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Release notes: 2026-05-25 — sim-step-sim1-stub

Status: Ready for review
Repo: li-langverse/lic
Branch: feat/ph-hw-sim1 → PR into feat/ph-hw-multi-vendor
PH / REQ: PH-SIM SIM-1
Author: agent

Summary (one sentence)

PH-SIM SIM-1 adds sim_reset / sim_step on SimSessionStub (deterministic tick counter, no physics kernel) plus studio_sim_step_hook to sync studio profile then step.

Agent continuation (required)

  1. Read: packages/li-sim/src/lib.li (SIM-1 block), packages/li-studio/src/lib.li (studio_sim_step_hook), docs/game-dev/specs/li-engine-unified-sim-rfc.md.
  2. Run: lic check packages/li-sim/src/lib.li; lic check packages/li-sim/li-tests/smoke/sim_step_stub.li; lic check packages/li-studio/src/lib.li; lic check li-tests/composable/import_studio_sim_step_stub.li.
  3. Then: PH-SIM SIM-2 — replay buffers / checkpoint hooks on session or SimWorld per RFC.
  4. Blocked on: li-physics-runtime integrators, lis MCP tick persistence — none for this merge.

Changed (specific)

Area What Evidence
packages/li-sim sim_status_*, SimSessionStub.tick/last_dt, sim_reset, sim_step li-tests/smoke/sim_step_stub.li
packages/li-studio studio_sim_step_hook (profile apply + sim_step) smoke + composable
li-tests/composable import_studio_sim_step_stub.li monorepo manifest
docs/release-notes/2026-05-25-sim-step-sim1-stub.md this file agent continuation

Not changed (scope fence)

  • SimWorld / scene entity mutation / li-physics-runtime stepping — not implemented.
  • ml.rl.EnvPool → sim_step wiring — not implemented (SIM-3).
  • Replay / checkpoint (SIM-2) — not implemented.
  • lis MCP HTTP tick persistence — not wired.
  • LLVM / httpd / tier5 — not touched.

Breaking / Security / Performance / Downstream

  • Breaking: None — new fields on SimSessionStub default to tick=0, last_dt=0.0.
  • Security: N/A — in-memory int/float counter, no I/O.
  • Performance: N/A — O(1) increment per step.
  • Downstream: Studio timeline playback can call studio_sim_step_hook when wiring real ticks; RL agents should wait for SIM-3.

CHANGELOG entry (paste into Unreleased)

### Added
- **PH-SIM SIM-1 sim step stub** — `sim_reset` / `sim_step` on `SimSessionStub`, `studio_sim_step_hook`; smokes `sim_step_stub.li`, `import_studio_sim_step_stub.li` — [2026-05-25-sim-step-sim1-stub.md](docs/release-notes/2026-05-25-sim-step-sim1-stub.md).