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el/docs/v1/experiments/cycles/18-async-half-expressible.md
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El SDK CI - dev / build-and-test (pull_request) Failing after 14m31s
rerun cycle 18 rather than reconstruct it
The async/future measurements were produced by a C stub in /tmp, and that
artifact was destroyed when the session worktrees were removed. The log then
asserted results with nothing behind them -- a claim inside an evidence record,
which is exactly what turns a chain of custody into a pile.

Rerun, not reconstructed. Rebuilding the missing file would have been a
fabrication with a fresh timestamp; rerunning produces new evidence with its own.

  lang/tests/integration/fixtures/future.c   the future, as a tagged heap object
  lang/tests/integration/async_future.sh     the harness, 6/6

  ok  unbound: synchronous, correct result
  ok  unbound: el_await on a non-future passes through, no crash
  ok  bound: does not crash
  ok  bound: the awaited result is correct
  ok  bound: the caller continues BEFORE the body finishes
  ok  bound: wrap returns in <10ms while the body takes 50ms

LABELLED AS A REPLICATION. The outcomes were already known when this harness was
written, so its expectations are NOT predictions committed in advance. Its
evidentiary value is that a third party can reproduce it, not that it was called
ahead of time. Recording it as anything stronger would corrupt the record it is
meant to repair.

The fixture also carries the P5 defect and its fix in a comment: the first
el_await dereferenced ->magic off an unvalidated slot and SIGSEGV'd on the
unbound path, sixty seconds after the same defect was diagnosed elsewhere in the
runtime.
2026-08-17 11:03:59 -05:00

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# async — half expressible, and the cycle that was dogma
**Status: replicated and corroborated. Three runs — the first was invalid.**
> **Chain of custody note, 2026-08-17.** The original measurements were produced
> by a C stub written in `/tmp`, and that artifact was destroyed when the session
> worktrees were removed. For a period this file asserted results with nothing
> behind them — a claim inside an evidence record, which is the defect that turns
> a chain into a pile. It was **rerun**, not reconstructed: reconstructing the
> missing file would have been a fabrication with a fresh timestamp.
>
> The fixture now lives at `lang/tests/integration/fixtures/future.c` and the
> harness at `lang/tests/integration/async_future.sh`, so a third party can
> reproduce this without taking my word for it. **6/6.**
>
> The replication is labelled as such: the outcomes were already known when the
> harness was written, so its expectations are not predictions committed in
> advance. Its value is reproducibility, not foresight.
## The first attempt was DOGMA, not science
I had just finished arguing that `@async` was expressible, then ran something to
confirm it. **No prediction was committed.** The test was rigged in a way that
should have been visible while writing it:
```c
pthread_create(&t,NULL,runner,NULL); pthread_join(t,NULL);
```
`join` immediately after `create` — the caller blocks until the body finishes.
That is a thread round-trip, not deferral. And the test printed the word
`DEFERRED` itself: I wrote the conclusion into the output and read it back.
```
Ishikawa on the rigged test
method ran after concluding, not to decide
machine nothing forces a prediction before execution
material the assertion was written into the output string
measurement no falsification criterion existed, so nothing could fail
root cause the test was authored by the party holding the conclusion,
with no commitment made before it ran
```
Discarded and re-run properly.
## Second run — predictions committed first
```
P1 the caller proceeds while the body runs expect TRUE
P2 interleaving is observable in timestamps expect TRUE
P3 the result cannot be retrieved — one 64-bit slot, no
future type, so the wrap either blocks or returns
something that is not the result expect TRUE
P4 therefore HALF expressible: fire-and-forget yes, await no expect TRUE
```
## Results — 4/4
```
[ 18 us] wrap RETURNS to caller
[ 29 us] body START
caller continues, got 0
[ 50176 us] body END (computed 42)
caller done
```
The caller got **0, not 42**. Both of my earlier claims were wrong in opposite
directions: "not expressible" was too strong — fire-and-forget works today,
bound after the build, no compiler change. "Expressible" was too strong the
other way.
## Follow-on cycle — a future is one more tagged object
```
P1 el_val_t already carries tagged heap objects TRUE 5 magic tags exist
P2 a future is one more TRUE
P3 the caller awaits and gets 42 TRUE
P4 ZERO compiler changes TRUE runtime C + one binding
P5 the unbound path still works FALSE SIGSEGV
```
**P4 is the result.** `@async` — called unexpressible for hours — needs no
compiler change. A future is one more magic-tagged heap object; `defer` returns
the handle, `el_await` blocks.
**P5 is the failure that mattered.** Sixty seconds after diagnosing
`let s: String = 42` as an arbitrary read, I wrote the identical defect into
`el_await`: reading `->magic` off an unvalidated slot. That opened cycle 19.