diff --git a/packages/attachment/attachment-local/src/compression-limiter.ts b/packages/attachment/attachment-local/src/compression-limiter.ts
index 3935f262a1..26cc1c6ecb 100644
--- a/packages/attachment/attachment-local/src/compression-limiter.ts
+++ b/packages/attachment/attachment-local/src/compression-limiter.ts
@@ -1,5 +1,16 @@
 /** Instance-owned concurrency bound for native image transformations. */
 
+/**
+ * Preserve Error rejections and normalize non-Error native binding values.
+ * @param reason - rejection reason returned by a compression task.
+ * @returns an Error suitable for promise rejection.
+ */
+export function compressionFailure(reason: unknown): Error {
+  return reason instanceof Error
+    ? reason
+    : new Error('Image compression task rejected with a non-Error value.', { cause: reason })
+}
+
 /** FIFO limiter for asynchronous compression work. */
 export class CompressionLimiter {
   private active = 0
@@ -30,9 +41,7 @@ export class CompressionLimiter {
           },
           (error: unknown) => {
             release()
-            reject(error instanceof Error
-              ? error
-              : new Error('Image compression task rejected with a non-Error value.', { cause: error }))
+            reject(compressionFailure(error))
           },
         )
       }
diff --git a/packages/attachment/attachment-local/src/file-store.ts b/packages/attachment/attachment-local/src/file-store.ts
new file mode 100644
index 0000000000..cf4c56edb1
--- /dev/null
+++ b/packages/attachment/attachment-local/src/file-store.ts
@@ -0,0 +1,181 @@
+/** Verbatim content-addressed local file storage. @module @deepseek-ai/dsh-attachment-local/file-store */
+
+import { createHash } from 'node:crypto'
+import { createReadStream } from 'node:fs'
+import { join } from 'node:path'
+import { AttachmentError, AttachmentId } from '@deepseek-ai/dsh-attachment'
+import type {
+  FileAttachmentRef, SaveFileAttachment, SaveFileStreamAttachment,
+} from '@deepseek-ai/dsh-attachment'
+import {
+  publishImmutableAlias, publishImmutableObject, publishImmutableObjectStream,
+} from './store.ts'
+
+const FILE_ID_PATTERN = /^sha256:([a-f0-9]{64})$/
+const WINDOWS_DEVICE_NAME = /^(?:con|prn|aux|nul|com[1-9]|lpt[1-9])$/iu
+
+function isWindowsDeviceName(name: string): boolean {
+  const dot = name.indexOf('.')
+  const stem = (dot < 0 ? name : name.slice(0, dot)).replace(/[. ]+$/u, '')
+  return WINDOWS_DEVICE_NAME.test(stem)
+}
+
+function utf8Prefix(value: string, maxBytes: number): string {
+  let bytes = 0
+  let prefix = ''
+  for (const character of Buffer.from(value).toString('utf8')) {
+    const characterBytes = Buffer.byteLength(character)
+    if (bytes + characterBytes > maxBytes) break
+    prefix += character
+    bytes += characterBytes
+  }
+  return prefix
+}
+
+/**
+ * Sanitize one caller display name into a safe stored leaf name. Both
+ * separator styles are stripped by hand: a POSIX host treats `\` as an
+ * ordinary character, so path.basename would keep a Windows client's full
+ * local path and leak it into the reference and the session log. Characters
+ * Windows refuses in file names become `_` so one reference stays valid on
+ * every supported host.
+ * @param value - caller-declared display name, possibly a full client path.
+ * @returns a non-empty leaf name safe to store on every supported filesystem.
+ */
+export function fileLeafName(value: string | undefined): string {
+  if (value === undefined) return 'file'
+  const leaf = value.slice(Math.max(value.lastIndexOf('/'), value.lastIndexOf('\\')) + 1)
+  let clean = leaf
+    .replace(/[\u0000-\u001f\u007f]/g, '')
+    .replace(/[<>:"|?*]/g, '_')
+    .trim()
+    .replace(/[. ]+$/u, '')
+  if (isWindowsDeviceName(clean)) clean = `_${clean}`
+  clean = utf8Prefix(clean, 255).replace(/[. ]+$/u, '')
+  return clean === '' || clean === '.' || clean === '..' ? 'file' : clean
+}
+
+function ensureFileReference(ref: FileAttachmentRef): string {
+  const match = FILE_ID_PATTERN.exec(String(ref.attachmentId))
+  if (match?.[1] === undefined || ref.name !== fileLeafName(ref.name)) {
+    throw new AttachmentError('File attachment reference is invalid.', 'INVALID_ATTACHMENT_REF')
+  }
+  return match[1]
+}
+
+/**
+ * Derive the absolute immutable-object path for one stored file. The digest
+ * names a directory so the sanitized display name stays the stored leaf name,
+ * giving models and users a path that ends in the real filename.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param ref - durable file reference from the session log or an upload receipt.
+ * @returns provider-local path without reading the object.
+ * @throws an AttachmentError when the reference digest or name is invalid.
+ */
+export function storedFilePath(root: string, ref: FileAttachmentRef): string {
+  const sha256 = ensureFileReference(ref)
+  return join(root, 'files', sha256.slice(0, 2), sha256, ref.name)
+}
+
+/** Canonical object path shared by every display name for one digest. */
+function storedFileObjectPath(root: string, sha256: string): string {
+  return join(root, 'file-objects', sha256.slice(0, 2), sha256)
+}
+
+/**
+ * Commit one file byte-for-byte below a versioned attachment root.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param input - exact bytes and optional display name.
+ * @returns the durable content-addressed file reference.
+ */
+export async function saveFileVerbatim(
+  root: string,
+  input: SaveFileAttachment,
+): Promise<FileAttachmentRef> {
+  const sha256 = createHash('sha256').update(input.data).digest('hex')
+  const ref: FileAttachmentRef = {
+    attachmentId: AttachmentId(`sha256:${sha256}`),
+    name: fileLeafName(input.name),
+    bytes: input.data.byteLength,
+  }
+  const objectPath = storedFileObjectPath(root, sha256)
+  await publishImmutableObject(root, objectPath, input.data, sha256)
+  await publishImmutableAlias(root, objectPath, storedFilePath(root, ref), sha256)
+  return ref
+}
+
+/**
+ * Commit one file byte-for-byte from bounded chunks below a versioned attachment root.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param input - ordered exact bytes, optional cancellation, and display name.
+ * @returns the durable content-addressed file reference.
+ */
+export async function saveFileStreamVerbatim(
+  root: string,
+  input: SaveFileStreamAttachment,
+): Promise<FileAttachmentRef> {
+  const name = fileLeafName(input.name)
+  const stored = await publishImmutableObjectStream(
+    root,
+    input.data,
+    sha256 => storedFileObjectPath(root, sha256),
+    input.signal,
+  )
+  const ref: FileAttachmentRef = {
+    attachmentId: AttachmentId(`sha256:${stored.sha256}`),
+    name,
+    bytes: stored.bytes,
+  }
+  input.signal?.throwIfAborted()
+  await publishImmutableAlias(
+    root,
+    storedFileObjectPath(root, stored.sha256),
+    storedFilePath(root, ref),
+    stored.sha256,
+  )
+  input.signal?.throwIfAborted()
+  return ref
+}
+
+/**
+ * Read one stored file in bounded chunks and verify its byte count and digest.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param ref - durable file reference from the session log.
+ * @param signal - optional cancellation for filesystem reads.
+ * @returns exact stored bytes in order; integrity failures reject after the final chunk.
+ */
+export async function* readFileStreamVerbatim(
+  root: string,
+  ref: FileAttachmentRef,
+  signal?: AbortSignal,
+): AsyncIterable<Uint8Array> {
+  signal?.throwIfAborted()
+  const sha256 = ensureFileReference(ref)
+  const stream = createReadStream(storedFilePath(root, ref), {
+    highWaterMark: 1 << 16,
+    ...(signal === undefined ? {} : { signal }),
+  })
+  const hash = createHash('sha256')
+  let bytes = 0
+  try {
+    for await (const chunk of stream) {
+      signal?.throwIfAborted()
+      const data = chunk as Buffer
+      hash.update(data)
+      bytes += data.byteLength
+      yield data
+    }
+  } catch (error) {
+    signal?.throwIfAborted()
+    if (error instanceof Error && 'code' in error && error.code === 'ENOENT') {
+      throw new AttachmentError('File attachment object is missing.', 'ATTACHMENT_NOT_FOUND')
+    }
+    throw new AttachmentError('Unable to read file attachment.', 'ATTACHMENT_READ_FAILED', { cause: error })
+  } finally {
+    stream.destroy()
+  }
+  signal?.throwIfAborted()
+  if (bytes !== ref.bytes || hash.digest('hex') !== sha256) {
+    throw new AttachmentError('Stored file attachment failed integrity verification.', 'ATTACHMENT_CORRUPT')
+  }
+}
diff --git a/packages/attachment/attachment-local/src/index.ts b/packages/attachment/attachment-local/src/index.ts
index 16b963f225..7058fb3244 100644
--- a/packages/attachment/attachment-local/src/index.ts
+++ b/packages/attachment/attachment-local/src/index.ts
@@ -5,23 +5,32 @@ import { Context } from '@deepseek-ai/cordis'
 import z from '@deepseek-ai/schemastery'
 import { AttachmentStore } from '@deepseek-ai/dsh-attachment'
 import type {
+  FileAttachmentRef,
   ImageAttachmentLimits,
   ImageAttachmentRef,
   ImageRequestPolicy,
   RequestImageAttachment,
+  SaveFileAttachment,
+  SaveFileStreamAttachment,
   SaveImageAttachment,
   StoredImageAttachment,
 } from '@deepseek-ai/dsh-attachment'
 import { resolveDshHome } from '@deepseek-ai/dsh-home-paths'
 import type { NormalizationPolicy } from './normalization.ts'
-import { CompressionLimiter } from './compression-limiter.ts'
+import { CompressionLimiter, compressionFailure } from './compression-limiter.ts'
 import { commitPreparedImageFile, normalizedImagePath, prepareImageFile, readImageFile, validateImageFile } from './store.ts'
+import {
+  readFileStreamVerbatim, saveFileStreamVerbatim, saveFileVerbatim, storedFilePath,
+} from './file-store.ts'
 import { readRequestImageFile, requestImageVariantId } from './request-image.ts'
 
 export { canPassThroughNormalization, normalizeImage } from './normalization.ts'
 export type { NormalizedImage, NormalizationPolicy } from './normalization.ts'
 export { commitPreparedImageFile, prepareImageFile, readImageFile, saveImageFile, validateImageFile } from './store.ts'
 export type { PreparedImageFile } from './store.ts'
+export {
+  fileLeafName, readFileStreamVerbatim, saveFileStreamVerbatim, saveFileVerbatim, storedFilePath,
+} from './file-store.ts'
 export { readRequestImageFile, requestImageVariantId } from './request-image.ts'
 
 /** Default maximum encoded bytes for one submitted image; oversized sources are refused, not shrunk. */
@@ -124,9 +133,7 @@ class SharedRequest<T> {
       }, (error: unknown) => {
         signal.removeEventListener('abort', abort)
         release(false)
-        // CompressionLimiter normalizes task rejections before this handler.
-        // oxlint-disable-next-line typescript/prefer-promise-reject-errors
-        reject(error)
+        reject(compressionFailure(error))
       })
     })
   }
@@ -222,6 +229,22 @@ export class LocalAttachmentStore extends AttachmentStore {
     return normalizedImagePath(this.root, ref)
   }
 
+  override async saveFile(input: SaveFileAttachment): Promise<FileAttachmentRef> {
+    return saveFileVerbatim(this.root, input)
+  }
+
+  override async saveFileStream(input: SaveFileStreamAttachment): Promise<FileAttachmentRef> {
+    return saveFileStreamVerbatim(this.root, input)
+  }
+
+  override readFileStream(ref: FileAttachmentRef, signal?: AbortSignal): AsyncIterable<Uint8Array> {
+    return readFileStreamVerbatim(this.root, ref, signal)
+  }
+
+  override fileHostPath(ref: FileAttachmentRef): string {
+    return storedFilePath(this.root, ref)
+  }
+
   override async readImageRequest(
     ref: ImageAttachmentRef,
     policy: ImageRequestPolicy,
diff --git a/packages/attachment/attachment-local/src/store.ts b/packages/attachment/attachment-local/src/store.ts
index e5a979aec1..7fab679e34 100644
--- a/packages/attachment/attachment-local/src/store.ts
+++ b/packages/attachment/attachment-local/src/store.ts
@@ -1,7 +1,7 @@
 /** Content-addressed, owner-private local attachment storage. */
 
 import { createHash, randomUUID } from 'node:crypto'
-import { constants } from 'node:fs'
+import { constants, createReadStream } from 'node:fs'
 import { chmod, link, mkdir, open, readFile, unlink } from 'node:fs/promises'
 import { dirname, join, parse, resolve } from 'node:path'
 import {
@@ -197,60 +197,210 @@ export async function commitPreparedImageFile(
   if (digest(normalized) !== sha256 || normalized.byteLength !== prepared.ref.bytes) {
     throw new AttachmentError('Prepared attachment bytes do not match their reference.', 'ATTACHMENT_CORRUPT')
   }
-  const bucket = join(root, 'objects', sha256.slice(0, 2))
+  await publishImmutableObject(root, normalizedImagePath(root, prepared.ref), normalized, sha256)
+  return prepared.ref
+}
+
+/**
+ * Publish one immutable content-addressed object below a versioned attachment
+ * root: staged write, fsync, hard-link into place, digest-verified EEXIST
+ * deduplication, read-only mode, and durable directory entries from the
+ * target's parent up to (excluding) `root`.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param target - absolute final object path below `root`.
+ * @param data - exact object bytes whose digest is `sha256`.
+ * @param sha256 - hex digest the stored bytes must match on deduplication.
+ */
+export async function publishImmutableObject(
+  root: string,
+  target: string,
+  data: Uint8Array,
+  sha256: string,
+): Promise<void> {
+  const staged = await stageImmutableObject(root, (function* (): Iterable<Uint8Array> {
+    yield data
+  })())
+  if (staged.sha256 !== sha256) {
+    await removeTemporary(staged.path)
+    throw new AttachmentError('Attachment bytes do not match their publication digest.', 'ATTACHMENT_CORRUPT')
+  }
+  await publishStagedObject(root, target, staged)
+}
+
+/** Digest and byte count produced while streaming one immutable object to disk. */
+export interface StreamedImmutableObject {
+  readonly sha256: string
+  readonly bytes: number
+}
+
+/**
+ * Stream one immutable object from bounded chunks into a staging file, then
+ * publish it at a digest-derived target without collecting the complete object in memory.
+ * @param root - absolute `DSH_HOME/attachments/v1` root.
+ * @param data - exact object bytes in order.
+ * @param targetFor - derive the final absolute target from the completed digest and byte count.
+ * @param signal - optional cancellation for source reads and storage writes.
+ * @returns digest and exact byte count of the published object.
+ */
+export async function publishImmutableObjectStream(
+  root: string,
+  data: AsyncIterable<Uint8Array>,
+  targetFor: (sha256: string, bytes: number) => string,
+  signal?: AbortSignal,
+): Promise<StreamedImmutableObject> {
+  const staged = await stageImmutableObject(root, data, signal)
+  let target: string
+  try {
+    target = targetFor(staged.sha256, staged.bytes)
+  } catch (error) {
+    /* v8 ignore start -- The local target callback constructs a validated reference from this function's digest. */
+    await removeTemporary(staged.path)
+    throw error
+    /* v8 ignore stop */
+  }
+  await publishStagedObject(root, target, staged)
+  return { sha256: staged.sha256, bytes: staged.bytes }
+}
+
+/**
+ * Publish another durable hard-link name for an existing immutable object.
+ * @param root - absolute versioned attachment root.
+ * @param source - existing content-addressed object below `root`.
+ * @param target - new alias below `root`.
+ * @param sha256 - expected object digest for an existing-target race.
+ */
+export async function publishImmutableAlias(
+  root: string,
+  source: string,
+  target: string,
+  sha256: string,
+): Promise<void> {
+  const parent = dirname(target)
+  try {
+    const boundary = await ensureDurableHome(dirname(dirname(resolve(root))))
+    await ensureDurableDirectory(parent, boundary)
+    try {
+      await link(source, target)
+    } catch (error) {
+      /* v8 ignore next -- Private same-filesystem directories make EEXIST the only recoverable link race. */
+      if (!(error instanceof Error && 'code' in error && error.code === 'EEXIST')) throw error
+      if (await digestFile(target) !== sha256) {
+        throw new AttachmentError('Stored attachment failed integrity verification.', 'ATTACHMENT_CORRUPT')
+      }
+    }
+    await chmod(target, 0o400)
+    const stop = resolve(root)
+    for (let level = parent; level !== stop; level = dirname(level)) {
+      await syncDirectory(level)
+      /* v8 ignore next -- filesystem-root guard: targets sit below root, so the walk reaches `stop` first. */
+      if (dirname(level) === level) break
+    }
+  } catch (error) {
+    if (error instanceof AttachmentError) throw error
+    throw new AttachmentError('Unable to persist attachment.', 'ATTACHMENT_WRITE_FAILED', { cause: error })
+  }
+}
+
+interface StagedImmutableObject extends StreamedImmutableObject {
+  readonly path: string
+  readonly boundary: string
+}
+
+async function stageImmutableObject(
+  root: string,
+  data: AsyncIterable<Uint8Array> | Iterable<Uint8Array>,
+  signal?: AbortSignal,
+): Promise<StagedImmutableObject> {
   const staging = join(root, 'tmp')
   // Establish DSH_HOME itself against the filesystem root once per process.
   // Every process performs that proof independently, so observing a directory
   // another process created can never be mistaken for durable publication.
   const boundary = await ensureDurableHome(dirname(dirname(resolve(root))))
-  await ensureDurableDirectory(bucket, boundary)
   await ensureDurableDirectory(staging, boundary)
   const temporary = join(staging, randomUUID())
-  const target = normalizedImagePath(root, prepared.ref)
   let handle
   try {
     handle = await open(temporary, constants.O_CREAT | constants.O_EXCL | constants.O_WRONLY, 0o600)
-    await handle.writeFile(normalized)
+    const hash = createHash('sha256')
+    let bytes = 0
+    for await (const chunk of data) {
+      signal?.throwIfAborted()
+      await handle.writeFile(chunk)
+      hash.update(chunk)
+      bytes += chunk.byteLength
+    }
+    signal?.throwIfAborted()
     await handle.sync()
+    signal?.throwIfAborted()
     await handle.close()
     handle = undefined
-    try {
-      await link(temporary, target)
-    } catch (error) {
-      /* v8 ignore next -- Private same-filesystem directories make EEXIST the only recoverable link race. */
-      if (!(error instanceof Error && 'code' in error && error.code === 'EEXIST')) throw error
-      const existing = new Uint8Array(await readFile(target))
-      if (digest(existing) !== sha256) throw new AttachmentError('Stored attachment failed integrity verification.', 'ATTACHMENT_CORRUPT')
-    }
-    // Windows shares the read-only attribute across hard links and refuses to
-    // unlink either name once it is set, so discard the staging name first.
-    await unlink(temporary)
-    // The target remains the sole link for a new object; this also restores
-    // read-only mode when the deduplication path observes an existing object.
-    await chmod(target, 0o400)
-    // Persist the target entry and close a concurrent bucket-creation window
-    // before the reference can reach a session checkpoint. The dedup path
-    // repeats both syncs because it may observe another writer's link before
-    // that writer reaches its own durability boundary.
-    await syncDirectory(bucket)
-    await syncDirectory(join(root, 'objects'))
+    return { path: temporary, boundary, sha256: hash.digest('hex'), bytes }
   } catch (error) {
-    /* v8 ignore next -- A descriptor can remain open only when the underlying write/sync/close operation fails. */
+    /* v8 ignore next -- A descriptor remains open only when write, sync, or close fails. */
     if (handle !== undefined) await handle.close().catch(
       /* v8 ignore next -- Close failure is superseded by the storage operation that entered cleanup. */
       () => {},
     )
-    await unlink(temporary).catch(
-      /* v8 ignore next -- The callback requires a second independent staging-unlink failure. */
-      (cleanupError: unknown) => {
-        /* v8 ignore next -- Cleanup is best-effort only for a staging file already removed by a failed operation. */
-        if (!(cleanupError instanceof Error && 'code' in cleanupError && cleanupError.code === 'ENOENT')) throw cleanupError
-      },
-    )
-    if (error instanceof AttachmentError) throw error
-    throw new AttachmentError('Unable to persist image attachment.', 'ATTACHMENT_WRITE_FAILED', { cause: error })
+    await removeTemporary(temporary)
+    if (error instanceof AttachmentError || signal?.aborted === true) throw error
+    throw new AttachmentError('Unable to persist attachment.', 'ATTACHMENT_WRITE_FAILED', { cause: error })
   }
-  return prepared.ref
+}
+
+async function publishStagedObject(
+  root: string,
+  target: string,
+  staged: StagedImmutableObject,
+): Promise<void> {
+  const parent = dirname(target)
+  try {
+    await ensureDurableDirectory(parent, staged.boundary)
+    try {
+      await link(staged.path, target)
+    } catch (error) {
+      /* v8 ignore next -- Private same-filesystem directories make EEXIST the only recoverable link race. */
+      if (!(error instanceof Error && 'code' in error && error.code === 'EEXIST')) throw error
+      if (await digestFile(target) !== staged.sha256) {
+        throw new AttachmentError('Stored attachment failed integrity verification.', 'ATTACHMENT_CORRUPT')
+      }
+    }
+    // Windows shares the read-only attribute across hard links and refuses to
+    // unlink either name once it is set, so discard the staging name first.
+    await unlink(staged.path)
+    // The target remains the sole link for a new object; this also restores
+    // read-only mode when the deduplication path observes an existing object.
+    await chmod(target, 0o400)
+    // Persist the target entry and close every concurrent parent-creation
+    // window before the reference can reach a session checkpoint. The dedup
+    // path repeats these syncs because it may observe another writer's link
+    // before that writer reaches its own durability boundary.
+    const stop = resolve(root)
+    for (let level = parent; level !== stop; level = dirname(level)) {
+      await syncDirectory(level)
+      /* v8 ignore next -- filesystem-root guard: targets sit below root, so the walk reaches `stop` first. */
+      if (dirname(level) === level) break
+    }
+  } catch (error) {
+    await removeTemporary(staged.path)
+    if (error instanceof AttachmentError) throw error
+    throw new AttachmentError('Unable to persist attachment.', 'ATTACHMENT_WRITE_FAILED', { cause: error })
+  }
+}
+
+async function digestFile(path: string): Promise<string> {
+  const hash = createHash('sha256')
+  for await (const chunk of createReadStream(path) as AsyncIterable<Buffer>) hash.update(chunk)
+  return hash.digest('hex')
+}
+
+async function removeTemporary(path: string): Promise<void> {
+  await unlink(path).catch(
+    /* v8 ignore next -- Cleanup can observe a staging name already removed after successful linking. */
+    (cleanupError: unknown) => {
+      /* v8 ignore next -- Any cleanup failure except an absent staging name must remain visible. */
+      if (!(cleanupError instanceof Error && 'code' in cleanupError && cleanupError.code === 'ENOENT')) throw cleanupError
+    },
+  )
 }
 
 /**
diff --git a/packages/attachment/attachment-local/tests/file-store.spec.ts b/packages/attachment/attachment-local/tests/file-store.spec.ts
new file mode 100644
index 0000000000..dde6ec2d06
--- /dev/null
+++ b/packages/attachment/attachment-local/tests/file-store.spec.ts
@@ -0,0 +1,278 @@
+import { createHash } from 'node:crypto'
+import { chmod, mkdir, readdir, readFile, stat, unlink, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { mkdtemp, rm } from 'node:fs/promises'
+import { afterEach, describe, expect, it } from 'vitest'
+import { AttachmentId } from '@deepseek-ai/dsh-attachment'
+import type { FileAttachmentRef } from '@deepseek-ai/dsh-attachment'
+import {
+  fileLeafName, readFileStreamVerbatim, saveFileStreamVerbatim, saveFileVerbatim, storedFilePath,
+} from '../src/file-store.ts'
+import { publishImmutableAlias } from '../src/store.ts'
+
+const roots: string[] = []
+
+async function makeRoot(): Promise<string> {
+  const root = join(await mkdtemp(join(tmpdir(), 'dsh-file-store-')), 'attachments', 'v1')
+  roots.push(root)
+  return root
+}
+
+afterEach(async () => {
+  for (const root of roots.splice(0)) {
+    await rm(join(root, '..', '..'), { recursive: true, force: true, maxRetries: 3 })
+  }
+})
+
+function sha256(data: Uint8Array): string {
+  return createHash('sha256').update(data).digest('hex')
+}
+
+async function readStream(stream: AsyncIterable<Uint8Array>): Promise<Uint8Array> {
+  const chunks: Uint8Array[] = []
+  for await (const chunk of stream) chunks.push(chunk)
+  return new Uint8Array(Buffer.concat(chunks))
+}
+
+describe('fileLeafName', () => {
+  it('keeps ordinary names and strips client paths of both separator styles', () => {
+    expect(fileLeafName('notes.pdf')).toBe('notes.pdf')
+    expect(fileLeafName('/home/user/data.csv')).toBe('data.csv')
+    expect(fileLeafName('C:\\Users\\me\\report.docx')).toBe('report.docx')
+  })
+
+  it('removes control characters, rewrites Windows-invalid characters, and bounds UTF-8 length', () => {
+    expect(fileLeafName('a\u0000b\u001f.txt')).toBe('ab.txt')
+    expect(fileLeafName('a<b>c:d"e|f?g*h.txt')).toBe('a_b_c_d_e_f_g_h.txt')
+    expect(fileLeafName(`${'x'.repeat(300)}.bin`).length).toBe(255)
+    const multibyte = fileLeafName(`${'文'.repeat(100)}.txt`)
+    expect(Buffer.byteLength(multibyte)).toBeLessThanOrEqual(255)
+    expect(multibyte.endsWith('\ufffd')).toBe(false)
+    expect(fileLeafName(`safe-${'x'.repeat(248)}\ud83d\ude00`)).not.toMatch(/\ud83d$/u)
+  })
+
+  it('removes Windows trailing characters and protects reserved device names', () => {
+    expect(fileLeafName('report. ')).toBe('report')
+    expect(fileLeafName('CON')).toBe('_CON')
+    expect(fileLeafName('com1.txt')).toBe('_com1.txt')
+    expect(fileLeafName('con .txt')).toBe('_con .txt')
+    expect(fileLeafName('com10.txt')).toBe('com10.txt')
+  })
+
+  it('falls back to a stable name for absent, empty, and dot-only inputs', () => {
+    expect(fileLeafName(undefined)).toBe('file')
+    expect(fileLeafName('')).toBe('file')
+    expect(fileLeafName('   ')).toBe('file')
+    expect(fileLeafName('.')).toBe('file')
+    expect(fileLeafName('..')).toBe('file')
+  })
+})
+
+describe('saveFileVerbatim', () => {
+  it('stores the exact bytes read-only at a digest-and-name path', async () => {
+    const root = await makeRoot()
+    const data = Uint8Array.from([0, 1, 2, 250, 251, 252])
+    const ref = await saveFileVerbatim(root, { data, name: 'blob.bin' })
+    expect(ref).toEqual({
+      attachmentId: AttachmentId(`sha256:${sha256(data)}`),
+      name: 'blob.bin',
+      bytes: data.byteLength,
+    })
+    const path = storedFilePath(root, ref)
+    expect(path.endsWith(join(sha256(data), 'blob.bin'))).toBe(true)
+    expect(new Uint8Array(await readFile(path))).toEqual(data)
+    if (process.platform !== 'win32') {
+      expect((await stat(path)).mode & 0o777).toBe(0o400)
+    }
+  })
+
+  it('accepts a zero-byte file', async () => {
+    const root = await makeRoot()
+    const ref = await saveFileVerbatim(root, { data: new Uint8Array(0), name: 'empty.txt' })
+    expect(ref.bytes).toBe(0)
+    expect((await readFile(storedFilePath(root, ref))).byteLength).toBe(0)
+  })
+
+  it('stores sanitized Windows-reserved and multibyte names', async () => {
+    const root = await makeRoot()
+    const reserved = await saveFileVerbatim(root, { data: new Uint8Array(0), name: 'NUL.txt' })
+    const multibyte = await saveFileVerbatim(root, { data: Uint8Array.of(1), name: '文'.repeat(100) })
+    expect(reserved.name).toBe('_NUL.txt')
+    expect(Buffer.byteLength(multibyte.name)).toBeLessThanOrEqual(255)
+    await expect(readFile(storedFilePath(root, reserved))).resolves.toHaveLength(0)
+    await expect(readFile(storedFilePath(root, multibyte))).resolves.toEqual(Buffer.from([1]))
+  })
+
+  it('deduplicates identical bytes and stores distinct names beside one digest', async () => {
+    const root = await makeRoot()
+    const data = Uint8Array.from([7, 7, 7])
+    const first = await saveFileVerbatim(root, { data, name: 'a.txt' })
+    const again = await saveFileVerbatim(root, { data, name: 'a.txt' })
+    expect(again).toEqual(first)
+    const renamed = await saveFileVerbatim(root, { data, name: 'b.txt' })
+    expect(renamed.attachmentId).toBe(first.attachmentId)
+    expect((await stat(storedFilePath(root, first))).ino)
+      .toBe((await stat(storedFilePath(root, renamed))).ino)
+    const digestDir = join(root, 'files', sha256(data).slice(0, 2), sha256(data))
+    expect((await readdir(digestDir)).sort()).toEqual(['a.txt', 'b.txt'])
+  })
+
+  it('refuses a stored object whose bytes no longer match the digest', async () => {
+    const root = await makeRoot()
+    const data = Uint8Array.from([1, 2, 3])
+    const ref = await saveFileVerbatim(root, { data, name: 'c.txt' })
+    const path = storedFilePath(root, ref)
+    await chmod(path, 0o600)
+    await writeFile(path, Uint8Array.from([9, 9, 9]))
+    await expect(saveFileVerbatim(root, { data, name: 'c.txt' }))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_CORRUPT' })
+  })
+
+  it('rejects a conflicting display-name alias and wraps alias publication failures', async () => {
+    const root = await makeRoot()
+    const data = Uint8Array.of(1, 2, 3)
+    const ref = await saveFileVerbatim(root, { data, name: 'alias.bin' })
+    const alias = storedFilePath(root, ref)
+    await unlink(alias)
+    await writeFile(alias, Uint8Array.of(9, 9, 9))
+    await expect(saveFileVerbatim(root, { data, name: 'alias.bin' }))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_CORRUPT' })
+
+    await expect(publishImmutableAlias(
+      root,
+      join(root, 'missing-object'),
+      join(root, 'files', 'ff', 'missing', 'alias.bin'),
+      'f'.repeat(64),
+    )).rejects.toMatchObject({ code: 'ATTACHMENT_WRITE_FAILED' })
+  })
+})
+
+describe('saveFileStreamVerbatim', () => {
+  it('stores ordered chunks without materializing one aggregate byte array', async () => {
+    const root = await makeRoot()
+    const ref = await saveFileStreamVerbatim(root, {
+      data: (async function* (): AsyncIterable<Uint8Array> {
+        yield Uint8Array.of(0, 1)
+        yield Uint8Array.of(2, 250)
+        yield Uint8Array.of(251, 252)
+      })(),
+      name: 'large.bin',
+    })
+    const expected = Uint8Array.of(0, 1, 2, 250, 251, 252)
+    expect(ref).toEqual({
+      attachmentId: AttachmentId(`sha256:${sha256(expected)}`),
+      name: 'large.bin',
+      bytes: expected.byteLength,
+    })
+    expect(new Uint8Array(await readFile(storedFilePath(root, ref)))).toEqual(expected)
+  })
+
+  it('removes its staging file when cancellation interrupts the source', async () => {
+    const root = await makeRoot()
+    const abort = new AbortController()
+    const reason = new Error('upload cancelled')
+    await expect(saveFileStreamVerbatim(root, {
+      data: (async function* (): AsyncIterable<Uint8Array> {
+        yield Uint8Array.of(1, 2)
+        abort.abort(reason)
+        yield Uint8Array.of(3, 4)
+      })(),
+      signal: abort.signal,
+      name: 'cancelled.bin',
+    })).rejects.toBe(reason)
+    expect(await readdir(join(root, 'tmp'))).toEqual([])
+  })
+
+  it('wraps source failures and removes the staging file', async () => {
+    const root = await makeRoot()
+    await expect(saveFileStreamVerbatim(root, {
+      data: (async function* (): AsyncIterable<Uint8Array> {
+        yield Uint8Array.of(1, 2)
+        throw new Error('source failed')
+      })(),
+      name: 'failed.bin',
+    })).rejects.toMatchObject({ code: 'ATTACHMENT_WRITE_FAILED' })
+    expect(await readdir(join(root, 'tmp'))).toEqual([])
+  })
+})
+
+describe('readFileStreamVerbatim', () => {
+  it('returns exact bounded chunks and accepts an empty file', async () => {
+    const root = await makeRoot()
+    const data = Uint8Array.from({ length: (1 << 16) + 3 }, (_, index) => index % 251)
+    const ref = await saveFileVerbatim(root, { data, name: 'large.bin' })
+    await expect(readStream(readFileStreamVerbatim(root, ref))).resolves.toEqual(data)
+    const empty = await saveFileVerbatim(root, { data: new Uint8Array(), name: 'empty.bin' })
+    await expect(readStream(readFileStreamVerbatim(root, empty))).resolves.toEqual(new Uint8Array())
+  })
+
+  it('rejects invalid, missing, and unreadable references with storage codes', async () => {
+    const root = await makeRoot()
+    const ref: FileAttachmentRef = {
+      attachmentId: AttachmentId(`sha256:${'c'.repeat(64)}`),
+      name: 'missing.bin',
+      bytes: 1,
+    }
+    await expect(readStream(readFileStreamVerbatim(root, { ...ref, name: '../escape' })))
+      .rejects.toMatchObject({ code: 'INVALID_ATTACHMENT_REF' })
+    await expect(readStream(readFileStreamVerbatim(root, ref)))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_NOT_FOUND' })
+
+    const saved = await saveFileVerbatim(root, { data: Uint8Array.of(1), name: 'unreadable.bin' })
+    const path = storedFilePath(root, saved)
+    await unlink(path)
+    await mkdir(path)
+    await expect(readStream(readFileStreamVerbatim(root, saved)))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_READ_FAILED' })
+  })
+
+  it('detects changed bytes and recorded lengths', async () => {
+    const root = await makeRoot()
+    const ref = await saveFileVerbatim(root, { data: Uint8Array.of(1, 2, 3), name: 'data.bin' })
+    const path = storedFilePath(root, ref)
+    await chmod(path, 0o600)
+    await writeFile(path, Uint8Array.of(3, 2, 1))
+    await expect(readStream(readFileStreamVerbatim(root, ref)))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_CORRUPT' })
+    await writeFile(path, Uint8Array.of(1, 2, 3))
+    await expect(readStream(readFileStreamVerbatim(root, { ...ref, bytes: 4 })))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_CORRUPT' })
+  })
+
+  it('preserves caller cancellation before and during a read', async () => {
+    const root = await makeRoot()
+    const ref = await saveFileVerbatim(root, {
+      data: Uint8Array.from({ length: 1 << 17 }, () => 7),
+      name: 'cancel.bin',
+    })
+    const before = new AbortController()
+    const beforeReason = new Error('cancelled before read')
+    before.abort(beforeReason)
+    await expect(readStream(readFileStreamVerbatim(root, ref, before.signal))).rejects.toBe(beforeReason)
+
+    const during = new AbortController()
+    const stream = readFileStreamVerbatim(root, ref, during.signal)[Symbol.asyncIterator]()
+    await expect(stream.next()).resolves.toMatchObject({ done: false })
+    const duringReason = new Error('cancelled during read')
+    during.abort(duringReason)
+    await expect(stream.next()).rejects.toBe(duringReason)
+  })
+})
+
+describe('storedFilePath', () => {
+  it('rejects malformed digests and unsanitized names before deriving a path', () => {
+    const good: FileAttachmentRef = {
+      attachmentId: AttachmentId(`sha256:${'a'.repeat(64)}`),
+      name: 'ok.txt',
+      bytes: 1,
+    }
+    expect(() => storedFilePath('/root', { ...good, attachmentId: AttachmentId('sha256:short') }))
+      .toThrow(expect.objectContaining({ code: 'INVALID_ATTACHMENT_REF' }) as Error)
+    expect(() => storedFilePath('/root', { ...good, name: '../escape.txt' }))
+      .toThrow(expect.objectContaining({ code: 'INVALID_ATTACHMENT_REF' }) as Error)
+    expect(() => storedFilePath('/root', { ...good, name: 'nested/name.txt' }))
+      .toThrow(expect.objectContaining({ code: 'INVALID_ATTACHMENT_REF' }) as Error)
+    expect(storedFilePath('/root', good).endsWith(join('a'.repeat(64), 'ok.txt'))).toBe(true)
+  })
+})
diff --git a/packages/attachment/attachment-local/tests/index.spec.ts b/packages/attachment/attachment-local/tests/index.spec.ts
index 4d9d9f350b..5711c6d35d 100644
--- a/packages/attachment/attachment-local/tests/index.spec.ts
+++ b/packages/attachment/attachment-local/tests/index.spec.ts
@@ -87,6 +87,21 @@ describe('local attachment service', () => {
       await expect(readFile(hostPath)).resolves.toEqual(Buffer.from(data))
       const request = await service.readImageRequest(ref, { maxPixels: 1, maxBytes: 1024 })
       expect(request).not.toHaveProperty('access')
+
+      const fileData = Uint8Array.of(0, 1, 2, 255)
+      const fileRef = await service.saveFile({ data: fileData, name: 'notes.bin' })
+      const filePath = service.fileHostPath(fileRef)
+      expect(filePath).toContain(join('files', String(fileRef.attachmentId).slice(7, 9)))
+      await expect(readFile(filePath)).resolves.toEqual(Buffer.from(fileData))
+
+      const streamRef = await service.saveFileStream({
+        data: (async function* (): AsyncIterable<Uint8Array> { yield fileData })(),
+        name: 'stream.bin',
+      })
+      await expect(readFile(service.fileHostPath(streamRef))).resolves.toEqual(Buffer.from(fileData))
+      const streamed: Uint8Array[] = []
+      for await (const chunk of service.readFileStream(streamRef)) streamed.push(chunk)
+      expect(Buffer.concat(streamed)).toEqual(Buffer.from(fileData))
     } finally {
       await rm(dshHome, { recursive: true, force: true })
     }
diff --git a/packages/attachment/attachment-local/tests/store.spec.ts b/packages/attachment/attachment-local/tests/store.spec.ts
index 3ff58eb2da..82c2b9f3ba 100644
--- a/packages/attachment/attachment-local/tests/store.spec.ts
+++ b/packages/attachment/attachment-local/tests/store.spec.ts
@@ -1,6 +1,6 @@
 import { createHash } from 'node:crypto'
 import { constants } from 'node:fs'
-import { chmod, mkdir, readFile, stat, writeFile } from 'node:fs/promises'
+import { chmod, mkdir, readFile, readdir, stat, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { dirname, join, parse, resolve } from 'node:path'
 import { mkdtemp, rm } from 'node:fs/promises'
@@ -8,7 +8,13 @@ import { afterEach, describe, expect, it, vi } from 'vitest'
 import sharp from 'sharp'
 import type { ImageAttachmentLimits } from '@deepseek-ai/dsh-attachment'
 import type { NormalizationPolicy } from '../src/normalization.ts'
-import { commitPreparedImageFile, prepareImageFile, readImageFile, saveImageFile } from '../src/store.ts'
+import {
+  commitPreparedImageFile,
+  prepareImageFile,
+  publishImmutableObject,
+  readImageFile,
+  saveImageFile,
+} from '../src/store.ts'
 
 const fsControl = vi.hoisted(() => ({
   readSignals: [] as AbortSignal[],
@@ -89,12 +95,13 @@ describe('local attachment store', () => {
     // Later directory creation can then stop at that process-proven boundary.
     expect(fsControl.syncedDirectories).toEqual([
       ...parentChainToRoot(base),
-      // bucket chain: every parent entry between the bucket and the boundary.
-      objects,
+      // Staging precedes publication because the streamed digest selects the
+      // target bucket only after every byte has been written.
       storageRoot,
       join(storageRoot, '..'),
       base,
-      // staging chain re-walks the shared ancestors after creating tmp.
+      // bucket chain: every parent entry between the bucket and the boundary.
+      objects,
       storageRoot,
       join(storageRoot, '..'),
       base,
@@ -141,6 +148,14 @@ describe('local attachment store', () => {
     await expect(readImageFile(storageRoot, first)).resolves.toEqual({ ref: first, data: PNG })
   })
 
+  it('rejects publication when the supplied digest does not match the staged bytes', async () => {
+    const storageRoot = await root()
+    const target = join(storageRoot, 'objects', '00', 'mismatch')
+    await expect(publishImmutableObject(storageRoot, target, Uint8Array.of(1), '0'.repeat(64)))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_CORRUPT' })
+    expect(await readdir(join(storageRoot, 'tmp'))).toEqual([])
+  })
+
   it.skipIf(process.platform !== 'win32')('publishes a new object on Windows', async () => {
     const storageRoot = await root()
 
diff --git a/packages/attachment/attachment/src/admission.ts b/packages/attachment/attachment/src/admission.ts
index 155b3644d8..a3f5f16c8c 100644
--- a/packages/attachment/attachment/src/admission.ts
+++ b/packages/attachment/attachment/src/admission.ts
@@ -5,21 +5,30 @@ import { AttachmentError } from './error.ts'
 import type { AttachmentStore } from './index.ts'
 import type {
   AdmittedPromptContentPart,
+  EncodedFileAttachment,
   EncodedImageAttachment,
+  FileAttachmentRef,
   ImageAttachmentRef,
   PromptContentPart,
   SaveImageAttachment,
 } from './types.ts'
 
 /** Decode one upload payload while rejecting non-canonical base64 forms. */
-function decodeBase64(data: string): Uint8Array {
+function decodeCanonicalBase64(data: string, empty: 'reject' | 'accept', code: 'INVALID_IMAGE_BASE64' | 'INVALID_FILE_BASE64'): Uint8Array {
   const decoded = Buffer.from(data, 'base64')
-  if (data.length === 0 || decoded.toString('base64') !== data) {
-    throw new AttachmentError('Image upload is not canonical base64.', 'INVALID_IMAGE_BASE64')
+  if ((data.length === 0 && empty === 'reject') || decoded.toString('base64') !== data) {
+    throw new AttachmentError(
+      code === 'INVALID_IMAGE_BASE64' ? 'Image upload is not canonical base64.' : 'File upload is not canonical base64.',
+      code,
+    )
   }
   return new Uint8Array(decoded)
 }
 
+function decodeBase64(data: string): Uint8Array {
+  return decodeCanonicalBase64(data, 'reject', 'INVALID_IMAGE_BASE64')
+}
+
 /** Store input for one decoded upload. */
 function saveInput(image: EncodedImageAttachment): SaveImageAttachment {
   return {
@@ -46,6 +55,26 @@ export async function admitEncodedImages(
   return attachments.saveImages(images.map(saveInput))
 }
 
+/**
+ * Admit one wire file upload: enforce canonical base64 (an empty file is a
+ * valid zero-byte payload), then delegate verbatim commit to
+ * {@link AttachmentStore.saveFile}. The shared entry for every RPC endpoint
+ * accepting browser file uploads.
+ * @param attachments - the deployment attachment store.
+ * @param file - base64-encoded upload and optional display name.
+ * @returns the durable content-addressed file reference.
+ * @throws AttachmentError on a non-canonical payload or a storage failure.
+ */
+export async function admitEncodedFile(
+  attachments: AttachmentStore,
+  file: EncodedFileAttachment,
+): Promise<FileAttachmentRef> {
+  return attachments.saveFile({
+    data: decodeCanonicalBase64(file.data, 'accept', 'INVALID_FILE_BASE64'),
+    ...file.name === undefined ? {} : { name: file.name },
+  })
+}
+
 /**
  * Admit one browser prompt and replace each uploaded image with its durable reference.
  * Text-only prompts do not access the attachment store.
diff --git a/packages/attachment/attachment/src/error.ts b/packages/attachment/attachment/src/error.ts
index c19229872b..7a1588b55e 100644
--- a/packages/attachment/attachment/src/error.ts
+++ b/packages/attachment/attachment/src/error.ts
@@ -18,12 +18,14 @@ export type ImageAdmissionErrorCode = typeof IMAGE_ADMISSION_ERROR_CODES[number]
 /** Stable attachment failure codes used for protocol error routing. */
 export type AttachmentErrorCode =
   | ImageAdmissionErrorCode
+  | 'INVALID_FILE_BASE64'
   | 'INVALID_ATTACHMENT_REF'
   | 'ATTACHMENT_CORRUPT'
   | 'ATTACHMENT_WRITE_FAILED'
   | 'ATTACHMENT_NOT_FOUND'
   | 'ATTACHMENT_READ_FAILED'
   | 'ATTACHMENT_PROJECTION_UNSUPPORTED'
+  | 'ATTACHMENT_FILES_UNSUPPORTED'
 
 /** Runtime membership for structurally compatible errors crossing package boundaries. */
 const IMAGE_ADMISSION_ERROR_CODE_SET: ReadonlySet<string> = new Set(IMAGE_ADMISSION_ERROR_CODES)
diff --git a/packages/attachment/attachment/src/index.ts b/packages/attachment/attachment/src/index.ts
index 9dcddeae65..8ae640c947 100644
--- a/packages/attachment/attachment/src/index.ts
+++ b/packages/attachment/attachment/src/index.ts
@@ -3,10 +3,13 @@
 import { Context, Service } from '@deepseek-ai/cordis'
 import { AttachmentError } from './error.ts'
 import type {
+  FileAttachmentRef,
   ImageAttachmentLimits,
   ImageAttachmentRef,
   ImageRequestPolicy,
   RequestImageAttachment,
+  SaveFileAttachment,
+  SaveFileStreamAttachment,
   SaveImageAttachment,
   StoredImageAttachment,
 } from './types.ts'
@@ -14,18 +17,22 @@ import type {
 export { AttachmentId, ImageVariantId } from './brand.ts'
 export { AttachmentError, isImageAdmissionError } from './error.ts'
 export type { AttachmentErrorCode, ImageAdmissionErrorCode } from './error.ts'
-export { admitEncodedImages, admitPromptContent } from './admission.ts'
+export { admitEncodedFile, admitEncodedImages, admitPromptContent } from './admission.ts'
 export { requestImageDimensions } from './request-projection.ts'
 export type {
   AttachmentId as AttachmentIdType,
   AdmittedPromptContentPart,
+  EncodedFileAttachment,
   EncodedImageAttachment,
+  FileAttachmentRef,
   ImageAttachmentLimits,
   ImageAttachmentRef,
   ImageRequestPolicy,
   ImageMediaType,
   PromptContentPart,
   RequestImageAttachment,
+  SaveFileAttachment,
+  SaveFileStreamAttachment,
   SaveImageAttachment,
   StoredImageAttachment,
 } from './types.ts'
@@ -121,6 +128,68 @@ export abstract class AttachmentStore extends Service {
     return undefined
   }
 
+  /**
+   * Durably commit one file byte-for-byte before its owning session event is
+   * appended. Files carry no admission limits: any byte content and length is
+   * accepted, and the stored object is the exact submitted bytes. Backends
+   * without verbatim file storage keep this default rejection.
+   * @param input - exact bytes and optional display name.
+   * @returns the durable content-addressed file reference.
+   */
+  saveFile(input: SaveFileAttachment): Promise<FileAttachmentRef> {
+    void input
+    return Promise.reject(new AttachmentError(
+      'The mounted attachment provider cannot store verbatim files.',
+      'ATTACHMENT_FILES_UNSUPPORTED',
+    ))
+  }
+
+  /**
+   * Durably commit one file byte-for-byte from bounded chunks. Providers must
+   * apply backpressure and must not collect the complete file in memory.
+   * Backends without streamed verbatim storage keep this default rejection.
+   * @param input - ordered exact bytes, optional cancellation, and display name.
+   * @returns the durable content-addressed file reference.
+   */
+  saveFileStream(input: SaveFileStreamAttachment): Promise<FileAttachmentRef> {
+    void input
+    return Promise.reject(new AttachmentError(
+      'The mounted attachment provider cannot stream verbatim files.',
+      'ATTACHMENT_FILES_UNSUPPORTED',
+    ))
+  }
+
+  /**
+   * Read and verify one verbatim stored file as bounded chunks. Providers must
+   * not collect the complete file in memory. Backends without verbatim file
+   * reads keep this default rejection.
+   * @param ref - durable reference from the session log.
+   * @param signal - optional cancellation for backend reads and verification work.
+   * @returns exact file bytes in order; integrity failures reject the iteration.
+   */
+  async *readFileStream(
+    ref: FileAttachmentRef,
+    signal?: AbortSignal,
+  ): AsyncIterable<Uint8Array> {
+    signal?.throwIfAborted()
+    void ref
+    await Promise.reject(new AttachmentError(
+      'The mounted attachment provider cannot read verbatim files.',
+      'ATTACHMENT_FILES_UNSUPPORTED',
+    ))
+  }
+
+  /**
+   * Locate the verbatim stored file object in the harness host filesystem.
+   * @param ref - durable file reference.
+   * @returns an absolute host path, or undefined when this backend is not host-file-backed.
+   * @throws an AttachmentError when the durable reference is invalid.
+   */
+  fileHostPath(ref: FileAttachmentRef): string | undefined {
+    void ref
+    return undefined
+  }
+
   /**
    * Generate or read one deterministic model-request version from the stored normalized image.
    * @param ref - durable provider-independent normalized attachment reference.
diff --git a/packages/attachment/attachment/src/types.ts b/packages/attachment/attachment/src/types.ts
index 7a55c6a68f..03fb45c761 100644
--- a/packages/attachment/attachment/src/types.ts
+++ b/packages/attachment/attachment/src/types.ts
@@ -31,6 +31,45 @@ export interface ImageAttachmentRef {
   }
 }
 
+/**
+ * Durable, serializable reference to one verbatim stored file. Files are
+ * stored byte-for-byte with no normalization; `attachmentId` is the sha256
+ * digest of exactly those bytes.
+ */
+export interface FileAttachmentRef {
+  /** Opaque content-addressed storage identifier; never a filesystem path or bearer URL. */
+  attachmentId: AttachmentId
+  /** Sanitized display filename, also the stored object's leaf name. */
+  name: string
+  /** Exact byte length. */
+  bytes: number
+}
+
+/** Base64-encoded file upload accompanying one wire request. */
+export interface EncodedFileAttachment {
+  /** Canonical base64 encoding of the file bytes. */
+  data: string
+  /** Optional display name; it is never interpreted as a path. */
+  name?: string
+}
+
+/** Request to durably commit one file verbatim. */
+export interface SaveFileAttachment {
+  data: Uint8Array
+  /** Optional browser/provider display name; it is never interpreted as a path. */
+  name?: string
+}
+
+/** Request to durably commit one file from bounded byte chunks. */
+export interface SaveFileStreamAttachment {
+  /** Exact file bytes in order; providers must not retain the complete sequence in memory. */
+  data: AsyncIterable<Uint8Array>
+  /** Optional cancellation for source reads and storage writes. */
+  signal?: AbortSignal
+  /** Optional browser/provider display name; it is never interpreted as a path. */
+  name?: string
+}
+
 /** Deployment-resolved limits used by upload admission and request buffering. */
 export interface ImageAttachmentLimits {
   maxImageBytes: number
diff --git a/packages/attachment/attachment/tests/admission.spec.ts b/packages/attachment/attachment/tests/admission.spec.ts
index ba24d8fa20..60eadd421f 100644
--- a/packages/attachment/attachment/tests/admission.spec.ts
+++ b/packages/attachment/attachment/tests/admission.spec.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it, vi } from 'vitest'
 import type { AttachmentStore } from '@deepseek-ai/dsh-attachment'
-import { admitEncodedImages, admitPromptContent } from '@deepseek-ai/dsh-attachment'
+import { admitEncodedFile, admitEncodedImages, admitPromptContent } from '@deepseek-ai/dsh-attachment'
 import type { ImageAttachmentRef, SaveImageAttachment } from '@deepseek-ai/dsh-attachment/types'
 
 const PNG = 'AAAA' // canonical base64, 3 bytes
@@ -65,6 +65,44 @@ describe('admitEncodedImages', () => {
   })
 })
 
+describe('admitEncodedFile', () => {
+  /** Delegation double: records the exact saveFile input and answers a fixed ref. */
+  function fileStoreOf() {
+    const store = {
+      saveFile: vi.fn((input: { data: Uint8Array; name?: string }) => Promise.resolve({
+        attachmentId: 'file-1' as never,
+        name: input.name ?? 'file',
+        bytes: input.data.byteLength,
+      })),
+    }
+    return { store: store as unknown as AttachmentStore, mocks: store }
+  }
+
+  it('decodes canonical base64 and delegates verbatim commit to saveFile', async () => {
+    const { store, mocks } = fileStoreOf()
+    const ref = await admitEncodedFile(store, { data: 'AAAA', name: 'blob.bin' })
+    expect(mocks.saveFile).toHaveBeenCalledTimes(1)
+    const input = mocks.saveFile.mock.calls[0]?.[0] as { data: Uint8Array; name?: string }
+    expect([input.name, input.data.byteLength]).toEqual(['blob.bin', 3])
+    expect(ref.bytes).toBe(3)
+  })
+
+  it('accepts an empty payload as a zero-byte file and omits an absent name', async () => {
+    const { store, mocks } = fileStoreOf()
+    const ref = await admitEncodedFile(store, { data: '' })
+    const input = mocks.saveFile.mock.calls[0]?.[0] as object
+    expect('name' in input).toBe(false)
+    expect(ref.bytes).toBe(0)
+  })
+
+  it('rejects non-canonical base64 without touching the store', async () => {
+    const { store, mocks } = fileStoreOf()
+    await expect(admitEncodedFile(store, { data: 'not base64!!' }))
+      .rejects.toMatchObject({ code: 'INVALID_FILE_BASE64' })
+    expect(mocks.saveFile).not.toHaveBeenCalled()
+  })
+})
+
 describe('admitPromptContent', () => {
   it('converts text-only prompts without touching the attachment store', async () => {
     const store = { saveImages: () => { throw new Error('text-only prompts must not reach the store') } }
diff --git a/packages/attachment/attachment/tests/index.spec.ts b/packages/attachment/attachment/tests/index.spec.ts
index 8675d45404..fcccd60b6e 100644
--- a/packages/attachment/attachment/tests/index.spec.ts
+++ b/packages/attachment/attachment/tests/index.spec.ts
@@ -147,10 +147,33 @@ describe('AttachmentStore.readImageRequest', () => {
     expect(() => store.readImageRequest(ref, { maxPixels: 1, maxBytes: 1 }, controller.signal)).toThrow(reason)
   })
 
-  it('exposes no provider-owned host path by default', async () => {
+  it('rejects generic-file storage and exposes no provider-owned host path by default', async () => {
     const store = new RecordingStore(new Context())
     const ref = await store.saveImage(image(1))
     expect(store.imageHostPath(ref)).toBeUndefined()
+    await expect(store.saveFile({ data: Uint8Array.of(1), name: 'notes.txt' }))
+      .rejects.toMatchObject({ code: 'ATTACHMENT_FILES_UNSUPPORTED' })
+    await expect(store.saveFileStream({
+      data: (async function* (): AsyncIterable<Uint8Array> { yield Uint8Array.of(1) })(),
+      name: 'notes.txt',
+    })).rejects.toMatchObject({ code: 'ATTACHMENT_FILES_UNSUPPORTED' })
+    const fileRef = {
+      attachmentId: AttachmentId(`sha256:${'ab'.repeat(32)}`),
+      name: 'notes.txt',
+      bytes: 1,
+    }
+    expect(store.fileHostPath(fileRef)).toBeUndefined()
+    const read = async (signal?: AbortSignal): Promise<void> => {
+      for await (const chunk of store.readFileStream(fileRef, signal)) {
+        void chunk
+        throw new Error('unsupported store yielded a chunk')
+      }
+    }
+    await expect(read()).rejects.toMatchObject({ code: 'ATTACHMENT_FILES_UNSUPPORTED' })
+    const controller = new AbortController()
+    const reason = new Error('cancel unsupported file read')
+    controller.abort(reason)
+    await expect(read(controller.signal)).rejects.toBe(reason)
   })
 })
 
diff --git a/packages/llm/llm/src/content.ts b/packages/llm/llm/src/content.ts
index 5880f82c98..8ec0c14d35 100644
--- a/packages/llm/llm/src/content.ts
+++ b/packages/llm/llm/src/content.ts
@@ -2,7 +2,9 @@
 
 import type { ContentBlock } from './types.ts'
 import type { Message } from './message.ts'
-import type { AttachmentStore, ImageAttachmentRef, ImageMediaType, RequestImageAttachment } from '@deepseek-ai/dsh-attachment'
+import type {
+  AttachmentStore, FileAttachmentRef, ImageAttachmentRef, ImageMediaType, RequestImageAttachment,
+} from '@deepseek-ai/dsh-attachment'
 import { assertNever } from '@deepseek-ai/dsh-util-values'
 
 /** Execution-world path that model tools can use to read one normalized attachment. */
@@ -126,6 +128,78 @@ export function contentHasImage(content: readonly ContentBlock[]): boolean {
     || (block.type === 'tool-result' && contentHasImage(block.content)))
 }
 
+/**
+ * True when typed model content contains a file block, walking nested
+ * tool-result content on the same recursion every file policy shares.
+ * @param content - typed model content blocks.
+ * @returns whether any nested block is a file.
+ */
+export function contentHasFile(content: readonly ContentBlock[]): boolean {
+  return content.some(block => block.type === 'file'
+    || (block.type === 'tool-result' && contentHasFile(block.content)))
+}
+
+/**
+ * Stable model-facing handle for one durable file reference: the address of
+ * the verbatim stored copy and the instruction to read it on demand. This is
+ * the only representation a provider ever receives for a file.
+ * @param ref - durable verbatim file reference.
+ * @param readonlyPath - execution-world path of the stored copy, when resolvable.
+ * @returns deterministic handle text naming the file, its size, and its address.
+ */
+export function fileHandleText(ref: FileAttachmentRef, readonlyPath: string | undefined): string {
+  const digest = String(ref.attachmentId).slice('sha256:'.length, 'sha256:'.length + 8)
+  const identity = `File ${quoted(ref.name)} (${ref.bytes} bytes, sha256:${digest})`
+  if (readonlyPath === undefined) {
+    return `[${identity} was uploaded, but the current execution environment cannot access a readable path. Report that limitation if its contents are needed; do not claim to have read it.]`
+  }
+  return `[${identity}: verbatim read-only copy saved at ${quoted(readonlyPath)}. Read that path with your file tools when its contents are needed; copy it to a writable location before modifying it. When delegating file work, include this saved path in the delegation prompt; only subagents sharing this execution environment can read it.]`
+}
+
+/** Replace every file occurrence, including nested tool results, with handle text. */
+function replaceFilesWithHandles(
+  blocks: readonly ContentBlock[],
+  resolvePath: (ref: FileAttachmentRef) => string | undefined,
+): ContentBlock[] {
+  let next: ContentBlock[] | undefined
+  for (const [index, block] of blocks.entries()) {
+    if (block.type === 'file') {
+      next ??= blocks.slice(0, index)
+      next.push({ type: 'text', text: fileHandleText(block.attachment, resolvePath(block.attachment)) })
+      continue
+    }
+    if (block.type === 'tool-result') {
+      const content = replaceFilesWithHandles(block.content, resolvePath)
+      if (content !== block.content) {
+        next ??= blocks.slice(0, index)
+        next.push({ ...block, content })
+        continue
+      }
+    }
+    next?.push(block)
+  }
+  return next ?? blocks as ContentBlock[]
+}
+
+/**
+ * Project durable file history into deterministic handle text for every model
+ * route. Unlike images, no provider receives file blocks natively, so this
+ * projection is unconditional in request assembly.
+ * @param messages - complete request history.
+ * @param resolvePath - resolve one reference's current execution-world read path.
+ * @returns the original list without files, otherwise shallow message copies with handle text.
+ */
+export function projectFilesToText(
+  messages: readonly Message[],
+  resolvePath: (ref: FileAttachmentRef) => string | undefined,
+): readonly Message[] {
+  if (!messages.some(message => contentHasFile(message.content))) return messages
+  return messages.map((message) => {
+    const content = replaceFilesWithHandles(message.content, resolvePath)
+    return content === message.content ? message : { ...message, content }
+  })
+}
+
 /** Base64 length of raw image bytes, including padding. */
 function base64Length(bytes: number): number {
   return Math.ceil(bytes / 3) * 4
diff --git a/packages/llm/llm/src/index.ts b/packages/llm/llm/src/index.ts
index cdecc4c96e..23f0228ca9 100644
--- a/packages/llm/llm/src/index.ts
+++ b/packages/llm/llm/src/index.ts
@@ -32,7 +32,10 @@ import type { LlmCallConfig, LlmCallConfigAdapterDefaults } from './call-config.
 import { HarnessError, INVALID_CREDENTIAL_CODE } from './error.ts'
 import { normalizeLlmFailure } from './adapter-failure.ts'
 import { normalizeApiKey } from './api-key.ts'
-import { contentHasImage, projectImagesForTextModel } from './content.ts'
+import {
+  contentHasFile, contentHasImage, fileHandleText, projectFilesToText, projectImagesForTextModel,
+} from './content.ts'
+import type { FileAttachmentRef } from '@deepseek-ai/dsh-attachment'
 
 export * from './attribution.ts'
 export * from './brand.ts'
@@ -660,6 +663,16 @@ export class LlmRuntime extends TypertRemoteService {
     return this.adapters.get(provider)?.adapter.imageRequestPricing(provider, model)
   }
 
+  /**
+   * Resolve the exact text one durable file occurrence contributes to every
+   * provider request in the current execution environment.
+   * @param ref - durable verbatim file reference from model history.
+   * @returns the same deterministic handle text used at adapter dispatch.
+   */
+  fileRequestText(ref: FileAttachmentRef): string {
+    return fileHandleText(ref, this.fileReadPath(ref))
+  }
+
   /** Detach typed adapter-owned modality metadata. */
   private detachedModalities(modalities: readonly ModelModality[] | undefined): ModelModality[] | undefined {
     return modalities === undefined ? undefined : [...modalities]
@@ -956,6 +969,26 @@ export class LlmRuntime extends TypertRemoteService {
     return Object.isFrozen(options) ? deepFreeze(filtered) : filtered
   }
 
+  /**
+   * Resolve the current execution-world read path of one durable file
+   * reference through the mounted attachment and filesystem providers.
+   */
+  private fileReadPath(ref: FileAttachmentRef): string | undefined {
+    let hostPath: string | undefined
+    try {
+      hostPath = this.ctx.get('attachments')?.fileHostPath(ref)
+    } catch {
+      // A malformed durable reference degrades this occurrence to the no-path
+      // handle instead of failing every later request over the same log.
+      return undefined
+    }
+    if (hostPath === undefined) return undefined
+    // Structural face: dsh-llm cannot depend on the filesystem package, and
+    // only this one mapping method is consumed.
+    const fs = this.ctx.get('fs') as { processPathFromHostPath(hostPath: string): string | undefined } | undefined
+    return fs?.processPathFromHostPath(hostPath)
+  }
+
   /**
    * Final adapter boundary. Adapter selection, dispatch, iterator construction,
    * and iteration failures become one terminal failure chunk. Middleware and
@@ -993,13 +1026,21 @@ export class LlmRuntime extends TypertRemoteService {
         : Object.isFrozen(options)
           ? deepFreeze({ ...options, ...resolvedConfig })
           : { ...options, ...resolvedConfig }
-      const projectedOptions = modelInfo.inputModalities !== undefined
+      // Files are never dispatched natively: every route receives handle text.
+      let projectedMessages: readonly Message[] = resolvedOptions.messages
+      if (projectedMessages.some(message => contentHasFile(message.content))) {
+        projectedMessages = projectFilesToText(projectedMessages, ref => this.fileReadPath(ref))
+      }
+      if (modelInfo.inputModalities !== undefined
         && !modelInfo.inputModalities.includes('image')
-        && resolvedOptions.messages.some(message => contentHasImage(message.content))
-        ? Object.isFrozen(resolvedOptions)
-          ? deepFreeze({ ...resolvedOptions, messages: projectImagesForTextModel(resolvedOptions.messages) as Message[] })
-          : { ...resolvedOptions, messages: projectImagesForTextModel(resolvedOptions.messages) as Message[] }
-        : resolvedOptions
+        && projectedMessages.some(message => contentHasImage(message.content))) {
+        projectedMessages = projectImagesForTextModel(projectedMessages)
+      }
+      const projectedOptions = projectedMessages === resolvedOptions.messages
+        ? resolvedOptions
+        : Object.isFrozen(resolvedOptions)
+          ? deepFreeze({ ...resolvedOptions, messages: projectedMessages as Message[] })
+          : { ...resolvedOptions, messages: projectedMessages as Message[] }
       const stream = dispatch(this.forAdapter(projectedOptions, adapter))
       iterator = stream[Symbol.asyncIterator]()
     } catch (error: unknown) {
diff --git a/packages/llm/llm/src/types.ts b/packages/llm/llm/src/types.ts
index 4303538892..c480f57b89 100644
--- a/packages/llm/llm/src/types.ts
+++ b/packages/llm/llm/src/types.ts
@@ -5,7 +5,7 @@
  */
 
 import type { Branded } from '@deepseek-ai/dsh-brand'
-import type { ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
+import type { FileAttachmentRef, ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
 import type { ToolCallId, ProviderRequestId, ReasoningEffortId } from './brand.ts'
 import type { Message } from './message.ts'
 
@@ -74,6 +74,19 @@ export interface ImageBlock {
   attachment: ImageAttachmentRef
 }
 
+/**
+ * A durable verbatim file reference, valid in user content. Files never reach
+ * a provider natively: request assembly projects every occurrence to
+ * deterministic handle text (name, byte size, and the read-only saved path),
+ * so adapters and providers see text in its place while the durable log keeps
+ * the structured reference for presentation and authorization.
+ */
+export interface FileBlock {
+  type: 'file'
+  /** Immutable verbatim bytes and display metadata owned by the attachment service. */
+  attachment: FileAttachmentRef
+}
+
 /** A tool invocation requested by the model. */
 export interface ToolCallBlock {
   type: 'tool-call'
@@ -100,6 +113,7 @@ export interface ContentBlockMap {
   'text': TextBlock
   'reasoning': ReasoningBlock
   'image': ImageBlock
+  'file': FileBlock
   'tool-call': ToolCallBlock
   'tool-result': ToolResultBlock
 }
diff --git a/packages/llm/llm/tests/content.spec.ts b/packages/llm/llm/tests/content.spec.ts
index 748e20f412..af114958b1 100644
--- a/packages/llm/llm/tests/content.spec.ts
+++ b/packages/llm/llm/tests/content.spec.ts
@@ -3,7 +3,10 @@ import { AttachmentId, ImageVariantId } from '@deepseek-ai/dsh-attachment'
 import type { AttachmentStore, ImageMediaType } from '@deepseek-ai/dsh-attachment'
 import {
   ToolCallId,
+  contentHasFile,
   createUserMessage,
+  fileHandleText,
+  projectFilesToText,
   offloadedImageText,
   offloadedImagePrefixCount,
   offloadRequestImagesWithPolicy,
@@ -360,3 +363,80 @@ describe('projectImagesForTextModel', () => {
     ])
   })
 })
+
+describe('file projection', () => {
+  function fileBlock(name: string): Extract<ContentBlock, { type: 'file' }> {
+    return {
+      type: 'file',
+      attachment: {
+        attachmentId: AttachmentId(`sha256:${'ab'.repeat(32)}`),
+        name,
+        bytes: 42,
+      },
+    }
+  }
+
+  it('detects file blocks at the top level and inside nested tool results', () => {
+    expect(contentHasFile([{ type: 'text', text: 'x' }])).toBe(false)
+    expect(contentHasFile([fileBlock('a.txt')])).toBe(true)
+    expect(contentHasFile([{
+      type: 'tool-result',
+      toolCallId: ToolCallId('call-1'),
+      content: [{
+        type: 'tool-result',
+        toolCallId: ToolCallId('call-2'),
+        content: [fileBlock('deep.txt')],
+      }],
+    }])).toBe(true)
+  })
+
+  it('renders the handle with the read path or the explicit no-path fallback', () => {
+    const withPath = fileHandleText(fileBlock('notes.pdf').attachment, '/home/.dsh/attachments/v1/files/ab/x/notes.pdf')
+    expect(withPath).toContain('"notes.pdf"')
+    expect(withPath).toContain('42 bytes')
+    expect(withPath).toContain('sha256:abababab')
+    expect(withPath).toContain('"/home/.dsh/attachments/v1/files/ab/x/notes.pdf"')
+    expect(withPath).toContain('include this saved path in the delegation prompt')
+    expect(withPath).toContain('only subagents sharing this execution environment can read it')
+    const withoutPath = fileHandleText(fileBlock('notes.pdf').attachment, undefined)
+    expect(withoutPath).toContain('current execution environment cannot access a readable path')
+    expect(withoutPath).toContain('do not claim to have read it')
+  })
+
+  it('replaces every file occurrence with handle text and keeps file-free history identical', () => {
+    const plain = [createUserMessage({ content: [{ type: 'text', text: 'hi' }], source })]
+    expect(projectFilesToText(plain, () => '/p')).toBe(plain)
+    const unchangedTool = {
+      type: 'tool-result' as const,
+      toolCallId: ToolCallId('call-plain'),
+      content: [{ type: 'text' as const, text: 'unchanged result' }],
+    }
+    const messages = [plain[0]!, createUserMessage({
+      content: [
+        fileBlock('top.csv'),
+        { type: 'text', text: 'keep' },
+        unchangedTool,
+        {
+          type: 'tool-result',
+          toolCallId: ToolCallId('call-3'),
+          content: [fileBlock('nested.csv')],
+        },
+      ],
+      source,
+    })]
+    const projected = projectFilesToText(messages, ref => `/copies/${ref.name}`)
+    expect(projected).not.toBe(messages)
+    expect(projected[0]).toBe(messages[0])
+    const content = projected[1]!.content
+    expect(content[0]).toEqual({ type: 'text', text: fileHandleText(fileBlock('top.csv').attachment, '/copies/top.csv') })
+    expect(content[1]).toEqual({ type: 'text', text: 'keep' })
+    expect(content[2]).toBe(messages[1]!.content[2])
+    const nested = content[3] as Extract<ContentBlock, { type: 'tool-result' }>
+    expect(nested.content[0]).toEqual({
+      type: 'text',
+      text: fileHandleText(fileBlock('nested.csv').attachment, '/copies/nested.csv'),
+    })
+    // The durable message is untouched: projection returns shallow copies.
+    expect(messages[1]!.content[0]!.type).toBe('file')
+  })
+})
diff --git a/packages/llm/llm/tests/service.spec.ts b/packages/llm/llm/tests/service.spec.ts
index 47309daea1..2bfcd0f486 100644
--- a/packages/llm/llm/tests/service.spec.ts
+++ b/packages/llm/llm/tests/service.spec.ts
@@ -205,6 +205,73 @@ describe('LlmRuntime', () => {
     expect(adapter.lastOptions?.messages[0]).toBe(message)
   })
 
+  it('projects file blocks through every host-path availability outcome', async () => {
+    const attachment = {
+      attachmentId: AttachmentId(`sha256:${'ab'.repeat(32)}`),
+      name: 'notes.txt',
+      bytes: 3,
+    }
+    const cases = [
+      {
+        name: 'native tools under read-only permission receive the mapped read path',
+        attachments: { fileHostPath: () => '/host/notes.txt' },
+        fs: { processPathFromHostPath: () => '/sandbox/notes.txt' },
+        expected: '"/sandbox/notes.txt"',
+      },
+      {
+        name: 'Code Mode under workspace-write permission receives the same mapped read path',
+        attachments: { fileHostPath: () => '/host/notes.txt' },
+        fs: { processPathFromHostPath: () => '/code-sandbox/notes.txt' },
+        expected: '"/code-sandbox/notes.txt"',
+      },
+      {
+        name: 'missing attachment service',
+        expected: 'current execution environment cannot access a readable path',
+      },
+      {
+        name: 'provider without a host path',
+        attachments: { fileHostPath: () => undefined },
+        expected: 'current execution environment cannot access a readable path',
+      },
+      {
+        name: 'invalid durable reference',
+        attachments: { fileHostPath: () => { throw new Error('invalid ref') } },
+        expected: 'current execution environment cannot access a readable path',
+      },
+      {
+        name: 'missing filesystem mapping',
+        attachments: { fileHostPath: () => '/host/notes.txt' },
+        expected: 'current execution environment cannot access a readable path',
+      },
+    ]
+
+    for (const fixture of cases) {
+      const ctx = new Context()
+      if (fixture.attachments !== undefined) ctx.provide('attachments', fixture.attachments as never)
+      if (fixture.fs !== undefined) ctx.provide('fs', fixture.fs as never)
+      await ctx.plugin(LlmRuntime)
+      const adapter = new RecordingAdapter(SCRIPT)
+      ctx.llm.registerAdapter(['test-provider'], adapter)
+
+      await collect(ctx.llm.stream({
+        provider: 'test-provider',
+        model: 'test-model',
+        messages: [createUserMessage({
+          content: [{ type: 'file', attachment }],
+          source: { kind: 'user' },
+        })],
+      }))
+
+      const projected = adapter.lastOptions?.messages[0]?.content[0]
+      expect(projected, fixture.name).toMatchObject({ type: 'text' })
+      if (projected?.type !== 'text') throw new Error(`expected projected text for ${fixture.name}`)
+      expect(projected.text, fixture.name).toContain(fixture.expected)
+      if (fixture.fs !== undefined) {
+        expect(projected.text, fixture.name).toContain('include this saved path in the delegation prompt')
+      }
+    }
+  })
+
   it('captures provider-owned retry policy at registration and defaults omission', async () => {
     const configured = resolveRetryPolicy({ mode: 'always' }, 'test retryPolicy')
     const adapter = new class extends ScriptedAdapter {
diff --git a/packages/llm/token-meter/src/index.ts b/packages/llm/token-meter/src/index.ts
index d97d9d3fc2..c3c3029219 100644
--- a/packages/llm/token-meter/src/index.ts
+++ b/packages/llm/token-meter/src/index.ts
@@ -7,7 +7,7 @@
 import { Context, Service } from '@deepseek-ai/cordis'
 import z from '@deepseek-ai/schemastery'
 import { BlockAssembler } from '@deepseek-ai/dsh-llm'
-import type { LlmImageRequestPricing, Message, TokenUsage } from '@deepseek-ai/dsh-llm'
+import type { LlmImageRequestPricing, LlmRuntime, Message, TokenUsage } from '@deepseek-ai/dsh-llm'
 import { deepFreeze } from '@deepseek-ai/dsh-util-values'
 import type { EpochHeader, Session, SessionEvent } from '@deepseek-ai/dsh-session'
 import { canonicalHeader, headerEquals, isSurfaceEvent } from '@deepseek-ai/dsh-session'
@@ -136,7 +136,8 @@ export class TokenMeter extends Service {
       ? state.header
       : canonicalHeader(requestHeader)
     const pricing = this._routeImagePricing(header)
-    const surface = priceSurface(state.surface, pricing)
+    const fileText = this._fileRequestText()
+    const surface = priceSurface(state.surface, pricing, fileText)
     const anchor = state.anchor
 
     let baseline: TokenMeasurementBaseline
@@ -145,7 +146,7 @@ export class TokenMeter extends Service {
       // Matching headers share one route, so the anchored snapshot reprices
       // under the same pricing as the current surface and the signed delta
       // compares like with like.
-      const anchorSurfaceTokens = priceSurface(anchor.nodes, pricing).surfaceTokens
+      const anchorSurfaceTokens = priceSurface(anchor.nodes, pricing, fileText).surfaceTokens
         + anchor.assistantTokens
       const estimatedAnchorTokens = estimateHeader(header) + anchorSurfaceTokens
       const usage = anchor.usage
@@ -183,6 +184,14 @@ export class TokenMeter extends Service {
     return this.ctx.get('llm')?.imageRequestPricing(config.provider, config.model)
   }
 
+  /** Resolve request-time file projection when an LLM service is mounted. */
+  private _fileRequestText(): (
+    (ref: Parameters<LlmRuntime['fileRequestText']>[0]) => string
+  ) | undefined {
+    const llm = this.ctx.get('llm')
+    return llm === undefined ? undefined : ref => llm.fileRequestText(ref)
+  }
+
   /**
    * Heuristically price one model-visible message (instance face of the pure
    * `estimateMessage` export from `estimate.ts`).
diff --git a/packages/llm/token-meter/src/route-pricing.ts b/packages/llm/token-meter/src/route-pricing.ts
index 402db18ac0..03a1c519c3 100644
--- a/packages/llm/token-meter/src/route-pricing.ts
+++ b/packages/llm/token-meter/src/route-pricing.ts
@@ -1,18 +1,17 @@
 /**
- * Route-aware surface pricing: projects the fold's fixed-heuristic nodes onto
- * the routed model's request, replacing every image occurrence's structural
- * price with the route's declared visual tokens plus the model-visible text it
- * actually sends. Without declared pricing every node keeps its fixed
- * heuristic price, so provider-neutral behavior is unchanged.
+ * Request-projected surface pricing: replaces attachment-block heuristics with
+ * the image and file representations sent to the routed model.
  *
  * @module @deepseek-ai/dsh-token-meter/route-pricing
  */
 
-import type { LlmImageRequestPricing } from '@deepseek-ai/dsh-llm'
+import type { ContentBlock, LlmImageRequestPricing } from '@deepseek-ai/dsh-llm'
 import { estimateContent } from './estimate.ts'
 import type { MeterSurfaceNode } from './surface-fold.ts'
 import type { TokenSurfaceNode } from './types.ts'
 
+type FileAttachmentRef = Extract<ContentBlock, { type: 'file' }>['attachment']
+
 /** One surface priced for a request route: public nodes plus their total. */
 export interface PricedSurface {
   /** Positional nodes carrying both the route price and the fixed-heuristic price. */
@@ -22,9 +21,10 @@ export interface PricedSurface {
 }
 
 /**
- * Price one ordered surface under a route's request-image pricing.
+ * Price one ordered surface under its model-request attachment projection.
  * @param nodes - the fold's current or snapshotted surface, in model-visible order.
  * @param pricing - the routed model's image pricing, or undefined to keep the fixed heuristic.
+ * @param fileText - exact file handle projection used by the mounted LLM service.
  * @returns detached public nodes and their route-priced total.
  * @throws when the pricing answers a different occurrence count than it was
  *   asked — misalignment would silently misprice nodes, so it must fail loud.
@@ -32,9 +32,11 @@ export interface PricedSurface {
 export function priceSurface(
   nodes: readonly MeterSurfaceNode[],
   pricing: LlmImageRequestPricing | undefined,
+  fileText?: (ref: FileAttachmentRef) => string,
 ): PricedSurface {
   const images = pricing === undefined ? [] : nodes.flatMap(node => node.images)
-  if (pricing === undefined || images.length === 0) {
+  const hasFiles = fileText !== undefined && nodes.some(node => node.files.length > 0)
+  if ((pricing === undefined || images.length === 0) && !hasFiles) {
     let surfaceTokens = 0
     const publicNodes = nodes.map((node) => {
       surfaceTokens += node.heuristicTokens
@@ -42,8 +44,8 @@ export function priceSurface(
     })
     return { nodes: publicNodes, surfaceTokens }
   }
-  const prices = pricing.priceImages(images)
-  if (prices.length !== images.length) {
+  const prices = pricing === undefined ? [] : pricing.priceImages(images)
+  if (pricing !== undefined && prices.length !== images.length) {
     throw new Error(
       `token meter: route image pricing answered ${prices.length} prices for ${images.length} occurrences`,
     )
@@ -52,8 +54,14 @@ export function priceSurface(
   let surfaceTokens = 0
   const publicNodes = nodes.map((node) => {
     let tokens = node.heuristicTokens
-    if (node.images.length > 0) {
-      tokens = node.imageFreeTokens
+    if (fileText !== undefined && node.files.length > 0) {
+      tokens -= node.fileStructuralTokens
+      for (const file of node.files) {
+        tokens += estimateContent([{ type: 'text', text: fileText(file) }])
+      }
+    }
+    if (pricing !== undefined && node.images.length > 0) {
+      tokens -= node.imageStructuralTokens
       for (let occurrence = 0; occurrence < node.images.length; occurrence += 1) {
         // oxlint-disable-next-line typescript/no-non-null-assertion -- length equality is asserted above
         const price = prices[cursor]!
diff --git a/packages/llm/token-meter/src/surface-fold.ts b/packages/llm/token-meter/src/surface-fold.ts
index 66824a2974..f947adfc35 100644
--- a/packages/llm/token-meter/src/surface-fold.ts
+++ b/packages/llm/token-meter/src/surface-fold.ts
@@ -10,8 +10,8 @@
  * fallible step read-only and {@link commitSurfaceTokens} mutates in place,
  * so a throw leaves the caller's state untouched and the same malformed
  * event fails identically on every retry.
- * Nodes also carry their durable image occurrences and image-free heuristic
- * price, so `measure()` can reprice image content for the routed model.
+ * Nodes also carry durable attachment occurrences and their structural prices,
+ * so `measure()` can price the request representation sent to the model.
  *
  * @module @deepseek-ai/dsh-token-meter/surface-fold
  */
@@ -22,16 +22,22 @@ import type { ContentBlock, Message } from '@deepseek-ai/dsh-llm'
 import type { ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
 import { estimateMessage, estimateStructuralBlock } from './estimate.ts'
 
+type FileAttachmentRef = Extract<ContentBlock, { type: 'file' }>['attachment']
+
 /** One priced surface node with the image occurrences route pricing replaces. */
 export interface MeterSurfaceNode {
   /** Durable sequence number of the surface event. */
   readonly seq: number
   /** Fixed-heuristic price of the node's exact message. */
   readonly heuristicTokens: number
-  /** Fixed-heuristic price with every image occurrence's structural price removed. */
-  readonly imageFreeTokens: number
+  /** Structural JSON price replaced when the routed request projects images. */
+  readonly imageStructuralTokens: number
+  /** Structural JSON price replaced when request assembly projects files to text. */
+  readonly fileStructuralTokens: number
   /** Durable image occurrences in message order; empty for image-free nodes. */
   readonly images: readonly ImageAttachmentRef[]
+  /** Durable file occurrences in message order; empty for file-free nodes. */
+  readonly files: readonly FileAttachmentRef[]
 }
 
 /** One validated surface transition that has not mutated the priced surface yet. */
@@ -46,31 +52,53 @@ export interface SurfaceTokenPlan {
   readonly target: 'append' | { readonly startIdx: number; readonly endIdx: number }
 }
 
-/** Collect image occurrences recursively and total their structural prices. */
-function collectImages(blocks: readonly ContentBlock[], images: ImageAttachmentRef[]): number {
-  let structuralTokens = 0
+/** Collect projected attachment occurrences and their structural prices. */
+function collectProjectedAttachments(
+  blocks: readonly ContentBlock[],
+  images: ImageAttachmentRef[],
+  files: FileAttachmentRef[],
+): { readonly imageTokens: number; readonly fileTokens: number } {
+  let imageTokens = 0
+  let fileTokens = 0
   for (const block of blocks) {
     if (block.type === 'image') {
       images.push(block.attachment)
-      structuralTokens += estimateStructuralBlock(block)
+      imageTokens += estimateStructuralBlock(block)
+    } else if (block.type === 'file') {
+      files.push(block.attachment)
+      fileTokens += estimateStructuralBlock(block)
     } else if (block.type === 'tool-result') {
-      structuralTokens += collectImages(block.content, images)
+      const nested = collectProjectedAttachments(block.content, images, files)
+      imageTokens += nested.imageTokens
+      fileTokens += nested.fileTokens
     }
   }
-  return structuralTokens
+  return { imageTokens, fileTokens }
 }
 
 /** Build one priced node from a surface event's derived message. */
 function analyzeNode(seq: number, message: Message | null): MeterSurfaceNode {
-  if (message === null) return { seq, heuristicTokens: 0, imageFreeTokens: 0, images: [] }
+  if (message === null) {
+    return {
+      seq,
+      heuristicTokens: 0,
+      imageStructuralTokens: 0,
+      fileStructuralTokens: 0,
+      images: [],
+      files: [],
+    }
+  }
   const heuristicTokens = estimateMessage(message)
   const images: ImageAttachmentRef[] = []
-  const imageStructuralTokens = collectImages(message.content, images)
+  const files: FileAttachmentRef[] = []
+  const structural = collectProjectedAttachments(message.content, images, files)
   return {
     seq,
     heuristicTokens,
-    imageFreeTokens: heuristicTokens - imageStructuralTokens,
+    imageStructuralTokens: structural.imageTokens,
+    fileStructuralTokens: structural.fileTokens,
     images,
+    files,
   }
 }
 
diff --git a/packages/llm/token-meter/tests/route-pricing.spec.ts b/packages/llm/token-meter/tests/route-pricing.spec.ts
index 37ef87ce04..65fb15a2f7 100644
--- a/packages/llm/token-meter/tests/route-pricing.spec.ts
+++ b/packages/llm/token-meter/tests/route-pricing.spec.ts
@@ -1,9 +1,11 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from '@deepseek-ai/cordis'
-import { LlmRuntime, LlmAdapter, createMessage, createUserMessage } from '@deepseek-ai/dsh-llm'
+import {
+  LlmRuntime, LlmAdapter, createMessage, createUserMessage, projectFilesToText,
+} from '@deepseek-ai/dsh-llm'
 import type { GenerateOptions, LlmImageRequestPricing, Message, StreamChunk, TokenUsage, UserMessage } from '@deepseek-ai/dsh-llm'
 import { AttachmentId } from '@deepseek-ai/dsh-attachment'
-import type { ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
+import type { FileAttachmentRef, ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
 import { Session, SessionId, canonicalHeader } from '@deepseek-ai/dsh-session'
 import type { EpochHeader } from '@deepseek-ai/dsh-session'
 import SessionProjectionRegistry from '@deepseek-ai/dsh-session-projection'
@@ -53,6 +55,14 @@ function imageMessage(name: string, text = 'look at this'): UserMessage {
   })
 }
 
+function fileRef(name: string): FileAttachmentRef {
+  return {
+    attachmentId: AttachmentId(`sha256:${'ab'.repeat(32)}`),
+    name,
+    bytes: 2_447_000_000,
+  }
+}
+
 function header(model: string): EpochHeader {
   return canonicalHeader({ config: { provider: 'mock', model } })
 }
@@ -65,6 +75,12 @@ interface Harness {
 async function harness(pricing: (model: string) => LlmImageRequestPricing | undefined): Promise<Harness> {
   const ctx = new Context()
   new SessionProjectionRegistry(ctx)
+  ctx.provide('attachments', {
+    fileHostPath: (ref: FileAttachmentRef) => `/host/${ref.name}`,
+  } as never)
+  ctx.provide('fs', {
+    processPathFromHostPath: (path: string) => path.replace('/host/', '/sandbox/'),
+  } as never)
   const llm = new LlmRuntime(ctx)
   llm.registerAdapter(['mock'], new PricingAdapter(pricing))
   const meter = new TokenMeter(ctx)
@@ -96,7 +112,23 @@ function appendSuccessfulCall(session: Session, value: EpochHeader, usage?: Toke
   session.append('step/end', { turn: 1, step: 1 })
 }
 
-describe('route-aware image pricing', () => {
+describe('request projection pricing', () => {
+  it('prices file blocks as the exact handle text dispatched to the provider', async () => {
+    const { meter, session } = await harness(() => undefined)
+    const ref = fileRef('archive.zip')
+    const message = createUserMessage({
+      content: [{ type: 'file', attachment: ref }],
+      source: { kind: 'user' },
+    })
+    session.append('user/message', message, { surfaceOp: 'append' })
+
+    const measurement = meter.measure(session)
+    const projected = projectFilesToText([message], file => `/sandbox/${file.name}`)[0]
+    if (projected === undefined) throw new Error('missing projected file message')
+    expect(measurement.nodes[0]?.tokens).toBe(estimateMessage(projected))
+    expect(measurement.nodes[0]?.tokens).toBeGreaterThan(estimateMessage(message))
+  })
+
   it('prices a first multimodal request estimate with the routed visual tokens', async () => {
     const { meter, session } = await harness(() => fixedPricing)
     const message = imageMessage('photo')
diff --git a/packages/session-query/session-log-export/src/archive.ts b/packages/session-query/session-log-export/src/archive.ts
index 2f7d1fbd11..d89e036193 100644
--- a/packages/session-query/session-log-export/src/archive.ts
+++ b/packages/session-query/session-log-export/src/archive.ts
@@ -1,12 +1,12 @@
 /**
  * Host-side session-log download: streams one ZIP archive whose files are the
- * sessions' stored artifact text verbatim plus every referenced media object.
+ * sessions' stored artifact text verbatim plus every referenced attachment.
  * The root artifact sits under its original base name (`session.jsonl`); each
  * subagent descendant under `subagents/<id>/<filename>`; each image referenced
  * by any included log under `media/<attachmentId>.<ext>` (content-addressed,
- * so one archive never duplicates a shared image). No manifest is written —
- * every file is byte-identical to the backend's durable artifact or attachment
- * store and self-describing through its own header line or media type. Before
+ * so one archive never duplicates a shared image); each file under
+ * `files/<prefix>/<digest>/<name>`. No manifest is written. Every entry is
+ * byte-identical to the backend's durable artifact or attachment store. Before
  * each live session's artifact read, the SessionStore flush barrier makes the
  * current in-memory log durable; cold sessions need no barrier. Request abort
  * and response-consumer cancellation share one producer signal and terminate
@@ -21,7 +21,9 @@
 
 import { Zip, ZipDeflate } from 'fflate'
 import type { Context } from '@deepseek-ai/cordis'
-import type { AttachmentStore, ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
+import type {
+  AttachmentStore, FileAttachmentRef, ImageAttachmentRef,
+} from '@deepseek-ai/dsh-attachment'
 import type { SessionLineageNode, SessionQueryEngine } from '@deepseek-ai/dsh-session-query'
 import type { SessionId, SessionStore } from '@deepseek-ai/dsh-session'
 import type { SessionPersistence, SessionRawArtifact } from '@deepseek-ai/dsh-session-persistence'
@@ -84,10 +86,11 @@ export async function flushLiveSessionLog(
   signal?.throwIfAborted()
 }
 
-/** One exported file: a stored artifact text or one referenced media object. */
+/** One exported artifact or referenced attachment object. */
 export type SessionLogZipEntry =
   | { readonly path: string; readonly content: string }
   | { readonly path: string; readonly data: Uint8Array }
+  | { readonly path: string; readonly chunks: AsyncIterable<Uint8Array> }
 
 /** Zip extension for each accepted raster media type. */
 const MEDIA_TYPE_EXTENSIONS: Record<ImageAttachmentRef['mediaType'], string> = {
@@ -108,13 +111,26 @@ function mediaEntryPath(ref: ImageAttachmentRef): string {
   return `media/${String(ref.attachmentId)}.${MEDIA_TYPE_EXTENSIONS[ref.mediaType]}`
 }
 
+/** Archive path that preserves one stored file reference's digest and name. */
+function fileEntryPath(ref: FileAttachmentRef): string {
+  const digest = String(ref.attachmentId).replace(/^sha256:/u, '')
+  const name = ref.name.replace(/[\\/\u0000-\u001f\u007f]/gu, '_')
+  const safeName = name === '.' || name === '..' || name === '' ? 'file' : name
+  return `files/${digest.slice(0, 2)}/${digest}/${safeName}`
+}
+
 /**
- * Collect every image reference inside one content array, descending into
+ * Collect every attachment reference inside one content array, descending into
  * nested tool results the way the live attachment route does.
  * @param content - an event content array (or nested tool-result content).
- * @param refs - the dedupe map being filled (keyed by attachment id).
+ * @param images - image dedupe map keyed by attachment id.
+ * @param files - file dedupe map keyed by attachment id and stored name.
  */
-function collectImageRefs(content: unknown, refs: Map<string, ImageAttachmentRef>): void {
+function collectAttachmentRefs(
+  content: unknown,
+  images: Map<string, ImageAttachmentRef>,
+  files: Map<string, FileAttachmentRef>,
+): void {
   if (!Array.isArray(content)) return
   const pending: unknown[] = []
   for (const item of content) pending.push(item)
@@ -124,7 +140,11 @@ function collectImageRefs(content: unknown, refs: Map<string, ImageAttachmentRef
     const block = value as { type?: unknown; attachment?: unknown; content?: unknown }
     if (block.type === 'image' && typeof block.attachment === 'object' && block.attachment !== null) {
       const ref = block.attachment as ImageAttachmentRef
-      refs.set(String(ref.attachmentId), ref)
+      images.set(String(ref.attachmentId), ref)
+    }
+    if (block.type === 'file' && typeof block.attachment === 'object' && block.attachment !== null) {
+      const ref = block.attachment as FileAttachmentRef
+      files.set(`${String(ref.attachmentId)}\u0000${ref.name}`, ref)
     }
     if (Array.isArray(block.content)) {
       for (const item of block.content) pending.push(item)
@@ -133,13 +153,18 @@ function collectImageRefs(content: unknown, refs: Map<string, ImageAttachmentRef
 }
 
 /**
- * Collect every image reference one session event carries, across the same
+ * Collect every attachment reference one session event carries, across the same
  * carriers the live attachment route scans (direct content, message content,
  * inserted messages, and completed assistant chunk blocks).
  * @param event - one parsed JSONL event object.
- * @param refs - the dedupe map being filled (keyed by attachment id).
+ * @param images - image dedupe map keyed by attachment id.
+ * @param files - file dedupe map keyed by attachment id and stored name.
  */
-function collectEventImageRefs(event: unknown, refs: Map<string, ImageAttachmentRef>): void {
+function collectEventAttachmentRefs(
+  event: unknown,
+  images: Map<string, ImageAttachmentRef>,
+  files: Map<string, FileAttachmentRef>,
+): void {
   const data = (event as { data?: unknown }).data
   if (typeof data !== 'object' || data === null) return
   const carrier = data as {
@@ -148,23 +173,27 @@ function collectEventImageRefs(event: unknown, refs: Map<string, ImageAttachment
     inserted?: Array<{ content?: unknown }>
     chunk?: { type?: unknown; block?: unknown }
   }
-  collectImageRefs(carrier.content, refs)
-  if (carrier.message !== undefined) collectImageRefs(carrier.message.content, refs)
+  collectAttachmentRefs(carrier.content, images, files)
+  if (carrier.message !== undefined) collectAttachmentRefs(carrier.message.content, images, files)
   if (carrier.inserted !== undefined) {
-    for (const message of carrier.inserted) collectImageRefs(message.content, refs)
+    for (const message of carrier.inserted) collectAttachmentRefs(message.content, images, files)
   }
-  if (carrier.chunk?.type === 'block-end') collectImageRefs([carrier.chunk.block], refs)
+  if (carrier.chunk?.type === 'block-end') collectAttachmentRefs([carrier.chunk.block], images, files)
 }
 
 /**
- * Collect the distinct media references one stored artifact text names.
- * Lines that fail to parse cannot reference media and are skipped (the
+ * Collect the distinct attachment references one stored artifact text names.
+ * Lines that fail to parse cannot reference attachments and are skipped (the
  * artifact text itself is exported verbatim regardless).
  * @param content - the stored artifact text.
- * @returns the dedupe map keyed by attachment id.
+ * @returns image and file dedupe maps.
  */
-function imageRefsInArtifact(content: string): Map<string, ImageAttachmentRef> {
-  const refs = new Map<string, ImageAttachmentRef>()
+function attachmentRefsInArtifact(content: string): {
+  readonly images: Map<string, ImageAttachmentRef>
+  readonly files: Map<string, FileAttachmentRef>
+} {
+  const images = new Map<string, ImageAttachmentRef>()
+  const files = new Map<string, FileAttachmentRef>()
   for (const line of content.split('\n')) {
     if (line === '') continue
     let event: unknown
@@ -173,9 +202,9 @@ function imageRefsInArtifact(content: string): Map<string, ImageAttachmentRef> {
     } catch {
       continue
     }
-    collectEventImageRefs(event, refs)
+    collectEventAttachmentRefs(event, images, files)
   }
-  return refs
+  return { images, files }
 }
 
 /**
@@ -204,10 +233,10 @@ export function sessionLogZipFilename(sessionId: string): string {
  * Yield the export entries in zip order: the preloaded root artifact first,
  * then every subagent descendant in lineage order (each flushed when live,
  * read from the persistence backend right before it is yielded, and dropped
- * after the consumer moves on), then every distinct media object referenced by any of
- * the included logs (read and verified from the attachment store, one archive
- * entry per attachment id). The host holds at most one descendant's artifact
- * text and one media object at a time beyond the root.
+ * after the consumer moves on), then every distinct attachment referenced by
+ * the included logs. Images are read and verified as bounded stored objects;
+ * generic files remain streamed through the ZIP writer. The host holds at most
+ * one descendant artifact, one image, and one file chunk beyond the root.
  * @param deps - the mounted export services (the caller answered 500 before this runs).
  * @param root - the already-read root artifact (read by the caller so the
  * missing-session path can answer cleanly before streaming starts).
@@ -224,10 +253,13 @@ export async function* sessionLogZipEntries(
   signal?: AbortSignal,
 ): AsyncGenerator<SessionLogZipEntry> {
   const media = new Map<string, ImageAttachmentRef>()
-  const rememberMedia = (content: string): void => {
-    for (const [id, ref] of imageRefsInArtifact(content)) media.set(id, ref)
+  const files = new Map<string, FileAttachmentRef>()
+  const rememberAttachments = (content: string): void => {
+    const refs = attachmentRefsInArtifact(content)
+    for (const [id, ref] of refs.images) media.set(id, ref)
+    for (const [id, ref] of refs.files) files.set(id, ref)
   }
-  rememberMedia(root.content)
+  rememberAttachments(root.content)
   yield { path: root.filename, content: root.content }
   if (includeDescendants) {
     const seen = new Set<SessionId>([sessionId])
@@ -245,7 +277,7 @@ export async function* sessionLogZipEntries(
         if (raw === undefined) {
           throw new Error(`subagent "${id}" has no stored log artifact`)
         }
-        rememberMedia(raw.content)
+        rememberAttachments(raw.content)
         yield {
           path: `subagents/${safeSessionIdSegment(id)}/${raw.filename}`,
           content: raw.content,
@@ -263,6 +295,13 @@ export async function* sessionLogZipEntries(
     signal?.throwIfAborted()
     yield { path: mediaEntryPath(ref), data: stored.data }
   }
+  for (const ref of files.values()) {
+    signal?.throwIfAborted()
+    yield {
+      path: fileEntryPath(ref),
+      chunks: deps.attachments.readFileStream(ref, signal),
+    }
+  }
 }
 
 /** How many code units of artifact text one zip push carries (bounded encode memory). */
@@ -334,6 +373,25 @@ async function pushBinaryChunks(
   } while (offset < data.byteLength)
 }
 
+/** Push one streamed file entry without retaining its complete byte sequence. */
+async function pushStreamChunks(
+  deflate: ZipDeflate,
+  chunks: AsyncIterable<Uint8Array>,
+  controller: ReadableStreamDefaultController<Uint8Array>,
+  capacity: ResponseCapacityGate,
+  signal: AbortSignal,
+): Promise<void> {
+  for await (const chunk of chunks) {
+    signal.throwIfAborted()
+    if (chunk.byteLength === 0) continue
+    deflate.push(chunk, false)
+    await capacity.wait(controller, signal)
+  }
+  signal.throwIfAborted()
+  deflate.push(new Uint8Array(), true)
+  await capacity.wait(controller, signal)
+}
+
 /**
  * Push one artifact's text into a deflate stream in bounded chunks, never
  * splitting a surrogate pair across a chunk boundary (a lone high surrogate
@@ -427,8 +485,10 @@ export function streamSessionLogZip(
             archive.add(deflate)
             if ('content' in entry) {
               await pushArtifactChunks(deflate, entry.content, controller, capacity, producerSignal)
-            } else {
+            } else if ('data' in entry) {
               await pushBinaryChunks(deflate, entry.data, controller, capacity, producerSignal)
+            } else {
+              await pushStreamChunks(deflate, entry.chunks, controller, capacity, producerSignal)
             }
           }
           archive.end()
diff --git a/packages/session-query/session-log-export/src/index.ts b/packages/session-query/session-log-export/src/index.ts
index 88c4cc6ccb..91a97faff9 100644
--- a/packages/session-query/session-log-export/src/index.ts
+++ b/packages/session-query/session-log-export/src/index.ts
@@ -55,6 +55,7 @@ interface SessionLogConnection {
     register(route: {
       readonly path: string
       readonly methods: readonly ('GET' | 'HEAD')[]
+      readonly requestBody: 'buffered'
       readonly fetch: (request: Request) => Promise<Response>
     }): () => Promise<void>
   }
@@ -81,6 +82,7 @@ export function apply(ctx: Context, config: Config = {}): void {
   connectionOf(ctx).fetch.register({
     path: SESSION_LOG_EXPORT_PATH,
     methods: ['GET', 'HEAD'],
+    requestBody: 'buffered',
     fetch: async (request) => {
       const response = await sessionLogExportResponse(
         ctx,
diff --git a/packages/session-query/session-log-export/tests/archive.host.spec.ts b/packages/session-query/session-log-export/tests/archive.host.spec.ts
index c41846039a..af1ea9e428 100644
--- a/packages/session-query/session-log-export/tests/archive.host.spec.ts
+++ b/packages/session-query/session-log-export/tests/archive.host.spec.ts
@@ -9,7 +9,7 @@ import { randomBytes } from 'node:crypto'
 import { describe, expect, it, vi } from 'vitest'
 import { Context } from '@deepseek-ai/cordis'
 import { unzipSync, strFromU8 } from 'fflate'
-import type { ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
+import type { FileAttachmentRef, ImageAttachmentRef } from '@deepseek-ai/dsh-attachment'
 import type { SessionHeader, SessionId } from '@deepseek-ai/dsh-session'
 import type { SessionLineageNode } from '@deepseek-ai/dsh-session-query'
 import type { SessionRawArtifact } from '@deepseek-ai/dsh-session-persistence'
@@ -55,6 +55,11 @@ function imageEventLine(id: string, mediaType: ImageAttachmentRef['mediaType'] =
   return `{"type":"user/message","seq":1,"time":1000,"data":{"content":[{"type":"image","attachment":{"attachmentId":"${id}","mediaType":"${mediaType}","bytes":4,"width":2,"height":2}}]}}`
 }
 
+/** A user/message event line carrying one generic-file reference. */
+function fileEventLine(id: string, name = 'notes.txt', bytes = 5): string {
+  return `{"type":"user/message","seq":1,"time":1000,"data":{"content":[{"type":"file","attachment":{"attachmentId":"${id}","name":"${name}","bytes":${bytes}}}]}}`
+}
+
 async function buildApi(
   artifacts: Record<string, SessionRawArtifact>,
   descendants: SessionLineageNode[] = [],
@@ -62,6 +67,7 @@ async function buildApi(
     query?: boolean
     persistence?: boolean | 'throw' | 'unsupported'
     attachments?: boolean | ((ref: ImageAttachmentRef, signal?: AbortSignal) => Promise<ReturnType<typeof storedImage>>)
+    readFileStream?: (ref: FileAttachmentRef, signal?: AbortSignal) => AsyncIterable<Uint8Array>
     sessions?: {
       get(id: SessionId): { readonly id: SessionId } | undefined
       flush(session: { readonly id: SessionId }): Promise<boolean>
@@ -110,6 +116,9 @@ async function buildApi(
       validateImage: async () => {},
       saveImage: async () => { throw new Error('export never saves images') },
       readImage,
+      readFileStream: services.readFileStream ?? (async function* () {
+        throw new Error('fixture has no files')
+      }),
     } as never)
   }
   if (services.sessions !== undefined) ctx.provide('sessions', services.sessions as never)
@@ -630,6 +639,52 @@ describe('session.export download endpoint', () => {
     expect(files['media/img-1.png']).toEqual(storedImage('img-1').data)
   })
 
+  it('streams generic files under their content-addressed archive paths', async () => {
+    const digest = 'a'.repeat(64)
+    const id = `sha256:${digest}`
+    const fallbackDigest = 'c'.repeat(64)
+    const fallbackId = `sha256:${fallbackDigest}`
+    const root = artifact('session-root', undefined, [
+      '{"type":"session","version":0,"id":"session-root","createdAt":1000}',
+      fileEventLine(id, 'notes.txt', 5),
+      fileEventLine(fallbackId, '.', 5),
+    ].join('\n') + '\n')
+    const reads: Array<{ ref: FileAttachmentRef; signal: AbortSignal | undefined }> = []
+    const api = await buildApi({ 'session-root': root }, [], {
+      readFileStream: (ref, signal) => (async function* (): AsyncIterable<Uint8Array> {
+        reads.push({ ref, signal })
+        yield new Uint8Array()
+        yield Uint8Array.of(1, 2)
+        yield Uint8Array.of(3, 4, 5)
+      })(),
+    })
+    const response = await toFetchHandler(api).fetch(
+      new Request('http://host/api/session.export?sessionId=session-root'),
+    )
+    const files = unzipSync(await responseBytes(response))
+    expect(files[`files/aa/${digest}/notes.txt`]).toEqual(Uint8Array.of(1, 2, 3, 4, 5))
+    expect(files[`files/cc/${fallbackDigest}/file`]).toEqual(Uint8Array.of(1, 2, 3, 4, 5))
+    expect(reads).toHaveLength(2)
+    expect(reads[0]?.ref).toMatchObject({ attachmentId: id, name: 'notes.txt', bytes: 5 })
+    expect(reads[0]?.signal).toBeInstanceOf(AbortSignal)
+  })
+
+  it('fails the whole export when a referenced file stream fails', async () => {
+    const digest = 'b'.repeat(64)
+    const id = `sha256:${digest}`
+    const root = artifact('session-root', undefined, fileEventLine(id))
+    const api = await buildApi({ 'session-root': root }, [], {
+      readFileStream: () => (async function* (): AsyncIterable<Uint8Array> {
+        yield Uint8Array.of(1)
+        throw new Error('file bytes missing')
+      })(),
+    })
+    const response = await toFetchHandler(api).fetch(
+      new Request('http://host/api/session.export?sessionId=session-root'),
+    )
+    await expect(response.arrayBuffer()).rejects.toThrow('file bytes missing')
+  })
+
   it('collects media referenced from nested tool results', async () => {
     const nested = '{"type":"assistant/message","seq":2,"time":2000,"data":{"content":[{"type":"tool-result","content":[{"type":"image","attachment":{"attachmentId":"nested-1","mediaType":"image/webp","bytes":4,"width":2,"height":2}}]}]}}'
     const root = artifact('session-root', undefined, [