diff --git a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.i18n.yaml b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.i18n.yaml
index a636d18288..cf4c994853 100644
--- a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.i18n.yaml
+++ b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.i18n.yaml
@@ -2,5 +2,5 @@
 # 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 .agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md
-2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md: 6213a5d28493c388f7a05d57d353896e0b86f352
-2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md: daf02b895a06039cd06976edb7c10cf9481b7166
+2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md: afdad301a4853754184b75668d167e71420c2480
+2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md: 48d6e0748979b09053aa51a94788fdd95d997179
diff --git a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md
index 6213a5d284..afdad301a4 100644
--- a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md
+++ b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.md
@@ -1,4 +1,4 @@
-# Agent Note: Bound in-flight binding calls, snapshot binding metadata, and compact the reply queue in the CPython backend
+# Agent Note: Bound in-flight binding calls, snapshot binding metadata, compact the reply queue, and meter wide completions with cursors in the CPython backend
 
 Status: implemented
 
@@ -6,13 +6,13 @@ English | [中文](2026-08-29-code-runtime-python-call-backlog-and-binding-metad
 
 ## Problem
 
-A further review round on the CPython subprocess backend (packages/experimental/code-runtime-python) surfaced three findings on the binding-dispatch and validation paths. First, the reply-backlog cap counts only RESOLVED calls — `pendingReplies` grows after the binding's `await` resolves — so a child flooding calls against a binding whose promise never settles accumulates one async closure per frame until the wall clock without ever tripping the cap. Second, `validateBindings` reads `errorClass.name`, `errorClass.memberNameProperty`, and `namespace.global` several times and retains the original errorClass object for the boot frame, whose `JSON.stringify` re-reads it after validation: a getter that returns a valid value during validation and then throws or returns a conflicting value at stringify time turns the seam-misuse rejection into a worker-exit, or injects a different name than validation approved. Third, `replyQueue` never shrinks mid-drain: the drain loop clears consumed slots to `undefined` but leaves `length` (and the backing store) growing, so a child that reads replies just fast enough to keep the drain alive but never empty grows the array linearly with cumulative throughput.
+A further review round on the CPython subprocess backend (packages/experimental/code-runtime-python) surfaced seven findings on the binding-dispatch, validation, completion-metering, and frame-parse paths. First, the reply-backlog cap counts only RESOLVED calls — `pendingReplies` grows after the binding's `await` resolves — so a child flooding calls against a binding whose promise never settles accumulates one async closure per frame until the wall clock without ever tripping the cap. Second, `validateBindings` reads `errorClass.name`, `errorClass.memberNameProperty`, and `namespace.global` several times and retains the original errorClass object for the boot frame, whose `JSON.stringify` re-reads it after validation: a getter that returns a valid value during validation and then throws or returns a conflicting value at stringify time turns the seam-misuse rejection into a worker-exit, or injects a different name than validation approved. Third, `replyQueue` never shrinks mid-drain: the drain loop clears consumed slots to `undefined` but leaves `length` (and the backing store) growing, so a child that reads replies just fast enough to keep the drain alive but never empty grows the array linearly with cumulative throughput. Fourth, the completion meter `checkDoneValue` pushes every member of an open container onto an explicit work stack, so a wide completion value near the frame cap (millions of members) copies that many references onto the stack — O(width) auxiliary memory on top of the already-parsed value — OOMing the host after the parse succeeded. Fifth, a done frame processed in the SAME data event as more than 1024 call frames settles the run before the post-macrotask call-backlog check runs (which no-ops once settled), so a child could finish successfully while leaving the outstanding closures behind. Sixth, the child's `_dump_string` folds a spelled-out surrogate pair into its astral code point, so two DIFFERENT Python dict keys — `"\ud83d\ude00"` and `"\U0001f600"` — encode to the SAME JSON member and the host's `JSON.parse` silently drops one of them, violating the lossless-JSON promise for completions and binding arguments. Seventh, the load gate bounds the CHILD's build-and-encode under `RLIMIT_AS` but not the HOST's `JSON.parse`: a legitimately configured wide completion near the frame cap (e.g. a 3-million-key dict under a 50 MiB budget) materializes several times its raw bytes in the host's property storage, so a constrained host heap (e.g. `--max-old-space-size=256`) dies with a process-level OOM during the parse — before `checkDoneValue` (which only sees the already-parsed value) could reject it.
 
 ## Decision
 
-### In-flight binding calls are capped at 1024
+### In-flight binding calls are capped at 1024, checked once per macrotask after the microtasks drain
 
-`case 'call'` counts the outstanding binding calls before dispatch (`pendingCalls`) and releases the slot in the async body's `finally`, covering the reply-written, resolution-rejected, and settled-drop exits. When the count reaches `MAX_PENDING_REPLIES`, the run settles as a `worker-exit` with a call-backlog message, bounding in-flight closures exactly like the reply backlog. This is a count bound, not a byte bound.
+`case 'call'` counts the outstanding binding calls before dispatch (`pendingCalls`) and releases the slot in the async body's `finally`, covering the reply-written, resolution-rejected, and settled-drop exits. The data handler schedules ONE post-batch check per macrotask via `setImmediate` (deduped by a flag): it runs after the current macrotask's microtasks, so it sees the TRUE outstanding count — the live count is inflated by the batch's own frames (the finallys have not run yet), and a per-event snapshot is stale when flowing mode fires several `data` events within one macrotask before any microtask drains. When the count passes `MAX_PENDING_REPLIES` — strictly greater, so exactly 1024 outstanding calls are allowed — the run settles as a `worker-exit` with a call-backlog message. The check no-ops once `settled`, so a `done` or `log` frame wins over the cap: a program that returns with binding calls it started but never awaited still completes with its value. The `done` handler independently re-checks the count before accepting the frame, closing the window where a done in the SAME batch as a flood would settle the run before the post-macrotask check could fire. This is a count bound, not a byte bound.
 
 ### Binding metadata is snapshotted into plain values before validation and the boot frame
 
@@ -22,20 +22,49 @@ A further review round on the CPython subprocess backend (packages/experimental/
 
 `drainReplies` compacts the consumed prefix (`replyQueue.splice(0, head); head = 0`) once `head` reaches `MAX_PENDING_REPLIES`. The splice is O(head) once per bound of consumed frames — amortized O(1) per reply — bounding the backing store to O(backlog + bound) for a drain that never empties.
 
+### The completion meter walks wide values with one cursor per nesting level
+
+`checkDoneValue` now holds one cursor per OPEN container (a values iterator for the root and arrays, an entries iterator for objects whose key escapes are metered when the entry is reached), the same shape `hasNonLosslessNumber` and the child's `_check_done_value` already use. The byte budget still bounds the walk: each member is metered as its cursor yields it, and the width lower-bound checks bail an over-budget container before the cursor descends. The auxiliary state is O(depth), not O(width), so a wide completion near the frame cap meters exactly instead of copying millions of references. `encodeJsonPlain` keeps its per-container task stack, which is O(width) but holds only references while the encoded output is itself O(total bytes) — same-order as its result, so the exemption is documented in its comment.
+
+### The frame parse cap is bounded by the host's heap
+
+The raw-byte frame cap does not protect the host process: `JSON.parse` of a wide-object frame materializes several times the raw bytes in property storage. The WORST shape is a dict of many short unique keys, which forces V8's dictionary-mode property storage plus one interned string per key — measured 6.4x for a 3,000,000-key frame (~31 MB raw) on a 1 GiB heap, trending up with key count (a flat unique-key array is ~4x, a repeated-key dict ~3x); a 256 MiB heap OOMs on that frame outright. The effective cap each instance enforces is `min(protocol cap, floor((heap_size_limit - HOST_PARSE_BASELINE_BYTES) / HOST_PARSE_WORST_CASE_MULTIPLE))` with a 16x multiple — ~2.5x over the measured worst shape — derived from the host's configured heap limit (`--max-old-space-size` honored via `v8.getHeapStatistics().heap_size_limit`). A default Node heap (~4 GiB) never binds; a constrained host lowers the cap and the load gate rejects any budget whose frame could not be parsed safely, failing loud at load instead of OOMing the host mid-parse. The child's `RLIMIT_AS` gate is a separate resource and stays unchanged.
+
+### Dict keys that fold to one JSON member are rejected as non-lossless
+
+The child's `_dump_string` folds a spelled-out surrogate pair into its astral code point so the host's UTF-16 strings (where the two code units and the single character are the SAME string) meter at the same cost. Python can hold both spellings as distinct keys, so a dict containing `"\ud83d\ude00"` and `"\U0001f600"` would emit two members with the same JSON key and the host's `JSON.parse` would silently drop one. Both lossless-JSON walks (`_lossless_json_violation` for binding arguments, `_check_done_value` for completions) now track each dict's combined keys in a per-dict seen-set — O(keys), the same order as the dict itself — and reject a collision as non-lossless before any encoding.
+
 ## Testing
 
 - `tests/runtime.spec.ts` — a hostile child floods 5000 sequential calls against a binding that never settles (`await new Promise(() => {})`); the run settles as `worker-exit` with the call-backlog message long before `maxWallMs`. Verified fail-before: without the cap the run times out at the wall clock.
+- `tests/runtime.spec.ts` — a legitimate `asyncio.gather` of 1025 instant calls completes with all 1025 results: the post-macrotask check sees the count after the finallys drained, where a per-frame check could trip on the 1025th frame of a single 64 KiB read.
+- `tests/runtime.spec.ts` — a program that schedules 1024 slow bindings (still pending) and returns `"done"` completes with its value: the check no-ops once the done frame settles the run, and the strict threshold allows exactly 1024 outstanding calls. Verified fail-before: an unconditional event-boundary check failed this exact case.
+- `tests/runtime.spec.ts` — a single 62 KiB write of 1025 compact calls against a never-settling binding settles as `worker-exit` long before `maxWallMs`, even though no further frames ever arrive: the per-macrotask check fires after the batch. Verified fail-before: a per-event admission snapshot never re-checks without further frames and the run waited out the wall clock.
+- `tests/runtime.spec.ts` — a single write of 1025 compact calls PLUS a done frame in the same batch settles as `worker-exit`: the done handler re-checks the count before accepting the frame, where the post-macrotask check would no-op after the done settled the run. Verified fail-before: without the done re-check the run completed successfully with the outstanding closures left behind.
+- `tests/runtime.spec.ts` — a burst of 1300 instant calls whose frames split across pipe reads completes with all results: the check runs after all of a macrotask's finallys, where a per-event snapshot could see a stale in-flight count when flowing mode fires several events before any microtask drains.
+- `tests/runtime.spec.ts` — a completion value and binding arguments whose dict contains both `"\ud83d\ude00"` and `"\U0001f600"` as keys are rejected as non-lossless (invalid-output / a lossless-JSON call rejection): the two spellings fold to one JSON member, which the host's JSON.parse would silently collapse. Verified fail-before: without the collision check both round-tripped with one key dropped.
+- `tests/protocol.spec.ts` — `hostFrameParseCeiling` derives the effective parse cap from a simulated heap: the protocol cap binds on a default heap, a ~304 MiB host limit yields a 15 MiB cap, and a tiny heap leaves almost no parse room.
+- `tests/runtime.spec.ts` — a child node with a 128 MiB old space rejects a 50 MiB completion budget at load (`maxValueBytes must not exceed`), where the address-space gate alone would admit it. Verified fail-before: with the heap bound ignored the budget loaded.
+- `tests/runtime.spec.ts` — a child node with a 128 MiB old space builds a wide-unique-key dict whose frame is AT the derived cap and parses it, surviving. Verified fail-before: with the parse multiple at 8 the derived cap doubles and the same subprocess OOMs during the parse.
+- The suite's temp fixtures (`dsh-bad-bin-`, `dsh-fake-bin-`, `dsh-rlimit-*`, `dsh-staging-`, heartbeat dirs, wrapper scripts) are now registered and removed after each test, so repeated runs do not accumulate `dsh-*` artifacts in the shared tmpdir.
 - Two namespace-shape tests — `errorClass.name`/`errorClass.memberNameProperty` and `namespace.global` exposed through getters that throw or change on a second read; the run boots and completes, and each field is read exactly once (asserted). Verified fail-before: without the snapshot, the errorClass getter threw inside validation and the global getter injected a different name, failing the program with `NameError`.
-- `tests/runtime.spec.ts` — a child floods calls whose replies exceed the writable high-water mark, blocking the first drain write; the resumed drain consumes a backlog past the compaction bound while a second wave of calls is still pending, and the child reads fd 3 itself (blocking the reply pump) to verify all 1524 replies arrive. Verified fail-before: a splice that removed pending frames dropped the second wave and the run hung to the wall clock.
+- `tests/runtime.spec.ts` — a child floods calls whose replies exceed the writable high-water mark, blocking the first drain write; the resumed drain consumes a backlog past the compaction bound while a second wave of calls is still pending, and the child reads fd 3 itself (blocking the reply pump) to verify all 1524 replies arrive. No fixed sleep: the child's reads pace at the drain's delivery rate, and the host finishes pushing a wave within milliseconds, so the queue is always full at the splice; newlines are counted per chunk (each reply carries exactly one), never by re-scanning the accumulated total, which would be O(n²). Verified fail-before: a splice that removed pending frames dropped the second wave and the run hung to the wall clock.
+- `tests/protocol.spec.ts` — a 2,000,000-element array and a 100,000-key object meter at their exact serialized size, reject one byte under, and still find a `-0` tail element, pinning the cursor walk's breadth behavior.
 
 ## Alternatives considered
 
 **Pause the fd-3 read side instead of counting in-flight calls.** Rejected: pausing reads would also stall processing of `done` and `log` frames the child may send after its last call, changing settlement timing; a count cap is deterministic and matches the existing frame-cap pattern.
 
+**Check the in-flight count per frame.** Rejected: the finallys run on the microtask queue, which drains only when the macrotask ends, so a single event carrying more than `MAX_PENDING_REPLIES` legitimate call frames would trip a per-frame check even though every binding settled immediately.
+
+**Check the count at call admission against a per-event snapshot.** Rejected twice: an unconditional event-boundary check reclassifies a `done` frame as worker-exit when a program returns with calls it never awaited, and a snapshot that refreshes per `data` event is stale when flowing mode fires several events within one macrotask (a legitimate burst whose second chunk carries more in-flight calls than the cap would be killed). Checking the true count once per macrotask, after the microtasks drain, is chunking-independent on both axes, and the strict threshold lets exactly `MAX_PENDING_REPLIES` outstanding calls complete normally.
+
 **Read metadata once but keep the original errorClass object.** Rejected: the boot frame's `JSON.stringify` re-invokes the getters; only a plain stored copy guarantees both stages read the same values.
 
 **Rely on the drain's `finally` reset for queue memory.** Rejected: the reset runs only when the drain ends; a drain that never empties keeps growing. Mid-drain compaction bounds the backing store while the drain is alive.
 
+**Keep the completion meter's explicit member stack.** Rejected: the byte budget bounds the WALK but not the stack's reference count, which is O(width) — a wide value near the frame cap copies millions of references and can OOM the host after the parse succeeded; the per-level cursor shape keeps O(depth) state.
+
 ## Consequences
 
-In-flight binding closures are bounded like the reply backlog, so a child flooding calls against a never-settling binding fails the run early instead of accumulating closures until the wall clock. The boot frame serializes exactly the metadata validation approved, regardless of getter state. The reply queue's backing store stays bounded during sustained partial drains; the compaction is internal memory hygiene with no observable behavior change.
+In-flight binding closures are bounded like the reply backlog, so a child flooding calls against a never-settling binding fails the run early instead of accumulating closures until the wall clock, while a legitimate large concurrent gather is unaffected (the cap is checked after the microtask queue drains). The boot frame serializes exactly the metadata validation approved, regardless of getter state. The reply queue's backing store stays bounded during sustained partial drains; the compaction is internal memory hygiene with no observable behavior change. The completion meter keeps its exact byte accounting with O(depth) auxiliary state, so a wide completion value meters without a host OOM.
diff --git a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md
index daf02b895a..48d6e07489 100644
--- a/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md
+++ b/.agents/notes/implemented/bug-fix/2026-08-29-code-runtime-python-call-backlog-and-binding-metadata-snapshot.zh.md
@@ -1,4 +1,4 @@
-# Agent Note: 在 CPython 后端限制在途 binding 调用、快照 binding 元数据并压缩回复队列
+# Agent Note: 在 CPython 后端限制在途 binding 调用、快照 binding 元数据、压缩回复队列并用游标计量宽完成值
 
 Status: implemented
 
@@ -6,13 +6,13 @@ Status: implemented
 
 ## Problem
 
-对 CPython 子进程后端（packages/experimental/code-runtime-python）的又一轮评审在 binding 分发与校验路径上浮出三项发现。其一，回复积压上限只计数已解析的调用——`pendingReplies` 在 binding 的 `await` 解析后才增长——因此向 promise 永不结算的 binding 洪泛调用的子进程会每个帧累积一个异步闭包直到墙钟，却始终不触发该上限。其二，`validateBindings` 多次读取 `errorClass.name`、`errorClass.memberNameProperty` 与 `namespace.global`，并把原始 errorClass 对象保留到引导帧，其 `JSON.stringify` 在校验后重读该对象：getter 在校验时返回合法值、在序列化时抛错或返回冲突值，会把 seam 误用拒绝变成 worker-exit，或注入一个未经校验批准的名字。其三，`replyQueue` 在排空进行中从不收缩：排空循环把已消费槽位清成 `undefined`，但 `length`（及其后备存储）继续增长，因此以恰好能让排空持续存活却永不排空的速率读取回复的子进程，会让数组随累计吞吐量线性增长。
+对 CPython 子进程后端（packages/experimental/code-runtime-python）的又一轮评审在 binding 分发、校验、完成值计量与帧解析路径上浮出七项发现。其一，回复积压上限只计数已解析的调用——`pendingReplies` 在 binding 的 `await` 解析后才增长——因此向 promise 永不结算的 binding 洪泛调用的子进程会每个帧累积一个异步闭包直到墙钟，却始终不触发该上限。其二，`validateBindings` 多次读取 `errorClass.name`、`errorClass.memberNameProperty` 与 `namespace.global`，并把原始 errorClass 对象保留到引导帧，其 `JSON.stringify` 在校验后重读该对象：getter 在校验时返回合法值、在序列化时抛错或返回冲突值，会把 seam 误用拒绝变成 worker-exit，或注入一个未经校验批准的名字。其三，`replyQueue` 在排空进行中从不收缩：排空循环把已消费槽位清成 `undefined`，但 `length`（及其后备存储）继续增长，因此以恰好能让排空持续存活却永不排空的速率读取回复的子进程，会让数组随累计吞吐量线性增长。其四，完成值计量器 `checkDoneValue` 把开放容器的每个成员压入显式工作栈，因此接近帧上限的宽完成值（数百万成员）会把同等数量的引用复制进栈——在已解析值之上再占 O(width) 辅助内存——在解析成功后 OOM 终止宿主。其五，与超过 1024 个调用帧处于同一 data 事件的 done 帧会在批后调用积压检查运行之前结算运行（该检查在 settled 后为空操作），因此子进程可以「成功」完成却留下未结算闭包。其六，子端 `_dump_string` 把拼写出来的代理项对折叠成星面码点，因此两个不同的 Python 字典键——`"\ud83d\ude00"` 与 `"\U0001f600"`——编码成同一个 JSON 成员，宿主的 `JSON.parse` 会静默丢弃其一，违反完成值与 binding 参数的 lossless JSON 承诺。其七，加载门限制的是子端在 `RLIMIT_AS` 下的构建与编码，而非宿主的 `JSON.parse`：合法配置的接近帧上限宽完成值（如 50 MiB 预算下的 300 万键字典）会在宿主属性存储中物化其原始字节的若干倍，因此受限堆宿主（如 `--max-old-space-size=256`）会在解析期间以进程级 OOM 死亡——早于 `checkDoneValue`（它只能看到已解析值）拒绝它。
 
 ## Decision
 
-### 在途 binding 调用限制为 1024
+### 在途 binding 调用限制为 1024，每个宏任务在微任务排空后检查一次
 
-`case 'call'` 在分发前对在途 binding 调用计数（`pendingCalls`），并在异步体的 `finally` 中释放槽位，覆盖回复已写入、解析被拒绝与结算后丢弃三种出口。计数达到 `MAX_PENDING_REPLIES` 时，运行以带 call-backlog 消息的 `worker-exit` 结算，与回复积压一样限制在途闭包。这是计数上限而非字节上限。
+`case 'call'` 在分发前对在途 binding 调用计数（`pendingCalls`），并在异步体的 `finally` 中释放槽位，覆盖回复已写入、解析被拒绝与结算后丢弃三种出口。data 处理器经 `setImmediate`（用标志去重）为每个宏任务调度一次批后检查：它在该宏任务的微任务之后运行，因此看到的是真实在途计数——实时计数被本批自身帧抬高（`finally` 尚未运行），而按 `data` 事件刷新的快照在 flowing 模式下同一宏任务内连续发出多个事件（微任务尚未排空）时会过期。计数**严格大于** `MAX_PENDING_REPLIES`（恰好 1024 个在途调用允许）时，运行以带 call-backlog 消息的 `worker-exit` 结算。检查在 `settled` 后为空操作，因此 `done` 或 `log` 帧优先于上限：启动了 binding 调用却未 await 就返回的程序仍以其值正常完成。`done` 处理器在接受帧之前独立复查计数，封住与洪泛同批的 done 会在批后检查触发前结算运行的窗口。这是计数上限而非字节上限。
 
 ### binding 元数据在校验与引导帧之前快照为纯值
 
@@ -22,20 +22,49 @@ Status: implemented
 
 `drainReplies` 在 `head` 达到 `MAX_PENDING_REPLIES` 时压缩已消费前缀（`replyQueue.splice(0, head); head = 0`）。该 splice 为 O(head)，每消费一上限的帧执行一次——均摊到每条回复为 O(1)——使永不排空的排空把后备存储限制在 O(积压 + 上限)。
 
+### 完成值计量器每层持一个游标遍历宽值
+
+`checkDoneValue` 现在为每个开放容器持一个游标（根与数组用 values 迭代器，对象用 entries 迭代器——key 的转义字节在该 entry 到达时计量），与 `hasNonLosslessNumber` 及子端 `_check_done_value` 已用的形态一致。字节预算仍然限制遍历：每个成员在游标产出时计量，宽度下界检查会在游标下降之前拒绝超预算容器。辅助状态为 O(depth) 而非 O(width)，因此接近帧上限的宽完成值精确计量，而不是复制数百万引用。`encodeJsonPlain` 保留其每容器任务栈——该栈为 O(width) 但只持有引用，而编码输出本身即 O(total bytes)，与结果同量级，豁免已在注释中说明。
+
+### 帧解析上限受宿主堆约束
+
+原始字节帧上限并不保护宿主进程：`JSON.parse` 一个宽对象帧会在属性存储中物化其原始字节的若干倍。**最坏形态是大量短唯一键的字典**——迫使 V8 进入字典模式属性存储并为每个键内化一个字符串——1 GiB 堆上 3,000,000 键帧（约 31 MB 原始）实测 6.4 倍且随键数上升（平铺唯一键数组约 4 倍、重复键字典约 3 倍）；256 MiB 堆直接在该帧上 OOM。每个实例执行的有效上限为 `min(协议上限, floor((heap_size_limit - HOST_PARSE_BASELINE_BYTES) / HOST_PARSE_WORST_CASE_MULTIPLE))`，系数为 16——实测最坏形态的约 2.5 倍安全余量——由宿主配置的堆上限推导（`--max-old-space-size` 经 `v8.getHeapStatistics().heap_size_limit` 生效）。默认 Node 堆（约 4 GiB）永不收紧；受限宿主会降低上限，加载门拒绝任何帧无法被安全解析的预算，在加载期响亮失败而非在解析中途 OOM 宿主。子端的 `RLIMIT_AS` 门是另一资源，保持不变。
+
+### 折叠为同一 JSON 成员的字典键按非 lossless 拒绝
+
+子端 `_dump_string` 把拼写出来的代理项对折叠成星面码点，使宿主的 UTF-16 字符串（两个码元与单个字符是同一字符串）按相同成本计量。Python 可以把两种拼写作为不同键持有，因此包含 `"\ud83d\ude00"` 与 `"\U0001f600"` 的字典会发出两个同键成员，宿主的 `JSON.parse` 会静默丢弃其一。两条 lossless-JSON 遍历（binding 参数的 `_lossless_json_violation` 与完成值的 `_check_done_value`）现在用每字典 seen 集跟踪合并后的键——O(keys)，与字典本身同量级——在编码前把�