Merge branch 'codex/tool-json-schema-dsl' into codex/canonical-tool-output

# Conflicts:
#	docs/config-catalog.md
#	docs/persistence-catalog.md
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/stdout.expected.jsonl
#	packages/cordis/tool-cordis/src/api-catalog.ts
#	packages/core/agent-loop/tests/contract-regressions.spec.ts
#	packages/ui/acp/src/index.ts
#	packages/ui/tui/src/index.ts

.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md

@@ -16,7 +16,7 @@ Two forces shape the design. First, compaction policy and reusable token measure
 
 Per the [capability-seams Agent Note](../architecture/2026-06-13-capability-seams.md), compaction ships as separate packages so the contract, the algorithm, and (later) the consumer surface evolve independently:
 
-1. **Interface** — `@deepseek-ai/dsh-compact`: an abstract `CompactService` owning the `ctx.compact` key, the `CompactionResult` vocabulary, and the `compact/*` session events. It declares `compactIfNeeded()` and `compactRegion()` as **abstract** — the contract states *what* compaction does, not *how*.
+1. **Interface** — `@deepseek-ai/dsh-compact`: an abstract `CompactService` owning the `ctx.compact` key, the `CompactionResult` vocabulary, the `compact/*` session events, and the canonical checkpoint message source. It declares `compactIfNeeded()` and `compactRegion()` as **abstract** — the contract states *what* compaction does, not *how*.
 2. **Implementation** — `@deepseek-ai/dsh-compact-basic`: a concrete `BasicCompactService` that consumes `ctx.tokenMeter` and owns the tail→head retention walk, summarization via `ctx.llm.stream()`, the surface replacement, the lock, post-step pressure, and canonical context-overflow recovery. `summarize()` is its sole subclass hook; pricing and replay stay with the meter.
 3. **Model-free companion** — `@deepseek-ai/dsh-compact-tool-result-prune`: a concrete optional service that rewrites oversized current `tool/result` nodes before the backend selects a summary range. It is not a second compaction implementation and does not implement `CompactService`.
 4. **Consumer** — deferred. A `/compact` tool and slash command will `inject: ['compact']` and call the contract; they are intentionally out of scope here so the seam settles first.
@@ -69,13 +69,14 @@ Auto-compaction always starts at the surface head, merging the prior checkpoint
 
 ### Surface replacement: `compact/*` events are log-only; one `user/message` carries the summary
 
-Because `SurfaceEventType` is closed, the summary cannot ride on a `compact/*` event. The backend instead appends a **single `user/message`** with `surfaceOp: { op: 'replace', start, end }` whose `content` is the (framed) summary and whose `sourceEventSeqs` covers the shadowed entries *and* the bookkeeping events. The `compact/*` events are pure log records (lock + provenance). The surface mutation sits **inside** the lock — `compact/end` is the last event appended:
+Because `SurfaceEventType` is closed, the summary cannot ride on a `compact/*` event. The backend instead appends a **single `user/message`** with `source: COMPACT_CHECKPOINT_SOURCE` and `surfaceOp: { op: 'replace', start, end }` whose `content` is the (framed) summary and whose `sourceEventSeqs` covers the shadowed entries *and* the bookkeeping events. The interface exports that source and `isCompactCheckpointSource()` so consumers recognize a persisted or cloned checkpoint without depending on backend package identity. The `compact/*` events are pure log records (lock + provenance). The surface mutation sits **inside** the lock — `compact/end` is the last event appended:
 
 ```
 compact/start    → log-only. Acquires the lock.
 [summarize older range via the backend]
 compact/summary  → log-only. Provenance: raw summary, range, shadowed seqs, token count.
-user/message     → surfaceOp { op:'replace', start, end }. THE surface mutation (framed summary).
+user/message     → canonical checkpoint source + surfaceOp { op:'replace', start, end }.
+                   THE surface mutation (framed summary).
                    deriveMessages() renders it as a user-role message.
 compact/end      → log-only. Releases the lock (carries `error` on a recoverable failure).
 ```
@@ -84,7 +85,7 @@ compact/end      → log-only. Releases the lock (carries `error` on a recoverab
 
 ### Checkpoint framing + incremental merge (backend-private)
 
-The basic backend wraps the summary as established checkpoint context and tags it for incremental merging on the next cycle. The raw summary remains on `compact/summary`. Framing is backend policy; the seam promises only that one replacement user message carries the possibly framed summary.
+The basic backend wraps the summary as established checkpoint context and tags it for incremental merging on the next cycle. The raw summary remains on `compact/summary`. Framing is backend policy; the seam promises that one replacement user message carries the possibly framed summary and uses the canonical checkpoint source.
 
 ### Blocking via a log-recorded lock, plus a crash/recoverable failure taxonomy
 
@@ -117,7 +118,7 @@ Two failure paths, both documented:
 - **Packages**: `packages/compact/compact` supplies the interface, `compact-basic` supplies the backend, and `compact-tool-result-prune` supplies optional deterministic rewriting. `packages/llm/token-meter` owns replay-aware measurement independently. The consumer tier is deferred.
 - **Automatic seams**: `agent/post-step` (`@mode serial`) handles successful-call pressure and `agent/request-error` (`@mode waterfall`) handles final request failures after the failed step closes. Generic `agent/pre-step` remains a four-argument checkpoint with no compaction-only prompt/prefix payload.
 - **`SessionEventMap`** gains `compact/start` / `compact/summary` / `compact/end` by declaration merging (merge-extensible); `SurfaceEventType` is **not** touched. These are session events, not cordis `Events`, so the event-taxonomy gate needs no entry.
-- **`dsh-compact`** owns `toolPairingBalancedBefore(session, seq)` and `toolPairingBalancedAfter(session, seq)`, the cached surface-edge checks that `compactRegion` and `compactIfNeeded` use to avoid splitting a tool-call/result pair. The cache validates current membership by seq and answers both edges from one per-cut balance sequence; stale or missing seqs and orphan results reject.
+- **`dsh-compact`** owns `COMPACT_CHECKPOINT_SOURCE`, `isCompactCheckpointSource(source)`, `toolPairingBalancedBefore(session, seq)`, and `toolPairingBalancedAfter(session, seq)`. The marker identifies replacement summaries across backend implementations. The cached surface-edge checks prevent `compactRegion` and `compactIfNeeded` from splitting a tool-call/result pair, validate current membership by seq, answer both edges from one per-cut balance sequence, and reject stale or missing seqs and orphan results.
 - **`dsh-session`** validates positional replacement, complete provenance, and content-only single-node `tool/result` rewrites through its one surface manager. Its invariant companion treats fresh appended tool results as executions that require an open step and pending call; validated replacements remain turn-enclosed rewrites.
 - **Wiring**: `examples/tui-agent/cordis.yml` loads zero-config `dsh-token-meter`, `dsh-compact-tool-result-prune`, then `dsh-compact-basic`; service-wide defaults make the composition usable without repeated numeric policy.
 

.agents/notes/implemented/feature/2026-07-21-cross-session-references.i18n.yaml

@@ -0,0 +1,6 @@
+# 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
+2026-07-21-cross-session-references.md: bfa015b24cda6c8651829b6a7f0800326da5b502
+2026-07-21-cross-session-references.zh.md: e8e99124f7e2ccfe9fbe97323c17143372017562

.agents/notes/implemented/feature/2026-07-21-cross-session-references.md

@@ -0,0 +1,60 @@
+# Agent Note: Cross-session references
+
+Status: implemented
+
+English | [中文](2026-07-21-cross-session-references.zh.md)
+
+## Problem
+
+TUI and ACP users need to bring relevant work from another conversation into one new message without resuming, forking, or granting the source transcript authority over the current session. The harness already exposes exact session enumeration and raw event inspection, but every host independently parsing logs would duplicate compaction folding, provenance filtering, size limits, error behavior, and persistence. Encoding host markup directly into the agent message contract would also bind the core loop to one UI syntax.
+
+## Decision
+
+`@deepseek-ai/dsh-session-reference` is one context consumer service at `ctx.sessionReferences`. Hosts normalize their protocol into `SessionReferenceInput[]`, call `prepare()` before enqueue, and pass the returned contexts through the generic `SendOptions.contexts` boundary. Core agent packages know only that one queued message may carry frozen `HookContext[]`; they do not parse session URIs or read another log.
+
+`dsh-session:<base64url(JSON.stringify(sessionId))>` is the canonical host-independent identifier. JSON string encoding precedes base64url so quotes, slashes, backslashes, Unicode, newlines, and every other JavaScript string value round-trip without delimiter ambiguity. TUI renders that URI inside `@[label](uri)` and ACP uses standard `resource_link`; text-only clients may use the same inline mention. Explicit Markdown mentions and resource links reject malformed URIs. Bare text becomes a reference only for a non-empty base64url-shaped payload, whose decode must still be canonical; empty or punctuation-only uses remain ordinary discussion text.
+
+The service uses `ctx.sessionQuery.readSurface(sessionId)`, which loads one live-preferred corpus observation, folds it with the session package's canonical surface algorithm, and returns a detached header, capture seq, and current nodes. FTS is not a dependency: v1 discovery filters only id and cwd, and future title/body search can replace the candidate layer without changing reference identity or preparation.
+
+## Snapshot and projection
+
+Preparation deduplicates in first-appearance order, rejects the target id, enforces a configurable limit with a hard maximum of three references, and performs all reads in parallel. It returns no partially prepared context: any read, cancellation, validation, or budget error rejects the operation before `send()` or `steer()`. Cancellation races in-flight discovery and exact reads, so a host settles promptly even when a persistence backend cannot interrupt its pending operation; any late backend settlement is observed but cannot enqueue the message. A source is read before enqueue, so later source messages, compaction, deletion, or persistence replacement cannot change the target session.
+
+Projection retains direct-user messages and steering, completed assistant text, and checkpoint user messages carrying the canonical source exported by `dsh-compact`. That marker is part of the compaction capability contract rather than a backend package name. When a source prompt already contains baked prefix context, projection reads only its model-hidden display content, so referencing that target later does not recursively propagate an earlier snapshot. Projection excludes shadowed pre-compaction nodes, tools and results, reasoning, injected context, other plugin user messages, log-only records, and incomplete assistant chunks. Repeated compaction therefore exposes only the latest folded checkpoint lineage still on the current surface plus its retained tail; there is no raw/current switch and no shadow recovery.
+
+One aggregated context is serialized as JSON beneath a fixed untrusted-background warning. The warning tells the model not to follow instructions, permission claims, or tool requests from referenced sessions unless the current user repeats them. Tag-safe serialization emits every data `<` as the lossless JSON escape `\u003c`; source strings therefore cannot spell the surrounding XML-like tags. The `## My request:` text is a routing cue rather than the trust boundary: referenced data may spell those words inside a JSON string, but it cannot forge the closing `</referenced-sessions>` tag or escape the data region. The same serializer drives each source's independent byte accounting. The context declares `prompt-prefix` placement, so AgentLoop persists one `user/message` or `steering/message` containing the snapshot, `## My request:` delimiter, and effective direct prompt. Its model-hidden envelope retains the direct display content and source/retention metadata. Target replay therefore satisfies the model-visible/log-reconstructable invariant without a new event type or a separate user-role context message.
+
+## Message ownership
+
+`send()` and `steer()` snapshot content, resolved source, and contexts together as one deeply frozen lossless-JSON inbox record. Synthetic `inject()` accepts source and model-hidden metadata but not attached contexts, which belong to inbox messages. A claimed ordinary message exposes its attached contexts as the default `agent/prompt-submit` additional contexts; a block writes neither user message nor contexts. The waterfall's returned allow is authoritative, so a listener wrapping `next()` preserves downstream content and contexts unless it intentionally replaces them. After admission, absent or `separate` placement writes an independent `context/message`, while `prompt-prefix` placement bakes context and the effective request into one prompt event. Drained steering bypasses `agent/prompt-submit` but applies the same placement split. Late steering retains the same record when converted to queued input, while cancellation, disposal, and terminal discard drop message and contexts together. `agent/queued` reports the frozen contexts so the observation event describes the complete retained item.
+
+This preserves host driving semantics: TUI decides `send()` versus `steer()` from the agent state after preparation, so only its queued path dispatches UserPromptSubmit hooks; ACP continues to call `send()` once per `session/prompt`. Reference preparation is not a new steering protocol and does not create a turn by itself.
+
+## Host adapters
+
+TUI combines session candidates with the existing `@` file provider. Each candidate displays the latest folded session title and falls back to the session id; lookup follows the editor's cancellation signal, and session id, cwd, and mention labels escape external terminal controls while the canonical URI retains the original id. TUI prepares only submissions containing structured mentions, disables duplicate submit while awaiting snapshots, restores failed input, renders the prompt envelope's display content as the user message, and renders its session-reference metadata as a compact source list instead of exposing the complete JSON in the terminal.
+
+ACP detects direct slash commands from ordinary prompt flattening before extracting `dsh-session:` resource links and canonical inline mentions, so URI-shaped command arguments remain opaque while ordinary resource-link rendering is preserved. Standard `session/list` exposes each loadable session's folded title and, when references are mounted, a canonical URI under `_meta["deepseek-harness/sessionReference"]`; a client can use `title ?? sessionId` as the resource-link name. A valid reference without the optional service returns a capability-unavailable RPC error, and preparation failure occurs before the in-flight turn slot and agent send. A preparation-specific abort owner makes `session/cancel` and bridge teardown stop pending reads. Picker UI remains an ACP client responsibility because ACP does not define a cross-session mention menu.
+
+## Budget and retention
+
+Each of at most three references is independently capped at 65,536 UTF-8 bytes by default. Retention preserves current compact checkpoints and the newest conversation unit before dropping older non-checkpoint messages. An oversized retained text uses `dsh-retention` head/tail slicing and records exact omitted bytes; if one source's fixed serialized fields cannot fit its cap, the whole preparation fails rather than emitting a partial context.
+
+## Alternatives considered
+
+- **Wait for SQLite FTS5** — rejected because snapshot correctness requires exact id reads and canonical surface folding, not content search. FTS improves discovery only.
+- **Put mention syntax in `Agent.send()`** — rejected because it would make the core protocol parse TUI/ACP presentation and prevent typed non-text hosts from sharing the semantic layer.
+- **Implement references inside TUI and ACP separately** — rejected because projection, security warning, retention, and persistence would drift across hosts.
+- **Place a separate user-role context message beside the prompt** — rejected because two adjacent user messages weaken the prompt's deictic binding: in `@foo what does this session discuss?`, the model may resolve “this session” as the current conversation instead of the referenced snapshot.
+- **Bake the prefix host-side before `send()`** — rejected because `agent/prompt-submit` must inspect and rewrite only the direct prompt. The effective prompt and attached contexts meet only after admission in AgentLoop, which can apply an `allow.content` rewrite consistently to both combined model content and `envelope.displayContent`; earlier host assembly would expose snapshot bytes to the hook or let those two views diverge.
+- **Replay the raw source log or restore shadowed events** — rejected because compact defines the current model surface and may intentionally retire sensitive or expensive history.
+- **Resume or fork the source** — rejected because the feature supplies read-only background for one target message, not identity or lifecycle continuity.
+- **Inject at request time by rereading the source** — rejected because the reference would become nondeterministic, cancellation races could alter its bytes, and target replay would depend on external mutable state.
+
+## Verification
+
+Unit and integration coverage pins URI round-trips and text-boundary punctuation, explicit malformed references, title-aware candidate ranking, terminal-control escaping, projection exclusions, non-recursive prompt-envelope projection, backend-independent compact checkpoints, tag-safe framing, deduplication, self-reference, count limits, all-or-nothing reads, prompt cancellation against a non-settling storage read, independent per-source byte retention, frozen message ownership, prompt blocking, send/steer placement, title isolation, missing capability, title-aware ACP session listing, ordinary ACP resource links, opaque ACP command arguments, and compact TUI/ACP replay. A keyless TUI snapshot runs the real agent loop: the source surface replaces old user/assistant history with a compact checkpoint, the target submits a mention, and the captured model request contains one user message ordered as snapshot, request delimiter, and current prompt, without either shadowed string.
+
+## Consequences
+
+The new plugin is the stable semantic boundary and adds no persistence schema, event type, FTS dependency, source subscription, or compact shadow access. Standard TUI/ACP demo bundles mount it explicitly and expose its count and per-source byte limits in their own config; custom hosts remain unchanged until they mount the service and adapt their input. Reference contexts increase target history size within configured bounds and can later be summarized by ordinary target compaction, after which the source session is irrelevant.

.agents/notes/implemented/feature/2026-07-21-cross-session-references.zh.md

@@ -0,0 +1,60 @@
+# Agent Note: 跨会话引用
+
+Status: implemented
+
+[English](2026-07-21-cross-session-references.md) | 中文
+
+## 问题
+
+TUI 与 ACP（Agent Client Protocol）用户需要把另一场对话中的相关工作带入一条新消息，但不恢复、不 fork，也不让源 transcript（文本记录）对当前会话拥有权威性。harness 已经提供准确的会话枚举与原始事件检查，但若每个宿主都独立解析日志，就会重复实现压缩（compaction）折叠、来源过滤、大小限制、错误行为和持久化。把宿主标记直接编码进 agent（智能体）消息契约，还会让核心循环绑定某一种 UI 语法。
+
+## 决策
+
+`@deepseek-ai/dsh-session-reference` 是注册在 `ctx.sessionReferences` 上的单一上下文消费服务。宿主先把各自的协议规范化为 `SessionReferenceInput[]`，在入队前调用 `prepare()`，再通过通用的 `SendOptions.contexts` 边界传递返回的上下文。核心 agent 包只知道一条排队消息可以携带已冻结的 `HookContext[]`；它们既不解析会话 URI，也不读取其他日志。
+
+`dsh-session:<base64url(JSON.stringify(sessionId))>` 是与宿主无关的规范标识符。系统先执行 JSON 字符串编码，再执行 base64url 编码，因此引号、正斜杠、反斜杠、Unicode、换行符以及其他任意 JavaScript 字符串值都能无损往返，不会因分隔符产生歧义。TUI 把该 URI 渲染到 `@[label](uri)` 中，ACP 使用标准 `resource_link`；纯文本客户端可以使用同一种行内提及标记。显式 Markdown 提及标记与资源链接会拒绝格式错误的 URI。裸文本只有在负载非空且形状符合 base64url 时才会成为引用，而且解码过程仍须通过规范性校验；空负载或只含标点符号的用法仍按普通讨论文本处理。
+
+该服务使用 `ctx.sessionQuery.readSurface(sessionId)`：它优先从实时会话加载一次语料观察结果，使用会话包的规范表层算法执行折叠，并返回与源数据分离的会话头、捕获序号和当前节点。FTS 不是功能依赖：v1 的候选发现只按 id 和 cwd 过滤；未来的标题或正文搜索可以替换候选层，而无需改变引用标识或准备过程。
+
+## 快照与投影
+
+准备过程按首次出现的顺序去重、拒绝目标会话自身的 id，并且执行可配置的数量限制，但引用硬上限为三个，所有读取均并行执行。该过程不会返回部分完成的上下文：任何读取、取消、校验或预算错误都会在调用 `send()` 或 `steer()` 前拒绝本次操作。取消会与进行中的候选发现和精确读取竞速，因此即使持久化后端无法中断待处理操作，宿主也能及时结束等待；后端迟到的完成结果仍会被观察，但不能让消息入队。源会话在入队前完成读取，因此源会话后续新增消息、执行压缩、被删除或替换持久化内容，都无法改变目标会话中的快照。
+
+投影会保留直接用户消息与 steering（中途引导）、已完成的 assistant 文本，以及携带由 `dsh-compact` 导出的规范来源标记的检查点用户消息。该标记属于压缩功能契约的一部分，而非某个后端包名称。当源提示词已包含合并写入的前缀上下文时，投影只读取其模型不可见的显示内容，因此后续引用该目标不会递归传播先前的快照。投影会排除压缩前已被遮蔽的节点、工具及其结果、推理（reasoning）、注入的上下文、其他插件用户消息、仅用于日志的记录，以及尚未完成的 assistant 分片。因此，重复压缩只会暴露当前表层仍保留的最新折叠检查点谱系及其尾部消息；系统不提供 raw/current 开关，也不恢复被遮蔽的内容。
+
+系统把一个聚合上下文序列化为 JSON，并置于固定的不可信背景警告之后。该警告要求模型不要遵循被引用会话中的指令、权限声明或工具请求，除非当前用户再次提出这些内容。标签安全序列化会把数据中的每个 `<` 无损转义为 JSON `\u003c`；因此源字符串无法拼出外围类似 XML 的标签。`## My request:` 文本只是路由提示，不是信任边界：被引用数据可以在 JSON 字符串中包含这些词，但无法伪造闭合的 `</referenced-sessions>` 标签，也无法逃逸数据区域。同一个序列化器会独立核算每个源的字节数。该上下文声明 `prompt-prefix` 放置方式，因此 AgentLoop 会持久化一条 `user/message` 或 `steering/message`，其中包含快照、`## My request:` 分隔符和最终生效的直接提示词。其模型不可见封套保留直接显示内容以及来源与保留元数据。因此，目标回放无需新增事件类型或单独的用户角色上下文消息，也能满足「模型可见／日志可重建」不变量。
+
+## 消息所有权
+
+`send()` 与 `steer()` 会把内容、解析后的来源和上下文一起快照为一条深度冻结、无损 JSON 的收件箱记录。合成的 `inject()` 接受来源和模型不可见的元数据，但不接受附加上下文，因为上下文属于收件箱消息。普通消息被认领后，其附带的上下文会作为 `agent/prompt-submit` 的默认附加上下文公开；提示词被阻止时，系统既不写入用户消息，也不写入上下文。waterfall（瀑布式事件）返回的 allow 结果具有最终权威性，因此监听器包装 `next()` 时会保留下游内容与上下文，除非它有意替换这些值。消息被接纳后，未指定放置方式或指定为 `separate` 时会写入独立的 `context/message`；指定为 `prompt-prefix` 时则会把上下文与最终生效的请求合并写入同一个提示词事件。排空 steering 消息时会绕过 `agent/prompt-submit`，但采用相同的放置方式分流。延迟到达的 steering 转换为排队输入时保留同一条记录；取消、dispose（资源释放）和到达终止态后的丢弃则会同时丢弃消息与上下文。`agent/queued` 会报告已冻结的上下文，使观察事件能够描述完整的保留项。
+
+这保留了宿主的驱动语义：TUI 在准备完成后根据 agent 状态决定调用 `send()` 还是 `steer()`，因此只有它的排队路径才会分派 UserPromptSubmit 钩子；ACP 则继续调用 `send()`，每个 `session/prompt` 调用一次。引用准备过程不是新的 steering 协议，本身也不会创建轮次。
+
+## 宿主适配器
+
+TUI 把会话候选与现有 `@` 文件提供方组合在一起。每个候选项显示最新折叠后的会话标题，没有标题时回退到 session id。候选查询遵循编辑器的取消信号；session id、cwd 和提及标签中的外部终端控制字符会被转义，但规范 URI 仍保留原始 id。TUI 只准备包含结构化提及标记的提交；等待快照时禁用重复提交；失败时恢复输入；它把提示词封套的显示内容渲染为用户消息，并把其中的会话引用元数据渲染为精简的来源列表，不在终端中暴露完整 JSON。
+
+ACP 先从普通提示词扁平化结果中检测直接斜杠命令，再提取 `dsh-session:` 资源链接和规范的行内提及标记，因此形如 URI 的命令参数保持不透明，同时保留普通资源链接的渲染方式。标准 `session/list` 会公开每个可加载会话折叠后的标题；挂载会话引用功能时，还会在 `_meta["deepseek-harness/sessionReference"]` 下公开规范 URI。客户端可以使用 `title ?? sessionId` 作为资源链接名称。若引用有效但可选服务未挂载，系统会返回「功能不可用」RPC 错误；准备失败会发生在占用进行中轮次槽位并调用 agent send 之前。引用准备过程单独拥有中止控制权，因此 `session/cancel` 和桥接释放都能停止待处理的读取。选择器 UI 仍由 ACP 客户端负责，因为 ACP 未定义跨会话提及菜单。
+
+## 预算与保留策略
+
+最多三个引用中的每一个默认独立限制在 65,536 个 UTF-8 字节以内，不设置完整提示词的总预算。保留策略会优先保留当前压缩检查点和最新的对话单元，再丢弃较旧的非检查点消息。若保留文本过大，系统使用 `dsh-retention` 进行首尾切片并记录准确的省略字节数；若某个源的固定序列化字段无法装入其上限，整个准备过程会失败，不会输出部分上下文。
+
+## 考虑过的替代方案
+
+- **等待 SQLite FTS5**：不予采纳，因为快照正确性依赖按准确 id 读取和规范表层折叠，而不是内容搜索。FTS 只改进候选发现。
+- **把提及标记语法放入 `Agent.send()`**：不予采纳，因为这会迫使核心协议解析 TUI／ACP 的表现层，并阻止带类型的非文本宿主复用同一语义层。
+- **在 TUI 和 ACP 中分别实现引用**：不予采纳，因为投影、安全警告、保留策略和持久化会在不同宿主之间逐渐偏离。
+- **在提示词旁放置单独的用户角色上下文消息**：不予采纳，因为相邻的两条用户消息会削弱提示词的指示语绑定：在 `@foo what does this session discuss?` 中，模型可能把「this session」解析为当前对话，而不是被引用的快照。
+- **在调用 `send()` 前由宿主合并前缀**：不予采纳，因为 `agent/prompt-submit` 必须只检查和改写直接提示词。最终生效的提示词与附加上下文只有在 AgentLoop 接纳后才汇合；此时 AgentLoop 可以把 `allow.content` 改写一致应用于合并后的模型内容和 `envelope.displayContent`。若由宿主更早组装，就会向该钩子暴露快照字节，或使这两个视图发生偏离。
+- **回放原始源日志或恢复被遮蔽的事件**：不予采纳，因为压缩定义了当前模型表层，并且可能有意淘汰敏感或开销高昂的历史内容。
+- **恢复或 fork 源会话**：不予采纳，因为本功能只为一条目标消息提供只读背景，不提供身份或生命周期连续性。
+- **在请求时重新读取源会话并注入**：不予采纳，因为这会让引用变得不确定，取消竞态可能改变其字节内容，目标回放也会依赖可变的外部状态。
+
+## 验证
+
+单元与集成测试覆盖 URI 无损往返与文本边界标点、显式格式错误的引用、会考虑标题的候选排序、终端控制字符转义、投影排除规则、提示词封套的非递归投影、与后端无关的压缩检查点、标签安全封套、去重、自引用、数量限制、读取的全有或全无、存储读取不结束时取消提示词、逐源独立字节保留、冻结的消息所有权、提示词阻止、send／steer 放置方式、标题隔离、功能缺失、包含标题信息的 ACP 会话列表、普通 ACP 资源链接、不透明的 ACP 命令参数，以及精简的 TUI／ACP 回放。无密钥 TUI 快照会运行真实的 agent loop（智能体循环）：源表层用一个压缩检查点替换旧的用户／assistant 历史，目标会话提交一个提及标记，捕获到的模型请求只包含一条用户消息，其中依次为快照、请求分隔符和当前提示词，并且不包含任一被遮蔽的字符串。
+
+## 后果
+
+新插件构成稳定的语义边界，不会新增持久化 schema、事件类型、FTS 依赖、源会话订阅或对压缩所遮蔽内容的访问。标准 TUI／ACP 演示组合包会显式挂载它，并在各自的配置中暴露引用数量和逐源字节上限；自定义宿主在挂载该服务并适配输入前保持不变。引用上下文会在配置的界限内增大目标历史，随后可由目标会话的普通压缩进行摘要；完成压缩后，源会话便不再相关。