diff --git a/CHANGELOG.md b/CHANGELOG.md
index acf8f8a7..a0db8c24 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
-- Sync to upstream Luau 0.597
+- Sync to upstream Luau 0.599
 - Prioritise `game:GetService()` as the first autocompletion entry when typing `game:`
 - Code blocks in hover and documentation now use `luau` as the syntax highlighting
 
diff --git a/luau b/luau
index 1d0b4491..24fdac4c 160000
--- a/luau
+++ b/luau
@@ -1 +1 @@
-Subproject commit 1d0b449181a41c00efc255a9a255616b843986b9
+Subproject commit 24fdac4c05f5ae189ede5153a83af4c1bd25351d
diff --git a/src/operations/Completion.cpp b/src/operations/Completion.cpp
index 8c776b84..3ac649d6 100644
--- a/src/operations/Completion.cpp
+++ b/src/operations/Completion.cpp
@@ -7,6 +7,9 @@
 #include "LSP/LuauExt.hpp"
 #include "LSP/DocumentationParser.hpp"
 
+LUAU_FASTFLAG(LuauClipExtraHasEndProps);
+LUAU_FASTFLAG(LuauAutocompleteDoEnd);
+
 /// Defining sort text levels assigned to completion items
 /// Note that sort text is lexicographically
 namespace SortText
@@ -100,24 +103,66 @@ void WorkspaceFolder::endAutocompletion(const lsp::CompletionParams& params)
         return;
 
     auto unclosedBlock = false;
-    for (auto it = ancestry.rbegin(); it != ancestry.rend(); ++it)
+    if (FFlag::LuauClipExtraHasEndProps)
     {
-        if (auto* statForIn = (*it)->as<Luau::AstStatForIn>(); statForIn && !statForIn->hasEnd)
-            unclosedBlock = true;
-        if (auto* statFor = (*it)->as<Luau::AstStatFor>(); statFor && !statFor->hasEnd)
-            unclosedBlock = true;
-        if (auto* statIf = (*it)->as<Luau::AstStatIf>(); statIf && !statIf->hasEnd)
-            unclosedBlock = true;
-        if (auto* statWhile = (*it)->as<Luau::AstStatWhile>(); statWhile && !statWhile->hasEnd)
-            unclosedBlock = true;
-        if (auto* statBlock = (*it)->as<Luau::AstStatBlock>(); statBlock && !statBlock->hasEnd)
-            unclosedBlock = true;
-        if (auto* exprFunction = (*it)->as<Luau::AstExprFunction>(); exprFunction && !exprFunction->hasEnd)
-            unclosedBlock = true;
+        for (auto it = ancestry.rbegin(); it != ancestry.rend(); ++it)
+        {
+            if (auto* statForIn = (*it)->as<Luau::AstStatForIn>(); statForIn && !statForIn->body->hasEnd)
+                unclosedBlock = true;
+            else if (auto* statFor = (*it)->as<Luau::AstStatFor>(); statFor && !statFor->body->hasEnd)
+                unclosedBlock = true;
+            else if (auto* statIf = (*it)->as<Luau::AstStatIf>())
+            {
+                bool hasEnd = statIf->thenbody->hasEnd;
+                if (statIf->elsebody)
+                {
+                    if (auto* elseBlock = statIf->elsebody->as<Luau::AstStatBlock>())
+                        hasEnd = elseBlock->hasEnd;
+                }
+
+                if (!hasEnd)
+                    unclosedBlock = true;
+            }
+            else if (auto* statWhile = (*it)->as<Luau::AstStatWhile>(); statWhile && !statWhile->body->hasEnd)
+                unclosedBlock = true;
+            else if (auto* exprFunction = (*it)->as<Luau::AstExprFunction>(); exprFunction && !exprFunction->body->hasEnd)
+                unclosedBlock = true;
+            if (FFlag::LuauAutocompleteDoEnd)
+            {
+                if (auto* exprBlock = (*it)->as<Luau::AstStatBlock>(); exprBlock && !exprBlock->hasEnd)
+                    unclosedBlock = true;
+
+                // FIX: if the unclosedBlock came from a repeat, then don't autocomplete, as it will be wrong!
+                if (auto* statRepeat = (*it)->as<Luau::AstStatRepeat>(); statRepeat && !statRepeat->body->hasEnd)
+                    unclosedBlock = false;
+            }
+        }
+    }
+    else
+    {
+        for (auto it = ancestry.rbegin(); it != ancestry.rend(); ++it)
+        {
+            if (auto* statForIn = (*it)->as<Luau::AstStatForIn>(); statForIn && !statForIn->DEPRECATED_hasEnd)
+                unclosedBlock = true;
+            if (auto* statFor = (*it)->as<Luau::AstStatFor>(); statFor && !statFor->DEPRECATED_hasEnd)
+                unclosedBlock = true;
+            if (auto* statIf = (*it)->as<Luau::AstStatIf>(); statIf && !statIf->DEPRECATED_hasEnd)
+                unclosedBlock = true;
+            if (auto* statWhile = (*it)->as<Luau::AstStatWhile>(); statWhile && !statWhile->DEPRECATED_hasEnd)
+                unclosedBlock = true;
+            if (FFlag::LuauAutocompleteDoEnd)
+            {
+                if (auto* statBlock = (*it)->as<Luau::AstStatBlock>(); statBlock && !statBlock->hasEnd)
+                    unclosedBlock = true;
+            }
+            if (auto* exprFunction = (*it)->as<Luau::AstExprFunction>(); exprFunction && !exprFunction->DEPRECATED_hasEnd)
+                unclosedBlock = true;
+        }
     }
 
     // TODO: we could potentially extend this further that just `hasEnd`
     // by inserting `then`, `until` `do` etc. It seems Studio does this
+    // NOTE: `until` can be inserted if `hasEnd` in a repeat block is false
 
     if (unclosedBlock)
     {