Practice loop (search-backed): spaced regression replay that never weakens the veto

Twin: examples/sdk_practice_loop.py · emits agent-learning.practice-loop.v1 · offline, no credentials. A coding agent can complete this page from the frontmatter alone.

1. What you are testing

The practice loop (search-backed) runs a six-phase round — assess, diagnose, drill, update, consolidate, calibrate — over the simulation contract's declared objective. Drills target measured ZPD; updates are layer-scoped; consolidated lessons land in an append-only store with a spaced-replay schedule. The load-bearing invariant: spacing governs between-promotion standing health, but at every candidate promotion the full frozen-row union replays regardless of schedule state — the promotion veto is never weakened.

The failure classes this page targets: a non-deterministic loop, a schedule state machine that drifts, a promotion that skips schedule-quiet rows, and a planted regression that goes undetected.

2. Run it

Generate the committed fixtures (the determinism pair, the schedule-history matrix, the zero-due promotion sweep, the non-forgetting interference run, and the budget-conservation ledger):

python examples/sdk_practice_loop.py artifacts/practice-loop.json

3. What you built

Run the postcondition verbatim:

python -c "import json; p=json.load(open('artifacts/practice-loop.json')); assert p['kind']=='agent-learning.practice-loop-readiness.v1', p; assert p['determinism_equal'] is True, p; print('ok')"

The artifact records that two identical-seed runs produce byte-identical phase artifacts after the envelope strip.

4. When it fails

Symptom	First-mile class	Doctor check
build refused with budget_undeclared	the manifest has no eval_budget	missing_engine_modules
build refused with objective_guards_missing	the simulation objective has no guards	missing_engine_modules
a promotion replayed fewer rows than the full union	a schedule filter leaked into the sweep	public_boundary_passed

5. Prove it / keep it

The practice_loop_readiness release gate recomputes these committed fixtures on every release-check: determinism, the schedule transition table, the zero-due promotion-veto sweep, the non-forgetting interference run, budget conservation, and the claims-lint all gate the release.