diff --git a/runtime/doc/lsp.txt b/runtime/doc/lsp.txt
index d199634bae..06fec15f3c 100644
--- a/runtime/doc/lsp.txt
+++ b/runtime/doc/lsp.txt
@@ -1611,8 +1611,8 @@ enable({enable}, {filter})                       *vim.lsp.inlay_hint.enable()*
     Parameters: ~
       • {enable}  (`boolean?`) true/nil to enable, false to disable
       • {filter}  (`table?`) Optional filters |kwargs|, or `nil` for all.
-                  • {bufnr} (`integer?`) Buffer number, or 0/nil for current
-                    buffer.
+                  • {bufnr} (`integer?`) Buffer number, or 0 for current
+                    buffer, or nil for all.
 
 get({filter})                                       *vim.lsp.inlay_hint.get()*
     Get the list of inlay hints, (optionally) restricted by buffer or range.
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index bae0030a14..4d06f3df8d 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -148,6 +148,8 @@ BREAKING CHANGES IN HEAD                                    *news-breaking-dev*
 The following changes to UNRELEASED features were made during the development
 cycle (Nvim HEAD, the "master" branch).
 
+• `vim.lsp.inlay_hint.enable()` now take effect on all buffers by default.
+
 • Removed `vim.treesitter.foldtext` as transparent foldtext is now supported
   https://github.com/neovim/neovim/pull/20750
 
diff --git a/runtime/lua/vim/lsp/inlay_hint.lua b/runtime/lua/vim/lsp/inlay_hint.lua
index 3d8b54ee3d..985cbef5ff 100644
--- a/runtime/lua/vim/lsp/inlay_hint.lua
+++ b/runtime/lua/vim/lsp/inlay_hint.lua
@@ -4,13 +4,26 @@ local ms = require('vim.lsp.protocol').Methods
 local api = vim.api
 local M = {}
 
----@class (private) vim.lsp.inlay_hint.bufstate
+---@class (private) vim.lsp.inlay_hint.globalstate Global state for inlay hints
+---@field enabled boolean Whether inlay hints are enabled for this scope
+---@type vim.lsp.inlay_hint.globalstate
+local globalstate = {
+  enabled = false,
+}
+
+---@class (private) vim.lsp.inlay_hint.bufstate: vim.lsp.inlay_hint.globalstate Buffer local state for inlay hints
 ---@field version? integer
 ---@field client_hints? table<integer, table<integer, lsp.InlayHint[]>> client_id -> (lnum -> hints)
 ---@field applied table<integer, integer> Last version of hints applied to this line
----@field enabled boolean Whether inlay hints are enabled for this buffer
 ---@type table<integer, vim.lsp.inlay_hint.bufstate>
-local bufstates = {}
+local bufstates = vim.defaulttable(function(_)
+  return setmetatable({ applied = {} }, {
+    __index = globalstate,
+    __newindex = function(state, key, value)
+      rawset(state, key, (globalstate[key] ~= value) and value or nil)
+    end,
+  })
+end)
 
 local namespace = api.nvim_create_namespace('vim_lsp_inlayhint')
 local augroup = api.nvim_create_augroup('vim_lsp_inlayhint', {})
@@ -34,7 +47,7 @@ function M.on_inlayhint(err, result, ctx, _)
     return
   end
   local bufstate = bufstates[bufnr]
-  if not bufstate or not bufstate.enabled then
+  if not bufstate.enabled then
     return
   end
   if not (bufstate.client_hints and bufstate.version) then
@@ -91,11 +104,7 @@ function M.on_refresh(err, _, ctx, _)
   for _, bufnr in ipairs(vim.lsp.get_buffers_by_client_id(ctx.client_id)) do
     for _, winid in ipairs(api.nvim_list_wins()) do
       if api.nvim_win_get_buf(winid) == bufnr then
-        local bufstate = bufstates[bufnr]
-        if bufstate then
-          util._refresh(ms.textDocument_inlayHint, { bufnr = bufnr })
-          break
-        end
+        util._refresh(ms.textDocument_inlayHint, { bufnr = bufnr })
       end
     end
   end
@@ -154,7 +163,7 @@ function M.get(filter)
   end
 
   local bufstate = bufstates[bufnr]
-  if not (bufstate and bufstate.client_hints) then
+  if not bufstate.client_hints then
     return {}
   end
 
@@ -203,12 +212,9 @@ end
 --- Clear inlay hints
 ---@param bufnr (integer) Buffer handle, or 0 for current
 local function clear(bufnr)
-  if bufnr == nil or bufnr == 0 then
+  if bufnr == 0 then
     bufnr = api.nvim_get_current_buf()
   end
-  if not bufstates[bufnr] then
-    return
-  end
   local bufstate = bufstates[bufnr]
   local client_lens = (bufstate or {}).client_hints or {}
   local client_ids = vim.tbl_keys(client_lens) --- @type integer[]
@@ -222,15 +228,14 @@ local function clear(bufnr)
 end
 
 --- Disable inlay hints for a buffer
----@param bufnr (integer|nil) Buffer handle, or 0 or nil for current
+---@param bufnr (integer) Buffer handle, or 0 for current
 local function _disable(bufnr)
-  if bufnr == nil or bufnr == 0 then
+  if bufnr == 0 then
     bufnr = api.nvim_get_current_buf()
   end
   clear(bufnr)
-  if bufstates[bufnr] then
-    bufstates[bufnr] = { enabled = false, applied = {} }
-  end
+  bufstates[bufnr] = nil
+  bufstates[bufnr].enabled = false
 end
 
 --- Refresh inlay hints, only if we have attached clients that support it
@@ -244,30 +249,38 @@ local function _refresh(bufnr, opts)
 end
 
 --- Enable inlay hints for a buffer
----@param bufnr (integer|nil) Buffer handle, or 0 or nil for current
+---@param bufnr (integer) Buffer handle, or 0 for current
 local function _enable(bufnr)
-  if bufnr == nil or bufnr == 0 then
+  if bufnr == 0 then
     bufnr = api.nvim_get_current_buf()
   end
-  local bufstate = bufstates[bufnr]
-  if not bufstate then
-    bufstates[bufnr] = { applied = {}, enabled = true }
-    api.nvim_create_autocmd('LspNotify', {
-      buffer = bufnr,
-      callback = function(opts)
-        if
-          opts.data.method ~= ms.textDocument_didChange
-          and opts.data.method ~= ms.textDocument_didOpen
-        then
-          return
-        end
-        if bufstates[bufnr] and bufstates[bufnr].enabled then
-          _refresh(bufnr, { client_id = opts.data.client_id })
-        end
-      end,
-      group = augroup,
-    })
-    _refresh(bufnr)
+  bufstates[bufnr] = nil
+  bufstates[bufnr].enabled = true
+  _refresh(bufnr)
+end
+
+api.nvim_create_autocmd('LspNotify', {
+  callback = function(args)
+    ---@type integer
+    local bufnr = args.buf
+
+    if
+      args.data.method ~= ms.textDocument_didChange
+      and args.data.method ~= ms.textDocument_didOpen
+    then
+      return
+    end
+    if bufstates[bufnr].enabled then
+      _refresh(bufnr, { client_id = args.data.client_id })
+    end
+  end,
+  group = augroup,
+})
+api.nvim_create_autocmd('LspAttach', {
+  callback = function(args)
+    ---@type integer
+    local bufnr = args.buf
+
     api.nvim_buf_attach(bufnr, false, {
       on_reload = function(_, cb_bufnr)
         clear(cb_bufnr)
@@ -278,32 +291,30 @@ local function _enable(bufnr)
       end,
       on_detach = function(_, cb_bufnr)
         _disable(cb_bufnr)
+        bufstates[cb_bufnr] = nil
       end,
     })
-    api.nvim_create_autocmd('LspDetach', {
-      buffer = bufnr,
-      callback = function(args)
-        local clients = vim.lsp.get_clients({ bufnr = bufnr, method = ms.textDocument_inlayHint })
-
-        if
-          not vim.iter(clients):any(function(c)
-            return c.id ~= args.data.client_id
-          end)
-        then
-          _disable(bufnr)
-        end
-      end,
-      group = augroup,
-    })
-  else
-    bufstate.enabled = true
-    _refresh(bufnr)
-  end
-end
+  end,
+  group = augroup,
+})
+api.nvim_create_autocmd('LspDetach', {
+  callback = function(args)
+    ---@type integer
+    local bufnr = args.buf
+    local clients = vim.lsp.get_clients({ bufnr = bufnr, method = ms.textDocument_inlayHint })
 
+    if not vim.iter(clients):any(function(c)
+      return c.id ~= args.data.client_id
+    end) then
+      _disable(bufnr)
+    end
+  end,
+  group = augroup,
+})
 api.nvim_set_decoration_provider(namespace, {
   on_win = function(_, _, bufnr, topline, botline)
-    local bufstate = bufstates[bufnr]
+    ---@type vim.lsp.inlay_hint.bufstate
+    local bufstate = rawget(bufstates, bufnr)
     if not bufstate then
       return
     end
@@ -361,13 +372,13 @@ function M.is_enabled(bufnr)
   if bufnr == nil or bufnr == 0 then
     bufnr = api.nvim_get_current_buf()
   end
-  return bufstates[bufnr] and bufstates[bufnr].enabled or false
+  return bufstates[bufnr].enabled
 end
 
 --- Optional filters |kwargs|, or `nil` for all.
 --- @class vim.lsp.inlay_hint.enable.Filter
 --- @inlinedoc
---- Buffer number, or 0/nil for current buffer.
+--- Buffer number, or 0 for current buffer, or nil for all.
 --- @field bufnr integer?
 
 --- Enables or disables inlay hints for a buffer.
@@ -392,11 +403,28 @@ function M.enable(enable, filter)
   end
 
   vim.validate({ enable = { enable, 'boolean', true }, filter = { filter, 'table', true } })
+  enable = enable == nil or enable
   filter = filter or {}
-  if enable == false then
-    _disable(filter.bufnr)
+
+  if filter.bufnr == nil then
+    globalstate.enabled = enable
+    for bufnr, _ in pairs(bufstates) do
+      if api.nvim_buf_is_loaded(bufnr) then
+        if enable == false then
+          _disable(bufnr)
+        else
+          _enable(bufnr)
+        end
+      else
+        bufstates[bufnr] = nil
+      end
+    end
   else
-    _enable(filter.bufnr)
+    if enable == false then
+      _disable(filter.bufnr)
+    else
+      _enable(filter.bufnr)
+    end
   end
 end
 
diff --git a/test/functional/plugin/lsp/inlay_hint_spec.lua b/test/functional/plugin/lsp/inlay_hint_spec.lua
index 0aaf94d6da..94e7fbb97c 100644
--- a/test/functional/plugin/lsp/inlay_hint_spec.lua
+++ b/test/functional/plugin/lsp/inlay_hint_spec.lua
@@ -137,20 +137,51 @@ describe('vim.lsp.inlay_hint', function()
       )
     end)
 
-    it('clears/applies inlay hints when passed false/true/nil', function()
-      exec_lua([[vim.lsp.inlay_hint.enable(false, { bufnr = bufnr })]])
-      screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
+    describe('clears/applies inlay hints when passed false/true/nil', function()
+      before_each(function()
+        exec_lua([[
+          bufnr2 = vim.api.nvim_create_buf(true, false)
+          vim.lsp.buf_attach_client(bufnr2, client_id)
+          vim.api.nvim_win_set_buf(0, bufnr2)
+        ]])
+        insert(text)
+        exec_lua([[vim.lsp.inlay_hint.enable(true, { bufnr = bufnr2 })]])
+        exec_lua([[vim.api.nvim_win_set_buf(0, bufnr)]])
+        screen:expect({ grid = grid_with_inlay_hints })
+      end)
 
-      exec_lua([[vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })]])
-      screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+      it('for one single buffer', function()
+        exec_lua([[
+          vim.lsp.inlay_hint.enable(false, { bufnr = bufnr })
+          vim.api.nvim_win_set_buf(0, bufnr2)
+        ]])
+        screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+        exec_lua([[vim.api.nvim_win_set_buf(0, bufnr)]])
+        screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
 
-      exec_lua(
-        [[vim.lsp.inlay_hint.enable(not vim.lsp.inlay_hint.is_enabled(bufnr), { bufnr = bufnr })]]
-      )
-      screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
+        exec_lua([[vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })]])
+        screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
 
-      exec_lua([[vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })]])
-      screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+        exec_lua(
+          [[vim.lsp.inlay_hint.enable(not vim.lsp.inlay_hint.is_enabled(bufnr), { bufnr = bufnr })]]
+        )
+        screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
+
+        exec_lua([[vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })]])
+        screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+      end)
+
+      it('for all buffers', function()
+        exec_lua([[vim.lsp.inlay_hint.enable(false)]])
+        screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
+        exec_lua([[vim.api.nvim_win_set_buf(0, bufnr2)]])
+        screen:expect({ grid = grid_without_inlay_hints, unchanged = true })
+
+        exec_lua([[vim.lsp.inlay_hint.enable(true)]])
+        screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+        exec_lua([[vim.api.nvim_win_set_buf(0, bufnr)]])
+        screen:expect({ grid = grid_with_inlay_hints, unchanged = true })
+      end)
     end)
   end)