fix(sdk-rust): classify an undecodable registration response as InvalidResponse - #446
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…idResponse
Agent registration in AgentWorkforce/relay's PR proof gate failed like this,
three times identically, blocking every runtime PR:
register transport error: HTTP error: error decoding response body
That is reqwest's message for a response that ARRIVED and could not be
parsed. It is not a transport failure. The catch-all in
register_agent_token collapsed every unclassified RelayError into
Transport with `error.to_string()`, which:
- misnamed a server fault as a network one
- discarded the URL, the status, and the decode cause underneath the
outermost message — leaving nothing to diagnose with
- made registration_is_retryable() say yes, so it was retried as though a
retry could help
The last point is the dangerous one. An undecodable response to a
registration may be a response to a registration that COMMITTED. Retrying
it risks a second registration, not recovery from a blip.
Add AgentRegistrationError::InvalidResponse, carrying status, URL, and the
full source chain. Classify into it when the reqwest error is a decode
failure, when the body was JSON that did not match the schema, or when the
SDK already knew the response was invalid. It is not retryable.
Genuine transport failures keep their classification and stay retryable:
this narrows what counts as transport, it does not stop retrying real
network faults. A test pins that.
Downstream: relay's broker matches this enum with wildcard arms throughout
and delegates retryability to registration_is_retryable(), so it inherits
the change without modification.
What this does not do: establish what the server actually sent. Codex
reviewed the response paths on POST /v1/agents and found no intentional
non-JSON path; the Cloudflare entrypoint rethrowing unclassified engine
exceptions is a plausible but unconfirmed boundary. The next failure will
now name the status, URL and cause, which is what settles it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Session-Id: d458bd97-53d8-4f02-be9c-48b67b93c916
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe registration flow now classifies all HTTP errors, including decode errors, as retryable ChangesRegistration error handling
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✅ Passed checks (4 passed)
Full details: Title checkExplanation The title is misleading because the finalized changes keep reqwest decode errors classified as retryable Transport errors. The PR classifies schema-invalid and known invalid responses as InvalidResponse.
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Devin Review found 1 potential issue.
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| #[error( | ||
| "registration for '{agent_name}' got a response it could not understand{}: {detail}", | ||
| status.map(|code| format!(" ({code})")).unwrap_or_default() | ||
| )] |
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🟡 Invalid-response messages omit the endpoint
When InvalidResponse contains a URL, its rendered message drops it. format_registration_error therefore cannot identify which endpoint returned the unusable response.
Learn more
The new variant stores the response URL, but its thiserror format expression never references url. Callers commonly use Display directly or through format_registration_error, so retaining the field does not put it in their diagnostic message.
Example: An error with status: Some(503) and url: Some("https://cast.agentrelay.com/v1/agents") renders the status and cause but omits https://cast.agentrelay.com/v1/agents.
Recommended fix: Add the optional url to the InvalidResponse display expression and extend the_message_names_status_and_cause to assert that the rendered message contains the endpoint.
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Actionable comments posted: 1
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Inline comments:
In `@packages/sdk-rust/src/registration.rs`:
- Around line 138-140: Update the InvalidResponse display formatting used by
format_registration_error to include the response URL, rendering it as an “at
{url}” suffix after the optional status and before the detail. Extend
the_message_names_status_and_cause to assert that the URL appears in the
formatted message.
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packages/sdk-rust/src/registration.rs
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Review found the first revision's classification was inverted for the very
error that motivated it.
Bugbot: in reqwest 0.12, `is_decode()` is true for `bytes()` failures, not
only parse errors. This client reads every body with `bytes()` and parses
afterwards with serde_json, so a decode-kind reqwest error here can ONLY
mean the body was never fully read — a reset or timeout after headers. That
is the exchange failing. Routing it to InvalidResponse and refusing to retry
would have made every mid-body reset permanent. It stays Transport and
retryable, now carrying URL, status and the source chain in its detail so
the log names what it was talking to.
The genuine "server answered unusably" case is `RelayError::Json`: a
success status whose body did not parse. That one is InvalidResponse and
not retryable, as before. And a non-JSON body on an error status already
surfaces as `Api { code: "invalid_response_body", status }` with its status
intact, so it was never in this path.
This also sharpens the original diagnosis. "HTTP error: error decoding
response body" three times running means the body never fully arrived
three times — the server or edge closing the connection after headers —
rather than the server sending something unparseable.
Devin and CodeRabbit: InvalidResponse stored the URL and did not render it,
so format_registration_error could not say which endpoint answered. It is
in the Display now, and the test asserts it.
Tests use real reqwest errors from a refused connection rather than
constructed ones, because reqwest::Error is not constructible directly and
the point is the classification of what reqwest actually produces.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Session-Id: d458bd97-53d8-4f02-be9c-48b67b93c916
|
All three findings were correct. Fixed in 0fe4150 — and Bugbot's was more than a leak; it showed my classification was inverted for the very error that motivated this PR. Bugbot —
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1 participant
The failure
AgentWorkforce/relay's PR proof gate fails in
prove-base, three times identically, blocking every runtime-touching PR there:That is reqwest's message for a response that arrived and could not be parsed. It is not a transport failure — the exchange completed. The server answered with something the client couldn't understand.
Why the message was useless and the retry was wrong
register_agent_token's catch-all collapsed every unclassifiedRelayErrorintoTransportviaerror.to_string():Three consequences:
registration_is_retryable()said yes, because everythingTransportis retryable — so it was retried as though a retry could help.The third is the dangerous one. An undecodable response to a registration may be a response to a registration that committed. Retrying it risks a second registration, not recovery from a blip.
The change
A new
AgentRegistrationError::InvalidResponse { status, url, detail }, wheredetailcarries the full source chain. Classified into it when:is_decode()RelayError::Json)RelayError::InvalidResponse)It is not retryable.
Genuine transport failures keep their classification and stay retryable — this narrows what counts as transport, it does not stop retrying real network faults. A test pins that specifically.
Downstream
relay's broker aliases this enum (
pub type RelaycastRegistrationError = AgentRegistrationError), matches it with wildcard arms in every site, and delegates retryability toregistration_is_retryable(). It inherits the change on its next SDK bump with no code change. Verified by reading each match.What this does not do
It does not establish what the server actually sent. A codex review of every response path on
POST /v1/agentsin relaycast-cloud found no intentional non-JSON path — the Cloudflare entrypoint rethrowing unclassified engine exceptions (entrypoints/cloudflare.ts:164) is a plausible boundary, unconfirmed. A decode error also permits valid JSON with an incompatible schema, so "HTML error page" was an assumption.The point of this PR is that the next failure names the status, URL, and cause. That's what settles it.
58 tests pass, clippy clean, 4 new tests.
🤖 Generated with Claude Code
Note
Medium Risk
Changes registration error taxonomy and retry behavior at agent signup; wrong classification could either duplicate registrations or stop retrying transient network faults, though tests explicitly guard the reqwest-vs-JSON split.
Overview
Registration failures no longer lump every unhandled
RelayErrorintoTransport, which mislabeled completed-but-unparseable HTTP responses as network faults and letregistration_is_retryableretry them.The PR adds
AgentRegistrationError::InvalidResponse(optional status, URL, and a full error source chain indetail) for cases where the server replied but the client could not use the body—RelayError::JsonandRelayError::InvalidResponse. Those outcomes are not retryable, because the registration may already have committed and a retry could register twice.classify_registration_failureroutes remaining failures explicitly:RelayError::Http(including reqwest “decode” errors frombytes()read failures mid-body) staysTransportand retryable, but transportdetailnow includes status, URL, and nested causes viadescribe_with_sources.register_agent_tokenuses this classifier instead oferror.to_string()on the catch-all arm.A dedicated test module locks in classification, retry policy, and richer error messages.
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