Erratum — draft-fossil-submanifests-00 §7.2 / §8.1

Document	draft-fossil-submanifests-00
Section	7.2 — Peer Capability Gate (the client's duty after avoid-submanifests); 8.1 — Emission Gate (the same duty)
Type	Technical ("commits created during the session" names a situation neither implementation produces)
Status	Applied in draft-fossil-submanifests-00 (2026-10-19)
Reported	2026-10-18
Submitter	Dan Mestas
Found via	Implementing the pragma in go-libfossil and finding no code path the rule could apply to

1. Summary

§7.2 says a client that received avoid-submanifests "MUST NOT emit S cards in commits created during the session", and §8.1 repeats the rule as "in a commit against a server from which it has received the avoid-submanifests pragma in the current sync session". Neither zit nor go-libfossil creates a commit inside a sync session: a commit is made, and then autosync pushes it in a separate exchange. The rule as written never applies, and the draft does not say what "session" means across a commit-then-push, so an implementer cannot tell whether a pragma received on yesterday's push binds today's commit. The text should define the session and say plainly what the pragma binds.

2. The text in error

§7.2: "A client receiving it MUST NOT emit S cards in commits created during the session (Section 8.1)."

§8.1: "and MUST NOT emit one in a commit against a server from which it has received the avoid-submanifests pragma in the current sync session (Section 7.2)."

3. What the implementations do

zit records the pragma in a per-session, one-way latch (Client.avoid_submanifests in src/sync.zig) that a new session starts clear, and reads it together with the setting in clientMayEmitSCards. Its commit path runs outside any session, so the latch never reaches a commit; emission is governed by the repository's own setting. A zit server whose setting is false still stores an S-bearing artifact pushed to it, because the setting gates emission, not receipt. go-libfossil behaves the same way and recorded the rule as partially met (SM-7.2-3).

4. Corrected text

§7.2, replace the sentence with:

A sync session is one exchange between a client and a server, from its first request to its last reply. A client that receives the pragma MUST NOT emit S cards in a commit it creates during that session. A commit created outside a session is governed by the client's own enable-submanifests setting alone (Section 8.1); an implementation that commits first and pushes afterwards therefore never creates a commit the pragma binds, and the pragma informs it that the server's operator has not enabled emission there. The pragma does not gate receipt: a server stores an S-bearing artifact pushed to it whatever its setting, as Section 8.1 says of existing artifacts.

§8.1, replace "and MUST NOT emit one in a commit against a server from which it has received the avoid-submanifests pragma in the current sync session (Section 7.2)" with "and MUST NOT emit one in a commit created during a sync session in which it has received the avoid-submanifests pragma (Section 7.2)".

5. Observable consequence of the uncorrected text

An implementer can read the rule as binding every commit made while a server that sent the pragma is the autosync target, and build a writer that falls flat after one push to such a server, while zit and go-libfossil keep writing trees. The corrected text makes the two implementations' behaviour the specified one.

6. Implementations

zit and go-libfossil already behave this way; no change.