Iter 36. Locks down the ADR-119 §2.1 forward-compat promise that
reserved flag bits round-trip unchanged through the parser. A future
protocol revision may light up bits 2 or 4..=15; today's parser
preserves them so a node running iter N can forward unknown bits to
a peer running iter N+M without losing information.
Added (in src/frame.rs::flags):
- pub const KNOWN_FLAGS_MASK = HAS_CSI_DELTA | PRIVACY_MODE | SELF_ONLY
(the three currently-named flags, occupying bits 0, 1, 3)
- pub const RESERVED_FLAGS_MASK = !KNOWN_FLAGS_MASK
(bit 2 + bits 4..=15 — every position not currently assigned)
- Docstrings reference ADR-119 §2.1 verbatim so a future reviewer
understands why the constants exist.
tests/reserved_flags.rs (8 named tests, all green, no_std-compatible
so they run in BOTH feature configs):
known_flags_mask_covers_exactly_three_named_flags
(count_ones() == 3 catches accidental flag additions that should
also update KNOWN_FLAGS_MASK)
reserved_and_known_masks_are_complementary
(mask | reserved == u16::MAX; mask & reserved == 0)
known_flags_do_not_overlap_with_each_other
(HAS_CSI_DELTA, PRIVACY_MODE, SELF_ONLY all on distinct bits)
header_preserves_reserved_flag_bits_through_round_trip
*** Headline test: set RESERVED_FLAGS_MASK on a header, serialize,
parse, verify the bits survived. ***
header_preserves_mixed_known_and_reserved_bits
(HAS_CSI_DELTA | PRIVACY_MODE | (1<<7) | (1<<14) — mixed case)
reserved_bits_do_not_collide_with_self_only_bit_3
(bit 2 is reserved but bit 3 is named — pins the asymmetry)
all_zero_flags_round_trip_cleanly
all_one_flags_round_trip_cleanly (stress: every bit set)
The new tests are no_std-compatible (no Vec / no serde) so they run
in both `cargo test --no-default-features` and default feature
configs. The no_default test count therefore jumps from 72 to 80.
ADR-124 status (iter step 0 sibling check):
- docs/adr/ADR-124-rvagent-mcp-ruvector-npm-integration.md unchanged
at 431 lines. SENSE-BRIDGE scope remains orthogonal.
ACs progressed:
- ADR-119 §2.1 "Reserved flag bits 2-15 lock in future-extension
order; any new bit assignment is a version bump." — the test now
enforces the OTHER half of this contract: a peer running the
future version can set a reserved bit and our parser will preserve
it through the round-trip rather than masking it off.
Test config:
- cargo test --no-default-features → 80 passed (72 + 8 no_std-compat)
- cargo test → 243 passed (235 + 8)
Out of scope (next iter target):
- PR-readiness pivot: witness bundle regeneration, CHANGELOG batch
across iters 1-36, AC closeout table for the PR description.
All in-crate ACs are now covered; remaining work is either
external-resource-gated (KIT BFId, Pi5/Nexmon) or PR-prep.
Co-Authored-By: claude-flow <ruv@ruv.net>
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