diff --git a/builtin/runtime/lsp.lua b/builtin/runtime/lsp.lua
index c0efb03..befc3ad 100644
--- a/builtin/runtime/lsp.lua
+++ b/builtin/runtime/lsp.lua
@@ -168,15 +168,17 @@ pmacs.lsp.config.dockerfile = pmacs.lsp.config.dockerfile or {
 }
 
 -- CMake via cmake-language-server (the Python server). It speaks LSP over
--- stdio with no transport flag and pulls configuration via
--- `workspace/configuration` under the `cmake` section (empty ⇒ defaults,
--- present not null — same rationale as gopls). It reads
--- `build/compile_commands.json` for the project model. Users populate
--- `settings.cmake` (buildDirectory, …) from init.lua.
+-- stdio with no transport flag. Unlike gopls/taplo it does NOT pull a
+-- `workspace/configuration` section: it reads `buildDirectory` from the
+-- `initialize` request's `initializationOptions`, and drives its project
+-- model off CMake's File API under `<buildDirectory>/.cmake/api/` (not
+-- `compile_commands.json`). So the config is an `init_options`, defaulting
+-- to the conventional out-of-source `build/`; users override
+-- `init_options.buildDirectory` from init.lua.
 pmacs.lsp.config.cmake = pmacs.lsp.config.cmake or {
   command = "cmake-language-server",
   args = {},
-  settings = { cmake = {} },
+  init_options = { buildDirectory = "build" },
 }
 
 -- TOML via taplo. `taplo lsp stdio` serves LSP over stdio. taplo
diff --git a/tests/m4_acceptance.rs b/tests/m4_acceptance.rs
index 9eecb53..3cc0462 100644
--- a/tests/m4_acceptance.rs
+++ b/tests/m4_acceptance.rs
@@ -6154,6 +6154,11 @@ fn m4_filename_map_resolves_special_files() {
             out.plain_is_nil = f('notes.txt') == nil
             out.cfg_docker = pmacs.lsp.config.dockerfile and pmacs.lsp.config.dockerfile.command
             out.cfg_cmake = pmacs.lsp.config.cmake and pmacs.lsp.config.cmake.command
+            -- cmake-language-server reads buildDirectory from
+            -- initializationOptions, not workspace/configuration.
+            out.cmake_builddir = pmacs.lsp.config.cmake
+                and pmacs.lsp.config.cmake.init_options
+                and pmacs.lsp.config.cmake.init_options.buildDirectory
             out.has_make_cfg = pmacs.lsp.config.make ~= nil
             return out
             ",
@@ -6181,6 +6186,11 @@ fn m4_filename_map_resolves_special_files() {
         probe.get::<String>("cfg_cmake").unwrap(),
         "cmake-language-server"
     );
+    assert_eq!(
+        probe.get::<String>("cmake_builddir").unwrap(),
+        "build",
+        "cmake config passes buildDirectory via init_options (not a workspace/configuration section)"
+    );
     assert!(
         !probe.get::<bool>("has_make_cfg").unwrap(),
         "Make has no language server, so no config.make"