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docs(http): add ADR-042 OpenAPI gateway pattern for to_openapi

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The to_openapi spec was describing one OpenAPI path per alknet operation
— the inverse of from_openapi. That inverse is genuinely messy: the call
protocol's input is a flat JSON object, and generating a traditional
OpenAPI path entry (POST /fs/{path} with path param, body, query params)
requires reverse-engineering which fields are path/query/body — metadata
the call protocol doesn't carry. The three options (leaky HTTP metadata
on OperationSpec, fragile heuristics, manual annotation) are all messy.

ADR-042 replaces this with the gateway pattern (same as ADR-041 for
to_mcp): to_openapi generates 5 fixed endpoints (search, schema, call,
batch, subscribe) that gate access to the full operation registry. The
input is always a flat JSON body — no path/query/body split to
reverse-engineer. JSON Schema is already in the OperationSpec.

The per-caller API surface is the key advantage: /search is
AccessControl-filtered, so the client sees only what it can call. The
Gitea failure mode (dumping admin ops to every caller in a static
OpenAPI doc) is structurally impossible — the per-caller surface is the
default, not an afterthought. OpenAPI has no per-caller filtering
concept; the gateway pattern provides it through /search.

Gateway endpoint set:
- /search -> services/list (AccessControl-filtered, names + descriptions)
- /schema -> services/schema (full OperationSpec)
- /call -> call.requested (Query/Mutation, flat JSON body)
- /batch -> multiple call.requested (correlated IDs)
- /subscribe -> call.requested (Subscription, SSE) — the one endpoint
  the MCP gateway excludes (MCP is request/response; OpenAPI/SSE
  supports streaming)

A traditional per-operation-paths projection is additive (a deployment
that wants the nice Swagger UI builds it with HTTP-specific metadata),
not a replacement. The gateway is the default.

http-adapters.md to_openapi section rewritten: the gateway endpoint
set, per-caller filtering, error fidelity on the /call endpoint, and
the additive traditional projection. The 'Why' section adds the
flat->structured and per-caller-surface rationale.

README/overview ADR tables and the top-level README current-state note
updated for ADR-042.
This commit is contained in:
glm-5.2
2026-06-29 09:33:39 +00:00
parent 5fc074713c
commit 69ebe58bab
5 changed files with 335 additions and 31 deletions
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@@ -18,7 +18,7 @@ The storage and auth strategy research (`docs/research/alknet-storage-strategy/f
The alknet-call crate is **implemented and reviewed** — both the server-side core and the client/adapter surface (207 lib + 2 integration tests passing). The alknet-core and alknet-call crate specs are in draft; the alknet-vault crate specs are stable.
**alknet-http specs drafted.** The alknet-http crate (HTTP interface — `h2`/`http/1.1`/`h3` server + `from_openapi`/`to_openapi`/`from_mcp`/`to_mcp` adapters) now has architecture specs: [crates/http/](crates/http/) (overview, http-server, http-adapters, http-mcp, webtransport) and six new ADRs — [ADR-036](decisions/036-http-to-call-operation-mapping.md) (HTTP-to-call mapping), [ADR-037](decisions/037-mcp-stdio-transport-exclusion.md) (MCP stdio exclusion), [ADR-038](decisions/038-http3-and-webtransport-as-first-class.md) (HTTP/3 + WebTransport as first-class, correcting the Phase 0 deferral framing), [ADR-039](decisions/039-http-server-and-client-host-colocated.md) (HTTP server + client host colocated in one crate), [ADR-040](decisions/040-webtransport-alpn-stream-proxy.md) (WebTransport ALPN-stream-proxy — browser → WebTransport stream → any ALPN handler via WASM parser; the "VPN-like without being a VPN" use case), [ADR-041](decisions/041-mcp-tool-gateway-pattern.md) (`to_mcp` tool-gateway pattern — 4 fixed gateway tools instead of one tool per operation, addressing LLM context tool-bloat). ADR-003 Amendment 1 clarifies that `alknet-call` is a protocol-foundation crate (the `alknet-http` → `alknet-call` dependency edge). The specs are in draft; implementation has not started. Three open questions carried: OQ-38 (WebTransport standalone relay service scope — distinct from the in-process ALPN-stream-proxy resolved by ADR-040), OQ-39 (`to_openapi` published-spec versioning), OQ-40 (reqwest client config).
**alknet-http specs drafted.** The alknet-http crate (HTTP interface — `h2`/`http/1.1`/`h3` server + `from_openapi`/`to_openapi`/`from_mcp`/`to_mcp` adapters) now has architecture specs: [crates/http/](crates/http/) (overview, http-server, http-adapters, http-mcp, webtransport) and seven new ADRs — [ADR-036](decisions/036-http-to-call-operation-mapping.md) (HTTP-to-call mapping), [ADR-037](decisions/037-mcp-stdio-transport-exclusion.md) (MCP stdio exclusion), [ADR-038](decisions/038-http3-and-webtransport-as-first-class.md) (HTTP/3 + WebTransport as first-class, correcting the Phase 0 deferral framing), [ADR-039](decisions/039-http-server-and-client-host-colocated.md) (HTTP server + client host colocated in one crate), [ADR-040](decisions/040-webtransport-alpn-stream-proxy.md) (WebTransport ALPN-stream-proxy — browser → WebTransport stream → any ALPN handler via WASM parser; the "VPN-like without being a VPN" use case), [ADR-041](decisions/041-mcp-tool-gateway-pattern.md) (`to_mcp` tool-gateway pattern — 4 fixed gateway tools instead of one tool per operation, addressing LLM context tool-bloat), [ADR-042](decisions/042-openapi-gateway-pattern.md) (`to_openapi` gateway pattern — 5 fixed gateway endpoints instead of one path per operation; per-caller AccessControl-filtered API surface). ADR-003 Amendment 1 clarifies that `alknet-call` is a protocol-foundation crate (the `alknet-http` → `alknet-call` dependency edge). The specs are in draft; implementation has not started. Three open questions carried: OQ-38 (WebTransport standalone relay service scope — distinct from the in-process ALPN-stream-proxy resolved by ADR-040), OQ-39 (`to_openapi` published-spec versioning), OQ-40 (reqwest client config).
**Next step**: The storage/repo-pattern ADRs (030–033) are accepted and amend the core and call specs. The next implementation phase is the ADR-029 migration (peer-keyed overlays, `PeerRef` routing, retire `remote_safe`/`trusted_peer`) with the ADR-030 `PeerEntry` change and the ADR-032 `forwarded_for` field folded in — the `OperationContext`, `from_call` handler, and `AuthPolicy` are all under edit, making this the cheapest window. After that: alknet-http implementation (specs drafted, ADRs 036–038 proposed), which consumes the `CredentialStore` trait and the `OperationAdapter` contract. The alknet-ssh crate (the other post-core crate, specced in parallel) proceeds independently — it depends on `alknet-core`, not `alknet-call`.
@@ -94,6 +94,7 @@ The alknet-call crate is **implemented and reviewed** — both the server-side c
| [039](decisions/039-http-server-and-client-host-colocated.md) | HTTP Server and Client Host Colocated in alknet-http | Proposed |
| [040](decisions/040-webtransport-alpn-stream-proxy.md) | WebTransport ALPN-Stream-Proxy | Proposed |
| [041](decisions/041-mcp-tool-gateway-pattern.md) | MCP Tool-Gateway Pattern for to_mcp | Proposed |
| [042](decisions/042-openapi-gateway-pattern.md) | OpenAPI Gateway Pattern for to_openapi | Proposed |
## Open Questions