diff --git a/src/lib/whoop/__tests__/response-classifier.test.ts b/src/lib/whoop/__tests__/response-classifier.test.ts
index e24ba2466..073ce522a 100644
--- a/src/lib/whoop/__tests__/response-classifier.test.ts
+++ b/src/lib/whoop/__tests__/response-classifier.test.ts
@@ -3,6 +3,7 @@ import {
   WhoopApiError,
   classifyWhoopError,
   classifyWhoopResponse,
+  isInvalidGrant,
 } from "../response-classifier";
 
 describe("classifyWhoopResponse", () => {
@@ -90,4 +91,93 @@ describe("classifyWhoopError", () => {
     expect(classifyWhoopError(new Error("network down"))).toBe("transient");
     expect(classifyWhoopError("boom")).toBe("transient");
   });
+
+  it("lifts a 400 invalid_grant from the token endpoint to reauth_required", () => {
+    const err = new WhoopApiError({
+      verb: "refreshAccessToken",
+      classification: "persistent",
+      httpStatus: 400,
+      reason: "http_400",
+      upstreamError: "invalid_grant",
+    });
+    // The construction-time verdict is persistent (status-only), but the
+    // refined classifier promotes the revoked-grant case to reauth.
+    expect(err.classification).toBe("persistent");
+    expect(classifyWhoopError(err)).toBe("reauth_required");
+  });
+
+  it("keeps other 400s persistent (only invalid_grant is reauth)", () => {
+    const badClient = new WhoopApiError({
+      verb: "refreshAccessToken",
+      classification: "persistent",
+      httpStatus: 400,
+      reason: "http_400",
+      upstreamError: "invalid_client",
+    });
+    expect(classifyWhoopError(badClient)).toBe("persistent");
+
+    const bareBadRequest = new WhoopApiError({
+      verb: "fetchRecoveries",
+      classification: "persistent",
+      httpStatus: 400,
+      reason: "http_400",
+    });
+    expect(classifyWhoopError(bareBadRequest)).toBe("persistent");
+  });
+
+  it("detects invalid_grant from a legacy unwrapped message too", () => {
+    const err = new Error(
+      "WHOOP refreshAccessToken error: 400 - invalid_grant",
+    );
+    expect(classifyWhoopError(err)).toBe("reauth_required");
+  });
+});
+
+describe("isInvalidGrant", () => {
+  it("is true only for a 400 carrying invalid_grant", () => {
+    expect(
+      isInvalidGrant(
+        new WhoopApiError({
+          verb: "refreshAccessToken",
+          classification: "persistent",
+          httpStatus: 400,
+          reason: "http_400",
+          upstreamError: "invalid_grant",
+        }),
+      ),
+    ).toBe(true);
+  });
+
+  it("is false for invalid_grant on a non-400 status", () => {
+    expect(
+      isInvalidGrant(
+        new WhoopApiError({
+          verb: "refreshAccessToken",
+          classification: "reauth_required",
+          httpStatus: 401,
+          reason: "http_401",
+          upstreamError: "invalid_grant",
+        }),
+      ),
+    ).toBe(false);
+  });
+
+  it("is false for a 400 with a different OAuth error", () => {
+    expect(
+      isInvalidGrant(
+        new WhoopApiError({
+          verb: "refreshAccessToken",
+          classification: "persistent",
+          httpStatus: 400,
+          reason: "http_400",
+          upstreamError: "invalid_client",
+        }),
+      ),
+    ).toBe(false);
+  });
+
+  it("is false for a non-WhoopApiError without the signal", () => {
+    expect(isInvalidGrant(new Error("network down"))).toBe(false);
+    expect(isInvalidGrant("boom")).toBe(false);
+  });
 });
diff --git a/src/lib/whoop/response-classifier.ts b/src/lib/whoop/response-classifier.ts
index 793ed3510..b6b5538ce 100644
--- a/src/lib/whoop/response-classifier.ts
+++ b/src/lib/whoop/response-classifier.ts
@@ -100,6 +100,12 @@ export class WhoopApiError extends Error {
   readonly httpStatus: number | undefined;
   readonly reason: string;
   readonly verb: string;
+  /**
+   * The OAuth `error` code from a token-endpoint failure body (e.g.
+   * `invalid_grant` when a refresh token is revoked). Undefined for the
+   * collection endpoints, which signal failure through the status code alone.
+   */
+  readonly upstreamError: string | undefined;
 
   constructor(opts: {
     verb: string;
@@ -121,17 +127,48 @@ export class WhoopApiError extends Error {
     this.classification = opts.classification;
     this.httpStatus = opts.httpStatus;
     this.reason = opts.reason;
+    this.upstreamError = opts.upstreamError;
   }
 }
 
+/**
+ * True when a caught error is an OAuth `invalid_grant` on a 400 from the token
+ * endpoint — the canonical signal that the stored refresh token was revoked
+ * (the user disconnected the app, or WHOOP expired the grant). A plain
+ * `classifyWhoopResponse(400)` buckets this as `persistent`, which never
+ * prompts a reconnect; lifting it to `reauth_required` makes the connection
+ * surface the reauth prompt. Scoped tightly to a 400 carrying `invalid_grant`
+ * so other 400s (a malformed request, a bad client_secret → `invalid_client`)
+ * stay persistent.
+ *
+ * Robust to a lost prototype across a pg-boss retry: it reads the dedicated
+ * `upstreamError` field when present, else falls back to the
+ * `"... error: 400 - invalid_grant"` message segment.
+ */
+export function isInvalidGrant(err: unknown): boolean {
+  if (err instanceof WhoopApiError) {
+    if (err.httpStatus !== 400) return false;
+    if (err.upstreamError === "invalid_grant") return true;
+    return /\binvalid_grant\b/.test(err.message);
+  }
+  const msg = err instanceof Error ? err.message : String(err);
+  return /WHOOP\s+\w+\s+error:\s*400\b[\s\S]*\binvalid_grant\b/.test(msg);
+}
+
 /**
  * Read the classification from any caught error. Returns `transient` for a
  * non-`WhoopApiError` input so a call site surfacing a plain `Error` retries
  * rather than permanently disabling the integration. Falls back to parsing the
  * HTTP status out of the legacy `"WHOOP <verb> error: <status>"` message shape
  * for callers that lose the original prototype across a pg-boss retry.
+ *
+ * A 400 `invalid_grant` from the token endpoint is the one 4xx that is NOT
+ * persistent: the refresh token was revoked, so the verdict is
+ * `reauth_required` and the user is prompted to reconnect.
  */
 export function classifyWhoopError(err: unknown): WhoopClassification {
+  if (isInvalidGrant(err)) return "reauth_required";
+
   if (err instanceof WhoopApiError) return err.classification;
 
   const msg = err instanceof Error ? err.message : String(err);