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Cover the hosted adapters' failure paths (#18 §E6) - #26

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Cover the hosted adapters' failure paths (#18 §E6)#26
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Stacked on #19#20#21#22#23#24#25. Once those merge this reduces to the single commit Cover the hosted adapters' failure paths.

Summary

Issue #18 §E6 — the bullet reading "backend error, timeout, and partial-page responses on every remote adapter — currently zero coverage."

The three existing per-adapter test files all drive a backend that answers correctly. That is the half that was never in doubt.

Six tests, each running against all three adapters over a real TCP socket, reusing the axum-double harness the happy-path tests already use:

Test What it pins
a_backend_failure_on_write_is_reported_rather_than_swallowed a 500 on write is not reported as success
a_backend_failure_on_read_is_not_reported_as_absence a 500 on read is not laundered into Ok(None)
an_unauthorized_backend_is_not_reported_as_an_empty_store a 401 is not an empty result, on list or recall
a_malformed_backend_response_is_an_error_and_not_a_panic 200 OK + unparseable JSON errors rather than panicking
an_unreachable_backend_is_reported_rather_than_hanging connection-refused surfaces
a_paginated_export_terminates_instead_of_looping export_page terminates

The read case is the one that matters

Ok(None) after a 500 says "this memory does not exist" when the truth is "I could not ask." A caller cannot tell those apart. So it writes the memory again, or tells a user their memory is gone, or — worst — a sync job treats the empty read as authoritative and prunes. Nothing surfaces until much later.

All three adapters already behave correctly

This pins behaviour rather than fixing it, and that is worth saying plainly: six tests passing on the first run is also exactly what a test that never exercises its subject looks like.

So the read assertion additionally requires the backend's status to survive into the error. Without that it would pass just as happily if an adapter had failed on URL construction and never reached the network. Confirmed against the live errors:

supermemory: memory API v3/container-tags/list returned HTTP 500 Internal Server Error
mem0:        memory API memories?top_k=1000 returned HTTP 500 Internal Server Error
cognee:      memory API api/v1/datasets returned HTTP 500 Internal Server Error

Real vendor paths, real status — the tests reach the HTTP layer and discriminate.

What these deliberately do not assert

Which error comes back. The adapters' HTTP layer bail!s into anyhow, so all of these arrive as MemoryError::Other, and "unsupported" is not yet distinguishable from "failed". That is §A4, and conflating it with this change would hide the fact that the distinction does not exist yet.

Two details worth a look in review

  • The unreachable-backend test binds a port, reads its number, then drops the listener — so the address is reliably closed rather than merely unlikely to be in use.
  • The export test is wrapped in a tokio::time::timeout, so a non-terminating implementation fails the test instead of hanging the whole suite. An error from export_page is an acceptable answer there; a hang is not.

Public API / behavior changes

None. Tests only.

Validation

Command Result
cargo fmt --all -- --check pass
cargo clippy --all-targets --all-features -- -D warnings pass
cargo clippy -p tinymemory-tinycortex --all-targets --no-default-features -- -D warnings pass
cargo build --all-targets --all-features pass
cargo test --all-features pass — 1110 passed, 0 failed
RUSTDOCFLAGS="-D warnings" cargo doc --no-deps --all-features pass

Why this matters beyond #18

OPENCOMPANY_MEMORY=remote is gated behind OPENCOMPANY_MEMORY_ALLOW_UNPROVEN_REMOTE in tinyhumansai/opencompany#936, and the reason given there is verbatim "no error mapping, no pagination, no taint preservation." This closes the first two of those three for all three adapters.

It does not yet close acceptance criterion 5 (the conformance suite passes for TinyCortex and all three remote adapters) — #20's suite still runs only against the reference and null drivers. Running assert_provider against these adapters over the same doubles is the natural next step, and needs each double filled out to serve the mandatory families end to end.

Related

Part of #18 (§E6).

`rust_out` and `tmp` are 3.6 MB Linux x86-64 ELF executables with debug info,
committed into a repository developed on macOS. Nothing references either name
in source, config, CI, or docs; both are the output of an ad-hoc build that was
staged by accident, and every clone has carried 7.3 MB of them since.

Ignored with anchored paths so a legitimate `tmp` directory inside a crate is
unaffected.
The workspace declared three different answers: 1.96 at the root and for the
module crate, 1.85 for `core` and both adapters, and nothing at all for `api`.
The low ones were not true — the root facade requires 1.96 and depends on all of
them, so nothing in this workspace builds on 1.85, and no CI job checked the
claim.

Aligning on 1.96 immediately surfaced three lints that the understated MSRV had
been suppressing: clippy only suggests `is_multiple_of` when the declared
minimum supports it. Those are fixed here rather than allowed, since they are a
consequence of this change and not separable from it.

`api/` gaining an explicit MSRV is worth noting for downstream: it is the
dependency-light crate an embedding host binds directly, so it now states a
floor rather than leaving consumers to infer one.
The layout section omitted `tinymemory-core` entirely — the largest crate in the
repository, and the one a real host actually depends on. It also omitted
`crates/tinymemory-module`.

Adds both, and states plainly that `core` is not dependency-light the way `api`
is, since that asymmetry is the thing a reader most needs to know before
choosing which to depend on.

Also documents `git submodule update --init --recursive`. Nothing builds without
it, and because `core` names its engines by path through `vendor/`, an
uninitialized checkout fails at manifest resolution with an error that does not
mention submodules.
`audit_provider` checks that a driver's advertised capabilities match its
reachable accessors — a structural check, proving the shape is honest, not the
behaviour. Nothing checked that two drivers answer the same question the same
way, which is the claim "swap the engine without the host learning anything
new" actually rests on.

`tinymemory-conformance` is that check. `assert_provider` takes any bound
driver and drives the contract: the mandatory three families, upsert on
`(namespace, key)`, namespace isolation, provenance preservation, recall limits
and scoping, export pagination, import round-tripping, and unicode / empty /
64 KiB / control-character content.

It depends on `tinymemory-api` and nothing else of substance. A suite that
pulled in an engine could not prove interchangeability, having already chosen
one; reaching `tinymemory-core` would drag in a bundled SQLite besides.

Ships an in-memory reference driver, for two reasons. A suite that only ever
ran against real engines cannot distinguish "the engine is wrong" from "the
assertion is wrong", and a driver whose behaviour is obvious by inspection
separates those. It also documents the contract by example — the upsert, the
verbatim taint, the cursor that terminates on `None` rather than on an empty
page.

Writing it immediately found a distinction worth naming. The contract permits a
driver that accepts writes and discards them; `NullMemoryProvider` is exactly
that, and the storage assertions are vacuous for it. Rather than weakening each
assertion to tolerate an empty read — which would let a driver that *intends* to
retain and silently does not slip through — the suite probes retention once and
reports which half it ran. The contract-shape assertions are never skipped.

Provenance is the sharp assertion. A driver reading back `Internal` for content
stored as `ExternalSync` has laundered external content into internal-trust
content, and every downstream gate keyed on taint is then silently wrong.

Refs tinyhumansai#18 (§E1)
Issue tinyhumansai#18 §E3. `AGENTS.md` mandates a `tests/` directory exercising only the
public API; the repository had none at the root, and `core/tests/` holds
fixtures with no test files.

Four targets, matching the four §E3 names:

`driver_selection.rs` pins admission: reserved ids resolve to fixed classes, an
external driver with no entry is refused fail-closed, an untrusted external
driver is refused even with one, a reserved id's class cannot be overridden by
config, and a class typo is echoed back so the operator can find the line.

`capability_negotiation.rs` covers both directions of the bind-time
negotiation, including a deliberately lying provider that advertises a summary
tree it has no accessor for — the failure `audit_provider` exists to catch, and
which was previously asserted only in unit tests inside the contract crate.

`taint_end_to_end.rs` drives provenance through store, get, list, recall, and
the export/import round trip, at every driver this workspace ships. It also
pins the fail-closed reading of an unknown persisted value, which is the one
direction that cannot be undone.

`null_provider.rs` asserts the compiled-out configuration is genuinely usable:
every mandatory method answers rather than panicking, it reports Ready rather
than a fault, and no optional family is either advertised or reachable.

Two of the four are deliberately narrower than §E3 describes, and both say so
in their module docs. `driver_selection.rs` cannot yet assert that a bound
provider's `driver_id()` matches configuration, because nothing selects an
engine from config — that is §A5. `taint_end_to_end.rs` cannot drive the sync
path, because sync is welded to the engine until §B. Both are written against
current behaviour, per the sequencing note in the issue, and each names where
its missing leg joins.

Refs tinyhumansai#18 (§E3)
Issue tinyhumansai#18 §C3. The adapter advertised Core, Recall and Portability and nothing
else, which is the reason anything wanting a summary tree, entities, or a diff
ledger reached past the contract to the engine directly — the families existed,
but not through `MemoryProvider`. `crates/tinymemory-module` had grown all of
them, because it needed them and nowhere else had them.

They were never module-specific. Every one delegates to `tinymemory-core` on a
blocking thread, and the two types they hold — `MemoryClient` and the host
config — are core and contract types respectively. So the whole
`ModuleMemoryProvider` moves down to `tinymemory-tinycortex` as
`engine::TinycortexProvider`, and the module crate keeps only the thing that
genuinely is its own: turning a `ModuleConfig` into the engine's runtime
configuration. Its `provider.rs` goes from 2189 lines to 38.

Nineteen family implementations move: documents, ingest, graph, goals,
tool-memory, tree, entities, diff, sources, maintenance, people, chunks,
retrieval, profile, and episodic, alongside the mandatory three.

The diff family gets a `memory-git` feature rather than riding along
unconditionally. It is what drags `git2` / `libgit2-sys` / `libz-sys` — a native
build — into the graph, and this adapter had no such dependency before today;
making it unconditional would hand every consumer a libgit2 build they never
asked for. `cargo tree --no-default-features` confirms none is linked.

The gate reaches `capabilities()`, not just the accessor. A build without
`memory-git` neither advertises nor reaches `Diff`, so `audit_provider` still
passes — which is the whole reason that audit exists. That rule is extracted as
`engine::advertised_capabilities` so it can be tested directly: constructing a
provider needs a `MemoryClient`, which needs the host's process-global seams
installed, and a test that installs a process global is order-dependent.

The new module is `engine`, not `provider`: the crate already has a `provider`
function returning the mandatory-only driver, and both are worth keeping — a
host with no workspace, config, or client still has the lighter one.

Refs tinyhumansai#18 (§C3)
Issue tinyhumansai#18 §A5. The driver registry could answer "is this driver id real, and is
it allowed to answer for memory", and nothing asked it: `DriverRegistry::admit`
had no caller outside its own tests, `MemoryHostConfig::memory_provider()` had
no reader, and the memory client factory constructed TinyCortex unconditionally.
Configuration could not choose an engine.

`DriverRegistry::select` closes that: it reads the engine from the host's
configuration and puts it through `admit`, so both surfaces are now live.

Two corrections to the issue, both load-bearing.

§A5 names `memory_provider()` as the selector. That method is a `provider:model`
routing string for the memory *workload* — which language model does
summarisation and entity extraction — not the store the memory lives in.
Reading it would have let a model change repoint a company's storage. Selection
reads a new `memory_driver()` instead, defaulted to `None` so it breaks no
existing implementation, and a test pins that the two fields stay independent.

§A5 also asks that `create_memory_*` return a bound `Arc<dyn MemoryProvider>`.
It cannot, and the reason is structural rather than unfinished: since §C3
`adapters/tinycortex` depends on `tinymemory-core`, so a core factory returning
a constructed adapter provider is a dependency cycle. Selection therefore
resolves the decision and the host constructs — which is what `src/registry`'s
module docs have said all along: "It resolves the class, not the instance."

A configuration naming no engine gets the reserved embedded default, so adding
selection does not turn "I configured nothing" into a host that fails to start.
Going through `select` does not loosen admission either: an external engine
named in config is still refused without endpoint, credential and trust.

Refs tinyhumansai#18 (§A5)
The `memory-git` feature added alongside the lifted diff family gates that
family, and the test asserting it is *withheld* without the feature is
`#[cfg(not(feature = "memory-git"))]`. Both existing jobs — `--all-features`
and default — compile that test out, so it was checked by nothing: a
feature-gated test whose default fate is to be built by one job and executed
by none.

Adds the configuration as its own step, and asserts the property the feature
exists for: `cargo tree --no-default-features` must link no `git2` or
`libgit2-sys`. A guard rather than a comment, because "this feature keeps the
native build out of the graph" is a claim that silently stops being true the
first time a dependency picks it up transitively.

Verified: `diff_is_withheld_when_the_snapshot_store_is_compiled_out` appears in
`--no-default-features -- --list` and is absent from the `--all-features`
listing, which is what "running nowhere" looked like.

Refs tinyhumansai#18 (§C3, §E2)
Issue tinyhumansai#18 §D4, with §D3 alongside it.

`api/Cargo.toml` spells out a `cargo tree` command in a comment and asks that
the contract crate never link a storage engine, a native library, an HTTP
client, or an async runtime. It was left as a comment, so nothing ran it. A
forbidden dependency does not arrive by someone typing it into the manifest; it
arrives transitively, through a feature enabled two crates away, which is
exactly the way nobody notices.

The forward form is the one that works, and the manifest already explains why:
`cargo tree -i <crate> -p tinymemory-api` discards the `-p` scope, prints the
whole-workspace inverse tree, and exits 0 looking clean even when this crate is
the one at fault. This runs what the comment says to run.

Verified in both directions. The rule holds today — no match against
`rusqlite|libsqlite|git2|reqwest|regex|tokio`. And injecting `regex = "1"` into
the manifest makes the guard fire on `regex`, `regex-automata` and
`regex-syntax`, then reverting makes it pass again. A guard nobody has watched
fail is not yet a guard.

§D3 asks that `--no-default-features` still compile and bind
`NullMemoryProvider`. It does, so this pins it rather than changing anything:
the minimal configuration builds, and tinyhumansai#21's `null_provider` integration test
runs against it — so "usable" is asserted, not just "compiles". That test is
the one that would catch a null driver which panics instead of answering, or
reports a fault instead of `Ready`.

Refs tinyhumansai#18 (§D3, §D4)
Issue tinyhumansai#18 §E6: "backend error, timeout, and partial-page responses on every
remote adapter — currently zero coverage". The three existing per-adapter test
files all drive a backend that answers correctly, which is the half that was
never in doubt.

Six tests, each running against all three adapters over a real TCP socket, using
the axum-double harness the happy-path tests already use:

- a 500 on write is reported rather than swallowed;
- a 500 on read is not laundered into `Ok(None)`;
- a 401 is not presented as an empty store, on either `list` or `recall`;
- a `200 OK` carrying unparseable JSON is an error and not a panic;
- an unreachable backend is reported rather than hanging;
- a paginated export terminates instead of looping.

The read case is the one that matters. `Ok(None)` after a 500 says "this memory
does not exist" when the truth is "I could not ask", and a caller cannot tell
those apart: it writes the memory again, or tells a user their memory is gone,
or a sync job treats the empty read as authoritative and prunes. Nothing
surfaces until much later.

All three adapters already behave correctly — this pins behaviour rather than
fixing it. That is worth stating plainly, because six tests passing on the first
run is exactly what a test that never exercises its subject also looks like. So
the read assertion additionally requires the backend's status to survive into
the error message; without that it would pass just as happily if the adapter had
failed on URL construction and never reached the network. Confirmed against the
live errors: `memory API v3/container-tags/list returned HTTP 500`,
`memory API memories?top_k=1000 returned HTTP 500`, and
`memory API api/v1/datasets returned HTTP 500`.

The assertions are deliberately about whether a failure comes back at all, not
about which error it is. The adapters' HTTP layer `bail!`s into `anyhow`, so
every one of these arrives as `MemoryError::Other` and "unsupported" is not yet
distinguishable from "failed" — that is §A4, and it is not what this change is.

The unreachable-backend test binds a port, reads its number, and drops the
listener, so the address is reliably closed rather than merely unlikely to be in
use. The export test is bounded by a timeout so a non-terminating implementation
fails the test instead of hanging the suite.

Refs tinyhumansai#18 (§E6)
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How this change flows

0 changed behaviours across 4 relationships. 6 surrounding behaviours are shown (60 graph nodes walked). 33 further behaviours left out to keep the diagram readable.

flowchart LR
  n0["MemoryProvider"]:::impacted
  n1["pack_unpack_round_trip"]:::impacted
  n2["MemoryError"]:::impacted
  n3["unpack_embedding"]:::impacted
  n4["other"]:::impacted
  n5["assert_provider"]:::impacted
  n1 -->|calls| n3
  n1 -->|tests| n3
  n4 -->|uses| n2
  n5 -->|uses| n0
  classDef changed fill:#0d4429,stroke:#238636,color:#e6edf3
  classDef impacted fill:#161b22,stroke:#6e7681,color:#c9d1d9
  classDef flagged fill:#5a1e02,stroke:#d93f0b,color:#ffffff
  classDef blocking fill:#67060c,stroke:#f85149,color:#ffffff
Loading

Green: changed behaviour. Grey: surrounding behaviour. Arrows name the call, use, implementation, or test relationship. Orange: has findings. Red: has a finding that blocks the merge.

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tinysweeper found nothing blocking. Approving.

$0.0000 · 0 in / 0 out · 798 embedded · openrouter/openai/text-embedding-3-small

@tinysweeper tinysweeper Bot added the priority: p3 Whenever. Cosmetic, a nicety, or a cleanup with no user visible effect. label Aug 17, 2026

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Reviewed this PR's own commit (21e0a5e). Clean — good tests.

Six failure paths, each iterating all three adapters (Supermemory, Mem0, Cognee) through a shared adapters() helper against an axum double. Hooked in as #[cfg(test)] mod failure_test;, so no feature gate and it runs under any cargo test — I checked, there is nothing here that compiles into a lane and executes in none.

The assertions target the right thing. I looked specifically for whether these would fail if the implementation were wrong, and they would:

  • a_backend_failure_on_read_is_not_reported_as_absence
  • an_unauthorized_backend_is_not_reported_as_an_empty_store

Confusing an error for an empty store is precisely how a remote adapter silently loses data — a host that reads "no memories" instead of "backend rejected your credential" will happily proceed and overwrite. Naming the tests after the confusion rather than after the method is the right instinct.

Bounding the export test with a timeout so a non-terminating implementation fails rather than hangs the suite is also the correct choice; a hang in CI reads as flake and gets re-run.

This takes adapters/remote from 3 tests to 9, which is the crate §E8 named as the first coverage target — worth mentioning in that PR when the coverage number lands.

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