Clamp fitted terminal sizes to PTY limits

src/renderer/components/terminal/XTermSurface.test.tsx

@@ -1,18 +1,20 @@
 import { act } from "@testing-library/react";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { renderWithI18n as render } from "@/renderer/testUtils/i18n";
+import { resizeTerminalPayloadSchema } from "@/shared/contracts";
 import type { SupervisorEvent } from "@/shared/ipc";
 // ── Hoisted state shared between mock factories and test code ────
 const { state } = vi.hoisted(() => ({
   state: {
     terminal: null as null | Record<string, ReturnType<typeof vi.fn>>,
     terminalOptions: null as null | Record<string, unknown>,
+    fitSize: null as null | { cols: number; rows: number },
     eventListeners: [] as Array<(e: SupervisorEvent) => void>,
     isMac: false,
     bridge: {
       readTerminalScrollback: vi.fn<() => Promise<string>>().mockResolvedValue(""),
       writeTerminal: vi.fn<() => Promise<void>>().mockResolvedValue(undefined),
-      resizeTerminal: vi.fn<() => Promise<void>>().mockResolvedValue(undefined),
+      resizeTerminal: vi.fn<(input: unknown) => Promise<void>>().mockResolvedValue(undefined),
       openExternal: vi.fn<() => Promise<void>>().mockResolvedValue(undefined),
       openExternalNative: vi.fn<() => Promise<void>>().mockResolvedValue(undefined),
       onSupervisorEvent: vi.fn<(listener: (e: SupervisorEvent) => void) => () => void>(),
@@ -70,7 +72,11 @@ vi.mock("@xterm/xterm", () => ({
 
 vi.mock("@xterm/addon-fit", () => ({
   FitAddon: class MockFitAddon {
-    fit = vi.fn<() => void>();
+    fit = vi.fn<() => void>(() => {
+      if (state.terminal && state.fitSize) {
+        Object.assign(state.terminal, state.fitSize);
+      }
+    });
   },
 }));
 
@@ -174,6 +180,7 @@ describe("XTermSurface", () => {
   beforeEach(() => {
     state.terminal = null;
     state.terminalOptions = null;
+    state.fitSize = null;
     state.eventListeners = [];
     state.isMac = false;
     vi.clearAllMocks();
@@ -187,6 +194,7 @@ describe("XTermSurface", () => {
   });
 
   afterEach(() => {
+    vi.restoreAllMocks();
     state.eventListeners = [];
   });
 
@@ -267,6 +275,26 @@ describe("XTermSurface", () => {
     });
   });
 
+  it("clamps a fitted terminal to the backing PTY size contract", async () => {
+    state.fitSize = { cols: 401, rows: 201 };
+    vi.spyOn(HTMLElement.prototype, "clientWidth", "get").mockReturnValue(4_000);
+    vi.spyOn(HTMLElement.prototype, "clientHeight", "get").mockReturnValue(2_000);
+    state.bridge.resizeTerminal.mockImplementation((input) => {
+      resizeTerminalPayloadSchema.parse(input);
+      return Promise.resolve();
+    });
+
+    render(<XTermSurface terminalId="test-1" />);
+    await flushFrame();
+
+    expect(state.terminal).toMatchObject({ cols: 401, rows: 201 });
+    expect(state.bridge.resizeTerminal).toHaveBeenCalledWith({
+      threadId: "test-1",
+      cols: 400,
+      rows: 200,
+    });
+  });
+
   it("does not nudge on a fresh launch with no scrollback", async () => {
     state.bridge.readTerminalScrollback.mockResolvedValueOnce("");
 

src/renderer/components/terminal/XTermSurface.tsx

@@ -21,7 +21,7 @@ import {
   type PointerEvent as ReactPointerEvent,
   type RefObject,
 } from "react";
-import type { TerminalSize } from "@/shared/contracts";
+import { MAX_TERMINAL_COLS, MAX_TERMINAL_ROWS, type TerminalSize } from "@/shared/contracts";
 import { useSharedSettings } from "@/renderer/state/sharedSettingsStore";
 import { useThreadOutputStore } from "@/renderer/state/threadOutputStore";
 import { isMac, readBridge } from "@/renderer/bridge";
@@ -281,6 +281,10 @@ export const XTermSurface = forwardRef<
       resizeBackingTerminalRef.current
         ? resizeBackingTerminalRef.current(size)
         : readBridge().resizeTerminal({ threadId: terminalId, cols: size.cols, rows: size.rows });
+    const backingTerminalSize = (): TerminalSize => ({
+      cols: Math.min(terminal.cols, MAX_TERMINAL_COLS),
+      rows: Math.min(terminal.rows, MAX_TERMINAL_ROWS),
+    });
 
     // Force the live agent to repaint a clean full frame. On reopen the PTY kept
     // running at the same winsize, so a fresh same-size fit issues a no-op
@@ -292,8 +296,7 @@ export const XTermSurface = forwardRef<
     // (possibly stale / byte-sliced) replayed scrollback.
     const forceAgentRepaint = () => {
       if (!isActive) return;
-      const cols = terminal.cols;
-      const rows = terminal.rows;
+      const { cols, rows } = backingTerminalSize();
       if (cols < 20 || rows < 5) return;
       // Pin our throttle bookkeeping to the REAL size so the next doFit doesn't
       // also fire a (now-redundant) resize for the same dimensions.
@@ -430,8 +433,7 @@ export const XTermSurface = forwardRef<
     const flushPtyResize = () => {
       ptyResizeTimer = 0;
       if (!isActive) return;
-      const cols = terminal.cols;
-      const rows = terminal.rows;
+      const { cols, rows } = backingTerminalSize();
       if (cols === lastCols && rows === lastRows) return;
       if (cols < 20 || rows < 5) return;
 
@@ -508,7 +510,7 @@ export const XTermSurface = forwardRef<
         ptyResizeTimer = 0;
       }
       if (!resizeTerminalOnFit) {
-        onTerminalResizeRef.current?.({ cols: terminal.cols, rows: terminal.rows });
+        onTerminalResizeRef.current?.(backingTerminalSize());
       } else if (terminal.buffer.normal.length < RESIZE_DEBOUNCE_BUFFER_THRESHOLD) {
         flushPtyResize();
       } else {

src/shared/contracts/thread.ts

@@ -90,9 +90,12 @@ export interface TerminalShellSnapshot {
   outputLength: number;
 }
 
+export const MAX_TERMINAL_COLS = 400;
+export const MAX_TERMINAL_ROWS = 200;
+
 export const terminalSizeSchema = z.object({
-  cols: z.number().int().min(20).max(400),
-  rows: z.number().int().min(5).max(200),
+  cols: z.number().int().min(20).max(MAX_TERMINAL_COLS),
+  rows: z.number().int().min(5).max(MAX_TERMINAL_ROWS),
 });
 export type TerminalSize = z.infer<typeof terminalSizeSchema>;