* feat(sandbox): share sandbox identity derivation and acquire serialization (#4741)
Remote providers (AIO, E2B, BoxLite, Tenki, OpenSandbox) each inlined the
same sha256(user:thread)[:16] sandbox-id expression and kept per-scope lock
dicts that grew unboundedly until shutdown. This extracts both mechanisms
into shared components without changing provider lifecycle, ids, capacity
semantics, or public tool behavior:
- sandbox/identity.py: keyword-only derive_sandbox_scope_token (byte-pinned
compatibility contract) + is_sandbox_scope_token; per-provider golden
vectors pin current behavior including BoxLite's raw-None quirk and each
provider's private user_id resolution.
- sandbox/acquire_serialization.py: AcquireSerializer — per-key lock table
with holder/waiter refcount reclamation, bounded dedicated executor
(async waits off both the event loop and the default executor),
worker-owned cancellation cleanup (no event-loop callback dependency), idempotent close().
- Each provider adopts both components; AIO/E2B key by (user_id, thread_id)
with acquire and (E2B) release serialized; BoxLite/Tenki/OpenSandbox key
by derived sandbox id and offload the whole sync acquire to the
serializer's executor so a cancelled awaiter cannot overlap a retried
same-scope body (leaked-remote-VM regression caught in review).
- thread_id=None acquires stay unserialized; provider shutdown()/reset()
close the serializer; E2B capacity/ledger/reconciliation and AIO
ownership/flock machinery untouched.
- blocking-IO anchor proves contended OpenSandbox acquire_async stays off
the event loop (teeth verified red/green); AGENTS.md documents the
shared components.
* refactor(sandbox): address review on acquire serialization (#5089)
- Replace unreachable checkin branch with an assertion: run() returns
False only after abandon(), which the except handler always re-raises;
the old _checkin would have double-decremented the refcount.
- Document the task.cancelling() == 0 assumption in hold_async.
- Drop unused thread_id/user_id kwargs from BoxLite and Tenki
_acquire_scope_locked (OpenSandbox still forwards them).
* fix(sandbox): preserve request ContextVars in acquire executor bridge (#5089)
loop.run_in_executor() does not copy contextvars, unlike the inherited
SandboxProvider.acquire_async() which used asyncio.to_thread(). The
BoxLite/OpenSandbox/Tenki acquire_async bridges introduced in this PR
therefore dropped the request trace id (logged as trace_id=-).
Add AcquireSerializer.run_on_executor(), which copies the calling
context and runs the callable through ctx.run, and route all three
providers through it. Add regression tests binding request_trace_context
and verifying the worker thread observes it.
