diff --git a/src/renderer/generic.zig b/src/renderer/generic.zig
index 0f4a294bc..9c7dc602f 100644
--- a/src/renderer/generic.zig
+++ b/src/renderer/generic.zig
@@ -17,6 +17,7 @@ const noMinContrast = cellpkg.noMinContrast;
 const constraintWidth = cellpkg.constraintWidth;
 const isCovering = cellpkg.isCovering;
 const rowNeverExtendBg = @import("row.zig").neverExtendBg;
+const glyph_protocol = @import("glyph_protocol.zig");
 const Overlay = @import("Overlay.zig");
 const imagepkg = @import("image.zig");
 const ImageState = imagepkg.State;
@@ -173,6 +174,9 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
         font_shaper: font.Shaper,
         font_shaper_cache: font.ShaperCache,
 
+        /// Renderer-local snapshot of per-session Glyph Protocol entries.
+        glyph_protocol: glyph_protocol.State = .empty,
+
         /// The images that we may render.
         images: ImageState = .empty,
 
@@ -815,6 +819,7 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
 
             self.font_shaper.deinit();
             self.font_shaper_cache.deinit(self.alloc);
+            self.glyph_protocol.deinit(self.alloc);
 
             self.config.deinit();
 
@@ -1074,6 +1079,11 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
             // Update our grid
             self.font_grid = grid;
 
+            // When our font grid changes, our cell metrics can change,
+            // our atlas is gone, etc. so invalid all prior glyph
+            // protocol rasterizations.
+            self.glyph_protocol.invalidateRasterized();
+
             // Update all our textures so that they sync on the next frame.
             // We can modify this without a lock because the GPU does not
             // touch this data.
@@ -1199,6 +1209,20 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
                     state.terminal.scrollViewport(.bottom);
                 }
 
+                // Sync our Glyph Protocol state before updating the render
+                // state because RenderState.update consumes terminal dirty
+                // flags, including glyph_glossary.
+                if (state.terminal.flags.dirty.glyph_glossary) {
+                    self.glyph_protocol.syncFromGlossary(
+                        self.alloc,
+                        &state.terminal.glyph_glossary,
+                    ) catch |err| {
+                        // Don't hard fail the frame update, just degrade
+                        // to showing some invalid glyphs.
+                        log.warn("error syncing glyph protocol state err={}", .{err});
+                    };
+                }
+
                 // Update our terminal state
                 try self.terminal_state.update(self.alloc, state.terminal);
 
@@ -3173,6 +3197,59 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
             const cell = cell_raws[x];
             const cp = cell.codepoint();
 
+            // If we have a glyph via the glyph protocol, render that.
+            if (self.glyph_protocol.renderGlyph(
+                self.alloc,
+                self.font_grid,
+                self.grid_metrics,
+                cp,
+            ) catch |err| switch (err) {
+                error.OutOfMemory => return error.OutOfMemory,
+                error.RasterizationFailed => glyph: {
+                    // If rasterization fails for any reason, just render the
+                    // replacement char to show some invalid character is
+                    // here.
+                    log.warn("error rasterizing glyph protocol glyph, rendering replacement character cp={X}", .{cp});
+                    const replacement = try self.font_grid.renderCodepoint(
+                        self.alloc,
+                        0xFFFD,
+                        .regular,
+                        .text,
+                        .{
+                            .grid_metrics = self.grid_metrics,
+                            .cell_width = cell.gridWidth(),
+                        },
+                    );
+
+                    break :glyph if (replacement) |render|
+                        render.glyph
+                    else {
+                        // Super weird, we should always have something for
+                        // the replacement char. Log it and just render
+                        // nothing I guess.
+                        log.warn("replacement character couldn't render", .{});
+                        return;
+                    };
+                },
+            }) |glyph| {
+                // If the glyph is 0 width or height, it will be invisible
+                // when drawn, so don't bother adding it to the buffer.
+                if (glyph.width == 0 or glyph.height == 0) return;
+                try self.cells.add(self.alloc, .text, .{
+                    // For now, we only support grayscale glyphs.
+                    .atlas = .grayscale,
+                    .grid_pos = .{ @intCast(x), @intCast(y) },
+                    .color = .{ color.r, color.g, color.b, alpha },
+                    .glyph_pos = .{ glyph.atlas_x, glyph.atlas_y },
+                    .glyph_size = .{ glyph.width, glyph.height },
+                    .bearings = .{
+                        @intCast(glyph.offset_x),
+                        @intCast(glyph.offset_y),
+                    },
+                });
+                return;
+            }
+
             // Render
             const render = try self.font_grid.renderGlyph(
                 self.alloc,
diff --git a/src/renderer/glyph_protocol.zig b/src/renderer/glyph_protocol.zig
new file mode 100644
index 000000000..7b2d55561
--- /dev/null
+++ b/src/renderer/glyph_protocol.zig
@@ -0,0 +1,318 @@
+const std = @import("std");
+const testing = std.testing;
+const Allocator = std.mem.Allocator;
+
+const font = @import("../font/main.zig");
+const glyf_rasterize = font.glyf_rasterize;
+const Glossary = @import("../terminal/main.zig").apc.glyph.Glossary;
+const Glyf = @import("../font/opentype/glyf.zig").Glyf;
+
+/// Map of registered codepoints in renderer-local state.
+pub const CodepointMap = std.AutoArrayHashMapUnmanaged(u21, Codepoint);
+
+/// Renderer-local Glyph Protocol state for one terminal session.
+///
+/// The terminal owns the authoritative `Glossary`, but the renderer cannot
+/// keep pointers into it because rendering happens outside the terminal mutex
+/// and rasterized atlas metadata has renderer-specific lifetime.
+///
+/// This state is a snapshot of the terminal glossary plus lazy rasterization
+/// cache for glyphs that have actually appeared on screen.
+pub const State = struct {
+    /// Registered codepoints keyed by Unicode scalar value.
+    codepoints: CodepointMap = .empty,
+
+    /// Empty initial state with no registrations and no allocated storage.
+    pub const empty: State = .{ .codepoints = .empty };
+
+    /// Release all cloned glossary entries and map storage owned by this state.
+    pub fn deinit(self: *State, alloc: Allocator) void {
+        for (self.codepoints.values()) |*entry| entry.deinit(alloc);
+        self.codepoints.deinit(alloc);
+        self.* = undefined;
+    }
+
+    /// Synchronize the renderer-local state from the terminal glossary.
+    ///
+    /// This does a full replacement rather than attempting to diff because the
+    /// glossary is spec-limited to 1024 entries and full replacement naturally
+    /// invalidates rasterized glyphs for clear, overwrite, and FIFO eviction.
+    /// If cloning fails, the previous renderer state is left intact.
+    pub fn syncFromGlossary(
+        self: *State,
+        alloc: Allocator,
+        glossary: *const Glossary,
+    ) Allocator.Error!void {
+        // Build a complete replacement first. If any clone/allocation fails,
+        // errdefer releases the partial map and `self` continues to point at
+        // the previous successfully-synced snapshot.
+        var new_codepoints: CodepointMap = .empty;
+        errdefer deinitMap(&new_codepoints, alloc);
+
+        try new_codepoints.ensureTotalCapacity(alloc, glossary.entries.count());
+        for (glossary.entries.keys(), glossary.entries.values()) |cp, *entry| {
+            new_codepoints.putAssumeCapacityNoClobber(cp, .{
+                .entry = try entry.clone(alloc),
+            });
+        }
+
+        // Only after the new snapshot is complete do we release the old one.
+        // This makes sync failure non-destructive, which lets the renderer
+        // fall back to the last good snapshot under memory pressure.
+        deinitMap(&self.codepoints, alloc);
+        self.codepoints = new_codepoints;
+    }
+
+    /// Invalidate rasterized atlas metadata while preserving registration
+    /// entries so they can be re-rasterized for a new font grid or cell size.
+    ///
+    /// Call this when the terminal grid metrics change in any way.
+    pub fn invalidateRasterized(self: *State) void {
+        for (self.codepoints.values()) |*entry| entry.rasterized = null;
+    }
+
+    /// Errors that callers of `renderGlyph` can meaningfully react to.
+    pub const RenderError = Allocator.Error || error{
+        /// The decoded glyph could not be rasterized by the renderer.
+        RasterizationFailed,
+    };
+
+    /// Render a registered codepoint into the shared grayscale atlas, lazily.
+    ///
+    /// The returned glyph is atlas metadata only. The underlying registration
+    /// entry is kept so font-grid changes can invalidate and rasterize again.
+    pub fn renderGlyph(
+        self: *State,
+        alloc: Allocator,
+        grid: *font.SharedGrid,
+        grid_metrics: font.Metrics,
+        cp: u21,
+    ) RenderError!?font.Glyph {
+        const codepoint = self.codepoints.getPtr(cp) orelse return null;
+
+        // Fast path: the glyph was already rasterized into the current font
+        // atlas. `font.Glyph` is just atlas metadata, so returning it by value
+        // is cheap and avoids touching the cloned outline again.
+        if (codepoint.rasterized) |glyph| return glyph;
+
+        const entry = &codepoint.entry;
+
+        // Glyph Protocol `width` is the requested cell span. Use it for both
+        // the bitmap width and constraint span so sizing/alignment/padding are
+        // applied over the same 1- or 2-cell render span described by the spec.
+        const width_cells: u2 = switch (entry.width) {
+            .narrow => 1,
+            .wide => 2,
+        };
+
+        // Decode-time validation already guaranteed this is a supported glyf
+        // outline. Rasterization happens lazily because applications may
+        // register many glyphs that never become visible.
+        var bitmap = switch (entry.glyph) {
+            .glyf => |outline| glyf_rasterize.rasterize(
+                alloc,
+                outline,
+                entry.design,
+                .{
+                    .grid_metrics = grid_metrics,
+                    .cell_width = width_cells,
+                    .constraint = entry.constraint,
+                    .constraint_width = width_cells,
+                },
+            ) catch |err| switch (err) {
+                error.OutOfMemory => return error.OutOfMemory,
+
+                error.NoCurrentPoint,
+                error.InvalidMatrix,
+                error.PathNotClosed,
+                error.InvalidHeight,
+                error.InvalidWidth,
+                error.InvalidState,
+                => return error.RasterizationFailed,
+            },
+        };
+        defer bitmap.deinit(alloc);
+
+        // Cache the empty result too. This prevents repeated rasterization for
+        // valid but visually-empty outlines while keeping downstream render code
+        // on the normal zero-sized-glyph skip path.
+        if (bitmap.width == 0 or bitmap.height == 0) {
+            codepoint.rasterized = .{
+                .width = 0,
+                .height = 0,
+                .offset_x = 0,
+                .offset_y = 0,
+                .atlas_x = 0,
+                .atlas_y = 0,
+            };
+            return codepoint.rasterized.?;
+        }
+
+        // Atlas allocation and writes must hold the shared grid lock. The more
+        // expensive vector rasterization above intentionally happens outside the
+        // lock so other surfaces sharing this grid are blocked for less time.
+        grid.lock.lock();
+        defer grid.lock.unlock();
+
+        // Reuse the normal font grayscale atlas. If it fills up, grow it and
+        // retry just like SharedGrid.renderGlyph does for regular font glyphs.
+        const region = region: while (true) {
+            break :region grid.atlas_grayscale.reserve(
+                alloc,
+                bitmap.width,
+                bitmap.height,
+            ) catch |err| switch (err) {
+                error.OutOfMemory => return error.OutOfMemory,
+                error.AtlasFull => {
+                    try grid.atlas_grayscale.grow(alloc, grid.atlas_grayscale.size * 2);
+                    continue;
+                },
+            };
+        };
+        grid.atlas_grayscale.set(region, bitmap.data);
+
+        // A Glyph Protocol glyf bitmap is rasterized as a full render-span
+        // bitmap. A top bearing equal to bitmap height places the top of the
+        // quad at the top of the cell in the existing text shader convention.
+        codepoint.rasterized = .{
+            .width = bitmap.width,
+            .height = bitmap.height,
+            .offset_x = 0,
+            .offset_y = @intCast(bitmap.height),
+            .atlas_x = region.x,
+            .atlas_y = region.y,
+        };
+
+        return codepoint.rasterized.?;
+    }
+
+    /// Release a codepoint map and all cloned entries in it.
+    ///
+    /// This helper resets the map to `.empty` so it can be safely reused after
+    /// both successful replacement and error-path cleanup.
+    fn deinitMap(map: *CodepointMap, alloc: Allocator) void {
+        for (map.values()) |*entry| entry.deinit(alloc);
+        map.deinit(alloc);
+        map.* = .empty;
+    }
+};
+
+/// One registered codepoint in the renderer snapshot.
+pub const Codepoint = struct {
+    /// Cloned terminal glossary entry. This is kept even after rasterization so
+    /// font grid changes can discard atlas metadata and rasterize again.
+    entry: Glossary.Entry,
+
+    /// Cached atlas metadata for the current font grid, if visible before.
+    rasterized: ?font.Glyph = null,
+
+    /// Release the cloned glossary entry owned by this codepoint.
+    pub fn deinit(self: *Codepoint, alloc: Allocator) void {
+        self.entry.deinit(alloc);
+        self.* = undefined;
+    }
+};
+
+fn testEntry(alloc: Allocator, x_offset: i32) !Glossary.Entry {
+    const contours = try alloc.dupe(u16, &.{2});
+    errdefer alloc.free(contours);
+
+    const points = try alloc.dupe(Glyf.Outline.Point, &.{
+        .{ .x = x_offset, .y = 0, .on_curve = true },
+        .{ .x = x_offset + 500, .y = 0, .on_curve = true },
+        .{ .x = x_offset, .y = 500, .on_curve = true },
+    });
+    errdefer alloc.free(points);
+
+    return .{
+        .glyph = .{ .glyf = .{
+            .contours = contours,
+            .points = points,
+        } },
+        .design = .{
+            .units_per_em = 1000,
+            .advance_width = 1000,
+            .line_height = 1000,
+        },
+        .width = .narrow,
+        .constraint = .none,
+    };
+}
+
+test "State syncFromGlossary clones terminal entries" {
+    const alloc = testing.allocator;
+
+    var glossary: Glossary = .empty;
+    defer glossary.deinit(alloc);
+    try glossary.register(alloc, 0xE000, try testEntry(alloc, 0));
+
+    var state: State = .empty;
+    defer state.deinit(alloc);
+    try state.syncFromGlossary(alloc, &glossary);
+
+    try testing.expect(state.codepoints.contains(0xE000));
+    try testing.expect(!state.codepoints.contains(0xE001));
+
+    const src = glossary.entries.getPtr(0xE000).?;
+    const dst = state.codepoints.getPtr(0xE000).?;
+    try testing.expect(src.glyph.glyf.points.ptr != dst.entry.glyph.glyf.points.ptr);
+    try testing.expectEqual(src.glyph.glyf.points[0], dst.entry.glyph.glyf.points[0]);
+}
+
+test "State syncFromGlossary replaces removed and changed entries" {
+    const alloc = testing.allocator;
+
+    var glossary: Glossary = .empty;
+    defer glossary.deinit(alloc);
+    try glossary.register(alloc, 0xE000, try testEntry(alloc, 0));
+
+    var state: State = .empty;
+    defer state.deinit(alloc);
+    try state.syncFromGlossary(alloc, &glossary);
+
+    try glossary.register(alloc, 0xE001, try testEntry(alloc, 10));
+    try glossary.delete(alloc, 0xE000);
+    try state.syncFromGlossary(alloc, &glossary);
+
+    try testing.expect(!state.codepoints.contains(0xE000));
+    try testing.expect(state.codepoints.contains(0xE001));
+    try testing.expectEqual(@as(i32, 10), state.codepoints.getPtr(0xE001).?.entry.glyph.glyf.points[0].x);
+}
+
+test "State invalidateRasterized clears cached glyph metadata" {
+    const alloc = testing.allocator;
+
+    var glossary: Glossary = .empty;
+    defer glossary.deinit(alloc);
+    try glossary.register(alloc, 0xE000, try testEntry(alloc, 0));
+
+    var state: State = .empty;
+    defer state.deinit(alloc);
+    try state.syncFromGlossary(alloc, &glossary);
+
+    const codepoint = state.codepoints.getPtr(0xE000).?;
+    codepoint.rasterized = .{
+        .width = 1,
+        .height = 1,
+        .offset_x = 0,
+        .offset_y = 1,
+        .atlas_x = 2,
+        .atlas_y = 3,
+    };
+
+    state.invalidateRasterized();
+    try testing.expect(codepoint.rasterized == null);
+}
+
+test "State renderGlyph returns null for unregistered codepoint" {
+    var state: State = .empty;
+
+    const grid: *font.SharedGrid = undefined;
+    const glyph = try state.renderGlyph(
+        testing.allocator,
+        grid,
+        undefined,
+        0xE000,
+    );
+    try testing.expect(glyph == null);
+}
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 3a914794f..9350c5549 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -3208,6 +3208,11 @@ pub fn fullReset(self: *Terminal) void {
 
     // Always mark dirty so we redraw everything
     self.flags.dirty.clear = true;
+
+    // The clear dirty bit is enough to force a full render-state rebuild, but
+    // renderers keep their own cloned Glyph Protocol state. Set the glossary
+    // dirty bit too so they sync and drop any registrations cleared above.
+    self.flags.dirty.glyph_glossary = true;
 }
 
 /// Returns true if the point is dirty, used for testing.