Adversarial review of the direct bridge found divergences from the
double-conversion chain it replaces; all are now aligned and covered by
tests that fail against the previous implementation:
- flush argument fragments buffered before a deferred tool announcement,
and announce name-less tools at finalize, so no tool arguments are lost
when upstreams stream arguments before the name
- fold text-only user array content into a single string; parts form only
when an image requires it (strict chat upstreams reject array content)
- drop tool_choice pointing at undeclared tools and unknown choice types
- treat cache_write_tokens/cache_creation_tokens as alternate spellings
(prefer write), not additive
- generate a response id when the upstream omits one
- derive stop_reason from blocks for content_filter/unknown finish reasons
- emit input_json_delta "{}" when a tool block closes without argument
deltas
Skip the Responses API intermediate representation on the /v1/messages
force-chat path. Previously every streaming token ran through two state
machines (CC→Responses→Anthropic); now it runs through one (CC→Anthropic).
New file backend/internal/pkg/apicompat/chatcompletions_anthropic_bridge.go:
- AnthropicToChatCompletionsRequest: request-side direct conversion
- ChatCompletionsResponseToAnthropic: non-stream response direct conversion
- ChatCompletionsChunkToAnthropicEvents + Finalize: single streaming state machine
openai_gateway_messages_chat_fallback.go rewired to use the direct bridge.
Existing 7 ForceChatCompletions end-to-end tests pass unchanged; 22 new
unit tests added including equivalence tests vs the double-conversion path.
WSv2 egress relays upstream events verbatim without the HTTP-path
namespace restore, so flattening requests that take the WSv2 branch
would surface flattened tool names the client cannot match. Resolve
the WS transport decision before flattening and skip flattening only
when the request will actually go WSv2 (passthrough accounts return
via HTTP before the WSv2 branch and still flatten).
Also check all type assertions in responses_namespace_test.go to
satisfy golangci-lint errcheck.
Resolve conflict in openai_gateway_passthrough.go streaming path: keep
main's normalizeCompletedImageGenerationStatus normalization ahead of
this branch's namespace restore block, mirroring the established order
in openai_gateway_response_handling.go.
The snapshot taken before dispatching the OAuth response handler still used
raw c.Writer.Size(), while handleOpenAIImagesOAuthResponseError compares it
against the keepalive-adjusted size. From the second failover round on, the
previous round's heartbeat bytes made the raw snapshot positive while the
adjusted size stayed -1, so a retryable upstream error was misjudged as
'response already written': the failover was swallowed and the client got a
committed 200 with a whitespace-only body.
Snapshot now uses OpenAIImagesJSONKeepaliveAdjustedWrittenSize, matching the
comparison side. Regression test simulates a prior-round heartbeat before
ForwardImages and asserts the retryable error still converts to
UpstreamFailoverError (verified red without the fix, green with it).
shaw