diff --git a/src/font/shaper/coretext.zig b/src/font/shaper/coretext.zig
index 56e172aa3..2ea316637 100644
--- a/src/font/shaper/coretext.zig
+++ b/src/font/shaper/coretext.zig
@@ -232,7 +232,24 @@ pub const Shaper = struct {
         // Get our font. We have to apply the font features we want for
         // the font here.
         const run_font: *macos.text.Font = font: {
-            const face = try run.group.group.faceFromIndex(run.font_index);
+            // The CoreText shaper relies on CoreText and CoreText claims
+            // that CTFonts are threadsafe. See:
+            // https://developer.apple.com/documentation/coretext/
+            //
+            // Quote:
+            // All individual functions in Core Text are thread-safe. Font
+            // objects (CTFont, CTFontDescriptor, and associated objects) can
+            // be used simultaneously by multiple operations, work queues, or
+            // threads. However, the layout objects (CTTypesetter,
+            // CTFramesetter, CTRun, CTLine, CTFrame, and associated objects)
+            // should be used in a single operation, work queue, or thread.
+            //
+            // Because of this, we only acquire the read lock to grab the
+            // face and set it up, then release it.
+            run.grid.lock.lockShared();
+            defer run.grid.lock.unlockShared();
+
+            const face = try run.grid.resolver.collection.getFace(run.font_index);
             const original = face.font;
 
             const attrs = try self.features.attrsDict(face.quirks_disable_default_font_features);
diff --git a/src/font/shaper/run.zig b/src/font/shaper/run.zig
index 2d982411f..36e7ef2ab 100644
--- a/src/font/shaper/run.zig
+++ b/src/font/shaper/run.zig
@@ -174,7 +174,7 @@ pub const RunIterator = struct {
 
                 // Otherwise we need a fallback character. Prefer the
                 // official replacement character.
-                if (try self.group.indexForCodepoint(
+                if (try self.grid.getIndex(
                     alloc,
                     0xFFFD, // replacement char
                     font_style,
@@ -182,7 +182,7 @@ pub const RunIterator = struct {
                 )) |idx| break :font_info .{ .idx = idx, .fallback = 0xFFFD };
 
                 // Fallback to space
-                if (try self.group.indexForCodepoint(
+                if (try self.grid.getIndex(
                     alloc,
                     ' ',
                     font_style,
@@ -251,7 +251,7 @@ pub const RunIterator = struct {
     ) !?font.Collection.Index {
         // Get the font index for the primary codepoint.
         const primary_cp: u32 = if (cell.isEmpty() or cell.codepoint() == 0) ' ' else cell.codepoint();
-        const primary = try self.group.indexForCodepoint(
+        const primary = try self.grid.getIndex(
             alloc,
             primary_cp,
             style,
@@ -275,7 +275,7 @@ pub const RunIterator = struct {
 
             // Find a font that supports this codepoint. If none support this
             // then the whole grapheme can't be rendered so we return null.
-            const idx = try self.group.indexForCodepoint(
+            const idx = try self.grid.getIndex(
                 alloc,
                 cp,
                 style,
@@ -286,11 +286,11 @@ pub const RunIterator = struct {
 
         // We need to find a candidate that has ALL of our codepoints
         for (candidates.items) |idx| {
-            if (!self.group.group.hasCodepoint(idx, primary_cp, presentation)) continue;
+            if (!self.grid.hasCodepoint(idx, primary_cp, presentation)) continue;
             for (cps) |cp| {
                 // Ignore Emoji ZWJs
                 if (cp == 0xFE0E or cp == 0xFE0F or cp == 0x200D) continue;
-                if (!self.group.group.hasCodepoint(idx, cp, presentation)) break;
+                if (!self.grid.hasCodepoint(idx, cp, presentation)) break;
             } else {
                 // If the while completed, then we have a candidate that
                 // supports all of our codepoints.