DC-PROTO-08

DC derived enforced

Once chain-sync enters a state where the server holds agency, the pure per-session reducer must return exactly one of: a legal RollForward, a legal RollBackward, a legal AwaitReply, or a structured deterministic session-close/error. It must not return an ambiguous wait state unless the wait condition is an explicit replay input.

Source: docs/planning/phase4-n-a-successor-invariants.md §1 (I-8), §2 (¬P-4)
Cluster: PHASE4-N-G
Authority surface: producer-side chain-sync server-agency reducer

Enforcement trace

Code

crates/ade_network/src/chain_sync/server.rs

Tests 12

producer_chain_sync_serve_request_next_idle_yields_roll_forward_when_served_has_block
producer_chain_sync_serve_request_next_idle_yields_await_reply_when_served_empty
producer_chain_sync_serve_find_intersect_known_point_yields_intersect_found
producer_chain_sync_serve_find_intersect_unknown_point_yields_intersect_not_found
producer_chain_sync_serve_done_terminates_session
producer_chain_sync_serve_rejects_illegal_grammar_pair
producer_chain_sync_advance_tip_idle_yields_none
producer_chain_sync_advance_tip_can_await_yields_roll_forward_when_block_available
producer_chain_sync_advance_tip_must_reply_yields_roll_forward_when_block_available
producer_chain_sync_advance_tip_can_await_yields_none_when_cursor_at_head
producer_chain_sync_serve_roll_forward_header_equals_accepted_block_header_bytes
producer_chain_sync_serve_replays_byte_identical_over_corpus

CI 1

ci_check_chain_sync_server_closure.sh

Cross-references

Strengthened in

Evidence

Reducer signature is total: every (state, in_msg) pair under client-agency returns Ok(ServerStep::Reply()) or Ok(ServerStep::Done) or Err(ProducerServerError::Grammar()). The match arm covering server-originated messages from client agency returns a Grammar error (defensive; the underlying BLUE state machine rejects these first).
Server-agency states (CanAwait/MustReply) are exited via either ServerReply::roll_forward(_) (data available) or ServerReply::await_reply() (parks in MustReply for advance_tip). Intersect leg always returns IntersectFound or IntersectNotFound. Done leg always returns ServerStep::Done.