Merge latest master into invariant service seam

2026-08-15 21:04:50 +00:00 · 2026-07-20 20:19:01 +08:00
parent 2f3ca3027b 21718d5ba7
commit 2c04056348
184 changed files with 1882 additions and 364 deletions
--- a/.agents/notes/implemented/architecture/2026-06-14-session-persistence.md
+++ b/.agents/notes/implemented/architecture/2026-06-14-session-persistence.md
@@ -13,7 +13,7 @@ The [event-sourced model](2026-06-11-event-sourced-sessions.md) makes the append
 Persistence is an abstract **capability seam** ([capability seams](2026-06-13-capability-seams.md), the `dsh-bash` template), not loop or core logic:

 1. **Interface** (`dsh-session-persistence`, `ctx.sessionPersistence`) — an abstract `SessionPersistence` service: `create`/`append`/`load`/`list`. Its persisted unit IS the existing `SessionEvent` (`{ type, seq, time, data }`), reused verbatim — no conversion type.
-2. **Implementation** (`dsh-session-persistence-jsonl`) — an append-only JSONL log per session (a `SessionHeader` line then one `SessionEvent` per line, verbatim **including `assistant/chunk`**).
+2. **Implementation** (`dsh-session-persistence-jsonl`) — an append-only logical JSONL log per session (a `SessionHeader` line then one `SessionEvent` per line, verbatim **including `assistant/chunk`**), encoded as [checksummed Zstandard frames by default](2026-07-19-zstandard-jsonl-session-logs.md) or raw lines by configuration.

 Key choices recorded here because they are durable, contested, and surprising:

--- a/.agents/notes/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md
+++ b/.agents/notes/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md
@@ -28,7 +28,7 @@ Six methods (five required + an optional lifecycle hook) — the only seam betwe

 ### The opaque torn marker

-The single design choice that keeps the seam clean: the crash-repair "where is the torn tail" token is OPAQUE to the coordinator. The coordinator computes the synthetic closers (it owns `interruptedTurnClosers` from `dsh-session`), but it only ever tests `tornMarker !== undefined` and passes the value straight back to `commitRepair` — it never inspects it. Each backend picks its own marker type: JSONL uses the byte offset to truncate to, SQLite the seq to delete from (both happen to be `number`). The JSONL backend folds its `committedBytes < buffer.byteLength` comparison INSIDE the hook so the returned marker is already `number | undefined`; without that fold the coordinator would have to know about byte lengths.
+The single design choice that keeps the seam clean: the crash-repair "where is the torn tail" token is OPAQUE to the coordinator. The coordinator computes the synthetic closers (it owns `interruptedTurnClosers` from `dsh-session`), but it only ever tests `tornMarker !== undefined` and passes the value straight back to `commitRepair` — it never inspects it. Each backend picks its own marker type: JSONL carries the byte offset to truncate to plus any complete events decoded from an incomplete final frame, while SQLite carries the seq to delete from. The coordinator therefore knows neither byte lengths nor frame recovery state.

 ## Testing

--- a/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.i18n.yaml
+++ b/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.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
+2026-07-19-zstandard-jsonl-session-logs.md: 09d30594fe31eed138a128dabc1947b15857808d
+2026-07-19-zstandard-jsonl-session-logs.zh.md: 131531d9dba7cb01407191bf937f8b0ee3c6860a
--- a/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.md
+++ b/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.md
@@ -0,0 +1,57 @@
+# Agent Note: Zstandard JSONL session logs
+
+Status: implemented
+
+English | [中文](2026-07-19-zstandard-jsonl-session-logs.zh.md)
+
+## Problem
+
+The JSONL persistence backend keeps every `SessionEvent` verbatim, including high-volume `assistant/chunk` records. Raw text makes logs inspectable but spends storage and I/O on repeated JSON keys and model text. Compression must retain the existing append/fsync commit boundary, collision-safe first materialization, crash repair, and metadata-only listing; rewriting a whole compressed file after every turn would discard those properties.
+
+The encoding also has to remain explicit at the deployment boundary. Snapshot fixtures and external line readers require raw JSONL, while a backend cannot safely guess between compressed and raw artifacts in one root or silently migrate pre-release session data.
+
+## Decision
+
+### Configuration and suffix ownership
+
+`dsh-session-persistence-jsonl` accepts `compression?: 'zstd' | 'none'` and explicitly resolves omission to `'zstd'`. Zstandard artifacts end in `.jsonl.zstd`; `'none'` retains the original newline-delimited UTF-8 `.jsonl` representation. `SessionLocation.kind` remains `'jsonl'`, because both encodings carry the same logical record format, and `SESSION_FORMAT_VERSION` remains `0` under the repository's pre-release reject-without-migration policy.
+
+Each persistence root belongs to one encoding. A one-time discovery preflight rejects any opposite suffix, and targeted load, live-adoption, listing, and materialization paths repeat the relevant suffix check after an initially empty preflight. The error names the incompatible artifact and directs the deployment to the matching configuration or a separate root. There is no migration, dual read, dual write, or extension-based fallback.
+
+### Frame and write path
+
+The compressed artifact is a standard concatenation of independent [Zstandard frames](https://datatracker.ietf.org/doc/html/rfc8878): one checksummed frame containing exactly the header line, followed by one checksummed frame for every durable append batch. Normal loop batches are turn commits, so frame boundaries preserve the existing persistence checkpoint without making the storage layer depend on turn event types.
+
+Compression uses Node's built-in [`zstdCompress` and `zstdDecompress`](https://nodejs.org/download/release/v22.19.0/docs/api/zlib.html), available at the repository's Node 22.19 floor. The backend enables `ZSTD_c_checksumFlag`, otherwise accepts Node's defaults, and exposes neither a compression-level knob nor a new dependency. The API is marked experimental by Node, so the Node 22.19, 24, and 26 compatibility gate exercises the exact helper.
+
+First materialization compresses the two initial frames before opening the temporary file, then keeps the existing write, file `fsync`, collision-safe hard-link publication, and directory `fsync` sequence. Later batches are compressed before opening the destination and appended at EOF. A caught write or file-sync failure truncates to the prior byte length, syncs the rollback, and rethrows so the coordinator can retry the unchanged batch.
+
+### Read, listing, and crash recovery
+
+A frame-boundary scanner reads the standard magic, variable header fields, block headers and payload sizes, and optional checksum trailer. It does not interpret compressed blocks. Complete frames are decompressed independently and sequentially, which validates their checksums, and their plaintext is passed to the existing JSONL scanner. A checksum/decompression failure in any complete frame, a malformed complete-frame JSONL tail, or invalid frame structure is corruption and rejects.
+
+Listing reads in bounded chunks only until the first complete frame is available, validates and decompresses that header frame, and never reads an event frame. The dedicated header frame therefore preserves metadata-only listing even for very large session logs.
+
+EOF inside the final frame is a recoverable torn tail. Node's decoder is given the available frame prefix; every complete newline-terminated event it emits is retained. Repair truncates from that frame's starting byte and appends one new checksummed frame containing the recovered complete events followed by the coordinator's synthetic tool, step, and turn closers. If the tear occurs before any complete event is decodable, repair drops the partial frame and retains all prior complete frames.
+
+### Consumers and verification
+
+The CLI, ACP, and stdio app bundles expose symmetric `persistenceCompression` pass-through configuration. Snapshot recording and replay compositions select `'none'` explicitly because committed fixtures are raw JSONL inputs to replay and normalization; ordinary runtime compositions use the compressed default.
+
+The shared persistence and coordinator contracts run against both encodings. Backend tests cover standard framing and checksum interoperability, header-only listing, append rollback, encoding mismatch rejection, complete-frame corruption, and final-frame tears through headers, blocks, and checksum trailers. Default runtime, built-bin, headless, ACP, and Python smokes assert the compressed suffix and Zstandard magic or decode the header; raw-content tests opt out explicitly.
+
+## Alternatives considered
+
+- **One frame per JSONL record** — rejected because it multiplies frame headers and checksums for high-volume chunk events and makes a physical boundary unrelated to the durable append batch.
+- **Rewrite one whole compressed stream after every append** — rejected because cost grows with log size and replacement would give up append/fsync rollback and the established collision-safe materialization mechanics.
+- **Use a streaming compressor across appends** — rejected because an interrupted encoder state does not leave independently checksummed append units, complicating bounded listing and frame-start repair.
+- **Add an external native Zstandard dependency** — rejected because the supported Node floor already provides the required codec; another native artifact would enlarge installation and executable-packaging risk without adding a required behavior.
+- **Expose compression level or keep raw JSONL as the default** — rejected because there is no deployment evidence for a second tuning policy, while `'none'` preserves the line-readable path for fixtures and integrations that need it.
+
+## Consequences
+
+- Ordinary session roots store `.jsonl.zstd` and retain append-only, fsync, rollback, and interrupted-turn recovery semantics.
+- Raw JSONL remains a deliberate configuration, but changing encoding requires a fresh/separate root or selecting the mode that matches existing artifacts.
+- One frame per durable batch adds bounded framing/checksum overhead and allows header-only listing plus repair from an exact append boundary.
+- External tools must understand concatenated Zstandard frames or consume raw-mode artifacts; generic one-shot Node decompression reads only the first independent frame, so backend reads walk frames explicitly.
+- The implementation depends on Node's experimental built-in Zstandard API without an npm dependency; the supported-version compatibility gate makes drift visible.
--- a/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.zh.md
+++ b/.agents/notes/implemented/architecture/2026-07-19-zstandard-jsonl-session-logs.zh.md
@@ -0,0 +1,57 @@
+# Agent Note: Zstandard JSONL 会话日志
+
+Status: implemented
+
+[English](2026-07-19-zstandard-jsonl-session-logs.md) | 中文
+
+## 问题
+
+JSONL 持久化后端会逐字保留每个 `SessionEvent`，其中包括数量庞大的 `assistant/chunk` 记录。原始文本便于检查，但重复的 JSON 键和模型文本会增加存储与 I/O 开销。压缩编码必须保留既有的 append/fsync 提交边界、首次物化时的无冲突发布、崩溃修复以及仅元数据列举；如果每轮都重写整个压缩文件，就会失去这些属性。
+
+编码还必须在部署边界上保持显式。快照 fixture 与外部逐行读取器需要原始 JSONL，而后端无法在同一根目录中安全猜测压缩产物与原始产物，也不能静默迁移预发布会话数据。
+
+## 决策
+
+### 配置与后缀归属
+
+`dsh-session-persistence-jsonl` 接受 `compression?: 'zstd' | 'none'`，并将省略值显式解析为 `'zstd'`。Zstandard 产物使用 `.jsonl.zstd` 后缀；`'none'` 保留原有的换行分隔 UTF-8 `.jsonl` 表示。`SessionLocation.kind` 仍为 `'jsonl'`，因为两种编码承载同一逻辑记录格式；按照仓库的预发布拒绝且不迁移策略，`SESSION_FORMAT_VERSION` 仍为 `0`。
+
+每个持久化根目录只归属于一种编码。一次性的发现预检会拒绝任何相反后缀，而针对性的加载、活跃采用、列举与物化路径会在最初空目录预检之后再次执行对应后缀检查。错误会指出不兼容产物，并要求部署选择匹配配置或单独根目录。系统不提供迁移、双重读取、双重写入或基于扩展名的兜底。
+
+### 帧与写入路径
+
+压缩产物是标准独立 [Zstandard 帧](https://datatracker.ietf.org/doc/html/rfc8878)的串联：第一个带校验和的帧只包含头部行，后续每个持久追加批次各占一个带校验和的帧。正常 agent loop 批次就是轮次提交，因此帧边界保留既有持久化检查点，同时不让存储层依赖轮次事件类型。
+
+压缩使用 Node 内置的 [`zstdCompress` 与 `zstdDecompress`](https://nodejs.org/download/release/v22.19.0/docs/api/zlib.html)，仓库最低支持的 Node 22.19 已提供这些 API。后端启用 `ZSTD_c_checksumFlag`，其余采用 Node 默认值，不公开压缩级别调节项，也不增加依赖。Node 将该 API 标记为实验性，因此 Node 22.19、24 与 26 兼容性门禁会执行同一个辅助实现。
+
+首次物化会在打开临时文件之前压缩两个初始帧，然后保留既有的写入、文件 `fsync`、避免冲突的硬链接发布与目录 `fsync` 顺序。后续批次也会先压缩，再打开目标并在 EOF 追加。捕获到写入或文件同步失败时，后端会截断到原有字节长度，同步回滚结果，再重新抛出错误，让协调器重试未变化的批次。
+
+### 读取、列举与崩溃恢复
+
+帧边界扫描器会读取标准魔数、可变头字段、块头与负载长度，以及可选校验和尾部，但不会解释压缩块。后端独立且按顺序解压完整帧，由此验证各帧校验和，再把明文交给既有 JSONL 扫描器。任何完整帧的校验和或解压失败、完整帧中畸形的 JSONL 尾部，或者无效帧结构都属于损坏并拒绝加载。
+
+列举只按有界分片读取到第一个完整帧可用为止，验证并解压该头部帧，绝不读取事件帧。因此，即使会话日志很大，专用头部帧仍能维持仅元数据列举。
+
+最终帧内部遇到 EOF 属于可恢复的撕裂尾部。后端把已有帧前缀交给 Node 解码器，并保留其产出的每个完整、以换行结束的事件。修复从该帧起始字节截断，再追加一个新的带校验和帧，其中依次包含恢复出的完整事件，以及协调器生成的工具、步骤与轮次闭合事件。如果撕裂位置尚不足以解码任何完整事件，修复会丢弃该不完整帧并保留此前全部完整帧。
+
+### 消费方与验证
+
+CLI、ACP 与 stdio 应用包公开对称的 `persistenceCompression` 透传配置。快照录制与回放组合显式选择 `'none'`，因为提交的 fixture 是回放与规范化过程使用的原始 JSONL 输入；普通运行时组合使用压缩默认值。
+
+共享持久化契约与协调器契约会针对两种编码运行。后端测试覆盖标准帧与校验和互操作性、仅头部列举、追加回滚、编码不匹配拒绝、完整帧损坏，以及横跨头部、块和校验和尾部的最终帧撕裂。默认运行时、构建后二进制、headless、ACP 与 Python 冒烟测试会断言压缩后缀与 Zstandard 魔数，或解码头部；读取原始内容的测试则显式退出压缩。
+
+## 考虑过的替代方案
+
+- **每条 JSONL 记录一个帧**——不予采纳，因为它会让大量分片事件各自承担帧头与校验和开销，并让物理边界脱离持久追加批次。
+- **每次追加都重写一个完整压缩流**——不予采纳，因为成本会随日志大小增长，而且替换操作会放弃追加/fsync 回滚和既有的无冲突物化机制。
+- **跨追加使用流式压缩器**——不予采纳，因为编码器状态中断后不会留下可独立校验的追加单元，从而使有界列举与按帧起点修复更复杂。
+- **增加外部原生 Zstandard 依赖**——不予采纳，因为受支持的 Node 最低版本已经提供所需编解码器；另一个原生产物会增加安装与可执行文件打包风险，却不增加必需行为。
+- **公开压缩级别或继续默认使用原始 JSONL**——不予采纳，因为没有部署证据支持第二种调节策略，而 `'none'` 已为需要逐行读取的 fixture 与集成保留路径。
+
+## 后果
+
+- 普通会话根目录存储 `.jsonl.zstd`，并保留仅追加、fsync、回滚与中断轮次恢复语义。
+- 原始 JSONL 仍是显式配置，但切换编码需要使用全新或单独根目录，或者选择与既有产物匹配的模式。
+- 每个持久批次一个帧会增加有界的帧与校验和开销，同时支持仅头部列举和从精确追加边界开始修复。
+- 外部工具必须理解串联的 Zstandard 帧，或者消费原始模式产物；Node 通用的一次性解压只读取第一个独立帧，因此后端读取会显式遍历各帧。
+- 实现依赖 Node 的实验性内置 Zstandard API，但不增加 NPM 依赖；受支持版本兼容性门禁会暴露 API 漂移。
--- a/.agents/notes/implemented/feature/2026-07-12-subagent-persona-tool-filter-and-depth.md
+++ b/.agents/notes/implemented/feature/2026-07-12-subagent-persona-tool-filter-and-depth.md
@@ -49,9 +49,11 @@ The global registry remains live. A deny-only filter admits a later global name

 The depth limit bounds recursive delegation independently of tool visibility. A top-level agent has depth zero; an in-process child has its parent's validated depth plus one. `maxDepth` is an absolute non-negative safe integer, and a start rejects before child ownership begins when the derived child depth is greater than the cap.

-Every public entry validates the domain rather than relying on one model-facing configuration path. Negative values, fractions, negative zero, non-finite values, unsafe integers, malformed stored parent depth, and derived overflow all reject. Omitting the cap leaves depth unbounded by this mechanism.
+The effective parent depth is the greater of durable `SessionHeader.delegationDepth` and runtime `AgentOptions.subagentDepth`. An in-process child records its derived depth in the session header, and resume restores that header, so a restart cannot lower the recursion count.

-A deployment can combine depth and filtering. For example, it may keep the delegation tool visible at depth one but set `maxDepth: 1`, or deny the delegation tool entirely in children. Neither choice changes the provider's conversation-history behavior.
+Every public entry validates the domain rather than relying on one model-facing configuration path. Negative values, fractions, negative zero, non-finite values, unsafe integers, malformed stored parent depth, and derived overflow all reject. A direct `SubagentStartRequest` may omit the cap to leave depth unbounded; loader-resolved `dsh-tool-subagent` configuration instead defaults to `3`, accepts a numeric override, and uses explicit `'provider-managed'` to omit the cap for an out-of-process provider whose deployment owns its recursion budget. Three is a small finite default that still permits a root plus three descendant generations: the [SDK helper's generated subagent entries](../../../../packages/sdk/helper/src/features/builtin/index.ts) and [JSON-RPC example](../../../../examples/jsonrpc-agent/cordis.yml) use that general policy, while the shipped interactive ACP, headless, and REPL examples pin one. A numeric tool cap fails at provider mount when the provider lacks `depthLimit`.
+
+A deployment can combine depth and filtering, but the numeric cap does not synthesize a filter. The delegation tool stays visible at the cap because authorization may depend on runtime state; every attempted start checks the calling agent's current durable and runtime depth, and a rejected start returns an errored tool result without publishing a child. A deployment may separately deny delegation tools in children when its visibility policy is static. Neither choice changes the provider's conversation-history behavior.

 ### Capability gating keeps providers honest

@@ -83,10 +85,10 @@ A security design would need a separate authority representation, propagation ru

 **Hide only tool schemas.** Presentation-only filtering lets the model execute a tool that the prompt says does not exist through Code Mode or a forged call. One resolver governs both presentation and execution instead.

-**Use only tool filtering to stop recursion.** Removing the delegation tool is useful but provider-specific and does not protect direct service callers or alternate delegation tools. Absolute depth is an independent structural bound.
+**Encode the depth cap as an automatic tool filter.** A creation-time filter snapshots a decision that may depend on runtime state, affects only one configured tool name, and does not protect direct service callers or alternate delegation tools. The provider instead enforces the absolute cap at every start.

 ## Consequences

 Contributors can configure child role, visible global tools, and recursion without defining new providers. Capability checks fail before ownership starts, unpublished setup makes the first request consistent, and one tool resolver prevents presentation/execution drift.

-The cost is that deployments must understand live allow/deny behavior and the distinction between visibility and authority. Provider authors must advertise each supported control accurately, and in-process providers must install every requested contribution before publication. The controls deliberately do not solve security confinement or parent-to-child non-escalation.
+The cost is that deployments must understand live allow/deny behavior and the distinction between visibility and authority. A model may call a visible delegation tool after the current depth policy forbids another child and receive an error. Provider authors must advertise each supported control accurately, and in-process providers must install every requested contribution before publication. The controls deliberately do not solve security confinement or parent-to-child non-escalation.
--- a/.agents/notes/implemented/testing/2026-06-19-acp-snapshot-tests.md
+++ b/.agents/notes/implemented/testing/2026-06-19-acp-snapshot-tests.md
@@ -40,7 +40,7 @@ Replay is positional and therefore permits only one in-flight model stream per s

 ### Recording harvests the log; keyless replay needs a providerless config

-Recording runs the scenario with the real `llm-deepseek` adapter and the JSONL persistence backend, then copies the produced `.jsonl` into the scenario dir. Per-event appends are durable, but the harness shuts the subprocess down gracefully (close stdin → `await ctx.dispose()`) before harvesting so the final events are flushed. `llm-replay` itself does no recording — it is replay-only.
+Recording runs the scenario with the real `llm-deepseek` adapter and the JSONL persistence backend configured with `persistenceCompression: 'none'`, then copies the produced `.jsonl` into the scenario dir. The explicit raw mode keeps committed replay fixtures line-readable while ordinary deployments use the backend's compressed default. Per-event appends are durable, but the harness shuts the subprocess down gracefully (close stdin → `await ctx.dispose()`) before harvesting so the final events are flushed. `llm-replay` itself does no recording — it is replay-only.

 Replay uses a `cordis.snapshot.yml` overlay that replaces the real adapter with `llm-replay` while retaining the live composition. Recording uses the ordinary config and a harness-supplied persistence root. Replay mode skips `.env` loading, so a stray API key cannot trigger a live call. See the [single-source config Agent Note](2026-07-04-single-source-acp-replay-config.md).

--- a/AGENTS.md
+++ b/AGENTS.md
@@ -89,7 +89,7 @@ pnpm run hygiene
 out=$(printf 'echo ci smoke\n' | pnpm run demo:echo 2>&1)
 printf '%s\n' "$out" | grep -q '\[tool call\] echo({"text":"ci smoke"})'
 printf '%s\n' "$out" | grep -q '\[tool result\] ECHO: CI SMOKE'
-test -n "$(find .sessions -path '.sessions/cwd-*/main-session-*.jsonl' -type f -print -quit)"
+test -n "$(find .sessions -path '.sessions/cwd-*/main-session-*.jsonl.zstd' -type f -print -quit)"
 rm -rf .sessions
 pnpm exec vitest run --config vitest.e2e.config.ts packages/examples/stdio-demo/tests/built-bin.e2e.ts packages/examples/cli-demo/tests/built-bin.e2e.ts packages/examples/acp-demo/tests/built-bin.e2e.ts packages/ui/jsonrpc/tests/built-scope-carrier.e2e.ts packages/workflow/workflow-workerthread/tests/built-worker.e2e.ts packages/code-runtime/code-runtime-worker/tests/built-lib.e2e.ts
 ```
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -60,7 +60,7 @@ The shipped loop drains prompt-to-checkpoint work through plugin-visible service

 A **session** is an append-only log. Each ordinary **turn** claims one queued `send()` item; injection claims none. A claimed `send()` successor awaits the preceding claimed ordinary turn's checkpoint but may share its `running` interval ([decision](../.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md)). A turn ends when model and plugins stop it. A **step** is one model request plus tools. Below ([sequence companion](agent-lifecycle.md)), quotes mark durable events; other names are extension points.

-Startup resolves identity. No id mints `<config-id>-session-<uuid>`; `sessionId` resumes or creates; `resumeSessionId` requires history. Active failures emit `agent-loop/config-start-failed(sessionId, error)`, so front doors reject work; teardown stays silent.
+No id mints `<config-id>-session-<uuid>`; `sessionId` resumes/creates; `resumeSessionId` needs history. Resume restores lineage, seeds, and delegation depth pre-publication. Failures emit `agent-loop/config-start-failed(sessionId, error)`; front doors reject; teardown stays silent.

 ### Turn Flow

@@ -138,7 +138,7 @@ The session log is the source of truth. `deriveMessages()` projects session even

 **Model-visible ⟺ logged**: the log reconstructs every request — messages at `step/start` fronted by the header's session prefix, and headers by folding `request/header` — and the package-owned `dsh-agent-loop/invariant` can assert it through `ctx.invariants` ([reconstructability](../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md)).

-Durability is a plugin concern. Persistence backends buffer synchronous `session/event` notifications and the loop awaits a turn-end checkpoint before moving on. The `SessionPersistence` seam stores `SessionEvent` directly, with metadata in `SessionHeader`; JSONL and SQLite share one contract suite.
+Durability is a plugin concern. Backends buffer synchronous `session/event` notifications; the loop awaits a turn-end checkpoint. `SessionPersistence` stores `SessionEvent` directly and metadata in `SessionHeader`; JSONL defaults to checksummed Zstandard, with SQLite under one contract.

 ### Model Content

--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -58,6 +58,8 @@ export interface Config {
  dshHome?: string
  /** Directory the JSONL session backend writes under. Defaults to `./.sessions`. */
  persistenceRoot?: string
+  /** JSONL artifact encoding; defaults to checksummed Zstandard frames. */
+  persistenceCompression?: JsonlCompression
  /** Controls automatic AGENTS.md/CLAUDE.md loading; configure a byte budget or set `false`. */
  workspaceContext: agentCore.Config['workspaceContext']
  /** Skill registry, local-provider, and model-facing consumer config forwarded to agent-spine-demo. */
@@ -69,9 +71,9 @@ export interface Config {
 }
 ```

-Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)
+Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`JsonlCompression`](../packages/session-persistence/session-persistence-jsonl/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)

-Source: [`packages/examples/acp-demo/src/index.ts:33`](../packages/examples/acp-demo/src/index.ts)
+Source: [`packages/examples/acp-demo/src/index.ts:36`](../packages/examples/acp-demo/src/index.ts)

 ## `@deepseek-ai/dsh-agent-loop`

@@ -227,6 +229,8 @@ export interface Config {
  dshHome?: string
  /** Directory the JSONL session backend writes under. Defaults to `./.sessions`. */
  persistenceRoot?: string
+  /** JSONL artifact encoding; defaults to checksummed Zstandard frames. */
+  persistenceCompression?: JsonlCompression
  /** Skill registry, local-provider, and model-facing consumer config. */
  skills?: agentCore.SkillConfig
  /** Model-facing bash tool config forwarded through agent-spine-demo. */
@@ -238,9 +242,9 @@ export interface Config {
 }
 ```

-Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)
+Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`JsonlCompression`](../packages/session-persistence/session-persistence-jsonl/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools)

-Source: [`packages/examples/cli-demo/src/index.ts:22`](../packages/examples/cli-demo/src/index.ts)
+Source: [`packages/examples/cli-demo/src/index.ts:25`](../packages/examples/cli-demo/src/index.ts)

 ## `@deepseek-ai/dsh-code-runtime-worker`

@@ -757,10 +761,15 @@ export interface Config {
   * (bash calls, subprocesses). Sessions group under per-cwd subdirectories.
   */
  root: string
+  /** Physical encoding; defaults to checksummed Zstandard frames. */
+  compression?: JsonlCompression
 }
+
+/** Physical encoding selected for JSONL session artifacts. */
+export type JsonlCompression = 'zstd' | 'none'
 ```

-Source: [`packages/session-persistence/session-persistence-jsonl/src/index.ts:24`](../packages/session-persistence/session-persistence-jsonl/src/index.ts)
+Source: [`packages/session-persistence/session-persistence-jsonl/src/index.ts:36`](../packages/session-persistence/session-persistence-jsonl/src/index.ts)

 ## `@deepseek-ai/dsh-session-persistence-sqlite`

@@ -925,6 +934,8 @@ export interface Config {
  dshHome?: string
  /** Directory the JSONL session backend writes under. Defaults to `./.sessions`. */
  persistenceRoot?: string
+  /** JSONL artifact encoding; defaults to checksummed Zstandard frames. */
+  persistenceCompression?: JsonlCompression
  /** stdin-chat banner printed once on start. Defaults to `'ready.'`. */
  welcome?: string
  /** Terminal front-door selection and pi-tui presentation settings. */
@@ -957,9 +968,9 @@ export interface UiConfig {
 export type TerminalMode = 'auto' | 'readline' | 'tui'
 ```

-Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools) · [`uiTui`](../packages/ui/tui/src/index.ts)
+Depends on: [`agentCore`](../packages/examples/agent-spine-demo/src/index.ts) · [`JsonlCompression`](../packages/session-persistence/session-persistence-jsonl/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools) · [`uiTui`](../packages/ui/tui/src/index.ts)

-Source: [`packages/examples/stdio-demo/src/index.ts:75`](../packages/examples/stdio-demo/src/index.ts)
+Source: [`packages/examples/stdio-demo/src/index.ts:78`](../packages/examples/stdio-demo/src/index.ts)

 ## `@deepseek-ai/dsh-subagent-acp`

@@ -1206,8 +1217,7 @@ export interface Config {
  /**
   * Tool filter applied to every child. Filtered tools disappear from its
   * prompt and reject execution. Requires the provider's `toolFilter`
-   * capability; unknown names fail startup. Children otherwise see this tool,
-   * so deny it or set `maxDepth` to bound recursion.
+   * capability; unknown names fail startup.
   */
  toolFilter?: {
    /** Global tool names the child keeps; everything else is removed. */
@@ -1216,10 +1226,15 @@ export interface Config {
    deny?: string[]
  }
  /**
-   * Maximum child depth. Requires the provider's `depthLimit` capability and a
-   * non-negative safe integer. Omission is unbounded.
+   * Maximum child depth: a non-negative safe integer (default `3`; `0` forbids
+   * delegation entirely), or `'provider-managed'` to send no cap. A numeric cap
+   * requires the provider's `depthLimit` capability (mount fails loud
+   * otherwise). The provider checks the calling agent's current depth at every
+   * start; the tool remains model-visible so runtime policy owns rejection.
+   * `'provider-managed'` is for an out-of-process provider (ACP) whose
+   * recursion budget belongs to the child harness's own deployment.
   */
-  maxDepth?: number
+  maxDepth?: number | 'provider-managed'
 }
 ```

--- a/docs/cordis-catalog/events.md
+++ b/docs/cordis-catalog/events.md
@@ -585,7 +585,7 @@ A ready child settled. Scope-filtered dispatch uses the same delegating parent c

 Types: [Scoped](../core-data-structures/scope.md) · [SubagentService](../core-data-structures/subagent.md)

-Source: [`packages/subagent/subagent/src/index.ts:112`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:139`](../../packages/subagent/subagent/src/index.ts)

 ### `subagent/provider-added` — emit

@@ -602,7 +602,7 @@ A provider became resolvable in the registry.

 Types: [SubagentProvider](../core-data-structures/subagent.md)

-Source: [`packages/subagent/subagent/src/index.ts:86`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:113`](../../packages/subagent/subagent/src/index.ts)

 ### `subagent/provider-removed` — emit

@@ -617,7 +617,7 @@ A provider left the registry. Accepted runs remain holder-owned.
 'subagent/provider-removed'(name: string): void
 ```

-Source: [`packages/subagent/subagent/src/index.ts:92`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:119`](../../packages/subagent/subagent/src/index.ts)

 ### `subagent/start` — emit

@@ -639,7 +639,7 @@ A provider established a ready child. For in-process providers, `ctx.agents.get(

 Types: [Scoped](../core-data-structures/scope.md) · [SubagentService](../core-data-structures/subagent.md)

-Source: [`packages/subagent/subagent/src/index.ts:103`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:130`](../../packages/subagent/subagent/src/index.ts)

 ## `system-prompt/*`

--- a/docs/cordis-catalog/services.md
+++ b/docs/cordis-catalog/services.md
@@ -216,7 +216,7 @@ roots(): Agent[]

 Types: [Agent](../core-data-structures/core.md) · [SessionId](../core-data-structures/core.md)

-Source: [`packages/core/agent/src/index.ts:217`](../../packages/core/agent/src/index.ts)
+Source: [`packages/core/agent/src/index.ts:223`](../../packages/core/agent/src/index.ts)

 ## `ctx.approval` — `ApprovalService`

@@ -736,9 +736,9 @@ Persistence is intentionally not implemented here — persistence plugins subscr
 * Create a session owned by the calling fiber: disposing that fiber stops
 * event notification and removes the session from the store. `options.seed`
 * populates the session with a copy of those events (replay/fork);
- * `options.meta` attaches creation metadata (validated absolute `cwd`,
- * `parentSession` lineage) as the immutable {@link SessionHeader} (the store
- * fills `version`/`id`/`createdAt`).
+ * `options.meta` attaches creation metadata (validated absolute `cwd`, seed
+ * and parent lineage, and delegation depth) as the immutable
+ * {@link SessionHeader} (the store fills `version`/`id`/`createdAt`).
 *
 * For an agent whose session must be torn down IN ORDER with its loop (so the
 * loop's final flush is captured before the store attachment ends), do NOT use this
@@ -850,7 +850,7 @@ fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId):

 Types: [CreateSessionOptions](../core-data-structures/persistence.md) · [Session](../core-data-structures/session.md) · [SessionId](../core-data-structures/core.md)

-Source: [`packages/core/session/src/index.ts:549`](../../packages/core/session/src/index.ts)
+Source: [`packages/core/session/src/index.ts:553`](../../packages/core/session/src/index.ts)

 ## `ctx.skills` — `SkillService`

@@ -964,7 +964,7 @@ async start(name: string, request: SubagentStartRequest): Promise<SubagentRun>

 Types: [SubagentProvider](../core-data-structures/subagent.md) · [SubagentRun](../core-data-structures/subagent.md) · [SubagentStartRequest](../core-data-structures/subagent.md)

-Source: [`packages/subagent/subagent/src/index.ts:153`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:180`](../../packages/subagent/subagent/src/index.ts)

 ## `ctx.systemPrompt` — `SystemPrompt`

--- a/docs/core-data-structures/persistence.md
+++ b/docs/core-data-structures/persistence.md
@@ -60,12 +60,18 @@ interface SessionHeader {
   * boundary lets resume and replay distinguish parent history from child work.
   */
  readonly seedLength?: number
+  /**
+   * Delegation depth: absent (zero) for a top-level session, parent depth + 1
+   * for a subagent child. Persisted so a recursion budget survives restart and
+   * resume — a runtime-only depth would reset a resumed child to top-level.
+   */
+  readonly delegationDepth?: number
 }
 ```

 ## `CreateSessionOptions` — seeding and metadata

-Creating a `Session` through the store takes a `seed` (replay/fork an existing event log) and `meta` (the storage-level fields the store folds into a `SessionHeader`). The store fills in `version`/`id` and defaults `createdAt`; the caller supplies the validated absolute `cwd`, the `parentSession` lineage, the `seedLength` seed boundary, and — only when reconstructing a persisted session — the original `createdAt` to preserve it.
+Creating a `Session` through the store takes a `seed` (replay/fork an existing event log) and `meta` (the storage-level fields the store folds into a `SessionHeader`). The store fills in `version`/`id` and defaults `createdAt`; the caller supplies the validated absolute `cwd`, the `parentSession` lineage, the `seedLength` seed boundary, the `delegationDepth`, and — only when reconstructing a persisted session — the original `createdAt` to preserve it.

 ```ts type-equiv
 /**
@@ -85,6 +91,7 @@ interface CreateSessionOptions {
    readonly parentSession?: SessionId
    readonly createdAt?: number
    readonly seedLength?: number
+    readonly delegationDepth?: number
  }
 }
 ```
@@ -95,7 +102,7 @@ Replay/fork is therefore `ctx.sessions.create(id, { seed: seedEvents })`; resumi

 Both implement the same abstract `SessionPersistence` (locate/create/append/load/list over `SessionEvent`) and pass `runPersistenceContract`, proving the seam is genuinely backend-agnostic:

- **[dsh-session-persistence-jsonl](../../packages/session-persistence/session-persistence-jsonl)** — an append-only JSONL log per session with crash-safe atomic writes, the interrupted-turn crash recovery above, and a read/replay path.
+- **[dsh-session-persistence-jsonl](../../packages/session-persistence/session-persistence-jsonl)** — an append-only logical JSONL log per session, stored as checksummed concatenated Zstandard frames by default or raw lines by configuration, with crash-safe atomic writes, interrupted-turn recovery, and a read/replay path.
 - **[dsh-session-persistence-sqlite](../../packages/session-persistence/session-persistence-sqlite)** — `node:sqlite`, one row per `SessionEvent`. The row shape `(session_id, seq, type, time, data, source_event_seqs, surface_op)` maps 1:1 onto the event, including optional surface metadata, so there is no parallel persisted schema to keep in sync.

 Multiple backends sharing one on-disk session coordinate writes through the [shared persistence write-coordinator](../../.agents/notes/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md).
--- a/docs/core-data-structures/subagent.md
+++ b/docs/core-data-structures/subagent.md
@@ -237,5 +237,5 @@ interface SubagentProvider {

 The spawn and fork backends create an ordinary agent through `parent.ctx`, pass cancellation into core creation, and dispose through `AgentHandle`. Provider removal blocks new starts without revoking accepted runs. Each child gets a new flat scope rather than inheriting parent registrations. Depth and fork seeding reuse existing agent and session vocabulary:

- **Delegation depth** is a merge-extensible `AgentOptions.subagentDepth` field (`0` for a top-level agent, parent + 1 for a child). Only `undefined` means top level; every stored present value must be a non-negative safe integer. The seam owns it — the loop neither sets nor reads it — so a nested spawn validates its parent's stored depth, rejects a derived child depth outside the safe-integer domain, and applies a defined absolute `request.maxDepth` cap to that child.
+- **Delegation depth** is durable `SessionHeader.delegationDepth` plus the merge-extensible runtime field `AgentOptions.subagentDepth`; absence means top-level depth zero, and the greater present value is authoritative. The seam owns both fields — the loop neither sets nor reads them — so an in-process child persists parent depth + 1, resume cannot lower it, and every start rejects a derived depth outside the safe-integer domain or above a defined absolute `request.maxDepth` cap.
 - **Fork seeding** uses `CreateAgentOptions.seed` (a `SessionEvent[]` prefix threaded through `AgentLoop.createAgent` → `ctx.sessions.prepare({ seed })`, the same primitive `resume` uses). The fork backend passes a *balanced completed-turn prefix* of the parent's log — the parent's events up to and including its last `turn/end` — so the seed is contiguous-from-0 and the [invariants](../../packages/support/invariants) replay accepts it (the in-flight, unbalanced turn is excluded).
--- a/docs/event-producer-consumer.md
+++ b/docs/event-producer-consumer.md
@@ -32,10 +32,10 @@ This matrix shows which packages dispatch each harness-owned event and which pac
 | `session/disposed` | `emit` | [`packages/core/session/src/index.ts:57`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`agent-loop`](../packages/core/agent-loop), [`session-persistence`](../packages/session-persistence/session-persistence) |
 | `session/event` | `emit` | [`packages/core/session/src/index.ts:69`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`acp`](../packages/ui/acp), [`cli-demo`](../packages/examples/cli-demo), [`jsonrpc`](../packages/ui/jsonrpc), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`stdio`](../packages/ui/stdio), [`token-meter`](../packages/llm/token-meter), [`tui`](../packages/ui/tui), [`workspace-context`](../packages/context/workspace-context) |
 | `session/flush` | `parallel` | [`packages/core/session/src/index.ts:79`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`session-persistence`](../packages/session-persistence/session-persistence) |
-| `subagent/end` | `emit` | [`packages/subagent/subagent/src/index.ts:112`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`hooks-claude`](../packages/hooks/hooks-claude), [`jsonrpc`](../packages/ui/jsonrpc) |
-| `subagent/provider-added` | `emit` | [`packages/subagent/subagent/src/index.ts:86`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`emit`) | [`tool-subagent`](../packages/subagent/tool-subagent) |
-| `subagent/provider-removed` | `emit` | [`packages/subagent/subagent/src/index.ts:92`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`tool-subagent`](../packages/subagent/tool-subagent) |
-| `subagent/start` | `emit` | [`packages/subagent/subagent/src/index.ts:103`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`hooks-claude`](../packages/hooks/hooks-claude) |
+| `subagent/end` | `emit` | [`packages/subagent/subagent/src/index.ts:139`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`hooks-claude`](../packages/hooks/hooks-claude), [`jsonrpc`](../packages/ui/jsonrpc) |
+| `subagent/provider-added` | `emit` | [`packages/subagent/subagent/src/index.ts:113`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`emit`) | [`tool-subagent`](../packages/subagent/tool-subagent) |
+| `subagent/provider-removed` | `emit` | [`packages/subagent/subagent/src/index.ts:119`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`tool-subagent`](../packages/subagent/tool-subagent) |
+| `subagent/start` | `emit` | [`packages/subagent/subagent/src/index.ts:130`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`hooks-claude`](../packages/hooks/hooks-claude) |
 | `system-prompt/assemble` | `waterfall` | [`packages/core/system-prompt/src/index.ts:27`](../packages/core/system-prompt/src/index.ts) | [`system-prompt`](../packages/core/system-prompt) (`waterfall`) | [`acp`](../packages/ui/acp) |
 | `system-prompt/change` | `emit` | [`packages/core/system-prompt/src/index.ts:33`](../packages/core/system-prompt/src/index.ts) | [`system-prompt`](../packages/core/system-prompt) (`emit`) | - |
 | `tools/change` | `emit` | [`packages/core/tools/src/index.ts:116`](../packages/core/tools/src/index.ts) | [`tools`](../packages/core/tools) (`emit`) | - |
--- a/docs/glossary.md
+++ b/docs/glossary.md
@@ -14,4 +14,4 @@ FIXME(glossary-completeness): Expand this glossary before the first release so i
 - **shadowing** — most-specific-wins name resolution: a scoped tool/section/variable replaces its same-named global twin for that scope alone. The per-agent persona and per-agent tool-variant mechanism.
 - **restriction / scope-local registration** — a restriction (`tools.restrict`) filters the GLOBAL tool surface for one scope (compose by intersection); scope-local registrations are merged after that filter. A filtered-away global tool is absent from the prompt AND refuses execution, indistinguishably from a nonexistent one.
 - **setup window** — the creation slot where a creator composes an agent's scoped world (`CreateAgentOptions.setup`): after the scope and agent object exist but before the agent or session is published, `agent/session-start` fires, or the first prompt is assembled. Setup registers; it never drives the agent.
- **lineage** — parent/child facts carried as data (`parentSession`, `subagentDepth`); never affects visibility. <a id="lineage"></a>
+- **lineage** — parent/child facts carried as data (`parentSession`, durable `delegationDepth`, runtime `subagentDepth`); never affects visibility. <a id="lineage"></a>
--- a/docs/i18n/terminology.md
+++ b/docs/i18n/terminology.md
@@ -65,6 +65,7 @@
 | waterfall | waterfall | waterfall（瀑布式事件） | | |
 | wheel | wheel 包 | | | Python 打包格式 |
 | worktree | worktree | | | git 工作区概念 |
+| Zstandard | Zstandard | | | RFC 8878 compression format; `zstd` remains a code value. |

 ## 双语类（中英文文本各自使用中英文）

--- a/docs/persistence-catalog.md
+++ b/docs/persistence-catalog.md
@@ -79,7 +79,7 @@ export type SessionEvent<T extends SessionEventType = SessionEventType> = {
 }[T]
 ```

-Sources: [`packages/core/session/src/types.ts:256`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:263`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:293`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:325`](../packages/core/session/src/types.ts)
+Sources: [`packages/core/session/src/types.ts:263`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:270`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:300`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:332`](../packages/core/session/src/types.ts)

 ## Events

@@ -151,7 +151,7 @@ Source: [`packages/ui/user-approval/src/index.ts:68`](../packages/ui/user-approv

 Types: [StreamChunk](core-data-structures/llm-streaming.md)

-Source: [`packages/core/session/src/types.ts:220`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:227`](../packages/core/session/src/types.ts)

 #### `assistant/message` — surface

@@ -167,7 +167,7 @@ Source: [`packages/core/session/src/types.ts:220`](../packages/core/session/src/

 Types: [ContentBlock](core-data-structures/core.md) · [TokenUsage](core-data-structures/llm-streaming.md)

-Source: [`packages/core/session/src/types.ts:227`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:234`](../packages/core/session/src/types.ts)

 ### `compact/*`

@@ -246,7 +246,7 @@ Source: [`packages/compact/compact/src/types.ts:22`](../packages/compact/compact

 Types: [ContentBlock](core-data-structures/core.md) · [MessageSource](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:214`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:221`](../packages/core/session/src/types.ts)

 ### `hook/*`

@@ -324,7 +324,7 @@ Source: [`packages/ui/permission/src/index.ts:36`](../packages/ui/permission/src

 Types: [ContentBlock](core-data-structures/core.md) · [MessageSource](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:202`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:209`](../packages/core/session/src/types.ts)

 ### `request/*`

@@ -338,7 +338,7 @@ Source: [`packages/core/session/src/types.ts:202`](../packages/core/session/src/
 'request/header': { header: EpochHeader; reason: RequestHeaderReason }
 ```

-Source: [`packages/core/session/src/types.ts:252`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:259`](../packages/core/session/src/types.ts)

 ### `sandbox/*`

@@ -369,7 +369,7 @@ Source: [`packages/sandbox/sandbox-policy/src/session-mode.ts:34`](../packages/s

 Types: [ContentBlock](core-data-structures/core.md) · [MessageSource](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:245`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:252`](../packages/core/session/src/types.ts)

 ### `step/*`

@@ -380,7 +380,7 @@ Source: [`packages/core/session/src/types.ts:245`](../packages/core/session/src/
 'step/end': { turn: number; step: number }
 ```

-Source: [`packages/core/session/src/types.ts:195`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:202`](../packages/core/session/src/types.ts)

 #### `step/start` — log-only

@@ -389,7 +389,7 @@ Source: [`packages/core/session/src/types.ts:195`](../packages/core/session/src/
 'step/start': { turn: number; step: number }
 ```

-Source: [`packages/core/session/src/types.ts:193`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:200`](../packages/core/session/src/types.ts)

 ### `todo/*`

@@ -402,7 +402,7 @@ Source: [`packages/core/session/src/types.ts:193`](../packages/core/session/src/

 Types: [TodoItem](core-data-structures/session.md)

-Source: [`packages/core/session/src/types.ts:247`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:254`](../packages/core/session/src/types.ts)

 ### `tool/*`

@@ -419,7 +419,7 @@ Source: [`packages/core/session/src/types.ts:247`](../packages/core/session/src/

 Types: [CallId](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:233`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:240`](../packages/core/session/src/types.ts)

 #### `tool/code-dispatch` — log-only

@@ -463,7 +463,7 @@ Source: [`packages/core/tools/src/code-mode.ts:34`](../packages/core/tools/src/c

 Types: [CallId](core-data-structures/core.md) · [ContentBlock](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:243`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:250`](../packages/core/session/src/types.ts)

 ### `turn/*`

@@ -481,7 +481,7 @@ Source: [`packages/core/session/src/types.ts:243`](../packages/core/session/src/

 Types: [TurnEndReason](core-data-structures/session.md)

-Source: [`packages/core/session/src/types.ts:191`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:198`](../packages/core/session/src/types.ts)

 #### `turn/start` — log-only

@@ -497,7 +497,7 @@ Source: [`packages/core/session/src/types.ts:191`](../packages/core/session/src/

 Types: [TurnTrigger](core-data-structures/session.md)

-Source: [`packages/core/session/src/types.ts:184`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:191`](../packages/core/session/src/types.ts)

 ### `user/*`

@@ -510,4 +510,4 @@ Source: [`packages/core/session/src/types.ts:184`](../packages/core/session/src/

 Types: [ContentBlock](core-data-structures/core.md) · [MessageSource](core-data-structures/core.md)

-Source: [`packages/core/session/src/types.ts:197`](../packages/core/session/src/types.ts)
+Source: [`packages/core/session/src/types.ts:204`](../packages/core/session/src/types.ts)
--- a/examples/acp-agent/advanced.cordis.snapshot.yml
+++ b/examples/acp-agent/advanced.cordis.snapshot.yml
@@ -13,6 +13,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/advanced.cordis.yml
+++ b/examples/acp-agent/advanced.cordis.yml
@@ -11,6 +11,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/both-mode.cordis.snapshot.yml
+++ b/examples/acp-agent/both-mode.cordis.snapshot.yml
@@ -15,6 +15,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/both-mode.cordis.yml
+++ b/examples/acp-agent/both-mode.cordis.yml
@@ -13,6 +13,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/code-mode-workspace-context.cordis.snapshot.yml
+++ b/examples/acp-agent/code-mode-workspace-context.cordis.snapshot.yml
@@ -14,6 +14,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/code-mode-workspace-context.cordis.yml
+++ b/examples/acp-agent/code-mode-workspace-context.cordis.yml
@@ -11,6 +11,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/code-mode.cordis.snapshot.yml
+++ b/examples/acp-agent/code-mode.cordis.snapshot.yml
@@ -15,6 +15,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/code-mode.cordis.yml
+++ b/examples/acp-agent/code-mode.cordis.yml
@@ -14,6 +14,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
          workspaceContext:
            maxBytes: 65536
          tools:
--- a/examples/acp-agent/cordis.yml
+++ b/examples/acp-agent/cordis.yml
@@ -41,12 +41,14 @@
 # The ACP server app: the agent-spine-demo spine + JSONL persistence + the ACP bridge.
 # Persistence root: $DSH_SNAPSHOT_SESSIONS_ROOT when the snapshot harness sets it
 # (so it can harvest / isolate the log), else ./.sessions for the demo.
+# Snapshot modes use raw JSONL fixtures; ordinary runs keep the compressed default.
 - id: acp-agent
  name: '@deepseek-ai/dsh-acp-demo'
  config:
    provider: deepseek
    model: deepseek-v4-flash
    persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+    persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
    workspaceContext:
      maxBytes: 65536
    # Keep the persona to identity and behavior; tool plugins own tool guidance.
@@ -94,12 +96,14 @@
  config:
    provider: spawn
    toolName: subagent
+    maxDepth: 1

 - id: tool-subagent-fork
  name: '@deepseek-ai/dsh-tool-subagent'
  config:
    provider: fork
    toolName: subagent_fork
+    maxDepth: 1


 # The worker-thread workflow engine fans a model-written JavaScript script's
--- a/examples/acp-agent/depth-two.cordis.snapshot.yml
+++ b/examples/acp-agent/depth-two.cordis.snapshot.yml
@@ -0,0 +1,36 @@
+# Keyless counterpart to depth-two.cordis.yml: apply the depth patch and replace
+# the live adapter with per-session replay.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - id: llm-deepseek
+        name: '@deepseek-ai/dsh-llm-deepseek'
+        disabled: true
+      - id: sandbox
+        name: '@deepseek-ai/dsh-sandbox-local'
+        config:
+          runnerCommand:
+            - bash
+            - -c
+            - while [ "$1" != "--" ]; do shift; done; shift; exec "$@"
+            - passthrough-runner
+          runnerFailureSignatures:
+            - 'passthrough-runner: profile rejected'
+      - id: tool-subagent
+        name: '@deepseek-ai/dsh-tool-subagent'
+        config:
+          provider: spawn
+          toolName: subagent
+          maxDepth: 2
+      - insert:
+          - id: llm-replay
+            name: '@deepseek-ai/dsh-llm-replay'
+            config:
+              providers:
+                - id: deepseek
+                  name: DeepSeek
+                  models:
+                    - id: deepseek-v4-flash
+                    - id: deepseek-v4-pro
--- a/examples/acp-agent/depth-two.cordis.yml
+++ b/examples/acp-agent/depth-two.cordis.yml
@@ -0,0 +1,13 @@
+# Depth-limit snapshot overlay: keep the default composition and allow two
+# generations of spawn children before runtime enforcement rejects another.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - id: tool-subagent
+        name: '@deepseek-ai/dsh-tool-subagent'
+        config:
+          provider: spawn
+          toolName: subagent
+          maxDepth: 2
--- a/examples/acp-agent/tests/acp.snapshot.ts
+++ b/examples/acp-agent/tests/acp.snapshot.ts
@@ -30,6 +30,7 @@ const BOTH_MODE_CONFIG = fileURLToPath(new URL('../both-mode.cordis.yml', import
 const WORKSPACE_CONTEXT_CONFIG = fileURLToPath(new URL('../workspace-context.cordis.yml', import.meta.url))
 const ADVANCED_CONFIG = fileURLToPath(new URL('../advanced.cordis.yml', import.meta.url))
 const FS_CONFIG = fileURLToPath(new URL('../fs.cordis.yml', import.meta.url))
+const DEPTH_TWO_CONFIG = fileURLToPath(new URL('../depth-two.cordis.yml', import.meta.url))

 function snapshotModeFromEnv(value: string | undefined): SnapshotSuiteOptions['mode'] {
  switch (value) {
@@ -109,6 +110,13 @@ const SCENARIOS: Scenario[] = [
  { name: 'subagent-multi', hasModelTurn: true, recorded: true },
  { name: 'subagent-fork', hasModelTurn: true, recorded: true },
  { name: 'subagent-mixed', hasModelTurn: true, recorded: true },
+  {
+    name: 'subagent-depth-two-rejection',
+    hasModelTurn: true,
+    recorded: false,
+    overridden: true,
+    configPath: DEPTH_TWO_CONFIG,
+  },
  // The workflow tool: the model writes a one-child orchestration script; the
  // child runs as a spawn subagent under the worker-thread engine (its session is the
  // child fixture), and the tool result carries the script's return value.
--- a/examples/acp-agent/tests/fixtures/live-mode-switching-2026-07-07.session.jsonl
+++ b/examples/acp-agent/tests/fixtures/live-mode-switching-2026-07-07.session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"ed16a7e7-a76f-459f-b889-d4c424d66ef6","createdAt":1783421406247,"cwd":"/Users/wwl/workspace/deepseek-harness"}
+{"type":"session","version":0,"id":"ed16a7e7-a76f-459f-b889-d4c424d66ef6","createdAt":1783421406247,"cwd":"/Users/wwl/workspace/deepseek-harness","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783421410388,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783421410388,"data":{"content":[{"type":"text","text":"你好"}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783421410389,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/advanced-toolchain/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/advanced-toolchain/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"22222222-2222-4222-8222-222222222222","createdAt":1783950001000,"cwd":"/tmp/advanced-acp","parentSession":"11111111-1111-4111-8111-111111111111"}
+{"type":"session","version":0,"id":"22222222-2222-4222-8222-222222222222","createdAt":1783950001000,"cwd":"/tmp/advanced-acp","parentSession":"11111111-1111-4111-8111-111111111111","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783957884563,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783957884563,"data":{"content":[{"type":"text","text":"Reply with exactly DIRECT_CHILD_OK and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783957884564,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/advanced-toolchain/session.2.jsonl
+++ b/examples/acp-agent/tests/snapshots/advanced-toolchain/session.2.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"33333333-3333-4333-8333-333333333333","createdAt":1783950002000,"cwd":"/tmp/advanced-acp","parentSession":"11111111-1111-4111-8111-111111111111"}
+{"type":"session","version":0,"id":"33333333-3333-4333-8333-333333333333","createdAt":1783950002000,"cwd":"/tmp/advanced-acp","parentSession":"11111111-1111-4111-8111-111111111111","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783957884700,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783957884700,"data":{"content":[{"type":"text","text":"Reply with exactly WORKFLOW_CHILD_OK and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783957884700,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/advanced-toolchain/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/advanced-toolchain/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"11111111-1111-4111-8111-111111111111","createdAt":1783950000000,"cwd":"/tmp/advanced-acp"}
+{"type":"session","version":0,"id":"11111111-1111-4111-8111-111111111111","createdAt":1783950000000,"cwd":"/tmp/advanced-acp","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783957884479,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783957884479,"data":{"content":[{"type":"text","text":"Run this advanced flow exactly once: mount a no-op Cordis plugin named snapshot-marker; use run_code to inspect the live dynamic mounts through tools.cordis_inspect; delegate once to a direct spawn child; run one workflow that delegates to another spawn child; unmount dyn-1; then reply with exactly ADVANCED_ACP_OK."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783957884486,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/bash-spill/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/bash-spill/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":0,"data":{"content":[{"type":"text","text":"Use the bash tool to print a large deterministic output, then reply DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":0,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/both-mode-turn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/both-mode-turn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"bcd7e943-7b84-4264-82d0-f64e50d0d7ce","createdAt":1783611774317,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-52lrTl"}
+{"type":"session","version":0,"id":"bcd7e943-7b84-4264-82d0-f64e50d0d7ce","createdAt":1783611774317,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-52lrTl","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783611774323,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783611774323,"data":{"content":[{"type":"text","text":"Call the run_code tool (NOT the native bash tool directly) with a program that runs exactly `echo BOTH_OK` via tools.bash and returns its output. Then reply with that output only and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783611774324,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/cancel-tool-calls/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/cancel-tool-calls/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784437195072,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1784437195072,"data":{"content":[{"type":"text","text":"Run two shell commands: wait for cancellation, then write skipped.txt."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1784437195076,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/cancel/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/cancel/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":0,"data":{"content":[{"type":"text","text":"Start a long task; this turn will be cancelled mid-stream."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":0,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/code-mode-turn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/code-mode-turn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"94cd1ae4-e1d1-4ec8-9d27-50a1f849b6b3","createdAt":1783611771392,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-BteTVR"}
+{"type":"session","version":0,"id":"94cd1ae4-e1d1-4ec8-9d27-50a1f849b6b3","createdAt":1783611771392,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-BteTVR","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783611771394,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783611771394,"data":{"content":[{"type":"text","text":"Using ONE run_code program: call the bash tool twice — exactly `echo CODE_ONE` then exactly `echo CODE_TWO` — and return the two outputs joined with a plus sign. Then reply with that joined string only and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783611771396,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/code-mode-workspace-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/code-mode-workspace-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"65fbb8a6-624c-4d6a-bf5d-a7a7d14f2b49","createdAt":1783921765266,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-uorU26"}
+{"type":"session","version":0,"id":"65fbb8a6-624c-4d6a-bf5d-a7a7d14f2b49","createdAt":1783921765266,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-uorU26","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783921765269,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783921765269,"data":{"content":[{"type":"text","text":"Using ONE run_code program, call tools.read on nested/task.txt. After the program finishes, answer the workspace handshake question using the newly discovered instructions: What is the Code Mode workspace handshake?"}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783921765275,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/config-options/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/config-options/session.jsonl
@@ -1 +1 @@
-{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0}
+{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0,"delegationDepth":0}
--- a/examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"22222222-2222-4222-8222-222222222222","createdAt":1783951000000,"cwd":"/tmp/cordis-inspect-jsdoc"}
+{"type":"session","version":0,"id":"22222222-2222-4222-8222-222222222222","createdAt":1783951000000,"cwd":"/tmp/cordis-inspect-jsdoc","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784449176717,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1784449176718,"data":{"content":[{"type":"text","text":"Inspect the exact tools service API and tools/pre-execute event with cordis_inspect, then reply with exactly CORDIS_INSPECT_JSDOC_OK."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1784449176720,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/error-finish/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/error-finish/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":0,"data":{"content":[{"type":"text","text":"This prompt triggers a recorded provider error."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":0,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/escalation-approved/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/escalation-approved/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"f3cbd087-fb45-4b32-b0f2-3082d65bfcb4","createdAt":1783860675270,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-cbBLh2"}
+{"type":"session","version":0,"id":"f3cbd087-fb45-4b32-b0f2-3082d65bfcb4","createdAt":1783860675270,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-cbBLh2","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783860675271,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"permission/preset","seq":1,"time":1783962245380,"data":{"preset":"workspace-write"}}
 {"type":"sandbox/mode","seq":2,"time":1784518116517,"data":{"mode":"workspace-write"}}
--- a/examples/acp-agent/tests/snapshots/escalation-rejected/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/escalation-rejected/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"d692fe7f-7079-4ee4-8b06-f44fd026d4ea","createdAt":1783860679475,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-Hn29Od"}
+{"type":"session","version":0,"id":"d692fe7f-7079-4ee4-8b06-f44fd026d4ea","createdAt":1783860679475,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-Hn29Od","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783860679476,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"permission/preset","seq":1,"time":1783962246267,"data":{"preset":"workspace-write"}}
 {"type":"sandbox/mode","seq":2,"time":1784518117237,"data":{"mode":"workspace-write"}}
--- a/examples/acp-agent/tests/snapshots/fs-edit/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-edit/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"736c4bd8-41bd-43fb-9030-b4df3b2a4f83","createdAt":1783352084735,"cwd":"/tmp/acp-snap-cwd-0BxHdV"}
+{"type":"session","version":0,"id":"736c4bd8-41bd-43fb-9030-b4df3b2a4f83","createdAt":1783352084735,"cwd":"/tmp/acp-snap-cwd-0BxHdV","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352084740,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352084740,"data":{"content":[{"type":"text","text":"First use the read tool to read config.txt in the current directory. Then use the edit tool (NOT bash) to replace the literal text DEBUG with RELEASE in that file. Then reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352084742,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-escalation-approved/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-escalation-approved/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"977a4820-f609-4b48-9039-adcdd921c5fe","createdAt":1784045702340,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-vmEGzd"}
+{"type":"session","version":0,"id":"977a4820-f609-4b48-9039-adcdd921c5fe","createdAt":1784045702340,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-vmEGzd","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784045702342,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"permission/preset","seq":1,"time":1784045702343,"data":{"preset":"workspace-write"}}
 {"type":"sandbox/mode","seq":2,"time":1784045702343,"data":{"mode":"workspace-write"}}
--- a/examples/acp-agent/tests/snapshots/fs-policy-reject/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-policy-reject/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"b3292503-2c3d-4677-804d-1ed6802a4bc5","createdAt":1783611702544,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-QzoqnB"}
+{"type":"session","version":0,"id":"b3292503-2c3d-4677-804d-1ed6802a4bc5","createdAt":1783611702544,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-QzoqnB","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783611702550,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783611702550,"data":{"content":[{"type":"text","text":"Do NOT use the read tool and do NOT use bash or shell commands. Immediately use the edit tool to replace the literal text blue with green in settings.txt in the current directory. Do not read the file first. After the tool result, reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783611702550,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-read-window/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-read-window/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"b5639b9d-99a9-49e4-83da-77e6caa702be","createdAt":1783352099834,"cwd":"/tmp/acp-snap-cwd-N9HCkt"}
+{"type":"session","version":0,"id":"b5639b9d-99a9-49e4-83da-77e6caa702be","createdAt":1783352099834,"cwd":"/tmp/acp-snap-cwd-N9HCkt","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352099838,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352099839,"data":{"content":[{"type":"text","text":"Use the read tool (NOT bash) with offset 5 and limit 4 to read lines 5 through 8 of big.txt in the current directory. Then reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352099840,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-read/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-read/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"a57f852d-d476-4716-a380-8a1116e4d905","createdAt":1783352072464,"cwd":"/tmp/acp-snap-cwd-PEETkS"}
+{"type":"session","version":0,"id":"a57f852d-d476-4716-a380-8a1116e4d905","createdAt":1783352072464,"cwd":"/tmp/acp-snap-cwd-PEETkS","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352072468,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352072469,"data":{"content":[{"type":"text","text":"Use the read tool (NOT bash) to read the file greeting.txt in the current directory, then reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352072470,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-terminal-card/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-terminal-card/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"e128dda9-ed11-4868-8266-0ef90d03c3d6","createdAt":1783352050748,"cwd":"/tmp/acp-snap-cwd-mrFUuk"}
+{"type":"session","version":0,"id":"e128dda9-ed11-4868-8266-0ef90d03c3d6","createdAt":1783352050748,"cwd":"/tmp/acp-snap-cwd-mrFUuk","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352050753,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352050753,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo TERMINAL_OK. Then reply with the single word DONE and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352050755,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-write-overwrite/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-write-overwrite/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"e04cc262-6c89-4586-88d7-3e919240d735","createdAt":1783352092215,"cwd":"/tmp/acp-snap-cwd-hH2sGY"}
+{"type":"session","version":0,"id":"e04cc262-6c89-4586-88d7-3e919240d735","createdAt":1783352092215,"cwd":"/tmp/acp-snap-cwd-hH2sGY","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352092220,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352092221,"data":{"content":[{"type":"text","text":"First use the read tool to read data.txt in the current directory. Then use the write tool (NOT bash) to replace its entire contents with exactly the single line: replaced. Then reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352092223,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/fs-write/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/fs-write/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"fdcab4d0-e5e4-4a06-9195-be8f7049d67e","createdAt":1783352078749,"cwd":"/tmp/acp-snap-cwd-sNvn5N"}
+{"type":"session","version":0,"id":"fdcab4d0-e5e4-4a06-9195-be8f7049d67e","createdAt":1783352078749,"cwd":"/tmp/acp-snap-cwd-sNvn5N","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352078754,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352078754,"data":{"content":[{"type":"text","text":"Use the write tool (NOT bash) to create a file named notes.txt in the current directory containing exactly the single line: hello world. Then reply with exactly the single word DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352078756,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/handshake/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/handshake/session.jsonl
@@ -1 +1 @@
-{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0}
+{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0,"delegationDepth":0}
--- a/examples/acp-agent/tests/snapshots/hook-cc-posttool-block/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-posttool-block/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"669e8682-49fc-4dff-9bc7-6280e283cbe4","createdAt":1783962504097,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-WxJGUY"}
+{"type":"session","version":0,"id":"669e8682-49fc-4dff-9bc7-6280e283cbe4","createdAt":1783962504097,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-WxJGUY","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783962504115,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783962504117,"data":{"content":[{"type":"text","text":"Call the bash tool to run exactly: echo HELLO. If the first tool result is rejected, retry that command once. Quote the final tool result verbatim and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783962504152,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-posttool-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-posttool-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"0a862642-6652-4916-b88d-b058954ab0c6","createdAt":1783352196657,"cwd":"/tmp/acp-snap-cwd-LEetSL"}
+{"type":"session","version":0,"id":"0a862642-6652-4916-b88d-b058954ab0c6","createdAt":1783352196657,"cwd":"/tmp/acp-snap-cwd-LEetSL","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352196662,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352196662,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352196664,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-pretool-ask/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-pretool-ask/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"f688431c-01a8-4326-a5c5-1b5f0fd08483","createdAt":1783352171511,"cwd":"/tmp/acp-snap-cwd-iKVciS"}
+{"type":"session","version":0,"id":"f688431c-01a8-4326-a5c5-1b5f0fd08483","createdAt":1783352171511,"cwd":"/tmp/acp-snap-cwd-iKVciS","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352171519,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352171520,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352171527,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-pretool-deny/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-pretool-deny/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"ff1c1e99-3bd4-4ef8-a954-80d607d628ba","createdAt":1783352165190,"cwd":"/tmp/acp-snap-cwd-wDnkVo"}
+{"type":"session","version":0,"id":"ff1c1e99-3bd4-4ef8-a954-80d607d628ba","createdAt":1783352165190,"cwd":"/tmp/acp-snap-cwd-wDnkVo","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352165195,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352165196,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352165198,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-promptsubmit-block/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-promptsubmit-block/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"hook/invoked","seq":1,"time":0,"data":{"turn":1,"point":"UserPromptSubmit","dialect":"claude","handlerId":"claude:UserPromptSubmit:1"}}
 {"type":"hook/result","seq":2,"time":0,"data":{"turn":1,"point":"UserPromptSubmit","handlerId":"claude:UserPromptSubmit:1","decision":"block","exitCode":2,"stderrSummary":"blocked by policy hook","durationMs":0}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-promptsubmit-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-promptsubmit-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"d03c3a83-1238-4e2e-ad9a-b86a61840a40","createdAt":1783352160541,"cwd":"/tmp/acp-snap-cwd-QUDqlk"}
+{"type":"session","version":0,"id":"d03c3a83-1238-4e2e-ad9a-b86a61840a40","createdAt":1783352160541,"cwd":"/tmp/acp-snap-cwd-QUDqlk","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352160545,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"hook/invoked","seq":1,"time":1783352160546,"data":{"turn":1,"point":"UserPromptSubmit","dialect":"claude","handlerId":"claude:UserPromptSubmit:1"}}
 {"type":"hook/result","seq":2,"time":1783352160564,"data":{"turn":1,"point":"UserPromptSubmit","handlerId":"claude:UserPromptSubmit:1","decision":"pass","exitCode":0,"durationMs":17.45639600000004}}
--- a/examples/acp-agent/tests/snapshots/hook-cc-stop-continue/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-cc-stop-continue/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"eda79fbc-8a1b-4226-b74a-f5f297484747","createdAt":1784522140642,"cwd":"/var/folders/4j/54c8wb496zxfrs1ny_21jbb00000gn/T/acp-snap-cwd-r6rWZp"}
+{"type":"session","version":0,"id":"eda79fbc-8a1b-4226-b74a-f5f297484747","createdAt":1784522140642,"cwd":"/var/folders/4j/54c8wb496zxfrs1ny_21jbb00000gn/T/acp-snap-cwd-r6rWZp","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784522140646,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1784522140647,"data":{"content":[{"type":"text","text":"Reply with the single word FIRST and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1784522140648,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-posttool-block/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-posttool-block/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"01aa6a36-e9c2-42ba-934b-30bec80a1658","createdAt":1783986962232,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-x67BsP"}
+{"type":"session","version":0,"id":"01aa6a36-e9c2-42ba-934b-30bec80a1658","createdAt":1783986962232,"cwd":"/var/folders/2c/psb0_fmx7hbgz558xjt_f0l00000gn/T/acp-snap-cwd-x67BsP","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783986962235,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783986962235,"data":{"content":[{"type":"text","text":"Call the bash tool exactly once to run: echo HELLO. Whatever tool result comes back, quote it verbatim and stop without calling another tool."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783986962240,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-posttool-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-posttool-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"39d8aabe-6457-4a0e-83b7-ee33125a3666","createdAt":1783352228436,"cwd":"/tmp/acp-snap-cwd-VGFtPi"}
+{"type":"session","version":0,"id":"39d8aabe-6457-4a0e-83b7-ee33125a3666","createdAt":1783352228436,"cwd":"/tmp/acp-snap-cwd-VGFtPi","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352228441,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352228442,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352228443,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-pretool-block/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-pretool-block/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"57a74aed-99fc-43bc-a875-6dddebf64d69","createdAt":1783352214599,"cwd":"/tmp/acp-snap-cwd-7Hbu0m"}
+{"type":"session","version":0,"id":"57a74aed-99fc-43bc-a875-6dddebf64d69","createdAt":1783352214599,"cwd":"/tmp/acp-snap-cwd-7Hbu0m","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352214604,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352214605,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352214607,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-promptsubmit-block/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-promptsubmit-block/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"hook/invoked","seq":1,"time":0,"data":{"turn":1,"point":"UserPromptSubmit","dialect":"codex","handlerId":"codex:UserPromptSubmit:1"}}
 {"type":"hook/result","seq":2,"time":0,"data":{"turn":1,"point":"UserPromptSubmit","handlerId":"codex:UserPromptSubmit:1","decision":"block","exitCode":2,"stderrSummary":"blocked by codex policy hook","durationMs":0}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-promptsubmit-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-promptsubmit-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"0bebc0f4-a089-4fde-9b6e-db9532cfd4de","createdAt":1783352209682,"cwd":"/tmp/acp-snap-cwd-aopaZV"}
+{"type":"session","version":0,"id":"0bebc0f4-a089-4fde-9b6e-db9532cfd4de","createdAt":1783352209682,"cwd":"/tmp/acp-snap-cwd-aopaZV","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352209686,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"hook/invoked","seq":1,"time":1783352209687,"data":{"turn":1,"point":"UserPromptSubmit","dialect":"codex","handlerId":"codex:UserPromptSubmit:1"}}
 {"type":"hook/result","seq":2,"time":1783352209706,"data":{"turn":1,"point":"UserPromptSubmit","handlerId":"codex:UserPromptSubmit:1","decision":"pass","exitCode":0,"durationMs":19.49695100000008}}
--- a/examples/acp-agent/tests/snapshots/hook-codex-stop-continue/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/hook-codex-stop-continue/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"eb17be12-ca8c-46c8-b500-0977e8400208","createdAt":1784522152392,"cwd":"/var/folders/4j/54c8wb496zxfrs1ny_21jbb00000gn/T/acp-snap-cwd-ESgqLu"}
+{"type":"session","version":0,"id":"eb17be12-ca8c-46c8-b500-0977e8400208","createdAt":1784522152392,"cwd":"/var/folders/4j/54c8wb496zxfrs1ny_21jbb00000gn/T/acp-snap-cwd-ESgqLu","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784522152397,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1784522152397,"data":{"content":[{"type":"text","text":"Reply with the single word FIRST and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1784522152399,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/model-switching/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/model-switching/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"622d16ce-0a94-476b-97a4-26dad50b1fbf","createdAt":1784086275585,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-Cwf7Bh"}
+{"type":"session","version":0,"id":"622d16ce-0a94-476b-97a4-26dad50b1fbf","createdAt":1784086275585,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-Cwf7Bh","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1784086275588,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1784086275588,"data":{"content":[{"type":"text","text":"Without using tools, reply with exactly FLASH and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1784086275590,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/multi-turn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/multi-turn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"228b7b82-84ed-49b7-a567-981c03b28c77","createdAt":1783352113760,"cwd":"/tmp/acp-snap-cwd-aN2GRR"}
+{"type":"session","version":0,"id":"228b7b82-84ed-49b7-a567-981c03b28c77","createdAt":1783352113760,"cwd":"/tmp/acp-snap-cwd-aN2GRR","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352113765,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352113765,"data":{"content":[{"type":"text","text":"Reply with exactly the word: ONE. No tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352113767,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/parallel-tool-calls/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/parallel-tool-calls/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":0,"data":{"content":[{"type":"text","text":"Use the read tool twice in the same assistant message: read a.txt and b.txt. Then reply DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":0,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/permission-switching/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/permission-switching/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"df041acb-2f14-4d5f-b6e2-2fb6b9eb6427","createdAt":1783860666204,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-4oJKT4"}
+{"type":"session","version":0,"id":"df041acb-2f14-4d5f-b6e2-2fb6b9eb6427","createdAt":1783860666204,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-4oJKT4","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783860666206,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"permission/preset","seq":1,"time":1783962244578,"data":{"preset":"workspace-write"}}
 {"type":"sandbox/mode","seq":2,"time":1784518115721,"data":{"mode":"workspace-write"}}
--- a/examples/acp-agent/tests/snapshots/reject-extra-dirs/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/reject-extra-dirs/session.jsonl
@@ -1 +1 @@
-{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0}
+{"type":"session","version":0,"id":"00000000-0000-0000-0000-000000000000","createdAt":0,"delegationDepth":0}
--- a/examples/acp-agent/tests/snapshots/repeat-tool-guard/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/repeat-tool-guard/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":0,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":0,"data":{"content":[{"type":"text","text":"Write the todo list 'watch the kettle boil' five times in a row without changing it, then reply DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":0,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/skill-load/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/skill-load/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"9eb4181f-2d05-49d3-98fc-3711fe2f5664","createdAt":1783654655599,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-DhYwNW"}
+{"type":"session","version":0,"id":"9eb4181f-2d05-49d3-98fc-3711fe2f5664","createdAt":1783654655599,"cwd":"/var/folders/_g/59jgff8x2gqd39f5vy1wnbfc0000gn/T/acp-snap-cwd-DhYwNW","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783654655602,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783654655603,"data":{"content":[{"type":"text","text":"Load the snapshot-skill skill with the skill tool, then reply DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783654655608,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/input.json
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/input.json
@@ -0,0 +1,7 @@
+{
+  "steps": [
+    { "op": "initialize" },
+    { "op": "newSession" },
+    { "op": "prompt", "text": "Delegate through two child generations. The depth-two child must attempt one more subagent call and report the rejection." }
+  ]
+}
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/replay.override.json
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/replay.override.json
@@ -0,0 +1,22 @@
+[
+  {
+    "kind": "chunks",
+    "chunks": [
+      { "type": "block-start", "index": 0, "blockType": "tool-call" },
+      { "type": "tool-call-delta", "index": 0, "id": "call_root_child", "name": "subagent", "argumentsDelta": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}" },
+      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "call_root_child", "name": "subagent", "arguments": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}" } },
+      { "type": "usage", "usage": { "inputTokens": 10, "outputTokens": 5 } },
+      { "type": "finish", "reason": { "kind": "tool-calls" } }
+    ]
+  },
+  {
+    "kind": "chunks",
+    "chunks": [
+      { "type": "block-start", "index": 0, "blockType": "text" },
+      { "type": "text-delta", "index": 0, "text": "ROOT_DONE" },
+      { "type": "block-end", "index": 0, "block": { "type": "text", "text": "ROOT_DONE" } },
+      { "type": "usage", "usage": { "inputTokens": 10, "outputTokens": 2 } },
+      { "type": "finish", "reason": { "kind": "stop" } }
+    ]
+  }
+]
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.1.jsonl
@@ -0,0 +1,23 @@
+{"type":"session","version":0,"id":"22222222-2222-4222-8222-222222222222","createdAt":1001,"cwd":"/tmp/subagent-depth-two","parentSession":"11111111-1111-4111-8111-111111111111","delegationDepth":1}
+{"type":"turn/start","seq":0,"time":1784540790312,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
+{"type":"user/message","seq":1,"time":1784540790312,"data":{"content":[{"type":"text","text":"Call subagent once. Ask that child to attempt one further subagent call, then report the result."}],"source":{"kind":"user"}},"surfaceOp":"append"}
+{"type":"step/start","seq":2,"time":1784540790318,"data":{"turn":1,"step":1}}
+{"type":"request/header","seq":3,"time":1784540790318,"data":{"header":{"config":{"provider":"deepseek","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
+{"type":"assistant/chunk","seq":4,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
+{"type":"assistant/chunk","seq":5,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_one_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}}
+{"type":"assistant/chunk","seq":6,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}}}
+{"type":"assistant/chunk","seq":7,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
+{"type":"assistant/chunk","seq":8,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
+{"type":"assistant/message","seq":9,"time":1784540790318,"data":{"turn":1,"step":1,"content":[{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[4,5,6,7,8],"surfaceOp":"append"}
+{"type":"tool/call","seq":10,"time":1784540790319,"data":{"turn":1,"step":1,"callId":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}
+{"type":"tool/result","seq":11,"time":1784540790362,"data":{"turn":1,"step":1,"callId":"call_depth_one_child","content":[{"type":"text","text":"DEPTH_REJECTED"}],"isError":false},"sourceEventSeqs":[10],"surfaceOp":"append"}
+{"type":"step/end","seq":12,"time":1784540790363,"data":{"turn":1,"step":1}}
+{"type":"step/start","seq":13,"time":1784540790364,"data":{"turn":1,"step":2}}
+{"type":"assistant/chunk","seq":14,"time":1784540790365,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
+{"type":"assistant/chunk","seq":15,"time":1784540790365,"data":{"turn":1,"step":2,"chunk":{"type":"text-delta","index":0,"text":"DEPTH_ONE_DONE"}}}
+{"type":"assistant/chunk","seq":16,"time":1784540790365,"data":{"turn":1,"step":2,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"DEPTH_ONE_DONE"}}}}
+{"type":"assistant/chunk","seq":17,"time":1784540790365,"data":{"turn":1,"step":2,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":2}}}}
+{"type":"assistant/chunk","seq":18,"time":1784540790365,"data":{"turn":1,"step":2,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
+{"type":"assistant/message","seq":19,"time":1784540790365,"data":{"turn":1,"step":2,"content":[{"type":"text","text":"DEPTH_ONE_DONE"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":2}},"sourceEventSeqs":[14,15,16,17,18],"surfaceOp":"append"}
+{"type":"step/end","seq":20,"time":1784540790365,"data":{"turn":1,"step":2}}
+{"type":"turn/end","seq":21,"time":1784540790365,"data":{"turn":1,"reason":{"kind":"completed"}}}
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.2.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.2.jsonl
@@ -0,0 +1,23 @@
+{"type":"session","version":0,"id":"33333333-3333-4333-8333-333333333333","createdAt":1002,"cwd":"/tmp/subagent-depth-two","parentSession":"22222222-2222-4222-8222-222222222222","delegationDepth":2}
+{"type":"turn/start","seq":0,"time":1784540790319,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
+{"type":"user/message","seq":1,"time":1784540790319,"data":{"content":[{"type":"text","text":"Attempt one subagent call beyond the configured cap, then report the rejection."}],"source":{"kind":"user"}},"surfaceOp":"append"}
+{"type":"step/start","seq":2,"time":1784540790334,"data":{"turn":1,"step":1}}
+{"type":"request/header","seq":3,"time":1784540790334,"data":{"header":{"config":{"provider":"deepseek","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
+{"type":"assistant/chunk","seq":4,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
+{"type":"assistant/chunk","seq":5,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_three_rejected","name":"subagent","argumentsDelta":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}}
+{"type":"assistant/chunk","seq":6,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}}}
+{"type":"assistant/chunk","seq":7,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
+{"type":"assistant/chunk","seq":8,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
+{"type":"assistant/message","seq":9,"time":1784540790335,"data":{"turn":1,"step":1,"content":[{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[4,5,6,7,8],"surfaceOp":"append"}
+{"type":"tool/call","seq":10,"time":1784540790335,"data":{"turn":1,"step":1,"callId":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}
+{"type":"tool/result","seq":11,"time":1784540790337,"data":{"turn":1,"step":1,"callId":"call_depth_three_rejected","content":[{"type":"text","text":"Error: subagent depth 3 exceeds maxDepth 2"}],"isError":true},"sourceEventSeqs":[10],"surfaceOp":"append"}
+{"type":"step/end","seq":12,"time":1784540790338,"data":{"turn":1,"step":1}}
+{"type":"step/start","seq":13,"time":1784540790338,"data":{"turn":1,"step":2}}
+{"type":"assistant/chunk","seq":14,"time":1784540790339,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
+{"type":"assistant/chunk","seq":15,"time":1784540790339,"data":{"turn":1,"step":2,"chunk":{"type":"text-delta","index":0,"text":"DEPTH_REJECTED"}}}
+{"type":"assistant/chunk","seq":16,"time":1784540790339,"data":{"turn":1,"step":2,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"DEPTH_REJECTED"}}}}
+{"type":"assistant/chunk","seq":17,"time":1784540790339,"data":{"turn":1,"step":2,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":2}}}}
+{"type":"assistant/chunk","seq":18,"time":1784540790339,"data":{"turn":1,"step":2,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
+{"type":"assistant/message","seq":19,"time":1784540790339,"data":{"turn":1,"step":2,"content":[{"type":"text","text":"DEPTH_REJECTED"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":2}},"sourceEventSeqs":[14,15,16,17,18],"surfaceOp":"append"}
+{"type":"step/end","seq":20,"time":1784540790339,"data":{"turn":1,"step":2}}
+{"type":"turn/end","seq":21,"time":1784540790339,"data":{"turn":1,"reason":{"kind":"completed"}}}
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.jsonl
@@ -0,0 +1,23 @@
+{"type":"session","version":0,"id":"11111111-1111-4111-8111-111111111111","createdAt":1000,"cwd":"/tmp/subagent-depth-two","delegationDepth":0}
+{"type":"turn/start","seq":0,"time":1784540790290,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
+{"type":"user/message","seq":1,"time":1784540790291,"data":{"content":[{"type":"text","text":"Delegate through two child generations. The depth-two child must attempt one more subagent call and report the rejection."}],"source":{"kind":"user"}},"surfaceOp":"append"}
+{"type":"step/start","seq":2,"time":1784540790308,"data":{"turn":1,"step":1}}
+{"type":"request/header","seq":3,"time":1784540790308,"data":{"header":{"config":{"provider":"deepseek","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
+{"type":"assistant/chunk","seq":4,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
+{"type":"assistant/chunk","seq":5,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_root_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}}
+{"type":"assistant/chunk","seq":6,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}}}
+{"type":"assistant/chunk","seq":7,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
+{"type":"assistant/chunk","seq":8,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
+{"type":"assistant/message","seq":9,"time":1784540790310,"data":{"turn":1,"step":1,"content":[{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[4,5,6,7,8],"surfaceOp":"append"}
+{"type":"tool/call","seq":10,"time":1784540790310,"data":{"turn":1,"step":1,"callId":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}
+{"type":"tool/result","seq":11,"time":1784540790381,"data":{"turn":1,"step":1,"callId":"call_root_child","content":[{"type":"text","text":"DEPTH_ONE_DONE"}],"isError":false},"sourceEventSeqs":[10],"surfaceOp":"append"}
+{"type":"step/end","seq":12,"time":1784540790382,"data":{"turn":1,"step":1}}
+{"type":"step/start","seq":13,"time":1784540790382,"data":{"turn":1,"step":2}}
+{"type":"assistant/chunk","seq":14,"time":1784540790383,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
+{"type":"assistant/chunk","seq":15,"time":1784540790383,"data":{"turn":1,"step":2,"chunk":{"type":"text-delta","index":0,"text":"ROOT_DONE"}}}
+{"type":"assistant/chunk","seq":16,"time":1784540790383,"data":{"turn":1,"step":2,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"ROOT_DONE"}}}}
+{"type":"assistant/chunk","seq":17,"time":1784540790383,"data":{"turn":1,"step":2,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":2}}}}
+{"type":"assistant/chunk","seq":18,"time":1784540790383,"data":{"turn":1,"step":2,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
+{"type":"assistant/message","seq":19,"time":1784540790383,"data":{"turn":1,"step":2,"content":[{"type":"text","text":"ROOT_DONE"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":10,"outputTokens":2}},"sourceEventSeqs":[14,15,16,17,18],"surfaceOp":"append"}
+{"type":"step/end","seq":20,"time":1784540790383,"data":{"turn":1,"step":2}}
+{"type":"turn/end","seq":21,"time":1784540790383,"data":{"turn":1,"reason":{"kind":"completed"}}}
--- a/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/stdout.expected.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/stdout.expected.jsonl
@@ -0,0 +1,6 @@
+{"jsonrpc":"2.0","id":1,"result":{"protocolVersion":1,"agentInfo":{"name":"deepseek-harness-acp","version":"0.0.1"},"agentCapabilities":{"loadSession":true,"promptCapabilities":{"image":false,"audio":false,"embeddedContext":false}},"authMethods":[]}}
+{"jsonrpc":"2.0","id":2,"result":{"sessionId":"{{sessionId}}","configOptions":[{"id":"model","name":"Model","description":"Sets this session's provider and model.","category":"model","type":"select","currentValue":"[\"deepseek\",\"deepseek-v4-flash\"]","options":[{"value":"[\"deepseek\",\"deepseek-v4-flash\"]","name":"deepseek-v4-flash"},{"value":"[\"deepseek\",\"deepseek-v4-pro\"]","name":"deepseek-v4-pro"}]},{"id":"permission","name":"Permissions","description":"The session permission preset: each choice bundles a sandbox mode and an approval policy.","category":"mode","type":"select","currentValue":"danger-full-access","options":[{"value":"workspace-write","name":"workspace-write","description":"Write inside the workspace and permitted temporary directories; wider retries require approval."},{"value":"danger-full-access","name":"danger-full-access","description":"Full file access without approval prompts."}]}]}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"tool_call","toolCallId":"call_root_child","title":"subagent","kind":"other","status":"in_progress","rawInput":{"description":"Start depth one","prompt":"Call subagent once. Ask that child to attempt one further subagent call, then report the result."}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"tool_call_update","toolCallId":"call_root_child","status":"completed","content":[{"type":"content","content":{"type":"text","text":"DEPTH_ONE_DONE"}}]}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_message_chunk","content":{"type":"text","text":"ROOT_DONE"}}}}
+{"jsonrpc":"2.0","id":3,"result":{"stopReason":"end_turn"}}
--- a/examples/acp-agent/tests/snapshots/subagent-fork/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-fork/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"ada8966c-9fa3-441b-8721-37ff1e795e6a","createdAt":1783352137161,"cwd":"/tmp/acp-snap-cwd-0HLtcD","parentSession":"96cf59c9-b347-48b9-b234-a5200913ad05","seedLength":37}
+{"type":"session","version":0,"id":"ada8966c-9fa3-441b-8721-37ff1e795e6a","createdAt":1783352137161,"cwd":"/tmp/acp-snap-cwd-0HLtcD","parentSession":"96cf59c9-b347-48b9-b234-a5200913ad05","seedLength":37,"delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352134837,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352134838,"data":{"content":[{"type":"text","text":"Remember this fact for later: the project codeword is MARMALADE. Reply with the single word OK and stop. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352134840,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-fork/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-fork/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"96cf59c9-b347-48b9-b234-a5200913ad05","createdAt":1783352134832,"cwd":"/tmp/acp-snap-cwd-0HLtcD"}
+{"type":"session","version":0,"id":"96cf59c9-b347-48b9-b234-a5200913ad05","createdAt":1783352134832,"cwd":"/tmp/acp-snap-cwd-0HLtcD","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352134837,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352134838,"data":{"content":[{"type":"text","text":"Remember this fact for later: the project codeword is MARMALADE. Reply with the single word OK and stop. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352134840,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-mixed/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-mixed/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"e4aafa18-b9e3-48d0-8aae-6c9b25dcae80","createdAt":1783352145223,"cwd":"/tmp/acp-snap-cwd-i43JSF","parentSession":"959ffdf5-03e2-465e-9482-009b704632dc"}
+{"type":"session","version":0,"id":"e4aafa18-b9e3-48d0-8aae-6c9b25dcae80","createdAt":1783352145223,"cwd":"/tmp/acp-snap-cwd-i43JSF","parentSession":"959ffdf5-03e2-465e-9482-009b704632dc","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352145224,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352145224,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352145224,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-mixed/session.2.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-mixed/session.2.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"02b3a8dd-1d5e-4866-825f-5fbf5000a632","createdAt":1783352147504,"cwd":"/tmp/acp-snap-cwd-i43JSF","parentSession":"959ffdf5-03e2-465e-9482-009b704632dc","seedLength":31}
+{"type":"session","version":0,"id":"02b3a8dd-1d5e-4866-825f-5fbf5000a632","createdAt":1783352147504,"cwd":"/tmp/acp-snap-cwd-i43JSF","parentSession":"959ffdf5-03e2-465e-9482-009b704632dc","seedLength":31,"delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352142834,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352142834,"data":{"content":[{"type":"text","text":"Remember this fact for later: the project codeword is SAFFRON. Reply with the single word OK and stop. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352142835,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-mixed/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-mixed/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"959ffdf5-03e2-465e-9482-009b704632dc","createdAt":1783352142830,"cwd":"/tmp/acp-snap-cwd-i43JSF"}
+{"type":"session","version":0,"id":"959ffdf5-03e2-465e-9482-009b704632dc","createdAt":1783352142830,"cwd":"/tmp/acp-snap-cwd-i43JSF","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352142834,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352142834,"data":{"content":[{"type":"text","text":"Remember this fact for later: the project codeword is SAFFRON. Reply with the single word OK and stop. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352142835,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-multi/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-multi/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"553f8e92-aac1-4df3-8657-eacbb58f9581","createdAt":1783352127669,"cwd":"/tmp/acp-snap-cwd-28z5Of","parentSession":"14dda109-5728-45ba-a002-7db9543fe50e"}
+{"type":"session","version":0,"id":"553f8e92-aac1-4df3-8657-eacbb58f9581","createdAt":1783352127669,"cwd":"/tmp/acp-snap-cwd-28z5Of","parentSession":"14dda109-5728-45ba-a002-7db9543fe50e","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352127670,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352127670,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352127671,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-multi/session.2.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-multi/session.2.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"5f49e80c-16fc-42c7-a617-0b6bd0680aa3","createdAt":1783352129662,"cwd":"/tmp/acp-snap-cwd-28z5Of","parentSession":"14dda109-5728-45ba-a002-7db9543fe50e"}
+{"type":"session","version":0,"id":"5f49e80c-16fc-42c7-a617-0b6bd0680aa3","createdAt":1783352129662,"cwd":"/tmp/acp-snap-cwd-28z5Of","parentSession":"14dda109-5728-45ba-a002-7db9543fe50e","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352129662,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352129662,"data":{"content":[{"type":"text","text":"Reply with exactly the word BETA and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352129663,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-multi/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-multi/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"14dda109-5728-45ba-a002-7db9543fe50e","createdAt":1783352126247,"cwd":"/tmp/acp-snap-cwd-28z5Of"}
+{"type":"session","version":0,"id":"14dda109-5728-45ba-a002-7db9543fe50e","createdAt":1783352126247,"cwd":"/tmp/acp-snap-cwd-28z5Of","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352126251,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352126251,"data":{"content":[{"type":"text","text":"Use the subagent tool TWICE, once at a time, to delegate two subtasks to child agents. First subtask: 'Reply with exactly the word ALPHA and nothing else.' Second subtask (after the first returns): 'Reply with exactly the word BETA and nothing else.' After both subagents return, reply with the single word PARENT_DONE and stop. Do not use the bash tool."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352126252,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-spawn/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-spawn/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"ea339828-7885-42e1-9083-4355e6f1708d","createdAt":1783352120855,"cwd":"/tmp/acp-snap-cwd-rbeWyt","parentSession":"5138ed0d-e86e-4a7d-b75b-803307e92b17"}
+{"type":"session","version":0,"id":"ea339828-7885-42e1-9083-4355e6f1708d","createdAt":1783352120855,"cwd":"/tmp/acp-snap-cwd-rbeWyt","parentSession":"5138ed0d-e86e-4a7d-b75b-803307e92b17","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783352120856,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352120856,"data":{"content":[{"type":"text","text":"Reply with exactly the word CHILD_OK and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352120856,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/subagent-spawn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/subagent-spawn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"5138ed0d-e86e-4a7d-b75b-803307e92b17","createdAt":1783352119267,"cwd":"/tmp/acp-snap-cwd-rbeWyt"}
+{"type":"session","version":0,"id":"5138ed0d-e86e-4a7d-b75b-803307e92b17","createdAt":1783352119267,"cwd":"/tmp/acp-snap-cwd-rbeWyt","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352119273,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352119274,"data":{"content":[{"type":"text","text":"Use the subagent tool exactly once to delegate this subtask to a child agent: 'Reply with exactly the word CHILD_OK and nothing else.' After the subagent returns, reply with the single word PARENT_DONE and stop. Do not use the bash tool."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352119275,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/text-turn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/text-turn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"539aa64c-7f37-40ff-abd8-ed45b717be1b","createdAt":1783600629539,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-ka5r8w"}
+{"type":"session","version":0,"id":"539aa64c-7f37-40ff-abd8-ed45b717be1b","createdAt":1783600629539,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-ka5r8w","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783600629541,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783600629541,"data":{"content":[{"type":"text","text":"Reply with exactly the word: PONG. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783600629542,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/todo-plan/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/todo-plan/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"b0f1f758-dcf0-474e-851d-e62c11ec0a09","createdAt":1783352057652,"cwd":"/tmp/acp-snap-cwd-AYilT7"}
+{"type":"session","version":0,"id":"b0f1f758-dcf0-474e-851d-e62c11ec0a09","createdAt":1783352057652,"cwd":"/tmp/acp-snap-cwd-AYilT7","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352057655,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352057655,"data":{"content":[{"type":"text","text":"Use the todo_write tool to record a plan with exactly three todos: \"read the code\" (in_progress), \"write the fix\" (pending), \"run the tests\" (pending). Send all three in one todo_write call. Then reply with the single word DONE and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352057657,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/tool-call-turn/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/tool-call-turn/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"e9421ff4-baae-4807-a7ea-fd8a65f2c897","createdAt":1783352044766,"cwd":"/tmp/acp-snap-cwd-OwUkBh"}
+{"type":"session","version":0,"id":"e9421ff4-baae-4807-a7ea-fd8a65f2c897","createdAt":1783352044766,"cwd":"/tmp/acp-snap-cwd-OwUkBh","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352044771,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352044771,"data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo SNAPSHOT_OK. Then reply with the single word DONE and stop."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352044773,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/workflow-run/session.1.jsonl
+++ b/examples/acp-agent/tests/snapshots/workflow-run/session.1.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"583a4db2-3350-436c-b4a5-5615fd159052","createdAt":1783600636316,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-vdJYjz","parentSession":"3fd7d599-56b1-493a-930d-f1fc5e1556e8"}
+{"type":"session","version":0,"id":"583a4db2-3350-436c-b4a5-5615fd159052","createdAt":1783600636316,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-vdJYjz","parentSession":"3fd7d599-56b1-493a-930d-f1fc5e1556e8","delegationDepth":1}
 {"type":"turn/start","seq":0,"time":1783600636316,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783600636316,"data":{"content":[{"type":"text","text":"Reply with exactly the word WF_CHILD_OK and nothing else."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783600636316,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/workflow-run/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/workflow-run/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"3fd7d599-56b1-493a-930d-f1fc5e1556e8","createdAt":1783600631835,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-vdJYjz"}
+{"type":"session","version":0,"id":"3fd7d599-56b1-493a-930d-f1fc5e1556e8","createdAt":1783600631835,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-vdJYjz","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783600631838,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783600631838,"data":{"content":[{"type":"text","text":"Use the workflow tool exactly once, with args omitted, meta set to { \"name\": \"snapshot-flow\", \"description\": \"one child for the snapshot\" }, and this EXACT script body (copy it verbatim):\nphase('Run')\nconst reply = await agent('Reply with exactly the word WF_CHILD_OK and nothing else.')\nreturn { reply }\nAfter the workflow returns, reply with the single word WORKFLOW_DONE and stop. Do not use any other tool."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783600631839,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/workspace-context/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/workspace-context/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}"}
+{"type":"session","version":0,"id":"{{sessionId}}","createdAt":0,"cwd":"{{cwd}}","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783778297065,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783778297066,"data":{"content":[{"type":"text","text":"Read nested/task.txt with the read tool, then reply DONE."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783778297069,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/tests/snapshots/workspace-edit/session.jsonl
+++ b/examples/acp-agent/tests/snapshots/workspace-edit/session.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":0,"id":"48aca674-000a-4583-810b-01f8785cef13","createdAt":1783352264076,"cwd":"/tmp/acp-snap-cwd-rxbEpP"}
+{"type":"session","version":0,"id":"48aca674-000a-4583-810b-01f8785cef13","createdAt":1783352264076,"cwd":"/tmp/acp-snap-cwd-rxbEpP","delegationDepth":0}
 {"type":"turn/start","seq":0,"time":1783352264080,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
 {"type":"user/message","seq":1,"time":1783352264081,"data":{"content":[{"type":"text","text":"A file named greeting.txt in the current directory contains one word. Use the bash tool to append a second line containing the word WORLD to it (so it has two lines), then read the file back with `cat greeting.txt` to confirm, and reply with the single word DONE. Use a single bash call per action."}],"source":{"kind":"user"}},"surfaceOp":"append"}
 {"type":"step/start","seq":2,"time":1783352264082,"data":{"turn":1,"step":1}}
--- a/examples/acp-agent/workspace-context.cordis.snapshot.yml
+++ b/examples/acp-agent/workspace-context.cordis.snapshot.yml
@@ -15,6 +15,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
          workspaceContext:
            maxBytes: 65536
            dshHome: !!js process.cwd() + '/.dsh'
--- a/examples/acp-agent/workspace-context.cordis.yml
+++ b/examples/acp-agent/workspace-context.cordis.yml
@@ -12,6 +12,7 @@
          provider: deepseek
          model: deepseek-v4-flash
          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
          workspaceContext:
            maxBytes: 65536
            dshHome: !!js process.cwd() + '/.dsh'
--- a/examples/echo-agent/README.md
+++ b/examples/echo-agent/README.md
@@ -31,4 +31,4 @@ node --expose-internals --import tsx packages/examples/stdio-demo/src/bin.ts exa

 Type a message and press Enter. "echo <text>" triggers a tool call round-trip (the mock model requests the `echo` tool, which echoes the text uppercased, and the next model step acknowledges it).

-The session is persisted under `.sessions/` relative to the directory you launch the demo from. `pnpm run demo:echo` runs from the repo root, so the logs land in `<repo-root>/.sessions/cwd-<hash>/` (one `.jsonl` log per session). Clean up with: `rm -rf .sessions`
+The session is persisted under `.sessions/` relative to the directory you launch the demo from. `pnpm run demo:echo` runs from the repo root, so the logs land in `<repo-root>/.sessions/cwd-<hash>/` (one `.jsonl.zstd` log per session). Clean up with: `rm -rf .sessions`
--- a/Show More
+++ b/Show More