diff --git a/frontend/src/features/agents/CustomAgentChatView.test.tsx b/frontend/src/features/agents/CustomAgentChatView.test.tsx
index 01acf7b6..a2da99b2 100644
--- a/frontend/src/features/agents/CustomAgentChatView.test.tsx
+++ b/frontend/src/features/agents/CustomAgentChatView.test.tsx
@@ -1176,6 +1176,119 @@ describe("CustomAgentChatView", () => {
     expect(screen.getByText("Terminé").closest(".justify-end")).toBeTruthy();
   });
 
+  it("keeps successive turns isolated when backend userPrompt echoes arrive after progress (#251)", async () => {
+    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: "progress",
+            progress: {
+              source: "providerNative",
+              kind: "tool",
+              stage: "started",
+              label: "shell",
+              toolName: "shell",
+              text: `Running ${prompt}`,
+            },
+          });
+          onChunk({ kind: "userPrompt", text: prompt });
+          onChunk({
+            kind: "progress",
+            progress: {
+              source: "providerNative",
+              kind: "tool",
+              stage: "completed",
+              label: "shell",
+              toolName: "shell",
+              text: `Done ${prompt}`,
+            },
+          });
+          onChunk({ kind: "final", content: `final ${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"
+          nodeId="node-1"
+          sessionId="chat-session-1"
+          conversationId="conversation-1"
+          onSessionId={vi.fn()}
+          onConversationId={vi.fn()}
+        />
+      </DIProvider>,
+    );
+
+    await waitFor(() =>
+      expect(agent.reattachAgentChat).toHaveBeenCalledWith(
+        "chat-session-1",
+        expect.any(Function),
+      ),
+    );
+
+    fireEvent.change(screen.getByLabelText(/message CLI custom/), {
+      target: { value: "first request" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "Envoyer" }));
+    await screen.findByText("final first request");
+
+    fireEvent.change(screen.getByLabelText(/message CLI custom/), {
+      target: { value: "second request" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "Envoyer" }));
+    await screen.findByText("final second request");
+
+    expect(screen.getAllByText("first request")).toHaveLength(1);
+    expect(screen.getAllByText("second request")).toHaveLength(1);
+    expect(screen.getAllByTestId("chat-tool-progress")).toHaveLength(2);
+    expect(screen.queryByText("Running first request")).toBeNull();
+    expect(screen.queryByText("Running second request")).toBeNull();
+    expect(screen.getByText("Done first request")).toBeTruthy();
+    expect(screen.getByText("Done second request")).toBeTruthy();
+    expect(screen.getAllByText("Terminé")).toHaveLength(2);
+
+    const firstPrompt = screen.getByText("first request");
+    const firstProgress = screen.getByText("Done first request");
+    const firstFinal = screen.getByText("final first request");
+    const secondPrompt = screen.getByText("second request");
+    const secondProgress = screen.getByText("Done second request");
+    const secondFinal = screen.getByText("final second request");
+
+    expect(
+      Boolean(firstPrompt.compareDocumentPosition(firstProgress) & Node.DOCUMENT_POSITION_FOLLOWING),
+    ).toBe(true);
+    expect(
+      Boolean(firstProgress.compareDocumentPosition(firstFinal) & Node.DOCUMENT_POSITION_FOLLOWING),
+    ).toBe(true);
+    expect(
+      Boolean(firstFinal.compareDocumentPosition(secondPrompt) & Node.DOCUMENT_POSITION_FOLLOWING),
+    ).toBe(true);
+    expect(
+      Boolean(secondPrompt.compareDocumentPosition(secondProgress) & Node.DOCUMENT_POSITION_FOLLOWING),
+    ).toBe(true);
+    expect(
+      Boolean(secondProgress.compareDocumentPosition(secondFinal) & Node.DOCUMENT_POSITION_FOLLOWING),
+    ).toBe(true);
+  });
+
   it("renders canonical progress chunks as live agent, MCP, and delegation activity", async () => {
     const agent = {
       launchAgentChat: vi.fn(),
@@ -2293,7 +2406,7 @@ describe("CustomAgentChatView", () => {
     expect(screen.getByText("Progress").parentElement?.textContent).toContain("Terminé");
   });
 
-  it("renders late progress chunks after the final answer without reopening the turn", async () => {
+  it("ignores late progress chunks after the final answer without reopening the turn", async () => {
     let emitChunk: ((chunk: unknown) => void) | null = null;
     const agent = {
       launchAgentChat: vi.fn(),
@@ -2368,7 +2481,7 @@ describe("CustomAgentChatView", () => {
     });
 
     expect(screen.getByText("done")).toBeTruthy();
-    expect(screen.getByText("idea_ticket_read")).toBeTruthy();
+    expect(screen.queryByText("idea_ticket_read")).toBeNull();
     expect(screen.getByRole("button", { name: "Envoyer" })).toBeTruthy();
     expect(screen.queryByRole("button", { name: "Stop" })).toBeNull();
   });
diff --git a/frontend/src/features/agents/CustomAgentChatView.tsx b/frontend/src/features/agents/CustomAgentChatView.tsx
index f09dabca..dc80bb9d 100644
--- a/frontend/src/features/agents/CustomAgentChatView.tsx
+++ b/frontend/src/features/agents/CustomAgentChatView.tsx
@@ -236,24 +236,31 @@ function appendUserPrompt(
   text: string,
   attachments: string[] = [],
   receivedAtMs = Date.now(),
-): ChatTurn[] {
-  const last = turns[turns.length - 1];
-  if (
-    last?.role === "user" &&
-    last.text === text &&
-    JSON.stringify(last.attachments ?? []) === JSON.stringify(attachments)
-  ) {
-    return turns;
+): { turns: ChatTurn[]; appended: boolean } {
+  for (let index = turns.length - 1; index >= 0; index -= 1) {
+    const turn = turns[index];
+    if (turn.role === "final" || turn.role === "error") break;
+    if (turn.role !== "user") continue;
+    if (
+      turn.text === text &&
+      JSON.stringify(turn.attachments ?? []) === JSON.stringify(attachments)
+    ) {
+      return { turns, appended: false };
+    }
+    break;
   }
-  return [
-    ...turns,
-    {
-      role: "user",
-      text,
-      receivedAtMs,
-      ...(attachments.length > 0 ? { attachments } : {}),
-    },
-  ];
+  return {
+    turns: [
+      ...turns,
+      {
+        role: "user",
+        text,
+        receivedAtMs,
+        ...(attachments.length > 0 ? { attachments } : {}),
+      },
+    ],
+    appended: true,
+  };
 }
 
 function isReplyProgressSource(value: unknown): value is ReplyProgressSource {
@@ -775,14 +782,6 @@ function foldChunk(
     if (isRecoverableNoResponseTurn(last) && raw.kind !== "error") {
       return foldChunk({ ...state, turns: turns.slice(0, -1) }, raw, receivedAtMs);
     }
-    if (raw.kind === "progress") {
-      return appendProgress(state, normalizeProgress(raw.progress) ?? {
-        source: "ideaLocal",
-        kind: "other",
-        stage: "info",
-        label: unknownChunkLabel(raw),
-      });
-    }
     return state;
   }
   switch (raw.kind) {
@@ -838,17 +837,21 @@ function foldChunk(
       return { ...completedState, turns: next };
     }
     case "userPrompt":
-    case "UserPrompt":
+    case "UserPrompt": {
+      const appended = appendUserPrompt(
+        turns,
+        String(raw.text ?? raw.prompt ?? ""),
+        attachmentLabels(raw.attachments),
+        receivedAtMs,
+      );
       return {
         ...state,
-        turns: appendUserPrompt(
-          turns,
-          String(raw.text ?? raw.prompt ?? ""),
-          attachmentLabels(raw.attachments),
-          receivedAtMs,
-        ),
-        progressScope: state.progressScope + 1,
+        turns: appended.turns,
+        progressScope: appended.appended
+          ? state.progressScope + 1
+          : state.progressScope,
       };
+    }
     default:
       return {
         ...state,