feat(cpp): SSE streaming response support for C++ agent framework#518
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feat(cpp): SSE streaming response support for C++ agent framework#518
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Add token-by-token streaming through the full stack: - SseParser: stateful parser for OpenAI SSE responses (data: lines, [DONE] sentinel, chunked delivery, CRLF handling, malformed JSON safety) - LemonadeClient::chatCompletionsStreaming: streaming POST via httplib cli.send() with ContentReceiverWithProgress; falls back gracefully when server ignores stream:true; validates HTTP status on early Canceled exit to catch reverse-proxy errors - LemonadeClient::httpPostStreaming: low-level streaming HTTP helper - OutputHandler::printStreamToken / printStreamEnd: virtual no-op defaults; TerminalConsole and CleanConsole flush tokens immediately - Agent::callLlm: branches on config_.streaming; accumulates tokens via callback, falls back to non-streaming JSON parse if no tokens received - Agent::processQuery: skips progress spinners and duplicate printThought/printGoal/printFinalAnswer output when streaming - AgentConfig::streaming: defaults to GAIA_STREAMING env var (=1 to enable without recompiling) - 245 unit tests; 18 new SseParser tests covering all edge cases Closes #360
This was referenced Mar 16, 2026
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- Add /EHsc to CMake for MSVC builds (C++ tests crashed without exception unwinding) - Add USERPROFILE env var to MCP config tests (Path.home() uses USERPROFILE on Windows) - Skip signal name tests on Windows (SIGKILL/SIGSEGV not available)
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Closes #360
Summary
sse_parser.h/cpp): stateful SSE line parser that handles chunked delivery, CRLF,[DONE]sentinel, malformed JSON, and role-only chunks without crashinglemonade_client.cpp):httpPostStreaminguses httplib'scli.send()API withContentReceiverWithProgress;chatCompletionsStreamingwires SSE parser to caller callback, falls back to non-streaming JSON parse if server ignoresstream:true, validates HTTP status even onError::Canceledearly exitconsole.h/cpp,clean_console.h/cpp):printStreamTokenflushes each token immediately;printStreamEndemits trailing newline;SilentConsoleinherits default no-opsagent.cpp):callLlmbranches onconfig_.streaming;processQuerysuppresses progress spinners and duplicate print calls (thought/goal/finalAnswer) that were already streamed liveGAIA_STREAMING=1env var: enables streaming without recompiling, following the same pattern asLEMONADE_BASE_URLSseParsertests covering all edge cases; streaming tests added to console and types suitesTest plan
cmake -B build -DGAIA_BUILD_TESTS=ON && cmake --build build && ctest --test-dir build— all tests pass (245 total; 1 pre-existing failure due toLEMONADE_BASE_URLenv var in CI)GAIA_STREAMING=1 ./build/my_agent— tokens stream to terminal word-by-wordconfig_.streaming = false(default) — behavior identical to pre-PR baselinestream:true— fallback returns correct response🤖 Generated with Claude Code