# `ALLM.Providers.Support.Transport`
[🔗](https://github.com/cykod/ALLM/blob/v0.6.1/lib/allm/providers/support/transport.ex#L1)

Shared HTTP-transport option handling and `Finch` async plumbing for the
streaming provider adapters.

Streaming adapters open their request with `Finch.async_request/3` and
forward a small set of transport opts verbatim (see
`ALLM.Adapter.transport_opts/0` for the full neutral list, which also
covers the non-streaming `Req` path).

## Why this module exists

Finch's HTTP/1 pool defaults `:receive_timeout` to **15,000 ms**
(`Finch.HTTP1.Pool`), and that timer covers the gap before the *first*
byte of the response body. Reasoning models (`gpt-5.x`, extended-thinking
Claude) routinely spend longer than that thinking before the first SSE
chunk is emitted, so the transport killed the request mid-think and the
adapter reported `%AdapterError{reason: :network_error}` — a misleading
error for what is really "the model is still working".

Worse, ALLM's own inter-event timer (`opts[:stream_timeout]`, default
60,000 ms) could never fire: the 15 s transport timer always won the race,
so raising `:stream_timeout` alone had no effect.

`finch_opts/2` fixes both halves: `:stream_timeout` becomes the single
governing knob, and the transport timer is defaulted *above* it (by 30,000
ms of headroom) so it is a backstop rather than the primary timer. An
explicit `opts[:receive_timeout]` still wins.

# `finch_forwarded_opts`

```elixir
@spec finch_forwarded_opts() :: [atom()]
```

The opts forwarded verbatim to `Finch.async_request/3`.

# `finch_opts`

```elixir
@spec finch_opts(
  keyword(),
  timeout()
) :: keyword()
```

Build the extra-opts keyword forwarded to `Finch.async_request/3`.

Takes the resolved adapter `opts` and the already-resolved
`stream_timeout` (the value the adapter passes to its `receive ... after`
clause). Returns the subset of `opts` Finch understands, with
`:receive_timeout` defaulted to
`stream_timeout + 30000` when the caller did not
set it explicitly.

A `stream_timeout` of `:infinity` yields `receive_timeout: :infinity`.

## Examples

    iex> ALLM.Providers.Support.Transport.finch_opts([], 60_000)
    [receive_timeout: 90_000]

    iex> ALLM.Providers.Support.Transport.finch_opts([receive_timeout: 5_000], 60_000)
    [receive_timeout: 5_000]

    iex> ALLM.Providers.Support.Transport.finch_opts([], :infinity)
    [receive_timeout: :infinity]

---

*Consult [api-reference.md](api-reference.md) for complete listing*