glm-5.2
69ebe58bab
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.
246 lines
13 KiB
Markdown
246 lines
13 KiB
Markdown
---
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status: draft
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last_updated: 2026-06-29
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---
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# alknet-http — Overview
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The HTTP interface crate: serves inbound HTTP on standard ALPNs and hosts
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the HTTP-backed call-protocol adapters. This document covers the crate's
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two roles, its dependency edges, and the adapter location map. Component
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details are in the sibling documents.
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## What
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`alknet-http` is the HTTP protocol handler for the ALPN-as-service
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architecture. It serves two roles in one crate:
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1. **HTTP server** — a `ProtocolHandler` (`HttpAdapter`) that accepts
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HTTP/2, HTTP/1.1, and HTTP/3 (WebTransport) connections on the
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standard IANA ALPNs (`h2`, `http/1.1`, `h3`). It serves REST APIs, the
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`to_openapi`/`to_mcp` projections of local call-protocol operations,
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the `/healthz` operational endpoint, and the decoy surface for
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stealth mode.
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2. **HTTP client host** — the home of the HTTP-transport-backed call
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adapters: `from_openapi` (import external HTTP APIs as call
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operations, using `reqwest` for outbound calls) and `from_mcp` (import
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remote MCP tools over streamable HTTP, using `reqwest`). The reverse
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projections `to_openapi` (generate an OpenAPI doc from the local
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registry's `External` operations) and `to_mcp` (expose local ops as
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MCP tools over streamable HTTP, using `axum`) also live here.
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Both directions share the same HTTP dependencies (`axum` for serving,
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`reqwest` for calling out), which is why they live in one crate rather
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than being split into a server crate and a client crate. See
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[ADR-039](../../decisions/039-http-server-and-client-host-colocated.md)
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for the full rationale.
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## Why
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The crate's purpose is to be the HTTP interface library for downstream
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crates that need to expose an HTTP interface. A downstream consumer (the
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CLI binary, a hub deployment, a browser-facing service) wires
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`HttpAdapter` into the `HandlerRegistry` for the standard HTTP ALPNs and
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gets a full HTTP surface: REST projection of the call protocol, OpenAPI
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discovery, MCP tool exposure, and WebTransport for browsers.
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The key architectural insight that shapes the crate: **HTTP is both a
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server surface and a client transport for adapters.** The server side
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serves HTTP to external clients (browsers, curl, axios); the client side
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makes outbound HTTP calls to external APIs (OpenAI, Anthropic, vast.ai)
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through the `from_openapi`/`from_mcp` forwarding handlers. Both
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directions share HTTP dependencies and HTTP-specific concerns (TLS,
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headers, streaming, SSE), so they belong in one crate. See
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[ADR-039](../../decisions/039-http-server-and-client-host-colocated.md)
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for the colocation decision.
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## Dependencies
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```
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alknet-http
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├── alknet-core (ProtocolHandler, Connection, AuthContext, IdentityProvider, Capabilities)
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├── alknet-call (OperationAdapter, OperationSpec, Handler, HandlerRegistration,
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│ OperationRegistry, AdapterError, OperationProvenance)
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├── axum (HTTP server — Router, extractors, middleware)
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├── reqwest (HTTP client — from_openapi/from_mcp forwarding)
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├── hyper (HTTP/1.1 + HTTP/2 framing; axum is built on hyper)
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├── wtransport (HTTP/3 + WebTransport — feature-gated behind `h3`)
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└── rmcp (MCP streamable HTTP — feature-gated behind `mcp`)
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```
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### The `alknet-call` dependency (ADR-003 Amendment 1)
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`alknet-http` depends on `alknet-call`. ADR-003's rule is "no handler
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crate depends on another handler crate," but `alknet-call` is both a
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handler (it implements `ProtocolHandler` on `alknet/call`) *and* the
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protocol-foundation crate that `alknet-agent`, `alknet-napi`, and now
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`alknet-http` consume. `alknet-http` depending on `alknet-call` is
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"HTTP uses the call protocol types" (`OperationSpec`, `Handler`,
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`HandlerRegistration`, `OperationAdapter`), not "HTTP depends on SSH."
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See [ADR-003 Amendment 1](../../decisions/003-crate-decomposition.md).
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`alknet-call` stays lean — it has no `reqwest`, no `axum`, no HTTP
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dependencies. The `from_openapi`/`from_mcp` forwarding handlers are
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opaque `Arc<dyn Handler>` from the registry's perspective: constructed by
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`alknet_http::from_openapi()` at registration time, stored in
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`HandlerRegistration`, dispatched by the `CallAdapter` which doesn't
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know `reqwest` is involved.
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## ALPNs
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| ALPN | Handler | Transport | Browser? |
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|------|---------|-----------|----------|
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| `http/1.1` | `HttpAdapter` | HTTP/1.1 over QUIC stream | No |
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| `h2` | `HttpAdapter` | HTTP/2 over QUIC stream | No |
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| `h3` | `HttpAdapter` | HTTP/3 / WebTransport | Yes (X.509 required) |
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These are standard IANA ALPN strings, not `alknet/`-prefixed. Any HTTP
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client connects without knowing about alknet — the TLS handshake
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negotiates `h2` or `http/1.1` normally, and the `HttpAdapter` serves
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HTTP. This is the stealth mapping (ADR-010): clients that don't offer
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alknet ALPNs get the HTTP handler, just like port scanners in stealth
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mode.
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The `HttpAdapter` registers for all three ALPNs (when the corresponding
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features are enabled). The endpoint's `HandlerRegistry` maps each ALPN to
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the same `HttpAdapter` instance; the handler branches on
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`connection.remote_alpn()` to pick the right framing.
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## Adapter Location Map
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The decomposition principle (settled in
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[client-and-adapters.md](../call/client-and-adapters.md)): the adapter
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trait lives where the types live (`alknet-call`); the adapter
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implementations live where their transport dependencies live.
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```
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alknet-call (lean — no HTTP client, no HTTP server)
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├── OperationAdapter trait (the contract — async, ADR-017 §5)
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├── from_call (QUIC — discovers remote ops via call protocol)
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├── from_jsonschema (pure parse — caller fetches the doc, passes it in)
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└── CallClient (outbound connection opener)
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alknet-http (owns HTTP server + HTTP client)
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├── HttpAdapter (axum server — inbound HTTP on h2/http1.1/h3)
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├── from_openapi (parse OpenAPI doc + reqwest forwarding handler)
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├── to_openapi (generate OpenAPI doc from local registry)
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├── from_mcp (feature-gated) (import remote MCP tools over streamable HTTP — reqwest)
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└── to_mcp (feature-gated) (expose local ops as MCP tools over streamable HTTP — axum)
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```
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`alknet-call` never sees the HTTP client. The `from_openapi`/`from_mcp`
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forwarding handlers are opaque `Arc<dyn Handler>` from the registry's
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perspective. `alknet-call` stays lean; `alknet-http` owns both HTTP
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directions.
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## Feature Gates
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```toml
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[features]
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default = ["h2", "http1"] # the non-browser HTTP surface
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h3 = ["dep:wtransport"] # HTTP/3 + WebTransport (browser path; X.509 required)
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mcp = ["dep:rmcp"] # from_mcp / to_mcp (streamable HTTP only — ADR-037)
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```
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- `h2` + `http1` (default): the `axum` + `hyper` HTTP/1.1 + HTTP/2
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server. This is the surface non-browser clients use.
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- `h3`: the `wtransport` (or quinn HTTP/3 extension) dependency. Adds
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the `h3` ALPN handler and the WebTransport streaming path. See
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[webtransport.md](webtransport.md) and
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[ADR-038](../../decisions/038-http3-and-webtransport-as-first-class.md).
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- `mcp`: the `rmcp` dependency with streamable HTTP transport features
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only. Adds `from_mcp`/`to_mcp`. See [http-mcp.md](http-mcp.md) and
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[ADR-037](../../decisions/037-mcp-stdio-transport-exclusion.md).
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A deployment that only needs the REST surface (no browsers, no MCP) uses
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the default features. A browser-facing hub enables `h3`. A deployment
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that wants MCP tool import/export enables `mcp`.
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## The No-Env-Vars Invariant
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The `from_openapi`/`from_mcp` forwarding handlers are the **credential
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injection point** for the no-env-vars architecture. The path (from the
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gap analysis):
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```
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vault → assembly layer → Capabilities → HandlerRegistration.capabilities
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→ OperationContext.capabilities → from_openapi handler reads
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context.capabilities.get("openai") → injects into HTTP Authorization
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header → reqwest request goes out with vault-derived credential
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```
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This makes aisdk's `std::env::var("OPENAI_API_KEY")` reads unreachable —
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the assembly layer never calls `Default::default()` on a provider; it
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constructs them with vault-derived credentials, or routes HTTP calls
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through `from_openapi` operations that carry the credential in
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`Capabilities`.
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**This is a spec-level invariant**: no handler reads outbound
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credentials from any source other than `OperationContext.capabilities`.
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The `from_openapi`/`from_mcp` implementations in `alknet-http` are
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verified against this invariant. See ADR-014 and
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[client-and-adapters.md](../call/client-and-adapters.md).
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## Architecture (component pointers)
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- **[http-server.md](http-server.md)** — the `HttpAdapter` for `h2`/
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`http/1.1`: how axum is run over a QUIC bidirectional stream, Bearer
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auth resolution, the `/healthz` raw route, stealth decoy, and the
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HTTP-to-call dispatch (ADR-036).
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- **[http-adapters.md](http-adapters.md)** — `from_openapi` (parse
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OpenAPI, build forwarding handlers with `reqwest`) and `to_openapi`
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(generate an OpenAPI doc from the registry's `External` operations).
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Error fidelity per ADR-023.
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- **[http-mcp.md](http-mcp.md)** — `from_mcp`/`to_mcp` (feature-gated),
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streamable HTTP only (ADR-037), the rmcp integration.
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- **[webtransport.md](webtransport.md)** — the `h3` ALPN handler,
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WebTransport session/stream handling, the browser streaming path
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(ADR-038).
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## Design Decisions
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| Decision | ADR | Summary |
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|----------|-----|---------|
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| HTTP-to-call operation mapping | [ADR-036](../../decisions/036-http-to-call-operation-mapping.md) | Direct path mapping; `to_openapi` is projection, not router |
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| MCP stdio transport exclusion | [ADR-037](../../decisions/037-mcp-stdio-transport-exclusion.md) | Streamable HTTP only; stdio is not built (RCE vector) |
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| HTTP/3 + WebTransport first-class | [ADR-038](../../decisions/038-http3-and-webtransport-as-first-class.md) | `h3` in scope, not deferred; browser streaming uses QUIC streams |
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| HTTP server + client host colocated | [ADR-039](../../decisions/039-http-server-and-client-host-colocated.md) | One crate for server + adapters (shared HTTP deps, shared mapping) |
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| WebTransport ALPN-stream-proxy | [ADR-040](../../decisions/040-webtransport-alpn-stream-proxy.md) | Browser → WebTransport stream → any ALPN handler (SSH, git, SFTP) via WASM parser |
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| `to_mcp` tool-gateway pattern | [ADR-041](../../decisions/041-mcp-tool-gateway-pattern.md) | 4 fixed gateway tools (search/schema/call/batch), not one tool per operation |
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| `to_openapi` gateway pattern | [ADR-042](../../decisions/042-openapi-gateway-pattern.md) | 5 fixed gateway endpoints (search/schema/call/batch/subscribe); per-caller AccessControl-filtered |
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| `alknet-call` is protocol-foundation | [ADR-003](../../decisions/003-crate-decomposition.md) Am. 1 | `alknet-http` depends on `alknet-call` (types, not peer handler) |
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| Bearer auth via `resolve_from_token` | [ADR-004](../../decisions/004-auth-as-shared-core.md) | HTTP handler credential source + resolution (settled) |
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| Stealth mode = HTTP handler on standard ALPNs | [ADR-010](../../decisions/010-alpn-router-and-endpoint.md) | Decoy for unknown paths (settled) |
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| Adapter-registered ops are `Internal` | [ADR-015](../../decisions/015-privilege-model-and-authority-context.md) | `from_openapi`/`from_mcp` produce `Internal` leaves (settled) |
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| `OperationAdapter` trait is async | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | HTTP adapters implement the async trait (settled) |
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| `to_*` adapters are projections | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | `to_openapi`/`to_mcp` consume the registry, don't produce entries (settled) |
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| Error schema fidelity | [ADR-023](../../decisions/023-operation-error-schemas.md) | `from_openapi` maps HTTP status → `HTTP_<status>` codes; `to_openapi` projects back (settled) |
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| Browsers require X.509 | [ADR-027](../../decisions/027-tls-identity-redesign-acme-rawkey-decoupling.md) | `h3`/WebTransport needs X.509 (settled) |
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| Browsers are not alknet peers | [ADR-034](../../decisions/034-outgoing-only-x509-and-three-peer-roles.md) | Browser over WebTransport/HTTPS = bearer token, no `PeerId` (settled) |
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## Open Questions
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See [open-questions.md](../../open-questions.md) for full details.
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- **OQ-13** (resolved): Operation path format `/{service}/{op}` — the
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HTTP path.
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- **OQ-26** (resolved): `AdapterError` variants — reused by HTTP
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adapters; `#[non_exhaustive]` allows extension.
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- **OQ-37** (resolved): Browsers are not peers; `h3` hub is a
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mixed-fingerprint `PeerEntry`.
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- **OQ-38** (open, scope): WebTransport relay-as-proxy — does the proxy
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live in `alknet-http` or a separate relay crate?
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- **OQ-39** (open): `to_openapi` published-spec versioning — versioning
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strategy for generated OpenAPI specs.
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- **OQ-40** (open): reqwest client config and connection pooling —
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two-way-door config shape.
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## References
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- `docs/research/alknet-http/phase-0-findings.md` — Phase 0 research
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- `docs/research/alknet-call-completion/gap-analysis.md` — adapter
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location map, no-env-vars invariant
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- `/workspace/@alkdev/operations/src/from_openapi.ts`,
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`/workspace/@alkdev/operations/src/from_mcp.ts` — TypeScript prior art
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- `/workspace/rust-sdk/` — MCP Rust SDK (rmcp); streamable HTTP examples
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- `/workspace/wtransport/` — pure-Rust WebTransport reference |