diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index d6a1666426..b7d098b956 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -86,6 +86,7 @@ LSP
   arguments corresponding to a log entry instead of the individual arguments.
 • `vim.lsp.semantic_tokens.start/stop` now renamed to
   `vim.lsp.semantic_tokens.enable`
+• Missing fields in LSP messages are now represented using |vim.NIL| instead of nil.
 
 LUA
 
diff --git a/runtime/lua/vim/lsp/_meta/protocol.lua b/runtime/lua/vim/lsp/_meta/protocol.lua
index cc274d2893..9b8013b536 100644
--- a/runtime/lua/vim/lsp/_meta/protocol.lua
+++ b/runtime/lua/vim/lsp/_meta/protocol.lua
@@ -11,7 +11,7 @@ nvim -l src/gen/gen_lsp.lua --version 3.18
 ---@meta
 error('Cannot require a meta file')
 
----@alias lsp.null nil
+---@alias lsp.null vim.NIL
 ---@alias uinteger integer
 ---@alias decimal number
 ---@alias lsp.DocumentUri string
@@ -3297,7 +3297,7 @@ error('Cannot require a meta file')
 ---@class lsp.FileOperationPattern
 ---
 ---The glob pattern to match. Glob patterns can have the following syntax:
----- `*` to match one or more characters in a path segment
+---- `*` to match zero or more characters in a path segment
 ---- `?` to match on one character in a path segment
 ---- `**` to match any number of path segments, including none
 ---- `{}` to group sub patterns into an OR expression. (e.g. `**/*.{ts,js}` matches all TypeScript and JavaScript files)
@@ -5699,7 +5699,7 @@ error('Cannot require a meta file')
 ---its resource, or a glob-pattern that is applied to the {@link TextDocument.fileName path}.
 ---
 ---Glob patterns can have the following syntax:
----- `*` to match one or more characters in a path segment
+---- `*` to match zero or more characters in a path segment
 ---- `?` to match on one character in a path segment
 ---- `**` to match any number of path segments, including none
 ---- `{}` to group sub patterns into an OR expression. (e.g. `**/*.{ts,js}` matches all TypeScript and JavaScript files)
@@ -5720,7 +5720,7 @@ error('Cannot require a meta file')
 ---@alias lsp.NotebookDocumentFilter lsp.NotebookDocumentFilterNotebookType|lsp.NotebookDocumentFilterScheme|lsp.NotebookDocumentFilterPattern
 
 ---The glob pattern to watch relative to the base path. Glob patterns can have the following syntax:
----- `*` to match one or more characters in a path segment
+---- `*` to match zero or more characters in a path segment
 ---- `?` to match on one character in a path segment
 ---- `**` to match any number of path segments, including none
 ---- `{}` to group conditions (e.g. `**/*.{ts,js}` matches all TypeScript and JavaScript files)
diff --git a/runtime/lua/vim/lsp/client.lua b/runtime/lua/vim/lsp/client.lua
index 55c49298cc..e3b8bb7ae9 100644
--- a/runtime/lua/vim/lsp/client.lua
+++ b/runtime/lua/vim/lsp/client.lua
@@ -623,7 +623,7 @@ function Client:_process_static_registrations()
         id = self.server_capabilities[capability].id,
         method = method,
         registerOptions = {
-          documentSelector = self.server_capabilities[capability].documentSelector, ---@type lsp.DocumentSelector?
+          documentSelector = self.server_capabilities[capability].documentSelector, ---@type lsp.DocumentSelector|lsp.null
         },
       }
     end
@@ -963,15 +963,19 @@ end
 function Client:_get_registration(method, bufnr)
   bufnr = vim._resolve_bufnr(bufnr)
   for _, reg in ipairs(self.registrations[method] or {}) do
-    local regoptions = reg.registerOptions --[[@as {documentSelector:lsp.TextDocumentFilter[]}]]
-    if not regoptions or not regoptions.documentSelector then
+    local regoptions = reg.registerOptions --[[@as {documentSelector:lsp.DocumentSelector|lsp.null}]]
+    if
+      not regoptions
+      or regoptions == vim.NIL
+      or not regoptions.documentSelector
+      or regoptions.documentSelector == vim.NIL
+    then
       return reg
     end
-    local documentSelector = regoptions.documentSelector
     local language = self:_get_language_id(bufnr)
     local uri = vim.uri_from_bufnr(bufnr)
     local fname = vim.uri_to_fname(uri)
-    for _, filter in ipairs(documentSelector) do
+    for _, filter in ipairs(regoptions.documentSelector) do
       local flang, fscheme, fpat = filter.language, filter.scheme, filter.pattern
       if
         not (flang and language ~= flang)
@@ -1162,7 +1166,7 @@ end
 --- @param method (vim.lsp.protocol.Method.ServerToClient) LSP method name
 --- @param params (table) The parameters for that method
 --- @return any result
---- @return lsp.ResponseError error code and message set in case an exception happens during the request.
+--- @return lsp.ResponseError? error code and message set in case an exception happens during the request.
 function Client:_server_request(method, params)
   log.trace('server_request', method, params)
   local handler = self:_resolve_handler(method)
diff --git a/runtime/lua/vim/lsp/rpc.lua b/runtime/lua/vim/lsp/rpc.lua
index 0e082d0f80..d14ec0b31a 100644
--- a/runtime/lua/vim/lsp/rpc.lua
+++ b/runtime/lua/vim/lsp/rpc.lua
@@ -323,7 +323,7 @@ end
 --- @package
 --- @param body string
 function Client:handle_body(body)
-  local ok, decoded = pcall(vim.json.decode, body, { luanil = { object = true } })
+  local ok, decoded = pcall(vim.json.decode, body)
   if not ok then
     self:on_error(M.client_errors.INVALID_SERVER_JSON, decoded)
     return
@@ -355,7 +355,6 @@ function Client:handle_body(body)
           )
         end
         if err then
-          ---@cast err lsp.ResponseError
           assert(
             type(err) == 'table',
             'err must be a table. Use rpc_response_error to help format errors.'
@@ -374,8 +373,16 @@ function Client:handle_body(body)
       end
       self:send_response(decoded.id, err, result)
     end))
-    -- This works because we are expecting vim.NIL here
-  elseif decoded.id and (decoded.result ~= vim.NIL or decoded.error ~= vim.NIL) then
+  -- Proceed only if exactly one of 'result' or 'error' is present, as required by the LSP spec:
+  -- - If 'error' is nil, then 'result' must be present.
+  -- - If 'result' is nil, then 'error' must be present (and not vim.NIL).
+  elseif
+    decoded.id
+    and (
+      (decoded.error == nil and decoded.result ~= nil)
+      or (decoded.result == nil and decoded.error ~= nil and decoded.error ~= vim.NIL)
+    )
+  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]]
 
@@ -415,7 +422,7 @@ function Client:handle_body(body)
         M.client_errors.SERVER_RESULT_CALLBACK_ERROR,
         callback,
         decoded.error,
-        decoded.result
+        decoded.result ~= vim.NIL and decoded.result or nil
       )
     else
       self:on_error(M.client_errors.NO_RESULT_CALLBACK_FOUND, decoded)
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index 8188af99d9..283ee0870e 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -520,7 +520,7 @@ function M.apply_text_document_edit(
     -- do not check the version after the first edit.
     not (index and index > 1)
     and (
-      text_document.version
+      text_document.version ~= vim.NIL
       and text_document.version > 0
       and M.buf_versions[bufnr] > text_document.version
     )
@@ -827,8 +827,12 @@ function M.convert_signature_help_to_markdown_lines(signature_help, ft, triggers
   if signature.parameters and #signature.parameters > 0 then
     -- First check if the signature has an activeParameter. If it doesn't check if the response
     -- had that property instead. Else just default to 0.
-    local active_parameter =
-      math.max(signature.activeParameter or signature_help.activeParameter or 0, 0)
+    --
+    -- NOTE: Using tonumber() as a temporary workaround to handle `vim.NIL` until #34838 is merged
+    local active_parameter = math.max(
+      tonumber(signature.activeParameter) or tonumber(signature_help.activeParameter) or 0,
+      0
+    )
 
     -- If the activeParameter is > #parameters, then set it to the last
     -- NOTE: this is not fully according to the spec, but a client-side interpretation
diff --git a/src/gen/gen_lsp.lua b/src/gen/gen_lsp.lua
index d9c23873ce..dd394a380b 100755
--- a/src/gen/gen_lsp.lua
+++ b/src/gen/gen_lsp.lua
@@ -370,7 +370,7 @@ local function write_to_meta_protocol(protocol, version, output_file)
     '---@meta',
     "error('Cannot require a meta file')",
     '',
-    '---@alias lsp.null nil',
+    '---@alias lsp.null vim.NIL',
     '---@alias uinteger integer',
     '---@alias decimal number',
     '---@alias lsp.DocumentUri string',
diff --git a/test/functional/fixtures/fake-lsp-server.lua b/test/functional/fixtures/fake-lsp-server.lua
index 6798d53d2b..1077e0de1a 100644
--- a/test/functional/fixtures/fake-lsp-server.lua
+++ b/test/functional/fixtures/fake-lsp-server.lua
@@ -172,7 +172,7 @@ function tests.prepare_rename_nil()
     body = function()
       notify('start')
       expect_request('textDocument/prepareRename', function()
-        return nil, nil
+        return {}, nil
       end)
       notify('shutdown')
     end,
@@ -197,7 +197,7 @@ function tests.prepare_rename_placeholder()
       end)
       expect_request('textDocument/rename', function(params)
         assert_eq(params.newName, 'renameto')
-        return nil, nil
+        return {}, nil
       end)
       notify('shutdown')
     end,
@@ -226,7 +226,7 @@ function tests.prepare_rename_range()
       end)
       expect_request('textDocument/rename', function(params)
         assert_eq(params.newName, 'renameto')
-        return nil, nil
+        return {}, nil
       end)
       notify('shutdown')
     end,
diff --git a/test/functional/plugin/lsp/document_color_spec.lua b/test/functional/plugin/lsp/document_color_spec.lua
index 9c6d6a681e..b35cf76761 100644
--- a/test/functional/plugin/lsp/document_color_spec.lua
+++ b/test/functional/plugin/lsp/document_color_spec.lua
@@ -129,7 +129,7 @@ body {
     exec_lua(function()
       _G.server2 = _G._create_server({
         colorProvider = {
-          documentSelector = nil,
+          documentSelector = vim.NIL,
         },
         handlers = {
           ['textDocument/documentColor'] = function(_, _, callback)
diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 68db45006c..71078f12b3 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -1976,7 +1976,7 @@ describe('LSP', function()
         {
           NIL,
           {
-            arguments = { 'EXTRACT_METHOD', { metadata = {} }, 3, 0, 6123, NIL },
+            arguments = { 'EXTRACT_METHOD', { metadata = { field = vim.NIL } }, 3, 0, 6123, NIL },
             command = 'refactor.perform',
             title = 'EXTRACT_METHOD',
           },
@@ -4498,7 +4498,7 @@ describe('LSP', function()
         name = 'prepare_rename_placeholder',
         expected_handlers = {
           { NIL, {}, { method = 'shutdown', client_id = 1 } },
-          { NIL, NIL, { method = 'textDocument/rename', client_id = 1, bufnr = 1 } },
+          { {}, NIL, { method = 'textDocument/rename', client_id = 1, bufnr = 1 } },
           { NIL, {}, { method = 'start', client_id = 1 } },
         },
         expected_text = 'placeholder', -- see fake lsp response
@@ -4508,7 +4508,7 @@ describe('LSP', function()
         name = 'prepare_rename_range',
         expected_handlers = {
           { NIL, {}, { method = 'shutdown', client_id = 1 } },
-          { NIL, NIL, { method = 'textDocument/rename', client_id = 1, bufnr = 1 } },
+          { {}, NIL, { method = 'textDocument/rename', client_id = 1, bufnr = 1 } },
           { NIL, {}, { method = 'start', client_id = 1 } },
         },
         expected_text = 'line', -- see test case and fake lsp response