
 end
 
 --- A number indicating the maximum length of a single
 --- line. Sets the 'textwidth' option.
 function properties.max_line_length(bufnr, val)
-  local n = tonumber(val)
+  local n = vim._tointeger(val)
   if n then
     vim.bo[bufnr].textwidth = n
   else
-    assert(val == 'off', 'max_line_length must be a number or "off"')
+    assert(val == 'off', 'max_line_length must be an integer or "off"')
     vim.bo[bufnr].textwidth = 0
   end
 end
diff --git a/runtime/lua/man.lua b/runtime/lua/man.lua
index 1104e7f906..ef1e6e51eb 100644
--- a/runtime/lua/man.lua
+++ b/runtime/lua/man.lua
@@ -438,7 +438,7 @@ local function get_page(path, silent)
   if (vim.g.man_hardwrap or 1) ~= 1 then
     manwidth = 999
   elseif vim.env.MANWIDTH then
-    vim.env.MANWIDTH = tonumber(vim.env.MANWIDTH) or 0
+    vim.env.MANWIDTH = vim._tointeger(vim.env.MANWIDTH) or 0
     manwidth = math.min(vim.env.MANWIDTH, api.nvim_win_get_width(0) - vim.o.wrapmargin)
   else
     manwidth = api.nvim_win_get_width(0) - vim.o.wrapmargin
diff --git a/runtime/lua/nvim/tutor.lua b/runtime/lua/nvim/tutor.lua
index 730469f3e6..53a417f366 100644
--- a/runtime/lua/nvim/tutor.lua
+++ b/runtime/lua/nvim/tutor.lua
@@ -57,7 +57,7 @@ function M.apply_marks()
     vim.b.tutor_extmarks = {}
     for expct, _ in pairs(vim.b.tutor_metadata.expect) do
       ---@diagnostic disable-next-line: assign-type-mismatch
-      local lnum = tonumber(expct) ---@type integer
+      local lnum = vim._ensure_integer(expct)
       vim.api.nvim_buf_set_extmark(0, tutor_hl_ns, lnum - 1, 0, {
         line_hl_group = 'tutorExpect',
         invalidate = true,
diff --git a/runtime/lua/tohtml.lua b/runtime/lua/tohtml.lua
index a709d4de63..6d46a26a11 100644
--- a/runtime/lua/tohtml.lua
+++ b/runtime/lua/tohtml.lua
@@ -228,9 +228,8 @@ local function cterm_to_hex(colorstr)
   if colorstr:sub(1, 1) == '#' then
     return colorstr
   end
-  assert(colorstr ~= '')
-  local color = tonumber(colorstr) --[[@as integer]]
-  assert(color and 0 <= color and color <= 255)
+  local color = vim._ensure_integer(colorstr)
+  assert(0 <= color and color <= 255)
   if cterm_color_cache[color] then
     return cterm_color_cache[color]
   end
@@ -239,7 +238,7 @@ local function cterm_to_hex(colorstr)
     cterm_color_cache[color] = hex
   else
     notify("Couldn't get terminal colors, using fallback")
-    local t_Co = tonumber(vim.api.nvim_eval('&t_Co'))
+    local t_Co = vim._ensure_integer(vim.api.nvim_eval('&t_Co'))
     if t_Co <= 8 then
       cterm_color_cache = cterm_8_to_hex
     elseif t_Co == 88 then
@@ -744,7 +743,7 @@ local function styletable_statuscolumn(state)
     signcolumn = 'auto'
   end
   if signcolumn ~= 'no' then
-    local max = tonumber(signcolumn:match('^%w-:(%d)')) --[[@as integer?]] or 1
+    local max = vim._tointeger(signcolumn:match('^%w-:(%d)')) or 1
     if signcolumn:match('^auto') then
       --- @type table<integer,integer>
       local signcount = {}
@@ -771,7 +770,7 @@ local function styletable_statuscolumn(state)
   local foldcolumn = state.opt.foldcolumn
   if foldcolumn ~= '0' then
     if foldcolumn:match('^auto') then
-      local max = tonumber(foldcolumn:match('^%w-:(%d)')) --[[@as integer?]] or 1
+      local max = vim._tointeger(foldcolumn:match('^%w-:(%d)')) or 1
       local maxfold = 0
       vim._with({ buf = state.bufnr }, function()
         for row = state.start, state.end_ do
@@ -783,7 +782,7 @@ local function styletable_statuscolumn(state)
       end)
       minwidth = minwidth + math.min(maxfold, max)
     else
-      minwidth = minwidth + tonumber(foldcolumn) --[[@as integer]]
+      minwidth = minwidth + vim._ensure_integer(foldcolumn)
     end
   end
 
diff --git a/runtime/lua/vim/_core/defaults.lua b/runtime/lua/vim/_core/defaults.lua
index f6b4f18e61..10611be194 100644
--- a/runtime/lua/vim/_core/defaults.lua
+++ b/runtime/lua/vim/_core/defaults.lua
@@ -794,12 +794,12 @@ do
           return nil
         end
 
-        local val = tonumber(c, 16)
+        local val = vim._tointeger(c, 16)
         if not val then
           return nil
         end
 
-        local max = assert(tonumber(string.rep('f', #c), 16))
+        local max = vim._ensure_integer(string.rep('f', #c), 16)
         return val / max
       end
 
@@ -1001,9 +1001,9 @@ do
               end
 
               if
-                tonumber(params[#params - 2]) == r
-                and tonumber(params[#params - 1]) == g
-                and tonumber(params[#params]) == b
+                vim._tointeger(params[#params - 2]) == r
+                and vim._tointeger(params[#params - 1]) == g
+                and vim._tointeger(params[#params]) == b
               then
                 setoption('termguicolors', true)
               end
diff --git a/runtime/lua/vim/_core/editor.lua b/runtime/lua/vim/_core/editor.lua
index 680791c4d3..49adc6ff7e 100644
--- a/runtime/lua/vim/_core/editor.lua
+++ b/runtime/lua/vim/_core/editor.lua
@@ -1,3 +1,5 @@
+local tointeger = vim._tointeger
+
 -- Nvim-Lua stdlib: the `vim` module (:help lua-stdlib)
 --
 
@@ -74,7 +76,7 @@ function vim._os_proc_info(pid)
   local ppid_string = assert(vim.system({ 'ps', '-p', pid, '-o', 'ppid=' }):wait().stdout)
   -- Remove trailing whitespace.
   name = vim.trim(name):gsub('^.*/', '')
-  local ppid = tonumber(ppid_string) or -1
+  local ppid = tointeger(ppid_string) or -1
   return {
     name = name,
     pid = pid,
@@ -95,12 +97,9 @@ function vim._os_proc_children(ppid)
   elseif r.code ~= 0 then
     error('command failed: ' .. vim.fn.string(cmd))
   end
-  local children = {}
+  local children = {} --- @type integer[]
   for s in r.stdout:gmatch('%S+') do
-    local i = tonumber(s)
-    if i ~= nil then
-      table.insert(children, i)
-    end
+    children[#children + 1] = tointeger(s)
   end
   return children
 end
@@ -476,17 +475,17 @@ function vim.region(bufnr, pos1, pos2, regtype, inclusive)
     local c2 --- @type number
     if regtype:byte() == 22 then -- block selection: take width from regtype
       c1 = pos1[2]
-      c2 = c1 + tonumber(regtype:sub(2))
+      c2 = c1 + vim._ensure_integer(regtype:sub(2))
       -- and adjust for non-ASCII characters
       local bufline = vim.api.nvim_buf_get_lines(bufnr, l, l + 1, true)[1]
       local utflen = vim.str_utfindex(bufline, 'utf-32', #bufline)
       if c1 <= utflen then
-        c1 = assert(tonumber(vim.str_byteindex(bufline, 'utf-32', c1)))
+        c1 = vim.str_byteindex(bufline, 'utf-32', c1)
       else
         c1 = #bufline + 1
       end
       if c2 <= utflen then
-        c2 = assert(tonumber(vim.str_byteindex(bufline, 'utf-32', c2)))
+        c2 = vim.str_byteindex(bufline, 'utf-32', c2)
       else
         c2 = #bufline + 1
       end
@@ -1264,7 +1263,7 @@ function vim.deprecate(name, alternative, version, plugin, backtrace)
     -- Example: if removal `version` is 0.12 (soft-deprecated since 0.10-dev), show warnings
     -- starting at 0.11, including 0.11-dev.
     local major, minor = version:match('(%d+)%.(%d+)')
-    major, minor = tonumber(major), tonumber(minor)
+    major, minor = tointeger(major), tointeger(minor)
     local nvim_major = 0 --- Current Nvim major version.
 
     -- We can't "subtract" from a major version, so:
diff --git a/runtime/lua/vim/_core/options.lua b/runtime/lua/vim/_core/options.lua
index e98b95f837..d826df5c00 100644
--- a/runtime/lua/vim/_core/options.lua
+++ b/runtime/lua/vim/_core/options.lua
@@ -692,7 +692,7 @@ local function create_option_accessor(scope)
   local option_mt
 
   local function make_option(name, value)
-    local info = assert(get_options_info(name), 'Not a valid option name: ' .. name)
+    local info = get_options_info(name) or error('Not a valid option name: ' .. name)
 
     if type(value) == 'table' and getmetatable(value) == option_mt then
       assert(name == value._name, "must be the same value, otherwise that's weird.")
diff --git a/runtime/lua/vim/_core/shared.lua b/runtime/lua/vim/_core/shared.lua
index da50338d01..b898f0e45b 100644
--- a/runtime/lua/vim/_core/shared.lua
+++ b/runtime/lua/vim/_core/shared.lua
@@ -1620,6 +1620,35 @@ function vim._ensure_list(x)
   return { x }
 end
 
+--- Coerces {x} to an integer, like `tonumber()`, but rejects fractional values.
+---
+--- Returns `nil` if {x} cannot be converted with `tonumber()`, or if the
+--- resulting number is not integral.
+---
+--- @param x any Value to convert.
+--- @param base? integer Numeric base passed to `tonumber()`.
+--- @return integer? integer Converted integer value, or `nil`.
+function vim._tointeger(x, base)
+  --- @diagnostic disable-next-line:param-type-mismatch optional `base` is equivalent to `tonumber(x)`
+  local nx = tonumber(x, base)
+  if nx and nx == math.floor(nx) then
+    --- @cast nx integer
+    return nx
+  end
+end
+
+--- Coerces {x} to an integer and errors if conversion fails.
+---
+--- This is the throwing counterpart to |vim._tointeger()| and should be used
+--- when non-integer input is a programming error.
+---
+--- @param x any Value to convert.
+--- @param base? integer Numeric base passed to `tonumber()`.
+--- @return integer integer Converted integer value.
+function vim._ensure_integer(x, base)
+  return vim._tointeger(x, base) or error(('Cannot convert %s to integer'):format(x))
+end
+
 -- Use max 32-bit signed int value to avoid overflow on 32-bit systems. #31633
 vim._maxint = 2 ^ 32 - 1
 
diff --git a/runtime/lua/vim/deprecated/health.lua b/runtime/lua/vim/deprecated/health.lua
index eed889d90a..901a107d6f 100644
--- a/runtime/lua/vim/deprecated/health.lua
+++ b/runtime/lua/vim/deprecated/health.lua
@@ -14,7 +14,7 @@ function M.check()
 
     local version, backtraces, alternative = v[1], v[2], v[3]
     local major, minor = version:match('(%d+)%.(%d+)')
-    major, minor = tonumber(major), tonumber(minor)
+    major, minor = vim._ensure_integer(major), vim._ensure_integer(minor)
     local removal_version = string.format('nvim-%d.%d', major, minor)
     local will_be_removed = vim.fn.has(removal_version) == 1 and 'was removed' or 'will be removed'
 
diff --git a/runtime/lua/vim/diagnostic.lua b/runtime/lua/vim/diagnostic.lua
index 81862988fc..2f6afcafb6 100644
--- a/runtime/lua/vim/diagnostic.lua
+++ b/runtime/lua/vim/diagnostic.lua
@@ -2857,7 +2857,7 @@ function M.match(str, pat, groups, severity_map, defaults)
     if field == 'severity' then
       diagnostic[field] = severity_map[match]
     elseif field == 'lnum' or field == 'end_lnum' or field == 'col' or field == 'end_col' then
-      diagnostic[field] = assert(tonumber(match)) - 1
+      diagnostic[field] = vim._ensure_integer(match) - 1
     elseif field then
       diagnostic[field] = match
     end
diff --git a/runtime/lua/vim/fs.lua b/runtime/lua/vim/fs.lua
index dc26790d14..7eadf8cb78 100644
--- a/runtime/lua/vim/fs.lua
+++ b/runtime/lua/vim/fs.lua
@@ -790,8 +790,7 @@ function M.abspath(path)
 
   -- Windows allows paths like C:foo/bar, these paths are relative to the current working directory
   -- of the drive specified in the path
-  local cwd = (iswin and prefix:match('^%w:$')) and uv.fs_realpath(prefix) or uv.cwd()
-  assert(cwd ~= nil)
+  local cwd = assert((iswin and prefix:match('^%w:$')) and uv.fs_realpath(prefix) or uv.cwd())
   -- Convert cwd path separator to `/`
   cwd = cwd:gsub(os_sep, '/')
 
diff --git a/runtime/lua/vim/func/_memoize.lua b/runtime/lua/vim/func/_memoize.lua
index c46f878067..c79ca596db 100644
--- a/runtime/lua/vim/func/_memoize.lua
+++ b/runtime/lua/vim/func/_memoize.lua
@@ -24,11 +24,15 @@ local function resolve_hash(hash)
   if type(hash) == 'number' then
     hash = idx_hash(hash)
   elseif type(hash) == 'string' then
-    local c = hash == 'concat' or hash:match('^concat%-(%d+)')
-    if c then
-      hash = concat_hash(tonumber(c))
+    if hash == 'concat' then
+      hash = concat_hash()
     else
-      error('invalid value for hash: ' .. hash)
+      local c = hash:match('^concat%-(%d+)')
+      if c then
+        hash = concat_hash(vim._ensure_integer(c))
+      else
+        error('invalid value for hash: ' .. hash)
+      end
     end
   end
   --- @cast hash -integer
diff --git a/runtime/lua/vim/health.lua b/runtime/lua/vim/health.lua
index 663d4872bd..e22e72c589 100644
--- a/runtime/lua/vim/health.lua
+++ b/runtime/lua/vim/health.lua
@@ -147,7 +147,7 @@ local function filepath_to_healthcheck(path)
       -- */health/init.lua
       name = vim.fs.dirname(vim.fs.dirname(subpath))
     end
-    name = assert(name:gsub('/', '.')) --- @type string
+    name = assert(name:gsub('/', '.')) --[[@as string]]
 
     func = 'require("' .. name .. '.health").check()'
     filetype = 'l'
diff --git a/runtime/lua/vim/health/health.lua b/runtime/lua/vim/health/health.lua
index 42e7bdb067..b48f2306a2 100644
--- a/runtime/lua/vim/health/health.lua
+++ b/runtime/lua/vim/health/health.lua
@@ -295,10 +295,15 @@ local function check_tmux()
   if tmux_esc_time ~= 'error' then
     if tmux_esc_time == '' then
       health.error('`escape-time` is not set', suggestions)
-    elseif tonumber(tmux_esc_time) > 300 then
-      health.error('`escape-time` (' .. tmux_esc_time .. ') is higher than 300ms', suggestions)
     else
-      health.ok('escape-time: ' .. tmux_esc_time)
+      local tmux_esc_time_ms = vim._tointeger(tmux_esc_time)
+      if not tmux_esc_time_ms then
+        health.error('`escape-time` (' .. tmux_esc_time .. ') is not an integer', suggestions)
+      elseif tmux_esc_time_ms > 300 then
+        health.error('`escape-time` (' .. tmux_esc_time .. ') is higher than 300ms', suggestions)
+      else
+        health.ok('escape-time: ' .. tmux_esc_time)
+      end
     end
   end
 
diff --git a/runtime/lua/vim/loader.lua b/runtime/lua/vim/loader.lua
index c5279990d1..6aa79a0244 100644
--- a/runtime/lua/vim/loader.lua
+++ b/runtime/lua/vim/loader.lua
@@ -174,13 +174,21 @@ local function read_cachefile(cname)
 
   --- @type integer[]|{[0]:integer}
   local header = vim.split(data:sub(1, zero - 1), ',')
-  if tonumber(header[1]) ~= VERSION then
+  local version = vim._tointeger(header[1])
+  if version ~= VERSION then
+    return
+  end
+
+  local size = vim._tointeger(header[2])
+  local sec = vim._tointeger(header[3])
+  local nsec = vim._tointeger(header[4])
+  if not (size and sec and nsec) then
     return
   end
 
   local hash = {
-    size = tonumber(header[2]),
-    mtime = { sec = tonumber(header[3]), nsec = tonumber(header[4]) },
+    size = size,
+    mtime = { sec = sec, nsec = nsec },
   }
 
   local chunk = data:sub(zero + 1)
diff --git a/runtime/lua/vim/lsp.lua b/runtime/lua/vim/lsp.lua
index 0764c28b44..aad7958aeb 100644
--- a/runtime/lua/vim/lsp.lua
+++ b/runtime/lua/vim/lsp.lua
@@ -1136,7 +1136,7 @@ api.nvim_create_autocmd('VimLeavePre', {
 
     local max_timeout = 0
     for _, client in pairs(active_clients) do
-      max_timeout = math.max(max_timeout, tonumber(client.exit_timeout) or 0)
+      max_timeout = math.max(max_timeout, vim._tointeger(client.exit_timeout) or 0)
       client:stop(client.exit_timeout)
     end
 
diff --git a/runtime/lua/vim/lsp/_changetracking.lua b/runtime/lua/vim/lsp/_changetracking.lua
index 3d54b12656..e3c9feb46a 100644
--- a/runtime/lua/vim/lsp/_changetracking.lua
+++ b/runtime/lua/vim/lsp/_changetracking.lua
@@ -32,8 +32,8 @@ local M = {}
 --- @field lines string[] snapshot of buffer lines from last didChange
 --- @field lines_tmp string[]
 --- @field pending_changes table[] List of debounced changes in incremental sync mode
---- @field timer uv.uv_timer_t? uv_timer
---- @field last_flush nil|number uv.hrtime of the last flush/didChange-notification
+--- @field timer? uv.uv_timer_t uv_timer
+--- @field last_flush? number uv.hrtime of the last flush/didChange-notification
 --- @field needs_flush boolean true if buffer updates haven't been sent to clients/servers yet
 --- @field refs integer how many clients are using this group
 ---
@@ -68,7 +68,7 @@ local function get_group(client)
   local change_capability = vim.tbl_get(client.server_capabilities, 'textDocumentSync', 'change')
   local sync_kind = change_capability or protocol.TextDocumentSyncKind.None
   if not allow_inc_sync and change_capability == protocol.TextDocumentSyncKind.Incremental then
-    sync_kind = protocol.TextDocumentSyncKind.Full --[[@as integer]]
+    sync_kind = protocol.TextDocumentSyncKind.Full
   end
   return {
     sync_kind = sync_kind,
diff --git a/runtime/lua/vim/lsp/_snippet_grammar.lua b/runtime/lua/vim/lsp/_snippet_grammar.lua
index f06d6e9afd..7828b2a994 100644
--- a/runtime/lua/vim/lsp/_snippet_grammar.lua
+++ b/runtime/lua/vim/lsp/_snippet_grammar.lua
@@ -174,9 +174,7 @@ local G = P({
 --- @param input string
 --- @return vim.snippet.Node<vim.snippet.SnippetData>
 function M.parse(input)
-  local snippet = G:match(input)
-  assert(snippet, 'snippet parsing failed')
-  return snippet --- @type vim.snippet.Node<vim.snippet.SnippetData>
+  return assert(G:match(input), 'snippet parsing failed')
 end
 
 return M
diff --git a/runtime/lua/vim/lsp/client.lua b/runtime/lua/vim/lsp/client.lua
index 635c2cde76..d7d5b46ba6 100644
--- a/runtime/lua/vim/lsp/client.lua
+++ b/runtime/lua/vim/lsp/client.lua
@@ -713,10 +713,8 @@ end
 --- @see |vim.lsp.buf_request_all()|
 function Client:request(method, params, handler, bufnr)
   if not handler then
-    handler = assert(
-      self:_resolve_handler(method),
-      string.format('not found: %q request handler for client %q.', method, self.name)
-    )
+    handler = self:_resolve_handler(method)
+      or error(('not found: %q request handler for client %q.'):format(method, self.name))
   end
   -- Ensure pending didChange notifications are sent so that the server doesn't operate on a stale state
   changetracking.flush(self, bufnr)
diff --git a/runtime/lua/vim/lsp/completion.lua b/runtime/lua/vim/lsp/completion.lua
index d70a61d0da..66880ae8d1 100644
--- a/runtime/lua/vim/lsp/completion.lua
+++ b/runtime/lua/vim/lsp/completion.lua
@@ -324,7 +324,13 @@ local function generate_kind(item)
 
   -- extract hex from RGB format
   local r, g, b = doc:match('rgb%((%d+)%s*,?%s*(%d+)%s*,?%s*(%d+)%)')
-  local hex = r and string.format('%02x%02x%02x', tonumber(r), tonumber(g), tonumber(b))
+  local hex = r
+      and string.format(
+        '%02x%02x%02x',
+        vim._ensure_integer(r),
+        vim._ensure_integer(g),
+        vim._ensure_integer(b)
+      )
     or doc:match('#?([%da-fA-F]+)')
 
   if not hex then
@@ -696,7 +702,7 @@ function CompletionResolver:is_valid()
   return vim.api.nvim_buf_is_valid(self.bufnr)
     and vim.api.nvim_get_current_buf() == self.bufnr
     and vim.startswith(vim.api.nvim_get_mode().mode, 'i')
-    and tonumber(vim.fn.pumvisible()) == 1
+    and vim.fn.pumvisible() ~= 0
     and (vim.tbl_get(cmp_info, 'completed', 'word') or '') == self.word,
     cmp_info
 end
@@ -916,7 +922,7 @@ local function trigger(bufnr, clients, ctx)
   reset_timer()
   Context:cancel_pending()
 
-  if tonumber(vim.fn.pumvisible()) == 1 and not Context.isIncomplete then
+  if vim.fn.pumvisible() ~= 0 and not Context.isIncomplete then
     return
   end
 
@@ -1018,7 +1024,7 @@ end
 
 --- @param handle vim.lsp.completion.BufHandle
 local function on_insert_char_pre(handle)
-  if tonumber(vim.fn.pumvisible()) == 1 then
+  if vim.fn.pumvisible() ~= 0 then
     if Context.isIncomplete then
       reset_timer()
 
@@ -1143,8 +1149,7 @@ local function enable_completions(client_id, bufnr, opts)
   end
 
   if not buf_handle.clients[client_id] then
-    local client = lsp.get_client_by_id(client_id)
-    assert(client, 'invalid client ID')
+    local client = assert(lsp.get_client_by_id(client_id), 'invalid client ID')
 
     -- Add the new client to the buffer's clients.
     buf_handle.clients[client_id] = client
@@ -1245,7 +1250,6 @@ end
 --- - findstart=1: list of matches (actually just calls |complete()|)
 function M._omnifunc(findstart, base)
   lsp.log.debug('omnifunc.findstart', { findstart = findstart, base = base })
-  assert(base) -- silence luals
   local bufnr = api.nvim_get_current_buf()
   local clients = lsp.get_clients({ bufnr = bufnr, method = 'textDocument/completion' })
   local remaining = #clients
diff --git a/runtime/lua/vim/lsp/document_color.lua b/runtime/lua/vim/lsp/document_color.lua
index 0b9e1a415c..1c6e3d40d0 100644
--- a/runtime/lua/vim/lsp/document_color.lua
+++ b/runtime/lua/vim/lsp/document_color.lua
@@ -47,10 +47,9 @@ local function get_contrast_color(color)
   if not (r_s and g_s and b_s) then
     error('Invalid color format: ' .. color)
   end
-  local r, g, b = tonumber(r_s, 16), tonumber(g_s, 16), tonumber(b_s, 16)
-  if not (r and g and b) then
-    error('Invalid color format: ' .. color)
-  end
+  local r = vim._ensure_integer(r_s, 16)
+  local g = vim._ensure_integer(g_s, 16)
+  local b = vim._ensure_integer(b_s, 16)
 
   -- Source: https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
   -- Using power 2.2 is a close approximation to full piecewise transform
diff --git a/runtime/lua/vim/lsp/health.lua b/runtime/lua/vim/lsp/health.lua
index 14502851a5..c868affa10 100644
--- a/runtime/lua/vim/lsp/health.lua
+++ b/runtime/lua/vim/lsp/health.lua
@@ -137,8 +137,7 @@ local function check_watcher()
     return
   end
 
-  local watchfunc = vim.lsp._watchfiles._watchfunc
-  assert(watchfunc)
+  local watchfunc = assert(vim.lsp._watchfiles._watchfunc)
   local watchfunc_name --- @type string
   if watchfunc == vim._watch.watch then
     watchfunc_name = 'libuv-watch'
diff --git a/runtime/lua/vim/lsp/rpc.lua b/runtime/lua/vim/lsp/rpc.lua
index a34a04bffd..d75b3ed18f 100644
--- a/runtime/lua/vim/lsp/rpc.lua
+++ b/runtime/lua/vim/lsp/rpc.lua
@@ -56,7 +56,10 @@ local function get_content_length(header)
     elseif state == 'value' then
       if c == 13 and header:byte(i + 1) == 10 then -- must end with \r\n
         local value = buf:get()
-        return assert(digit and tonumber(value), 'value of Content-Length is not number: ' .. value)
+        if digit then
+          return vim._ensure_integer(value)
+        end
+        error('value of Content-Length is not number: ' .. value)
       else
         buf:put(string.char(c))
       end
@@ -429,7 +432,7 @@ function Client:handle_body(body)
     )
   then
     -- We sent a number, so we expect a number.
-    local result_id = assert(tonumber(decoded.id), 'response id must be a number') --[[@as integer]]
+    local result_id = vim._ensure_integer(decoded.id)
 
     -- Notify the user that a response was received for the request
     local notify_reply_callback = self.notify_reply_callbacks[result_id]
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index a0ac87afec..b58286b7b7 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -636,8 +636,7 @@ function M.rename(old_fname, new_fname, opts)
   local newdir = vim.fs.dirname(new_fname)
   vim.fn.mkdir(newdir, 'p')
 
-  local ok, err = os.rename(old_fname_full, new_fname)
-  assert(ok, err)
+  assert(os.rename(old_fname_full, new_fname))
 
   local old_undofile = vim.fn.undofile(old_fname_full)
   if uv.fs_stat(old_undofile) ~= nil then
@@ -1745,10 +1744,10 @@ function M.open_floating_preview(contents, syntax, opts)
   api.nvim_create_autocmd('WinClosed', {
     group = api.nvim_create_augroup('nvim.closing_floating_preview', { clear = true }),
     callback = function(args)
-      local winid = tonumber(args.match)
-      local ok, preview_bufnr = pcall(api.nvim_win_get_var, winid, 'lsp_floating_bufnr')
+      local winid = vim._tointeger(args.match)
+      local preview_bufnr = vim.w[winid].lsp_floating_bufnr
       if
-        ok
+        preview_bufnr
         and api.nvim_buf_is_valid(preview_bufnr)
         and winid == vim.b[preview_bufnr].lsp_floating_preview
       then
diff --git a/runtime/lua/vim/pack.lua b/runtime/lua/vim/pack.lua
index 6d9b8dc9a1..a218a38d6a 100644
--- a/runtime/lua/vim/pack.lua
+++ b/runtime/lua/vim/pack.lua
@@ -1157,7 +1157,7 @@ local function show_confirm_buf(lines, on_finish)
   --- @type integer
   local cancel_au_id
   local function on_cancel(data)
-    if tonumber(data.match) ~= win_id then
+    if vim._tointeger(data.match) ~= win_id then
       return
     end
     pcall(api.nvim_del_autocmd, cancel_au_id)
diff --git a/runtime/lua/vim/pack/_lsp.lua b/runtime/lua/vim/pack/_lsp.lua
index f40d65ddea..7eedf9dfe5 100644
--- a/runtime/lua/vim/pack/_lsp.lua
+++ b/runtime/lua/vim/pack/_lsp.lua
@@ -20,7 +20,7 @@ function methods.shutdown(_, callback)
 end
 
 local get_confirm_bufnr = function(uri)
-  return tonumber(uri:match('^nvim%-pack://confirm#(%d+)$'))
+  return vim._tointeger(uri:match('^nvim%-pack://confirm#(%d+)$'))
 end
 
 local group_header_pattern = '^# (%S+)'
diff --git a/runtime/lua/vim/treesitter/_query_linter.lua b/runtime/lua/vim/treesitter/_query_linter.lua
index 7bfc860111..391d3487d1 100644
--- a/runtime/lua/vim/treesitter/_query_linter.lua
+++ b/runtime/lua/vim/treesitter/_query_linter.lua
@@ -86,7 +86,8 @@ local function get_error_entry(err, node)
   local start_line, start_col = node:range()
   local line_offset, col_offset, msg = err:gmatch('.-:%d+: Query error at (%d+):(%d+)%. ([^:]+)')() ---@type string, string, string
   start_line, start_col =
-    start_line + tonumber(line_offset) - 1, start_col + tonumber(col_offset) - 1
+    start_line + vim._ensure_integer(line_offset) - 1,
+    start_col + vim._ensure_integer(col_offset) - 1
   local end_line, end_col = start_line, start_col
   if msg:match('^Invalid syntax') or msg:match('^Impossible') then
     -- Use the length of the underlined node
diff --git a/runtime/lua/vim/treesitter/highlighter.lua b/runtime/lua/vim/treesitter/highlighter.lua
index b71f0db9a7..9521ce3dfd 100644
--- a/runtime/lua/vim/treesitter/highlighter.lua
+++ b/runtime/lua/vim/treesitter/highlighter.lua
@@ -429,7 +429,7 @@ local function on_range_impl(
 
           -- The "priority" attribute can be set at the pattern level or on a particular capture
           local priority = (
-            tonumber(metadata.priority or metadata[capture] and metadata[capture].priority)
+            vim._tointeger(metadata.priority or metadata[capture] and metadata[capture].priority)
             or vim.hl.priorities.treesitter
           ) + spell_pri_offset
 
diff --git a/runtime/lua/vim/uri.lua b/runtime/lua/vim/uri.lua
index 8b6f1a61ee..0e954bcb7a 100644
--- a/runtime/lua/vim/uri.lua
+++ b/runtime/lua/vim/uri.lua
@@ -25,7 +25,7 @@ local PATTERNS = {
 ---@param hex string
 ---@return string
 local function hex_to_char(hex)
-  return schar(tonumber(hex, 16))
+  return schar(vim._ensure_integer(hex, 16))
 end
 
 ---@param char string
@@ -101,7 +101,7 @@ end
 ---@param uri string
 ---@return string filename or unchanged URI for non-file URIs
 function M.uri_to_fname(uri)
-  local scheme = assert(uri:match(URI_SCHEME_PATTERN), 'URI must contain a scheme: ' .. uri)
+  local scheme = uri:match(URI_SCHEME_PATTERN) or error('URI must contain a scheme: ' .. uri)
   if scheme ~= 'file' then
     return uri
   end
diff --git a/runtime/lua/vim/version.lua b/runtime/lua/vim/version.lua
index a904255490..652d645325 100644
--- a/runtime/lua/vim/version.lua
+++ b/runtime/lua/vim/version.lua
@@ -86,8 +86,12 @@ local function cmp_prerel(prerel1, prerel2)
     if word1 == nil and word2 == nil then -- Done iterating.
       return 0
     end
-    word1, n1, word2, n2 =
-      word1 or '', n1 and tonumber(n1) or 0, word2 or '', n2 and tonumber(n2) or 0
+
+    word1 = word1 or ''
+    n1 = vim._tointeger(n1) or 0
+    word2 = word2 or ''
+    n2 = vim._tointeger(n2) or 0
+
     if word1 ~= word2 then
       return word1 < word2 and -1 or 1
     end
@@ -197,9 +201,9 @@ function M._version(version, strict) -- Adapted from https://github.com/folke/la
     or (major and minor and patch and major ~= '' and minor ~= '' and patch ~= '')
   then
     return setmetatable({
-      major = tonumber(major),
-      minor = minor == '' and 0 or tonumber(minor),
-      patch = patch == '' and 0 or tonumber(patch),
+      major = vim._ensure_integer(major),
+      minor = minor == '' and 0 or vim._ensure_integer(minor),
+      patch = patch == '' and 0 or vim._ensure_integer(patch),
       prerelease = prerel ~= '' and prerel or nil,
       build = build ~= '' and build or nil,
     }, Version)
@@ -286,7 +290,6 @@ function M.range(spec) -- Adapted from https://github.com/folke/lazy.nvim
     return setmetatable({ from = M.parse('0.0.0') }, range_mt)
   end
 
-  ---@type number?
   local hyphen = spec:find(' - ', 1, true)
   if hyphen then
     local a = spec:sub(1, hyphen - 1)
@@ -379,15 +382,15 @@ function M.intersect(r1, r2)
   end
 end
 
----@param v string|vim.Version
+---@param v string|vim.Version|number[]
 ---@return string
-local function create_err_msg(v)
+local function err_msg(v)
   if type(v) == 'string' then
-    return string.format('invalid version: "%s"', tostring(v))
+    return ('invalid version: "%s"'):format(v)
   elseif type(v) == 'table' and v.major then
-    return string.format('invalid version: %s', vim.inspect(v))
+    return ('invalid version: %s'):format(vim.inspect(v))
   end
-  return string.format('invalid version: %s (%s)', tostring(v), type(v))
+  return ('invalid version: %s (%s)'):format(tostring(v), type(v))
 end
 
 --- Parses and compares two version objects (the result of |vim.version.parse()|, or
@@ -413,8 +416,8 @@ end
 ---@param v2 vim.Version|number[]|string Version to compare with `v1`.
 ---@return integer -1 if `v1 < v2`, 0 if `v1 == v2`, 1 if `v1 > v2`.
 function M.cmp(v1, v2)
-  local v1_parsed = assert(M._version(v1), create_err_msg(v1))
-  local v2_parsed = assert(M._version(v2), create_err_msg(v1))
+  local v1_parsed = M._version(v1) or error(err_msg(v1))
+  local v2_parsed = M._version(v2) or error(err_msg(v2))
   if v1_parsed == v2_parsed then
     return 0
   end
@@ -492,7 +495,9 @@ end
 ---@param opts vim.version.parse.Opts? Options for parsing.
 ---@return vim.Version? # `Version` object or `nil` if input is invalid.
 function M.parse(version, opts)
-  assert(type(version) == 'string', create_err_msg(version))
+  if type(version) ~= 'string' then
+    error(err_msg(version))
+  end
   opts = opts or { strict = false }
   return M._version(version, opts.strict)
 end