When the Gemini->Anthropic streaming bridge for the /v1/messages endpoint
receives a functionCall part followed by a text part, the text branch in
handleStreamingResponse opened a new text content block without closing the
already-open tool_use block. The tool block's content_block_stop was only
emitted at end-of-stream, after the text block's content_block_start, so the
Anthropic SSE stream contained overlapping/unterminated content blocks. Clients
that assemble messages by block index (e.g. Claude Code) can drop the tool
input or mis-parse the response.
The functionCall branch already closes an open text block before opening a tool
block, and the chat-completions sibling closes the tool block in its text branch
via closeOpenTool(). This applies the same symmetric handling to the messages
variant: close any open tool_use block (resetting openToolIndex/openToolName/
seenToolJSON) before starting text.
Adds a regression test that replays a tool->text Gemini stream and asserts the
Anthropic content-block lifecycle never overlaps.
0a521f09fb