From 72f2edfa713114a8b122defdef802595ec031fd8 Mon Sep 17 00:00:00 2001
From: HarshaNaidu11 <harshavardhannaidu1111@gmail.com>
Date: Fri, 3 Jul 2026 23:20:46 +0530
Subject: [PATCH 1/2] fix(core): adjust wide-character rendering boundaries in
 differential renderer

---
 packages/core/src/terminal/Renderer.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/terminal/Renderer.ts b/packages/core/src/terminal/Renderer.ts
index 41404e21..8dde62bf 100644
--- a/packages/core/src/terminal/Renderer.ts
+++ b/packages/core/src/terminal/Renderer.ts
@@ -278,7 +278,7 @@ export class Renderer {
                 // flush the span
                 const adjustedStart = Renderer._adjustSpanStart(spanStart, back[row]);
                 output += moveTo(adjustedStart, row);
-                for (let sc = spanStart; sc < c; sc++) {
+                for (let sc = adjustedStart; sc < c; sc++) {
                     const cell = back[row][sc];
                     if (cell.width === 0) continue;
                     output += this._renderCell(cell);
@@ -291,7 +291,7 @@ export class Renderer {
         if (spanStart !== -1) {
             const adjustedStart = Renderer._adjustSpanStart(spanStart, back[row]);
             output += moveTo(adjustedStart, row);
-            for (let sc = spanStart; sc < cols; sc++) {
+            for (let sc = adjustedStart; sc < cols; sc++) {
                 const cell = back[row][sc];
                 if (cell.width === 0) continue;
                 output += this._renderCell(cell);

From 8e843412a459f5a292719f2250919123461c5021 Mon Sep 17 00:00:00 2001
From: HarshaNaidu11 <harshavardhannaidu1111@gmail.com>
Date: Sun, 5 Jul 2026 12:03:27 +0530
Subject: [PATCH 2/2] fix(core): resolve wide-character layout corruption in
 differential renderer

---
 packages/core/src/terminal/Renderer.test.ts | 28 +++++++++++++++++++++
 packages/core/src/terminal/Renderer.ts      |  7 +++---
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/packages/core/src/terminal/Renderer.test.ts b/packages/core/src/terminal/Renderer.test.ts
index 4f9fb1c0..3ab64f7f 100644
--- a/packages/core/src/terminal/Renderer.test.ts
+++ b/packages/core/src/terminal/Renderer.test.ts
@@ -262,4 +262,32 @@ describe('Renderer profiling hooks', () => {
         const resetCount = (output.match(/\x1b\[0m/g) || []).length;
         expect(resetCount).toBeGreaterThanOrEqual(2);
     });
+
+    it('correctly adjusts span start backwards and renders from adjustedStart', () => {
+        const narrowScreen = new Screen(10, 2);
+        const renderer = new Renderer(terminal, narrowScreen);
+
+        // First frame: write a wide character at col 0 and 'A' at col 2
+        narrowScreen.setCell(0, 0, { char: '中', width: 2 });
+        narrowScreen.setCell(1, 0, { char: '', width: 0 });
+        narrowScreen.setCell(2, 0, { char: 'A', width: 1 });
+        renderer.renderNow();
+
+        // Second frame: Keep col 0 unchanged, change col 1 style (continuation) and col 2 char
+        narrowScreen.setCell(0, 0, { char: '中', width: 2 });
+        narrowScreen.setCell(1, 0, { char: '', width: 0, fg: { type: 'named', name: 'red' } });
+        narrowScreen.setCell(2, 0, { char: 'B', width: 1 });
+
+        fakeStdout.writes = '';
+        renderer.renderNow();
+
+        // Verify that the output has redrawn the wide character at col 0
+        const outputStr = fakeStdout.writes;
+        // It should move to col 0, not col 1 or 2, to start rendering
+        expect(outputStr).toContain('\x1b[1;1H');
+        // It should render '中'
+        expect(outputStr).toContain('中');
+        // It should render 'B'
+        expect(outputStr).toContain('B');
+    });
 });
diff --git a/packages/core/src/terminal/Renderer.ts b/packages/core/src/terminal/Renderer.ts
index 8dde62bf..3368e743 100644
--- a/packages/core/src/terminal/Renderer.ts
+++ b/packages/core/src/terminal/Renderer.ts
@@ -267,11 +267,10 @@ export class Renderer {
         let spanStart = -1;
 
         for (let c = 0; c < cols; c++) {
-            // Skip continuation cells (right half of wide chars) - they are not
-            // independently renderable and their primary cell handles the output.
-            if (back[row][c].width === 0) continue;
-            
             const changed = !cellsEqual(front[row][c], back[row][c]);
+            // Skip continuation cells (right half of wide chars) if they haven't changed.
+            // If they have changed, we must process them so we can adjust the span start back to the primary cell.
+            if (back[row][c].width === 0 && !changed) continue;
             if (changed && spanStart === -1) {
                 spanStart = c; // start a new changed span
             } else if (!changed && spanStart !== -1) {