fix(frontend): ArrowUp rappelle l'historique chat même en multiligne — #304 (cause: le handler ArrowUp remontait dans le texte dès que le draft faisait plus d'une ligne, au lieu de rappeler le message précédent; fix type terminal: ArrowUp déclenche le rappel historique uniquement quand le curseur est à la fin de la dernière ligne du textarea, sinon navigation caret normale préservée; ArrowDown symétrique en fin de draft pour redescendre dans l'historique; QA verte reconfirmée par Git: npm test -- src/features/agents/CustomAgentChatView.test.tsx 71/71, npm run typecheck OK, git diff --check OK; QA fournie: npm run build OK; fichiers .ideai/* tickets/counter/index/attachments et scripts/ hors périmètre; aucun push)

frontend/src/features/agents/CustomAgentChatView.test.tsx

@@ -138,6 +138,57 @@ function setMeasuredTextOverflow(
   fireEvent(window, new Event("resize"));
 }
 
+function renderHistoryChat() {
+  const agent = {
+    launchAgentChat: vi.fn(),
+    reattachAgentChat: vi.fn(async (sessionId: string) => ({
+      sessionId,
+      scrollback: [],
+    })),
+    sendAgentChat: vi.fn(
+      async (_sessionId: string, prompt: string, onChunk: (chunk: ReplyChunk) => void) => {
+        onChunk({ kind: "final", content: `answer ${prompt}` });
+      },
+    ),
+    cancelAgentChat: vi.fn(async () => {}),
+    closeAgentChat: vi.fn(async () => {}),
+  };
+  render(
+    <DIProvider
+      gateways={{
+        agent,
+        system: { pickFile: vi.fn(async () => null) },
+      } as unknown as Gateways}
+    >
+      <CustomAgentChatView
+        projectId="project-1"
+        agentId="agent-1"
+        agentName="Worker"
+        profile={profile}
+        cwd="/repo"
+        layoutId="layout-1"
+        nodeId="node-1"
+        sessionId="chat-session-1"
+        conversationId="conversation-1"
+        onSessionId={vi.fn()}
+        onConversationId={vi.fn()}
+      />
+    </DIProvider>,
+  );
+  return agent;
+}
+
+async function sendHistoryPrompt(
+  composer: HTMLTextAreaElement,
+  agent: ReturnType<typeof renderHistoryChat>,
+  prompt: string,
+) {
+  const expectedCalls = agent.sendAgentChat.mock.calls.length + 1;
+  fireEvent.change(composer, { target: { value: prompt } });
+  fireEvent.click(screen.getByRole("button", { name: "Envoyer" }));
+  await waitFor(() => expect(agent.sendAgentChat).toHaveBeenCalledTimes(expectedCalls));
+}
+
 describe("CustomAgentChatView", () => {
   beforeEach(() => {
     vi.clearAllMocks();
@@ -532,6 +583,95 @@ describe("CustomAgentChatView", () => {
     await waitFor(() => expect(composer.value).toBe("draft in progress"));
   });
 
+  it("recalls history from the exact end of a multiline draft and restores it verbatim", async () => {
+    const agent = renderHistoryChat();
+    const composer = (await screen.findByLabelText(
+      /message CLI custom/,
+    )) as HTMLTextAreaElement;
+    await waitFor(() => expect(agent.reattachAgentChat).toHaveBeenCalled());
+    await sendHistoryPrompt(composer, agent, "historic prompt");
+
+    const multilineDraft = "ligne 1\nligne 2\nfin 🧪  ";
+    fireEvent.change(composer, { target: { value: multilineDraft } });
+    composer.setSelectionRange(multilineDraft.length, multilineDraft.length);
+    Object.defineProperty(composer, "scrollHeight", {
+      value: 480,
+      configurable: true,
+    });
+    composer.scrollTop = 0;
+
+    expect(fireEvent.keyDown(composer, { key: "ArrowUp" })).toBe(false);
+    await waitFor(() => expect(composer.value).toBe("historic prompt"));
+    expect(composer.selectionStart).toBe(composer.value.length);
+    expect(composer.selectionEnd).toBe(composer.value.length);
+    expect(composer.scrollTop).toBe(480);
+
+    expect(fireEvent.keyDown(composer, { key: "ArrowDown" })).toBe(false);
+    await waitFor(() => expect(composer.value).toBe(multilineDraft));
+    expect(composer.selectionStart).toBe(multilineDraft.length);
+    expect(composer.selectionEnd).toBe(multilineDraft.length);
+    expect(composer.scrollTop).toBe(480);
+  });
+
+  it("keeps ArrowUp native away from a simple end caret or during modified/IME input", async () => {
+    const agent = renderHistoryChat();
+    const composer = (await screen.findByLabelText(
+      /message CLI custom/,
+    )) as HTMLTextAreaElement;
+    await waitFor(() => expect(agent.reattachAgentChat).toHaveBeenCalled());
+    await sendHistoryPrompt(composer, agent, "historic prompt");
+
+    const draft = "première\ndeuxième";
+    const nativeCases: Array<{
+      selection: [number, number];
+      event?: Record<string, unknown>;
+    }> = [
+      { selection: [4, 4] },
+      { selection: [0, draft.length] },
+      { selection: [draft.length, draft.length], event: { shiftKey: true } },
+      { selection: [draft.length, draft.length], event: { ctrlKey: true } },
+      { selection: [draft.length, draft.length], event: { altKey: true } },
+      { selection: [draft.length, draft.length], event: { metaKey: true } },
+      { selection: [draft.length, draft.length], event: { isComposing: true } },
+      { selection: [draft.length, draft.length], event: { keyCode: 229 } },
+    ];
+    for (const testCase of nativeCases) {
+      fireEvent.change(composer, { target: { value: draft } });
+      composer.setSelectionRange(...testCase.selection);
+      expect(
+        fireEvent.keyDown(composer, { key: "ArrowUp", ...testCase.event }),
+      ).toBe(true);
+      expect(composer.value).toBe(draft);
+    }
+
+    composer.setSelectionRange(draft.length, draft.length);
+    expect(fireEvent.keyDown(composer, { key: "ArrowUp" })).toBe(false);
+    await waitFor(() => expect(composer.value).toBe("historic prompt"));
+  });
+
+  it("does not consume ArrowUp with empty history and never mutates recalled entries", async () => {
+    const agent = renderHistoryChat();
+    const composer = (await screen.findByLabelText(
+      /message CLI custom/,
+    )) as HTMLTextAreaElement;
+    await waitFor(() => expect(agent.reattachAgentChat).toHaveBeenCalled());
+
+    expect(fireEvent.keyDown(composer, { key: "ArrowUp" })).toBe(true);
+    await sendHistoryPrompt(composer, agent, "original history");
+    fireEvent.keyDown(composer, { key: "ArrowUp" });
+    await waitFor(() => expect(composer.value).toBe("original history"));
+
+    fireEvent.change(composer, { target: { value: "edited recall" } });
+    composer.setSelectionRange(composer.value.length, composer.value.length);
+    fireEvent.keyDown(composer, { key: "ArrowUp" });
+    await waitFor(() => expect(composer.value).toBe("original history"));
+
+    fireEvent.click(screen.getByRole("button", { name: "Envoyer" }));
+    await waitFor(() => expect(agent.sendAgentChat).toHaveBeenCalledTimes(2));
+    expect(composer.value).toBe("");
+    expect(fireEvent.keyDown(composer, { key: "ArrowDown" })).toBe(true);
+  });
+
   it("persists prompt history across a custom chat remount", async () => {
     const agent = {
       launchAgentChat: vi.fn(),
@@ -3422,7 +3562,7 @@ describe("CustomAgentChatView", () => {
     expect(screen.getByRole("option", { name: /\/clean/ })).toBeTruthy();
     expect(screen.getByRole("option", { name: /\/commit/ })).toBeTruthy();
 
-    fireEvent.keyDown(composer, { key: "ArrowDown" });
+    fireEvent.keyDown(composer, { key: "ArrowUp" });
     fireEvent.keyDown(composer, { key: "Enter" });
 
     await waitFor(() => expect(composer.value).toBe("/commit "));