Doc 20 §6 D1, second slice: the dedicated test app D1 calls for, plus
the doc 20 §7 risk-1 gate.
tests/apps/standalone/sched-context/ drives the primitives with no wx
linked (a failure can only be the contexts layer) and assertions ON —
unlike the races harness, an emscripten "cannot start an async
operation" state here IS the bug, not a tolerated state. Nine
scenarios, each pinning one invariant; the load-bearing ones:
- parked_does_not_block: a parked context does not stop others running.
This is doc 19's freeze made unrepresentable — there a parked activity
held a global interlock and the UI died; here "parked" simply means
"not runnable", and three workers run past it before it resumes.
- one_transition_in_flight: a context calling drain() gets a no-op, with
a second ready context queued so a buggy nested drain would actually
run something and be caught.
- async_wake: a real macrotask hop (setTimeout → mark_ready → drain),
the shape every production bridge has.
- deep_park_sizing: parks 64 live frames deep to measure what a park
actually costs.
The memory gate asserts the ceiling (peak live contexts, peak bytes),
that nothing leaked (live=0, bytes=0, created==finished), that nothing
was left mid-transition, and that refusals occurred (zero would mean the
illegal-operation scenarios stopped provoking).
Measured here: ~34 B/frame, 2200 B for a 64-frame park, 1 MB peak for 4
concurrent contexts. Recorded with the caveat that the harness's frames
carry three locals each, so this is a FLOOR — real bridges save far more
per frame (libcontext runs 512 K after a 64 K buffer silently
overflowed). The apparatus and its units are validated; the sizing
DECISION needs deep-park numbers from real bridges at D3/D4.
playwright.config: asyncify-firefox now matches every spec in ./asyncify
instead of only asyncify-races* — a new harness there is covered by
construction rather than by remembering to widen the pattern.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TEHGiiXMShNXbBr7gSJ7iz
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