fix: preserve multi-image prompt batches

packages/attachment/attachment/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/attachment/attachment/README.md
-README.md: b25ef7bcf89b3b85600ed02ab12eb0cdd1117244
-README.zh.md: f45933c2a011978b31a306a1de80d7f031838c8e
+README.md: 4f450316294e554396adb9a8454051a08d9befd3
+README.zh.md: fe51b0003cdf1659c7c56106b97c6f3139ebe890

packages/attachment/attachment/README.md

@@ -4,7 +4,7 @@ English | [中文](README.zh.md)
 
 The durable attachment seam. `ctx.attachments` validates and atomically commits immutable image bytes, then returns a serializable `ImageAttachmentRef`; consumers never persist browser paths, object URLs, provider URLs, or base64 in session events.
 
-Unsent composer images remain browser-owned temporary drafts. `saveImage` validates and commits one image at message submission or while committing structured provider output, before any model-visible session event is published. `readImage` verifies the content-addressed object against its logged metadata.
+Unsent composer images remain browser-owned temporary drafts. `validateImage` runs the same admission policy without persisting; batch writers validate every member first so a malformed member cannot strand earlier members as unreferenced objects. `saveImage` commits each accepted image before any model-visible session event is published, and `readImage` verifies the content-addressed object against its logged metadata.
 
 ## Model Experience
 

packages/attachment/attachment/README.zh.md

@@ -4,7 +4,7 @@
 
 持久附件服务边界。`ctx.attachments` 校验并以原子方式提交不可变图片字节，随后返回可序列化的 `ImageAttachmentRef`；消费方绝不会在会话事件中持久保存浏览器路径、对象 URL、提供方 URL 或 base64。
 
-未发送的输入区图片仍是由浏览器持有的临时草稿。`saveImage` 在提交消息或提交结构化提供方输出时校验并提交一张图片，且发生在发布任何模型可见的会话事件之前。`readImage` 根据已记录的元数据校验内容寻址对象。
+未发送的输入区图片仍是由浏览器持有的临时草稿。`validateImage` 运行相同的准入策略，但不执行持久化；批量写入方会先校验每个成员，避免某个格式错误的成员使较早的成员成为无引用对象。`saveImage` 会在发布任何模型可见的会话事件前提交每张已接受的图片，`readImage` 则根据已记录的元数据校验内容寻址对象。
 
 ## 模型体验
 

packages/attachment/attachment/src/index.ts

@@ -33,6 +33,13 @@ export abstract class AttachmentStore extends Service {
   /** Deployment-resolved image policy used by authoritative and fast-path validation. */
   abstract readonly imageLimits: ImageAttachmentLimits
 
+  /**
+   * Validate one image without persisting it.
+   * Batch callers validate every member before saving any member.
+   * @param input - encoded bytes, declared media type, and optional display name.
+   */
+  abstract validateImage(input: SaveImageAttachment): void
+
   /**
    * Validate and durably commit one image before its owning session event is appended.
    * @param input - encoded bytes, declared media type, and optional display name.

packages/attachment/attachment/src/types.ts

@@ -36,6 +36,8 @@ export interface ImageAttachmentRef {
 /** Deployment-resolved limits shared by upload consumers and UI preflight. */
 export interface ImageAttachmentLimits {
   maxImageBytes: number
+  maxImagesPerMessage: number
+  maxMessageImageBytes: number
   maxImagePixels: number
   mediaTypes: readonly ImageMediaType[]
 }