diff --git a/packages/core-shared/src/instrumentation/sentry/pii-fields.ts b/packages/core-shared/src/instrumentation/sentry/pii-fields.ts
new file mode 100644
index 0000000..897b830
--- /dev/null
+++ b/packages/core-shared/src/instrumentation/sentry/pii-fields.ts
@@ -0,0 +1,46 @@
+// packages/core-shared/src/instrumentation/sentry/pii-fields.ts
+
+// R32 — substring match on event keys (case-insensitive)
+export const PII_KEY_SUBSTRINGS = [
+  "email",
+  "password",
+  "token",
+  "cookie",
+  "authorization",
+  "set-cookie",
+  "x-api-key",
+  "apikey",
+  "api_key",
+  "secret",
+] as const;
+
+// R33 — substring match on URL query-param keys (case-insensitive)
+export const PII_QUERY_PARAM_SUBSTRINGS = [
+  "token",
+  "email",
+  "password",
+  "key",
+  "sig",
+  "signature",
+  "access_token",
+  "accesstoken",
+  "secret",
+] as const;
+
+export const REDACTED_VALUE = "[redacted]" as const;
+export const REDACTED_IP = "[redacted-ip]" as const;
+
+// IPv4: simple dotted-quad; IPv6: any colon-separated hex with at least one ::
+export const IPV4_REGEX = /\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b/g;
+export const IPV6_REGEX =
+  /\b(?:[0-9a-fA-F]{1,4}:){2,7}[0-9a-fA-F]{1,4}\b|::(?:[0-9a-fA-F]{1,4}:){0,6}[0-9a-fA-F]{1,4}/g;
+
+export function keyContainsPii(key: string): boolean {
+  const lower = key.toLowerCase();
+  return PII_KEY_SUBSTRINGS.some((s) => lower.includes(s));
+}
+
+export function queryParamContainsPii(key: string): boolean {
+  const lower = key.toLowerCase();
+  return PII_QUERY_PARAM_SUBSTRINGS.some((s) => lower.includes(s));
+}
diff --git a/packages/core-shared/src/instrumentation/sentry/scrub.test.ts b/packages/core-shared/src/instrumentation/sentry/scrub.test.ts
new file mode 100644
index 0000000..5b5ff07
--- /dev/null
+++ b/packages/core-shared/src/instrumentation/sentry/scrub.test.ts
@@ -0,0 +1,139 @@
+// packages/core-shared/src/instrumentation/sentry/scrub.test.ts
+import { describe, it, expect } from "vitest";
+import { beforeSend, beforeSendTransaction } from "@/instrumentation/sentry/scrub";
+
+describe("beforeSend", () => {
+  it("redacts top-level keys whose names contain PII substrings", () => {
+    const event = {
+      extra: { email: "a@b.c", username: "alice" },
+      contexts: { custom: { password: "p", note: "ok" } },
+    } as Parameters<typeof beforeSend>[0];
+    const result = beforeSend(event, {} as Parameters<typeof beforeSend>[1]) as Record<
+      string,
+      unknown
+    >;
+    const extra = result["extra"] as Record<string, unknown>;
+    const contexts = result["contexts"] as { custom: Record<string, unknown> };
+    expect(extra["email"]).toBe("[redacted]");
+    expect(extra["username"]).toBe("alice");
+    expect(contexts.custom["password"]).toBe("[redacted]");
+    expect(contexts.custom["note"]).toBe("ok");
+  });
+
+  it("redacts derived key names (substring match): userEmail, accessToken, apiKey", () => {
+    const event = {
+      extra: { userEmail: "a@b.c", accessToken: "t", apiKey: "k", id: "u1" },
+    } as Parameters<typeof beforeSend>[0];
+    const result = beforeSend(event, {} as Parameters<typeof beforeSend>[1]) as Record<
+      string,
+      unknown
+    >;
+    const extra = result["extra"] as Record<string, unknown>;
+    expect(extra["userEmail"]).toBe("[redacted]");
+    expect(extra["accessToken"]).toBe("[redacted]");
+    expect(extra["apiKey"]).toBe("[redacted]");
+    expect(extra["id"]).toBe("u1");
+  });
+
+  it("redacts headers map keys case-insensitively", () => {
+    const event = {
+      request: {
+        headers: { Authorization: "Bearer x", "Set-Cookie": "session=abc", "User-Agent": "ua" },
+      },
+    } as Parameters<typeof beforeSend>[0];
+    const result = beforeSend(event, {} as Parameters<typeof beforeSend>[1]) as Record<
+      string,
+      unknown
+    >;
+    const request = result["request"] as { headers: Record<string, unknown> };
+    expect(request.headers["Authorization"]).toBe("[redacted]");
+    expect(request.headers["Set-Cookie"]).toBe("[redacted]");
+    expect(request.headers["User-Agent"]).toBe("ua");
+  });
+
+  it("redacts IPv4 addresses found in string values", () => {
+    const event = { extra: { note: "Connection from 192.168.1.10 failed" } } as Parameters<
+      typeof beforeSend
+    >[0];
+    const result = beforeSend(event, {} as Parameters<typeof beforeSend>[1]) as Record<
+      string,
+      unknown
+    >;
+    const extra = result["extra"] as Record<string, unknown>;
+    expect(extra["note"]).toBe("Connection from [redacted-ip] failed");
+  });
+
+  it("redacts IPv6 addresses found in string values", () => {
+    const event = { extra: { note: "Tunnel to fe80::1ff:fe23:4567:890a established" } } as Parameters<
+      typeof beforeSend
+    >[0];
+    const result = beforeSend(event, {} as Parameters<typeof beforeSend>[1]) as Record<
+      string,
+      unknown
+    >;
+    const extra = result["extra"] as Record<string, unknown>;
+    expect(extra["note"] as string).toContain("[redacted-ip]");
+  });
+
+  it("does not crash on null/undefined branches", () => {
+    expect(beforeSend({ extra: null } as Parameters<typeof beforeSend>[0], {} as Parameters<typeof beforeSend>[1])).toBeTruthy();
+    expect(beforeSend({} as Parameters<typeof beforeSend>[0], {} as Parameters<typeof beforeSend>[1])).toBeTruthy();
+  });
+
+  it("returns the event (not null) — keeps Sentry transport flowing", () => {
+    expect(
+      beforeSend({ extra: { ok: true } } as Parameters<typeof beforeSend>[0], {} as Parameters<typeof beforeSend>[1]),
+    ).toBeTruthy();
+  });
+});
+
+describe("beforeSendTransaction", () => {
+  it("strips PII query params from request.url", () => {
+    const event = {
+      request: { url: "https://app/api/foo?token=secret&user=alice&email=a@b.c" },
+    } as Parameters<typeof beforeSendTransaction>[0];
+    const result = beforeSendTransaction(
+      event,
+      {} as Parameters<typeof beforeSendTransaction>[1],
+    ) as Record<string, unknown>;
+    const request = result["request"] as { url: string };
+    expect(request.url).toContain("token=%5Bredacted%5D");
+    expect(request.url).toContain("email=%5Bredacted%5D");
+    expect(request.url).toContain("user=alice");
+  });
+
+  it("strips PII query params from event.transaction", () => {
+    const event = { transaction: "/foo?token=x&id=y" } as Parameters<
+      typeof beforeSendTransaction
+    >[0];
+    const result = beforeSendTransaction(
+      event,
+      {} as Parameters<typeof beforeSendTransaction>[1],
+    ) as Record<string, unknown>;
+    expect(result["transaction"] as string).toContain("token=%5Bredacted%5D");
+    expect(result["transaction"] as string).toContain("id=y");
+  });
+
+  it("matches derived param names (accessToken, ApiSecret)", () => {
+    const event = { request: { url: "https://x/y?accessToken=t&ApiSecret=z&safe=1" } } as Parameters<
+      typeof beforeSendTransaction
+    >[0];
+    const result = beforeSendTransaction(
+      event,
+      {} as Parameters<typeof beforeSendTransaction>[1],
+    ) as Record<string, unknown>;
+    const request = result["request"] as { url: string };
+    expect(request.url).toContain("accessToken=%5Bredacted%5D");
+    expect(request.url).toContain("ApiSecret=%5Bredacted%5D");
+    expect(request.url).toContain("safe=1");
+  });
+
+  it("returns the event when no URL present", () => {
+    expect(
+      beforeSendTransaction(
+        {} as Parameters<typeof beforeSendTransaction>[0],
+        {} as Parameters<typeof beforeSendTransaction>[1],
+      ),
+    ).toBeTruthy();
+  });
+});
diff --git a/packages/core-shared/src/instrumentation/sentry/scrub.ts b/packages/core-shared/src/instrumentation/sentry/scrub.ts
new file mode 100644
index 0000000..8c8ba14
--- /dev/null
+++ b/packages/core-shared/src/instrumentation/sentry/scrub.ts
@@ -0,0 +1,70 @@
+// packages/core-shared/src/instrumentation/sentry/scrub.ts
+import type { ErrorEvent, EventHint, TransactionEvent } from "@sentry/nextjs";
+import {
+  IPV4_REGEX,
+  IPV6_REGEX,
+  REDACTED_IP,
+  REDACTED_VALUE,
+  keyContainsPii,
+  queryParamContainsPii,
+} from "./pii-fields";
+
+function redactString(s: string): string {
+  // Create new regexes each call since regexes with /g are stateful
+  const ipv4 = new RegExp(IPV4_REGEX.source, "g");
+  const ipv6 = new RegExp(IPV6_REGEX.source, "g");
+  return s.replace(ipv4, REDACTED_IP).replace(ipv6, REDACTED_IP);
+}
+
+function deepScrub(value: unknown, parentKey = ""): unknown {
+  if (value === null || value === undefined) return value;
+  if (typeof value === "string") {
+    return parentKey && keyContainsPii(parentKey) ? REDACTED_VALUE : redactString(value);
+  }
+  if (typeof value === "number" || typeof value === "boolean") {
+    return parentKey && keyContainsPii(parentKey) ? REDACTED_VALUE : value;
+  }
+  if (Array.isArray(value)) {
+    return value.map((v) => deepScrub(v, parentKey));
+  }
+  if (typeof value === "object") {
+    const out: Record<string, unknown> = {};
+    for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
+      out[k] = keyContainsPii(k) ? REDACTED_VALUE : deepScrub(v, k);
+    }
+    return out;
+  }
+  return value;
+}
+
+export function beforeSend(event: ErrorEvent, _hint: EventHint): ErrorEvent | null {
+  return deepScrub(event) as ErrorEvent;
+}
+
+function scrubUrl(url: string): string {
+  try {
+    const u = new URL(url, "http://placeholder.local");
+    for (const [k] of Array.from(u.searchParams.entries())) {
+      if (queryParamContainsPii(k)) {
+        u.searchParams.set(k, REDACTED_VALUE);
+      }
+    }
+    return url.startsWith("/") ? `${u.pathname}${u.search}` : u.toString();
+  } catch {
+    return url;
+  }
+}
+
+export function beforeSendTransaction(
+  event: TransactionEvent,
+  _hint: EventHint,
+): TransactionEvent | null {
+  const out: TransactionEvent = { ...event };
+  if (out.request?.url) {
+    out.request = { ...out.request, url: scrubUrl(out.request.url) };
+  }
+  if (out.transaction && (out.transaction.includes("?") || out.transaction.includes("="))) {
+    out.transaction = scrubUrl(out.transaction);
+  }
+  return out;
+}