# hive-sock-client

One JSON-line-over-unix-socket client, shared by every daemon that speaks
to a hyperhive socket.

The wire protocol is the same everywhere: connect, write one line of JSON,
read one line of JSON back. Before this crate existed, five daemons each
carried their own copy of that — two of them byte-identical — and the
retry, response-handling and error-context behaviour drifted between them.

The crate is generic over the request and response types, so it is
protocol-agnostic: the host-served control socket and the harness's
in-agent socket both use it, with their own wire-type crates.

## Shapes

- `request` / `request_retried` — write, then decode the response line.
  `request_retried` additionally reports how many retries it took, for
  callers (MCP tool handlers) that want to tell the model a socket flake
  happened so it doesn't retry at the LLM level.
- `notify` — write, half-close, drain the response line and discard it.
  For fire-and-forget ops where the reply carries nothing the caller acts
  on. The drain is not optional: without it the server's write-back lands
  on a closed socket.

## Retry is a policy value, not a fork

`Retry::RideOutRestart` backs off 2/4/8/16/30s (60s total), sized to ride
out a service restart. It is for callers with no natural retry of their
own — a stall there costs a surfaced tool error and the tokens to handle
it.

`Retry::None` fails fast. It is for callers already inside a poll loop,
where the poll interval *is* the retry and a second backoff would only
stack sleeps and delay the rest of the batch.

Two named policies, not a configurable schedule: nobody needs a third yet,
and naming them keeps the *reason* for the choice at the call site.

## Error contract

Errors always name the socket path. That detail is load-bearing: a
permission problem on a socket that reads as "is the daemon running?"
sends the operator to fix the wrong thing.

A refused or missing socket additionally gets a "may be restarting" hint,
and an exhausted retry schedule records how long it tried, so a surfaced
error reads as the likely transient it usually is.

Serialisation and deserialisation failures are never retried — retrying
identical bytes reproduces the same failure. They are raised outside the
retry loop, so only connect/IO/short-read failures ever reach it.