merge fix/terminal-fit-remount-stability dans develop (fix: détection de stabilité réelle du fit terminal au remount)

QA: verdict VERT (suite automatisée), réserve manuelle : vérification desktop/Tauri (comportement réel du fit terminal dans l'app packagée) non exécutée.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/features/terminals/TerminalView.test.tsx

@@ -455,10 +455,11 @@ describe("TerminalView — visible launch-failure surface (ticket #14 F3)", () =
       fitSpy.mockRestore();
     });
 
-    it("keeps fitting across a keyed project remount until the new cell settles", async () => {
+    it("keeps fitting across a keyed project remount until the new cell is actually stable", async () => {
       // ProjectsView keys LayoutGrid by project. A project switch therefore
-      // unmounts/remounts TerminalView, so the mount path itself must keep a
+      // unmounts/remounts TerminalView, so the mount path itself must fit until
-      // short tail of fits alive while the new cell geometry settles.
+      // the new cell's real geometry has stabilized, not for a guessed count of
+      // frames.
       const fitSpy = vi.spyOn(FitAddon.prototype, "fit");
       const firstHandle = makeHandle({ sessionId: "project-1" });
       const secondHandle = makeHandle({ sessionId: "project-2" });
@@ -489,11 +490,11 @@ describe("TerminalView — visible launch-failure surface (ticket #14 F3)", () =
       await waitFor(() => expect(open).toHaveBeenCalledTimes(2));
       setTerminalBoxSize(520, 260);
 
-      for (let i = 0; i < 8; i += 1) {
+      for (let i = 0; i < 3; i += 1) {
         await new Promise((resolve) => requestAnimationFrame(resolve));
       }
 
-      expect(fitSpy.mock.calls.length).toBeGreaterThan(5);
+      expect(fitSpy.mock.calls.length).toBeGreaterThanOrEqual(2);
       await waitFor(() => expect(secondHandle.resize).toHaveBeenCalled());
       expect(firstHandle.close).not.toHaveBeenCalled();
       expect(secondHandle.close).not.toHaveBeenCalled();
@@ -501,6 +502,70 @@ describe("TerminalView — visible launch-failure surface (ticket #14 F3)", () =
       fitSpy.mockRestore();
     });
 
+    it("refits a late remount after scrollback while the cell was absent", async () => {
+      // Regression for project/layout switch: the agent can keep writing while
+      // its view is unmounted. On reattach, scrollback is repainted immediately,
+      // but the new container may stay 0x0 longer than the old fixed remount
+      // frame tail. The view must keep retrying until a real size appears.
+      const fitSpy = vi.spyOn(FitAddon.prototype, "fit");
+      const handle = makeHandle({ sessionId: "late-remount-1" });
+      const reattach = vi.fn(
+        async (_sessionId: string, onData: (b: Uint8Array) => void) => {
+          onData(new TextEncoder().encode("agent wrote while absent\r\n"));
+          return {
+            handle,
+            scrollback: new TextEncoder().encode("retained scrollback\r\n"),
+          } satisfies ReattachResult;
+        },
+      );
+      const open = vi.fn(async () => makeHandle({ sessionId: "should-not-open" }));
+
+      renderView(new MockTerminalGateway(), "/cwd", {
+        sessionId: "late-remount-1",
+        open,
+        reattach,
+      });
+
+      await waitFor(() => expect(reattach).toHaveBeenCalledTimes(1));
+      expect(open).not.toHaveBeenCalled();
+      fitSpy.mockClear();
+
+      // Stay zero-sized past the previous fixed remount tail.
+      for (let i = 0; i < 16; i += 1) {
+        await new Promise((resolve) => requestAnimationFrame(resolve));
+      }
+      expect(fitSpy).not.toHaveBeenCalled();
+      expect(handle.resize).not.toHaveBeenCalled();
+
+      setTerminalBoxSize(560, 280);
+
+      await waitFor(() => expect(fitSpy).toHaveBeenCalled());
+      await waitFor(() => expect(handle.resize).toHaveBeenCalled());
+      expect(handle.close).not.toHaveBeenCalled();
+
+      fitSpy.mockRestore();
+    });
+
+    it("continues refitting while remount geometry keeps changing, then stops after stability", async () => {
+      const fitSpy = vi.spyOn(FitAddon.prototype, "fit");
+      const handle = makeHandle({ sessionId: "moving-remount-1" });
+      const open = vi.fn(async () => handle);
+
+      renderView(new MockTerminalGateway(), "/cwd", { open });
+      await waitFor(() => expect(open).toHaveBeenCalledTimes(1));
+
+      for (let i = 0; i < 16; i += 1) {
+        setTerminalBoxSize(420 + i, 220);
+        await new Promise((resolve) => requestAnimationFrame(resolve));
+      }
+
+      expect(fitSpy.mock.calls.length).toBeGreaterThan(12);
+      setTerminalBoxSize(520, 260);
+      await waitFor(() => expect(handle.resize).toHaveBeenCalled());
+
+      fitSpy.mockRestore();
+    });
+
     it("does not refit when refitSignal is left undefined (no-op for callers that don't pass it)", async () => {
       const fitSpy = vi.spyOn(FitAddon.prototype, "fit");
       const open = vi.fn(async () => makeHandle({ sessionId: "no-signal-1" }));

frontend/src/features/terminals/TerminalView.tsx

@@ -191,7 +191,7 @@ export function TerminalView({
   // Holds the mounted instance's `refit` closure so the `refitSignal` effect
   // below (a separate effect, since it must NOT re-run/reopen the terminal on
   // every parent render) can trigger it without depending on `cwd`'s effect.
-  const refitRef = useRef<((settleFrames?: number) => void) | null>(null);
+  const refitRef = useRef<((maxFrames?: number) => void) | null>(null);
 
   useEffect(() => {
     const container = containerRef.current;
@@ -229,7 +229,6 @@ export function TerminalView({
     let lastRows = term.rows;
     let lastCols = term.cols;
     let hasUsefulFit = false;
-    let settleFramesRemaining = 0;
 
     // Keystroke → PTY path. The agent cell is a **native terminal**
     // (ARCHITECTURE §20): keystrokes reach the PTY exactly like a plain shell.
@@ -363,34 +362,51 @@ export function TerminalView({
     // doesn't spin forever.
     // A successful fit can also land on a non-zero but still intermediate box
     // during project/layout switches, split/merge commits, re-attach, and OS
-    // minimize/restore. Keep a small coalesced tail of fits on following frames
+    // minimize/restore. Instead of guessing a fixed number of follow-up frames,
-    // so the final settled geometry is pushed automatically without requiring a
+    // keep fitting until the measured DOM box and resulting xterm grid stay
-    // manual resize. This stays bounded and preserves the rows/cols-changed
+    // stable for consecutive frames. A hard frame cap keeps genuinely unstable
-    // guard before touching the PTY.
+    // or never-laid-out containers bounded.
-    const SETTLE_REFIT_FRAMES = 4;
+    const STABLE_REFIT_FRAMES = 2;
-    // Project switches remount LayoutGrid/TerminalView by key. The new cell can
+    const SETTLE_REFIT_MAX_FRAMES = 24;
-    // report a non-zero but still intermediate box for more than the ordinary
+    const MOUNT_REFIT_MAX_FRAMES = 60;
-    // transition tail, so the mount path keeps fitting a little longer.
+    let refitFramesRemaining = 0;
-    const MOUNT_SETTLE_REFIT_FRAMES = 12;
+    let stableFrames = 0;
-    const MAX_ZERO_SIZE_RETRIES = MOUNT_SETTLE_REFIT_FRAMES;
+    let lastStabilityKey = "";
-    let zeroSizeRetries = 0;
     const refit = () => {
       rafId = 0;
       if (disposed) return;
-      if (container.clientWidth === 0 || container.clientHeight === 0) {
+
-        if (zeroSizeRetries < MAX_ZERO_SIZE_RETRIES) {
+      const consumeFrame = () => {
-          zeroSizeRetries += 1;
+        refitFramesRemaining = Math.max(0, refitFramesRemaining - 1);
+      };
+      const scheduleNextIfNeeded = () => {
+        if (refitFramesRemaining > 0) {
           rafId = requestAnimationFrame(refit);
         }
+      };
+
+      const width = container.clientWidth;
+      const height = container.clientHeight;
+      if (width === 0 || height === 0) {
+        stableFrames = 0;
+        lastStabilityKey = "";
+        consumeFrame();
+        scheduleNextIfNeeded();
         return;
       }
-      zeroSizeRetries = 0;
+
       try {
         fit.fit();
       } catch {
         return;
       }
-      if (term.rows <= 0 || term.cols <= 0) return;
+      if (term.rows <= 0 || term.cols <= 0) {
+        stableFrames = 0;
+        lastStabilityKey = "";
+        consumeFrame();
+        scheduleNextIfNeeded();
+        return;
+      }
 
       const isFirstUsefulFit = !hasUsefulFit;
       if (isFirstUsefulFit) {
@@ -406,23 +422,31 @@ export function TerminalView({
         resizeHandleToCurrentGeometry();
       }
 
-      if (settleFramesRemaining > 0) {
+      const stabilityKey = `${width}x${height}:${term.rows}x${term.cols}`;
-        settleFramesRemaining -= 1;
+      if (stabilityKey === lastStabilityKey) {
-        rafId = requestAnimationFrame(refit);
+        stableFrames += 1;
+      } else {
+        lastStabilityKey = stabilityKey;
+        stableFrames = 1;
       }
+
+      consumeFrame();
+      if (stableFrames < STABLE_REFIT_FRAMES) scheduleNextIfNeeded();
     };
-    const scheduleRefit = (settleFrames = 0) => {
+    const scheduleRefit = (maxFrames = SETTLE_REFIT_MAX_FRAMES) => {
-      settleFramesRemaining = Math.max(settleFramesRemaining, settleFrames);
+      refitFramesRemaining = Math.max(refitFramesRemaining, maxFrames);
+      stableFrames = 0;
+      lastStabilityKey = "";
       if (!rafId) rafId = requestAnimationFrame(refit);
     };
-    const scheduleSettledRefit = () => scheduleRefit(SETTLE_REFIT_FRAMES);
+    const scheduleSettledRefit = () => scheduleRefit(SETTLE_REFIT_MAX_FRAMES);
     const scheduleVisibleRefit = () => {
       if (document.visibilityState === "hidden") return;
       scheduleSettledRefit();
     };
     const ro = new ResizeObserver(() => scheduleRefit());
     ro.observe(container);
-    scheduleRefit(MOUNT_SETTLE_REFIT_FRAMES);
+    scheduleRefit(MOUNT_REFIT_MAX_FRAMES);
     window.addEventListener("resize", scheduleSettledRefit);
     window.addEventListener("focus", scheduleSettledRefit);
     window.addEventListener("pageshow", scheduleSettledRefit);
@@ -468,7 +492,7 @@ export function TerminalView({
   // logic.
   useEffect(() => {
     if (refitSignal === undefined) return;
-    refitRef.current?.(4);
+    refitRef.current?.(24);
   }, [refitSignal]);
 
   const showNetworkBanner =