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Release notes: 2026-05-25 — vertical-gap-sim-step-physics

Status: Ready for review
Repo: li-langverse/lic
Branch: feat/vertical-gap-sim-step-physics → PR into main
PH / REQ: PH-SIM SIM-1, vertical gaps #4 (domain step stubs), #9 (MD tier metadata)
Author: agent

Summary (one sentence)

Studio timeline stepping calls sim.scientific MD smoke on sim_scientific profile and physics.runtime physics_step on game, with studio_md_particle_tier_select_ok wired to li-scene tier metadata.

Agent continuation (required)

  1. Read: packages/li-studio/src/lib.li (studio_sim_step_hook, studio_game_step_hook, studio_md_particle_tier_select_ok), packages/li-sim-scientific/src/lib.li (sim_scientific_tick_stub), packages/li-scene/src/lib.li (MD tier types).
  2. Run: lic check --workspace; lic check packages/li-studio/li-tests/smoke/studio_sim_step_by_profile.li; lic check li-tests/composable/import_studio_sim_step_by_profile.li.
  3. Then: SIM-2 replay buffers; full SimWorld + scene sync for physics_sync_*; tier-2 MD oracle benches for sim_scientific viewport.
  4. Blocked on: lis MCP tick persistence, EnvPool RL hookup (SIM-3) — none for this merge.

Changed (specific)

Area What Evidence
packages/li-sim-scientific sim_scientific_tick_stub → run_md_lj_smoke composable + studio smoke
packages/li-studio deps li-sim-scientific, li-scene, li-physics-runtime; profile step hooks studio_sim_step_by_profile.li
li-tests/composable import_studio_sim_step_by_profile.li monorepo manifest
docs/release-notes/2026-05-25-vertical-gap-sim-step-physics.md this file agent continuation

Not changed (scope fence)

  • SimWorld entity mutation / replay (SIM-2) — not implemented.
  • ml.rl.EnvPool → sim_step (SIM-3) — not wired.
  • physics_sync_from_scene / physics_sync_to_scene — not called from Studio.
  • lis MCP HTTP server — not implemented.
  • Tier-2 MD/PDE competitive oracles — not added (display tier metadata only).
  • LLVM / httpd / tier5 — not touched.

Breaking / Security / Performance / Downstream

  • Breaking: None — new hooks; studio_sim_step_hook still returns sim_status_* codes.
  • Security: N/A — in-process float stubs, no I/O.
  • Performance: N/A — O(1) stub per frame; full MD bench rows separate.
  • Downstream: Studio native timeline can call studio_sim_step_hook; RL/automotive profiles still use generic sim_step only.

CHANGELOG entry (paste into Unreleased)

### Added
- **Vertical gap #4/#9 sim step physics** — `sim_scientific_tick_stub`, `studio_game_step_hook`, `studio_md_particle_tier_select_ok`, profile smokes — [2026-05-25-vertical-gap-sim-step-physics.md](docs/release-notes/2026-05-25-vertical-gap-sim-step-physics.md).