fix(e2b): close remote lifecycle gaps

packages/e2b/fs-e2b/src/index.ts

@@ -199,6 +199,7 @@ export class E2BFileSystem extends FileSystem {
         const reader = stream.getReader()
         const decoder = new TextDecoder('utf-8', { fatal: true })
         let sampledBytes = 0
+        let completed = false
         try {
           while (true) {
             assertNotAborted(signal, 'read')
@@ -222,9 +223,17 @@ export class E2BFileSystem extends FileSystem {
           } catch (error: unknown) {
             throw new FsError(`cannot read "${displayPath}": invalid UTF-8 text`, 'FS_NOT_TEXT', { cause: error })
           }
+          completed = true
         } catch (error: unknown) {
           throw mapError(error, 'read', displayPath, signal)
         } finally {
+          if (!completed) {
+            try {
+              await reader.cancel()
+            } catch (_streamCancellationFailure) {
+              // The primary read outcome owns the result; cancellation is best-effort after early stop.
+            }
+          }
           reader.releaseLock()
         }
       },

packages/e2b/fs-e2b/tests/filesystem.spec.ts

@@ -12,7 +12,7 @@ import { FsVersion } from '@deepseek-ai/dsh-fs'
 import E2BFileSystem from '@deepseek-ai/dsh-fs-e2b'
 import * as E2BFsInvariant from '../src/invariant.ts'
 import InvariantService from '@deepseek-ai/dsh-invariants'
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 
 interface RemoteNode {
   type: FileType
@@ -38,6 +38,8 @@ class FakeRemote {
   readonly removals: string[] = []
   readonly commands: string[] = []
   streamChunks: Uint8Array[] | undefined
+  streamKeepOpen = false
+  readonly streamCancel = vi.fn()
   nextCommandError: unknown
   nextInfoError: unknown
   nextListError: unknown
@@ -148,10 +150,11 @@ class FakeRemote {
         if (options.format === 'bytes') return data.slice()
         const chunks = this.streamChunks ?? [data.slice()]
         return new ReadableStream<Uint8Array>({
-          start(controller) {
+          start: (controller) => {
             for (const chunk of chunks) controller.enqueue(chunk)
-            controller.close()
+            if (!this.streamKeepOpen) controller.close()
           },
+          cancel: () => { this.streamCancel() },
         })
       },
       list: async (path: string, options?: { depth?: number; signal?: AbortSignal }): Promise<EntryInfo[]> => {
@@ -303,6 +306,22 @@ describe('E2BFileSystem identity, metadata, and reads', () => {
     expect(initiallyBuffered).toBe('€')
   })
 
+  it('cancels a remote stream when its consumer stops early', async () => {
+    const remote = new FakeRemote()
+    remote.file('/workspace/text.txt', 'ab')
+    remote.streamChunks = [bytes('a'), bytes('b')]
+    remote.streamKeepOpen = true
+    const { fs } = await setup(remote)
+    const stream = await fs.streamText(await fs.resolve('text.txt'))
+
+    for await (const chunk of stream) {
+      expect(chunk).toBe('a')
+      break
+    }
+
+    expect(remote.streamCancel).toHaveBeenCalledOnce()
+  })
+
   it('matches local binary sampling while edits still reject any NUL byte', async () => {
     const remote = new FakeRemote()
     remote.file('/workspace/late-nul.txt', `${'a'.repeat(8192)}\0tail`)