patch silently overwrites external edits made while approval is pending #60595

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1. opencodejr commented on Oct 30, 2026

   

   opencodejrBot

   on Oct 30, 2026

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   Thanks for the detailed report and the script. I can reproduce this on the latest dev (95fc3c87), run from source.

   The script below does what yours does. It runs the real patch tool on a temp file with first=old\nsecond=old\n and holds it at the approval prompt. While it is held, it writes second=external-change to the file, then approves. The patch returns completed ("Success. Updated the following files: M file.txt"), but the file ends up as first=new\nsecond=old\n. The outside change is silently lost.

   In packages/core/src/tool/plugin/patch.ts, the patch tool reads the file and builds the new content before asking for permission. After approval it writes that content without checking whether the file changed in between. The per-file lock only covers writes made by OpenCode itself, so it doesn't catch an editor saving the file.

   Related issues:

   • [BUG] V1 apply_patch silently overwrites external file changes (missing stale-content check) #31776: the same problem in v1's apply_patch
   • edit and write can silently lose a concurrent successful file update #60509: edit and write racing each other inside OpenCode
   • apply_patch: parallel calls on the same file silently drop one change #53512: two parallel apply_patch calls on the same file

   Reproduction script (patch-race.ts)

   // Run from packages/core of an opencode checkout:
   //   cd packages/core && bun -e "$(cat /path/to/patch-race.ts)"
   import { Effect, Layer, Deferred, Fiber } from 'effect'
   import { AppNodeBuilder } from '@opencode/core/effect/app-node-builder'
   import { LayerNode } from '@opencode/util/effect/layer-node'
   import { makeLocationNode } from '@opencode/util/effect/app-node'
   import { Environment } from '@opencode/core/environment/index'
   import { FileMutation } from '@opencode/core/file-mutation'
   import { Formatter } from '@opencode/core/formatter'
   import { Location } from '@opencode/core/location'
   import { FileAccess } from '@opencode/core/file-access'
   import { Permission } from '@opencode/core/permission'
   import { AbsolutePath } from '@opencode/core/schema'
   import { Session } from '@opencode/core/session'
   import { Tool } from '@opencode/core/tool'
   import { PatchTool } from '@opencode/core/tool/plugin/patch'
   import { location } from './test/fixture/location'
   import { permissionLayer } from './test/lib/permission'
   import { toolIdentity, executeTool, registerToolPlugin } from './test/lib/tool'
   import { mkdtemp } from 'node:fs/promises'
   
   const dir = await mkdtemp('/tmp/oc-patch-external-')
   await Bun.write(dir + '/file.txt', 'first=old\nsecond=old\n')
   const deps = [Tool.node, FileAccess.node, FileMutation.node, Environment.node, Formatter.node, Location.node, Permission.node]
   const node = makeLocationNode({ name: 'race-patch', layer: Layer.effectDiscard(registerToolPlugin(PatchTool.Plugin)), deps })
   const ready = Deferred.makeUnsafe()
   const proceed = Deferred.makeUnsafe()
   const loc = Layer.succeed(Location.Service, Location.Service.of(location({ directory: AbsolutePath.make(dir) })))
   const layer = AppNodeBuilder.build(LayerNode.group([Tool.node, FileAccess.node, FileMutation.node, node]), [
     Location.node.replace(loc),
     Formatter.node.replace(Layer.mock(Formatter.Service, { file: () => Effect.succeed(false) })),
     // Permission prompt: signal "pending", then wait until we approve
     Permission.node.replace(permissionLayer({ assert: () => Deferred.succeed(ready, undefined).pipe(Effect.andThen(Deferred.await(proceed))) })),
   ])
   await Effect.runPromise(
     Effect.gen(function* () {
       const reg = yield* Tool.Service
       const patch = yield* executeTool(reg, {
         sessionID: Session.ID.make('ses_race'),
         ...toolIdentity,
         call: { type: 'tool-call', id: 'patch', name: 'patch', input: { patchText: '*** Begin Patch\n*** Update File: file.txt\n@@\n-first=old\n+first=new\n second=old\n*** End Patch' } },
       }).pipe(Effect.forkChild)
       yield* Deferred.await(ready)
       // External editor saves a change while approval is pending
       yield* Effect.promise(() => Bun.write(dir + '/file.txt', 'first=old\nsecond=external-change\n'))
       console.log('after external write', JSON.stringify(yield* Effect.promise(() => Bun.file(dir + '/file.txt').text())))
       yield* Deferred.succeed(proceed, undefined)
       console.log('patch', JSON.stringify(yield* Fiber.join(patch)))
       console.log('after patch', JSON.stringify(yield* Effect.promise(() => Bun.file(dir + '/file.txt').text())))
     }).pipe(Effect.provide(layer)),
   )

   Run it: bun patch-race.ts
2. opencodejr

   added

   reproduced

   severity:high

   on Oct 30, 2026