diff --git a/webview-ui/src/components/chat/__tests__/ChatTextArea.spec.tsx b/webview-ui/src/components/chat/__tests__/ChatTextArea.spec.tsx
index aae9ac3cc6..ce22d4b07c 100644
--- a/webview-ui/src/components/chat/__tests__/ChatTextArea.spec.tsx
+++ b/webview-ui/src/components/chat/__tests__/ChatTextArea.spec.tsx
@@ -583,6 +583,38 @@ describe("ChatTextArea", () => {
 				expect(setInputValue).toHaveBeenCalledWith("Current input")
 			})
 
+			it("should preserve current input while assistant messages stream", () => {
+				const setInputValue = vi.fn()
+				const { container, rerender } = render(
+					<ChatTextArea {...defaultProps} setInputValue={setInputValue} inputValue="Current input" />,
+				)
+				const textarea = container.querySelector("textarea")!
+
+				textarea.setSelectionRange(0, 0)
+				fireEvent.keyDown(textarea, { key: "ArrowUp" })
+				expect(setInputValue).toHaveBeenCalledWith("Third prompt")
+				;(useExtensionState as ReturnType<typeof vi.fn>).mockReturnValue({
+					filePaths: [],
+					openedTabs: [],
+					apiConfiguration: {
+						apiProvider: providerIdentifiers.anthropic,
+					},
+					taskHistory: [],
+					clineMessages: [
+						...mockClineMessages,
+						{ type: "say", say: "text", text: "Streaming assistant output", ts: 4000 },
+					],
+					cwd: "/test/workspace",
+				})
+				setInputValue.mockClear()
+				rerender(<ChatTextArea {...defaultProps} setInputValue={setInputValue} inputValue="Third prompt" />)
+				textarea.setSelectionRange(textarea.value.length, textarea.value.length)
+
+				fireEvent.keyDown(textarea, { key: "ArrowDown" })
+
+				expect(setInputValue).toHaveBeenCalledWith("Current input")
+			})
+
 			it("should reset history navigation when user types", () => {
 				const setInputValue = vi.fn()
 				const { container } = render(
diff --git a/webview-ui/src/components/chat/hooks/__tests__/usePromptHistory.spec.ts b/webview-ui/src/components/chat/hooks/__tests__/usePromptHistory.spec.ts
new file mode 100644
index 0000000000..ee51191429
--- /dev/null
+++ b/webview-ui/src/components/chat/hooks/__tests__/usePromptHistory.spec.ts
@@ -0,0 +1,84 @@
+import { ClineMessage, HistoryItem } from "@roo-code/types"
+import { act, renderHook } from "@testing-library/react"
+
+import { usePromptHistory, type UsePromptHistoryReturn } from "../usePromptHistory"
+
+describe("usePromptHistory", () => {
+	it("resets navigation when switching to conversation history with identical prompts", () => {
+		const prompt = "Explain this code"
+		const taskHistory: HistoryItem[] = [
+			{
+				id: "task-1",
+				number: 1,
+				ts: 1,
+				task: prompt,
+				tokensIn: 0,
+				tokensOut: 0,
+				totalCost: 0,
+				workspace: "/workspace",
+			},
+		]
+		const conversationHistory: ClineMessage[] = [{ ts: 2, type: "say", say: "user_feedback", text: prompt }]
+		const setInputValue = vi.fn()
+
+		const { result, rerender } = renderHook<UsePromptHistoryReturn, { clineMessages: ClineMessage[] | undefined }>(
+			({ clineMessages }) =>
+				usePromptHistory({
+					clineMessages,
+					taskHistory,
+					cwd: "/workspace",
+					inputValue: "draft",
+					setInputValue,
+				}),
+			{ initialProps: { clineMessages: undefined } },
+		)
+
+		act(() => {
+			result.current.setHistoryIndex(0)
+			result.current.setTempInput("draft")
+		})
+
+		expect(result.current.promptHistory).toEqual([prompt])
+		expect(result.current.historyIndex).toBe(0)
+		expect(result.current.tempInput).toBe("draft")
+
+		rerender({ clineMessages: conversationHistory })
+
+		expect(result.current.promptHistory).toEqual([prompt])
+		expect(result.current.historyIndex).toBe(-1)
+		expect(result.current.tempInput).toBe("")
+	})
+
+	it("resets navigation when the current history source gains a prompt", () => {
+		const firstPrompt = "Explain this code"
+		const secondPrompt = "Now simplify it"
+		const initialHistory: ClineMessage[] = [{ ts: 1, type: "say", say: "user_feedback", text: firstPrompt }]
+		const updatedHistory: ClineMessage[] = [
+			...initialHistory,
+			{ ts: 2, type: "say", say: "user_feedback", text: secondPrompt },
+		]
+
+		const { result, rerender } = renderHook<UsePromptHistoryReturn, { clineMessages: ClineMessage[] }>(
+			({ clineMessages }) =>
+				usePromptHistory({
+					clineMessages,
+					taskHistory: undefined,
+					cwd: "/workspace",
+					inputValue: "draft",
+					setInputValue: vi.fn(),
+				}),
+			{ initialProps: { clineMessages: initialHistory } },
+		)
+
+		act(() => {
+			result.current.setHistoryIndex(0)
+			result.current.setTempInput("draft")
+		})
+
+		rerender({ clineMessages: updatedHistory })
+
+		expect(result.current.promptHistory).toEqual([secondPrompt, firstPrompt])
+		expect(result.current.historyIndex).toBe(-1)
+		expect(result.current.tempInput).toBe("")
+	})
+})
diff --git a/webview-ui/src/components/chat/hooks/usePromptHistory.ts b/webview-ui/src/components/chat/hooks/usePromptHistory.ts
index 402538182a..fef127953a 100644
--- a/webview-ui/src/components/chat/hooks/usePromptHistory.ts
+++ b/webview-ui/src/components/chat/hooks/usePromptHistory.ts
@@ -1,5 +1,5 @@
 import { ClineMessage, HistoryItem } from "@roo-code/types"
-import { useCallback, useEffect, useMemo, useState } from "react"
+import { useCallback, useEffect, useMemo, useRef, useState } from "react"
 
 interface UsePromptHistoryProps {
 	clineMessages: ClineMessage[] | undefined
@@ -38,6 +38,8 @@ export const usePromptHistory = ({
 	const [historyIndex, setHistoryIndex] = useState(-1)
 	const [tempInput, setTempInput] = useState("")
 	const [promptHistory, setPromptHistory] = useState<string[]>([])
+	const historySource = clineMessages?.length ? "conversation" : "task"
+	const previousHistorySource = useRef(historySource)
 
 	// Initialize prompt history with hybrid approach: conversation messages if in task, otherwise task history
 	const filteredPromptHistory = useMemo(() => {
@@ -71,11 +73,21 @@ export const usePromptHistory = ({
 
 	// Update prompt history when filtered history changes and reset navigation
 	useEffect(() => {
-		setPromptHistory(filteredPromptHistory)
+		const historyChanged =
+			promptHistory.length !== filteredPromptHistory.length ||
+			promptHistory.some((prompt, index) => prompt !== filteredPromptHistory[index])
+		const historySourceChanged = previousHistorySource.current !== historySource
+		previousHistorySource.current = historySource
+
+		if (!historyChanged && !historySourceChanged) return
+
+		if (historyChanged) {
+			setPromptHistory(filteredPromptHistory)
+		}
 		// Reset navigation state when switching between history sources
 		setHistoryIndex(-1)
 		setTempInput("")
-	}, [filteredPromptHistory])
+	}, [filteredPromptHistory, historySource, promptHistory])
 
 	// Reset history navigation when user types (but not when we're setting it programmatically)
 	const resetOnInputChange = useCallback(() => {