fix(mcp): project image results through durable attachments
This commit is contained in:
Tianyi Cui
@@ -2,5 +2,5 @@
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# side as of the last confirmed-consistent state. Both languages carry equal authority;
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# after editing either side, bring the other along and re-record with:
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# pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-07-07-mcp-client-plugin.md
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2026-07-07-mcp-client-plugin.md: 24828586645778294ad7bdafc6fd13a9bfb6745f
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2026-07-07-mcp-client-plugin.zh.md: 8f58c9359ca8447717cc353f97f1333370fa6fda
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2026-07-07-mcp-client-plugin.md: 9d1e12e23ee1140f8827612cc5156185959ccd4f
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2026-07-07-mcp-client-plugin.zh.md: 4d41be9d96e64d5e12a318afe087e44df21b5009
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@@ -141,11 +141,11 @@ Tools are never silently skipped; which tools are available never depends on plu
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A unified `execute` handler for all tools from one MCP server:
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1. Resolve `rawName` (the executor closes over it) and call `client.callTool({ name: rawName, arguments }, { signal: exec.signal })` with the configured timeout — the public name is never sent to the server.
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2. Map the result:
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- Multiple `text` content blocks → join with `'\n'` into a single `TextBlock` (required: `flattenText` uses `join('')` without separator, so multiple blocks would lose inter-block boundaries).
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- `image` content blocks → discard with a `ctx.logger.warn` (the harness has no image content block type; [drop-image Agent Note](../simplification/2026-07-04-drop-image-content-block.md)).
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- `isError: true` → map to the harness `isError` result path (`{ content: [...], isError: true }`).
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3. Cancellation: `exec.signal` (from the agent loop's cancel) is passed through to the MCP SDK's `callTool`, which sends `$/cancelRequest` to the server.
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2. Preserve canonical success as `{ content: JsonValue[], structuredContent? }`; complete MCP JSON blocks remain the programmatic/Code Mode value. `isError: true` throws before any image persistence so the registry owns the failure path.
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3. Prepare a separate ordered Native projection. Text runs join with `'\n'`; resource links preserve name and URI as text; audio, embedded resources, malformed blocks, and unknown types become explicit diagnostics. If any image exists, the bridge strictly decodes the complete batch, resolves the calling agent's latest exact route, requires an attachment store plus explicit model image input, and delegates all-member validation and ordered persistence to `AttachmentStore.saveImages()`. Any decode, capability, or storage refusal renders every image as diagnostic text and returns no partial references.
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4. Keep `output.render` synchronous and pure. The executor stages its richer projection in a generation-local `WeakMap` keyed by the exact execution; `finalizeContent` installs it only when the registry's post-execute result still has the original canonical value and fallback content. A policy block, value replacement, or content replacement remains authoritative, and a re-sync cannot let an older generation consume new execution state.
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5. Code Mode receives the untouched canonical value. Its generic dispatch bridge defers a successful final content sequence containing an image through the outer `run_code` result, so MCP requires no private parent-token special case.
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6. Cancellation: `exec.signal` (from the agent loop's cancel) is passed through to the MCP SDK's `callTool`, exact-model lookup, and the pre-storage gate.
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### Subprocess environment (stdio transport)
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@@ -189,13 +189,25 @@ Rejected. The remote name is untrusted, non-unique across deployments, and chang
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Rejected. `flattenText()` in the DeepSeek serializer uses `join('')` (no separator) when flattening `ContentBlock[]` to wire format. Multiple text blocks would silently lose inter-block boundaries — a correctness bug. All existing tools return a single TextBlock; the MCP bridge follows suit.
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### Replace the canonical MCP result with core `ContentBlock[]`
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Rejected. Programmatic callers need protocol-complete MCP blocks and `structuredContent`, while Native consumers need durable core images rather than base64. One canonical protocol value plus a separate projection preserves both contracts.
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### Add a generic RichContent service or perform I/O in `output.render`
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Rejected. Core already owns the role-neutral content vocabulary, and a second service would duplicate its logging and ordering contracts. `output.render` is pure, synchronous, and replayable, so attachment I/O belongs in async execution with an exact finalization handoff.
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### Let each image-returning tool special-case Code Mode parents
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Rejected. That couples leaf tools to composite-tool internals and misses future rich tools. The generic Code Mode bridge observes the final post-policy content and forwards image-bearing results uniformly.
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## Testing
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Coverage is named per tier; each behavior lives at the cheapest tier that can express it.
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- **Unit** (`tests/mcp-client.spec.ts`, `tests/apply.spec.ts`, mocked MCP SDK): the `publicToolName` algorithm (clean, normalize, truncate-and-hash, determinism, distinct-identity separation), raw-vs-public wire discipline, cross-server and native-tool coexistence, duplicate-`serverName` load failure and reservation release, invalid-tool-list rejection, generation swap/rollback, failed-re-sync retention, result mapping, cancellation, config schema validation. 100% per-file coverage gates the package.
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- **E2E** (`tests/mcp-client.e2e.ts`, keyless): the real MCP protocol against the in-repo fixture server, `@modelcontextprotocol/server-everything`, and `@modelcontextprotocol/server-filesystem` over stdio, and against an in-process `StreamableHTTPServerTransport` server over Streamable HTTP — discovery under the namespace, dotted-name normalization end to end, execution round-trips, duplicate-`serverName` rejection, disposal.
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- **Snapshot**: deliberately none. MCP tools introduce no new presentation shape — they register as raw `ToolDefinition`s and UI consumers use the generic-card fallback already pinned by their presentation suites. Adding an MCP server to a runnable snapshot composition would mutate its pinned system-prompt fixture and make every replay depend on spawning an external MCP server process for no new behavior. If a later change gives MCP tools their own render intent, that change names its snapshot coverage then.
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- **Unit** (`tests/mcp-client.spec.ts`, `tests/apply.spec.ts`, mocked MCP SDK): the `publicToolName` algorithm (clean, normalize, truncate-and-hash, determinism, distinct-identity separation), raw-vs-public wire discipline, cross-server and native-tool coexistence, duplicate-`serverName` load failure and reservation release, invalid-tool-list rejection, generation swap/rollback, failed-re-sync retention, lossless canonical results, mixed rich ordering, atomic malformed batches, exact capability/store refusal, explicit non-image diagnostics, post-execute policy precedence, cancellation, and config schema validation. 100% per-file coverage gates the package.
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- **E2E** (`tests/mcp-client.e2e.ts`, keyless): the real MCP protocol against the in-repo fixture server, `@modelcontextprotocol/server-everything`, and `@modelcontextprotocol/server-filesystem` over stdio, and against an in-process `StreamableHTTPServerTransport` server over Streamable HTTP — discovery under the namespace, dotted-name normalization end to end, execution round-trips, durable image save/read with base64 retained only in the canonical value, explicit refusal without an image route, duplicate-`serverName` rejection, and disposal.
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- **Snapshot**: the assembled ACP example owns the transport-visible inline-image transcript and the Code Mode image-forwarding transcript; package E2E owns the real MCP wire because the runnable snapshot must stay keyless and deterministic rather than spawning third-party server packages. MCP tool cards still use the generic-card fallback and require no package-specific UI snapshot.
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## Consequences
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@@ -206,3 +218,4 @@ Coverage is named per tier; each behavior lives at the cheapest tier that can ex
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- **Tool schema quality**: MCP servers may expose poorly-described tools (vague descriptions, incomplete JSON schemas). The harness passes them through as-is — garbage-in-garbage-out; that is the server author's responsibility, not the bridge's.
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- **Stdio process management**: a misbehaving MCP server that ignores signals could wedge dispose. The Cordis fiber disposal has bounded quiescence; a stuck transport eventually times out at the framework level.
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- Crash recovery is automatic within the [reconnect budget](2026-08-06-mcp-client-auto-reconnect.md); manual reload remains the path after exhaustion or with `reconnect.enabled: false`.
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- Image payloads can enter model context only through the shared durable attachment store and an exact positive route capability. Audio and embedded-resource payloads remain execution-local with explicit diagnostics.
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@@ -141,11 +141,11 @@ MCP 仅保证工具名在[单个服务器内](https://modelcontextprotocol.io/sp
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为来自同一个 MCP 服务器的所有工具提供统一的 `execute` 处理器：
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1. 解析 `rawName`（执行器闭包持有它），以配置的超时时间调用 `client.callTool({ name: rawName, arguments }, { signal: exec.signal })`——公开名称永远不发送给服务器。
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2. 映射结果：
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- 多个 `text` 内容块 → 以 `'\n'` 连接为单个 `TextBlock`（之所以必须这样做，是因为 `flattenText` 使用无分隔符的 `join('')`，多个内容块会丢失块间边界）。
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- `image` 内容块 → 丢弃并 `ctx.logger.warn`（harness 没有图片内容块类型；[删除图片 Agent Note](../simplification/2026-07-04-drop-image-content-block.md)）。
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- `isError: true` → 映射到 harness 的 `isError` 结果路径（`{ content: [...], isError: true }`）。
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3. 取消：`exec.signal`（来自 agent loop（智能体循环）的取消）透传给 MCP SDK 的 `callTool`，后者向服务器发送 `$/cancelRequest`。
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2. 把规范成功值保留为 `{ content: JsonValue[], structuredContent? }`；完整 MCP JSON 块仍是程序化调用／Code Mode 值。`isError: true` 会在持久化任何图片前抛出，使失败路径归注册表所有。
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3. 另行准备有序 Native 投影。连续文本块以 `'\n'` 连接；资源链接以文本保留名称和 URI；音频、嵌入资源、格式错误的块和未知类型成为明确诊断。只要存在图片，桥接层就严格解码完整批次，解析调用 agent 的最新确切路由，要求附件存储以及模型明确支持图片输入，再把全成员校验和有序持久化委托给 `AttachmentStore.saveImages()`。任何解码、能力或存储拒绝都会把全部图片渲染为诊断文本，且不返回部分引用。
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4. 保持 `output.render` 同步且纯净。执行器把更丰富的投影暂存在按同步世代创建、以确切执行为键的 `WeakMap` 中；只有注册表的 post-execute 结果仍保留原规范值和兜底内容时，`finalizeContent` 才安装该投影。策略阻止、值替换或内容替换仍具有权威性，重新同步也无法让旧世代消费新执行状态。
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5. Code Mode 接收未改动的规范值。其通用分发桥接层会把包含图片的成功最终内容序列经外层 `run_code` 结果延后，因此 MCP 无需私有父 token 特例。
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6. 取消：`exec.signal`（来自 agent loop 的取消）透传给 MCP SDK 的 `callTool`、确切模型查询和存储前门禁。
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### 子进程环境（stdio 传输）
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@@ -189,13 +189,25 @@ v1 否决。它能防止跨服务器冲突，但无法将 MCP 注册与原生 ha
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否决。DeepSeek 序列化器中的 `flattenText()` 在将 `ContentBlock[]` 扁平化为协议格式（wire format）时使用 `join('')`（无分隔符）。多个 text 块会静默丢失块间边界——这是正确性缺陷。所有现有工具返回单个 TextBlock；MCP 桥接遵循同一做法。
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### 用核心 `ContentBlock[]` 替换规范 MCP 结果
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不予采用。程序化调用方需要协议完整的 MCP 块和 `structuredContent`，Native 消费方则需要持久核心图片而不是 base64。一份规范协议值加一份独立投影可以同时保留两项契约。
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### 添加通用 RichContent 服务，或在 `output.render` 中执行 I/O
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不予采用。核心已经拥有角色无关的内容词汇，第二套服务会重复其日志与顺序契约。`output.render` 必须纯净、同步且可回放，因此附件 I/O 属于异步执行，再经确切的最终化交接安装结果。
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### 让每个返回图片的工具分别特殊处理 Code Mode 父调用
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不予采用。这会把叶子工具与组合工具内部机制耦合，并漏掉未来丰富工具。通用 Code Mode 桥接层观察最终 post-policy 内容，统一转发含图片结果。
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## 测试
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覆盖范围按层级列出；每项行为都放在能够表达它的最低成本层级。
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- **单元测试**（`tests/mcp-client.spec.ts`、`tests/apply.spec.ts`，mock MCP SDK）：`publicToolName` 算法（干净名称、规范化、截断加 hash、确定性、不同标识的分离）、raw 与 public 的协议纪律、跨服务器与原生工具共存、重复 `serverName` 加载失败与预留释放、无效工具列表拒绝、注册代切换/回滚、重新同步失败时保留上一代注册、结果映射、取消、配置 schema 校验。100% 逐文件覆盖率门禁约束该包。
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- **E2E**（`tests/mcp-client.e2e.ts`，无需密钥）：使用真实 MCP 协议对接仓库内的 fixture（测试前置数据）服务器、`@modelcontextprotocol/server-everything` 和 `@modelcontextprotocol/server-filesystem`（stdio 传输），以及进程内 `StreamableHTTPServerTransport` 服务器（Streamable HTTP 传输）——命名空间下的发现、带点号名称的端到端规范化、执行往返、重复 `serverName` 拒绝、dispose。
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- **快照**：刻意不做。MCP 工具不引入新的展示形态——它们以原始 `ToolDefinition` 注册，UI 消费方使用各自展示测试套件已固定的通用卡片兜底。将 MCP 服务器添加到某个可运行的快照组合会改变其已固定的系统提示词 fixture，且使每次回放依赖于 spawn 外部 MCP 服务器进程，而新增行为为零。如果后续变更为 MCP 工具引入专属渲染意图，该变更届时自行声明快照覆盖。
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- **单元测试**（`tests/mcp-client.spec.ts`、`tests/apply.spec.ts`，mock MCP SDK）：`publicToolName` 算法（干净名称、规范化、截断加 hash、确定性、不同标识的分离）、raw 与 public 的协议纪律、跨服务器与原生工具共存、重复 `serverName` 加载失败与预留释放、无效工具列表拒绝、注册代切换/回滚、重新同步失败时保留上一代注册、无损规范结果、丰富内容混合顺序、格式错误批次原子性、确切能力／存储拒绝、明确的非图片诊断、post-execute 策略优先级、取消，以及配置 schema 校验。100% 逐文件覆盖率门禁约束该包。
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- **E2E**（`tests/mcp-client.e2e.ts`，无需密钥）：使用真实 MCP 协议对接仓库内的 fixture（测试前置数据）服务器、`@modelcontextprotocol/server-everything` 和 `@modelcontextprotocol/server-filesystem`（stdio 传输），以及进程内 `StreamableHTTPServerTransport` 服务器（Streamable HTTP 传输）——命名空间下的发现、带点号名称的端到端规范化、执行往返、持久图片保存／读取且 base64 只保留在规范值中、缺少图片路由时明确拒绝、重复 `serverName` 拒绝，以及 dispose。
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- **快照**：组装后的 ACP 示例负责传输可见的内联图片 transcript 与 Code Mode 图片转发 transcript；包 E2E 负责真实 MCP 协议，因为可运行快照必须保持无密钥且确定，而不是 spawn 第三方服务器包。MCP 工具卡片仍使用通用卡片兜底，无需包专属 UI 快照。
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## 后果
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@@ -206,3 +218,4 @@ v1 否决。它能防止跨服务器冲突，但无法将 MCP 注册与原生 ha
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- **工具 schema 质量**：MCP 服务器可能暴露描述不佳的工具（模糊的描述、不完整的 JSON Schema）。harness 原样透传——垃圾进垃圾出；这是服务器作者的责任，不是桥接的。
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- **Stdio 进程管理**：行为异常的 MCP 服务器如果忽略信号，可能卡住 dispose。Cordis fiber 的 dispose 具有有界的完全停稳过程；卡住的传输层最终会在框架层面超时。
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- 崩溃恢复在[重连预算](2026-08-06-mcp-client-auto-reconnect.md)内自动进行；耗尽后或配置 `reconnect.enabled: false` 时回退为手动重新加载。
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- 图片载荷只有通过共享持久附件存储和确切正向路由能力，才能进入模型上下文。音频与嵌入资源载荷仍只存在于执行局部，并附带明确诊断。
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