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fix(provider): handle delayed tool call names in streamed responses #18623

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fix(provider): handle delayed tool call names in streamed responses #18623

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150 changes: 66 additions & 84 deletions packages/opencode/src/provider/sdk/copilot/chat/openai-compatible-chat-language-model.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -326,9 +326,10 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV2 {
id: string
type: "function"
function: {
name: string
name?: string
arguments: string
}
started: boolean
hasFinished: boolean
}> = []

Expand Down Expand Up @@ -363,6 +364,54 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV2 {
let isActiveReasoning = false
let isActiveText = false
let reasoningOpaque: string | undefined
const sync = (
call: (typeof toolCalls)[number],
ctl: TransformStreamDefaultController<LanguageModelV2StreamPart>,
done = false,
) => {
if (call.function.name == null) {
return
}

if (!call.started) {
ctl.enqueue({
type: "tool-input-start",
id: call.id,
toolName: call.function.name,
})
call.started = true

if (call.function.arguments.length > 0) {
ctl.enqueue({
type: "tool-input-delta",
id: call.id,
delta: call.function.arguments,
})
}
}

if (call.hasFinished) {
return
}

if (!done && !isParsableJson(call.function.arguments)) {
return
}

ctl.enqueue({
type: "tool-input-end",
id: call.id,
})

ctl.enqueue({
type: "tool-call",
toolCallId: call.id ?? generateId(),
toolName: call.function.name,
input: call.function.arguments,
providerMetadata: reasoningOpaque ? { copilot: { reasoningOpaque } } : undefined,
})
call.hasFinished = true
}

return {
stream: response.pipeThrough(
Expand Down Expand Up @@ -524,59 +573,17 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV2 {
})
}

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,
})

toolCalls[index] = {
id: toolCallDelta.id,
type: "function",
function: {
name: toolCallDelta.function.name,
name: toolCallDelta.function?.name || undefined,
arguments: toolCallDelta.function.arguments ?? "",
},
started: false,
hasFinished: false,
}

const toolCall = toolCalls[index]

if (toolCall.function?.name != null && toolCall.function?.arguments != null) {
// send delta if the argument text has already started:
if (toolCall.function.arguments.length > 0) {
controller.enqueue({
type: "tool-input-delta",
id: toolCall.id,
delta: toolCall.function.arguments,
})
}

// check if tool call is complete
// (some providers send the full tool call in one chunk):
if (isParsableJson(toolCall.function.arguments)) {
controller.enqueue({
type: "tool-input-end",
id: toolCall.id,
})

controller.enqueue({
type: "tool-call",
toolCallId: toolCall.id ?? generateId(),
toolName: toolCall.function.name,
input: toolCall.function.arguments,
providerMetadata: reasoningOpaque ? { copilot: { reasoningOpaque } } : undefined,
})
toolCall.hasFinished = true
}
}
sync(toolCalls[index], controller)

continue
}
Expand All @@ -588,37 +595,22 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV2 {
continue
}

if (toolCall.function.name == null && toolCallDelta.function?.name) {
toolCall.function.name = toolCallDelta.function.name
}

if (toolCallDelta.function?.arguments != null) {
toolCall.function!.arguments += toolCallDelta.function?.arguments ?? ""
if (toolCall.started) {
controller.enqueue({
type: "tool-input-delta",
id: toolCall.id,
delta: toolCallDelta.function.arguments ?? "",
})
}
}

// send delta
controller.enqueue({
type: "tool-input-delta",
id: toolCall.id,
delta: toolCallDelta.function.arguments ?? "",
})

// check if tool call is complete
if (
toolCall.function?.name != null &&
toolCall.function?.arguments != null &&
isParsableJson(toolCall.function.arguments)
) {
controller.enqueue({
type: "tool-input-end",
id: toolCall.id,
})

controller.enqueue({
type: "tool-call",
toolCallId: toolCall.id ?? generateId(),
toolName: toolCall.function.name,
input: toolCall.function.arguments,
providerMetadata: reasoningOpaque ? { copilot: { reasoningOpaque } } : undefined,
})
toolCall.hasFinished = true
}
sync(toolCall, controller)
}
}
},
Expand All @@ -639,17 +631,7 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV2 {

// go through all tool calls and send the ones that are not finished
for (const toolCall of toolCalls.filter((toolCall) => !toolCall.hasFinished)) {
controller.enqueue({
type: "tool-input-end",
id: toolCall.id,
})

controller.enqueue({
type: "tool-call",
toolCallId: toolCall.id ?? generateId(),
toolName: toolCall.function.name,
input: toolCall.function.arguments,
})
sync(toolCall, controller, true)
}

const providerMetadata: SharedV2ProviderMetadata = {
Expand Down
57 changes: 57 additions & 0 deletions packages/opencode/test/provider/copilot/copilot-chat-model.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,12 @@ const FIXTURES = {
`data: {"choices":[{"finish_reason":"tool_calls","index":0,"delta":{"content":null,"role":"assistant","tool_calls":[{"function":{"arguments":"{}","name":"read_file"},"id":"call_reasoning_only_2","index":1,"type":"function"}]}}],"created":1769917420,"id":"opaque-only","usage":{"completion_tokens":12,"prompt_tokens":123,"prompt_tokens_details":{"cached_tokens":0},"total_tokens":135,"reasoning_tokens":0},"model":"gemini-3-flash-preview"}`,
`data: [DONE]`,
],

delayedToolName: [
`data: {"choices":[{"index":0,"delta":{"content":null,"role":"assistant","tool_calls":[{"function":{"arguments":"{\\"path\\":\\""},"id":"call_delayed","index":0,"type":"function"}]}}],"created":1769917421,"id":"delayed-name","usage":{"completion_tokens":0,"prompt_tokens":0,"prompt_tokens_details":{"cached_tokens":0},"total_tokens":0,"reasoning_tokens":0},"model":"qwen3-coder"}`,
`data: {"choices":[{"finish_reason":"tool_calls","index":0,"delta":{"content":null,"role":"assistant","tool_calls":[{"function":{"arguments":"/README.md\\"}","name":"read_file"},"index":0,"type":"function"}]}}],"created":1769917421,"id":"delayed-name","usage":{"completion_tokens":12,"prompt_tokens":123,"prompt_tokens_details":{"cached_tokens":0},"total_tokens":135,"reasoning_tokens":0},"model":"qwen3-coder"}`,
`data: [DONE]`,
],
}

function createMockFetch(chunks: string[]) {
Expand Down Expand Up @@ -482,6 +488,57 @@ describe("doStream", () => {
})
})

test("should buffer tool deltas until function name arrives", async () => {
const mockFetch = createMockFetch(FIXTURES.delayedToolName)
const model = createModel(mockFetch)

const { stream } = await model.doStream({
prompt: TEST_PROMPT,
includeRawChunks: false,
})

const parts = await convertReadableStreamToArray(stream)
const errors = parts.filter((part) => part.type === "error")
const tool = parts.filter(
(part) =>
part.type === "tool-input-start" ||
part.type === "tool-input-delta" ||
part.type === "tool-input-end" ||
part.type === "tool-call",
)

expect(errors).toHaveLength(0)
expect(tool).toStrictEqual([
{
type: "tool-input-start",
id: "call_delayed",
toolName: "read_file",
},
{
type: "tool-input-delta",
id: "call_delayed",
delta: '{"path":"/README.md"}',
},
{
type: "tool-input-end",
id: "call_delayed",
},
{
type: "tool-call",
toolCallId: "call_delayed",
toolName: "read_file",
input: '{"path":"/README.md"}',
providerMetadata: undefined,
},
])

const finish = parts.find((part) => part.type === "finish")
expect(finish).toMatchObject({
type: "finish",
finishReason: "tool-calls",
})
})

test("should include response metadata from first chunk", async () => {
const mockFetch = createMockFetch(FIXTURES.basicText)
const model = createModel(mockFetch)
Expand Down
5 changes: 3 additions & 2 deletions packages/opencode/test/session/message-v2.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -699,9 +699,10 @@ describe("session.message-v2.toModelMessage", () => {
expect(MessageV2.toModelMessages(input, model)).toStrictEqual([])
})

test("converts pending/running tool calls to error results to prevent dangling tool_use", () => {
test("converts interrupted pending/running tool calls to error results to prevent dangling tool_use", () => {
const userID = "m-user"
const assistantID = "m-assistant"
const aborted = new MessageV2.AbortedError({ message: "aborted" }).toObject() as MessageV2.Assistant["error"]

const input: MessageV2.WithParts[] = [
{
Expand All @@ -715,7 +716,7 @@ describe("session.message-v2.toModelMessage", () => {
] as MessageV2.Part[],
},
{
info: assistantInfo(assistantID, userID),
info: assistantInfo(assistantID, userID, aborted),
parts: [
{
...basePart(assistantID, "a1"),
Expand Down
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