fix(message): authorize fallback broadcast provider

src/agents/tools/message-tool.test.ts

@@ -404,6 +404,7 @@ function createChannelPlugin(params: {
   config?: Partial<ChannelPlugin["config"]>;
   message?: ChannelMessageAdapterShape;
   messaging?: ChannelPlugin["messaging"];
+  outbound?: ChannelPlugin["outbound"];
 }): ChannelPlugin {
   return {
     id: params.id as ChannelPlugin["id"],
@@ -423,6 +424,7 @@ function createChannelPlugin(params: {
     },
     ...(params.message ? { message: params.message } : {}),
     ...(params.messaging ? { messaging: params.messaging } : {}),
+    ...(params.outbound ? { outbound: params.outbound } : {}),
     actions: {
       describeMessageTool:
         params.describeMessageTool ??
@@ -1771,6 +1773,44 @@ describe("message tool secret scoping", () => {
       broadcastChannel: "slack",
       broadcastTargets: ["slack:channel:one", "slack:channel:two"],
     },
+    {
+      name: "delegated fallback-resolved current-provider broadcast",
+      channel: "googlechat",
+      accountId: "alternate",
+      requesterAccountId: "current",
+      trusted: true,
+      origin: undefined,
+      rejected: true,
+      broadcast: true,
+      broadcastChannel: "last",
+      broadcastTargets: ["googlechat:spaces/current"],
+    },
+    {
+      name: "delegated fallback-resolved broadcast with matching current account",
+      channel: "googlechat",
+      accountId: "current",
+      requesterAccountId: "current",
+      trusted: true,
+      origin: undefined,
+      rejected: false,
+      broadcast: true,
+      broadcastChannel: "last",
+      broadcastTargets: ["googlechat:spaces/current"],
+      expectedRunnerChannel: "googlechat",
+    },
+    {
+      name: "direct fallback-resolved broadcast with alternate account",
+      channel: "googlechat",
+      accountId: "alternate",
+      requesterAccountId: undefined,
+      trusted: false,
+      origin: "direct-operator" as const,
+      rejected: false,
+      broadcast: true,
+      broadcastChannel: "last",
+      broadcastTargets: ["googlechat:spaces/current"],
+      expectedRunnerChannel: "googlechat",
+    },
     {
       name: "delegated channel-less broadcast with matching current account",
       channel: "googlechat",
@@ -1806,6 +1846,7 @@ describe("message tool secret scoping", () => {
           listAccountIds: () => ["current", "alternate"],
           resolveAccount: () => ({ enabled: true }),
         },
+        outbound: { deliveryMode: "direct", sendText: vi.fn() as never },
       });
       const slackPlugin = createChannelPlugin({
         id: "slack",
@@ -1817,6 +1858,7 @@ describe("message tool secret scoping", () => {
           listAccountIds: () => ["alternate"],
           resolveAccount: () => ({ enabled: true }),
         },
+        outbound: { deliveryMode: "direct", sendText: vi.fn() as never },
       });
       setActivePluginRegistry(
         createTestRegistry([
@@ -1905,6 +1947,9 @@ describe("message tool secret scoping", () => {
       await expect(invocation).resolves.toBeDefined();
       expect(mocks.resolveCommandSecretRefsViaGateway).toHaveBeenCalledOnce();
       expect(mocks.runMessageAction).toHaveBeenCalledOnce();
+      if ("expectedRunnerChannel" in testCase) {
+        expect(firstRunMessageActionInput()?.params?.channel).toBe(testCase.expectedRunnerChannel);
+      }
     },
   );
 

src/agents/tools/message-tool.ts

@@ -51,6 +51,7 @@ import {
 import { resolveMessageActionTurnCapability } from "../../gateway/message-action-turn-capability.js";
 import { createAbortError } from "../../infra/abort-signal.js";
 import { sha256Base64UrlPrefix } from "../../infra/crypto-digest.js";
+import { resolveMessageChannelSelection } from "../../infra/outbound/channel-selection.js";
 import {
   resolveMessageBroadcastAccountPlan,
   validateExplicitMessageAccountSelection,
@@ -1589,12 +1590,26 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
       const gatewayOpts = readGatewayCallOptions(params);
       const rawConfig = options?.config ?? loadConfigForTool();
       const requestedAccountId = readStringParam(params, "accountId");
-      const requestedScope = resolveMessageSecretScope({
-        channel: params.channel,
-        target: params.target,
-        targets: params.targets,
+      validateExplicitMessageAccountSelection({
+        cfg: rawConfig,
         accountId: requestedAccountId,
+        checkResolvedAccount: false,
       });
+      const requestedBroadcastChannel = normalizeOptionalLowercaseString(params.channel);
+      if (
+        action === "broadcast" &&
+        requestedBroadcastChannel &&
+        requestedBroadcastChannel !== "all"
+      ) {
+        // Authorize and execute the same canonical provider. Otherwise an unavailable
+        // hint can fall back to the current provider only after account authorization.
+        const selection = await resolveMessageChannelSelection({
+          cfg: rawConfig,
+          channel: requestedBroadcastChannel,
+          fallbackChannel: effectiveCurrentChannel.currentChannelProvider,
+        });
+        params.channel = selection.channel;
+      }
       const scope = resolveMessageSecretScope({
         channel: params.channel,
         target: params.target,
@@ -1603,7 +1618,6 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
         accountId: requestedAccountId,
         fallbackAccountId: agentAccountId,
       });
-      const requestedBroadcastChannel = normalizeOptionalLowercaseString(params.channel);
       // Broadcast execution only narrows on an explicit non-all channel. Target
       // prefixes cannot authorize fewer providers than the runner will execute.
       const unscopedExplicitBroadcast =
@@ -1627,12 +1641,7 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
         explicitAccountId,
         selectedChannels: broadcastAccountPlan
           ? broadcastAccountPlan.candidateChannels
-          : [
-              requestedScope.channel ??
-                (action === "broadcast"
-                  ? undefined
-                  : trustedTurnContext?.toolContext?.currentChannelProvider),
-            ],
+          : [scope.channel],
         trustedCurrentChannel: trustedTurnContext?.toolContext?.currentChannelProvider,
         trustedRequesterAccountId: trustedTurnContext?.requesterAccountId,
         hasTrustedTurnContext: trustedTurnContext !== undefined,