diff --git a/runtime/doc/lsp.txt b/runtime/doc/lsp.txt
index 7bb3603f6a..ff3bd8440b 100644
--- a/runtime/doc/lsp.txt
+++ b/runtime/doc/lsp.txt
@@ -2074,14 +2074,15 @@ from({diagnostics})                                *vim.lsp.diagnostic.from()*
         (`lsp.Diagnostic[]`)
 
                                           *vim.lsp.diagnostic.get_namespace()*
-get_namespace({client_id}, {is_pull})
+get_namespace({client_id}, {pull_id})
     Get the diagnostic namespace associated with an LSP client
     |vim.diagnostic| for diagnostics
 
     Parameters: ~
       • {client_id}  (`integer`) The id of the LSP client
-      • {is_pull}    (`boolean?`) Whether the namespace is for a pull or push
-                     client. Defaults to push
+      • {pull_id}    (`(boolean|string)?`) (default: nil) Pull diagnostics
+                     provider id (indicates "pull" client), or `nil` for a
+                     "push" client.
 
                                           *vim.lsp.diagnostic.on_diagnostic()*
 on_diagnostic({error}, {result}, {ctx})
diff --git a/runtime/lua/vim/lsp/diagnostic.lua b/runtime/lua/vim/lsp/diagnostic.lua
index b4159a0ac7..904ef611c0 100644
--- a/runtime/lua/vim/lsp/diagnostic.lua
+++ b/runtime/lua/vim/lsp/diagnostic.lua
@@ -187,14 +187,25 @@ local client_pull_namespaces = {}
 --- Get the diagnostic namespace associated with an LSP client |vim.diagnostic| for diagnostics
 ---
 ---@param client_id integer The id of the LSP client
----@param is_pull boolean? Whether the namespace is for a pull or push client. Defaults to push
-function M.get_namespace(client_id, is_pull)
+---@param pull_id (boolean|string)? (default: nil) Pull diagnostics provider id
+---               (indicates "pull" client), or `nil` for a "push" client.
+function M.get_namespace(client_id, pull_id)
   vim.validate('client_id', client_id, 'number')
+  vim.validate('pull_id', pull_id, { 'boolean', 'string' }, true)
+
+  if type(pull_id) == 'boolean' then
+    vim.deprecate('get_namespace(pull_id:boolean)', 'get_namespace(pull_id:string)', '0.14')
+  end
 
   local client = lsp.get_client_by_id(client_id)
-  if is_pull then
-    local key = ('%d'):format(client_id)
-    local name = ('nvim.lsp.%s.%d'):format(client and client.name or 'unknown', client_id)
+  if pull_id then
+    local provider_id = type(pull_id) == 'string' and pull_id or 'nil'
+    local key = ('%d:%s'):format(client_id, provider_id)
+    local name = ('nvim.lsp.%s.%d.%s'):format(
+      client and client.name or 'unknown',
+      client_id,
+      provider_id
+    )
     local ns = client_pull_namespaces[key]
     if not ns then
       ns = api.nvim_create_namespace(name)
@@ -215,8 +226,8 @@ end
 --- @param uri string
 --- @param client_id? integer
 --- @param diagnostics lsp.Diagnostic[]
---- @param is_pull boolean
-local function handle_diagnostics(uri, client_id, diagnostics, is_pull)
+--- @param pull_id boolean|string
+local function handle_diagnostics(uri, client_id, diagnostics, pull_id)
   local fname = vim.uri_to_fname(uri)
 
   if #diagnostics == 0 and vim.fn.bufexists(fname) == 0 then
@@ -230,7 +241,7 @@ local function handle_diagnostics(uri, client_id, diagnostics, is_pull)
 
   client_id = client_id or DEFAULT_CLIENT_ID
 
-  local namespace = M.get_namespace(client_id, is_pull)
+  local namespace = M.get_namespace(client_id, pull_id)
 
   vim.diagnostic.set(namespace, bufnr, diagnostic_lsp_to_vim(diagnostics, bufnr, client_id))
 end
@@ -276,11 +287,13 @@ function M.on_diagnostic(error, result, ctx)
     return
   end
 
-  handle_diagnostics(ctx.params.textDocument.uri, client_id, result.items, true)
+  ---@type lsp.DocumentDiagnosticParams
+  local params = ctx.params
+  handle_diagnostics(params.textDocument.uri, client_id, result.items, params.identifier or true)
 
   for uri, related_result in pairs(result.relatedDocuments or {}) do
     if related_result.kind == 'full' then
-      handle_diagnostics(uri, client_id, related_result.items, true)
+      handle_diagnostics(uri, client_id, related_result.items, params.identifier or true)
     end
 
     local related_bufnr = vim.uri_to_bufnr(uri)
@@ -504,6 +517,8 @@ function M._workspace_diagnostics(opts)
     end
 
     if error == nil and result ~= nil then
+      ---@type lsp.WorkspaceDiagnosticParams
+      local params = ctx.params
       for _, report in ipairs(result.items) do
         local bufnr = vim.uri_to_bufnr(report.uri)
 
@@ -515,7 +530,7 @@ function M._workspace_diagnostics(opts)
         -- We favor document pull requests over workspace results, so only update the buffer
         -- state if we're not pulling document diagnostics for this buffer.
         if bufstates[bufnr].pull_kind == 'workspace' and report.kind == 'full' then
-          handle_diagnostics(report.uri, ctx.client_id, report.items, true)
+          handle_diagnostics(report.uri, ctx.client_id, report.items, params.identifier or true)
           bufstates[bufnr].client_result_id[ctx.client_id] = report.resultId
         end
       end
diff --git a/test/functional/plugin/lsp/diagnostic_spec.lua b/test/functional/plugin/lsp/diagnostic_spec.lua
index 6952f9fdb1..12726bc2c6 100644
--- a/test/functional/plugin/lsp/diagnostic_spec.lua
+++ b/test/functional/plugin/lsp/diagnostic_spec.lua
@@ -351,6 +351,89 @@ describe('vim.lsp.diagnostic', function()
       eq('Pull Diagnostic', diags[1].message)
     end)
 
+    it('preserves push diagnostics when pull diagnostics are empty', function()
+      local push_ns_count, pull_ns_count, all_diags_count, push_ns, pull_ns = exec_lua(function()
+        vim.lsp.diagnostic.on_publish_diagnostics(nil, {
+          uri = fake_uri,
+          diagnostics = {
+            _G.make_error('Push Diagnostic', 0, 0, 0, 0),
+          },
+        }, { client_id = client_id })
+
+        vim.lsp.diagnostic.on_diagnostic(nil, {
+          kind = 'full',
+          items = {},
+        }, {
+          params = {
+            textDocument = { uri = fake_uri },
+          },
+          uri = fake_uri,
+          client_id = client_id,
+          bufnr = diagnostic_bufnr,
+        }, {})
+
+        local push_ns = vim.lsp.diagnostic.get_namespace(client_id, false)
+        local pull_ns = vim.lsp.diagnostic.get_namespace(client_id, true)
+
+        return #vim.diagnostic.get(diagnostic_bufnr, { namespace = push_ns }),
+          #vim.diagnostic.get(diagnostic_bufnr, { namespace = pull_ns }),
+          #vim.diagnostic.get(diagnostic_bufnr),
+          push_ns,
+          pull_ns
+      end)
+
+      eq(1, push_ns_count)
+      eq(0, pull_ns_count)
+      eq(1, all_diags_count)
+      neq(push_ns, pull_ns)
+    end)
+
+    it('uses pull_id to isolate pull diagnostic namespaces', function()
+      local first_count, second_count, total_count, first_ns, second_ns = exec_lua(function()
+        vim.lsp.diagnostic.on_diagnostic(nil, {
+          kind = 'full',
+          items = {
+            _G.make_error('Pull Diagnostic A', 0, 0, 0, 0),
+          },
+        }, {
+          params = {
+            identifier = 'provider-a',
+            textDocument = { uri = fake_uri },
+          },
+          uri = fake_uri,
+          client_id = client_id,
+          bufnr = diagnostic_bufnr,
+        }, {})
+
+        vim.lsp.diagnostic.on_diagnostic(nil, {
+          kind = 'full',
+          items = {},
+        }, {
+          params = {
+            identifier = 'provider-b',
+            textDocument = { uri = fake_uri },
+          },
+          uri = fake_uri,
+          client_id = client_id,
+          bufnr = diagnostic_bufnr,
+        }, {})
+
+        local first_ns = vim.lsp.diagnostic.get_namespace(client_id, 'provider-a')
+        local second_ns = vim.lsp.diagnostic.get_namespace(client_id, 'provider-b')
+
+        return #vim.diagnostic.get(diagnostic_bufnr, { namespace = first_ns }),
+          #vim.diagnostic.get(diagnostic_bufnr, { namespace = second_ns }),
+          #vim.diagnostic.get(diagnostic_bufnr),
+          first_ns,
+          second_ns
+      end)
+
+      eq(1, first_count)
+      eq(0, second_count)
+      eq(1, total_count)
+      neq(first_ns, second_ns)
+    end)
+
     it('handles multiline diagnostic ranges #33782', function()
       local diags = exec_lua(function()
         vim.lsp.diagnostic.on_diagnostic(nil, {