fix(ai): wrap invalid tool call input in JSON object to prevent API rejection

[chatman-media]

Closes #14442

Root cause

In packages/ai/src/generate-text/parse-tool-call.ts, the outer catch block that handles all tool-call parse errors contains:

const parsedInput = await safeParseJSON({ text: toolCall.input });
const input = parsedInput.success ? parsedInput.value : toolCall.input;
//                                                       ^^^^^^^^^^^^^^
//                                              raw string, not a JSON object

When a model emits malformed JSON for a tool call's input and safeParseJSON fails, the raw string is stored as input on the invalid tool-call result. This raw string then flows through to-response-messages.ts and convert-to-language-model-prompt.ts into the assistant message for the next API step. Providers like Amazon Bedrock require toolUse.input to be a JSON object (the Bedrock provider casts input: part.input as JSONObject), so the API rejects the request with:

"The format of the value at messages.X.content.Y.toolUse.input is invalid. Provide a json object for the field and try again."

The model never sees the tool-error result and has no opportunity to retry.

Fix

Wrap the fallback in a valid JSON object so conversation history stays API-valid:

const input = parsedInput.success
  ? parsedInput.value
  : { rawInvalidInput: toolCall.input };

The invalid: true flag and the original error are still surfaced on the tool-call result, so the model can observe the failure and retry.

Tests

• Updated two existing inline snapshot tests that previously asserted "input": "invalid json" (raw string) — they now correctly assert "input": { "rawInvalidInput": "invalid json" }.
• Added a new regression test: 'should wrap unparseable input in a JSON object so API stays valid' — it fails without the fix (raw string returned) and passes with it (wrapped object returned, invalid and error still set).

Verification: pnpm --filter ai test:node src/generate-text/parse-tool-call.test.ts — 22/22 pass with fix, 3/22 fail without it.

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