refactor: share the secret-shape matcher from one leaf

The idempotency cache refuses to persist a body carrying a HealthLog token or an AI provider key. The notification test routes are about to refuse echoing such text too, so the pattern moves to src/lib/secret-shape.ts instead of being written a second time. Behaviour of the cache is unchanged.

src/lib/__tests__/secret-shape.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+
+import { looksSecretShaped } from "@/lib/secret-shape";
+
+describe("looksSecretShaped", () => {
+  it.each([
+    ["an access token", "token hlk_abc123"],
+    ["a refresh token", "hlr_xyz789"],
+    ["a share-link token", "see hls_def456"],
+    ["an invite token", "hlv_0a1b2c3d"],
+    ["an elevation token", "hle_0a1b2c3d"],
+    ["an OpenAI key", "echoed sk-1234567890"],
+    ["an Anthropic key", "sk-ant-api03-xyz12345"],
+  ])("matches %s", (_label, text) => {
+    expect(looksSecretShaped(text)).toBe(true);
+  });
+
+  it.each([
+    ["a word containing sk-", "task-id must not contain spaces"],
+    ["another one", "risk-management"],
+    ["a JSON error body", '{"error":"Bad Request","errorCode":400}'],
+  ])("does not match %s", (_label, text) => {
+    expect(looksSecretShaped(text)).toBe(false);
+  });
+});

src/lib/idempotency.ts

@@ -28,6 +28,7 @@ import { isP2002 } from "@/lib/prisma-errors";
 import { findActiveGrant } from "@/lib/sharing/grants";
 import { decrypt, encrypt } from "@/lib/crypto";
 import { createHash } from "node:crypto";
+import { looksSecretShaped } from "@/lib/secret-shape";
 
 const TTL_MS = 24 * 60 * 60 * 1000;
 /**
@@ -641,21 +642,11 @@ export function withIdempotency<
       // Defence-in-depth: never persist a body that carries a freshly-issued
       // bearer / refresh token or a third-party AI provider key. Auth and
       // settings routes shouldn't be wrapped in withIdempotency to begin
-      // with, but if a future caller forgets we refuse to leak.
-      //   `hlk_`    = our access tokens
-      //   `hlr_`    = our refresh tokens
-      //   `hls_`    = clinician share-link tokens (v1.11)
-      //   `hlv_`    = registration invite tokens (v1.16 — the admin mint
-      //               response is the one place the raw token appears)
-      //   `sk-…`    = OpenAI / Anthropic keys (full token form, not the
-      //               raw substring — a 422 body explaining "task-id…"
-      //               or any other word containing `sk-` would otherwise
-      //               silently break idempotency for benign retries).
-      const SECRET_PATTERN =
-        /(?:\b(?:hlk_|hlr_|hls_|hlv_|hle_)[A-Za-z0-9_-]+|\bsk-(?:ant-)?[A-Za-z0-9_-]{8,})/;
+      // with, but if a future caller forgets we refuse to leak. The prefixes
+      // are listed where the matcher lives (`src/lib/secret-shape.ts`).
       const cloned = response.clone();
       const text = await cloned.text();
-      if (!SECRET_PATTERN.test(text)) {
+      if (!looksSecretShaped(text)) {
         await persistCached(ctx, response, text);
       } else {
         // Secret-shaped body — drop the claim so the key isn't left

src/lib/secret-shape.ts

@@ -0,0 +1,21 @@
+/**
+ * One definition of "this text carries a credential HealthLog or a common
+ * AI provider mints", shared by every surface that refuses to store or echo
+ * such text.
+ *
+ *   `hlk_` access tokens, `hlr_` refresh tokens, `hls_` clinician share-link
+ *   tokens, `hlv_` registration invite tokens, `hle_` elevation tokens;
+ *   `sk-…` / `sk-ant-…` OpenAI and Anthropic keys, in the full token form
+ *   only: a bare `sk-` substring ("task-id", "risk-management") is not a key,
+ *   and matching it would refuse benign text.
+ *
+ * It is a shape test, not a secret detector. A credential without one of
+ * these prefixes (a relay's own app token, a password) passes, so a caller
+ * that knows the secrets in play must also refuse text containing them.
+ */
+const SECRET_SHAPED =
+  /(?:\b(?:hlk_|hlr_|hls_|hlv_|hle_)[A-Za-z0-9_-]+|\bsk-(?:ant-)?[A-Za-z0-9_-]{8,})/;
+
+export function looksSecretShaped(text: string): boolean {
+  return SECRET_SHAPED.test(text);
+}