Paged-Context-Protocol (PCP) - v0.7.0-draft

A model-agnostic protocol for deciding what user-owned information enters model attention, when it enters, and with what identity and evidence.

一个模型无关的上下文分页协议，用于决定用户拥有的信息何时进入模型注意力，以及它以什么身份、 依据和范围进入。

定位 / Overview

尖端模型已经能够搜索文件、调用工具并管理较长的当前上下文，但跨会话、跨项目和跨模型的信息 连续性仍然通常依赖粗粒度压缩或封闭的产品 Memory。对于长期、高密度内容，问题不只是“能否存下”， 而是能否在需要时准确找到、验证来源，并只将当前任务真正需要的部分放入有限注意力。

Frontier models can search files, call tools, and manage long active contexts, yet continuity across sessions, projects, and models is still commonly reduced to coarse summaries or closed product Memory. For long-lived, high-density work, the problem is not only whether information can be stored, but whether the right material can be found, traced, and selectively admitted into finite attention.

**PCP 定义一个用户拥有、模型无关的信息空间，以及它与模型注意力之间的分页边界。**它不是某个 特定的 context manager、Memory 产品或 Storage 格式，也不要求把所有历史塞进同一个提示词。 在 PCP 中，Context 是跨时间存在的信息连续体；模型当前窗口只是一个临时 working set。

PCP defines a user-owned, model-independent information space and the paging boundary between that space and model attention. It is not a particular context manager, Memory product, or Storage format, and it does not require all history to be packed into one prompt. Context is an information continuum across time; the model's active window is only a temporary working set.

Source / Event
  -> stable Page + immutable Revision       (identity and storage)
  -> Relation / Provenance / Summary        (organization and evidence)
  -> Search / Read / Projection             (selection and materialization)
  -> Active working context                 (model attention)

协议核心 / Protocol Core

• Page 与 Revision / Page and Revision：Page 是稳定语义对象；Revision 是不可变内容快照。 原始 Page 通常为 sealed，维护型 Page 可以是 revisioned。/ A Page is a stable semantic object; a Revision is an immutable content snapshot. Raw Pages are normally sealed, while maintained Pages may be revisioned.
• Scope 与 Access / Scope and Access：统一地址空间不等于全局注入。搜索、读取、派生和写入都受 Scope 与服务端注入的访问身份约束。/ A unified address space is not global injection. Search, read, derivation, and write operations remain constrained by Scope and a server-injected access identity.
• Relation 与 Provenance / Relation and Provenance：Relation 连接稳定 Page；关系依据和来源链引用 精确 Revision。时间相邻或文本相似不会自动成为领域关系。/ Relations connect stable Pages, while relation evidence and provenance refer to exact Revisions. Temporal adjacency or textual similarity does not automatically become a domain edge.
• Summary 与 Validity / Summary and Validity：Summary 是可选、稀疏、可追溯的派生 Page，不是每条 内容的强制层级；Validity 记录内容当前是否仍适用。/ Summaries are optional, sparse, traceable derived Pages rather than a mandatory tier for every item. Validity records whether information remains applicable.
• Search、Read 与 Projection / Search, Read, and Projection：检索先返回可识别候选，再按需读取 Summary、Payload、Sources、Relations、History 等投影；模型或 Host 决定查询路径和进入注意力的时机。 / Retrieval returns identifiable candidates before selected projections such as Summary, Payload, Sources, Relations, or History are read. The model or Host chooses the query path and admission timing.
• Consolidation 与 Retention / Consolidation and Retention：多个当前语义 Page 可以经显式整合收缩为 canonical Page；历史 Revision 只在依赖、租约和保留规则允许时回收。/ Multiple current semantic Pages may be explicitly contracted into a canonical Page. Historical Revisions are collected only when dependencies, leases, and retention rules permit.

PCP 不规定固定 Router、Intent Focus、四级变焦、Chain-of-Thought、XML 流程或模型状态机。模型如何 决定写入、搜索、总结、整合和物化，属于 Model Client 或 Host 策略；协议只提供可互操作、可追溯、 受约束的对象与接口。

PCP does not prescribe a fixed Router, Intent Focus, zoom hierarchy, Chain-of-Thought, XML flow, or model state machine. Decisions to write, search, summarize, consolidate, and materialize remain Model Client or Host policy; the protocol supplies interoperable, traceable, and constrained objects and interfaces.

当前状态 / Current Status

v0.7.0-draft 是当前协议草案。它在不可变 Revision 之上恢复稳定 Page 身份，并加入显式 Scope、 Provenance、Relation、稀疏 Summary、Validity、consolidation 与 Revision retention 语义。

v0.7.0-draft is the current protocol draft. It restores stable Page identity above immutable Revisions and defines explicit Scope, Provenance, Relation, sparse Summary, Validity, consolidation, and Revision-retention semantics.

仓库现在同时包含一个可运行的 Rust 参考实现。它用于验证协议边界，不把 SQLite、某种检索算法、 某个模型或 Host 的操作习惯提升为协议要求。

The repository now includes a working Rust reference implementation. It validates the protocol boundary without making SQLite, one retrieval algorithm, one model, or a Host workflow normative.

Crate	职责 / Role
pcp-core	核心对象、请求、投影与 capability 类型 / Core objects, requests, projections, and capability types
pcp-store	携带 AccessSession 的数据库无关 Store 契约 / Database-independent Store contract with AccessSession
pcp-client	面向 Host 的传输无关 PcpApi 与 embedded client / Transport-independent PcpApi and embedded client
pcp-rpc	本地 Unix socket 协议、远端 client 与 server transport / Local Unix-socket wire, remote client, and server transport
pcp-sqlite	SQLite Page/Revision Store、迁移、检索、审计与回收 / SQLite Page/Revision Store, migrations, retrieval, audit, and retention
pcp-runtime	固定身份的多端点 broker 与可选维护协调器 / Fixed-identity multi-endpoint broker and optional maintenance coordinator
pcp-cli	检查、检索、读取、导出、整合与保留操作 / Inspection, retrieval, read, export, consolidation, and retention operations
pcp-mcp	基于官方 Rust MCP SDK 的本地 stdio 工具服务器 / Local stdio tool server built on the official Rust MCP SDK
pcp-console	独立、只读的本地 Web Inspector / Independent read-only local Web Inspector

已实现 / Implemented

• 稳定 Page、不可变 Revision、sealed/revisioned、CAS 修订与 v0.6 数据幂等迁移。 / Stable Pages, immutable Revisions, sealed/revisioned behavior, CAS updates, and idempotent migration from v0.6 data.
• head-only 默认检索，auto、exact、text、graph、temporal 模式，以及有界 Projection 读取。 / Head-only default retrieval, auto, exact, text, graph, and temporal modes, plus bounded Projection reads.
• Summary、Validity、Relation、Provenance、consolidation 与访问审计。 / Summary, Validity, Relation, Provenance, consolidation, and access audit.
• 固定接入身份的 embedded/RPC client、Runtime broker、CLI、MCP 与只读 Console。 / Fixed-identity embedded and RPC clients, Runtime broker, CLI, MCP, and read-only Console.
• 确定性 Revision 保留规划、有限租约、受保护的显式回收，以及多维 Health 诊断。 / Deterministic Revision-retention planning, finite leases, protected explicit collection, and multidimensional Health diagnostics.

尚未实现 / Not Yet Implemented

Alias 与 durable Page deletion 当前会通过 Capabilities 报告为不可用，cold storage 也尚未实现。 参考实现不内置语义模型或 Router；部署方可以在协议接口之上选择本地模型、远端模型、全文检索 或组合策略。

Aliases and durable Page deletion are currently reported as unavailable through Capabilities, and cold storage is not yet implemented. The reference implementation does not embed a semantic model or Router; deployments may compose local models, remote models, full-text retrieval, or other strategies above the protocol interface.

快速开始 / Quick Start

当前 workspace 使用 Rust 2024 edition： The workspace currently uses Rust 2024 edition:

cargo test --workspace

PCP_STORE_PATH=data/context.sqlite3 \
  cargo run -p pcp-cli -- doctor

PCP_STORE_PATH=data/context.sqlite3 \
  cargo run -p pcp-cli -- retention-plan 30 2 100

retention-plan 只是 dry run：三个参数依次表示最小保留天数、每个 Page 至少保留的最近 Revision 数， 以及返回的候选上限。实际回收使用独立的 retention-collect --confirm，并在提交前重新规划精确 Revision ID。

retention-plan is a dry run. Its arguments are minimum age in days, recent Revisions retained per Page, and candidate limit. Physical collection uses the separate retention-collect --confirm command and replans exact Revision IDs before submission.

部署 / Deployment

PcpApi 是消费侧边界。同一个 Host 可以直接嵌入 Store，也可以通过可选的 Runtime 使用独立生命周期 和固定服务端身份；CLI 与 MCP 均可连接这两种形态。

PcpApi is the consumer boundary. A Host may embed a Store directly or use the optional Runtime for an independent lifecycle and fixed server-side identities. Both CLI and MCP can connect through either shape.

Host --------> PcpApi --> EmbeddedPcpClient --> PcpStore
                    `----> RemotePcpClient ----> pcp-runtime --> PcpStore
Codex -------> MCP -----> PcpApi
Operator ----> CLI -----> PcpApi

多 client 部署可以从 examples/runtime.toml 启动 broker： For multiple clients, start the broker from examples/runtime.toml:

cargo build --release -p pcp-runtime
target/release/pcp-runtime --config examples/runtime.toml

每个 Unix socket 对应一个由 Runtime 注入的固定 Principal，请求不能自选身份。socket mode 为 0600； 这是本地用户边界，不能防御已经以同一 OS 用户运行的恶意进程。需要强隔离时，应使用独立端点、 最小 Scope 和独立模型上下文，因为 Storage 权限无法撤回已经进入模型窗口的信息。

Each Unix socket maps to one fixed Principal injected by Runtime; requests cannot choose their own identity. Socket mode is 0600. This is a local-user boundary, not protection from a hostile process already running as the same OS user. Strong isolation requires separate endpoints, minimal Scopes, and separate model contexts, because Storage authorization cannot retract information already visible to a model.

Runtime 维护 / Runtime Maintenance

维护协调器是可选能力，默认只观察，不应用变更。配置的 semantic worker 只能在有界候选与 Detail 上 返回 write_summary、consolidate、keep_separate 或 defer 决策，不能直接写 Store；Runtime 补齐 机械元数据，Store 再验证权限、当前 head、lineage 与原子性。维护器不会自动执行 Revision 回收。

The maintenance coordinator is optional and defaults to observation without applying changes. A configured semantic worker may return only write_summary, consolidate, keep_separate, or defer decisions over bounded candidates and Detail. It cannot write the Store directly; Runtime supplies mechanical metadata, and the Store revalidates authorization, current heads, lineage, and atomicity. The maintainer never performs automatic Revision collection.

详见 / See crates/pcp-runtime/README.md.

Codex / MCP

MCP 可以直接打开 embedded SQLite Store： MCP can open an embedded SQLite Store directly:

cargo build --release -p pcp-mcp
codex mcp add pcp \
  --env PCP_STORE_PATH=/absolute/path/to/context.sqlite3 \
  --env PCP_CLIENT_ID=codex:project-example \
  --env PCP_ACCESS_MODE=read \
  --env PCP_ALLOWED_SCOPES=project:example,conversation:example-main \
  -- /absolute/path/to/paged-context-protocol/target/release/pcp-mcp

也可以让 MCP 连接已经运行、身份绑定的 Runtime： Alternatively, MCP can connect to an identity-bound Runtime:

codex mcp add pcp \
  --env PCP_RUNTIME_SOCKET=/absolute/path/to/pcp-codex.sock \
  --env PCP_CLIENT_ID=codex:project-example \
  -- /absolute/path/to/paged-context-protocol/target/release/pcp-mcp

PCP_ACCESS_MODE 可为 read、audit、write 或 admin。即使在 admin 模式，跨 Scope 派生仍需 单独启用。pcp_whoami 用于检查服务端注入的 Principal 与授权范围；读工具不产生内容写入，Page、 Summary、Relation、Scope 与 Validity 工具会被 MCP 标记为写操作。

PCP_ACCESS_MODE may be read, audit, write, or admin. Cross-Scope derivation still requires a separate opt-in even in admin mode. pcp_whoami reports the server-injected Principal and grants. Read tools do not mutate content; Page, Summary, Relation, Scope, and Validity tools are marked as writes for MCP approval.

只读 Console / Read-only Console

Console 应连接一个独立的 audit 端点。它提供 Page、Relation、访问时间线、Retention 和 Health 视图，但不提供写入、修订、关联、撤回、Scope 管理或回收操作。Health 将存储形态、活动、召回、 整合、关系与运行状况分开呈现，不合成为不透明总分；操作遥测不保存查询文本或 Page 内容。

The Console should use a dedicated audit endpoint. It exposes Page, Relation, access-timeline, Retention, and Health views without write, revise, link, retract, Scope-management, or collection operations. Health presents storage shape, activity, recall, consolidation, graph, and operations separately rather than as an opaque score. Operational telemetry excludes query text and Page content.

cargo build --release -p pcp-console
PCP_RUNTIME_SOCKET=/absolute/path/to/pcp-operator.sock \
PCP_CLIENT_ID=operator:local \
PCP_CONSOLE_BIND=127.0.0.1:4318 \
  target/release/pcp-console

规范与历史 / Specification and History

• 当前协议 / Current specification: PROTOCOL.md (中文) · PROTOCOL-en.md (English)
• Runtime 说明 / Runtime notes: crates/pcp-runtime/README.md
• 历史版本与淘汰原因 / Historical generations and deprecation rationale: deprecated/
• License: MIT