---
id: review-001-forward-response-fidelity
name: Upstream response decode — vendored JSON, size caps, loud auth errors, error bodies (FWD-07, FWD-08, FWD-10, FWD-12)
status: pending
depends_on: []
scope: moderate
risk: medium
impact: component
level: implementation
tags: [adapters, review-001]
---

## Description

Review 001 findings on `src/adapters/forward.rs`'s response-decode paths
(`forward`, `forward_stream`), minus the SSE parser (its own task):

- **FWD-07**: `content_type.contains("application/json")`
  (`forward.rs:236`) misses `application/vnd.api+json`,
  `application/problem+json`, etc. → vendor JSON decoded as a `Value::Array`
  of one `Number` per byte. No response size limit on any read path
  (`json()/text()/bytes()`) — a hostile upstream controls caller memory.
  `forward_stream` never checks content-type (200 HTML → empty stream, no
  error). Fix: mime-essence matching (`application/.*+json` suffix
  semantics), response size caps on all read paths, and a loud error for
  non-SSE content on a Sub op.
- **FWD-08** (`forward.rs:104-126`, `:87-94`): invalid credential values
  (control characters, typo'd header name) silently drop the header —
  the request goes out unauthenticated and the caller only sees the
  eventual upstream 401. Fail loudly at call time. (No leak risk today —
  nothing is logged; keep it that way.)
- **FWD-10** (`forward.rs:215-227`, `:333-346`): upstream error bodies
  discarded — surfaced message is only `"HTTP {status}: {reason}"`;
  upstream diagnostics never reach the caller and unconsumed bodies
  hinder connection reuse. Surface a bounded error-body echo on the error
  path; keep the `HTTP_<status>` mapping as is (correct).
- **FWD-12**: byte-identical duplicates `value_to_path_segment`/
  `value_to_query` (`:133-151`); `forward`'s `op_type` parameter only
  toggles `ACCEPT` and its `text/` branch would buffer an entire SSE
  stream if a Sub were ever routed here (currently unreachable, inviting
  misuse — remove or make safe); the `unwrap_or_else(|_| "null")` at
  `:197` masks an unreachable serialization failure with a null body;
  `SharedHttpClient::reload` performs two separate `ArcSwap::store` calls.

## Acceptance Criteria

- [ ] `application/vnd.api+json` (and `application/problem+json`) decode as JSON, not byte arrays (test)
- [ ] Response size cap enforced on JSON/text/binary read paths (test)
- [ ] Non-SSE content-type on a Sub op produces a loud error, not an empty stream (test)
- [ ] Invalid credential values fail loudly at call time (test), no credential material logged
- [ ] Upstream 4xx/5xx bodies surface bounded in the error envelope (test)
- [ ] Duplicate `value_to_*` helpers collapsed; `text/` buffering branch removed or safe; reload atomic
- [ ] `forward.rs` COV-01 uncovered regions (binary branch, auth arms, non-2xx mapping, content-type branches) substantially covered
- [ ] `cargo test` and `cargo clippy --all-targets -- -D warnings` pass

## References

- docs/reviews/001-initial-implementation-review.md (Part D, FWD-07, FWD-08, FWD-10, FWD-12; Part I, COV-01)

## Notes

> Agent fills during implementation. Shares forward.rs with
> review-001-forward-url-safety (request side) and
> review-001-sse-parser — sequence those first or coordinate.

## Summary

> Filled on completion.