Iter 26 — closes the ABI gap between the Python and Rust SyncPacket
decoders. Before this, Python could decode the wire but had no helpers
to apply offsets or recover per-frame mesh time; any Python-side tooling
(host scripts, replay analysers, notebooks) would have to re-implement
the math from scratch and could drift from Rust silently.
New methods on the Python SyncPacket dataclass:
local_minus_epoch_us() -> int
Signed local-vs-mesh offset. Matches Rust byte-for-byte.
apply_to_local(local_at_frame_us: int) -> int
offset = epoch_us - local_us
return local_at_frame_us + offset
Identity at local_at_frame_us == self.local_us returns epoch_us.
mesh_aligned_us_for_sequence(frame_seq: int, fps_hz: float) -> int
Sequence-based interpolation matching Rust's identical method.
Includes u32 wraparound handling via masked-subtract — verified
against Rust's iter 17 `mesh_aligned_for_sequence_handles_seq_wraparound`.
3 new Python tests (10 total in TestSyncPacketParser, all green in 0.24s):
test_apply_to_local_recovers_epoch_at_sync_point
Identity at the sync point. Also verifies local_minus_epoch_us()
matches §A0.10's measured 1,163,565 µs bench number.
test_apply_to_local_preserves_inter_frame_delta
Frame arriving 5 s after the sync on the follower's local clock
produces mesh time exactly 5 s after sync.epoch_us.
test_mesh_aligned_us_for_sequence_matches_rust
Cross-language parity with Rust's
`end_to_end_sync_decode_then_frame_mesh_recovery` (iter 20):
100 frames after sync.sequence at 20 fps = sync.epoch_us + 5 s.
Cross-checks via apply_to_local — both paths must agree.
Test count after iter 26:
Python TestSyncPacketParser: 10/10 (was 7/7)
Rust sync_packet::tests: 15/15
Combined: 25 unit tests defending the SyncPacket contract across
the two host language stacks.
Co-Authored-By: claude-flow <ruv@ruv.net>
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