fix(tool-projection): expose host_file_* on cross-client transports when capable client connected

assistant/src/daemon/__tests__/conversation-tool-setup.test.ts

@@ -19,29 +19,28 @@
  * host_file_* are filtered out for chrome-extension regardless of the
  * hasNoClient flag.
  *
- * Cross-client exception (Phase 1): host_bash is allowed for non-host-proxy
- * interfaces (e.g. "web") when at least one host_bash-capable client is
- * connected via the event hub. host_file_* and host_browser remain filtered
- * regardless (Phase 2).
+ * Cross-client exception: tools whose capabilities are in
+ * CROSS_CLIENT_EXPOSED_CAPABILITIES (host_bash, host_file) are allowed for
+ * non-host-proxy interfaces (e.g. "web") when at least one capable client
+ * is connected via the event hub. host_browser is excluded (chrome-extension
+ * is its own executor; web turns have no CDP target model).
  */
 
 import { beforeEach, describe, expect, mock, test } from "bun:test";
 
 // ── Module-level mocks ─────────────────────────────────────────────
 
-// Control how many host_bash-capable clients the hub reports.
-let mockHostBashClientCount = 0;
+// Control how many capable clients the hub reports per capability.
+const mockClientCountByCapability = new Map<string, number>();
 
 mock.module("../../runtime/assistant-event-hub.js", () => ({
   assistantEventHub: {
     listClientsByCapability: (cap: string) => {
-      if (cap === "host_bash") {
-        return Array.from({ length: mockHostBashClientCount }, (_, i) => ({
-          clientId: `mock-client-${i}`,
-          capabilities: ["host_bash"],
-        }));
-      }
-      return [];
+      const count = mockClientCountByCapability.get(cap) ?? 0;
+      return Array.from({ length: count }, (_, i) => ({
+        clientId: `mock-${cap}-client-${i}`,
+        capabilities: [cap],
+      }));
     },
   },
   broadcastMessage: () => {},
@@ -72,7 +71,7 @@ function makeCtx(
 }
 
 beforeEach(() => {
-  mockHostBashClientCount = 0;
+  mockClientCountByCapability.clear();
 });
 
 describe("isToolActiveForContext — host tool capability gating", () => {
@@ -213,7 +212,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
   test("host_bash is active for web transport when a host_bash-capable client is connected", () => {
     // Cross-client path: a web turn should see host_bash when a macOS client
     // with host_bash capability is connected via the event hub.
-    mockHostBashClientCount = 1;
+    mockClientCountByCapability.set("host_bash", 1);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -224,7 +223,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
 
   test("host_bash is NOT active for web transport when no capable client is connected", () => {
     // No cross-client fallback: hub has no host_bash-capable subscribers.
-    mockHostBashClientCount = 0;
+    mockClientCountByCapability.set("host_bash", 0);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -233,11 +232,11 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
     ).toBe(false);
   });
 
-  test("host_file_read is NOT active for web transport even when a capable client is connected (Phase 2 gate)", () => {
-    // The cross-client exception is scoped to host_bash only.
-    // host_file_* remain filtered for non-host-proxy interfaces regardless
-    // of connected clients until Phase 2 lands.
-    mockHostBashClientCount = 1;
+  test("host_file_read is NOT active for web transport when only a host_bash client is connected", () => {
+    // The cross-client exception is per-capability: a host_bash-capable
+    // client in the hub does not satisfy host_file's exposure check, since
+    // listClientsByCapability is queried with the tool's actual capability.
+    mockClientCountByCapability.set("host_bash", 1);
     expect(
       isToolActiveForContext(
         "host_file_read",
@@ -249,7 +248,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
   test("host_bash for macos transport is unaffected by the cross-client exception", () => {
     // macos natively supports host_bash via host proxy — the supportsHostProxy
     // check passes, so the cross-client branch is never reached.
-    mockHostBashClientCount = 0;
+    mockClientCountByCapability.set("host_bash", 0);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -262,7 +261,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
     // Even with a capable client in the hub, the macos SSE path takes
     // precedence — it passes the supportsHostProxy check, bypasses the
     // cross-client branch, and reaches the hasNoClient gate.
-    mockHostBashClientCount = 1;
+    mockClientCountByCapability.set("host_bash", 1);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -275,7 +274,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
     // Security boundary: chrome-extension only gets host_browser. The
     // cross-client exception explicitly excludes chrome-extension transport
     // regardless of how many host_bash-capable clients are in the hub.
-    mockHostBashClientCount = 1;
+    mockClientCountByCapability.set("host_bash", 1);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -287,7 +286,7 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
   test("host_bash is NOT active for web transport when hasNoClient is true (no approval UI)", () => {
     // hasNoClient gate: no interactive approval UI available for this turn.
     // Cross-client exception must not bypass this gate.
-    mockHostBashClientCount = 1;
+    mockClientCountByCapability.set("host_bash", 1);
     expect(
       isToolActiveForContext(
         "host_bash",
@@ -297,6 +296,68 @@ describe("isToolActiveForContext — cross-client exception (Phase 1: host_bash)
   });
 });
 
+describe("isToolActiveForContext — cross-client exposure for host_file_*", () => {
+  const HOST_FILE_TOOLS = [
+    "host_file_read",
+    "host_file_write",
+    "host_file_edit",
+    "host_file_transfer",
+  ] as const;
+
+  for (const tool of HOST_FILE_TOOLS) {
+    test(`${tool} is exposed for web transport when a host_file client is connected`, () => {
+      mockClientCountByCapability.set("host_file", 1);
+      expect(
+        isToolActiveForContext(
+          tool,
+          makeCtx({ hasNoClient: false, transportInterface: "web" }),
+        ),
+      ).toBe(true);
+    });
+
+    test(`${tool} is NOT exposed for web when no host_file client is connected`, () => {
+      mockClientCountByCapability.set("host_file", 0);
+      expect(
+        isToolActiveForContext(
+          tool,
+          makeCtx({ hasNoClient: false, transportInterface: "web" }),
+        ),
+      ).toBe(false);
+    });
+
+    test(`${tool} is NOT exposed for chrome-extension (security boundary)`, () => {
+      mockClientCountByCapability.set("host_file", 1);
+      expect(
+        isToolActiveForContext(
+          tool,
+          makeCtx({ hasNoClient: true, transportInterface: "chrome-extension" }),
+        ),
+      ).toBe(false);
+    });
+
+    test(`${tool} is NOT exposed when hasNoClient is true (no approval UI)`, () => {
+      mockClientCountByCapability.set("host_file", 1);
+      expect(
+        isToolActiveForContext(
+          tool,
+          makeCtx({ hasNoClient: true, transportInterface: "web" }),
+        ),
+      ).toBe(false);
+    });
+  }
+
+  test("listClientsByCapability is queried with the actual capability, not host_bash (regression guard for D5 latent bug)", () => {
+    mockClientCountByCapability.set("host_bash", 0);
+    mockClientCountByCapability.set("host_file", 1);
+    expect(
+      isToolActiveForContext(
+        "host_file_transfer",
+        makeCtx({ hasNoClient: false, transportInterface: "web" }),
+      ),
+    ).toBe(true);
+  });
+});
+
 describe("HOST_TOOL_NAMES derivation", () => {
   test("HOST_TOOL_NAMES is derived from HOST_TOOL_TO_CAPABILITY", () => {
     // Sanity check: every tool in the names set has a capability mapping.

assistant/src/daemon/conversation-tool-setup.ts

@@ -350,6 +350,29 @@ export const HOST_TOOL_TO_CAPABILITY = new Map<string, HostProxyCapability>([
 // Derived from HOST_TOOL_TO_CAPABILITY so the invariant "every host tool has
 // a capability mapping" is a structural fact — no runtime assertion needed.
 export const HOST_TOOL_NAMES = new Set(HOST_TOOL_TO_CAPABILITY.keys());
+/**
+ * Capabilities eligible for cross-client exposure on non-host-proxy
+ * transports (e.g. web, ios routing to a connected macOS client).
+ * Adding a capability here exposes ALL tools that map to it (per
+ * HOST_TOOL_TO_CAPABILITY) on non-host-proxy transports — the daemon then
+ * routes the actual invocation to the connected capable client via the
+ * proxy's targetClientId path.
+ *
+ * Inclusions:
+ * - host_bash (Phase 1, PR #29322)
+ * - host_file (Phases 2 & 3, PRs #29398 + #29440)
+ *
+ * Exclusions:
+ * - host_browser: chrome-extension is its own executor; web turns don't
+ *   have a CDP target model. Re-evaluate when host browser via macOS
+ *   host proxy ships (PR #27489).
+ * - host_app_control, host_cu: not in HOST_TOOL_TO_CAPABILITY
+ *   (skill-routed).
+ */
+const CROSS_CLIENT_EXPOSED_CAPABILITIES = new Set<HostProxyCapability>([
+  "host_bash",
+  "host_file",
+]);
 const CLIENT_CAPABILITY_TOOL_NAMES = new Set(["app_open"]);
 const PLATFORM_TOOL_NAMES = new Set(["request_system_permission"]);
 
@@ -384,16 +407,22 @@ export function isToolActiveForContext(
     // Per-capability check is authoritative for structural support: if the
     // transport cannot service this capability, the tool is filtered out.
     if (transport && capability && !supportsHostProxy(transport, capability)) {
-      // Cross-client exception: allow host_bash for non-host-proxy interfaces when
-      // at least one capable client is connected via the event hub.
-      // Only applies to host_bash (not host_file, host_cu, host_browser — Phase 2).
-      // Excludes chrome-extension (security boundary: extension only gets host_browser)
-      // and hasNoClient turns (no interactive approval UI available).
+      // Cross-client exception: allow host tools whose capabilities have
+      // cross-client routing infrastructure (Phases 1–3) to be exposed for
+      // non-host-proxy transports (e.g. "web", "ios") when at least one
+      // capable client is connected via the event hub. Members of
+      // CROSS_CLIENT_EXPOSED_CAPABILITIES (host_bash, host_file) qualify;
+      // host_browser is intentionally excluded (chrome-extension is its
+      // own executor and web turns don't have a CDP target model).
+      // chrome-extension transport is excluded as a security boundary
+      // (extension only gets host_browser); hasNoClient turns are excluded
+      // (no interactive approval UI available).
       if (
-        capability === "host_bash" &&
+        capability &&
+        CROSS_CLIENT_EXPOSED_CAPABILITIES.has(capability) &&
         transport !== "chrome-extension" &&
         !ctx.hasNoClient &&
-        assistantEventHub.listClientsByCapability("host_bash").length > 0
+        assistantEventHub.listClientsByCapability(capability).length > 0
       ) {
         return true;
       }