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Transformer-anchor unions differ between logging configurations #795

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@khatchad

A pre-existing schedule-sensitivity residue of the #753 class, reconfirmed while implementing #790: the whole-project transformer anchors (testNlpgnnFullDense3dInput, testNlpgnnFullEinsumViaMatmul) produce different cross-context union members under the FINEST default logging configuration versus the CI logging configuration, deterministically each way. The logging configuration changes evaluation timing, which changes the schedule, which changes which members some reads resolve; the #758 order-invariance work made the recorded dependency graph converge order-independently, but the config-induced schedule difference still reaches results on these anchors (the Jul 22 measurements' predecessor-pair split under CI logging was the same signature).

Consequence: any change that perturbs evaluation on these anchors (engine-visibility diversions, new composition arms) reshuffles their pinned unions per configuration, so pins cannot be made stable across configs. This blocks landing the #790 one-sided broadcast rescue, whose baked operand members inherit the sensitivity.

The diagnosis recipe from #790: run the anchor group under both configurations and diff the per-context union dumps; the divergent member's producing read is the one still consuming schedule-dependent state outside an engine-keyed query.

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