claude-memory/graph/fixes/rust-reqwest-responsejson-yields-reqwesterror-not-serde-json-27a1f7.md

id	type	title	tags	importance	confidence	created	updated
27a1f728-ec90-469c-a6ab-5644d333322f	fix	Rust: reqwest response.json() yields reqwest::Error, not serde_json::Error	rust reqwest serde error-handling serde_json api	0.5	0.8	2026-02-28T04:58:15.771467+00:00	2026-03-01T22:02:57.289593+00:00

Fix: reqwest JSON Error Type Mismatch

Problem

When using response.json::<T>().await, JSON decode failures produce a reqwest::Error — not a serde_json::Error. This means a custom error variant like:

#[derive(Debug, thiserror::Error)]
enum ApiError {
    #[error("Parse error: {0}")]
    Parse(#[from] serde_json::Error),
    // ...
}

...is unreachable if you only call response.json(). The #[from] impl exists but can never fire.

Fix

Decode manually in two steps so the serde_json::Error is produced directly:

let body = response.text().await.map_err(ApiError::Request)?;
let data = serde_json::from_str::<T>(&body).map_err(ApiError::Parse)?;

Why It Matters

This lets callers distinguish network errors (connection dropped, timeout) from JSON parse errors (malformed response, schema mismatch). With response.json(), both collapse into reqwest::Error and you lose that distinction.

Context

Caught during code review of api/client.rs in SBA Scout Rust rewrite Phase 2.