A gateway can answer a failed generation with HTTP 200 and put the reason
in the body: a top-level `error` object and no `choices`, or
`choices[0].error` beside `finish_reason: "error"` when a generation dies
mid-flight. Both fell through to the empty-content throw, so a dead credit
balance, a data-policy block, a rate limit and a model that is down all
recorded the same hop: status 0, reason "returned empty content", no
excerpt. Nothing on the provider health card told them apart.
Raise the shape a non-2xx reply raises instead, with the gateway's own
message leading and its `error.code` as the status when that code is an
HTTP error status. The chain classifier, the health ledger and the card
then see 402 / 403 / 429 / 503 and treat each of them the way they treat
the same status on the wire. Message and excerpt are bounded and
key-redacted by the same helper the non-2xx path uses, so remote text is
no more trusted here than it is there.
Gated on the gateway tag: api.openai.com signals every failure with a
status, so the pinned tags parse exactly as before, and a genuine empty
reply stays the empty-content throw it was. The local-endpoint provider
had the same hole on its buffered path, its buffered-reply fallback and
its stream, and gets the same treatment. The body classifier learned the
two account-side refusals a gateway words in its own vocabulary rather
than the vendor's.
Replace the CompletionParams { systemPrompt, userPrompt } string pair with a
structured { system, messages[] } request across all five AI clients. One
refactor unlocks three things: provider prompt-caching (Anthropic cache_control
on the stable system prefix, OpenAI/Codex automatic prefix cache, with
cachedInputTokens surfaced for observability), the tool-calling wire surface,
and clean multi-turn.
Each client maps the new shape to its own wire and degrades unsupported
features silently: the local OpenAI-compatible server never receives a tools
field (most reject unknown keys), and prompt-caching is best-effort everywhere.
CompletionResult gains toolCalls, finishReason and cachedInputTokens; the tool
types and per-provider mapping ship now, the tool-use loop does not.
Vision inputs fold into the user turn's content parts via singleUserTurn, with
each provider's pre-existing block ordering preserved. The corrective-retry
paths append to the last user message rather than a flat string. The Coach
keeps assembling one user turn so its snapshot-once and grounding behaviour is
unchanged. No wire schema visible to API consumers changed.
Behaviour is unchanged across every surface; the full suite stays green.
Marc-André Bombeck