alkgit/docs/architecture/open-questions.md

status, last_updated

status	last_updated
draft	2026-09-25

Open Questions

All unresolved architecture questions, centrally tracked. Status values: open (needs resolution now), partially resolved (decision made but a narrower question remains — named in the entry), resolved (decision made, ADR recorded), deferred(scope) (waiting on external information — blocked-on condition stated), deferred(unclear) (pieces exist, shape needs investigation). See docs/sdd_process.md for the deferral protocol (blocker tasks in tasks/architecture/).

Door type classifies reversal cost: one-way decisions are expensive/impossible to reverse once published (wire formats, public API shapes); two-way decisions can be revisited while nothing is published. Door type does not change urgency — all decisions here need resolution when their impacts say so; it records how careful the resolution must be.

Deferred / Blocked summary

OQ	Status	Blocked on / investigation
OQ-05	deferred(scope)	ecosystem need for sha256
OQ-03	partially resolved	first-publish timing (release decision; the freeze inventory lives in backend.md/transport.md)

OQ-02 and OQ-04 resolved this cycle (ADR-014, ADR-013); OQ-08/06/07/09/01 resolved in earlier cycles. No open or deferred(unclear) questions remain.

Theme: composition / crate shapes

OQ-09: Slim-crate model — doors as family infrastructure, git as a payload service

• Origin: user session (2026-09-21); ADR-006, ADR-001, ssh.md
• Status: resolved — ADR-010 (pure protocol crate, the alktty/ alktunnels template): single alkgit crate, producer/consumer halves, backend traits with feature-gated gix, no doors, no binary; ALPN alk/git; http mounting → alkhttp git feature; git-over-ssh → alkssh (russh scaffolding dropped); the monorepo/binary framing was an init-agent artifact (vision amended).
• Resolution: [decisions/010-pure-protocol-crate.md]. All five sub-decisions recorded there (ssh deletion, http home, crate granularity, backend-trait surface, binary fate).
• Cross-references: ADR-001/006 (superseded), OQ-01, OQ-03, OQ-08, doors.md, backend.md, overview.md

OQ-01: HTTP adapter home and composability (alkhttp git feature vs alkgit-owned factory)

• Origin: user session question (OQ-01, resolved 2026-09-21)
• Status: resolved (subsumed by OQ-09/ADR-010) — the smart-http stateless substrate stays in alkgit (IO-abstract); the http mounting (routes, content types, with_extra_routes wiring) becomes an alkhttp git feature published after alkgit's first publish. The ADR-006 router-factory shape is superseded; the alkhttp-side feature is the outcome.
• Cross-references: ADR-006 (superseded), ADR-010, doors.md

OQ-03: Downstream embedding surface (what "embeds alkgit" means concretely)

• Origin: [overview.md], [transport.md], vision §"ALPN as a service"
• Status: partially resolved — the shape is settled (ADR-010): embedding = one crate + backend traits (own storage via default-features = false, or the gix/registry-file features) + optional door features. What remains deferred is the publish-time API freeze itself: which type/feature/op names are pinned at first crates.io publish. ADR-012 added the git/repo/* op set (names + schemas) to the freeze inventory.
• Door type: one-way (API freeze is registry-visible to dependents)
• Priority: medium
• Impacts: blocks the first publish only, not implementation.
• Blocked on: first-publish timing (a release decision, not an architecture question). The API surface inventory lives in backend.md §public API and transport.md §public API. ADR-013/014 added the push/negotiation trait surface (GitPackIngest binding, GitPackGen::common_haves) to the freeze inventory.
• Cross-references: ADR-010, ADR-002, ADR-012, ADR-013, ADR-014, backend.md, transport.md

Theme: transport / protocol

OQ-02: V2 multi-round negotiation (ack/NAK logic, wait-for-done retirement)

• Origin: [transport.md], poc2-findings §"does NOT settle"
• Status: resolved — ADR-014 (V2 negotiation ack loop). The duplex-capture walkthrough against git 2.43.0 (ground-truth negotiation mock, cross-checked against fetch-pack.c) resolved the grammar: no- done rounds get acknowledgments (ACK <oid> per recognized have, NAK when none, flush — never ready, so FLUSH is always the terminator); the done round generates closure(wants) − closure(haves) with no cross-round server state (clients re-send wants + commons every round); wait-for-done stays and the advertisement text is unchanged; the ack check is a new backend-trait method (common_haves) keeping the honest boundary at the seam. Captures: docs/research/negotiation-captures.md.
• Resolution: [decisions/014-v2-negotiation-ack-loop.md]
• Cross-references: ADR-003, ADR-004, ADR-005, ADR-009, ADR-014, transport.md §fetch, backend.md §"The trait family" (GitPackGen)

OQ-04: receive-pack (push) — validation gap

• Origin: [transport.md], poc3-findings §"does NOT settle"
• Status: resolved — ADR-013 (receive-pack state machine). The walkthrough against real git push captures (git 2.43.0: file://, git://, smart-http, plus raw stdio requests into real git receive-pack) resolved every listed unknown: the push path is V0-framed by upstream design (no version negotiation, ADR-003 governs fetch only); the advertisement is a V0-shaped ref advertisement (caps on the first ref line, capabilities^{} sentinel only for empty repos) with served set report-status(-v2) delete-refs side-band-64k atomic ofs-delta object-format=sha1 (+ push-options config-gated); shallow request lines are rejected up front for v1 (symmetric with fetch); thin packs accepted with bases from the server odb (default client behavior, no capability); ingestion = Bundle::write_to_directory_eagerly + gix-fsck + one gix-ref transaction per push (.keep-guarded pack landing); CAS timing is unpack-first-then-per-ref (observed upstream order); status report is band-1 pkt-line-framed with inner flush when sideband was selected. Captures: docs/research/push-captures.md.
• Resolution: [decisions/013-receive-pack-state-machine.md]
• Cross-references: ADR-003, ADR-004, ADR-005, ADR-009, ADR-013, transport.md §receive-pack, backend.md §"The trait family" (GitRefs, GitPackIngest), doors.md

OQ-05: sha256 support policy

• Origin: [transport.md], git-protocol.md §"Open items"
• Status: deferred(scope)
• Door type: two-way
• Priority: low
• Impacts: none for v1 (sha1 pinned); feature-flag passthrough compiles but is untested end-to-end.
• Blocked on: ecosystem need (a real client/repo requiring sha256) or upstream gix sha256 maturity; POC-2 left the pipeline hash-generic but untested. Tracker task: tasks/architecture/oq-05-sha256.md.
• Cross-references: ADR-003, ADR-004

Theme: identity / auth

OQ-08: Registry identity space + vault placement (narrowed)

• Origin: [overview.md], [doors.md], [backend.md]; originally "identity sources per front door"
• Status: resolved — ADR-011 (per-repo authorization): the identity model is alkcall's resolved Identity keyed on its stable logical id (alkcall ADR-025 property, referenced); alkgit stores no identity records; grants live in repo records; the public+read / always-authenticated-write policy is alkgit-core's authorize function (the clause ADR-007 pinned but the static ACL engine could not express); vault placement resolved as nothing to place in v1 (no credential-shaped material in metadata).
• Resolution: [decisions/011-per-repo-authorization.md]
• Cross-references: ADR-007, ADR-008, ADR-011, ADR-012, OQ-06, OQ-07, backend.md §GitRegistry, doors.md

Theme: storage / metadata

OQ-06: Registry/metadata backing store (gix feature)

• Origin: [backend.md] (was storage.md), ADR-008
• Status: resolved — ADR-012 (registry backing + write surface): the alknet repo/adapter pattern applied — GitRegistry read trait + GitRegistryStore write supertrait; default backing is the registry-file feature (per-repo record files + in-memory index, config-seeded, op-mutable, atomic writes — no gitoxide); persistence adapters (SQLite et al.) are future, separate, additive, gated by a real deployment need — the deferred "scale requirements" never gated the default, only that future adapter.
• Resolution: [decisions/012-registry-backing-and-ops.md] §1–2, §4
• Cross-references: ADR-008, ADR-010 (feature story amended), ADR-011, backend.md §feature model

OQ-07: Admin API operation set (v1 scope)

• Origin: [overview.md], alk-stack.md §"The gitea lesson"
• Status: resolved — ADR-012 (§3, §5): the crate ships a minimal CRUD op set (git/repo/{create,delete,update,get}) as thin call ops over GitRegistryStore, Visibility::External, always-on, gated by scopes (global tier, e.g. git:admin / git:repo:create) + ownership (self-owned tier; create mints ownership per alkcall ADR-011 and seeds the creator's grants — ownership never implies git access, ADR-011). The old "Internal ops over an admin listener" framing is superseded (right mechanism, wrong axis — visible-surface = authorized-surface is served by the ACL). Ops stay record-scoped; anything beyond repo records (users, orgs) is a downstream platform crate (the recorded split trigger, ADR-012 §5).
• Resolution: [decisions/012-registry-backing-and-ops.md] §3, §5
• Cross-references: ADR-007, ADR-011, ADR-012, alkcall ADR-017/011, backend.md §"The two op kinds"