Files
glm-5.3-flash f4b5f896b4 docs: sweep em dashes from all markdown prose
Renames the written-usage rule into practice across the contract surface:
docs/ (architecture, research, plans, sdd), tasks/ (all 43 task files,
taskgraph validate passes), AGENTS.md, README.md, CHANGELOG.md, and the
.opencode/agents/ prompts. Every replacement is a sense-preserving
rewrite (colons, semicolons, commas, parentheses, sentence splits, varied),
never a mechanical swap; no spaced hyphens were substituted. Enum fields,
frontmatter, tables, wire data, and cited identifiers survive verbatim;
en dashes inside numeric ranges keep their meaning.

Verification: taskgraph validate (43 tasks), repo grep clean (single
exempt hit: the verification command's own search pattern in AGENTS.md),
cargo test, clippy --all-targets -D warnings, fmt --check, doc all green.
2026-11-04 20:28:00 +00:00

131 lines
6.8 KiB
Markdown

# Vision
Status: Draft (phase 0 research).
## What this is
alkssh is the alk family's SSH adapter: a thin wrapper around russh
terminating the vanilla-ssh wire and bridging to/from alkcall channels
(family ADR-003). It is the alkhttp-style adapter for the SSH protocol, the
vanilla-ssh front door for vanilla clients, and the family's
vanilla-ssh client where a family app dials an upstream SSH server.
The substance almost entirely exists in the family. What alkssh adds is
the glue + the mapping:
- vanilla ssh (ssh(1), git(1), sftp clients) connect to an alkssh
endpoint as they would to any sshd;
- each SSH channel type is mapped onto a family protocol half
(see `mapping-table.md`);
- identity arrives the same way it does everywhere else in the family:
a verified SSH public key's fingerprint resolved through alkcall's
`IdentityProvider` (see `auth-bridge.md`).
The alkforge-relevant property is **exclusion**: an alkforge ssh
endpoint built with only the `git` feature is structurally incapable of
serving a shell, tunnels, or socks. Every mapping is a cargo feature;
unfeatured channel opens decline fail-closed (family ADR-003 decision
3). This is why alkssh leads alkforge's phase 0: the adapter is glue,
not protocol invention.
## Guiding principles
1. **russh owns the SSH wire.** No SSH framing is authored in-family
(family ADR-003 decision 1). KEX, cipher negotiation, channel
multiplexing, and userauth state machines come from russh; third-
party-upstream posture applies (file asks upstream; never silently
absorb a workaround).
2. **A door in both directions, vanilla on the outside.** alkssh is a
door for vanilla clients (server direction: vanilla in, family
out, each channel served by a family seam entry; primary current
purpose: git) and a door to vanilla servers (client direction:
family in, vanilla out; the reverse-runner shape: a family hub
dials vanilla sshd and the ops map family-side onto the same
protocols, **alktty** for sessions, **alktunnels** for
tunnels/-D legs, **alkgit** for upstream git, alkfs client later
for sftp; the runner stays vanilla by design). Type symmetry at
the seam: the family-facing surface speaks family-protocol types
in BOTH directions; the vanilla side speaks russh. The asymmetry
is honest and recorded: the server direction *serves* family seam
entries; the client direction *consumes* family types. It carries
no deployment policy: a downstream app (alkforge) embeds it,
enables features, and brings identity/ACL configuration.
3. **Fail-closed everything.** The feature graph, the auth-method
disposition, and the channel-request disposition all default to a
clean decline. Nothing is advertised that isn't served; nothing is
half-served. Every decline path is contract territory and is
tested.
4. **One seam per mapping.** Each family protocol already exposes a
generic duplex-stream or `Connection` serving entry
(`mapping-table.md`); a russh channel's read/write halves plug in at
exactly one point per mapping. No channel-type knowledge flows
upstream into the protocol crates.
5. **Identity is the family's, not SSH's.** SSH user names, `~/.ssh/`
conventions, and password auth are not the alk family's identity
model. A verified key's fingerprint → `Identity` via alkcall's
`IdentityProvider` is the only resolution path; secrets an alkssh
*client* holds come from alkvault-backed sources: vault-encrypted
at rest, treated as bearer-token-class secret material, never env
vars (family ADR-002 decision 5). The vault is a secret store on
this path, not a key generator or key custodian.
## Non-goals
- **Authoring SSH protocol machinery**: no in-family framing, cipher,
or KEX code, ever (russh upstream decides what SSH is).
- **Being an sshd.** No local user accounts, no `authorized_keys` file
semantics of the OpenSSH variety, no PAM-shaped anything. Deployment
posture belongs to the embedding app.
- **Serving sftp**: deferred to alkfs (family ADR-002); the subsystem
decline is the placeholder contract.
- **A binary / CLI.** Downstream apps embed the crate; there is no
`alkssh` executable in this crate.
- **Password / keyboard-interactive auth for clients.** The family
identity model has no password concept; these methods decline
server-side (see `auth-bridge.md`) and exist client-side only as
non-goals until a consuming use case arrives.
## Scope questions phase 0 must answer
These frame the research docs; each is a candidate open question for
phase 1's `open-questions.md`:
1. **The `alk/ssh` ALPN's topology role**: alkcall ADR-004 reserves
`alk/ssh` → `SshAdapter`, ADR-034's channels table gives it
stream_types `[0, 1]` ("SSH multiplexes internally, including its
own control"), and ADR-009 sketches a browser-WASM route where the
ALPN transports an SSH stream to an `SshAdapter`. But family ADR-003
describes alkssh terminating vanilla SSH at an edge. It remains
unresolved whether `alk/ssh` carries raw vanilla-SSH bytes between
alkssh instances (a relay leg), serves the browser route, or both,
and how that interacts with ADR-042's "the hub never runs a handler
for `alk/ssh`" relay ruling (see `mapping-table.md` §topology).
2. **russh pin**: version, crypto-backend feature, and the
RC-pinned transitive dependency situation (see `russh.md`).
3. **Feature names + graph**: the `session`/`tunnel`/`dynamic-forward`/`git`/`sftp` naming and their independence
(no feature implies another; flat until architecture says otherwise).
4. **Auth dispositions**: which russh auth methods the server
implements vs declines; the exact `auth_publickey` → fingerprint →
identity contract; client-side vault-backed at-rest key handling
(see `auth-bridge.md`).
5. **The mapping table details**: per channel type and per request,
the family seam, the parameter mapping, and the decline contract
(see `mapping-table.md`); POC validation per `pocs.md`.
Resolution status (post-POC): question 4 is answered by
POC-1/POC-2 evidence, question 5 by POC-3 (three mapping-row
corrections recorded), and question 2's *facts* are verified (the pin
decision itself is phase 1 ADR territory). Questions 1 (the `alk/ssh`
topology) and 3 (feature naming) are phase 1 decisions, carried as
seeded OQs / ADR territory per `pocs.md` §Sequencing and gates. A
client-direction consumer pattern (hub-dials-runner) is extracted in
`reverse-runner.md` and shapes the phase 1 client surface.
## References
- family ADR-003 (`/workspace/@alkdev/alkfamily/docs/architecture/decisions/003-alkssh-russh-adapter.md`)
- family ADR-002 (alkforge; why the exclusion property matters)
- family open-questions OQ-08 (partially resolved; remaining scope is
this repo's phase 0)
- `russh.md`, `auth-bridge.md`, `mapping-table.md`, `pocs.md` in this
directory