From a27ebf6e02dfbf44e63e503b821dbf19928ee0b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Halber?= <cedric@braintrustdata.com>
Date: Tue, 7 Jul 2026 16:54:45 -0700
Subject: [PATCH] fix(mastra): use Mastra span id as Braintrust row id for
 logFeedback
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BraintrustObservabilityExporter.onStart let SpanImpl auto-generate the
row id (this._id = eventId ?? idGenerator.getSpanId()), so the id was
unknowable to anyone outside the exporter. A Mastra user calling
logger.logFeedback({ id: <mastra span id> }) — or Mastra's score-event
bus forwarding score.spanId — targeted a row that didn't exist, and the
feedback landed as a stray row instead of merging into the generation
it was meant to score.

Pass event: { id: exported.id } on startSpan so the Mastra span id is
used as the Braintrust row id, matching the upstream @mastra/braintrust
fix (mastra-ai/mastra#11927, fixes #11899). The Braintrust span_id is
left auto-generated so W3C trace-context propagation still works for
subspans; only the row id (which logFeedback/mergeRowBatch key on) is
aliased to the Mastra span id.

Adds js/src/wrappers/mastra.test.ts covering both the row-id aliasing
and a subsequent logFeedback merge.

Refs: mastra-ai/mastra#11927
---
 .changeset/mastra-logfeedback-row-id.md |  5 ++
 js/src/wrappers/mastra.test.ts          | 81 +++++++++++++++++++++++++
 js/src/wrappers/mastra.ts               |  6 ++
 3 files changed, 92 insertions(+)
 create mode 100644 .changeset/mastra-logfeedback-row-id.md
 create mode 100644 js/src/wrappers/mastra.test.ts

diff --git a/.changeset/mastra-logfeedback-row-id.md b/.changeset/mastra-logfeedback-row-id.md
new file mode 100644
index 000000000..0f5230ca1
--- /dev/null
+++ b/.changeset/mastra-logfeedback-row-id.md
@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+fix(mastra): Use the Mastra span id as the Braintrust row id so `logFeedback` attaches to the right row instead of landing as a stray. Matches the upstream `@mastra/braintrust` fix (mastra-ai/mastra#11927).
diff --git a/js/src/wrappers/mastra.test.ts b/js/src/wrappers/mastra.test.ts
new file mode 100644
index 000000000..dcced568b
--- /dev/null
+++ b/js/src/wrappers/mastra.test.ts
@@ -0,0 +1,81 @@
+import {
+  afterEach,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  test,
+} from "vitest";
+import { configureNode } from "../node/config";
+import { _exportsForTestingOnly, initLogger } from "../logger";
+import { BraintrustObservabilityExporter } from "./mastra";
+
+try {
+  configureNode();
+} catch {
+  // Best-effort initialization for test environments.
+}
+
+type ExportedSpan = Parameters<
+  BraintrustObservabilityExporter["exportTracingEvent"]
+>[0]["exportedSpan"];
+
+const span = (overrides: Partial<ExportedSpan>): ExportedSpan => ({
+  id: "span-1",
+  traceId: "trace-1",
+  name: "agent run",
+  type: "agent_run",
+  startTime: 1_000_000,
+  ...overrides,
+});
+
+describe("BraintrustObservabilityExporter", () => {
+  let backgroundLogger: ReturnType<
+    typeof _exportsForTestingOnly.useTestBackgroundLogger
+  >;
+  let logger: ReturnType<typeof initLogger>;
+
+  beforeAll(async () => {
+    await _exportsForTestingOnly.simulateLoginForTests();
+  });
+
+  beforeEach(() => {
+    backgroundLogger = _exportsForTestingOnly.useTestBackgroundLogger();
+    logger = initLogger({
+      projectId: "test-project-id",
+      projectName: "mastra.test.ts",
+    });
+  });
+
+  afterEach(() => {
+    _exportsForTestingOnly.clearTestBackgroundLogger();
+  });
+
+  test("logFeedback keyed on the Mastra span id merges into the span row", async () => {
+    const exporter = new BraintrustObservabilityExporter();
+    const id = "mastra-span-123";
+
+    await exporter.exportTracingEvent({
+      type: "span_started",
+      exportedSpan: span({ id }),
+    });
+    await exporter.exportTracingEvent({
+      type: "span_ended",
+      exportedSpan: span({ id, endTime: 1_000_001 }),
+    });
+    // A Mastra user (or Mastra's score-event bus) knows only the Mastra span id.
+    logger.logFeedback({ id, scores: { quality: 0.9 }, source: "external" });
+
+    await backgroundLogger.flush();
+    const rows = (await backgroundLogger.drain()) as any[];
+
+    // The exporter aliases the row id to the Mastra span id, so the feedback
+    // merge row keys onto the span row and `mergeRowBatch` collapses them into a
+    // single row carrying both the span and the score. Without the aliasing the
+    // feedback would land as a separate orphan row.
+    const merged = rows.filter((r) => r.id === id);
+    expect(merged).toHaveLength(1);
+    expect(merged[0].span_attributes?.name).toBe("agent run");
+    expect(merged[0].scores?.quality).toBe(0.9);
+  });
+});
diff --git a/js/src/wrappers/mastra.ts b/js/src/wrappers/mastra.ts
index 9946a9643..28bba3410 100644
--- a/js/src/wrappers/mastra.ts
+++ b/js/src/wrappers/mastra.ts
@@ -272,6 +272,12 @@ export class BraintrustObservabilityExporter implements MastraObservabilityExpor
       name: exported.name,
       spanAttributes: { type: spanTypeFor(exported.type) },
       startTime: epochSeconds(exported.startTime),
+      // Use the Mastra span id as the Braintrust row id so that
+      // `logFeedback({ id: <mastra span id> })` (and Mastra's score events)
+      // attach to the right row. Without this, `SpanImpl` auto-generates a
+      // row id (`this._id = eventId ?? idGenerator.getSpanId()`) that no
+      // external caller could know.
+      event: { id: exported.id },
     };
 
     const parentRecord = exported.parentSpanId