Producer-owned message sources at the V4 edge
V4 边缘上的生产者归属消息源
Released V3 plugin attribution uses the shared wrapper `{ kind: 'plugin', plugin: '<producer>' }` plus the producer's context-form fields, so consumers had to treat one synthetic kind specially instead of switching on the producer identity. Once tool results became first-class tool-role messages and the current generation moved to V4, the format layer also had to keep reading released V3 files whose rows still carry
English
Problem
Released V3 plugin attribution uses the shared wrapper { kind: 'plugin', plugin: '<producer>' } plus the producer's context-form fields, so consumers had to treat one synthetic kind specially instead of switching on the producer identity. Once tool results became first-class tool-role messages and the current generation moved to V4, the format layer also had to keep reading released V3 files whose rows still carry the wrapper.
Decision
Message sources are producer-owned: kind identifies the producer, with declarations contributed through MessageSourceMap. The V3-to-V4 migration uses its fixed producer table: @deepseek-ai/dsh-system-prompt becomes system-prompt for system-role messages and runtime-context otherwise; compact becomes compact-checkpoint; tools-code-mode and tools-ptc become ptc-mode; dsh-compaction-basic becomes compact-basic; known same-name producers retain their kind. Unknown plugin names receive plugin: before the complete original name, while direct source kinds retain their original names. The prefix keeps a plugin named user separate from the human-user kind; this edge leaves direct attribution unchanged. Original context-form fields and other own JSON metadata survive; only the old wrapper's identity fields receive their specified conversion. Rename lookup uses own keys, so __proto__ and constructor remain data.
Native V4 source admission rejects the retired kind: 'plugin' wrapper in every declared durable message slot, including inbox and title-request messages. This refusal applies before recoverable scanning can discard a suffix. Complete source-slot validation runs in the shared known-event pass used by both the format catalog and native JSONL scanner, before either exposes a restored artifact or handle. Unknown nonempty attribution kinds and their extra JSON fields survive without their producer installed. Native compaction and title relationship checks use the producer kinds directly; the mandatory validation decision owns common lifecycle rules.
The source rewrite is owned by the V3-to-V4 migration stage and runs once while historical events become V4 events. The current V4 codec retains only the released physical framing and native V4 admission; it never sends a V4 row through the released V3 validator and has no source-conversion view in its encode, decode, restore, or row-admission paths.
Recorded current V4 fixtures and writer, notification, and stream-json sidecars are producer-owned; released V2/V3 fixtures and sidecars keep plugin attribution and convert at read time through the migration. The released session-format migrations note owns the versioning rules this edge follows.
The source-attribution policy distinguishes durable source declarations from request-only user inputs and records the narrowly scoped compatibility promise for new attribution kinds. Frozen migration rules retain historical producer kinds even when no active producer declares them.
Alternatives considered
Keep the released plugin wrapper as the current shape. Consumers would keep switching on one synthetic kind and the producer identity stays an untyped string; the current semantic validators would keep a second, unreleased source vocabulary.
Rewrite released rows only at scan time instead of migrating them. Scan admission is deliberately shape-only and refuses, never repairs; a scan-time rewrite would blur released generations with current rows and leave the current artifact with version-inappropriate source identities.
Reject plugin-kind rows as ordinary corruption in the scanner. That would let a stale released row silently truncate a current Session instead of surfacing a refusal, and would misclassify rows that full decoding still needs to diagnose.
Consequences
The recorded corpus for this migration applies the frozen rename table, while current-generation validation consumes producer-owned kinds directly. Web context labels render the producer kind (runtime-context) instead of the released plugin string. The shared rewriter reports malformed released sources as SessionFormatError, so a malformed historical source is a migration refusal rather than a silent payload loss.
中文
Problem
已发布 V3 的插件归属使用共享包装 { kind: 'plugin', plugin: '<producer>' } 外加生产者的上下文形态字段，消费方因此必须特殊对待一个合成 kind，而不是直接按生产者身份切换。工具结果成为一等 tool-role 消息、当前世代进入 V4 之后，格式层还必须继续读取仍带包装的已发布 V3 文件。
Decision
消息源由生产者拥有：kind 标识生产者，各方通过 MessageSourceMap 提供声明。V3-to-V4 迁移使用固定生产者表：@deepseek-ai/dsh-system-prompt 在 system-role 消息上变成 system-prompt，否则变成 runtime-context；compact 变成 compact-checkpoint；tools-code-mode 与 tools-ptc 变成 ptc-mode；dsh-compaction-basic 变成 compact-basic；已知同名生产者保留 kind。未知插件名在完整原名之前添加 plugin:，直接 source kind 则保留原名。该前缀将名为 user 的插件与人类用户 kind 区分开；本边保持直接归属不变。原上下文形态字段及其他自有 JSON 元数据保留；只有旧包装的身份字段执行指定转换。重命名查找使用自有键，因此 __proto__ 和 constructor 仍是数据。
原生 V4 消息源准入在每个声明的持久化消息槽位拒绝退役的 kind: 'plugin' 包装，包括 inbox 和标题请求消息。可恢复扫描丢弃后缀之前就会执行此拒绝。完整消息源槽位校验在格式目录和原生 JSONL 扫描器共用的已知事件校验中执行，先于两者公开恢复产物或句柄。即使生产者未安装，未知的非空归属 kind 及额外 JSON 字段仍原样保留。原生压缩和标题关系校验直接使用生产者 kind；强制校验决策负责通用生命周期规则。
来源重写由 V3 到 V4 迁移 Stage 负责，在历史事件转换为 V4 事件时只执行一次。当前 V4 编解码器只保留已发布的物理分帧和原生 V4 准入；它不会让 V4 行进入已发布 V3 校验器，编码、解码、恢复和行准入路径也没有来源转换视图。
录制的当前 V4 fixtures 与 writer、notification、stream-json 侧车是生产者归属的；已发布的 V2/V3fixtures 与侧车保留 plugin 归属，读取时经迁移转换。released session-format migrations笔记拥有本边所遵循的版本规则。
消息源归属策略区分持久化 source 声明与仅用于请求的 user 输入，并记录新增归属 kind 的受限兼容性承诺。即使没有活动生产者声明，冻结迁移规则仍保留历史生产者 kind。
Alternatives considered
保留 released plugin 包装作为当前形态。 消费方将继续特殊对待一个合成 kind，生产者身份仍是无类型字符串；当前语义校验器也会保留第二套非发布的消息源词汇。
只在扫描时重写 released 行而不是迁移它们。 扫描准入刻意只查形态并拒绝、从不修复；扫描时重写会模糊 released 世代与当前行的界限，使当前产物保留与版本不符的来源身份。
在 scanner 中把 plugin-kind 行当作普通损坏拒绝。 这会让过期的 released 行静默截断当前 Session，而不是给出拒绝；也会把完整解码仍需要诊断的行错误分类。
Consequences
本迁移的记录语料库应用冻结重命名表，而当前代校验器直接消费生产者自有 kind。Web 上下文标签渲染生产者 kind（runtime-context）而不是 released plugin 字符串。共享重写器将畸形历史来源报告为 SessionFormatError，因此迁移会拒绝它，而不会静默丢失载荷。