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fix(openrouter): Capture reasoning #1944

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54567d0
fix(openrouter): Capture reasoning
lforst May 4, 2026
f6a15d7
cs
lforst May 4, 2026
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5 changes: 5 additions & 0 deletions .changeset/clear-jeans-drive.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"braintrust": patch
---

fix(openrouter): Capture reasoning
48 changes: 48 additions & 0 deletions e2e/scenarios/openrouter-instrumentation/assertions.ts
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Expand Up @@ -13,6 +13,7 @@ import {
CHAT_MODEL,
EMBEDDING_MODEL,
RERANK_MODEL,
REASONING_MODEL,
ROOT_NAME,
SCENARIO_NAME,
} from "./constants.mjs";
Expand All @@ -21,7 +22,10 @@ const CHAT_MODEL_NAME = CHAT_MODEL.split("/").at(-1) ?? CHAT_MODEL;
const EMBEDDING_MODEL_NAME =
EMBEDDING_MODEL.split("/").at(-1) ?? EMBEDDING_MODEL;
const RERANK_MODEL_NAME = RERANK_MODEL.split("/").at(-1) ?? RERANK_MODEL;
const REASONING_MODEL_NAME =
REASONING_MODEL.split("/").at(-1) ?? REASONING_MODEL;
const OPENROUTER_MODEL_PROVIDER = "openai";
const OPENROUTER_REASONING_PROVIDER = "deepseek";
const OPENROUTER_RERANK_PROVIDER = "cohere";

type RunOpenRouterScenario = (harness: {
Expand Down Expand Up @@ -216,6 +220,50 @@ export function defineOpenRouterTraceAssertions(options: {
},
);

test(
"captures reasoning fields for a streamed reasoning chat completion",
testConfig,
() => {
const root = findLatestSpan(events, ROOT_NAME);
const operation = findLatestSpan(
events,
"openrouter-chat-reasoning-stream-operation",
);
const span = findOpenRouterSpan(events, operation?.span.id, [
"openrouter.chat.send",
]);
const output = span?.output as
| Array<{
message?: {
reasoning?: string;
reasoning_content?: string;
reasoning_details?: unknown[];
};
}>
| undefined;
const message = output?.[0]?.message;
const reasoning = message?.reasoning ?? message?.reasoning_content;
const hasReasoningText =
typeof reasoning === "string" && reasoning.length > 0;
const hasReasoningDetails =
Array.isArray(message?.reasoning_details) &&
message.reasoning_details.length > 0;

expect(operation).toBeDefined();
expect(span).toBeDefined();
expect(operation?.span.parentIds).toEqual([root?.span.id ?? ""]);
expect(span?.row.metadata).toMatchObject({
provider: OPENROUTER_REASONING_PROVIDER,
});
expect(span?.row.metadata?.model).toBe(REASONING_MODEL_NAME);
expect(span?.metrics?.time_to_first_token).toEqual(expect.any(Number));
expect(span?.metrics?.completion_reasoning_tokens).toEqual(
expect.any(Number),
);
expect(hasReasoningText || hasReasoningDetails).toBe(true);
},
);

test("captures trace for client.embeddings.generate()", testConfig, () => {
const root = findLatestSpan(events, ROOT_NAME);
const operation = findLatestSpan(
Expand Down
10 changes: 9 additions & 1 deletion e2e/scenarios/openrouter-instrumentation/constants.mjs
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@@ -1,7 +1,15 @@
const CHAT_MODEL = "openai/gpt-4o-mini-2024-07-18";
const EMBEDDING_MODEL = "openai/text-embedding-3-small";
const RERANK_MODEL = "cohere/rerank-v3.5";
const REASONING_MODEL = "deepseek/deepseek-r1";
const ROOT_NAME = "openrouter-root";
const SCENARIO_NAME = "openrouter-instrumentation";

export { CHAT_MODEL, EMBEDDING_MODEL, RERANK_MODEL, ROOT_NAME, SCENARIO_NAME };
export {
CHAT_MODEL,
EMBEDDING_MODEL,
RERANK_MODEL,
REASONING_MODEL,
ROOT_NAME,
SCENARIO_NAME,
};
31 changes: 31 additions & 0 deletions e2e/scenarios/openrouter-instrumentation/scenario.impl.mjs
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Expand Up @@ -9,6 +9,7 @@ import {
CHAT_MODEL,
EMBEDDING_MODEL,
RERANK_MODEL,
REASONING_MODEL,
ROOT_NAME,
SCENARIO_NAME,
} from "./constants.mjs";
Expand Down Expand Up @@ -90,6 +91,36 @@ async function runOpenRouterInstrumentationScenario(
},
);

await runOperation(
"openrouter-chat-reasoning-stream-operation",
"chat-reasoning-stream",
async () => {
const stream = await client.chat.send(
withCompatibleChatRequest({
model: REASONING_MODEL,
messages: [
{
role: "user",
content:
"Think briefly, then answer with exactly the number 4.",
},
],
maxTokens: 256,
reasoning: {
enabled: true,
exclude: false,
},
stream: true,
streamOptions: {
includeUsage: true,
},
temperature: 0,
}),
);
await collectAsync(stream);
},
);

await runOperation(
"openrouter-embeddings-operation",
"embeddings",
Expand Down
65 changes: 65 additions & 0 deletions js/src/instrumentation/plugins/openrouter-agent-plugin.test.ts
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Expand Up @@ -335,6 +335,71 @@ describe("OpenRouter Agent Plugin", () => {
metrics: {},
});
});

it("should aggregate reasoning fields from streaming deltas", () => {
expect(
aggregateOpenRouterChatChunks([
{
choices: [
{
delta: {
role: "assistant",
reasoning: "First, ",
reasoning_details: [
{
type: "reasoning.text",
text: "First, ",
},
],
},
},
],
},
{
choices: [
{
delta: {
reasoning_content: "check the answer.",
content: "OK",
reasoning_details: [
{
type: "reasoning.summary",
summary: "Checked the answer.",
},
],
},
finish_reason: "stop",
},
],
},
]),
).toEqual({
output: [
{
index: 0,
message: {
role: "assistant",
content: "OK",
reasoning: "First, check the answer.",
reasoning_content: "check the answer.",
reasoning_details: [
{
type: "reasoning.text",
text: "First, ",
},
{
type: "reasoning.summary",
summary: "Checked the answer.",
},
],
},
logprobs: null,
finish_reason: "stop",
},
],
metrics: {},
});
});
});

describe("callModel tool patching", () => {
Expand Down
28 changes: 28 additions & 0 deletions js/src/instrumentation/plugins/openrouter-agent-plugin.ts
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Expand Up @@ -633,6 +633,11 @@ export function aggregateOpenRouterChatChunks(
} {
let role: string | undefined;
let content = "";
let reasoning = "";
let hasReasoning = false;
let reasoningContent = "";
let hasReasoningContent = false;
let reasoningDetails: unknown[] | undefined;
let toolCalls:
| Array<{
index?: number;
Expand Down Expand Up @@ -670,6 +675,24 @@ export function aggregateOpenRouterChatChunks(
content += delta.content;
}

if (typeof delta.reasoning === "string") {
reasoning += delta.reasoning;
hasReasoning = true;
}

if (typeof delta.reasoning_content === "string") {
reasoning += delta.reasoning_content;
reasoningContent += delta.reasoning_content;
hasReasoningContent = true;
}

if (Array.isArray(delta.reasoning_details)) {
reasoningDetails = [
...(reasoningDetails || []),
...delta.reasoning_details,
];
}

const choiceFinishReason =
choice?.finishReason ?? choice?.finish_reason ?? undefined;
const deltaFinishReason =
Expand Down Expand Up @@ -740,6 +763,11 @@ export function aggregateOpenRouterChatChunks(
message: {
role,
content: content || undefined,
...(hasReasoning || hasReasoningContent ? { reasoning } : {}),
...(hasReasoningContent
? { reasoning_content: reasoningContent }
: {}),
...(reasoningDetails ? { reasoning_details: reasoningDetails } : {}),
...(toolCalls ? { tool_calls: toolCalls } : {}),
},
logprobs: null,
Expand Down
65 changes: 65 additions & 0 deletions js/src/instrumentation/plugins/openrouter-plugin.test.ts
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Expand Up @@ -282,6 +282,71 @@ describe("OpenRouter Plugin", () => {
metrics: {},
});
});

it("should aggregate reasoning fields from streaming deltas", () => {
expect(
aggregateOpenRouterChatChunks([
{
choices: [
{
delta: {
role: "assistant",
reasoning: "First, ",
reasoning_details: [
{
type: "reasoning.text",
text: "First, ",
},
],
},
},
],
},
{
choices: [
{
delta: {
reasoning_content: "check the answer.",
content: "OK",
reasoning_details: [
{
type: "reasoning.summary",
summary: "Checked the answer.",
},
],
},
finish_reason: "stop",
},
],
},
]),
).toEqual({
output: [
{
index: 0,
message: {
role: "assistant",
content: "OK",
reasoning: "First, check the answer.",
reasoning_content: "check the answer.",
reasoning_details: [
{
type: "reasoning.text",
text: "First, ",
},
{
type: "reasoning.summary",
summary: "Checked the answer.",
},
],
},
logprobs: null,
finish_reason: "stop",
},
],
metrics: {},
});
});
});

describe("aggregateOpenRouterResponseStreamEvents", () => {
Expand Down
28 changes: 28 additions & 0 deletions js/src/instrumentation/plugins/openrouter-plugin.ts
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Expand Up @@ -815,6 +815,11 @@ export function aggregateOpenRouterChatChunks(
} {
let role: string | undefined;
let content = "";
let reasoning = "";
let hasReasoning = false;
let reasoningContent = "";
let hasReasoningContent = false;
let reasoningDetails: unknown[] | undefined;
let toolCalls:
| Array<{
index?: number;
Expand Down Expand Up @@ -852,6 +857,24 @@ export function aggregateOpenRouterChatChunks(
content += delta.content;
}

if (typeof delta.reasoning === "string") {
reasoning += delta.reasoning;
hasReasoning = true;
}

if (typeof delta.reasoning_content === "string") {
reasoning += delta.reasoning_content;
reasoningContent += delta.reasoning_content;
hasReasoningContent = true;
}

if (Array.isArray(delta.reasoning_details)) {
reasoningDetails = [
...(reasoningDetails || []),
...delta.reasoning_details,
];
}

const choiceFinishReason =
choice?.finishReason ?? choice?.finish_reason ?? undefined;
const deltaFinishReason =
Expand Down Expand Up @@ -922,6 +945,11 @@ export function aggregateOpenRouterChatChunks(
message: {
role,
content: content || undefined,
...(hasReasoning || hasReasoningContent ? { reasoning } : {}),
...(hasReasoningContent
? { reasoning_content: reasoningContent }
: {}),
...(reasoningDetails ? { reasoning_details: reasoningDetails } : {}),
...(toolCalls ? { tool_calls: toolCalls } : {}),
},
logprobs: null,
Expand Down
6 changes: 6 additions & 0 deletions js/src/vendor-sdk-types/openrouter-agent.ts
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Expand Up @@ -15,6 +15,9 @@ export type OpenRouterAgentChatChoice = {
message?: {
role?: string;
content?: string | null;
reasoning?: string | null;
reasoning_content?: string | null;
reasoning_details?: unknown[];
tool_calls?: unknown;
};
logprobs?: unknown;
Expand All @@ -26,6 +29,9 @@ export type OpenRouterAgentChatCompletionChunk = {
delta?: {
role?: string;
content?: string;
reasoning?: string;
reasoning_content?: string;
reasoning_details?: unknown[];
tool_calls?: OpenRouterAgentChatToolCallDelta[];
toolCalls?: OpenRouterAgentChatToolCallDelta[];
finish_reason?: string | null;
Expand Down
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