glm-5.2
a3cb44968e
Prune the channels spec to reflect the stream-unification resolution (docs/research/stream-unification/findings.md): the channels wire format goes from 9 bytes to 8 bytes, the channels layer no longer carries a stream_type concept, into_sub_streams() is removed, and TTY always uses its 5-byte format (carried transparently in the channels payload). ADR-093 is the umbrella decision (the channels-layer consequence of ADR-092's BiStream handler leaf): every channel is a BiStream, the handler owns its sub-stream multiplexing, the channels layer routes by channel_id only. Amends ADR-071 (8-byte header, no stream_type), ADR-074 (into_sub_streams removed, accept_bi yields BiStream), reverses ADR-077 (TTY always 5-byte), and the channels-facing clauses of ADR-072/073/075/076/080/081. Adds ADR-092 forward-reference note (into_sub_streams preservation subsequently reversed by ADR-093) and the missing ADR-092 cross-reference on ADR-070. Adds OQ-68 (add/strip API shape — built-in vs utility; the contract is decided in ADR-093, the function surface is open; two-way door, low priority, decision-ready when the channels crate's implementation begins). Rewrites the 7 channels spec docs (README, overview, channels-wire, channels-connection, channels-adapter, channel-operations, channel-client) to describe the post-amendment shape as current, with the 8-byte header, the add/strip composition, single accept_bi accessor, BiStream per channel, and TTY-always-5-byte. Touch-up cross-references in hub README, client README, ADR-085, and the OQ-45/47/65 question files (TTY-internal stream_type 3 → STREAM_CTRL_IN; channels 9-byte → 8-byte).
82 lines
4.7 KiB
Markdown
82 lines
4.7 KiB
Markdown
# OQ-65: Should WebSocket Carry the Channels Protocol (Not Just the Call Protocol)?
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- **Origin**: `docs/architecture/crates/http/websocket.md` (ADR-048
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specifies WebSocket carries the native call-protocol session — the
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`EventEnvelope` wire format over a WebSocket text/binary frame
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stream); `docs/architecture/decisions/086-endpoint-types-and-entry-points.md`
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§3 (the web config advertises `alknet/channels` for the
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WebSocket-carrying-channels path — a path ADR-048 does not specify).
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- **Status**: open
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- **Door type**: one-way (this supersedes or extends ADR-048's
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"WebSocket carries the native call-protocol session" decision. If
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WebSocket carries channels, a browser opens one WebSocket and gets
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the full channels substrate — `channel/open`, data-channel ALPNs,
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the relay path through the hub — instead of only the call-protocol
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session. This is a browser-wire-format one-way door: once browsers
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depend on the channels-over-WebSocket framing, changing it is a
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breaking change for every browser client.)
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- **Priority**: medium (the browser story works without this —
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ADR-048's call-protocol-only WebSocket is functional — but
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channels-over-WebSocket makes the browser a first-class channels
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participant, which simplifies the hub relay and the browser's access
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to data-channel ALPNs like TTY and tunnels. The question is whether
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the simplification is worth the one-way-door commitment now, or
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whether the call-protocol-only path suffices until a concrete
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browser-needs-a-data-channel use case arrives.)
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- **Impacts**: Does not block the browser path (ADR-048 works). Would
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simplify the hub relay (one model, not two) and unblock browser
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access to data-channel ALPNs (TTY, tunnels) over a single WebSocket
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if resolved to "WebSocket carries channels."
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- **Resolution**: Not yet decided. The two options:
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**Option A — WebSocket carries call only (ADR-048 unchanged).** The
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browser opens a WebSocket and gets a call-protocol session
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(`EventEnvelope` over WebSocket frames). Data-channel ALPNs (TTY,
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tunnels) are not accessible from the browser — the browser can invoke
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call operations but cannot open a `alknet/tty` channel. A browser
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needing a TTY would use a separate WebSocket per session, each
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carrying the TTY wire format directly (not via `channel/open`).
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Simpler; the browser is a call-protocol client, not a channels
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client.
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**Option B — WebSocket carries channels (extends/supersedes
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ADR-048).** The browser opens a WebSocket and gets a channels
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connection — the 8-byte chunk format (ADR-071, as amended by ADR-093)
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over WebSocket binary frames, with channel 0 as `alknet/call` and
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data channels opened via `channel/open`. The browser is a full
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channels participant: it can open TTY channels, tunnels, etc. through
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the same WebSocket. The hub relay (ADR-079) works unchanged — the
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browser leg is a channels connection, same as a native leg. This is
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the "browser as channels client" path.
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The trade-off: Option B commits to the channels-over-WebSocket
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framing as a browser wire format (one-way door), but makes the
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browser a first-class channels participant and simplifies the hub
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(one relay model, not two). Option A keeps the browser simpler but
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means the browser cannot use data-channel ALPNs over the same
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connection — each data-channel ALPN needs its own WebSocket and its
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own browser-side implementation.
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This question is decision-ready when the first browser-needs-a-
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data-channel use case arrives (e.g., a browser-based terminal that
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needs `alknet/tty` over the hub). Until then, ADR-048's
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call-protocol-only path is the implemented browser path, and the
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web config advertises `alknet/channels` by default (per ADR-086 §3,
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so the hub is ready for Option B if chosen).
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Note: this is distinct from the WebTransport path (deferred per
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ADR-044). WebTransport, when revived, would carry channels natively
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(a WT bidi stream = a channels connection). WebSocket-carrying-
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channels is the WebSocket equivalent — same substrate, different
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transport. If Option B is chosen, the WebSocket-channels framing
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and the WebTransport-channels framing share the channels wire
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format (ADR-071); only the transport differs.
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- **Cross-references**: ADR-048 (WebSocket carries the native
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call-protocol session — the current decision this OQ may supersede
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or extend), ADR-071 (channels wire format — the 8-byte chunk format
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that would ride over WebSocket binary frames, as amended by ADR-093),
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ADR-093 (channels pure channel multiplexing — the umbrella decision),
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ADR-079 (hub relay — unchanged if the browser is a channels client),
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ADR-086 §3 (the web config advertises `alknet/channels` for this
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path), ADR-044 (WebTransport deferred; WebSocket is the v1 browser
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path) |