Add web multimodal image attachments

2026-07-23 15:20:47 +08:00
parent 3e3ea47296
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--- a/.agents/notes/proposed/feature/2026-07-22-web-multimodal-image-input-and-durable-attachments.i18n.yaml
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+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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
+2026-07-22-web-multimodal-image-input-and-durable-attachments.md: 14ad4e5ceb28fd7df8b639db403be8accd8c2028
+2026-07-22-web-multimodal-image-input-and-durable-attachments.zh.md: 5752247b080ee1be0b0bfbbf7a9fb7486ff6c41b
--- a/.agents/notes/proposed/feature/2026-07-22-web-multimodal-image-input-and-durable-attachments.md
+++ b/.agents/notes/proposed/feature/2026-07-22-web-multimodal-image-input-and-durable-attachments.md
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+# Agent Note: Web multimodal image input and durable attachments
+
+Status: proposed
+
+English | [中文](2026-07-22-web-multimodal-image-input-and-durable-attachments.zh.md)
+
+## Problem
+
+The Web composer accepts only text: `InputBar` receives a string draft, `ConversationService.send()` creates text content, and the host forwards that content to the agent. Users cannot paste an image, inspect it before sending, submit an image-only prompt, or recover sent images from history.
+
+This is not only a composer gap. Core needs a durable image content block, providers need explicit modality handling, and the session log must reconstruct everything visible to a model. [The previous image-block removal](../../implemented/simplification/2026-07-04-drop-image-content-block.md) rejected a partial design that could silently lose or flatten images. A browser object URL, local path, provider URL, or base64 payload cannot be canonical session content.
+
+The [Web client architecture](../../implemented/architecture/2026-07-19-gui-web-client-architecture.md) keeps components pure and per-session composer state in `ctx.conversation`; the [GUI layering and RPC protocol](../../implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md) makes durable events the source of truth for both live rendering and history replay. Image intake, persistence, provider conversion, and rendering therefore need one explicit lifecycle.
+
+Peer products converge on an attachment rail above the editor, but their storage choices differ. Codex-style paths such as `/var/folders/.../codex-clipboard-*.png` are reasonable intake staging locations, not durable message identities: the operating system may delete them, another host cannot read them, and a resumed session cannot rely on them.
+
+## Proposal
+
+Add pasted or dropped raster images to the Web composer as the first consumer of a durable attachment capability. Unsent files remain temporary client-owned draft state. The host validates and durably commits every accepted user image before appending its message event. A provider adapter that produces structured image output must durably commit the output before appending its assistant block. Canonical user and assistant content contains only role-neutral `ImageBlock` references.
+
+Version one supports PNG, JPEG, WebP, and GIF paste and drag-and-drop, image-only or mixed prompts, historical user and assistant image rendering, and original-image preview on double-click. File picking, generic files, PDF, audio, video, image copying, and a custom context menu are separate follow-ups.
+
+### Product behavior
+
+- Pasting or dropping one or more supported images adds ordered thumbnails above the textarea without inserting placeholder text. Dragging files over the composer highlights the drop target.
+- The rail is shared by the empty-state and resident composers, is hidden when empty, and scrolls horizontally instead of widening the composer.
+- Each approximately 72-by-72-pixel thumbnail has a remove action and opens its original draft image on double-click.
+- A prompt may contain text and images or images only. Pure text paste remains native browser behavior; the paste handler prevents the default only when it accepts an image file. File drops on the composer always prevent browser navigation, accept supported images, and report unsupported files locally.
+- A failed send restores the complete text and image draft. Removal, successful send, and session-scope disposal revoke obsolete object URLs.
+- Historical user and assistant images use one `MessageImage` control. Inline images preserve intrinsic aspect ratio, do not upscale, and stay within a 240-by-240-pixel box.
+- Double-clicking a message image opens the stored original in a viewport-bounded modal. Escape, the close control, and backdrop activation close it and restore focus.
+- Version one does not override the browser context menu and provides no explicit image-copy action.
+
+### Storage lifecycle and ownership
+
+The persistence boundary is message acceptance, not paste:
+
+| State | Allowed representation | Durability and ordering |
+| --- | --- | --- |
+| Unsent user draft | Browser `File` plus object URL; a native client may use an OS temporary file such as `/var/...` | Temporary and client-owned. It may disappear on reload or process exit and never appears in a session event. |
+| Accepted user image | Immutable object below `DSH_HOME` plus `ImageAttachmentRef` | The host commits every image before `agent.send()` or `agent.steer()` can append the owning user event. |
+| Structured model image output | Immutable object below `DSH_HOME` plus `ImageAttachmentRef` | The provider adapter commits the bytes before it emits a completed image block or assistant message event. Temporary URLs, paths, and base64 are forbidden in the event. |
+
+The framework-owned chat store keeps the per-session draft text and ordered attachment identifiers. `ConversationService` owns the corresponding browser-only `File` and object-URL registry:
+
+```ts
+export {}
+
+interface ChatStoreState {
+  selection: object | null
+  draft: string
+  imageIds: string[]
+  view: string | null
+}
+
+interface ComposerAttachment {
+  id: string
+  file: File
+  previewUrl: string
+}
+```
+
+This split uses the slots framework's store seat and bound actions as the single subscription path for UI state while keeping non-serializable browser objects out of persisted JSON. Draft text and ordered image identifiers continue to use `localStorage`; after a reload, `ConversationRoot` prunes identifiers whose runtime objects no longer exist. Unsent images therefore do not survive reload because browser `File` and object URLs are not durable. A native client may stage input in an OS temporary directory, but it must treat that path exactly like the browser object URL: delete it when no longer needed and copy the bytes into the durable store before message acceptance.
+
+The local attachment backend resolves an explicit `dshHome`, then `$DSH_HOME`, then `~/.dsh`. It stores content-addressed objects below `$DSH_HOME/attachments/v1/objects/<prefix>/<sha256>` with owner-only directory and file permissions. A temporary file is written, synchronized, and atomically published before the service returns a reference. The content digest is encoded in the opaque `sha256:<digest>` identifier, and every read verifies the digest, media type, byte length, width, and height.
+
+The store performs no automatic deletion in version one. Sent user images and model-generated images remain reachable for history, resume, and fork. Reference-aware garbage collection needs a separate design because an age-only rule can delete data still referenced by a durable session.
+
+### Durable content and prompt wire
+
+The attachment seam exposes immutable image write and verified read operations. The canonical metadata is deliberately narrower than a generic file record:
+
+```ts
+import type { Branded } from '@deepseek-ai/dsh-brand'
+
+type AttachmentId = Branded<'AttachmentId'>
+
+interface ImageAttachmentRef {
+  attachmentId: AttachmentId
+  mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
+  bytes: number
+  width: number
+  height: number
+  name?: string
+}
+
+interface ImageBlock {
+  type: 'image'
+  attachment: ImageAttachmentRef
+}
+```
+
+`ImageBlock` joins the merge-extensible core `ContentBlockMap` and is valid in either user or assistant content. It never carries base64, an object URL, a filesystem path, or a provider-owned locator. This keeps the session event plus immutable object store sufficient to reconstruct the exact model-visible image.
+
+The browser cannot mint a durable reference, so `session.prompt` accepts a narrow intake union rather than canonical `ContentBlock[]`:
+
+```ts
+export {}
+
+type PromptInputPart =
+  | { type: 'text'; text: string }
+  | {
+      type: 'image'
+      mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
+      data: string
+      name?: string
+    }
+```
+
+Base64 crosses JSON-RPC once and is discarded after persistence. The host validates canonical base64, image count, aggregate bytes, individual bytes, magic-byte MIME, intrinsic dimensions, and decoded-pixel count. Only after every image succeeds does it call the agent with normalized text and durable image blocks. A failure appends no user event and exposes no attachment path or raw bytes.
+
+`session.attachment` is a read-only, session-scoped endpoint. The host serves bytes only when a durable event in that session references the requested attachment identifier. The client caches the resulting object URL by session and attachment identifier for its service lifetime and revokes it on disposal.
+
+### Model capabilities and provider behavior
+
+Model catalog entries gain optional merge-extensible input and output modality declarations. A missing declaration means unknown; a present list without `image` is an explicit negative capability.
+
+The host is the authoritative preflight boundary. If the selected model explicitly excludes image input, it rejects the prompt before writing any attachment or event, and the client restores the draft. Unknown capability proceeds to the adapter guard so uncatalogued model identifiers remain usable. Immediate intake-time rejection in the UI may be added after model selection is exposed consistently across every Web entry path.
+
+The Pi-AI adapter is the first visual-input route: it resolves each durable reference through `ctx.attachments` and emits native image content only for models that declare image input. The hand-written DeepSeek adapter throws typed `UNSUPPORTED_CONTENT` for an image anywhere in the request, including nested tool results. No adapter may flatten or skip an image.
+
+Core supports structured assistant image blocks, but no current production provider route is certified for image output. Any future output-capable adapter must retrieve provider bytes under bounded size and time policy, validate them through the same attachment service, persist them, and only then publish the atomic `ImageBlock`. A URL in assistant Markdown remains text and is never downloaded automatically.
+
+Token estimation accounts for image dimensions without counting base64 or attachment locators as text. Provider-reported usage remains authoritative. ACP renders an explicit image marker until that protocol surface gains native image support rather than silently omitting the block.
+
+### History rendering and original preview
+
+History folding preserves `ImageBlock` in both user and assistant messages. User images align to the trailing edge above their text; assistant images align to the leading narration flow. `MessageImage` derives a stable inline box from recorded dimensions, resolves bytes through the session-authorized loader, uses `object-fit: contain`, and turns a missing or corrupt object into a retryable error control.
+
+Composer thumbnails and each `MessageImage` own ephemeral original-preview state and invoke the same pure `ImageLightbox`. The modal uses the already resolved original object URL, constrains only display size, focuses its close control, and restores the previous focus target when closed.
+
+### Limits and trust boundaries
+
+Version one accepts PNG, JPEG, WebP, and GIF only. SVG and remote URLs are excluded. Default limits are 5 MiB per image, 10 images and 20 MiB aggregate image bytes per message, and 40 million intrinsic pixels per image. These deployment-varying limits are validated backend configuration and are projected to the client for fast-path guidance; host validation remains authoritative.
+
+Malformed base64, unsupported or mismatched media, truncated headers, excess bytes, excess image count, excess pixels, missing objects, and integrity mismatches return stable structured failures. Original filenames are reduced to a display basename, control characters are removed, and no local path is logged or returned to the browser.
+
+### Package and surface changes
+
+| Surface | Responsibility |
+| --- | --- |
+| `packages/attachment/attachment` | Opaque attachment identifier, image reference, limits, failures, and `ctx.attachments` service. |
+| `packages/attachment/attachment-local` | Private content-addressed storage, image-header validation, integrity verification, and configuration. |
+| `packages/llm/llm` and `packages/llm/token-meter` | Role-neutral `ImageBlock`, modality metadata, and image cost estimation. |
+| `packages/llm/llm-pi-ai` | Resolve durable supported image input into native provider content. |
+| `packages/llm/llm-deepseek` | Reject image content explicitly. |
+| `packages/host/apiproxy` and `packages/host/runtime` | Narrow upload wire, persist-before-event ordering, session-authorized reads, limits, and model preflight. |
+| `packages/client/connection` and `packages/client/runtime` | Wire types, fixture images, prompt uploads, attachment reads, and durable-reference folding. |
+| `packages/client/ui-conversation` | Per-session draft images, attachment rail, user and assistant image controls, and original preview. |
+| `packages/ui/acp` | Explicit fallback rendering for image blocks. |
+
+The attachment packages form the interface/implementation side of one capability seam. Composer behavior stays in the conversation object layer, provider conversion stays in adapters, and no change is required in `agent-loop`.
+
+### Delivery
+
+1. Land the attachment seam, role-neutral image block, image-aware token estimation, Pi-AI input conversion, DeepSeek rejection, and durable host ordering.
+2. Land the Web upload/read protocol, in-memory draft images, paste/drop rail, user and assistant history rendering, double-click preview, and assembled keyless Web coverage.
+3. Add immediate intake-time capability feedback when active model selection is consistently available to the composer.
+4. Propose file picking, generic files/PDF, audio/video, durable draft staging, output-provider certification, and reference-aware garbage collection independently.
+
+No compatibility shim is required for the pre-release prompt wire; all call sites and fixtures change with the introducing slice.
+
+## Alternatives considered
+
+### Keep every intake image in `/var` or another temporary directory
+
+Temporary storage is appropriate before send, including for a native client that receives clipboard files through the operating system. It is not appropriate after acceptance: cleanup is outside the harness's control, paths are host-specific, and resume or fork can outlive the file. The proposal permits temporary staging but copies accepted bytes into `DSH_HOME` before the event.
+
+### Persist immediately on paste or drop
+
+Immediate persistence makes drafts reload-resistant but creates durable objects before a session or message owns them, which requires quota, orphan lifetime, and cleanup policy. Version one keeps the unsent draft temporary and makes send acceptance the durability boundary.
+
+### Inline base64 in messages and session logs
+
+This duplicates binary data across RPC, events, history pages, forks, compaction, and browser storage, and invites token accounting to treat encoding text as model text. One immutable object plus small references keeps the durable representation bounded.
+
+### Use browser object URLs, local paths, or provider URLs as canonical content
+
+Object URLs expire with the document, local paths are not portable, and provider URLs may expire, track viewers, or expose credentials. They remain temporary transport or preview details only.
+
+### Use one generic `AttachmentBlock` for images, files, audio, and video
+
+Composer presentation can use a generic attachment rail, but provider semantics are modality-specific. Images are native multimodal input; PDFs may be provider files or extracted text; video may be native, sampled, or unsupported. A specific `ImageBlock` forces every consumer to handle or reject the modality explicitly.
+
+### Rely on UI capability checks or silently filter images
+
+UI state can be stale and does not protect direct SDK, ACP, replay, or uncatalogued model paths. Silent filtering changes user intent. Provider enforcement remains mandatory, while UI checks are optional earlier feedback.
+
+## Acceptance criteria
+
+- Pasting or dropping one or more supported images shows ordered removable thumbnails above both composer variants without changing textarea text; drag-over highlights the target, unsupported drops cannot navigate away, and image-only send works.
+- Unsent browser images exist only as `File` and object URLs, survive session switches in memory, do not enter `localStorage`, and are revoked after removal, accepted send, or service disposal.
+- Every accepted user image is committed below resolved `DSH_HOME` before its `user/message` event. The event contains only `ImageBlock` references and never base64 or temporary paths.
+- Structured assistant images can be represented only by a durable `ImageBlock`; a future output adapter must persist bytes before emitting the assistant event, while Markdown image URLs remain text.
+- Cold history renders user and assistant image references through the same bounded control. Double-click opens the original; Escape, backdrop, and close control dismiss it without a custom context menu.
+- Session attachment reads fail unless the same session log references the identifier. Missing or corrupt objects fail explicitly and never return unverified bytes.
+- Pi-AI emits native input images for a compatible route. DeepSeek and every non-implementing consumer return an explicit unsupported-content failure rather than dropping the block.
+- An explicitly text-only active model rejects image send before attachment persistence or session event append; unknown metadata still reaches adapter enforcement and a failed send restores the draft.
+- Keyless unit, host integration, client integration, and assembled Chromium coverage exercise persistence ordering, absence of base64 in logs, authorization, paste and drop, image-only send, historical user and assistant images, original preview, and object-URL cleanup.
+- The current production adapter set declares text-only output; output-provider certification, file picking, non-image files, video, persistent drafts, and garbage collection remain outside version one.
+
+## Risks
+
+- Durable storage grows without garbage collection. Version one chooses replay safety over premature deletion.
+- A missing or corrupt object makes exact model reconstruction fail. Failing loud preserves integrity but may prevent that session from continuing until repaired.
+- JSON-RPC base64 adds upload memory and roughly one-third encoding overhead. Version-one limits bound it; larger media needs streaming or a binary transport.
+- Unsent images do not survive reload. Durable drafts need quota and orphan cleanup rather than reusing message storage implicitly.
+- Original preview decodes more pixels than the inline control displays. Pixel limits, one clicked preview, and object-URL disposal bound but do not eliminate transient browser memory.
+- Capability metadata may be missing or stale. Host preflight improves feedback, while adapter enforcement remains authoritative.
+- A future output provider may require authenticated retrieval before an assistant image can complete, adding latency and a new failure point. Persist-before-event ordering favors replay integrity.
--- a/.agents/notes/proposed/feature/2026-07-22-web-multimodal-image-input-and-durable-attachments.zh.md
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+# Agent Note: Web 多模态图片输入与持久附件
+
+Status: proposed
+
+[English](2026-07-22-web-multimodal-image-input-and-durable-attachments.md) | 中文
+
+## 问题
+
+Web 输入区目前仅接受文本：`InputBar` 接收字符串草稿，`ConversationService.send()` 创建文本内容，宿主再把该内容转发给 agent（智能体）。用户无法粘贴图片、在发送前查看图片、提交仅含图片的提示词，也无法从历史记录中恢复已发送图片。
+
+这不只是输入区功能缺失。核心层需要持久图片内容块，提供方需要明确处理模态，会话日志则必须重建模型可见的全部内容。[此前移除图片块的决策](../../implemented/simplification/2026-07-04-drop-image-content-block.md)否决了可能静默丢失图片或将其展平的不完整设计。浏览器对象 URL、本地路径、提供方 URL 或 base64 数据都不能成为规范会话内容。
+
+[Web 客户端架构](../../implemented/architecture/2026-07-19-gui-web-client-architecture.md)要求组件保持纯粹，并将每个会话的输入区状态放在 `ctx.conversation` 中；[GUI 分层与 RPC 协议](../../implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md)则要求持久事件成为实时渲染与历史回放的共同真源。因此，图片接收、持久化、提供方转换和渲染需要遵循同一个明确的生命周期。
+
+同类产品普遍在编辑器上方设置附件栏，但存储方案各不相同。诸如 `/var/folders/.../codex-clipboard-*.png` 的 Codex 式路径适合作为接收输入时的暂存位置，却不能作为持久消息身份：操作系统可能删除文件，另一台宿主无法读取文件，恢复后的会话也不能依赖文件仍然存在。
+
+## 提案
+
+把粘贴或拖放的光栅图片作为持久附件能力的首个消费方，接入 Web 输入区。未发送文件仍是由客户端持有的临时草稿状态。宿主在追加相应消息事件前，校验并持久提交每张已接受的用户图片。生成结构化图片输出的提供方适配器在追加相应助手块前，也必须持久提交输出。规范用户内容与助手内容只包含角色无关的 `ImageBlock` 引用。
+
+第一版支持粘贴和拖放 PNG、JPEG、WebP 与 GIF，支持仅图片或混合提示词，支持渲染历史用户图片与助手图片，并支持双击预览原图。文件选择、通用文件、PDF、音频、视频、图片复制和自定义上下文菜单分别作为后续工作。
+
+### 产品行为
+
+- 粘贴或拖放一张或多张受支持的图片后，文本框上方会按顺序显示缩略图，但不会插入占位文本。文件拖入输入区时会高亮放置目标。
+- 空状态输入区与常驻输入区共用附件栏；附件栏为空时隐藏，通过横向滚动避免撑宽输入区。
+- 每个缩略图约为 72 × 72 像素，带有移除操作；双击时打开草稿原图。
+- 提示词可同时包含文本与图片，也可仅包含图片。粘贴纯文本时保持浏览器原生行为；粘贴处理器只有接受图片文件后才阻止默认行为。无论文件是否受支持，在输入区放置文件时都会阻止浏览器导航；系统会接受受支持的图片，并在本地提示哪些文件不受支持。
+- 发送失败时恢复完整的文本与图片草稿。移除、发送成功和会话作用域释放都会撤销过期的对象 URL。
+- 历史用户图片与助手图片共用一个 `MessageImage` 控件。行内图片保持固有宽高比、不放大，并限制在 240 × 240 像素的边界框内。
+- 双击消息图片会在不超出视口的模态框中打开存储的原图。按 Escape、激活关闭控件或激活背景区域都会关闭模态框并恢复焦点。
+- 第一版不覆盖浏览器上下文菜单，也不提供明确的图片复制操作。
+
+### 存储生命周期与归属
+
+持久化边界是消息被接受，而不是图片被粘贴：
+
+| 状态 | 允许的表示 | 持久性与顺序 |
+| --- | --- | --- |
+| 未发送的用户草稿 | 浏览器 `File` 加对象 URL；原生客户端可以使用 `/var/...` 等操作系统临时文件 | 临时且由客户端持有。它可能在重载或进程退出后消失，绝不出现在会话事件中。 |
+| 已接受的用户图片 | `DSH_HOME` 下的不可变对象加 `ImageAttachmentRef` | 在 `agent.send()` 或 `agent.steer()` 能够追加所属用户事件前，宿主提交每张图片。 |
+| 结构化模型图片输出 | `DSH_HOME` 下的不可变对象加 `ImageAttachmentRef` | 提供方适配器在发出已完成的图片块或助手消息事件前提交字节。事件中禁止出现临时 URL、路径和 base64。 |
+
+框架持有的 chat store 保存每个会话的草稿文本和有序附件标识符，`ConversationService` 则持有相应的浏览器专用 `File` 与对象 URL 注册表：
+
+```ts
+export {}
+
+interface ChatStoreState {
+  selection: object | null
+  draft: string
+  imageIds: string[]
+  view: string | null
+}
+
+interface ComposerAttachment {
+  id: string
+  file: File
+  previewUrl: string
+}
+```
+
+这一拆分让 UI 状态通过 slots 框架的 store 席位和绑定 actions 使用唯一的订阅路径，同时避免把不可序列化的浏览器对象写进持久 JSON。草稿文本和有序图片标识符继续使用 `localStorage`；重载后，`ConversationRoot` 会清理缺少对应运行时对象的标识符。未发送图片因此无法跨重载保留，因为浏览器 `File` 与对象 URL 不具备持久性。原生客户端可以在操作系统临时目录中暂存输入，但必须像对待浏览器对象 URL 一样对待该路径：不再需要时删除，并在消息被接受前把字节复制进持久存储。
+
+本地附件后端依次解析显式 `dshHome`、`$DSH_HOME` 和 `~/.dsh`。它把内容寻址对象存储在 `$DSH_HOME/attachments/v1/objects/<prefix>/<sha256>` 下，并为目录和文件设置仅所有者可访问的权限。服务先写入并同步临时文件，再以原子方式发布，之后才返回引用。内容摘要编码在不透明的 `sha256:<digest>` 标识符中，每次读取都会校验摘要、媒体类型、字节长度、宽度和高度。
+
+第一版不对存储执行自动删除。已发送的用户图片和模型生成图片会一直保留，以供历史记录、恢复和 fork 使用。按引用感知的垃圾回收需要单独设计，因为仅按时间清理可能删除仍被持久会话引用的数据。
+
+### 持久内容与提示词协议
+
+附件服务边界公开不可变图片写入和经过校验的读取操作。规范元数据刻意比通用文件记录更窄：
+
+```ts
+import type { Branded } from '@deepseek-ai/dsh-brand'
+
+type AttachmentId = Branded<'AttachmentId'>
+
+interface ImageAttachmentRef {
+  attachmentId: AttachmentId
+  mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
+  bytes: number
+  width: number
+  height: number
+  name?: string
+}
+
+interface ImageBlock {
+  type: 'image'
+  attachment: ImageAttachmentRef
+}
+```
+
+`ImageBlock` 加入可合并扩展的核心 `ContentBlockMap`，在用户内容和助手内容中都有效。它绝不携带 base64、对象 URL、文件系统路径或提供方持有的定位符。因此，会话事件与不可变对象存储足以共同重建模型可见的确切图片。
+
+浏览器无法生成持久引用，因此 `session.prompt` 接受范围狭窄的接收联合类型，而不是规范 `ContentBlock[]`：
+
+```ts
+export {}
+
+type PromptInputPart =
+  | { type: 'text'; text: string }
+  | {
+      type: 'image'
+      mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
+      data: string
+      name?: string
+    }
+```
+
+Base64 只跨越一次 JSON-RPC，并在持久化后丢弃。宿主会校验规范 base64、图片数量、总字节数、单张图片字节数、与魔数字节一致的 MIME、固有尺寸和解码像素数。只有每张图片都成功后，宿主才会用规范化文本和持久图片块调用 agent。失败时不追加用户事件，也不公开任何附件路径或原始字节。
+
+`session.attachment` 是只读且限定于会话作用域的端点。只有该会话中的持久事件引用了所请求的附件标识符，宿主才提供字节。客户端在服务生命周期内，以会话和附件标识符为键缓存生成的对象 URL，并在释放时撤销它。
+
+### 模型能力与提供方行为
+
+模型目录项增加可选且可合并扩展的输入与输出模态声明。缺少声明表示未知；声明存在但不含 `image`，则明确表示不支持图片。
+
+宿主是权威的前置检查边界。如果所选模型明确排除图片输入，宿主会在写入任何附件或事件前拒绝提示词，客户端则恢复草稿。能力未知时继续进入适配器强制检查，使未收录的模型标识符仍然可用。在所有 Web 入口路径都能一致公开模型选择后，可以在 UI 中增加粘贴时立即拒绝的反馈。
+
+Pi-AI 适配器是首条视觉输入路径：它通过 `ctx.attachments` 解析每个持久引用，并且仅为声明支持图片输入的模型生成提供方原生图片内容。手写 DeepSeek 适配器遇到请求中任何位置的图片时都会抛出类型化的 `UNSUPPORTED_CONTENT` 错误，包括嵌套工具结果中的图片。任何适配器都不得将图片展平或跳过。
+
+核心层支持结构化助手图片块，但当前没有任何生产提供方路径通过图片输出认证。未来任何支持输出的适配器都必须在有界的大小和时间策略下获取提供方字节，通过同一个附件服务校验并持久化字节，之后才能以原子方式发布 `ImageBlock`。助手 Markdown 中的 URL 仍是文本，绝不自动下载。
+
+token 估算根据图片尺寸计量，但不把 base64 或附件定位符作为文本计数。提供方返回的用量仍是权威值。在 ACP（Agent Client Protocol）接口原生支持图片前，ACP 会渲染明确的图片标记，而不是静默省略该块。
+
+### 历史渲染与原图预览
+
+历史记录折叠会在用户消息和助手消息中保留 `ImageBlock`。用户图片在文本上方靠尾端对齐；助手图片在叙述流中靠前端对齐。`MessageImage` 根据记录的尺寸派生稳定的行内边界框，通过会话授权加载器解析字节，使用 `object-fit: contain`，并将对象缺失或损坏转换为可重试的错误控件。
+
+输入区缩略图和每个 `MessageImage` 各自持有临时原图预览状态，并调用同一个纯 `ImageLightbox`。模态框使用已经解析的原始对象 URL，只限制显示尺寸；它会聚焦关闭控件，并在关闭时把焦点恢复到先前的目标。
+
+### 限制与信任边界
+
+第一版仅接受 PNG、JPEG、WebP 和 GIF。不接受 SVG 和远程 URL。默认限制为每张图片 5 MiB、每条消息 10 张图片和 20 MiB 图片总字节数，以及每张图片 4,000 万个固有像素。这些随部署变化的限制属于经过校验的后端配置，并会投影给客户端以提供快速路径指引；宿主校验仍是权威结果。
+
+格式错误的 base64、不支持或不匹配的媒体、截断的文件头、超出字节限制、超出图片数量、超出像素限制、对象缺失和完整性不匹配都会返回稳定的结构化错误。原始文件名只保留用于显示的末段，控制字符会被移除，并且任何本地路径都不会写入日志或返回浏览器。
+
+### 包与接口变更
+
+| 接口 | 职责 |
+| --- | --- |
+| `packages/attachment/attachment` | 不透明附件标识符、图片引用、限制、错误和 `ctx.attachments` 服务。 |
+| `packages/attachment/attachment-local` | 私有内容寻址存储、图片头校验、完整性校验和配置。 |
+| `packages/llm/llm` 和 `packages/llm/token-meter` | 角色无关的 `ImageBlock`、模态元数据和图片成本估算。 |
+| `packages/llm/llm-pi-ai` | 将持久且受支持的图片输入解析为提供方原生内容。 |
+| `packages/llm/llm-deepseek` | 明确拒绝图片内容。 |
+| `packages/host/apiproxy` 和 `packages/host/runtime` | 范围狭窄的上传协议、先持久化再追加事件的顺序、会话授权读取、限制和模型前置检查。 |
+| `packages/client/connection` 和 `packages/client/runtime` | 协议类型、fixture（测试前置数据）图片、提示词上传、附件读取和持久引用折叠。 |
+| `packages/client/ui-conversation` | 每个会话的草稿图片、附件栏、用户与助手图片控件和原图预览。 |
+| `packages/ui/acp` | 图片块的明确兜底渲染。 |
+
+附件包（package）构成一个能力服务边界的接口与实现侧。输入区行为留在会话对象层，提供方转换留在适配器中，无需修改 `agent-loop`。
+
+### 交付
+
+1. 交付附件服务边界、角色无关的图片块、图片感知的 token 估算、Pi-AI 输入转换、DeepSeek 拒绝和宿主侧的持久化顺序。
+2. 交付 Web 上传与读取协议、内存草稿图片、支持粘贴与拖放的附件栏、用户与助手历史图片渲染、双击预览，以及组装后无需密钥的 Web 覆盖。
+3. 在输入区能够一致获取当前模型选择后，增加接收图片时立即提供的能力反馈。
+4. 分别为文件选择、通用文件与 PDF、音频与视频、持久草稿暂存、输出提供方认证和按引用感知的垃圾回收提出方案。
+
+预发布提示词协议不需要兼容包装层；引入相应切片时会同时修改所有调用点和 fixture。
+
+## 曾考虑的替代方案
+
+### 将每张粘贴图片保留在 `/var` 或其他临时目录中
+
+临时存储适合在发送前使用，也适合通过操作系统接收剪贴板文件的原生客户端。但它不适合在消息被接受后继续使用：清理不在 harness 的控制范围内，路径因宿主而异，恢复或 fork 后的会话也可能比文件存在得更久。提案允许临时暂存，但会在追加事件前将已接受的字节复制进 `DSH_HOME`。
+
+### 粘贴或拖放后立即持久化
+
+立即持久化可以让草稿在重载后继续存在，但会在会话或消息持有对象前就创建持久对象，因此必须定义配额、遗留对象生命周期和清理策略。第一版保持未发送草稿为临时状态，并把发送被接受作为持久性边界。
+
+### 在消息与会话日志中内联 base64
+
+这种方式会在 RPC、事件、历史分页、fork、压缩（compaction）和浏览器存储中复制二进制数据，还会诱使 token 计量把编码文本当成模型文本。单一不可变对象配合小型引用，可以让持久表示保持有界。
+
+### 使用浏览器对象 URL、本地路径或提供方 URL 作为规范内容
+
+对象 URL 会随文档失效，本地路径不可移植，提供方 URL 则可能过期、跟踪查看者或暴露凭据。它们只能作为临时传输或预览细节存在。
+
+### 用一个通用 `AttachmentBlock` 表示图片、文件、音频和视频
+
+输入区展示可以使用通用附件栏，但提供方语义取决于具体模态。图片是原生多模态输入；PDF 可能是提供方文件或提取后的文本；视频可能由模型原生支持、抽帧处理或不受支持。特定的 `ImageBlock` 会迫使每个消费方明确处理或拒绝该模态。
+
+### 依赖 UI 能力检查或静默过滤图片
+
+UI 状态可能陈旧，也无法保护直接 SDK、ACP、回放或未收录模型的路径。静默过滤会改变用户意图。提供方强制检查仍是必需项，UI 检查则是可选的提前反馈。
+
+## 验收标准
+
+- 在两种输入区中粘贴或拖放一张或多张受支持的图片时，文本框上方会按顺序显示可移除缩略图，且不更改文本框内容；拖入时会高亮目标，放置不支持的文件也不会触发页面跳转，仅图片的发送可正常工作。
+- 未发送的浏览器图片仅以 `File` 与对象 URL 的形式存在，可以在内存中跨会话切换保留，不进入 `localStorage`，并在移除、发送被接受或服务释放后撤销。
+- 每张已接受的用户图片都会提交到解析所得 `DSH_HOME` 下，之后才会追加相应的 `user/message` 事件。事件只包含 `ImageBlock` 引用，绝不包含 base64 或临时路径。
+- 结构化助手图片只能由持久 `ImageBlock` 表示；未来的输出适配器必须在发出助手事件前持久化字节，而 Markdown 图片 URL 仍是文本。
+- 冷启动历史记录通过同一个有界控件渲染用户与助手图片引用。双击打开原图；Escape、激活背景区域和激活关闭控件可以关闭预览，且不提供自定义上下文菜单。
+- 除非同一个会话日志引用了该标识符，否则会话附件读取会失败。对象缺失或损坏会明确失败，绝不返回未经校验的字节。
+- Pi-AI 会为兼容路径生成提供方原生输入图片。DeepSeek 与所有未实现该能力的消费方返回明确的不支持内容错误，而不是丢弃该块。
+- 明确仅支持文本的当前模型会在持久化附件或追加会话事件前拒绝图片发送；未知元数据仍会到达适配器强制检查，发送失败则恢复草稿。
+- 无需密钥的单元测试、宿主集成测试、客户端集成测试和组装应用的 Chromium 覆盖会验证持久化顺序、日志中不含 base64、授权、粘贴与拖放、仅图片发送、历史用户与助手图片、原图预览和对象 URL 清理。
+- 当前生产适配器集合声明仅支持文本输出；输出提供方认证、文件选择、非图片文件、视频、持久草稿和垃圾回收不在第一版范围内。
+
+## 风险
+
+- 持久存储会在没有垃圾回收时持续增长。第一版选择回放安全，而不是过早删除。
+- 对象缺失或损坏会让模型请求无法精确重建。明确失败可以保持完整性，但在修复前可能阻止该会话继续运行。
+- JSON-RPC base64 会增加上传内存，并带来约三分之一的编码开销。第一版的限制可以约束开销；更大的媒体需要流式传输或二进制传输协议。
+- 未发送图片无法跨重载保留。持久草稿需要配额和遗留对象清理，而不是隐式复用消息存储。
+- 原图预览解码的像素多于行内控件显示的像素。像素限制、一次只打开一个预览和对象 URL 释放可以约束但无法消除浏览器瞬时内存占用。
+- 能力元数据可能缺失或陈旧。宿主前置检查可以改善反馈，适配器强制检查仍是权威结果。
+- 未来输出提供方可能需要经过身份认证的下载，助手图片才能完成，这会增加延迟与新的故障点。先持久化再追加事件的顺序优先保障回放完整性。