diff --git a/src/__tests__/conversation-checkpoint-task.spec.ts b/src/__tests__/conversation-checkpoint-task.spec.ts
new file mode 100644
index 0000000000..e034ec8b6c
--- /dev/null
+++ b/src/__tests__/conversation-checkpoint-task.spec.ts
@@ -0,0 +1,79 @@
+// npx vitest run __tests__/conversation-checkpoint-task.spec.ts
+
+import { describe, it, expect, beforeEach, afterEach } from "vitest"
+import * as fs from "fs/promises"
+import * as os from "os"
+import * as path from "path"
+
+import type { ClineMessage } from "@roo-code/types"
+import { Task } from "../core/task/Task"
+
+function makeMessages(n: number): ClineMessage[] {
+	return Array.from(
+		{ length: n },
+		(_, i) =>
+			({
+				type: "user",
+				text: `message ${i}`,
+				ts: 1000 + i,
+			}) as unknown as ClineMessage,
+	)
+}
+
+let tmpDir: string
+
+beforeEach(async () => {
+	tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "conv-checkpoint-task-"))
+})
+
+afterEach(async () => {
+	await fs.rm(tmpDir, { recursive: true, force: true })
+})
+
+/**
+ * Task double carrying only the fields the checkpoint trigger methods read.
+ * The real prototype methods are bound onto the stub so we exercise the actual
+ * Task code path (getTaskDirectoryPath + storage module) without instantiating a Task.
+ */
+function makeTaskDouble(taskId: string, messages: ClineMessage[]) {
+	const proto = Task.prototype as unknown as {
+		createConversationCheckpoint: (this: object, summary?: string) => Promise<unknown>
+		listConversationCheckpoints: (this: object) => Promise<unknown[]>
+	}
+	const stub = { taskId, globalStoragePath: tmpDir, clineMessages: messages }
+	return Object.assign(stub, {
+		createConversationCheckpoint: proto.createConversationCheckpoint.bind(stub),
+		listConversationCheckpoints: proto.listConversationCheckpoints.bind(stub),
+	}) as unknown as Task
+}
+
+describe("Task.createConversationCheckpoint", () => {
+	it("persists the full message history under <taskDir>/checkpoints and returns the checkpoint", async () => {
+		const task = makeTaskDouble("task-1", makeMessages(2))
+
+		const cp = await task.createConversationCheckpoint("halfway")
+
+		expect(cp.taskId).toBe("task-1")
+		expect(cp.summary).toBe("halfway")
+		expect(cp.messages).toHaveLength(2)
+
+		// Lands in the standard task directory layout: <storage>/tasks/<taskId>/checkpoints/<id>.json
+		const raw = JSON.parse(
+			await fs.readFile(path.join(tmpDir, "tasks", "task-1", "checkpoints", `${cp.id}.json`), "utf8"),
+		) as { taskId: string; messages: unknown[] }
+		expect(raw.taskId).toBe("task-1")
+		expect(raw.messages).toHaveLength(2)
+	})
+
+	it("lists checkpoints newest first via listConversationCheckpoints", async () => {
+		const task = makeTaskDouble("task-1", makeMessages(1))
+
+		const cp1 = await task.createConversationCheckpoint()
+		// Ensure a distinct timestamp so ordering is unambiguous.
+		await new Promise((resolve) => setTimeout(resolve, 5))
+		const cp2 = await task.createConversationCheckpoint("second")
+
+		const list = await task.listConversationCheckpoints()
+		expect(list.map((c) => c.id)).toEqual([cp2.id, cp1.id])
+	})
+})
diff --git a/src/core/checkpoints/__tests__/conversation-checkpoint.spec.ts b/src/core/checkpoints/__tests__/conversation-checkpoint.spec.ts
new file mode 100644
index 0000000000..0481c80d61
--- /dev/null
+++ b/src/core/checkpoints/__tests__/conversation-checkpoint.spec.ts
@@ -0,0 +1,143 @@
+// npx vitest run core/checkpoints/__tests__/conversation-checkpoint.spec.ts
+
+import { describe, it, expect, beforeEach, afterEach } from "vitest"
+import * as fs from "fs/promises"
+import * as os from "os"
+import * as path from "path"
+
+import type { ClineMessage } from "@roo-code/types"
+import {
+	saveConversationCheckpoint,
+	listConversationCheckpoints,
+	loadConversationCheckpoint,
+} from "../conversation-checkpoint"
+
+function makeMessages(n: number): ClineMessage[] {
+	return Array.from(
+		{ length: n },
+		(_, i) =>
+			({
+				type: "user",
+				text: `message ${i}`,
+				ts: 1000 + i,
+			}) as unknown as ClineMessage,
+	)
+}
+
+let tmpDir: string
+
+beforeEach(async () => {
+	tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "conv-checkpoint-"))
+})
+
+afterEach(async () => {
+	await fs.rm(tmpDir, { recursive: true, force: true })
+})
+
+describe("saveConversationCheckpoint", () => {
+	it("writes a JSON file named by the creation timestamp and returns the checkpoint", async () => {
+		const messages = makeMessages(3)
+
+		const cp = await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "task-1", messages, now: 2000 })
+
+		expect(cp.id).toBe("2000")
+		expect(cp.taskId).toBe("task-1")
+		expect(cp.createdAt).toBe(2000)
+		const raw = await fs.readFile(path.join(tmpDir, "checkpoints", "2000.json"), "utf8")
+		const parsed = JSON.parse(raw) as { id: string; taskId: string; messages: unknown[] }
+		expect(parsed.id).toBe("2000")
+		expect(parsed.taskId).toBe("task-1")
+		expect(parsed.messages).toHaveLength(3)
+	})
+
+	it("omits the summary field when none is provided and includes it when given", async () => {
+		const noSummary = await saveConversationCheckpoint({
+			taskDir: tmpDir,
+			taskId: "t",
+			messages: makeMessages(1),
+			now: 100,
+		})
+		expect(noSummary.summary).toBeUndefined()
+
+		const withSummary = await saveConversationCheckpoint({
+			taskDir: tmpDir,
+			taskId: "t",
+			messages: makeMessages(1),
+			summary: "halfway done",
+			now: 200,
+		})
+		expect(withSummary.summary).toBe("halfway done")
+
+		const raw = await fs.readFile(path.join(tmpDir, "checkpoints", "100.json"), "utf8")
+		expect(JSON.parse(raw) as Record<string, unknown>).not.toHaveProperty("summary")
+	})
+
+	it("appends a numeric suffix on same-millisecond collisions instead of overwriting", async () => {
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages: makeMessages(1), now: 500 })
+		const second = await saveConversationCheckpoint({
+			taskDir: tmpDir,
+			taskId: "t",
+			messages: makeMessages(2),
+			now: 500,
+		})
+
+		expect(second.id).toBe("500-1")
+		// Both files coexist.
+		await expect(fs.access(path.join(tmpDir, "checkpoints", "500.json"))).resolves.toBeUndefined()
+		await expect(fs.access(path.join(tmpDir, "checkpoints", "500-1.json"))).resolves.toBeUndefined()
+	})
+
+	it("does not mutate the caller's messages array (deep clone)", async () => {
+		const messages = makeMessages(2)
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages, now: 300 })
+		;(messages[0] as { text?: string }).text = "mutated"
+
+		const loaded = await loadConversationCheckpoint(tmpDir, "300")
+		expect((loaded?.messages[0] as { text?: string }).text).toBe("message 0")
+	})
+})
+
+describe("listConversationCheckpoints", () => {
+	it("returns an empty list when the checkpoints directory does not exist", async () => {
+		const result = await listConversationCheckpoints(tmpDir)
+		expect(result).toEqual([])
+	})
+
+	it("lists checkpoints newest first (createdAt desc, then id desc on ties)", async () => {
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages: makeMessages(1), now: 100 })
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages: makeMessages(1), now: 300 })
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages: makeMessages(1), now: 200 })
+
+		const result = await listConversationCheckpoints(tmpDir)
+		expect(result.map((c) => c.id)).toEqual(["300", "200", "100"])
+	})
+
+	it("skips corrupt files rather than failing the listing", async () => {
+		await saveConversationCheckpoint({ taskDir: tmpDir, taskId: "t", messages: makeMessages(1), now: 100 })
+		const dir = path.join(tmpDir, "checkpoints")
+		await fs.writeFile(path.join(dir, "999.json"), "{ not valid json", "utf8")
+
+		const result = await listConversationCheckpoints(tmpDir)
+		expect(result.map((c) => c.id)).toEqual(["100"])
+	})
+})
+
+describe("loadConversationCheckpoint", () => {
+	it("loads a saved checkpoint by id and returns undefined when missing", async () => {
+		await saveConversationCheckpoint({
+			taskDir: tmpDir,
+			taskId: "t",
+			messages: makeMessages(2),
+			summary: "s",
+			now: 400,
+		})
+
+		const loaded = await loadConversationCheckpoint(tmpDir, "400")
+		expect(loaded?.taskId).toBe("t")
+		expect(loaded?.summary).toBe("s")
+		expect(loaded?.messages).toHaveLength(2)
+
+		const missing = await loadConversationCheckpoint(tmpDir, "does-not-exist")
+		expect(missing).toBeUndefined()
+	})
+})
diff --git a/src/core/checkpoints/conversation-checkpoint.ts b/src/core/checkpoints/conversation-checkpoint.ts
new file mode 100644
index 0000000000..c60fab2355
--- /dev/null
+++ b/src/core/checkpoints/conversation-checkpoint.ts
@@ -0,0 +1,117 @@
+import * as fs from "fs/promises"
+import * as path from "path"
+
+import type { ClineMessage } from "@roo-code/types"
+
+/**
+ * A manually-triggered conversation checkpoint.
+ *
+ * Unlike the git-based file checkpoints (RepoPerTaskCheckpointService), a conversation
+ * checkpoint snapshots the task's full message history so the user can restore the
+ * conversation to this point later. Stored as JSON under `<taskDir>/checkpoints/`.
+ */
+export interface ConversationCheckpoint {
+	/** Filename stem: epoch ms, with a `-N` suffix on same-millisecond collisions. */
+	id: string
+	taskId: string
+	createdAt: number
+	summary?: string
+	messages: ClineMessage[]
+}
+
+const CHECKPOINT_DIR = "checkpoints"
+
+function checkpointDir(taskDir: string): string {
+	return path.join(taskDir, CHECKPOINT_DIR)
+}
+
+/**
+ * Saves a conversation checkpoint to `<taskDir>/checkpoints/<id>.json`.
+ *
+ * The id is the creation timestamp; if that file already exists (two checkpoints in the
+ * same millisecond) a `-1`, `-2`, ... suffix is appended so no data is lost.
+ */
+export async function saveConversationCheckpoint(opts: {
+	taskDir: string
+	taskId: string
+	messages: ClineMessage[]
+	summary?: string
+	/** Injectable clock for deterministic tests. Defaults to Date.now(). */
+	now?: number
+}): Promise<ConversationCheckpoint> {
+	const dir = checkpointDir(opts.taskDir)
+	await fs.mkdir(dir, { recursive: true })
+
+	const createdAt = opts.now ?? Date.now()
+	let id = String(createdAt)
+	// Same-millisecond collision guard: append a numeric suffix until the file is free.
+	for (let n = 1; await fileExists(path.join(dir, `${id}.json`)); n++) {
+		id = `${createdAt}-${n}`
+	}
+
+	const checkpoint: ConversationCheckpoint = {
+		id,
+		taskId: opts.taskId,
+		createdAt,
+		...(opts.summary !== undefined ? { summary: opts.summary } : {}),
+		messages: structuredClone(opts.messages),
+	}
+
+	await fs.writeFile(path.join(dir, `${id}.json`), JSON.stringify(checkpoint, null, 2), "utf8")
+	return checkpoint
+}
+
+/** Lists all conversation checkpoints for a task, newest first. Missing dir → empty list. */
+export async function listConversationCheckpoints(taskDir: string): Promise<ConversationCheckpoint[]> {
+	const dir = checkpointDir(taskDir)
+	let entries: string[]
+	try {
+		entries = await fs.readdir(dir)
+	} catch (error) {
+		if ((error as NodeJS.ErrnoException).code === "ENOENT") {
+			return []
+		}
+		throw error
+	}
+
+	const checkpoints: ConversationCheckpoint[] = []
+	for (const entry of entries) {
+		if (!entry.endsWith(".json")) {
+			continue
+		}
+		try {
+			const raw = await fs.readFile(path.join(dir, entry), "utf8")
+			checkpoints.push(JSON.parse(raw) as ConversationCheckpoint)
+		} catch {
+			// Skip corrupt/partial files rather than failing the whole listing.
+		}
+	}
+
+	return checkpoints.sort((a, b) => b.createdAt - a.createdAt || b.id.localeCompare(a.id))
+}
+
+/** Loads a single checkpoint by id. Returns undefined when not found or unreadable. */
+export async function loadConversationCheckpoint(
+	taskDir: string,
+	id: string,
+): Promise<ConversationCheckpoint | undefined> {
+	const file = path.join(checkpointDir(taskDir), `${id}.json`)
+	try {
+		const raw = await fs.readFile(file, "utf8")
+		return JSON.parse(raw) as ConversationCheckpoint
+	} catch (error) {
+		if ((error as NodeJS.ErrnoException).code === "ENOENT") {
+			return undefined
+		}
+		throw error
+	}
+}
+
+async function fileExists(file: string): Promise<boolean> {
+	try {
+		await fs.access(file)
+		return true
+	} catch {
+		return false
+	}
+}
diff --git a/src/core/task/Task.ts b/src/core/task/Task.ts
index 8dfad1d4e0..377ab1484c 100644
--- a/src/core/task/Task.ts
+++ b/src/core/task/Task.ts
@@ -117,6 +117,11 @@ import {
 	saveTaskMessages,
 	taskMetadata,
 } from "../task-persistence"
+import {
+	saveConversationCheckpoint,
+	listConversationCheckpoints,
+	type ConversationCheckpoint,
+} from "../checkpoints/conversation-checkpoint"
 import { getEnvironmentDetails } from "../environment/getEnvironmentDetails"
 import { checkContextWindowExceededError } from "../context/context-management/context-error-handling"
 import {
@@ -1187,6 +1192,29 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 		}
 	}
 
+	/**
+	 * Manually-triggered conversation checkpoint (P4 of the Task Tree plan).
+	 *
+	 * Snapshots the task's full message history to `<taskDir>/checkpoints/<id>.json` so the
+	 * user can restore the conversation to this point later. This is distinct from the
+	 * git-based file checkpoints: it captures the CONVERSATION, not the working tree.
+	 */
+	async createConversationCheckpoint(summary?: string): Promise<ConversationCheckpoint> {
+		const taskDir = await getTaskDirectoryPath(this.globalStoragePath, this.taskId)
+		return saveConversationCheckpoint({
+			taskDir,
+			taskId: this.taskId,
+			messages: structuredClone(this.clineMessages),
+			summary,
+		})
+	}
+
+	/** Lists all conversation checkpoints for this task, newest first. */
+	async listConversationCheckpoints(): Promise<ConversationCheckpoint[]> {
+		const taskDir = await getTaskDirectoryPath(this.globalStoragePath, this.taskId)
+		return listConversationCheckpoints(taskDir)
+	}
+
 	private findMessageByTimestamp(ts: number): ClineMessage | undefined {
 		for (let i = this.clineMessages.length - 1; i >= 0; i--) {
 			if (this.clineMessages[i].ts === ts) {