diff --git a/packages/core-testing/src/instrumentation/recording-tracer.test.ts b/packages/core-testing/src/instrumentation/recording-tracer.test.ts
new file mode 100644
index 0000000..b571288
--- /dev/null
+++ b/packages/core-testing/src/instrumentation/recording-tracer.test.ts
@@ -0,0 +1,70 @@
+import { describe, it, expect } from "vitest";
+import { RecordingTracer } from "@/instrumentation/recording-tracer";
+
+describe("RecordingTracer", () => {
+  it("records every startSpan call with name, op, attributes, status, durationMs", async () => {
+    const tracer = new RecordingTracer();
+    await tracer.startSpan(
+      { name: "blog.getArticles", op: "use-case", attributes: { limit: 10 } },
+      async (span) => {
+        span.setAttribute("count", 3);
+        span.setStatus("ok");
+        return undefined;
+      },
+    );
+    expect(tracer.spans).toHaveLength(1);
+    const s = tracer.spans[0]!;
+    expect(s.name).toBe("blog.getArticles");
+    expect(s.op).toBe("use-case");
+    expect(s.attributes).toMatchObject({ limit: 10, count: 3 });
+    expect(s.status).toBe("ok");
+    expect(typeof s.durationMs).toBe("number");
+    expect(s.durationMs).toBeGreaterThanOrEqual(0);
+  });
+
+  it("records error status when fn throws", async () => {
+    const tracer = new RecordingTracer();
+    await expect(
+      tracer.startSpan({ name: "x" }, async () => {
+        throw new Error("boom");
+      }),
+    ).rejects.toThrow("boom");
+    expect(tracer.spans).toHaveLength(1);
+    expect(tracer.spans[0]!.status).toBe("error");
+    expect(tracer.spans[0]!.statusMessage).toBe("boom");
+  });
+
+  it("records error status when set explicitly via span.setStatus", async () => {
+    const tracer = new RecordingTracer();
+    await tracer.startSpan({ name: "x" }, async (span) => {
+      span.setStatus("error", "validation failed");
+      return undefined;
+    });
+    expect(tracer.spans[0]!.status).toBe("error");
+    expect(tracer.spans[0]!.statusMessage).toBe("validation failed");
+  });
+
+  it("reset() clears recorded spans", async () => {
+    const tracer = new RecordingTracer();
+    await tracer.startSpan({ name: "x" }, async () => undefined);
+    expect(tracer.spans).toHaveLength(1);
+    tracer.reset();
+    expect(tracer.spans).toHaveLength(0);
+  });
+
+  it("findSpan returns first matching span by name", async () => {
+    const tracer = new RecordingTracer();
+    await tracer.startSpan({ name: "a" }, async () => undefined);
+    await tracer.startSpan({ name: "b" }, async () => undefined);
+    expect(tracer.findSpan("b")).toBeDefined();
+    expect(tracer.findSpan("missing")).toBeUndefined();
+  });
+
+  it("nested spans are recorded in order (children appear after parent end)", async () => {
+    const tracer = new RecordingTracer();
+    await tracer.startSpan({ name: "parent" }, async () => {
+      await tracer.startSpan({ name: "child" }, async () => undefined);
+    });
+    expect(tracer.spans.map((s) => s.name)).toEqual(["child", "parent"]);
+  });
+});
diff --git a/packages/core-testing/src/instrumentation/recording-tracer.ts b/packages/core-testing/src/instrumentation/recording-tracer.ts
new file mode 100644
index 0000000..31a1c36
--- /dev/null
+++ b/packages/core-testing/src/instrumentation/recording-tracer.ts
@@ -0,0 +1,59 @@
+import type {
+  ITracer,
+  ISpan,
+  SpanOpts,
+  AttributeValue,
+} from "@repo/core-shared/instrumentation";
+
+export type RecordedSpan = {
+  name: string;
+  op?: string;
+  attributes: Record<string, AttributeValue>;
+  status: "ok" | "error";
+  statusMessage?: string;
+  durationMs: number;
+};
+
+export class RecordingTracer implements ITracer {
+  spans: RecordedSpan[] = [];
+
+  async startSpan<T>(opts: SpanOpts, fn: (span: ISpan) => Promise<T>): Promise<T> {
+    const start = performance.now();
+    const recorded: RecordedSpan = {
+      name: opts.name,
+      op: opts.op,
+      attributes: { ...(opts.attributes ?? {}) },
+      status: "ok",
+      durationMs: 0,
+    };
+    const span: ISpan = {
+      setAttribute(key, value) {
+        recorded.attributes[key] = value;
+      },
+      setStatus(status, message) {
+        recorded.status = status;
+        recorded.statusMessage = message;
+      },
+    };
+    try {
+      const result = await fn(span);
+      recorded.durationMs = performance.now() - start;
+      this.spans.push(recorded);
+      return result;
+    } catch (err) {
+      recorded.status = "error";
+      recorded.statusMessage = err instanceof Error ? err.message : String(err);
+      recorded.durationMs = performance.now() - start;
+      this.spans.push(recorded);
+      throw err;
+    }
+  }
+
+  reset(): void {
+    this.spans = [];
+  }
+
+  findSpan(name: string): RecordedSpan | undefined {
+    return this.spans.find((s) => s.name === name);
+  }
+}