fix(ai): audit setting and removing a stored provider key

Removing a provider key, like setting one, left no audit row, unlike
every other credential change. Each key slot a PATCH touches now writes
user.ai-provider.key.set or .remove with the slot and never the value.

src/app/api/user/ai-provider/__tests__/route.test.ts

@@ -63,6 +63,10 @@ vi.mock("@/lib/ai/consent-guard", () => ({
   hasActiveConsentForSurface: vi.fn(),
 }));
 
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn(),
+}));
+
 import { GET, PATCH } from "../route";
 import { prisma } from "@/lib/db";
 import { resolveProviderAvailability } from "@/lib/ai/provider";
@@ -72,6 +76,7 @@ import { readServerProviderHealth } from "@/lib/ai/server-provider-health";
 import { getAssistantFlags } from "@/lib/feature-flags";
 import { providerCredentialPolicy } from "@/lib/sharing/provider-work-authority";
 import { hasActiveConsentForSurface } from "@/lib/ai/consent-guard";
+import { auditLog } from "@/lib/auth/audit";
 
 function patchRequest(body: unknown): Request {
   return new Request("http://localhost/api/user/ai-provider", {
@@ -243,6 +248,38 @@ describe("PATCH /api/user/ai-provider — v1.22 fields", () => {
   });
 });
 
+describe("PATCH /api/user/ai-provider — key changes are audited", () => {
+  const patch = PATCH as (req: Request) => Promise<Response>;
+
+  it("audits a removed key, naming its slot and never a value", async () => {
+    const res = await patch(patchRequest({ anthropicKey: null }));
+    expect(res.status).toBe(200);
+    expect(vi.mocked(auditLog)).toHaveBeenCalledTimes(1);
+    expect(vi.mocked(auditLog)).toHaveBeenCalledWith(
+      "user.ai-provider.key.remove",
+      expect.objectContaining({
+        userId: "u-1",
+        details: { slot: "anthropic" },
+      }),
+    );
+  });
+
+  it("audits a stored key without its value", async () => {
+    await patch(patchRequest({ openaiKey: "sk-test-123", compatKey: "" }));
+    const calls = vi.mocked(auditLog).mock.calls;
+    expect(calls.map(([action, opts]) => [action, opts?.details])).toEqual([
+      ["user.ai-provider.key.set", { slot: "openai" }],
+      ["user.ai-provider.key.remove", { slot: "openai-compatible" }],
+    ]);
+    expect(JSON.stringify(calls)).not.toContain("sk-test-123");
+  });
+
+  it("writes no key audit for a change that touches no key", async () => {
+    await patch(patchRequest({ responseTimeoutSeconds: 120 }));
+    expect(vi.mocked(auditLog)).not.toHaveBeenCalled();
+  });
+});
+
 // v1.33.1 (#470) — the OpenAI-compatible gateway writes three columns of its
 // own. What matters at this layer: the SSRF floor applies to the gateway's
 // base URL exactly as it does to the Local one, and the column is nobody

src/app/api/user/ai-provider/route.ts

@@ -4,9 +4,11 @@ import { prisma } from "@/lib/db";
 import {
   apiSuccess,
   apiError,
+  getClientIp,
   returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
+import { auditLog } from "@/lib/auth/audit";
 import { isPublicUrl } from "@/lib/validations/notifications";
 import { isLocalAiHostAllowed } from "@/lib/ai/local-host-allowlist";
 import { encrypt, decrypt } from "@/lib/crypto";
@@ -374,5 +376,28 @@ export const PATCH = apiHandler(async (request: NextRequest) => {
     await prisma.user.update({ where: { id: user.id }, data: updates });
   }
 
+  // A stored provider key is a credential: setting or removing one is
+  // audited like every other credential change, with the slot it went into
+  // and never the value. A removal used to leave no trace at all.
+  const keySlots = [
+    ["anthropic", body.anthropicKey],
+    ["openai", body.openaiKey],
+    ["local", body.localKey],
+    ["openai-compatible", body.compatKey],
+  ] as const;
+  for (const [slot, value] of keySlots) {
+    if (value === undefined) continue;
+    await auditLog(
+      value === null || value === ""
+        ? "user.ai-provider.key.remove"
+        : "user.ai-provider.key.set",
+      {
+        userId: user.id,
+        ipAddress: getClientIp(request),
+        details: { slot },
+      },
+    );
+  }
+
   return apiSuccess({ updated: true });
 });

tests/integration/ai-provider-key-removal.test.ts

@@ -111,6 +111,17 @@ describe("PATCH /api/user/ai-provider — removing one saved key", () => {
     expect(row.aiCompatKeyEncrypted).not.toBeNull();
     expect(row.aiProvider).toBe("OPENAI");
     expect(row.aiModel).toBe("gpt-4o-mini");
+    // The removal is audited, naming the slot and no value.
+    const audits = await getPrismaClient().auditLog.findMany({
+      where: { userId, action: { startsWith: "user.ai-provider.key." } },
+      select: { action: true, details: true },
+    });
+    expect(audits).toEqual([
+      {
+        action: "user.ai-provider.key.remove",
+        details: JSON.stringify({ slot: "openai" }),
+      },
+    ]);
   });
 
   it("the read the form seeds from reports the key gone", async () => {