XTRAIN-24: Prove HOMEGOLF score gain from XTRAIN or keep XTRAIN off the critical path

[AtlantisPleb]

Summary

Prove whether XTRAIN materially improves the HOMEGOLF or PGOLF score path or formally keep it off the critical path.

Related tracking issue: #633

Why

Current retained XTRAIN truth is real but still bounded:

• XTRAIN completes train-to-infer closure
• XTRAIN emits actual text
• direct and served inference still agree
• current retained XTRAIN BPB is still 4.202998425869111
• there is still no retained evidence that XTRAIN improves the HOMEGOLF score path

The current risk is spending iteration time integrating XTRAIN more deeply into HOMEGOLF without any proof that it helps score.

Scope

• define the exact experiment needed to attribute a HOMEGOLF score gain to XTRAIN
• either produce that retained gain on the same competitive PGOLF family
• or codify the “XTRAIN stays sidecar or non-gating” rule in docs and operator flow
• keep the issue focused on score relevance, not generic XTRAIN correctness

Acceptance Criteria

• either a retained HOMEGOLF score receipt improves because of XTRAIN involvement
• or the repo explicitly marks XTRAIN as non-critical to the HOMEGOLF competitive loop until such evidence exists
• the HOMEGOLF path docs and issue stack reflect the verdict clearly

References

• docs/2026-03-28-psionic-clean-main-xtrain-run-audit.md
• docs/2026-03-28-homegolf-xtrain-pgolf-tailrun-loop-and-xtrain-refresh-audit.md
• docs/2026-03-28-parameter-golf-winner-gap-and-psionic-path-audit.md

[AtlantisPleb]

This one now has a real resolved verdict.

The repo has formally taken the "keep XTRAIN off the HOMEGOLF critical path until score relevance is proven" branch of the issue.

That rule is frozen in docs/PARAMETER_GOLF_XTRAIN_TRACK.md:

• bounded XTRAIN stays visible in the shared dashboard grammar
• XTRAIN scores are not treated as HOMEGOLF or public-leaderboard-equivalent scores
• promotion stays held until retained evidence shows XTRAIN is score relevant to the downstream competitive loop

So we have not proven a positive HOMEGOLF score gain from XTRAIN. We have done the other honest thing this issue allowed: codify that XTRAIN is non-critical to the HOMEGOLF score path until such evidence exists.

Closing as completed.