Backport: fix(google): fix streaming tool call args#15442
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## Background reported in #14358 the official feature docs mention that `willContinue` may be present and marked as false or absent from the terminal chunk of the partial args chunk that comes in. the aisdk assumed that `willContinue` will ALWAYS be present. that guard led to the tool call never actually forming and never executing. ## Summary adjusted the guard settings to properly form the tool call input args - relaxed the guard on terminal chunk ## Manual Verification verified by running the following repro; it doesn't fail before the fix but rather you won't see any tool call object forming neither any tool-result block. after the fix, the model executes it properly <details> <summary>repro:</summary> ```ts import { googleVertex } from '@ai-sdk/google-vertex'; import { isStepCount, streamText, tool } from 'ai'; import { z } from 'zod'; import { run } from '../../lib/run'; run(async () => { const result = streamText({ model: googleVertex('gemini-3-flash-preview'), prompt: 'List 2 fruits with prices. Use writeItems.', tools: { writeItems: tool({ description: 'Write items', inputSchema: z.object({ operations: z.array( z.object({ action: z.enum(['add']), itemid: z.string(), description: z.string(), price: z.number(), }), ), }), execute: async ({ operations }) => { console.log('EXECUTE:', operations.length); return `${operations.length} items`; }, }), }, providerOptions: { vertex: { streamFunctionCallArguments: true, }, }, stopWhen: isStepCount(5), }); for await (const part of result.fullStream) { switch (part.type) { case 'tool-input-start': console.log(`[tool-input-start] ${part.toolName} (${part.id})`); break; case 'tool-input-delta': process.stdout.write(part.delta); break; case 'tool-input-end': console.log(`\n[tool-input-end] (${part.id})`); break; case 'tool-call': console.log(`\n[tool-call] ${part.toolName}:`, part.input); break; case 'tool-result': console.log(`\n[tool-result] ${part.toolName}:`, part.output); break; case 'finish-step': console.log('\n[finish-step]', part.finishReason); break; case 'finish': console.log('[finish]', part.finishReason); break; case 'error': console.error('Error:', part.error); break; } } }); ``` </details> ## Checklist - [x] All commits are signed (PRs with unsigned commits cannot be merged) - [x] Tests have been added / updated (for bug fixes / features) - [ ] Documentation has been added / updated (for bug fixes / features) - [x] A _patch_ changeset for relevant packages has been added (for bug fixes / features - run `pnpm changeset` in the project root) - [x] I have reviewed this pull request (self-review) ## Future Work explore the reproduction if provided from this comment: #14358 (comment) remains a separate bug ## Related Issues fixes #14358
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aayush-kapoor
approved these changes
May 19, 2026
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This is an automated backport of #15438 to the release-v6.0 branch. FYI @aayush-kapoor