fix(FN-4915): harden fn_secret_get secret audit payload guard

Fusion-Task-Id: FN-4915
Fusion-Task-Lineage: d5c49dae-6069-4998-b632-aca52cc312dc

packages/cli/src/__tests__/extension-fn-secret-get.test.ts

@@ -6,9 +6,14 @@ const listSecretsMock = vi.hoisted(() => vi.fn());
 const approvalCreateMock = vi.hoisted(() => vi.fn());
 const approvalFindLatestByDedupeKeyMock = vi.hoisted(() => vi.fn());
 const recordRunAuditEventMock = vi.hoisted(() => vi.fn());
+const assertNoSecretPlaintextMock = vi.hoisted(() => vi.fn());
 
 vi.mock("@fusion/dashboard", () => ({ registerGithubTrackingHook: vi.fn() }));
-vi.mock("@fusion/engine", () => ({ createFnAgent: vi.fn(), fetchWebContent: vi.fn() }));
+vi.mock("@fusion/engine", () => ({
+  createFnAgent: vi.fn(),
+  fetchWebContent: vi.fn(),
+  assertNoSecretPlaintext: assertNoSecretPlaintextMock,
+}));
 
 vi.mock("@fusion/core", async () => {
   const actual = await vi.importActual<typeof import("@fusion/core")>("@fusion/core");
@@ -52,6 +57,7 @@ describe("extension fn_secret_get", () => {
     resolveSecretAccessPolicyMock.mockReturnValue({ policy: "auto", source: "secret" });
     approvalFindLatestByDedupeKeyMock.mockReturnValue(null);
     approvalCreateMock.mockReturnValue({ id: "apr-1", status: "pending" });
+    assertNoSecretPlaintextMock.mockImplementation(() => {});
   });
 
   it("returns value for auto policy", async () => {
@@ -61,8 +67,15 @@ describe("extension fn_secret_get", () => {
     const result = await tool.execute("id", { key: "API_KEY" }, undefined, undefined, { cwd: process.cwd(), agentId: "agent-1", runId: "run-1" });
     expect(result.details.value).toBe("secret-value");
     expect(approvalCreateMock).not.toHaveBeenCalled();
-    expect(recordRunAuditEventMock.mock.calls[0][0].mutationType).toBe("secret:read");
-    expect(JSON.stringify(recordRunAuditEventMock.mock.calls[0][0])).not.toContain("secret-value");
+    const event = recordRunAuditEventMock.mock.calls[0][0];
+    expect(event.mutationType).toBe("secret:read");
+    expect(event.metadata).toEqual({ key: "API_KEY", scope: "project" });
+    expect(event.metadata).not.toHaveProperty("plaintextValue");
+    expect(event.metadata).not.toHaveProperty("value");
+    expect(event.metadata).not.toHaveProperty("ciphertext");
+    expect(event.metadata).not.toHaveProperty("nonce");
+    expect(event.metadata).not.toHaveProperty("decrypted");
+    expect(JSON.stringify(event)).not.toContain("secret-value");
   });
 
   it("returns pending_approval for prompt policy", async () => {
@@ -75,6 +88,22 @@ describe("extension fn_secret_get", () => {
     expect(approvalCreateMock).toHaveBeenCalled();
   });
 
+  it("skips audit emission if metadata guard throws", async () => {
+    assertNoSecretPlaintextMock.mockImplementation(() => {
+      throw new Error("secret audit metadata may not include plaintext fields");
+    });
+
+    const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => undefined);
+    const tools = new Map<string, any>();
+    kbExtension({ registerTool: (d: any) => tools.set(d.name, d), registerCommand: vi.fn(), registerShortcut: vi.fn(), registerFlag: vi.fn(), on: vi.fn() } as any);
+    const tool = tools.get("fn_secret_get");
+
+    const result = await tool.execute("id", { key: "API_KEY" }, undefined, undefined, { cwd: process.cwd(), agentId: "agent-1", runId: "run-1" });
+    expect(result.details.value).toBe("secret-value");
+    expect(recordRunAuditEventMock).not.toHaveBeenCalled();
+    warnSpy.mockRestore();
+  });
+
   it("returns denied for deny policy and not found when missing", async () => {
     const tools = new Map<string, any>();
     kbExtension({ registerTool: (d: any) => tools.set(d.name, d), registerCommand: vi.fn(), registerShortcut: vi.fn(), registerFlag: vi.fn(), on: vi.fn() } as any);

packages/cli/src/extension.ts

@@ -42,6 +42,7 @@ import {
   ExperimentFinalizeStateError,
   type FinalizePlanOverride,
   fetchWebContent,
+  assertNoSecretPlaintext,
 } from "@fusion/engine";
 import * as dashboard from "@fusion/dashboard";
 import { resolve, basename, extname, join } from "node:path";
@@ -121,15 +122,20 @@ function emitSecretAudit(
   metadata?: Record<string, unknown>,
 ): void {
   if (!ctx.runId || !ctx.agentId) return;
-  store.recordRunAuditEvent({
-    runId: ctx.runId,
-    agentId: ctx.agentId,
-    taskId: ctx.taskId,
-    domain: "filesystem",
-    mutationType,
-    target,
-    metadata,
-  });
+  try {
+    assertNoSecretPlaintext(metadata);
+    store.recordRunAuditEvent({
+      runId: ctx.runId,
+      agentId: ctx.agentId,
+      taskId: ctx.taskId,
+      domain: "filesystem",
+      mutationType,
+      target,
+      metadata,
+    });
+  } catch (error) {
+    console.warn("[fusion-extension] secret audit emission skipped", error);
+  }
 }
 
 /**