feat(plan): extend CostModel with a size_params hook - #146
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`CostModel::rank_candidates` already lets a deployment reorder which `SummaryKind` answers an intent, but `SummaryParams` sizing (k / width / depth / precision) was still hardcoded in `boundary::bind_summary_with`, unreachable by any cost model. A deployment with its own accuracy-bound math (or a downstream catalog that only recognizes discrete parameter rungs) had no extension point short of forking `implementation_for_with`. Add `CostModel::size_params`, defaulting to the now-extracted `boundary::default_size_params` (byte-for-byte the same formulas `bind_summary_with` used inline before) so `DefaultCostModel` and every existing caller keep today's behavior unchanged. A deployment can now override ranking, sizing, or both, independently. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This was referenced Jul 22, 2026
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Summary
CostModel::rank_candidateslets a deployment reorder whichSummaryKindanswers anAggIntent, butSummaryParamssizing (k/width/depth/precision) was hardcoded inline inboundary::bind_summary_with, unreachable by any cost model.CostModel::size_params(kind, intent, eps, delta) -> SummaryParams, with a default body delegating to the newly-extractedboundary::default_size_params(the exact same formulas that were inline before — no behavior change forDefaultCostModelor any existing caller).control_planehas its own KLL/CMS/HLL parameter-sizing logic (in some cases tied to a downstream catalog's discrete supported-K rungs, not a continuous formula) that it needs to keep using while still adoptingimplement_tree_in_with's IR construction (schema/col/by plumbing) instead of forking it. This is the same "one extension point per deployment-specific decision" patternrank_candidatesalready established, one level deeper.Test plan
cargo test -p asap-plan— 26 passed (24 pre-existing + 2 new:size_params_default_body_matches_default_size_params,custom_cost_model_can_override_sizing_independently_of_ranking)cargo test --workspace— all green, no regressionscargo clippy -p asap-plan --all-targets— clean🤖 Generated with Claude Code