fix(google-genai): merge consecutive ToolMessages into single turn for parallel function calling#10442
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guoyangzhen (guoyangzhen) wants to merge 1 commit intolangchain-ai:mainfrom
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…r parallel function calling Fixes off-by-one error in convertBaseMessagesToContent where acc.content[acc.content.length] was always undefined, preventing the duplicate-role check from detecting consecutive function messages. When consecutive ToolMessages are detected (parallel function call responses), they are now merged into a single user content entry with multiple functionResponse parts, as required by the Gemini API. Previously, each ToolMessage created a separate user turn, causing the Gemini API to hang indefinitely when processing parallel function call results. Fixes langchain-ai#10342
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Summary
Fixes an off-by-one error in
convertBaseMessagesToContentthat prevents consecutiveToolMessages from being detected and merged. This causes the Gemini API to hang indefinitely when processing parallel function call results.Root Cause
acc.content[acc.content.length]is alwaysundefinedbecause arrays are 0-indexed. The duplicate-role check never fires, so consecutiveToolMessages (which should be merged into a single user turn per Gemini API requirements) silently create separate content entries.Changes
acc.content[acc.content.length]→acc.content[acc.content.length - 1]Test Plan
Added unit tests verifying:
ToolMessages are merged into a single user turnToolMessages are all mergedFixes #10342