feat(task): per-task file observation registry (A2, #1375)

src/core/task/Task.ts

@@ -104,6 +104,7 @@ import { ToolRepetitionDetector } from "../tools/ToolRepetitionDetector"
 import { restoreTodoListForTask } from "../tools/UpdateTodoListTool"
 import { FileContextTracker } from "../context-tracking/FileContextTracker"
 import { RooIgnoreController } from "../ignore/RooIgnoreController"
+import { ObservationRegistry } from "./observationRegistry"
 import { RooProtectedController } from "../protect/RooProtectedController"
 import { type AssistantMessageContent, presentAssistantMessage } from "../assistant-message"
 import { NativeToolCallParser } from "../assistant-message/NativeToolCallParser"
@@ -210,6 +211,7 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 	readonly parentTask: Task | undefined = undefined
 	readonly taskNumber: number
 	readonly workspacePath: string
+	readonly observationRegistry = new ObservationRegistry()
 
 	/**
 	 * The mode associated with this task. Persisted across sessions

src/core/task/__tests__/observationRegistry.spec.ts

@@ -0,0 +1,72 @@
+import { describe, it, expect, vi } from "vitest"
+
+import { ObservationRegistry } from "../observationRegistry"
+
+describe("ObservationRegistry", () => {
+	it("observe → get returns the recorded version and observedAt", () => {
+		const reg = new ObservationRegistry()
+		reg.observe("/a/b/c.ts", "1:2:300:4000000000:5000000000")
+
+		const obs = reg.get("/a/b/c.ts")
+		expect(obs).toBeDefined()
+		expect(obs!.version).toBe("1:2:300:4000000000:5000000000")
+		expect(typeof obs!.observedAt).toBe("number")
+	})
+
+	it("re-observe replaces the entry with a fresh observedAt", () => {
+		vi.useFakeTimers()
+		const reg = new ObservationRegistry()
+		reg.observe("/a/b/c.ts", "v1")
+		const first = reg.get("/a/b/c.ts")!
+		expect(first.version).toBe("v1")
+
+		vi.advanceTimersByTime(50)
+		reg.observe("/a/b/c.ts", "v2")
+		const second = reg.get("/a/b/c.ts")!
+		expect(second.version).toBe("v2")
+		expect(second.observedAt).toBeGreaterThan(first.observedAt)
+
+		vi.useRealTimers()
+	})
+
+	it("has returns true for observed paths, false otherwise", () => {
+		const reg = new ObservationRegistry()
+		reg.observe("/x.ts", "t1")
+		expect(reg.has("/x.ts")).toBe(true)
+		expect(reg.has("/y.ts")).toBe(false)
+	})
+
+	it("size reflects the number of observed entries", () => {
+		const reg = new ObservationRegistry()
+		expect(reg.size).toBe(0)
+		reg.observe("/a.ts", "t1")
+		reg.observe("/b.ts", "t2")
+		expect(reg.size).toBe(2)
+	})
+
+	it("clear removes all entries and resets size to 0", () => {
+		const reg = new ObservationRegistry()
+		reg.observe("/a.ts", "t1")
+		reg.observe("/b.ts", "t2")
+		reg.clear()
+		expect(reg.size).toBe(0)
+		expect(reg.get("/a.ts")).toBeUndefined()
+		expect(reg.has("/b.ts")).toBe(false)
+	})
+
+	it("get on empty registry returns undefined", () => {
+		const reg = new ObservationRegistry()
+		expect(reg.get("/any.ts")).toBeUndefined()
+	})
+
+	it("separate instances are independent — observing in one does not appear in the other", () => {
+		const regA = new ObservationRegistry()
+		const regB = new ObservationRegistry()
+		regA.observe("/shared.ts", "v1")
+		expect(regA.get("/shared.ts")).toBeDefined()
+		expect(regB.get("/shared.ts")).toBeUndefined()
+		regB.observe("/shared.ts", "v2")
+		expect(regA.get("/shared.ts")!.version).toBe("v1")
+		expect(regB.get("/shared.ts")!.version).toBe("v2")
+	})
+})

src/core/task/observationRegistry.ts

@@ -0,0 +1,47 @@
+/**
+ * Per-task file observation registry (upstream epic #1375, phase A2).
+ *
+ * Each Task owns its own instance so parent and subtask observations are
+ * independent. The S4 guarded-write will compare these versions against the
+ * token recomputed pre-write to detect stale reads or file replacement.
+ *
+ * Pure in-memory — zero I/O, no dependencies. No behavior change in this PR:
+ * observations are recorded but not consulted.
+ */
+
+export interface FileObservation {
+	/** Version token derived from on-disk fs.stat (bigint mode). */
+	version: string
+	/** Millisecond timestamp when the observation was recorded. */
+	observedAt: number
+}
+
+export class ObservationRegistry {
+	private readonly entries = new Map<string, FileObservation>()
+
+	/**
+	 * Record an observation for a file at its absolute path.
+	 *
+	 * Re-observing replaces the entry with a fresh observedAt timestamp and
+	 * the new version token.
+	 */
+	observe(absolutePath: string, version: string): void {
+		this.entries.set(absolutePath, { version, observedAt: Date.now() })
+	}
+
+	get(absolutePath: string): FileObservation | undefined {
+		return this.entries.get(absolutePath)
+	}
+
+	has(absolutePath: string): boolean {
+		return this.entries.has(absolutePath)
+	}
+
+	clear(): void {
+		this.entries.clear()
+	}
+
+	get size(): number {
+		return this.entries.size
+	}
+}

src/core/tools/ReadFileTool.ts

@@ -16,6 +16,7 @@
 import { isLegacyReadFileParams, type ClineSayTool } from "@roo-code/types"
 
 import { Task } from "../task/Task"
+import { computeVersionToken } from "../../utils/versionToken"
 import { formatResponse } from "../prompts/responses"
 import { RecordSource } from "../context-tracking/FileContextTrackerTypes"
 import { isPathOutsideWorkspace } from "../../utils/pathUtils"
@@ -220,6 +221,11 @@
 
 					await task.fileContextTracker.trackFileContext(relPath, "read_tool" as RecordSource)
 
+					// A2 (plan #33 / epic #1375): record the observed on-disk version for the future write guard.
+					// A stat failure leaves the target unobserved and never fails the read.
+					const version = await computeVersionToken(fullPath).catch(() => undefined)
+					if (version) task.observationRegistry.observe(fullPath, version)
+
 					updateFileResult(relPath, {
 						nativeContent: `File: ${relPath}\n${result}`,
 					})
@@ -799,6 +805,12 @@
 
 				// Track file in context
 				await task.fileContextTracker.trackFileContext(relPath, "read_tool")
+
+				// A2 (plan #33 / epic #1375): mirror the native path — record the observed
+				// on-disk version so legacy-format reads also feed the future write guard.
+				// A stat failure leaves the target unobserved and never fails the read.
+				const version = await computeVersionToken(fullPath).catch(() => undefined)
+				if (version) task.observationRegistry.observe(fullPath, version)
 			} catch (error) {
 				const errorMsg = error instanceof Error ? error.message : String(error)
 				results.push(`File: ${relPath}\nError: ${errorMsg}`)

src/core/tools/__tests__/readFileTool.spec.ts

@@ -13,10 +13,16 @@
  */
 
 import path from "path"
+import type { Stats } from "fs"
+
+import type { LegacyReadFileParams } from "@roo-code/types"
 
 import { isBinaryFile } from "isbinaryfile"
 
 import { readFileTool, ReadFileTool } from "../ReadFileTool"
+import type { Task } from "../../task/Task"
+import { ObservationRegistry } from "../../task/observationRegistry"
+import { computeVersionToken } from "../../../utils/versionToken"
 import { formatResponse } from "../../prompts/responses"
 import {
 	validateImageForProcessing,
@@ -136,13 +142,17 @@ interface MockTaskOptions {
 	rooIgnoreAllowed?: boolean
 	maxImageFileSize?: number
 	maxTotalImageSize?: number
+	observationRegistry?: ObservationRegistry
 }
 
 function createMockTask(options: MockTaskOptions = {}) {
 	const { supportsImages = false, rooIgnoreAllowed = true, maxImageFileSize = 5, maxTotalImageSize = 20 } = options
 
 	return {
 		cwd: "/test/workspace",
+		// Mirror Task: every task always owns an observation registry (A2, #1375).
+		// Tests asserting on observations pass their own instance via options.
+		observationRegistry: options.observationRegistry ?? new ObservationRegistry(),
 		api: {
 			getModel: vi.fn().mockReturnValue({
 				info: { supportsImages },
@@ -1489,5 +1499,108 @@ describe("ReadFileTool", () => {
 
 			expect(mockTask.didToolFailInCurrentTurn).toBe(true)
 		})
+
+		describe("observation registry", () => {
+			it("records an observation on successful read of an existing file", async () => {
+				const mockTask = createMockTask({
+					observationRegistry: new ObservationRegistry(),
+				})
+				const callbacks = createMockCallbacks()
+
+				// Override the beforeEach default stat mock with proper BigIntStats.
+				mockedFsStat.mockResolvedValue({
+					isDirectory: () => false,
+					dev: BigInt(1),
+					ino: BigInt(2),
+					size: BigInt(300),
+					mtimeNs: BigInt(4_000_000_000n),
+					ctimeNs: BigInt(5_000_000_000n),
+					// Cast: the mock only implements the members the tool and versionToken read.
+				} as unknown as Stats)
+				mockedIsBinaryFile.mockResolvedValue(false)
+
+				// Spy on observe to capture the exact key used (Windows path.resolve may use backslashes).
+				const reg = mockTask.observationRegistry!
+				const observeSpy = vi.spyOn(reg, "observe")
+
+				// Cast: the mock task only implements the members ReadFileTool.execute touches.
+				await readFileTool.execute({ path: "existing.ts" }, mockTask as unknown as Task, callbacks)
+
+				// Verify the tool called observe exactly once with a valid token.
+				expect(observeSpy).toHaveBeenCalledTimes(1)
+				const [calledPath, calledVersion] = observeSpy.mock.calls[0]
+				expect(calledPath).toContain("existing.ts")
+				expect(calledVersion).toMatch(/^\d+:\d+:\d+:\d+:\d+$/)
+
+				// Verify get() returns the same data using the spy-captured key.
+				const obs = reg.get(calledPath)
+				expect(obs).toBeDefined()
+				expect(obs!.version).toBe(calledVersion)
+			})
+
+			it("a failed read (absent path) leaves the registry size 0 and does not throw", async () => {
+				const mockTask = createMockTask({
+					observationRegistry: new ObservationRegistry(),
+				})
+				const callbacks = createMockCallbacks()
+
+				mockedFsReadFile.mockRejectedValue(new Error("ENOENT"))
+
+				// Cast: the mock task only implements the members ReadFileTool.execute touches.
+				await readFileTool.execute({ path: "missing.ts" }, mockTask as unknown as Task, callbacks)
+
+				// observationRegistry is guaranteed present because we passed it in createMockTask.
+				const reg = mockTask.observationRegistry
+				expect(reg).toBeDefined()
+				expect(reg!.size).toBe(0)
+			})
+
+			it("records an observation for legacy-format reads of existing files", async () => {
+				const mockTask = createMockTask({
+					observationRegistry: new ObservationRegistry(),
+				})
+				const callbacks = createMockCallbacks()
+
+				mockedFsStat.mockResolvedValue({
+					isDirectory: () => false,
+					dev: BigInt(1),
+					ino: BigInt(2),
+					size: BigInt(300),
+					mtimeNs: BigInt(4_000_000_000n),
+					ctimeNs: BigInt(5_000_000_000n),
+					// Cast: the mock only implements the members the tool and versionToken read.
+				} as unknown as Stats)
+				mockedIsBinaryFile.mockResolvedValue(false)
+
+				const reg = mockTask.observationRegistry!
+				const observeSpy = vi.spyOn(reg, "observe")
+
+				// Typed legacy (pre-refactor) params: the multi-file format with the
+				// _legacyFormat discriminant (see LegacyReadFileParams).
+				const legacyParams: LegacyReadFileParams = {
+					files: [{ path: "legacy.ts" }],
+					_legacyFormat: true,
+				}
+
+				// Cast: the mock task only implements the members ReadFileTool.execute touches.
+				await readFileTool.execute(legacyParams, mockTask as unknown as Task, callbacks)
+
+				expect(observeSpy).toHaveBeenCalledTimes(1)
+				const [calledPath, calledVersion] = observeSpy.mock.calls[0]
+				expect(calledPath).toContain("legacy.ts")
+				expect(calledVersion).toMatch(/^\d+:\d+:\d+:\d+:\d+$/)
+			})
+
+			it("two separate Task-owned registries are independent", async () => {
+				const regA = new ObservationRegistry()
+				const regB = new ObservationRegistry()
+				regA.observe("/shared.ts", "v1")
+				expect(regA.get("/shared.ts")!.version).toBe("v1")
+				expect(regB.get("/shared.ts")).toBeUndefined()
+				regB.observe("/shared.ts", "v2")
+				expect(regA.get("/shared.ts")!.version).toBe("v1")
+				expect(regB.get("/shared.ts")!.version).toBe("v2")
+			})
+		})
 	})
 })