# Caller-only arithmetic failure: observed next bottleneck

Clean compiler source `9c5c1e37bf22da1ab8f6046d5b35c82085563438`, Go 1.27.1.
The plan was saved before execution. All five original source-fill assignments
and all original construction/evaluation cases remain unchanged. One additional
candidate appears immediately before `bounded`:

```text
boundary = input.used >= input.limit
cap = input.limit / (input.used - input.limit)
```

The local training input skips the cap. The local holdout reaches a divisor of
one. This candidate therefore receives local 1/1 and separate holdout 1/1.
The original caller construction input has `used=8, limit=8`, giving a zero divisor.

Observed result: CLI exit 1; six declared assignments and budget six; five recorded
attempts. The new candidate compiled successfully and its first native process
exited 2, without timeout or cancellation. The report retains 281 diagnostic bytes
and their digest; its generic failure is `bounded child failed (exit/timeout recorded)`.
No structured language-fault outcome was emitted. Earlier attempts remain in the
record, but the later `bounded` assignment was never tried and final evaluation
was not reached. The source arithmetic and execution result identify a useful
counterexample; the generic runtime diagnostic alone does not classify its cause.

## Intended next implementation

Represent supported arithmetic failures as explicit outcomes of executing a Gooo
candidate, carrying the original input and the originating activity/expression.
Run and reproduce those outcomes through the native driver, then allow bounded
construction to try the next combination. Preserve earlier successful deliveries
and distinguish failed evaluation from missing observation. Saved replay must
check the same outcome, budget and source identities with no new inference.

Toolchain failures, external cancellation, timeouts and unknown process failures
retain their terminal meaning. Classification should come from the generated
Gooo execution protocol; generic process-exit text is insufficient. Existing
interpreter and native integer arithmetic semantics must continue to agree.

This directory is a failing probe and an implementation target. It is not a claim
that runtime-failure continuation is available in 0.6.15.