diff --git a/packages/core-shared/src/instrumentation/sentry/sentry-logger.test.ts b/packages/core-shared/src/instrumentation/sentry/sentry-logger.test.ts
new file mode 100644
index 0000000..78a10b7
--- /dev/null
+++ b/packages/core-shared/src/instrumentation/sentry/sentry-logger.test.ts
@@ -0,0 +1,82 @@
+// packages/core-shared/src/instrumentation/sentry/sentry-logger.test.ts
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+vi.mock("@sentry/nextjs", () => ({
+  captureException: vi.fn(),
+  captureMessage: vi.fn(),
+  addBreadcrumb: vi.fn(),
+  setUser: vi.fn(),
+}));
+
+import * as Sentry from "@sentry/nextjs";
+import { SentryLogger } from "@/instrumentation/sentry/sentry-logger";
+
+describe("SentryLogger", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("captureException forwards to Sentry on first call", () => {
+    const logger = new SentryLogger();
+    const err = new Error("boom");
+    logger.captureException(err, { tags: { feature: "blog" } });
+    expect(Sentry.captureException).toHaveBeenCalledTimes(1);
+    expect((Sentry.captureException as ReturnType<typeof vi.fn>).mock.calls[0][0]).toBe(err);
+  });
+
+  it("captureException is a no-op when err already marked __sentryReported", () => {
+    const logger = new SentryLogger();
+    const err = new Error("already-reported");
+    Object.defineProperty(err, "__sentryReported", { value: true });
+    logger.captureException(err);
+    expect(Sentry.captureException).not.toHaveBeenCalled();
+  });
+
+  it("captureException marks err as __sentryReported after sending", () => {
+    const logger = new SentryLogger();
+    const err = new Error("once");
+    logger.captureException(err);
+    expect((err as unknown as { __sentryReported: boolean }).__sentryReported).toBe(true);
+    // Second call: no-op
+    logger.captureException(err);
+    expect(Sentry.captureException).toHaveBeenCalledTimes(1);
+  });
+
+  it("__sentryReported is non-enumerable", () => {
+    const logger = new SentryLogger();
+    const err = new Error("x");
+    logger.captureException(err);
+    expect(Object.keys(err)).not.toContain("__sentryReported");
+    expect(JSON.stringify(err)).not.toContain("__sentryReported");
+  });
+
+  it("captureMessage forwards to Sentry", () => {
+    const logger = new SentryLogger();
+    logger.captureMessage("hello", "warning", { tags: { foo: "bar" } });
+    expect(Sentry.captureMessage).toHaveBeenCalledWith(
+      "hello",
+      expect.objectContaining({ level: "warning" }),
+    );
+  });
+
+  it("addBreadcrumb forwards to Sentry", () => {
+    const logger = new SentryLogger();
+    logger.addBreadcrumb({ category: "test", message: "x", data: { k: "v" } });
+    expect(Sentry.addBreadcrumb).toHaveBeenCalledTimes(1);
+  });
+
+  it("setUser strips non-id keys and warns in dev", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const logger = new SentryLogger();
+    logger.setUser({ id: "u1", email: "a@b.c", username: "alice" } as unknown as { id: string });
+    expect(Sentry.setUser).toHaveBeenCalledWith({ id: "u1" });
+    expect(warn).toHaveBeenCalled();
+    warn.mockRestore();
+  });
+
+  it("setUser passes null through", () => {
+    const logger = new SentryLogger();
+    logger.setUser(null);
+    expect(Sentry.setUser).toHaveBeenCalledWith(null);
+  });
+});
diff --git a/packages/core-shared/src/instrumentation/sentry/sentry-logger.ts b/packages/core-shared/src/instrumentation/sentry/sentry-logger.ts
new file mode 100644
index 0000000..d14c393
--- /dev/null
+++ b/packages/core-shared/src/instrumentation/sentry/sentry-logger.ts
@@ -0,0 +1,65 @@
+// packages/core-shared/src/instrumentation/sentry/sentry-logger.ts
+import * as Sentry from "@sentry/nextjs";
+import type { ILogger, Breadcrumb, CaptureContext } from "../logger.interface";
+
+const REPORTED = "__sentryReported" as const;
+
+function isReported(err: unknown): boolean {
+  return (
+    err !== null &&
+    typeof err === "object" &&
+    Boolean((err as Record<string, unknown>)[REPORTED])
+  );
+}
+
+function markReported(err: unknown): void {
+  if (err !== null && typeof err === "object") {
+    Object.defineProperty(err, REPORTED, {
+      value: true,
+      enumerable: false,
+      configurable: false,
+      writable: false,
+    });
+  }
+}
+
+export class SentryLogger implements ILogger {
+  captureException(err: unknown, ctx?: CaptureContext): void {
+    if (isReported(err)) return;
+    Sentry.captureException(err, ctx);
+    markReported(err);
+  }
+
+  captureMessage(
+    msg: string,
+    level: "info" | "warning" | "error" = "info",
+    ctx?: CaptureContext,
+  ): void {
+    Sentry.captureMessage(msg, { level, ...ctx });
+  }
+
+  addBreadcrumb(b: Breadcrumb): void {
+    Sentry.addBreadcrumb({
+      category: b.category,
+      message: b.message,
+      level: b.level,
+      data: b.data,
+    });
+  }
+
+  setUser(user: { id: string } | null): void {
+    if (user === null) {
+      Sentry.setUser(null);
+      return;
+    }
+    const { id, ...extra } = user as { id: string } & Record<string, unknown>;
+    if (Object.keys(extra).length > 0) {
+      // R36 — strip non-id keys; warn in dev for visibility
+      console.warn(
+        "[SentryLogger.setUser] stripped non-id keys for PII safety:",
+        Object.keys(extra),
+      );
+    }
+    Sentry.setUser({ id });
+  }
+}