diff --git a/packages/opencode/src/file/time.ts b/packages/opencode/src/file/time.ts
index 08f7e9a95127..90707f59ea33 100644
--- a/packages/opencode/src/file/time.ts
+++ b/packages/opencode/src/file/time.ts
@@ -4,6 +4,7 @@ import { makeRuntime } from "@/effect/run-service"
 import { AppFileSystem } from "@/filesystem"
 import { Flag } from "@/flag/flag"
 import type { SessionID } from "@/session/schema"
+import { Filesystem } from "../util/filesystem"
 import { Log } from "../util/log"
 
 export namespace FileTime {
@@ -62,6 +63,7 @@ export namespace FileTime {
       )
 
       const getLock = Effect.fn("FileTime.lock")(function* (filepath: string) {
+        filepath = Filesystem.normalizePath(filepath)
         const locks = (yield* InstanceState.get(state)).locks
         const lock = locks.get(filepath)
         if (lock) return lock
@@ -72,18 +74,21 @@ export namespace FileTime {
       })
 
       const read = Effect.fn("FileTime.read")(function* (sessionID: SessionID, file: string) {
+        file = Filesystem.normalizePath(file)
         const reads = (yield* InstanceState.get(state)).reads
         log.info("read", { sessionID, file })
         session(reads, sessionID).set(file, yield* stamp(file))
       })
 
       const get = Effect.fn("FileTime.get")(function* (sessionID: SessionID, file: string) {
+        file = Filesystem.normalizePath(file)
         const reads = (yield* InstanceState.get(state)).reads
         return reads.get(sessionID)?.get(file)?.read
       })
 
       const assert = Effect.fn("FileTime.assert")(function* (sessionID: SessionID, filepath: string) {
         if (disableCheck) return
+        filepath = Filesystem.normalizePath(filepath)
 
         const reads = (yield* InstanceState.get(state)).reads
         const time = reads.get(sessionID)?.get(filepath)
@@ -99,6 +104,7 @@ export namespace FileTime {
       })
 
       const withLock = Effect.fn("FileTime.withLock")(function* <T>(filepath: string, fn: () => Promise<T>) {
+        filepath = Filesystem.normalizePath(filepath)
         return yield* Effect.promise(fn).pipe((yield* getLock(filepath)).withPermits(1))
       })
 
diff --git a/packages/opencode/test/file/time.test.ts b/packages/opencode/test/file/time.test.ts
index db7eaaae0d8b..be3ee0edc574 100644
--- a/packages/opencode/test/file/time.test.ts
+++ b/packages/opencode/test/file/time.test.ts
@@ -11,6 +11,8 @@ afterEach(async () => {
   await Instance.disposeAll()
 })
 
+const wintest = process.platform === "win32" ? test : test.skip
+
 async function touch(file: string, time: number) {
   const date = new Date(time)
   await fs.utimes(file, date, date)
@@ -181,6 +183,23 @@ describe("file/time", () => {
         },
       })
     })
+
+    wintest("treats equivalent Windows path variants as the same file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      const variant = filepath.replace(/^[A-Za-z]:/, "").replaceAll("\\", "/").toLowerCase()
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          await FileTime.read(sessionID, variant)
+
+          expect(await FileTime.get(sessionID, filepath)).toBeInstanceOf(Date)
+          await FileTime.assert(sessionID, filepath)
+        },
+      })
+    })
   })
 
   describe("withLock()", () => {