alkblobs/tests/conformance

The conformance suite — home and conventions

The in-crate conformance harness for alkblobs' engines. Decided point (docs/plans/implementation.md, 2026-10-11): engines are features of one crate, so the suite lives in-crate, factory- parameterized over engine constructors — the alkstore ADR-017/022 contract-suite pattern adapted (there a sibling suite crate over Box<dyn Store>; here one test target over factories whose open vends the future Store facade, whose concrete type wave 2 binds).

This document is the convention's normative home on the test side (the in-code module docs in main.rs/factory.rs/stamp.rs restate their slices). Waves 2–6 grow columns against it: one column per engine, each column the same rows run against that engine's factory.

Row anatomy

A row is one named, independently-runnable property — an async function taking a StoreFactory (not a store), asserting by panicking on violation (a failing row is a test failure naming the property and expectation; the family-wide no-panic rule is relaxed here by the suite's test-side purpose).

Row naming

• snake_case, and the name states the property, not the engine (e.g. round_trip_known_length, dedup_is_one_pool_entry). The engine dimension is the column (which factory the row runs against), never the row name — that is what makes rows engine-uniform.
• Dimensions a property spans within one run — the content matrix, both put paths, both tiers where the invariant ranges over them — loop inside the row's body. A genuinely different property (e.g. sweep safety's fleet form vs its single-node form) is a separate row, not a flag inside the owner.
• Planned row families are registered in the invariant backlog (table below); a row that does not trace to a backlog entry is not a conformance row.

Contract stamps (the ADR-017 §4.2 convention adapted)

Every row is version-stamped with a doc-comment list item beginning Contract stamp:, citing the spec § and/or ADR § that pins the behavior tested:

/// <one-line statement of the property>
///
/// Contract stamp: store-api.md §Invariants 2; ADR-003 (whole-value
/// put is CAS first-writer-wins); ADR-005 (re-put refcounts).
pub async fn dedup_is_one_pool_entry<F: StoreFactory>(factory: &F) { ... }

Rules:

• The stamp cites the ADR § / spec § that pins the property — never a bare "wave 2" or a date. Several stamps are allowed when one row tests several changes' behavior together.
• A row added to pin a new contract addition is stamped with that addition's ADR; a row whose property predates the suite is stamped with the ADR/spec section that pinned it.
• A later change that amends a row's property appends to its stamp list; rows accumulate stamps, the ADRs' own texts record the history.
• Contract stamp: is greppable — grep -rn "Contract stamp:" tests/conformance/ is the stamp inventory.
• Rows are also free of engine-specific code by construction: a row may not branch on factory.name().

One normative owner per property

Each property has exactly one normative owner: the suite row. Engine-specific unit tests inside src/ may duplicate coverage for debugging convenience, but the suite row is the normative assertion — an engine's conformance claim rests on its column being green, not on its in-crate tests. When the suite itself needs per-engine divergence (the fleet-form sweep safety against postgres, INV-4), that is its own row with its own owner stamp, still one per property.

The factory contract

factory.rs pins the [StoreFactory] shape. The contract:

• open() vends a fresh, isolated store instance. No state is shared between rows or between columns: a fresh backing store per call — a fresh temp directory (local), a fresh pool (mem), a fresh schema or file (sqlite/postgres/pg-lo) — so a property's rows never observe another property's entries. Isolation is the implementer's owned guarantee.
• teardown() is idempotent and safe to run against an abandoned store: a failing assertion panics the row (early exit, no teardown on that path), so teardown must also make sense over a dropped / half-open instance. The factory owns what teardown means — deleting the temp dir, dropping the schema, closing the pool — and owns the isolated-ness guarantee above.
• Factories are Send + Sync: shareable across row runs.
• The wave-2 binding — made and recorded. The Store facade type landed with wave 2's store-construction task as a concrete type (alkblobs::Store, engine-blind; src/store.rs holds the engine- representation design point). The binding made the anticipated shape correction: the skeleton's Store associated type collapsed into the concrete facade — open() vends alkblobs::Store directly (factory.rs records the ruling; the wave-1 mock probe retired with it, replaced by the mem-gated binding demo factories in main.rs). A new engine column binds by implementing the trait; there is no longer a vendible type to choose.
• The row body owns its lifecycle. A row calls open() first — a fresh, isolated store per call — drives its assertions, and calls teardown() before returning; a failing assertion panics the row before teardown runs (the early exit above), which is why teardown() must make sense over the abandoned instance — dropped or still alive at unwind. The mem column's structural tests (factory_teardown_is_safe_against_a_panicking_row) exercise that path; isolation itself (fresh state per open, nothing shared) is exercised alongside (factory_open_vends_fresh_isolated_stores).

The SKIP posture

SQL-attached factories (postgres, pg-lo) ride a server (dockerized postgres) whose connection settings come from the environment. When no server is reachable, the column skips cleanly: a skip is not a failure, and the harness reports it as skipped rather than green or red. Two sides to keep honest:

• Engine waves' acceptance criteria require green against the server (the alkstore harness convention) — a skip never substitutes for acceptance.
• Server-less engines (mem, sqlite, local, and any future dependency-free engine) never skip: their columns must always be green in every environment.

The invariant backlog (rows-to-grow)

The seven invariants of store-api.md §Invariants, registered as the table every wave's rows grow against. Traceability: each row family names its store-api.md invariant and the ADRs pinning it. A suite row asserting something outside this table (or outside a wave's specced additions) needs a backlog entry and its stamp first.

#	Invariant (store-api.md §Invariants)	Row family	Pinning text	First column
INV-1	Whole-blob put/get round-trips byte-identical under the canonical derivation — both tiers, both put paths, every shipped engine	one round-trip family; content matrix and put paths loop in-body; per-engine columns	store-api.md §Invariants 1; ADR-002 (derivation); ADR-003 (put paths, dispatch); ADR-007/008/009/011 (engines)	wave 2 — mem (kv tier), then local (large tier)
INV-2	Dedup: identical content twice (same or different path) is one pool entry	one dedup row, same-path and different-path legs	store-api.md §Invariants 2; ADR-003 (CAS first-writer-wins); ADR-005 (re-put refcounts)	wave 2 — mem
INV-3	Stage hygiene: failure mid-put leaves zero stage files / no entry; success leaves exactly one committed entry	one hygiene family over both put paths and both failure modes (discard, failed commit)	store-api.md §Invariants 3; ADR-010 §1 (staged-put contract); ADR-003	wave 2 — mem (degenerate stage) and local
INV-4	Sweep safety: exact counts with correct liveness; aborting sources delete nothing. Engine-gated fleet form (DB-backed pins + sweep lease vs postgres)	one single-node family; the fleet form is its own engine-gated row family (runs under --all-features)	store-api.md §Invariants 4; ADR-005 (windows, sweeps); ADR-008 (fleet form); ADR-012 §1/§4/§6.7; ADR-013 §2	wave 2 — mem (in-process protocol); fleet form waits for wave 6
INV-5	list() correctness is observable only through GC	list-correctness asserted through sweep outcomes (exact counts), never by comparing lists directly	store-api.md §Invariants 5; ADR-003 (complete + well-formed list()); ADR-005	wave 2 — mem
INV-6	stat/size returns entry length without fetching content	one stat-discipline family per engine column	store-api.md §Invariants 6; ADR-008 (size probe); ADR-009 (pg-lo companion-row probe)	wave 2 — mem
INV-7	Engine-conformance uniformity: every engine's bodies pass the same contract suite mem passes	the meta-gate — a column's green run is the row; no separate test	store-api.md §Invariants 7; ADR-010 §1; ADR-011 §2 (mem's reference role)	wave 2 — mem defines it

The reference row set (INV-7's basis)

The mem column's rows (rows.rs) are the reference row set — the required set every other engine's rows mirror (ADR-011 §2, mem's contract-reference role; store-api.md §Invariants 7). A column mirrors this inventory row-for-row against its own factory; an addition to the set propagates to all columns (INV-7). The INV-row families are the engine mirror targets — the round-trip family covers the tier the column's engine serves (mem: the kv tier; local: the large tier). The two constructor-mode rows mirror wherever that configuration is constructible: a column with a kv-only factory runs the kv-only row against it — the row discovers the mode's threshold by probing, since known-length rejections read nothing, and requires the threshold materializable for its at-threshold legs (≤ 8 MiB, MAX_BOUNDARY_MATERIALIZATION).

Row (rows.rs)	Traces to
round_trip_puts_and_gets_are_byte_identical	INV-1 (content matrix, both put paths, in-body)
dedup_identical_content_is_one_pool_entry	INV-2 (same-path and cross-path legs)
stage_hygiene_zero_residue_on_failure_exactly_one_entry_on_success	INV-3 (both paths, both failure modes)
sweep_counts_are_exact_across_the_full_protection_set	INV-4 (happy shape: full protection set)
sweep_without_liveness_sources_aborts_and_deletes_nothing	INV-4 (abort shape: NoLivenessSources)
sweep_with_a_failed_protect_callback_aborts_and_deletes_nothing	INV-4 (abort shape: ProtectFailed)
sweep_is_single_flight_the_contended_second_aborts_as_data	INV-4 (abort shape: SweeperLock lease)
sweep_racing_a_pinned_put_never_deletes_the_protected_entry	INV-4 (the sweep-vs-put race)
list_correctness_is_observable_through_sweep_outcomes	INV-5 (exact counts, never list comparison)
stat_reports_len_and_algorithm_without_fetching_content	INV-6 (the stat-discipline family)
mem_only_mode_accepts_every_length_on_both_put_paths	constructor mode (ADR-011 §4)
kv_only_mode_rejects_over_threshold_puts_at_put_time	constructor mode (ADR-012 §6.2)

Stamps live on the rows themselves — grep -rn "Contract stamp:" tests/conformance/ is the inventory. The INV-4 rows beyond the families' first shapes (the SweeperLock abort) complete the three GcAbortCause variants within the single-node exact-count family (ADR-013 §2's lease, its in-process ADR-012 §5 form).

The schedule-relative reading for SQL-backed columns (the mirror convention's amendment)

The reference set's single-sweep exact-count rows are the inline-form host's (mem): there a completed sweep's candidates_staged == deleted + cancelled_by_arbitration holds over its same-sweep staged set. The durable form's semantics differ — staged this sweep, executed by the next (ADR-012 §6.7) — so SQL-backed columns read every exact-count assertion relative to the staged schedule: the staging sweep reports candidates_staged as the newly dead set and deletes nothing; its executor (the next sweep) reports deleted + cancelled_by_arbitration summing exactly to that staged set. Recorded, citing ADR-012 §6.7:

• INV-4 and INV-5 run the durable-schedule equivalents on SQL-backed columns — the two-sweep exact-count rows over the full protection set, the sweep-vs-put race across the window delay, and list correctness through durable-schedule outcomes (README §Columns beyond the reference set grows the rows table). The SweeperLock abort shape is form-independent (abort before staging) but its reference holder-completion leg is inline-form; SQL-backed columns run the holder-stages-only form (its staged set waits for the next sweep to execute).
• INV-2 and INV-3 — whose mirror rows observe their invariants through sweep outcomes — likewise assert their counts relative to the schedule: zero residue after failures is still staged-0; a success's exactly-one-entry is staged-1 then deleted-1 across the two sweeps. INV-1, INV-6, and the constructor-mode rows consume no entry-dependent sweep counts and mirror verbatim.
• Aborts are form-independent: NoLivenessSources and ProtectFailed abort before staging or executing — counts all zero on the durable form too — so those rows mirror directly.

Columns beyond the reference set (INV-7's mirror + extension)

The constructor-mode rows of the reference set run wherever the mode they name is constructible (README §The reference row set). A multi-tier column mirrors the set and grows its own rows for what its configuration carries that the reference set's single-tier host did not: the dispatch-coverage shape (ADR-012 §6.3 — both tiers load-bearing) and the engine's tier-specific properties. Those rows are still conformance rows — ADR-stamped, named for the property, traced — but they take the column's concrete factory instead of the StoreFactory trait: they observe the backing medium, which an engine-uniform row (unable to branch on any engine, and unable to see any tier's residency through the facade) cannot. Tier placement is facade-invisible by design; with kv = mem, the medium itself is the oracle — the mem kv tier never touches the factory's disk, so a committed file outside the staging area under the column's temp root is exactly one large-tier entry, and its absence beside a served read is exactly a kv-tier entry.

The local column's own rows (tests/conformance/local_column.rs, the dispatch-coverage and local-specific families):

Row	Traces to
routing_is_a_pure_function_of_length_across_put_paths_and_re_puts	ADR-003 §Dispatch policy (purity/no-migration); ADR-012 §6.3; INV-7 facade-contract row
threshold_boundary_lengths_route_deterministically	ADR-003 §Dispatch policy (at/below/above the threshold; constructor-tuned re-route); ADR-012 §6.3
kv_tier_misses_fall_through_to_the_large_tier_per_op	ADR-012 §6.1 (fall-through per op); ADR-012 §6.5 ruling 5 (miss shapes); ADR-006
stage_hygiene_exact_counts_on_disk_over_both_put_paths	INV-3's stage form (exact counts on disk); ADR-010 §1; ADR-003
pread_windows_read_committed_files_mid_slices_and_eof_clamped	store-api.md §Read path; ADR-010 §1 (streaming cursor); ADR-006
virgin_store_reads_are_no_ops_on_a_fresh_root	store-api.md §Error model (virgin-store semantics); ADR-012 §6.5
sweep_counts_stay_exact_over_both_tiers	INV-4/INV-5's both-tiers form (exact counts + list correctness through outcomes); ADR-005; ADR-012 §1/§6.3/§6.7

The dual-tier threshold is declared configuration, not a behavioral probe. The kv-only reference row discovers its factory's threshold by probing (rejections read nothing — free). A dual-tier store never rejects a length, and tier residency is facade-invisible, so there is nothing to probe: the dispatch rows take the threshold the column's factory declares (the same value its constructor took — configuration, like the mem column's kv-only threshold). The mem-only and kv-only mode rows do not mirror onto the dual-tier factories (the precondition mode() shapes they assert are not this column's mode); the dispatch rows are the dual-tier mode's facade-contract coverage.

The sqlite column's own rows (tests/conformance/sqlite_column.rs, the first SQL-backed column — the default-build production shape, kv = sqlite + large = local, feature sqlite default-on, ADR-007/013 §4): the dispatch-coverage rows with the placement oracle adapted by medium — both tiers are on disk now, kv entries live in the sqlite file (rows in the blobs table), large entries under the local root — and the durable-schedule sweep rows (§The schedule-relative reading for SQL-backed columns; ADR-012 §6.7; the window's gc_window rows are the schedule observer). The form-independent reference rows mirror verbatim: the INV-1 round-trip family and the INV-6 stat-discipline row against the dual-tier factory, the NoLivenessSources/ProtectFailed abort shapes (form-independent — abort before staging), and the kv-only rejection row against a kv-only(sqlite) factory (threshold-agnostic by discovery, unchanged; the threshold materializable per the configuration contract).

Row (sqlite_column.rs)	Traces to
dedup_identical_content_is_one_pool_entry	INV-2 (same-path and cross-path legs; counts read against the durable schedule, one row-oracle leg)
stage_hygiene_zero_residue_on_failure_exactly_one_entry_on_success	INV-3 (the degenerate kv stage form through the injectable failure modes; schedule-relative counts)
two_sweep_exact_counts_over_the_full_protection_set	INV-4/INV-5 (the full protection set across two sweeps — staged this sweep, executed by the next; the both-tiers form)
a_put_landing_during_the_window_survives_the_executing_sweep	INV-4 (the sweep-vs-put race across the window delay; execution-time re-arbitration)
the_contended_second_sweeper_aborts_as_data_and_the_holder_stages_only	INV-4 (the SweeperLock abort shape — abort before staging; the holder's durable-form completion: stages only)
list_correctness_is_observable_through_durable_schedule_outcomes	INV-5 (exact counts, never list comparison)
routing_is_a_pure_function_of_length_across_put_paths_and_re_puts	ADR-003 §Dispatch policy (purity/no-migration); ADR-012 §6.3; ADR-012 §6.7 (schedule-relative dedup legs); ADR-007; INV-7 facade-contract row
threshold_boundary_lengths_route_deterministically	ADR-003 §Dispatch policy (at/below/above, tuned + shipped-default thresholds); ADR-012 §6.3; ADR-007
kv_tier_misses_fall_through_to_the_large_tier_per_op	ADR-012 §6.1 (fall-through per op); ADR-012 §6.5 ruling 5 (miss shapes); ADR-006; ADR-012 §6.3; ADR-007
virgin_store_reads_are_no_ops_on_a_fresh_file	store-api.md §Error model (virgin-store semantics); ADR-012 §6.5; ADR-007 (the no-tables-yet read tolerance — engine-instrumented, the facade's fresh-file form)

The sqlite column's window delay is the test tuning (ADR-008 §2's legal degenerate tuning, Duration::ZERO — execute-on-next-sweep): the schedule the durable rows assert against is exactly the next-sweep executor form.

The postgres column's own rows (tests/conformance/postgres_column.rs, the first SKIP-posture column — the fleet-capable-kv shape, kv = postgres + large = local, feature postgres default-off, ADR-007/012 §5): the durable-schedule sweep rows mirror the sqlite column's family (§The schedule-relative reading for SQL-backed columns; ADR-012 §6.7 — the same window delay tuning, 0 — execute-on-next-sweep) and the dispatch rows with the placement oracle adapted by medium again — kv entries live as rows in the pg schema's blobs table, large entries under the local root (an independent connection counting the schema's rows vs the root's committed files; the column's own rows also watch the schedule itself, the schema's gc_window rows). The form-independent reference rows mirror verbatim: the INV-1 round-trip family and the INV-6 stat-discipline row against the dual-tier factory, the NoLivenessSources/ProtectFailed abort shapes (form-independent — abort before staging), and the kv-only rejection row against a kv-only(postgres) factory (threshold-agnostic by discovery, unchanged; the threshold materializable per the configuration contract). Connection settings ride the environment (ALKBLOBS_PG_HOST/PORT/USER/PASSWORD/DB) and the runners gate behind a reachability probe; the factories follow the alkstore pg-factory pattern (alkstore-postgres contract_suite.rs): a fresh engine-owned schema per open(), tracked per-instance, teardown DROP SCHEMA IF EXISTS … CASCADE over exactly the minted schemas (idempotent, owned, panicking-row-safe — CASCADE removes dependents server-side while the abandoned store's pooled connections fail closed on next use).

Row (postgres_column.rs)	Traces to
dedup_identical_content_is_one_pool_entry	INV-2 (same-path and cross-path legs; counts read against the durable schedule)
stage_hygiene_zero_residue_on_failure_exactly_one_entry_on_success	INV-3 (both put paths, both failure modes; schedule-relative counts)
two_sweep_exact_counts_over_the_full_protection_set	INV-4/INV-5 (the full protection set across two sweeps — staged this sweep, executed by the next; the both-tiers form)
a_put_landing_during_the_window_survives_the_executing_sweep	INV-4 (the sweep-vs-put race across the window delay; execution-time re-arbitration)
the_contended_second_sweeper_aborts_as_data_and_the_holder_stages_only	INV-4 (the SweeperLock abort shape — abort before staging; the holder's durable-form completion: stages only)
list_correctness_is_observable_through_durable_schedule_outcomes	INV-5 (exact counts, never list comparison)
routing_is_a_pure_function_of_length_across_put_paths_and_re_puts	ADR-003 §Dispatch policy (purity/no-migration); ADR-012 §6.3; ADR-012 §6.7 (schedule-relative dedup legs); ADR-007 §5; INV-7 facade-contract row
threshold_boundary_lengths_route_deterministically	ADR-003 §Dispatch policy (at/below/above, tuned + shipped-default thresholds); ADR-012 §6.3; ADR-007 §5
kv_tier_misses_fall_through_to_the_large_tier_per_op	ADR-012 §6.1 (fall-through per op); ADR-012 §6.5 ruling 5 (miss shapes); ADR-006; ADR-012 §6.3; ADR-007 §5
virgin_store_reads_are_no_ops_on_a_fresh_schema	store-api.md §Error model (virgin-store semantics); ADR-012 §6.5; ADR-007 §5 (the constructor always ensures the schema — the facade's fresh-schema form of the tolerance)

The pg-lo column's own rows (tests/conformance/pg_lo_column.rs, the second SKIP-posture column — the LO-medium column, ADR-009, landed wave 5): the reference inventory's form-independent rows mirror verbatim against a dual-tier factory (INV-1's round-trip family over the content matrix, INV-6's stat-discipline row — whose non-fetching discipline rides ADR-009's companion-row probe on this medium — and the NoLivenessSources/ProtectFailed abort shapes), and the column grows the durable-schedule sweep family (§The schedule-relative reading for SQL-backed columns; ADR-012 §6.7 — the same window delay tuning, 0 — execute-on-next-sweep), the dispatch rows with the placement oracle adapted to the LO medium (large entries are companion rows + LOs — an independent connection counting lo_entries and probing pg_largeobject; kv entries per the factory's kv engine: the mem-pglo factory's kv half is in-process, the mem introspection shape, the postgres-pglo factory's kv half counts the kv schema's blobs rows), the INV-1 extension row (the LO medium's ranged reads across the shipped window edge, EOF clamping, and the beyond-length clean failure against a planted overclaiming companion row), and the virgin-store row. No kv-only rejection row — no kv-only pg-lo constructor exists (pg-lo is a large engine; the postgres column hosts that row for the SQL kv engines).

The two factories span feature pairs — the first column whose factories need different feature sets (a recorded design point): DualTierMemPgLoFactory (kv = mem + large = pg-lo, the one-window-host rule's named test topology — the durable-schedule rows run with the window hosted on the large engine, gc_window in the pg-lo schema) gates on all(feature = "mem", feature = "pg-lo"); DualTierPostgresPgLoFactory (kv = postgres + large = pg-lo on one pg instance — the consolidation posture) gates on all(feature = "postgres", feature = "pg-lo") and carries the dormancy row (the pg-lo schema carries no gc_window; the window lives on the kv schema — ADR-012 §5); the column's full run (acceptance) is --all-features against the server. The factories follow the alkstore pg-factory pattern with the LO-isolation corollary carried in the engine task's recorded shape (the C7 lesson): a fresh dedicated database per open() (unique per call, tracked per-instance; engine schemas minted inside it), teardown reaping the instance's LOs (SELECT loid FROM lo_entries → lo_unlink), dropping exactly the minted schemas (DROP SCHEMA IF EXISTS … CASCADE), and dropping the database (WITH (FORCE)) — idempotent, panicking-row-safe, with a drop-guard janitor per open backing the abandoned paths — so zero LO residue on the shared harness database is structural (the engine suite's shared_harness_db_holds_zero_lo_residue gate measures it), and the structural teardown assertions probe zero orphan residue inside the dedicated database before it goes.

Row (pg_lo_column.rs)	Traces to
dedup_identical_content_is_one_pool_entry	INV-2 (kv and large legs; counts read against the durable schedule; ADR-009 §2/§4 — the companion table, delete = lo_unlink + row delete)
stage_hygiene_zero_residue_on_failure_exactly_one_entry_on_success	INV-3 (the LO tier's real staged form — the held tx's failure paths roll back to no row, no LO pages; schedule-relative counts; ADR-009 §2)
two_sweep_exact_counts_over_the_full_protection_set	INV-4/INV-5 (the full protection set across two sweeps, both tiers; the window observed on its host — the pg-lo schema for mem-pglo, the kv schema for postgres-pglo; ADR-012 §5)
a_put_landing_during_the_window_survives_the_executing_sweep	INV-4 (the sweep-vs-put race across the window delay; execution-time re-arbitration; ADR-012 §5 — the host rule's shapes)
the_contended_second_sweeper_aborts_as_data_and_the_holder_stages_only	INV-4 (the SweeperLock abort shape — abort before staging; the holder's durable-form completion: stages only)
list_correctness_is_observable_through_durable_schedule_outcomes	INV-5 (exact counts, never list comparison)
lo_windows_read_across_window_boundaries_and_a_short_body_fails_cleanly	INV-1's LO-medium extension (ranged reads across the shipped window edge; EOF clamping incl. the u64::MAX clamp — the C7 trap not inherited; the beyond-length clean failure); store-api.md §Read path; ADR-009 §2/§3 (the companion table as authority; the lo_get windows); ADR-006; ADR-010 §1
routing_is_a_pure_function_of_length_across_put_paths_and_re_puts	ADR-003 §Dispatch policy (purity/no-migration); ADR-009 §2 (the companion table); ADR-012 §5 (the topology); ADR-012 §6.3; ADR-012 §6.7; INV-7 facade-contract row
threshold_boundary_lengths_route_deterministically	ADR-003 §Dispatch policy (at/below/above, tuned + shipped-default thresholds); ADR-009 §2; ADR-012 §6.3
kv_tier_misses_fall_through_to_the_large_tier_per_op	ADR-012 §6.1 (fall-through per op); ADR-012 §6.5 ruling 5 (miss shapes); ADR-006; ADR-009 §2/§3 (the lo_get windows serve the fall-through); ADR-012 §6.3
virgin_store_reads_are_no_ops_on_a_fresh_schema	store-api.md §Error model (virgin-store semantics); ADR-012 §6.5; ADR-009 §2 (the companion-table bootstrap); ADR-012 §5 (the mem-pglo row asserts the window on the pg-lo host — gc_window present-and-empty, gc_pins never)
the_window_lives_on_the_kv_schema_and_the_pg_lo_schema_stays_dormant (postgres-pglo only)	the dormancy row: ADR-012 §5 (the one-window-host rule's kv-host arm — the pg-lo window clauses dormant, no gc_window in the pg-lo schema; the schedule observed on the kv host); ADR-008 §2; ADR-012 §6.7

Column plan

mem is the contract-reference engine (ADR-011 §2): wave 2 lands its column first (the first column binds the Store facade type), and every other engine's rows mirror mem's column — an addition to mem's column propagates as a requirement to all other columns (INV-7). The pg columns (postgres, pg-lo) additionally run the SKIP posture above — the postgres column is the posture's first landed host (server-less runs skip cleanly; its wave-4 acceptance is the green run against the harness server) and the pg-lo column is the second (landed wave 5; its two factories gate on the mem+pg-lo and postgres+pg-lo feature pairs respectively — the first column whose factories need different feature sets — with the column's full run --all-features against the harness server; the fleet-form rows of INV-4 are engine-gated to the postgres column and first run in wave 6).

Current state

The harness is green on five columns (waves 2–5). The mem column is the contract-reference column: the factory binding is the concrete alkblobs::Store facade (see §The factory contract — the binding demonstrator remains in binding.rs), the reference row set is landed (§The reference row set — rows.rs, every row ADR-stamped and traced to the backlog), the column's factories (mem-only, the reference; kv-only(mem) at a column-declared threshold) vend fresh isolated stores with idempotent teardown (mem_column.rs, the structural factory-contract tests included), and mem never skips.

The local column (the suite's first dual-tier column, the dispatch-coverage shape ADR-012 §6.3 names) mirrors the reference INV rows against its kv = mem + large = local factory at a column-declared tuned threshold — the shared matrix and race fixtures cross it, so both tiers' bodies are exercised — and grows the dispatch-coverage rows (pure-function routing with an on-disk placement oracle, fall-through per op, threshold boundaries at both the tuned and the shipped-default threshold) plus the local-specific rows (on-disk stage hygiene exact counts, pread windows, virgin-store no-ops, the both-tiers sweep shape) — §Columns beyond the reference set is the recorded inventory. Its factory instances each track and remove their own temp roots (idempotent teardown, panicking-row-safe; each runner owns its instance so concurrent rows never share roots). mem-only/kv-only modes and the local column never skip, but the local column is feature-gated on mem: the dual_tier_mem_local constructor rides feature mem because mem is the only constructible kv engine until wave 3 (the gate is the kv pairing's, not the local engine's, which is ungated in src/) — the column runs under cargo test --features mem, with the reference row set compiling ungated so it stays type-checked in default builds.

The sqlite column (the suite's first SQL-backed column — the default-build production shape, kv = sqlite + large = local, ADR-007/013 §4) mirrors the form-independent reference rows (INV-1, INV-6, the NoLivenessSources/ProtectFailed abort shapes, and the kv-only rejection row against kv-only(sqlite)) and grows the durable-schedule sweep rows (§The schedule-relative reading for SQL-backed columns — the two-sweep exact counts, the race across the window delay, the holder-stages-only lease shape, list correctness through durable-schedule outcomes, and the schedule-relative INV-2/3 readings) plus the dispatch rows with the placement oracle adapted by medium (both tiers on disk: the sqlite file's rows vs the root's committed files) and the virgin-store row — the recorded inventory is in §Columns beyond the reference set. Its factories declare the column-tuned threshold and the test tuning of the window delay (Duration::ZERO — execute-on-next-sweep), vend a fresh temp site per open (a private directory holding the sqlite file and the local root; idempotent teardown removing the site, panicking-row-safe, each runner owning its instance), and never skip. The column is feature-gated on sqlite — default-on, so the column runs in the default build: every cargo test run exercises it. The sqlite engine's no-tables-yet read tolerance is engine-instrumented (src/sqlite.rs's tests; the constructor-vs-lazy timing design point there), the column's virgin-store row being its facade form.

The postgres column (the suite's first SKIP-posture column — the fleet-capable-kv shape, kv = postgres + large = local, feature postgres default-off, ADR-007/013 §4, landed wave 4) mirrors the form-independent reference rows (INV-1, INV-6, the NoLivenessSources/ProtectFailed abort shapes, and the kv-only rejection row against kv-only(postgres)) and grows the sqlite column's durable-schedule sweep rows plus the dispatch rows with the placement oracle adapted by medium (an independent connection counts the pg schema's blobs rows vs the root's committed files; the column's own rows watch the schedule's gc_window rows) and the virgin-store row — the recorded inventory is in §Columns beyond the reference set. Its factories declare the column-tuned threshold and the test tuning of the window delay (Duration::ZERO — execute-on-next-sweep) and follow the alkstore pg-factory pattern: a fresh engine-owned schema per open() (unique per call, seeded per tag/pid/time — racing opens included), tracked per-instance in the schema registry, teardown DROP SCHEMA IF EXISTS … CASCADE over exactly the minted schemas plus removal of every vended temp root (idempotent, owned, panicking-row-safe; each runner owns its instance). The column skips cleanly server-less under the reachability probe (ALKBLOBS_PG_HOST gating; the remaining settings default to the harness server's values) — a skip is not a failure — and its acceptance is the green run against the harness server (dockerized pglo-poc, postgres:16-alpine, :15432, db blobs, verified live 2026-10-12; the alkstore harness's same server).

The pg-lo column (the suite's second SKIP-posture column — the LO-medium column, feature pg-lo default-off, ADR-009, its two factories gating on the mem+pg-lo and postgres+pg-lo feature pairs — the first column whose factories need different feature sets, landed wave 5) mirrors the form-independent reference rows (INV-1's round-trip family, INV-6's stat-discipline row riding ADR-009's companion-row probe, and the NoLivenessSources/ ProtectFailed abort shapes) and grows the durable-schedule sweep rows (run on both factories — the window observed on its host: the pg-lo schema for the mem-pglo factory per the one-window-host rule's named test topology, the kv schema for the postgres-pglo consolidation shape, which carries the dormancy row), the dispatch rows with the placement oracle adapted to the LO medium (companion rows + pg_largeobject probing for the large tier; the mem kv half in-process, the postgres kv half's blobs rows), the INV-1 extension row (the LO medium's ranged reads across the shipped window edge and the beyond-length clean failure), and the virgin-store rows — the recorded inventory is in §Columns beyond the reference set. No kv-only rejection row mirrors here (no kv-only pg-lo constructor exists; recorded). Connection settings ride the environment (ALKBLOBS_PG_HOST/PORT/USER/PASSWORD/DB — ALKBLOBS_PG_HOST gates; the rest default to the harness server's values) and the runners gate behind the reachability probe — a skip is never a failure — and its acceptance is the green run against the harness server under --all-features (dockerized pglo-poc, verified live 2026-10-12). Its factories declare the column-tuned threshold and the test tuning of the window delay (0 — execute-on-next-sweep) and follow the alkstore pg-factory pattern with the LO-isolation corollary carried in the engine task's recorded shape (the C7 lesson): a fresh dedicated database per open() (unique per call, engine schemas minted inside it, tracked per-instance; drop-guard janitors backing the abandoned paths), teardown reaping the instance's LOs (SELECT loid FROM lo_entries → lo_unlink), dropping exactly the minted schemas, and dropping the database (WITH (FORCE)) — idempotent, panicking-row-safe — so zero LO residue on the shared database is structural (the engine suite's shared_harness_db_holds_zero_lo_residue gate measures it) and the structural teardown assertions probe zero orphan residue inside the dedicated database before it goes.