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[v6.0] fix(openai-compatible): buffer tool call deltas until function.name arrives #16836

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gr2m merged 1 commit into from
Jul 6, 2026
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[v6.0] fix(openai-compatible): buffer tool call deltas until function.name arrives #16836

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5 changes: 5 additions & 0 deletions .changeset/breezy-eagles-care.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@ai-sdk/openai-compatible": patch
---

fix(openai-compatible): buffer tool call deltas until function.name arrives
159 changes: 159 additions & 0 deletions packages/openai-compatible/src/chat/openai-compatible-chat-language-model.test.ts
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Expand Up @@ -2217,6 +2217,165 @@ describe('doStream', () => {
`);
});

it('should stream tool deltas when function.name arrives in a later chunk', async () => {
server.urls['https://my.api.com/v1/chat/completions'].response = {
type: 'stream-chunks',
chunks: [
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"role":"assistant","content":null},"finish_reason":null}]}\n\n`,
// First tool_calls delta carries id and (empty) arguments but no function.name
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"id":"call_late","type":"function","function":{"arguments":""}}]},` +
`"finish_reason":null}]}\n\n`,
// function.name arrives in the next chunk together with the start of the arguments
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"id":"call_late","type":"function","function":{"name":"test-tool","arguments":"{\\""}}]},` +
`"finish_reason":null}]}\n\n`,
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"value"}}]},` +
`"finish_reason":null}]}\n\n`,
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\\":\\"hi\\"}"}}]},` +
`"finish_reason":null}]}\n\n`,
`data: {"id":"chatcmpl-late-name","object":"chat.completion.chunk","created":1729171479,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{},"finish_reason":"tool_calls"}],` +
`"usage":{"prompt_tokens":18,"completion_tokens":10,"total_tokens":28}}\n\n`,
'data: [DONE]\n\n',
],
};

const { stream } = await model.doStream({
tools: [
{
type: 'function',
name: 'test-tool',
inputSchema: {
type: 'object',
properties: { value: { type: 'string' } },
required: ['value'],
additionalProperties: false,
$schema: 'http://json-schema.org/draft-07/schema#',
},
},
],
prompt: TEST_PROMPT,
includeRawChunks: false,
});

expect(await convertReadableStreamToArray(stream)).toMatchInlineSnapshot(`
[
{
"type": "stream-start",
"warnings": [],
},
{
"id": "chatcmpl-late-name",
"modelId": "grok-3",
"timestamp": 2024-03-25T09:06:38.000Z,
"type": "response-metadata",
},
{
"id": "call_late",
"toolName": "test-tool",
"type": "tool-input-start",
},
{
"delta": "{"",
"id": "call_late",
"type": "tool-input-delta",
},
{
"delta": "value",
"id": "call_late",
"type": "tool-input-delta",
},
{
"delta": "":"hi"}",
"id": "call_late",
"type": "tool-input-delta",
},
{
"id": "call_late",
"type": "tool-input-end",
},
{
"input": "{"value":"hi"}",
"toolCallId": "call_late",
"toolName": "test-tool",
"type": "tool-call",
},
{
"finishReason": {
"raw": "tool_calls",
"unified": "tool-calls",
},
"providerMetadata": {
"test-provider": {},
},
"type": "finish",
"usage": {
"inputTokens": {
"cacheRead": 0,
"cacheWrite": undefined,
"noCache": 18,
"total": 18,
},
"outputTokens": {
"reasoning": 0,
"text": 10,
"total": 10,
},
"raw": {
"completion_tokens": 10,
"prompt_tokens": 18,
"total_tokens": 28,
},
},
},
]
`);
});

it('should error when streamed tool call never receives a function.name', async () => {
server.urls['https://my.api.com/v1/chat/completions'].response = {
type: 'stream-chunks',
chunks: [
`data: {"id":"chatcmpl-no-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"role":"assistant","content":null},"finish_reason":null}]}\n\n`,
`data: {"id":"chatcmpl-no-name","object":"chat.completion.chunk","created":1711357598,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"id":"call_missing","type":"function","function":{"arguments":"{}"}}]},` +
`"finish_reason":null}]}\n\n`,
`data: {"id":"chatcmpl-no-name","object":"chat.completion.chunk","created":1729171479,"model":"grok-3",` +
`"choices":[{"index":0,"delta":{},"finish_reason":"tool_calls"}],` +
`"usage":{"prompt_tokens":18,"completion_tokens":10,"total_tokens":28}}\n\n`,
'data: [DONE]\n\n',
],
};

const { stream } = await model.doStream({
tools: [
{
type: 'function',
name: 'test-tool',
inputSchema: {
type: 'object',
properties: { value: { type: 'string' } },
additionalProperties: false,
$schema: 'http://json-schema.org/draft-07/schema#',
},
},
],
prompt: TEST_PROMPT,
includeRawChunks: false,
});

await expect(
convertReadableStreamToArray(stream),
).rejects.toThrowErrorMatchingInlineSnapshot(
`[AI_InvalidResponseDataError: Expected 'function.name' to be a string.]`,
);
});

it('should stream tool call with thought signature from extra_content', async () => {
server.urls['https://my.api.com/v1/chat/completions'].response = {
type: 'stream-chunks',
Expand Down
146 changes: 118 additions & 28 deletions packages/openai-compatible/src/chat/openai-compatible-chat-language-model.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -418,6 +418,18 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
thoughtSignature?: string;
}> = [];

// Buffers tool-call deltas by `index` until `function.name` is known.
// Some OpenAI-compatible providers send the first delta without
// `function.name`.
const pendingToolCalls = new Map<
number,
{
id: string | null;
bufferedArguments: string;
thoughtSignature: string | undefined;
}
>();

let finishReason: LanguageModelV3FinishReason = {
unified: 'other',
raw: undefined,
Expand Down Expand Up @@ -553,38 +565,103 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
const index = toolCallDelta.index ?? toolCalls.length;

if (toolCalls[index] == null) {
if (toolCallDelta.id == null) {
throw new InvalidResponseDataError({
data: toolCallDelta,
message: `Expected 'id' to be a string.`,
if (toolCallDelta.index != null) {
// Buffer deltas until `function.name` is known. Some
// OpenAI-compatible providers send the first delta
// without `function.name`.
let pending = pendingToolCalls.get(index);
if (pending == null) {
pending = {
id: toolCallDelta.id ?? null,
bufferedArguments: '',
thoughtSignature:
toolCallDelta.extra_content?.google
?.thought_signature ?? undefined,
};
pendingToolCalls.set(index, pending);
} else {
if (pending.id == null && toolCallDelta.id != null) {
pending.id = toolCallDelta.id;
}
if (
pending.thoughtSignature == null &&
toolCallDelta.extra_content?.google
?.thought_signature != null
) {
pending.thoughtSignature =
toolCallDelta.extra_content.google.thought_signature;
}
}

const argumentsDelta = toolCallDelta.function?.arguments;
if (argumentsDelta != null) {
pending.bufferedArguments += argumentsDelta;
}

const name = toolCallDelta.function?.name;
if (name == null) {
continue; // wait for the delta that carries the name
}

pendingToolCalls.delete(index);

if (pending.id == null) {
throw new InvalidResponseDataError({
data: toolCallDelta,
message: `Expected 'id' to be a string.`,
});
}

controller.enqueue({
type: 'tool-input-start',
id: pending.id,
toolName: name,
});
}

if (toolCallDelta.function?.name == null) {
throw new InvalidResponseDataError({
data: toolCallDelta,
message: `Expected 'function.name' to be a string.`,
toolCalls[index] = {
id: pending.id,
type: 'function',
function: {
name,
arguments: pending.bufferedArguments,
},
hasFinished: false,
thoughtSignature: pending.thoughtSignature,
};
} else {
if (toolCallDelta.id == null) {
throw new InvalidResponseDataError({
data: toolCallDelta,
message: `Expected 'id' to be a string.`,
});
}

if (toolCallDelta.function?.name == null) {
throw new InvalidResponseDataError({
data: toolCallDelta,
message: `Expected 'function.name' to be a string.`,
});
}

controller.enqueue({
type: 'tool-input-start',
id: toolCallDelta.id,
toolName: toolCallDelta.function.name,
});
}

controller.enqueue({
type: 'tool-input-start',
id: toolCallDelta.id,
toolName: toolCallDelta.function.name,
});

toolCalls[index] = {
id: toolCallDelta.id,
type: 'function',
function: {
name: toolCallDelta.function.name,
arguments: toolCallDelta.function.arguments ?? '',
},
hasFinished: false,
thoughtSignature:
toolCallDelta.extra_content?.google?.thought_signature ??
undefined,
};
toolCalls[index] = {
id: toolCallDelta.id,
type: 'function',
function: {
name: toolCallDelta.function.name,
arguments: toolCallDelta.function.arguments ?? '',
},
hasFinished: false,
thoughtSignature:
toolCallDelta.extra_content?.google
?.thought_signature ?? undefined,
};
}

const toolCall = toolCalls[index];

Expand Down Expand Up @@ -636,6 +713,19 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
controller.enqueue({ type: 'text-end', id: 'txt-0' });
}

// Tool-call deltas that never received a `function.name` are
// invalid, preserving the original invalid-response semantics.
for (const [index, pending] of pendingToolCalls) {
throw new InvalidResponseDataError({
data: {
index,
id: pending.id,
function: { arguments: pending.bufferedArguments },
},
message: `Expected 'function.name' to be a string.`,
});
}

// go through all tool calls and send the ones that are not finished
for (const toolCall of toolCalls.filter(
toolCall => !toolCall.hasFinished,
Expand Down
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