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## Problem
When `buzz-agent` exhausts retries on a stalled LLM call, the error
message reads:
```
transport: error sending request for url (...) (cumulative 721s, 3 attempts)
```
That text is reqwest's generic pre-response failure string — identical
whether the cause is a TLS abort, a reset connection, or a
`read_timeout` fire. An operator reading the log cannot tell whether
something broke or whether the LLM generation legitimately took longer
than the configured timeout.
## Root cause (probe-confirmed)
A live probe against `goose-claude-fable-5` with a 900s client timeout
completed in **370s** — well past the default
`BUZZ_AGENT_LLM_TIMEOUT_SECS=240`. Extended-thinking models emit zero
bytes on non-streaming calls until generation is complete, so reqwest's
`read_timeout` fires on byte-silence regardless of whether the server is
healthy. The 46× exact-721s stall signatures in production logs (3 ×
240s + backoff) are deterministic self-inflicted timeouts, not network
faults.
## Fix
### Pure classifier over `{is_connect, llm_timeout, phase}`
A new `timeout_message(is_connect: bool, llm_timeout: Duration, phase:
TimeoutPhase)` pure function produces factual messages with the
configured duration value embedded verbatim. Two thin wrappers
(`classify_transport_error`, `classify_body_read_error`) extract the
reqwest flags and delegate. The duration reaches the classifiers through
a new `read_timeout: Duration` parameter on `post()` and
`openrouter_post()`; callers pass `cfg.llm_timeout`.
### Messages emitted
| Case | Message |
|---|---|
| Connect-phase timeout (`is_connect && is_timeout`) | `connect timeout:
no connection established within 10s` |
| Transport read-timeout | `read timeout: no response bytes received
within 240s (consider raising BUZZ_AGENT_LLM_TIMEOUT_SECS)` |
| Body-read timeout | `read timeout: no further response bytes received
within 240s (consider raising BUZZ_AGENT_LLM_TIMEOUT_SECS)` |
| Non-timeout | `transport: {reqwest text}` / `body read: {reqwest
text}` (unchanged) |
`LLM_CONNECT_TIMEOUT` is now a named `const` (was inline
`from_secs(10)`).
**Out of scope by explicit decision:** streaming support, changes to
`MAX_RETRIES` or backoff.
## Files changed
- `crates/buzz-agent/src/llm.rs` — `timeout_message` pure fn +
`TimeoutPhase` enum + `LLM_CONNECT_TIMEOUT` const; two classifier
wrappers updated; `post()` and `openrouter_post()` gain `read_timeout`
param; tests replaced.
## Tests
`cargo test -p buzz-agent`: **397 passed, 0 failed** at `294ce5897`.
**Pure-function tests (no network):**
- `timeout_message_connect_true_shows_connect_timeout` —
`is_connect=true` → connect-flavored text with 10s value; both phases
checked
- `timeout_message_transport_phase_shows_read_timeout_and_duration` —
transport phase includes 240s and config knob
- `timeout_message_body_read_phase_says_no_further_bytes_and_duration` —
body phase says "no further", shows 300s
- `timeout_message_duration_is_not_hardcoded` — 600s supplied → 600s in
output, not 240s
**Loopback reqwest integration tests:**
- `classify_transport_error_read_timeout_is_loopback_verified` — TCP
connect succeeds, server sends no bytes; verifies reqwest sets
`is_timeout && !is_connect` and message contains 50ms value
- `classify_transport_error_non_timeout_preserves_reqwest_text` —
controlled accept-then-close on an owned loopback listener → non-timeout
error; asserts exact `transport: {err}` output equality
- `classify_body_read_error_timeout_says_no_further_bytes` — loopback
server sends headers + 4 bytes of a declared-1024-byte body, then holds;
verifies `is_timeout`, "no further", 100ms value, config knob
No test performs egress beyond loopback (`127.0.0.1`). The TEST-NET-3
dial is deleted.
---------
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Co-authored-by: Duncan <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>