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On routes whose model reads a later system message as the effective prompt, dsh does not rewrite the first system node when the rendered prompt changes: SystemPromptProjection appends a complete system message after the cached history, and the Messages serializer ships it as a plain-text role:"system" message after the user turn. The newest such message is the prompt in force. ACP folded it like any plain-text message, so one compress range covering it left the model on the stale head prompt until the text changed again. Add a fifth durable identity to the dsh lane classifier, durable/system-prompt (dshSystemPromptPath), under the existing durable/* latest-per-identity default: the newest copy is pinned, superseded copies stay foldable. The criterion is the role (no text marker exists for a prompt): a non-empty plain-text system-role core that is neither bili's own summary carrier nor a structured system. Structured systems keep the kernel's hard pin; the classifier reuses hasUnrecoverableMediaPayload so the two rules cannot overlap and a tool delta arriving after the prompt cannot take its latest slot. The identity is consulted before the twelve marker classifiers. Their role gate only refuses the assistant role, so a system prompt that quoted a carrier marker used to project to that carrier's identity and take the latest slot from the real user-channel instance. Host layer only: no change under kernel/, no config field, no wire or persistence change. Other lanes keep folding plain-text in-history systems. oneShotCarrierPaths (drift accounting) is unchanged.
… limits Follow-up to the durable/system-prompt identity, from review. Tests: - Messages wire end-to-end: assert the role the kept prompt is forwarded with. Once the fold removes the assistant that followed it, the kernel's position heal re-voices a plain system as user, so the text survives and the system role does not. Pinned as a known limit; a kernel that relocates instead of demoting flips the assertion. - Lane wiring: drop the "registry keys are exactly [dsh]" pin (another lane registering a classifier is not this test's business) and assert instead that no other lane projects a plain-text system. - Drift registry: pin that system-role text containing a carrier marker is still accounted by marker there, as before the identity existed. - The chat-completions scenario cites the llm-pi-ai wire test it mirrors. Comments only in src/durable-message-guards.ts: where a developer message carrying text would share the identity (llm-pi-ai splits the text off on chat-completions and responses), and that the drift chain has no system-role step. Devlog: no retroactive unfold for prompts already covered by a block from an earlier build, the token cost of a never-folded copy, and the corrected red count on master (9 of 14).
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🟡 Changes recommended
A moderate active issue remains in src/durable-message-guards.ts where using msg.text.trim() as a whitespace check can unnecessarily allocate large strings (e.g., ~45K chars) and create avoidable memory churn in a repeatedly-invoked path, so a non-allocating whitespace test is needed.
1 open issue
What changed in this PR
Fix a dsh-lane correctness bug where the latest effective in-history system prompt could be folded into a summary, causing requests to run with a stale head prompt until the prompt text changes again.
Changes:
- Add a new dsh durable identity
durable/system-promptto preserve the newest plain-text in-history system prompt while keeping superseded copies foldable. - Prioritize this identity ahead of marker-based durable carriers to prevent carrier-slot takeover.
- Add regression coverage for classifier behavior, compression geometry, and real folding on both Messages and chat-completions wires, plus update inline docs/devlogs.
| File | Description |
|---|---|
| tests/dsh-system-prompt-durable.test.ts | Adds a new regression test suite validating that the newest in-history system prompt is preserved through classification and real compression for Messages and chat-completions wires. |
| src/durable-message-guards.ts | Introduces dshSystemPromptPath (durable/system-prompt) and wires it early in the dsh classifier so the latest plain-text system prompt is protected from folding. |
| src/config.ts | Updates configuration documentation comments to include the new durable/system-prompt identity alongside existing dsh durable carriers. |
| devlog/2026-11-12_dsh-durable-system-prompt/WORKLOG.md | Documents the investigation, implementation notes, testing performed, and known limitations for the dsh durable system-prompt change. |
| devlog/2026-11-12_dsh-durable-system-prompt/REQ.md | Captures the requirements, acceptance criteria, and explicit non-goals for preserving the latest in-history system prompt in dsh. |
Review effort: Balanced
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| export function dshSystemPromptPath(msg: CoreMessage): string | undefined { | ||
| return msg.role === "system" && msg.contentType === "text" && typeof msg.text === "string" && | ||
| msg.text.trim().length > 0 && !msg.text.startsWith(SUMMARY_HEADER) && !hasUnrecoverableMediaPayload(msg) | ||
| ? "durable/system-prompt" | ||
| : undefined; | ||
| } |
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已改：换成 /\S/.test(msg.text)，不再为判空复制整段文本。
ranxianglei
changed the title
dshSystemPromptPath used msg.text.trim().length > 0 only to ask whether the text has any non-whitespace character. trim() allocates a copy of the whole prompt (tens of thousands of characters in the reports that motivated the identity), and the classifier is consulted repeatedly during protection and fold checks. /\S/.test(msg.text) answers the same question (same whitespace set as trim) without the copy. No behavior change; the existing negatives (empty and whitespace-only system nodes) cover it. From review on the PR.
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Fixes #6352
问题
在 dsh 车道上，如果 compress 的范围覆盖了最新的历史内系统提示（in-history system prompt），这条提示会被折叠（fold）进摘要（summary）。从那时起，直到提示文本再次变化，模型一直按过期的头部提示运行。没有报错，也没有日志。
这条消息为什么重要：渲染出的系统提示变化时，DeepSeek Harness 并不总是重写第一个 system 节点。在模型把后面的
system消息当作有效提示的路由上（systemPromptUpdate: "in-history"），它会在缓存历史之后追加一条完整的新 system 消息。顶层的system字段保留旧文本，最新的历史内 system 消息才是正在生效的提示。billion-context 把这条消息当作普通历史。
hasUnrecoverableMediaPayload只固定结构化的 system 消息（"Plain-text ones … fold like any text message"，纯文本的……和普通文本消息一样折叠），而 dsh 的持久（durable）分类器（src/durable-message-guards.ts）认识四种载体（carrier），都在 user 通道上。所以模型发起的 compress 调用和代理（proxy）发起的折叠都可能覆盖到它。这个 PR 恢复了什么，没恢复什么
改动之后，最新提示的文本总会留在转发的请求里。它的角色取决于 wire：
system。healIllegalSystemPositions，[Bug][anthropic] 0.1.205: 400 "role 'system' must precede an 'assistant' message" still occurs with #4396 present (mid-conversation system + tool_addition, cf. #4400) #4457/kernel authorization request: heal must enforce the FOLLOW side of Anthropic's mid-conversation system position rule (#5432) #5438）会把这个位置上的纯文本 system 重新标成user。提示文本能到达模型，但是以user消息的形式。端到端测试固定了这个角色，所以内核一旦改动，这里会有反应。要保持 system 角色需要改内核，本 PR 不做（见「未覆盖的部分」）。这个形态从哪里来（deepseek-harness 源码，MIT，标签
dsh-v0.2.2-rc.2；与 rc.1 相比没有变化）packages/core/agent-loop/src/runtime-context.ts，SystemPromptProjection.project："A capable continuing series appends changed nonempty text after the cached history."（一个有能力的连续序列会把变化后的非空文本追加在缓存历史之后。）只有在不支持的路由、提示被清空、或者文本不同的新请求序列这三种情况下，才会重写第一个节点。packages/llm/llm-deepseek/src/serialize.ts：在历史内路由上，非开头的 system 消息会变成{ role: "system", content: [{ type: "text", text }] }，排在 user / tool-result 轮之后、下一条 assistant 之前；只有位于开头的 system 才会成为顶层的system。它的tests/adapter.spec.ts固定了结果：提示变化后，body.system仍是first prompt，messages里带着{ role: "system", content: [{ type: "text", text: "second prompt" }] }；清空再恢复之后，请求里唯一的提示就是那条历史内消息。packages/llm/llm-pi-ai/src/models.ts（conversationUpdates）和context.ts：对声明了supportsMidConvoSystemMessages的目录模型，同样是历史内模式。它的tests/conversation-updates.spec.ts固定了各 wire 的形态：Anthropic Messages 和 chat-completions 用role: "system"，responses API 用role: "developer"加字符串内容。SystemPromptProjection（system）和agent.ts里的工具注册表更新（developer；只有tool-addition/tool-removal块，没有文本）。复现
tests/dsh-system-prompt-durable.test.ts，本 PR 新增。在 masterc26c31ac上它的 14 个测试里有 9 个失败（新导出被桩成返回undefined，以便文件能加载）；通过的 5 个是分类器的反例，以及对必须保持不变的行为的固定。llm-deepseek形态的 Messages 请求体（头部提示在顶层字段，两次历史内更新，一条 tool-delta system，一个实时请求），经anthropicToCore和applyCompression，使用 dsh 车道配置。在 master 上，最新提示的 id 落在新建的块里面。startServer跑八轮，两次历史内提示更新，经/__bili/plugin/tool做一次范围覆盖这两条的compress，再跑一轮。在 master 上，转发给上游的请求里不再有最新的提示，Messages wire 和 chat-completions wire 都是如此。改动
在 dsh 车道分类器里增加第五种持久身份：
durable/system-prompt（dshSystemPromptPath），归现有的durable/*按身份保留最新一份的默认规则管。最新的一份被固定；被后来的副本顶替的（superseded）副本和普通历史一样折叠。判定条件：
role === "system"，内容是文本，非空，并且hasUnrecoverableMediaPayload而不是重新写一遍，所以这条规则和内核对 tool-delta / 仅指令 system 的硬固定在构造上就是不相交的，在提示之后到达的 tool delta 也不可能占掉提示的最新位置；system，KDD feat: bili CLI + debug in config + README rewrite #7）。分类器按角色匹配，而不是按文本标记，因为系统提示没有稳定的标记：它是任意的宿主和插件文字。这里角色是比标记更强的证据。它由宿主的序列化器打上；人的输入总是走 user 通道，模型输出总是走 assistant 通道，所以用户消息和模型回声（#2766）都产生不出它。头部提示在每个编解码器里都会被提到折叠空间之外，因此 dsh 车道里 system 角色的核心消息就是历史内的那种。
新身份在那十二个标记分类器之前被查询。它们的角色门只拒绝
assistant，所以在 master 上，引用了某个载体标记的系统提示（比如一份讲解 skill 目录标签的提示）会被投影成那个载体的身份，并且因为更新，从真正的 user 通道载体手里抢走最新位置。由角色决定的身份排在前面之后，这条提示保有自己的固定，真正的载体也保有自己的位置（测试："the four durable carriers keep their own latest slot next to the prompt"，在 master 上为红）。行为变化，仅限 dsh 车道（旧 → 新）
durable/system-prompt不变的部分
oneShotCarrierPaths/dshCarrierRawMarkers（预期重基线的核算）：没有改动；被顶替的提示副本的核算与以前完全一致。那条链仍然没有 system 角色这一步，所以含有载体标记的 system 角色文本，在位置链里算提示，在漂移核算里算那个标记的载体。这是已有的漂移处理方式，源码里有注明，测试文件里也有固定。durable/…模式，仍然没有默认值；durable/system-prompt可以像另外四个一样被点名（已测试）。Config.messagePathOf，内核在每个判定可折叠性的地方都会查它（compress、unit-projection、recommend、absorb），所以模型发起的折叠和代理发起的折叠由同一条规则覆盖。没有改动任何 wire、工具注入或摘要载体的代码。按 wire 的适用范围
规则作用在内核核心的角色上，所以与 wire 无关。各 wire 的证据：
llm-deepseek、llm-pi-ai）和下面的现场测量。编解码层测试和端到端测试。llm-pi-ai；端到端测试用的是它的conversation-updates.spec.ts所固定的位置），以及 Non-leading system messages are demoted to regular history messages, causing the system prompt to accumulate progressive | 非首位的 system message 被降级成普通历史消息，导致 system prompt 逐步累积 #6193 里的生产报告（那里副本排在数组末尾）。编解码层测试和端到端测试。llm-pi-ai发出{ role: "developer", content }）；我没有流量样本。只有编解码层的分类器行，没有端到端测试。配置面
没有新字段、环境变量或 CLI 标志。只在现有的
durable/虚拟路径命名空间里多了一个名字，可通过现有的protectedTools/protectedLatestTools模式访问。src/config.ts里protectedLatestTools上方的注释列出了这个身份；gen-config-docs generate没有产生漂移。内核
kernel/**下没有改动。分类器导入了两个现有的内核导出（hasUnrecoverableMediaPayload、SUMMARY_HEADER）。现场证据
一个长期运行的 dsh 会话，九天窗口，只统计结构性数量：143 份历史内系统提示副本；其中 18 到 37 份（两种计数方法分别取交集和并集）在仍是最新副本时被一个新建的块覆盖；按交集计数，这些时段跨越 6,206 个模型请求中的 2,919 个。
相关
tool_additionbut keeps the latertool_removalfor the same tool → 400tool_reference_unresolved#4818 和 PR [PR] EN | kernel: relocate misplaced tool-delta systems instead of demoting them (fixes #4818) #5800（open）：同一类问题（折叠前后历史内 system 消息会怎样），但消息类别和层次不同。它们针对的是结构化 tool-delta system 和 Messages wire 上内核的位置修复（[Bug][anthropic][claude-code] 0.1.208: the system-position heal drops atool_additionbut keeps the latertool_removalfor the same tool → 400tool_reference_unresolved#4818 来自 Claude Code；[PR] EN | kernel: relocate misplaced tool-delta systems instead of demoting them (fixes #4818) #5800 还引用了一份 dsh 现场报告，说只含添加的载体被丢掉）。本 PR 针对的是纯文本提示和宿主的持久分类，并明确把 tool-delta system 留给内核规则。coreToAnthropic把system以user的角色发出。上面说的 Messages wire 上的角色丢失是同一类问题。未覆盖的部分
prune丢弃已覆盖的 id 时不查保护，之后的合并会把已被消耗的块的覆盖范围（range）整个接过来（用一次性探针检查过：旧版本折叠，然后在新配置下渲染并合并；两种情况下提示都保持隐藏）。这样的会话要等 dsh 发出下一次提示更新才能恢复。llm-pi-ai在 chat-completions 和 responses 上就是这样做的，即使该消息同时带有工具块（它的 spec：{ role: "system", tools }后面跟着{ role: "system", content: "…" }）；在 Messages wire 上只有纯文本的 developer 消息会这样（文本加工具块仍是一条结构化 system）。验证
Node 22.23.3，Windows，隔离的家目录，出站网络被阻断（任何一次运行都没有记录到被阻断的请求）。
tests/dsh-native.test.ts，该文件在未修改的 master 上同样时序不稳（5 次基线运行里有 2 次取消同样的 4 个；该文件不导入被改模块）。第二个提交只改了注释和新测试文件。npm run typecheck、npm run build：干净。check-unused-exports、check-test-import-graph、config-surface-guard、check-architecture-docs：干净。