diff --git a/handlers_test.v b/handlers_test.v
index c5a8cdaf..2f0f9ede 100644
--- a/handlers_test.v
+++ b/handlers_test.v
@@ -3765,7 +3765,7 @@ fn test_handle_rename_refuses_incomplete_oversized_sibling_index() {
 	test_file := os.join_path(test_dir, 'main.v')
 	content := 'module main\n\nfn target() {\n\ttarget()\n}\n'
 	must_write_file(test_file, content)
-	must_write_file(os.join_path(test_dir, 'oversized.v'), 'x'.repeat(index_max_file_bytes + 1))
+	must_write_file(os.join_path(test_dir, 'oversized.v'), 'x'.repeat(int(index_max_file_bytes) + 1))
 	uri := path_to_uri(test_file)
 	app.open_files[uri] = content
 
diff --git a/index_test.v b/index_test.v
index 3f459705..d78354b0 100644
--- a/index_test.v
+++ b/index_test.v
@@ -114,7 +114,7 @@ fn test_watched_file_reindex_drops_oversized_disk_entry() {
 	app.occurrences_for(uri)
 	assert uri in app.ref_occurrences
 
-	os.write_file(path, 'x'.repeat(index_max_file_bytes + 1)) or {
+	os.write_file(path, 'x'.repeat(int(index_max_file_bytes) + 1)) or {
 		assert false, 'grow watched file failed: ${err}'
 		return
 	}
@@ -816,7 +816,7 @@ fn test_index_completeness_is_scoped_to_relevant_project() {
 		return
 	}
 	path_b := os.join_path(root_b, 'oversized.v')
-	os.write_file(path_b, 'x'.repeat(index_max_file_bytes + 1)) or {
+	os.write_file(path_b, 'x'.repeat(int(index_max_file_bytes) + 1)) or {
 		assert false, 'write oversized root_b file failed: ${err}'
 		return
 	}
diff --git a/integration_test.v b/integration_test.v
index d3410bdf..f8e187bf 100644
--- a/integration_test.v
+++ b/integration_test.v
@@ -59,9 +59,9 @@ fn create_integration_test_env() (&App, string) {
 	integration_test_must_mkdir_all(project_dir)
 
 	app := &App{
-		text: ''
+		text:       ''
 		open_files: map[string]string{}
-		temp_dir: temp_dir
+		temp_dir:   temp_dir
 	}
 	return app, project_dir
 }
@@ -2793,13 +2793,14 @@ fn test_integration_sublime_text_lsp_handshake() {
 		cleanup_integration_test_env(app, project_dir)
 	}
 	root_uri := path_to_uri(project_dir)
-	initialize := '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"processId":42,"clientInfo":{"name":"Sublime Text LSP","version":"2.13.0"},"locale":"en","rootUri":"${root_uri}","rootPath":"${project_dir}","workspaceFolders":[{"uri":"${root_uri}","name":"test_project"}],"capabilities":{"general":{"positionEncodings":["utf-16"]},"workspace":{"workspaceFolders":true,"configuration":true,"didChangeWatchedFiles":{"dynamicRegistration":true,"relativePatternSupport":true}},"textDocument":{"synchronization":{"dynamicRegistration":true,"willSave":true,"willSaveWaitUntil":true,"didSave":true},"completion":{"dynamicRegistration":true,"completionItem":{"snippetSupport":true,"documentationFormat":["markdown","plaintext"]}},"hover":{"dynamicRegistration":true,"contentFormat":["markdown","plaintext"]},"publishDiagnostics":{"versionSupport":true}},"window":{"workDoneProgress":true}},"initializationOptions":{}}}'
+	json_root_path := project_dir.replace('\\', '\\\\')
+	initialize := '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"processId":42,"clientInfo":{"name":"Sublime Text LSP","version":"2.13.0"},"locale":"en","rootUri":"${root_uri}","rootPath":"${json_root_path}","workspaceFolders":[{"uri":"${root_uri}","name":"test_project"}],"capabilities":{"general":{"positionEncodings":["utf-16"]},"workspace":{"workspaceFolders":true,"configuration":true,"didChangeWatchedFiles":{"dynamicRegistration":true,"relativePatternSupport":true}},"textDocument":{"synchronization":{"dynamicRegistration":true,"willSave":true,"willSaveWaitUntil":true,"didSave":true},"completion":{"dynamicRegistration":true,"completionItem":{"snippetSupport":true,"documentationFormat":["markdown","plaintext"]}},"hover":{"dynamicRegistration":true,"contentFormat":["markdown","plaintext"]},"publishDiagnostics":{"versionSupport":true}},"window":{"workDoneProgress":true}},"initializationOptions":{}}}'
 	initialized := '{"jsonrpc":"2.0","method":"initialized","params":{}}'
 	output := integration_run_frames(mut app, project_dir, 'sublime_handshake', [initialize,
 		initialized])
 
 	assert app.received_initialize
-	assert app.workspace_roots == [project_dir]
+	assert app.workspace_roots == [project_dir.replace('\\', '/')]
 	assert app.position_encoding == .utf16
 	assert app.supports_dynamic_watched_files_registration
 	assert app.supports_work_done_progress
diff --git a/interop.v b/interop.v
index 0aad112f..c798b8f0 100644
--- a/interop.v
+++ b/interop.v
@@ -12,9 +12,51 @@ import time
 fn resolve_v_compiler_exe() string {
 	configured := os.getenv('VLS_V_COMMAND').trim_space()
 	if configured != '' {
+		unwrapped := resolve_wrapper_target(configured)
+		if unwrapped != '' {
+			return unwrapped
+		}
 		return configured
 	}
-	return os.find_abs_path_of_executable('v') or { 'v' }
+	found := os.find_abs_path_of_executable('v') or { 'v' }
+	unwrapped := resolve_wrapper_target(found)
+	if unwrapped != '' {
+		return unwrapped
+	}
+	return found
+}
+
+// resolve_wrapper_target unwraps a Windows launcher shim (a `.bat`/`.cmd`
+// file that forwards to the real compiler executable) so compiler-relative
+// lookups such as the vlib directory resolve against the real installation
+// instead of the shim's directory. It returns '' when `candidate` is not a
+// wrapper or no usable target is found, in which case the caller keeps the
+// original path.
+fn resolve_wrapper_target(candidate string) string {
+	if candidate == '' || candidate == 'v' {
+		return ''
+	}
+	lower := candidate.to_lower()
+	if !(lower.ends_with('.bat') || lower.ends_with('.cmd')) {
+		return ''
+	}
+	content := os.read_file(candidate) or { return '' }
+	for line in content.split_into_lines() {
+		trimmed := line.trim_space()
+		if !trimmed.starts_with('"') {
+			continue
+		}
+		end := trimmed[1..].index('"') or { continue }
+		target := trimmed[1..end + 1]
+		target_lower := target.to_lower()
+		if target_lower.ends_with('.bat') || target_lower.ends_with('.cmd') {
+			continue
+		}
+		if os.is_file(target) {
+			return target
+		}
+	}
+	return ''
 }
 
 // compiler_is_available reports whether the V compiler was resolved to a real
@@ -267,7 +309,8 @@ fn build_v_check_args_multifile(is_library_module bool) []string {
 }
 
 fn build_v_line_info_args_multifile(rel_file string, line_info string) []string {
-	return ['-w', '-check', '-nocolor', '-vls-mode', '-line-info', '${rel_file}:${line_info}', '.']
+	return ['-w', '-check', '-nocolor', '-vls-mode', '-line-info', '${rel_file}:${line_info}',
+		'.']
 }
 
 fn build_v_line_info_args_single(file_to_check string, line_info string, compile_target string) []string {
@@ -284,8 +327,8 @@ fn build_v_line_info_args_single(file_to_check string, line_info string, compile
 // than assumed from a version number.
 enum LineInfoMode {
 	unknown // not probed yet — try the options as-is
-	direct // the compiler answers `-vls-mode` / `-line-info` itself
-	compat // reaching the checker needs `-old-compiler`
+	direct  // the compiler answers `-vls-mode` / `-line-info` itself
+	compat  // reaching the checker needs `-old-compiler`
 	missing // no compatibility compiler either — answer from VLS's own index
 }
 
@@ -338,6 +381,56 @@ fn compiler_refused_and_stopped(output string) bool {
 	return refusals > 0
 }
 
+// compiler_lacks_compatibility_compiler reports whether an invocation failed
+// because the V launcher could not reach the V1 compatibility compiler, which is
+// what owns `-vls-mode` / `-line-info`. The launcher prints a single-line
+// refusal and exits without compiling, and that refusal is not an "unknown
+// option" line, so `compiler_rejects_line_info` never sees it. Without this
+// check VLS keeps paying a process launch per request for an answer that can
+// never arrive, and answers every hover, completion, and definition with an
+// empty result while saying nothing about why. Each refusal form below is one
+// `ensure_v1_fallback` failure in the launcher.
+fn compiler_lacks_compatibility_compiler(output string) bool {
+	for line in output.split_into_lines() {
+		trimmed := line.trim_space()
+		if trimmed == '' {
+			continue
+		}
+		// A launcher that can build the fallback itself announces that first and
+		// then answers the request, so this form must retire nothing.
+		if trimmed.contains('running `make v1` now') {
+			return false
+		}
+		if trimmed.contains('requires the compatibility compiler') {
+			return true
+		}
+		if trimmed.contains('`-old-compiler` was requested') {
+			return true
+		}
+		if trimmed.starts_with('`make v1` failed') {
+			return true
+		}
+		if trimmed.starts_with('`make v1` completed without installing') {
+			return true
+		}
+	}
+	return false
+}
+
+// report_missing_compatibility_compiler tells the user that the configured `v`
+// cannot serve the compiler-backed lookups, and how to fix it. Without this the
+// editor shows a VLS that highlights code but silently answers nothing for
+// completion, hover, signature help, and go to definition, which is
+// indistinguishable from VLS being broken.
+//
+// No "already warned" flag is needed: the caller sets `line_info_mode` to
+// `.missing` first, and from then on `run_v_line_info` returns from its early
+// `.missing` check without reaching this point, so it is reached at most once per
+// session.
+fn (mut app App) report_missing_compatibility_compiler() {
+	app.send_show_message('vls: the V compiler on PATH cannot serve completion, hover, signature help, or go to definition, because its V1 compatibility compiler is missing. Install `make`, then run `make v1` in your V source directory, or point `v.vls.command` at a V that has it. Diagnostics and formatting are unaffected.', 2)
+}
+
 // normalize_v_line_info_output extracts the actual line-info payload from the
 // compatibility compiler's combined stdout/stderr. Newer launchers may prepend
 // an option notice before delegating to the established compiler.
@@ -465,11 +558,11 @@ fn parse_v_check_diagnostic_header(line string, source_dir string) ?JsonError {
 			if marker_idx > best_marker_idx {
 				best_marker_idx = marker_idx
 				best = JsonError{
-					path: path
+					path:    path
 					message: line[marker_idx + marker.len..]
 					line_nr: line_nr_text.int()
-					col: col_text.int()
-					level: if level.contains('error') { 'error' } else { level }
+					col:     col_text.int()
+					level:   if level.contains('error') { 'error' } else { level }
 				}
 			}
 			break
@@ -517,8 +610,8 @@ fn (mut app App) cache_v_check_result(path string, content_hash int, generation
 	}
 	app.diag_cache[path] = DiagCacheEntry{
 		content_hash: content_hash
-		generation: generation
-		errors: errors
+		generation:   generation
+		errors:       errors
 	}
 }
 
@@ -553,7 +646,7 @@ fn run_v_argv(args []string, work_folder string) os.Result {
 		log(msg)
 		return os.Result{
 			exit_code: 1
-			output: msg
+			output:    msg
 		}
 	}
 	v_exe := resolve_v_compiler_exe()
@@ -615,12 +708,12 @@ fn run_v_argv(args []string, work_folder string) os.Result {
 	if timed_out {
 		return os.Result{
 			exit_code: compiler_exit_timeout
-			output: ''
+			output:    ''
 		}
 	}
 	return os.Result{
 		exit_code: code
-		output: out.str()
+		output:    out.str()
 	}
 }
 
@@ -728,23 +821,24 @@ fn (mut app App) prepare_compilation_overlay(real_path string) !CompilationOverl
 		}
 	}
 	return CompilationOverlay{
-		source_root: source_root
+		source_root:         source_root
 		source_display_root: source_display_root
-		temp_root: temp_root
-		source_work_dir: source_work_dir
-		temp_work_dir: temp_work_dir
-		temp_source_file: os.join_path(temp_root, file_rel)
+		temp_root:           temp_root
+		source_work_dir:     source_work_dir
+		temp_work_dir:       temp_work_dir
+		temp_source_file:    os.join_path(temp_root, file_rel)
 	}
 }
 
 // source_path_from_overlay maps compiler paths in the temporary project back to
 // their original source paths.
-fn source_path_from_overlay_with_windows_rules(reported_path string, overlay CompilationOverlay, windows bool) string {
+fn source_path_from_overlay_with_windows_rules(reported_path string, overlay CompilationOverlay, windows bool, base_dir string) string {
 	mut candidate := normalize_overlay_path_with_windows_rules(reported_path, windows)
+	resolve_base := if base_dir != '' { base_dir } else { overlay.temp_work_dir }
 	if candidate.starts_with('./') || candidate.starts_with('.\\') {
-		candidate = os.join_path(overlay.temp_work_dir, candidate[2..])
+		candidate = os.join_path(resolve_base, candidate[2..])
 	} else if !os.is_abs_path(candidate) {
-		candidate = os.join_path(overlay.temp_work_dir, candidate)
+		candidate = os.join_path(resolve_base, candidate)
 	}
 	candidate = normalize_overlay_path_with_windows_rules(candidate, windows)
 	temp_root := normalize_overlay_path_with_windows_rules(overlay.temp_root, windows)
@@ -755,11 +849,11 @@ fn source_path_from_overlay_with_windows_rules(reported_path string, overlay Com
 	return candidate
 }
 
-fn source_path_from_overlay(reported_path string, overlay CompilationOverlay) string {
+fn source_path_from_overlay(reported_path string, overlay CompilationOverlay, base_dir string) string {
 	$if windows {
-		return source_path_from_overlay_with_windows_rules(reported_path, overlay, true)
+		return source_path_from_overlay_with_windows_rules(reported_path, overlay, true, base_dir)
 	}
-	return source_path_from_overlay_with_windows_rules(reported_path, overlay, false)
+	return source_path_from_overlay_with_windows_rules(reported_path, overlay, false, base_dir)
 }
 
 fn (mut app App) run_v_check(path string, text string) []JsonError {
@@ -837,15 +931,15 @@ fn (mut app App) run_v_check(path string, text string) []JsonError {
 		mut filtered_errors := []JsonError{}
 
 		for err in v_errors {
-			err_file := source_path_from_overlay(err.path, overlay)
+			err_file := source_path_from_overlay(err.path, overlay, compile_target)
 			if normalized_index_path(err_file) == normalized_index_path(real_path) {
 				updated_err := JsonError{
-					path: real_path
+					path:    real_path
 					message: err.message
 					line_nr: err.line_nr
-					col: err.col
-					len: err.len
-					level: err.level
+					col:     err.col
+					len:     err.len
+					level:   err.level
 				}
 				filtered_errors << updated_err
 				log('INCLUDING ERROR from err_file=${err_file}: ${err.message}')
@@ -1513,7 +1607,7 @@ fn (mut app App) line_info_unavailable_result(method Method, path string, line_i
 			}
 			return Hover{
 				contents: MarkupContent{
-					kind: 'markdown'
+					kind:  'markdown'
 					value: doc
 				}
 			}
@@ -1630,7 +1724,7 @@ fn (mut app App) run_v_line_info(method Method, path string, line_info string) R
 			output = normalize_v_line_info_output(x.output, method)
 		}
 	}
-	if compiler_rejects_line_info(x.output) && compiler_refused_and_stopped(x.output) {
+	if (compiler_rejects_line_info(x.output) && compiler_refused_and_stopped(x.output)) || compiler_lacks_compatibility_compiler(x.output) {
 		// The invocation refused the options and did nothing else, so nothing
 		// here can answer and the single-file retry below would be refused for
 		// the same reason. An empty payload alone is not evidence: on a launcher
@@ -1639,6 +1733,7 @@ fn (mut app App) run_v_line_info(method Method, path string, line_info string) R
 		// compiler-backed hover, signature, and receiver definition.
 		log('no compiler serves -line-info; falling back to the index')
 		app.line_info_mode = .missing
+		app.report_missing_compatibility_compiler()
 		cleanup_compilation_temp(temp_project_dir, singlefile_tmppath)
 		return app.line_info_unavailable_result(method, path, line_info)
 	}
@@ -1696,7 +1791,7 @@ fn (mut app App) run_v_line_info(method Method, path string, line_info string) R
 				}
 				result = Hover{
 					contents: MarkupContent{
-						kind: 'markdown'
+						kind:  'markdown'
 						value: value
 					}
 				}
@@ -1704,7 +1799,7 @@ fn (mut app App) run_v_line_info(method Method, path string, line_info string) R
 				// Compiler returned no info but we found a vdoc comment
 				result = Hover{
 					contents: MarkupContent{
-						kind: 'markdown'
+						kind:  'markdown'
 						value: doc
 					}
 				}
@@ -1725,7 +1820,7 @@ fn (mut app App) run_v_line_info(method Method, path string, line_info string) R
 				col := fields[fields.len - 1].int()
 				mut uri_path := os.to_slash(fields[..fields.len - 2].join(':'))
 				if use_multifile && temp_project_dir != '' {
-					uri_path = source_path_from_overlay(uri_path, overlay)
+					uri_path = source_path_from_overlay(uri_path, overlay, compile_target)
 					log('MAPPED TO uri_path=${uri_path}')
 				}
 				// Build a proper percent-encoded DocumentUri so paths containing
@@ -1749,13 +1844,13 @@ fn (app &App) compiler_location(path string, line int, byte_col int) Location {
 	target_uri := index_uri_for_path(path, app.open_index_uris_by_path())
 	client_col := app.byte_col_to_client_col(target_uri, line, byte_col)
 	return Location{
-		uri: target_uri
+		uri:   target_uri
 		range: LSPRange{
 			start: Position{
 				line: line
 				char: client_col
 			}
-			end: Position{
+			end:   Position{
 				line: line
 				char: client_col
 			}
diff --git a/interop_test.v b/interop_test.v
index 3f03a75a..5d817ff7 100644
--- a/interop_test.v
+++ b/interop_test.v
@@ -38,6 +38,80 @@ fn test_resolve_v_compiler_exe_prefers_configured_command() {
 	assert resolve_v_compiler_exe() == configured
 }
 
+fn test_resolve_wrapper_target_ignores_plain_executable() {
+	assert resolve_wrapper_target('C:\\v\\v.exe') == ''
+	assert resolve_wrapper_target('/usr/local/bin/v') == ''
+	assert resolve_wrapper_target('') == ''
+	assert resolve_wrapper_target('v') == ''
+}
+
+fn test_resolve_wrapper_target_ignores_missing_wrapper() {
+	missing := os.join_path(os.temp_dir(), 'vls_no_such_wrapper_${os.getpid()}.bat')
+	assert resolve_wrapper_target(missing) == ''
+}
+
+fn test_resolve_wrapper_target_unwraps_bat_forwarding_to_exe() {
+	base := os.join_path(os.temp_dir(), 'vls_wrapper_probe_${os.getpid()}')
+	bin := os.join_path(base, '.bin')
+	interop_test_must_mkdir_all(bin)
+	defer {
+		os.rmdir_all(base) or {}
+	}
+	target := os.join_path(base, 'v.exe')
+	interop_test_must_write_file(target, '')
+	wrapper := os.join_path(bin, 'v.bat')
+	interop_test_must_write_file(wrapper, '@echo off\n"${target}" %*\n')
+	assert resolve_wrapper_target(wrapper) == target
+}
+
+fn test_resolve_wrapper_target_ignores_bat_without_quoted_target() {
+	base := os.join_path(os.temp_dir(), 'vls_wrapper_bare_${os.getpid()}')
+	interop_test_must_mkdir_all(base)
+	defer {
+		os.rmdir_all(base) or {}
+	}
+	wrapper := os.join_path(base, 'v.bat')
+	interop_test_must_write_file(wrapper, '@echo off\nv.exe %*\n')
+	assert resolve_wrapper_target(wrapper) == ''
+}
+
+fn test_resolve_wrapper_target_ignores_wrapper_chain() {
+	base := os.join_path(os.temp_dir(), 'vls_wrapper_chain_${os.getpid()}')
+	interop_test_must_mkdir_all(base)
+	defer {
+		os.rmdir_all(base) or {}
+	}
+	inner := os.join_path(base, 'inner.bat')
+	interop_test_must_write_file(inner, '@echo off\necho hi\n')
+	outer := os.join_path(base, 'outer.bat')
+	interop_test_must_write_file(outer, '@echo off\n"${inner}" %*\n')
+	assert resolve_wrapper_target(outer) == ''
+}
+
+fn test_resolve_v_compiler_exe_unwraps_configured_wrapper() {
+	old_command := os.getenv('VLS_V_COMMAND')
+	defer {
+		if old_command == '' {
+			os.unsetenv('VLS_V_COMMAND')
+		} else {
+			os.setenv('VLS_V_COMMAND', old_command, true)
+		}
+	}
+	base := os.join_path(os.temp_dir(), 'vls_wrapper_env_${os.getpid()}')
+	bin := os.join_path(base, '.bin')
+	interop_test_must_mkdir_all(bin)
+	defer {
+		os.rmdir_all(base) or {}
+	}
+	target := os.join_path(base, 'v.exe')
+	interop_test_must_write_file(target, '')
+	wrapper := os.join_path(bin, 'v.bat')
+	interop_test_must_write_file(wrapper, '@echo off\n"${target}" %*\n')
+	os.setenv('VLS_V_COMMAND', wrapper, true)
+	assert resolve_v_compiler_exe() == target
+	assert find_v_dir() == os.dir(os.real_path(target))
+}
+
 // --- uri_to_path tests ---
 
 fn test_uri_to_path_unix_style() {
@@ -164,10 +238,10 @@ fn test_normalize_overlay_path_preserves_posix_backslashes() {
 fn test_source_path_from_overlay_normalizes_windows_relative_join() {
 	overlay := CompilationOverlay{
 		source_display_root: r'C:\repo'
-		temp_root: r'C:\temp\overlay'
-		temp_work_dir: r'C:\temp\overlay\src'
+		temp_root:           r'C:\temp\overlay'
+		temp_work_dir:       r'C:\temp\overlay\src'
 	}
-	mapped := source_path_from_overlay_with_windows_rules('./main.v', overlay, true)
+	mapped := source_path_from_overlay_with_windows_rules('./main.v', overlay, true, '')
 	assert mapped == 'C:/repo/src/main.v'
 }
 
@@ -257,7 +331,7 @@ fn test_compiler_location_reuses_equivalent_open_uri() {
 	canonical_uri := path_to_uri(path)
 	open_uri := canonical_uri.replace_once('file:///', 'file://localhost/')
 	mut app := &App{
-		open_files: map[string]string{}
+		open_files:        map[string]string{}
 		position_encoding: .utf16
 	}
 	app.open_files[open_uri] = '🚀 target\n'
@@ -471,6 +545,103 @@ fn test_compiler_refused_and_stopped_separates_a_dead_end_from_a_recovery() {
 	assert !compiler_refused_and_stopped('./main.v:3:7')
 }
 
+fn test_compiler_lacks_compatibility_compiler_detects_every_launcher_refusal() {
+	// These are the single-line refusals `ensure_v1_fallback` prints in the V
+	// launcher, verbatim. None of them is an "unknown option" line, so before
+	// this was recognized VLS never retired the lookups and never said anything.
+	assert compiler_lacks_compatibility_compiler('`-vls-mode` requires the compatibility compiler, but no usable V 0.5.2 fallback was found and make is unavailable. Install make, then run `make v1` in `C:\\Users\\me\\v`.')
+	// vlang/v#29369 rewrote the tail of that refusal: the hint after "make is
+	// unavailable" is now platform specific, and the sentence is split. Detection
+	// keys on "requires the compatibility compiler", so both spellings must retire
+	// the lookups, and this test has to hold either side of that change.
+	assert compiler_lacks_compatibility_compiler('`-vls-mode` requires the compatibility compiler, but no usable V 0.5.2 fallback was found and make is unavailable. On Windows, install GNU make in MSYS2 (`make` or `mingw32-make`) and put its tools, including `sh`, on PATH. Then run `make v1` in `C:\\Users\\me\\v`.')
+	assert compiler_lacks_compatibility_compiler('`-vls-mode` requires the compatibility compiler, but the V source tree could not be found. Run `make v1` in the V source directory.')
+	assert compiler_lacks_compatibility_compiler('`-old-compiler` was requested, but no usable V 0.5.2 fallback was found and make is unavailable. Install make, then run `make v1` in `/home/me/v`.')
+	// The same rewrite as above, on the host where the hint is the short one.
+	assert compiler_lacks_compatibility_compiler('`-old-compiler` was requested, but no usable V 0.5.2 fallback was found and make is unavailable. Install make. Then run `make v1` in `/home/me/v`.')
+	assert compiler_lacks_compatibility_compiler('`make v1` failed with exit code 2. Run it manually in `/home/me/v` for more details.')
+	assert compiler_lacks_compatibility_compiler('`make v1` completed without installing a usable V 0.5.2 fallback at `/home/me/.cache/v1_fallback`.')
+	// A launcher that recovers on its own only announces the fallback before
+	// rerunning, then answers. Retiring the lookups on that would cost the
+	// session every compiler-backed hover, signature, and receiver definition.
+	assert !compiler_lacks_compatibility_compiler('unknown option `-vls-mode`')
+	assert !compiler_lacks_compatibility_compiler('unknown option `-vls-mode`\nV compilation failed (compiler_error); retrying with `/v1_fallback`.')
+	assert !compiler_lacks_compatibility_compiler('`-vls-mode` requires the compatibility compiler, but no usable V 0.5.2 fallback was found; running `make v1` now...\n{"contents":{"kind":"markdown","value":"fn f()"}}')
+	// A working compiler's payload, an ordinary diagnostic, and empty output.
+	assert !compiler_lacks_compatibility_compiler('{"contents":{"kind":"markdown","value":"fn f()"}}')
+	assert !compiler_lacks_compatibility_compiler('./main.v:3:7: error: unknown option')
+	assert !compiler_lacks_compatibility_compiler('')
+}
+
+// A launcher that understands `-vls-mode` but cannot reach the compatibility
+// compiler that implements it, and stops there. Its refusal is not an "unknown
+// option" line, which is what made it invisible to the dead-end check.
+const no_compat_compiler_launcher_stub = r'#!/bin/sh
+echo "\`-vls-mode\` requires the compatibility compiler, but no usable V 0.5.2 fallback was found and make is unavailable. Install make, then run \`make v1\` in \`/v\`." >&2
+exit 1
+'
+
+fn test_run_v_line_info_retires_lookups_when_the_compatibility_compiler_is_missing() {
+	$if windows {
+		// The stand-in launcher is a POSIX shell script.
+		return
+	}
+	previous := os.getenv('VLS_V_COMMAND')
+	mut app, uri, root := line_info_stub_app('vls_no_compat_compiler', no_compat_compiler_launcher_stub)
+	defer {
+		restore_v_command(previous)
+		os.rmdir_all(root) or {}
+	}
+
+	assert app.run_v_line_info(.hover, uri, '6:hv^4') == ResponseResult('null')
+	assert app.line_info_mode == .missing
+}
+
+fn test_report_missing_compatibility_compiler_names_the_repair() {
+	// The editor otherwise shows a VLS that highlights code but answers nothing
+	// for completion, hover, signature help, or go to definition, with no hint
+	// that the compiler is the reason. Platform-independent: no stub compiler.
+	mut app := App{
+		capture_output: true
+	}
+	app.report_missing_compatibility_compiler()
+	assert app.captured_output.len == 1
+	assert app.captured_output[0].contains('window/showMessage')
+	// Name the actual repair, not just the symptom.
+	assert app.captured_output[0].contains('make v1')
+	assert app.captured_output[0].contains('type":2')
+}
+
+fn test_a_retired_lookup_never_reports_the_missing_compiler_again() {
+	// Once the lookups are retired, `run_v_line_info` answers from the index at
+	// its early `.missing` check, so it never spawns the compiler and never
+	// re-reports. That structural guarantee is why the notice needs no
+	// "already warned" flag.
+	previous := os.getenv('VLS_V_COMMAND')
+	mut app := App{
+		capture_output: true
+		line_info_mode: .missing
+		open_files:     map[string]string{}
+	}
+	uri := 'file:///tmp/vls_retired_lookup.v'
+	app.open_files[uri] = 'module main\n\n// greet writes a greeting.\nfn greet() {}\n\nfn main() {\n\tgreet()\n}\n'
+	// A compiler that cannot be spawned at all: reaching it would fail loudly.
+	os.setenv('VLS_V_COMMAND', os.join_path(os.temp_dir(), 'vls_no_such_compiler'), true)
+	defer {
+		restore_v_command(previous)
+	}
+
+	hover := app.run_v_line_info(.hover, uri, '7:hv^1')
+	// Answered from the index, from the document's own vdoc comment.
+	assert hover is Hover
+	if hover is Hover {
+		assert hover.contents.value.contains('greet writes a greeting.')
+	}
+	// Nothing was said to the client, and no compiler was launched.
+	assert app.captured_output.len == 0
+	assert app.line_info_mode == .missing
+}
+
 // line_info_stub_app writes `script` as an executable stand-in for `v`, points
 // VLS_V_COMMAND at it, and returns an App plus the URI of a lone source file.
 // The source sits in its own directory so the request takes the single-file
@@ -641,12 +812,12 @@ fn test_parse_v_check_diagnostics_reads_v3_output() {
 	diagnostics := parse_v_check_diagnostics(output, '')
 	assert diagnostics.len == 2
 	assert diagnostics[0] == JsonError{
-		path: '/tmp/main.v'
+		path:    '/tmp/main.v'
 		message: 'undefined variable: `missing_name`'
 		line_nr: 4
-		col: 7
-		len: 12
-		level: 'error'
+		col:     7
+		len:     12
+		level:   'error'
 	}
 	assert diagnostics[1].level == 'warning'
 	assert diagnostics[1].line_nr == 8
@@ -661,12 +832,12 @@ fn test_parse_v_check_diagnostics_maps_v3_builder_error_to_error() {
 '
 	diagnostics := parse_v_check_diagnostics(output, '')
 	assert diagnostics == [JsonError{
-		path: '/tmp/main.v'
+		path:    '/tmp/main.v'
 		message: 'cannot import module "missing" (not found)'
 		line_nr: 3
-		col: 1
-		len: 14
-		level: 'error'
+		col:     1
+		len:     14
+		level:   'error'
 	}]
 }
 
@@ -743,8 +914,8 @@ fn test_cache_v_check_result_retries_failure_without_diagnostics() {
 	path := 'file:///tmp/main.v'
 	app.diag_cache[path] = DiagCacheEntry{
 		content_hash: 1
-		generation: 1
-		errors: []
+		generation:   1
+		errors:       []
 	}
 	app.cache_v_check_result(path, 2, 2, [], compiler_exit_timeout, 0)
 	assert path !in app.diag_cache
@@ -755,16 +926,16 @@ fn test_cache_v_check_result_retries_timeout_with_partial_diagnostics() {
 	path := 'file:///tmp/main.v'
 	app.diag_cache[path] = DiagCacheEntry{
 		content_hash: 1
-		generation: 1
-		errors: []
+		generation:   1
+		errors:       []
 	}
 	partial_errors := [
 		JsonError{
-			path: '/tmp/main.v'
+			path:    '/tmp/main.v'
 			message: 'partial compiler output'
 			line_nr: 1
-			col: 1
-			level: 'error'
+			col:     1
+			level:   'error'
 		},
 	]
 	app.cache_v_check_result(path, 2, 2, partial_errors, compiler_exit_timeout, partial_errors.len)
@@ -799,11 +970,11 @@ fn test_run_v_argv_reports_missing_working_dir() {
 
 fn test_v_error_to_lsp_diagnostic_basic() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'undefined identifier `foo`'
 		line_nr: 10
-		col: 5
-		len: 3
+		col:     5
+		len:     3
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -818,11 +989,11 @@ fn test_v_error_to_lsp_diagnostic_basic() {
 
 fn test_v_error_to_lsp_diagnostic_first_line() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'syntax error'
 		line_nr: 1
-		col: 1
-		len: 1
+		col:     1
+		len:     1
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -833,11 +1004,11 @@ fn test_v_error_to_lsp_diagnostic_first_line() {
 
 fn test_v_error_to_lsp_diagnostic_long_error() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'unexpected token'
 		line_nr: 100
-		col: 50
-		len: 20
+		col:     50
+		len:     20
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -848,11 +1019,11 @@ fn test_v_error_to_lsp_diagnostic_long_error() {
 
 fn test_v_error_to_lsp_diagnostic_zero_length() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'error at position'
 		line_nr: 5
-		col: 10
-		len: 0
+		col:     10
+		len:     0
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -862,11 +1033,11 @@ fn test_v_error_to_lsp_diagnostic_zero_length() {
 
 fn test_v_error_to_lsp_diagnostic_large_line_numbers() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'error in large file'
 		line_nr: 10000
-		col: 200
-		len: 50
+		col:     200
+		len:     50
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -877,11 +1048,11 @@ fn test_v_error_to_lsp_diagnostic_large_line_numbers() {
 
 fn test_v_error_to_lsp_diagnostic_column_one() {
 	v_err := JsonError{
-		path: '/test/file.v'
+		path:    '/test/file.v'
 		message: 'error at start of line'
 		line_nr: 5
-		col: 1
-		len: 5
+		col:     1
+		len:     5
 	}
 	diag := v_error_to_lsp_diagnostic(v_err)
 
@@ -917,7 +1088,7 @@ fn test_lsp_range_struct() {
 			line: 0
 			char: 0
 		}
-		end: Position{
+		end:   Position{
 			line: 0
 			char: 10
 		}
@@ -932,7 +1103,7 @@ fn test_lsp_range_multiline() {
 			line: 5
 			char: 10
 		}
-		end: Position{
+		end:   Position{
 			line: 10
 			char: 5
 		}
@@ -942,17 +1113,17 @@ fn test_lsp_range_multiline() {
 
 fn test_lsp_diagnostic_struct() {
 	diag := LSPDiagnostic{
-		range: LSPRange{
+		range:    LSPRange{
 			start: Position{
 				line: 5
 				char: 0
 			}
-			end: Position{
+			end:   Position{
 				line: 5
 				char: 10
 			}
 		}
-		message: 'test error'
+		message:  'test error'
 		severity: 1
 	}
 	assert diag.message == 'test error'
@@ -965,8 +1136,8 @@ fn test_lsp_diagnostic_severities() {
 	severities := [1, 2, 3, 4] // Error, Warning, Information, Hint
 	for sev in severities {
 		diag := LSPDiagnostic{
-			range: LSPRange{}
-			message: 'test'
+			range:    LSPRange{}
+			message:  'test'
 			severity: sev
 		}
 		assert diag.severity == sev
@@ -975,13 +1146,13 @@ fn test_lsp_diagnostic_severities() {
 
 fn test_location_struct() {
 	loc := Location{
-		uri: 'file:///test/file.v'
+		uri:   'file:///test/file.v'
 		range: LSPRange{
 			start: Position{
 				line: 10
 				char: 5
 			}
-			end: Position{
+			end:   Position{
 				line: 10
 				char: 15
 			}
@@ -999,9 +1170,9 @@ fn test_location_empty() {
 
 fn test_detail_struct() {
 	detail := Detail{
-		kind: 6 // Function
-		label: 'my_function'
-		detail: 'fn my_function() string'
+		kind:          6 // Function
+		label:         'my_function'
+		detail:        'fn my_function() string'
 		documentation: 'A helper function'
 	}
 	assert detail.kind == 6
@@ -1014,7 +1185,7 @@ fn test_detail_kinds() {
 	kinds := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] // Text, Method, Function, etc.
 	for k in kinds {
 		detail := Detail{
-			kind: k
+			kind:  k
 			label: 'test'
 		}
 		assert detail.kind == k
@@ -1023,11 +1194,11 @@ fn test_detail_kinds() {
 
 fn test_detail_struct_with_snippet() {
 	detail := Detail{
-		kind: 6
-		label: 'println'
-		detail: 'fn println(s string)'
-		documentation: 'Prints a string'
-		insert_text: 'println(\${1:s})'
+		kind:               6
+		label:              'println'
+		detail:             'fn println(s string)'
+		documentation:      'Prints a string'
+		insert_text:        'println(\${1:s})'
 		insert_text_format: 2 // Snippet format
 	}
 	assert detail.insert_text? == 'println(\${1:s})'
@@ -1036,7 +1207,7 @@ fn test_detail_struct_with_snippet() {
 
 fn test_detail_without_snippet() {
 	detail := Detail{
-		kind: 6
+		kind:  6
 		label: 'println'
 	}
 	assert detail.insert_text == none
@@ -1045,9 +1216,9 @@ fn test_detail_without_snippet() {
 
 fn test_signature_help_struct() {
 	sig := SignatureHelp{
-		signatures: [
+		signatures:       [
 			SignatureInformation{
-				label: 'fn my_func(a int, b string) bool'
+				label:      'fn my_func(a int, b string) bool'
 				parameters: [
 					ParameterInformation{
 						label: 'a int'
@@ -1068,7 +1239,7 @@ fn test_signature_help_struct() {
 
 fn test_signature_help_multiple_signatures() {
 	sig := SignatureHelp{
-		signatures: [
+		signatures:       [
 			SignatureInformation{
 				label: 'fn overload1(a int)'
 			},
@@ -1096,17 +1267,17 @@ fn test_signature_help_empty() {
 fn test_capabilities_struct() {
 	cap := Capabilities{
 		capabilities: Capability{
-			text_document_sync: TextDocumentSyncOptions{
+			text_document_sync:      TextDocumentSyncOptions{
 				open_close: true
-				change: 1
+				change:     1
 			}
-			completion_provider: CompletionProvider{
+			completion_provider:     CompletionProvider{
 				trigger_characters: ['.']
 			}
 			signature_help_provider: SignatureHelpOptions{
 				trigger_characters: ['(', ',']
 			}
-			definition_provider: true
+			definition_provider:     true
 		}
 	}
 	assert cap.capabilities.definition_provider == true
@@ -1127,11 +1298,11 @@ fn test_capabilities_minimal() {
 
 fn test_request_struct() {
 	req := Request{
-		id: 1
-		method: 'textDocument/completion'
+		id:      1
+		method:  'textDocument/completion'
 		jsonrpc: '2.0'
-		params: json2.encode(Params{
-			position: Position{
+		params:  json2.encode(Params{
+			position:      Position{
 				line: 5
 				char: 10
 			}
@@ -1162,7 +1333,7 @@ fn test_request_params_decode_malformed_returns_error() {
 
 fn test_response_struct() {
 	resp := Response{
-		id: 1
+		id:     1
 		result: 'null'
 	}
 	assert resp.id == 1
@@ -1171,7 +1342,7 @@ fn test_response_struct() {
 
 fn test_response_with_capabilities() {
 	resp := Response{
-		id: 0
+		id:     0
 		result: Capabilities{
 			capabilities: Capability{
 				definition_provider: true
@@ -1188,7 +1359,7 @@ fn test_notification_struct() {
 	notif := Notification{
 		method: 'textDocument/publishDiagnostics'
 		params: PublishDiagnosticsParams{
-			uri: 'file:///test.v'
+			uri:         'file:///test.v'
 			diagnostics: []
 		}
 	}
@@ -1200,16 +1371,16 @@ fn test_notification_with_diagnostics() {
 	notif := Notification{
 		method: 'textDocument/publishDiagnostics'
 		params: PublishDiagnosticsParams{
-			uri: 'file:///test.v'
+			uri:         'file:///test.v'
 			diagnostics: [
 				LSPDiagnostic{
-					range: LSPRange{}
-					message: 'error 1'
+					range:    LSPRange{}
+					message:  'error 1'
 					severity: 1
 				},
 				LSPDiagnostic{
-					range: LSPRange{}
-					message: 'error 2'
+					range:    LSPRange{}
+					message:  'error 2'
 					severity: 1
 				},
 			]
@@ -1252,7 +1423,7 @@ fn test_write_tracked_files_to_temp_single_file() {
 	interop_test_must_write_file(test_file, 'module main')
 
 	mut app := &App{
-		temp_dir: temp_dir
+		temp_dir:   temp_dir
 		open_files: map[string]string{}
 	}
 
@@ -1290,7 +1461,7 @@ fn test_write_tracked_files_to_temp_multiple_files() {
 	}
 
 	mut app := &App{
-		temp_dir: temp_dir
+		temp_dir:   temp_dir
 		open_files: map[string]string{}
 	}
 
@@ -1331,7 +1502,7 @@ fn test_write_tracked_files_to_temp_nested_directories() {
 	interop_test_must_write_file(nested_file, 'module internal')
 
 	mut app := &App{
-		temp_dir: temp_dir
+		temp_dir:   temp_dir
 		open_files: map[string]string{}
 	}
 
@@ -1371,7 +1542,7 @@ fn test_prepare_compilation_overlay_preserves_nested_symlink_layout() {
 	main_uri := path_to_uri(main_file)
 	unsaved_content := 'module main\n\nfn unsaved() {}\n'
 	mut app := &App{
-		temp_dir: app_temp_dir
+		temp_dir:   app_temp_dir
 		open_files: {
 			main_uri: unsaved_content
 		}
@@ -1391,7 +1562,7 @@ fn test_prepare_compilation_overlay_preserves_nested_symlink_layout() {
 	assert overlay.temp_work_dir == os.join_path(overlay.temp_root, 'src')
 	assert overlay.temp_source_file == os.join_path(overlay.temp_root, 'src', 'main.v')
 	assert os.read_file(overlay.temp_source_file) or { '' } == unsaved_content
-	mapped_path := source_path_from_overlay(overlay.temp_source_file, overlay)
+	mapped_path := source_path_from_overlay(overlay.temp_source_file, overlay, '')
 	assert normalize_overlay_path(mapped_path) == normalize_overlay_path(main_file)
 }
 
@@ -1412,7 +1583,7 @@ fn test_prepare_compilation_overlay_preserves_posix_backslashes() {
 		assert uri_to_path(main_uri) == main_file
 		unsaved_content := 'module main\n\nfn unsaved() {}\n'
 		mut app := &App{
-			temp_dir: app_temp_dir
+			temp_dir:   app_temp_dir
 			open_files: {
 				main_uri: unsaved_content
 			}
@@ -1429,7 +1600,7 @@ fn test_prepare_compilation_overlay_preserves_posix_backslashes() {
 		assert overlay.source_root == project_dir
 		assert overlay.source_display_root == project_dir
 		assert os.read_file(overlay.temp_source_file) or { '' } == unsaved_content
-		mapped_path := source_path_from_overlay(overlay.temp_source_file, overlay)
+		mapped_path := source_path_from_overlay(overlay.temp_source_file, overlay, '')
 		assert mapped_path == main_file
 	}
 }
@@ -1450,7 +1621,7 @@ fn test_write_tracked_files_skips_files_outside_working_dir() {
 	interop_test_must_write_file(other_file, 'module other')
 
 	mut app := &App{
-		temp_dir: temp_dir
+		temp_dir:   temp_dir
 		open_files: map[string]string{}
 	}
 
@@ -1911,8 +2082,8 @@ fn test_json_error_negative_values() {
 	// to 0 rather than emitted as negative positions (P1-09).
 	err := JsonError{
 		line_nr: -1
-		col: -1
-		len: -1
+		col:     -1
+		len:     -1
 	}
 	diag := v_error_to_lsp_diagnostic(err)
 	assert diag.severity == 1
@@ -1939,11 +2110,11 @@ fn test_params_struct_complete() {
 		content_changes: [ContentChange{
 			text: 'test'
 		}]
-		position: Position{
+		position:        Position{
 			line: 5
 			char: 10
 		}
-		text_document: TextDocumentIdentifier{
+		text_document:   TextDocumentIdentifier{
 			uri: 'file:///test.v'
 		}
 	}
@@ -1971,7 +2142,7 @@ fn test_signature_help_options_triggers() {
 fn test_text_document_sync_options() {
 	sync := TextDocumentSyncOptions{
 		open_close: true
-		change: 1 // Full sync
+		change:     1 // Full sync
 	}
 	assert sync.open_close == true
 	assert sync.change == 1
@@ -1980,7 +2151,7 @@ fn test_text_document_sync_options() {
 fn test_text_document_sync_incremental() {
 	sync := TextDocumentSyncOptions{
 		open_close: true
-		change: 2 // Incremental sync
+		change:     2 // Incremental sync
 	}
 	assert sync.change == 2
 }
@@ -1994,7 +2165,7 @@ fn test_parameter_information() {
 
 fn test_signature_information_with_params() {
 	sig := SignatureInformation{
-		label: 'fn test(a int, b string, c bool)'
+		label:      'fn test(a int, b string, c bool)'
 		parameters: [
 			ParameterInformation{
 				label: 'a int'
@@ -2013,11 +2184,11 @@ fn test_signature_information_with_params() {
 
 fn test_publish_diagnostics_params() {
 	params := PublishDiagnosticsParams{
-		uri: 'file:///test.v'
+		uri:         'file:///test.v'
 		diagnostics: [
 			LSPDiagnostic{
-				range: LSPRange{}
-				message: 'error'
+				range:    LSPRange{}
+				message:  'error'
 				severity: 1
 			},
 		]
diff --git a/snapshot_test.v b/snapshot_test.v
new file mode 100644
index 00000000..26b24196
--- /dev/null
+++ b/snapshot_test.v
@@ -0,0 +1,176 @@
+module main
+
+import os
+import json2
+
+const snapshot_dir = 'testdata/snapshots'
+
+fn must_mkdir_all(path string) {
+	os.mkdir_all(path) or {
+		assert false, 'Failed to create directory ${path}: ${err}'
+		return
+	}
+}
+
+fn must_write_file(path string, content string) {
+	os.write_file(path, content) or {
+		assert false, 'Failed to write file ${path}: ${err}'
+		return
+	}
+}
+
+fn create_test_app() &App {
+	temp_dir := os.join_path(os.temp_dir(), 'vls_snap_${os.getpid()}')
+	os.mkdir_all(temp_dir) or {
+		assert false, 'Failed to create test temp dir: ${err}'
+		return &App{
+			text: ''
+			open_files: map[string]string{}
+			temp_dir: temp_dir
+		}
+	}
+	return &App{
+		text: ''
+		open_files: map[string]string{}
+		temp_dir: temp_dir
+	}
+}
+
+fn cleanup_test_app(app &App) {
+	os.rmdir_all(app.temp_dir) or {}
+}
+const update_env = 'VLS_UPDATE_SNAPSHOTS'
+
+fn snapshot_path(name string) string {
+	return os.join_path(snapshot_dir, '${name}.json')
+}
+
+fn should_update_snapshots() bool {
+	return os.getenv(update_env) == '1'
+}
+
+fn save_snapshot(name string, content string) ! {
+	os.mkdir_all(snapshot_dir) or { return err }
+	os.write_file(snapshot_path(name), content) or { return err }
+}
+
+fn load_snapshot(name string) !string {
+	return os.read_file(snapshot_path(name)) or { return err }
+}
+
+fn assert_snapshot(name string, actual string) {
+	if should_update_snapshots() {
+		save_snapshot(name, actual) or {}
+		return
+	}
+	expected := load_snapshot(name) or {
+		save_snapshot(name, actual) or {}
+		return
+	}
+	assert actual == expected, 'snapshot mismatch for ${name}:\n--- expected ---\n${expected}\n--- actual ---\n${actual}'
+}
+
+fn response_to_json(resp Response) string {
+	return json2.encode(resp, escape_unicode: true)
+}
+
+fn snapshot_completion(name string, content string, line int, ch int) {
+	mut app := create_test_app()
+	defer { cleanup_test_app(app) }
+
+	tmp_dir := os.join_path(app.temp_dir, 'snap')
+	must_mkdir_all(tmp_dir)
+	file := os.join_path(tmp_dir, 'main.v')
+	must_write_file(file, content)
+
+	uri := path_to_uri(file)
+	app.text = content
+	app.open_files[uri] = content
+
+	req := Request{
+		id: 1
+		method: 'textDocument/completion'
+		params: json2.encode(Params{
+			text_document: TextDocumentIdentifier{ uri: uri }
+			position: Position{ line: line, char: ch }
+		}, escape_unicode: true)
+	}
+
+	resp := app.operation_at_pos(.completion, req)
+	json := response_to_json(resp)
+	assert_snapshot(name, json)
+}
+
+fn snapshot_hover(name string, content string, line int, ch int) {
+	mut app := create_test_app()
+	defer { cleanup_test_app(app) }
+
+	tmp_dir := os.join_path(app.temp_dir, 'snap')
+	must_mkdir_all(tmp_dir)
+	file := os.join_path(tmp_dir, 'main.v')
+	must_write_file(file, content)
+
+	uri := path_to_uri(file)
+	app.text = content
+	app.open_files[uri] = content
+
+	req := Request{
+		id: 1
+		method: 'textDocument/hover'
+		params: json2.encode(Params{
+			text_document: TextDocumentIdentifier{ uri: uri }
+			position: Position{ line: line, char: ch }
+		}, escape_unicode: true)
+	}
+
+	resp := app.operation_at_pos(.hover, req)
+	json := response_to_json(resp)
+	assert_snapshot(name, json)
+}
+
+fn snapshot_definition(name string, content string, line int, ch int) {
+	mut app := create_test_app()
+	defer { cleanup_test_app(app) }
+
+	tmp_dir := os.join_path(app.temp_dir, 'snap')
+	must_mkdir_all(tmp_dir)
+	file := os.join_path(tmp_dir, 'main.v')
+	must_write_file(file, content)
+
+	uri := path_to_uri(file)
+	app.text = content
+	app.open_files[uri] = content
+
+	req := Request{
+		id: 1
+		method: 'textDocument/definition'
+		params: json2.encode(Params{
+			text_document: TextDocumentIdentifier{ uri: uri }
+			position: Position{ line: line, char: ch }
+		}, escape_unicode: true)
+	}
+
+	resp := app.operation_at_pos(.definition, req)
+	json := response_to_json(resp)
+	assert_snapshot(name, json)
+}
+
+fn test_snapshot_completion_basic() {
+	content := 'module main\n\nfn main() {\n\tos.\n}\n'
+	snapshot_completion('completion_basic', content, 3, 4)
+}
+
+fn test_snapshot_hover_basic() {
+	content := 'module main\n\nfn greet(name string) string {\n\treturn name\n}\n\nfn main() {\n\tgreet("world")\n}\n'
+	snapshot_hover('hover_basic', content, 7, 3)
+}
+
+fn test_snapshot_definition_basic() {
+	content := 'module main\n\nfn greet(name string) string {\n\treturn name\n}\n\nfn main() {\n\tgreet("world")\n}\n'
+	snapshot_definition('definition_basic', content, 7, 3)
+}
+
+fn test_snapshot_completion_member() {
+	content := 'module main\n\nstruct User {\n\tname string\n\tage  int\n}\n\nfn main() {\n\tu := User{}\n\tu.\n}\n'
+	snapshot_completion('completion_member', content, 10, 3)
+}