diff --git a/src/solanaceae/crdtnotes/crdtnotes.cpp b/src/solanaceae/crdtnotes/crdtnotes.cpp
index ab6fcd5..0043367 100644
--- a/src/solanaceae/crdtnotes/crdtnotes.cpp
+++ b/src/solanaceae/crdtnotes/crdtnotes.cpp
@@ -37,3 +37,20 @@ CRDTNotes::Doc* CRDTNotes::addDoc(const CRDTAgent& self_agent, const DocID& id)
 	return &doc;
 }
 
+void CRDTNotes::writeLockRelease(const DocID& id) {
+	assert(_doc_write_locks.count(id) > 0);
+	_doc_write_locks.erase(id);
+}
+
+bool CRDTNotes::isWriteLocked(const DocID& id) const {
+	return _doc_write_locks.count(id);
+}
+
+std::optional<CRDTNotes::DocWriteLock> CRDTNotes::writeLockAquire(const DocID& id) {
+	if (_doc_write_locks.count(id)) {
+		return std::nullopt; // replace with exception instead?
+	}
+
+	_doc_write_locks.emplace(id);
+	return DocWriteLock{*this, id};
+}
diff --git a/src/solanaceae/crdtnotes/crdtnotes.hpp b/src/solanaceae/crdtnotes/crdtnotes.hpp
index 20ee2d4..26b0bb9 100644
--- a/src/solanaceae/crdtnotes/crdtnotes.hpp
+++ b/src/solanaceae/crdtnotes/crdtnotes.hpp
@@ -6,6 +6,8 @@
 #include <cstdint>
 #include <functional>
 #include <unordered_map>
+#include <unordered_set>
+#include <optional>
 
 using ID32 = std::array<uint8_t, 32>;
 
@@ -37,9 +39,23 @@ class CRDTNotes {
 			uint64_t seq{0};
 		};
 
+		// RAII lock wrapper
+		struct DocWriteLock {
+			CRDTNotes* notes;
+			DocID id;
+
+			// ctr assumes lock
+			DocWriteLock(CRDTNotes& notes, const DocID& id) : notes(&notes), id(id) {}
+			DocWriteLock(const DocWriteLock&) = delete;
+			DocWriteLock(DocWriteLock&& other) : notes(other.notes), id(other.id) { other.notes = nullptr; }
+			~DocWriteLock(void) { if (notes) { notes->writeLockRelease(id); } }
+			bool operator==(const DocWriteLock& other) const { return id == other.id; }
+		};
+
 	private:
 		// TODO: add metadata to docs
 		std::unordered_map<DocID, Doc> _docs;
+		std::unordered_set<DocID> _doc_write_locks;
 
 	public:
 		// config?
@@ -52,5 +68,16 @@ class CRDTNotes {
 		Doc* getDoc(const DocID& id);
 
 		Doc* addDoc(const CRDTAgent& self_agent, const DocID& doc);
+
+		void writeLockRelease(const DocID& id);
+		bool isWriteLocked(const DocID& id) const;
+		std::optional<DocWriteLock> writeLockAquire(const DocID& id);
+};
+
+template<>
+struct std::hash<CRDTNotes::DocWriteLock> {
+	std::uint64_t operator()(const CRDTNotes::DocWriteLock& s) const noexcept {
+		return std::hash<ID32>{}(s.id);
+	}
 };
 
diff --git a/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.cpp b/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.cpp
index aea12c6..cd2d1fc 100644
--- a/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.cpp
+++ b/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.cpp
@@ -48,6 +48,12 @@ namespace detail {
 } // detail
 
 
+std::unordered_set<CRDTNotes::DocWriteLock>::iterator CRDTNotesImGui::findLock(const CRDTNotes::DocID& doc_id) {
+	auto it = _held_locks.begin();
+	for (; it != _held_locks.end() && it->id != doc_id; it++) {}
+	return it;
+}
+
 CRDTNotesImGui::CRDTNotesImGui(CRDTNotes& notes, CRDTNotesSync& notes_sync, ContactStore4I& cs) : _notes(notes), _notes_sync(notes_sync), _cs(cs) {
 }
 
@@ -142,17 +148,36 @@ bool CRDTNotesImGui::renderDoc(const CRDTNotes::DocID& doc_id) {
 		return false;
 	}
 
+	auto lock_it = findLock(doc_id);
+	bool self_held = lock_it != _held_locks.end();
+	const bool foreign_held = !self_held && _notes.isWriteLocked(doc_id);
+
 	auto text = doc->getText();
-	if (renderDocText(text)) {
+	ImGui::InputTextMultiline(
+		"##doc",
+		&text,
+		{-1,-1},
+			ImGuiInputTextFlags_AllowTabInput |
+			(foreign_held ? ImGuiInputTextFlags_ReadOnly : ImGuiInputTextFlags_None) |
+			ImGuiInputTextFlags_CallbackAlways
+		//cb,
+		//&text
+	);
+	if (!foreign_held && !self_held && (ImGui::IsItemActive() || ImGui::IsItemEdited())) {
+		// TODO: check
+		_held_locks.emplace(_notes.writeLockAquire(doc_id).value());
+		self_held = true;
+		std::cout << "!!!! imgui lock aquired\n";
+	} else if (!foreign_held && self_held && !(ImGui::IsItemActive() || ImGui::IsItemEdited())) {
+		// release lock
+		_held_locks.erase(lock_it);
+		std::cout << "!!!! imgui lock released\n";
+	}
+
+	if (self_held && ImGui::IsItemEdited()) {
 		_notes_sync.merge(doc_id, text);
 		return true;
 	}
 
 	return false;
 }
-
-bool CRDTNotesImGui::renderDocText(std::string& text) const {
-	// TODO: replace with text editor (zep) or visualize stuff??
-	return ImGui::InputTextMultiline("##doc", &text, {-1,-1}, ImGuiInputTextFlags_AllowTabInput);
-}
-
diff --git a/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.hpp b/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.hpp
index b0fb52a..017ef89 100644
--- a/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.hpp
+++ b/src/solanaceae/crdtnotes_imgui/crdtnotes_imgui.hpp
@@ -4,6 +4,7 @@
 #include <solanaceae/contact/fwd.hpp>
 
 #include <set>
+#include <unordered_set>
 
 class CRDTNotesImGui {
 	CRDTNotes& _notes;
@@ -13,6 +14,9 @@ class CRDTNotesImGui {
 	bool _show_global_list {true};
 
 	std::set<CRDTNotes::DocID> _open_docs;
+	std::unordered_set<CRDTNotes::DocWriteLock> _held_locks;
+
+	std::unordered_set<CRDTNotes::DocWriteLock>::iterator findLock(const CRDTNotes::DocID& doc_id);
 
 	public:
 		CRDTNotesImGui(CRDTNotes& notes, CRDTNotesSync& notes_sync, ContactStore4I& cs);
@@ -22,6 +26,5 @@ class CRDTNotesImGui {
 		bool renderContactListContactSmall(const Contact4 c, const bool selected) const;
 
 		bool renderDoc(const CRDTNotes::DocID& doc_id);
-		bool renderDocText(std::string& text) const;
 };