The patch API client has no request timeout, so scan, get and apply hang forever on a stalled server #570

[agent] Filed by the scheduled architecture audit routine (CLI and core). Register: discussion #560 register.

Kind: bug. Source: §1 #2; Part 7.2; register C02.

Problem

Both reqwest clients in ApiClient are built with no timeout and no connect_timeout:

• ApiClient::new: api/client.rs#L393-L396
• plain_client(): api/client.rs#L1912-L1922

None of these paths add a per-request bound:

• the JSON retry loop send_json_request (#L475-L551), used by fetch_patch, the batch search and org resolution;
• fetch_binary for blobs and diffs (#L1061-L1120).

The retry loop retries on status codes only, and a stalled connection never produces one.

Every other HTTP path in the crate is bounded, so the rule exists but is applied per call site:

• the vendoring service: .timeout(self.vendor_retry.attempt_timeout) at #L1512-L1530, and tokio::time::timeout at #L1635;
• telemetry: 2 s connect and 5 s total (telemetry.rs#L296-L298);
• self-update (update/download.rs#L65-L68, update/release.rs#L266-L269);
• the registry and Maven fetches (60 s).

Reproduced twice on main @ 1169ae6 with an integration test against ApiClient (not committed). The local TCP server accepts the connection, reads the request and never answers. Both fetch_blob(<hash>) and fetch_patch(<uuid>) were still pending when the test's 120 s outer guard fired, on both runs.

Symptoms

None filed. Several ci-janitor flake PRs (#419, #448, #565) handle API blips in tests, but a stall in production has no bound at all.

Impact

scan, get, apply (blob/diff fetch) and vex can hang a CI job until the job-level timeout on a stalled proxy, load balancer or half-open connection. This is P1 and the fix is small.

Proposed change

• Give both clients a connect_timeout (e.g. 10 s) and a read/idle bound: reqwest's read_timeout, or a per-attempt timeout sized for the request kind. Keep blob/diff bodies on a longer bound than JSON.
• Make the bound one named policy beside ApiRetryPolicy in api/retry.rs, overridable the same way. A stalled attempt then surfaces as ApiError::Network, which the existing proxy fallback already handles.
• Out of scope here: adding retry to fetch_binary and merging the three retry systems (C15, a separate refactor).

Size and scope

api/client.rs and api/retry.rs, ~30–60 production lines plus tests.

Acceptance criteria

• Regression tests: a server that accepts and never responds makes fetch_patch, the batch search and fetch_blob each return ApiError::Network within the configured bound, using a short test override rather than real minutes.
• The timeout values are named constants in one place and documented in CLI_CONTRACT.md if an env override is added.
• api_retry_e2e, binary_fetch_error_classification_e2e and blob_fetcher_edges_e2e stay green.

Dependencies

Blocks nothing. Related to C15 (one retry + timeout primitive) and to #571 (the uncapped blob/diff body in the same fetch_binary).