fix(gateway): harden agent provider routing

src/agents/lanes.ts

@@ -0,0 +1,2 @@
+export const AGENT_LANE_NESTED = "nested" as const;
+export const AGENT_LANE_SUBAGENT = "subagent" as const;

src/agents/subagent-announce.ts

@@ -8,6 +8,8 @@ import {
   resolveStorePath,
 } from "../config/sessions.js";
 import { callGateway } from "../gateway/call.js";
+import { INTERNAL_MESSAGE_PROVIDER } from "../utils/message-provider.js";
+import { AGENT_LANE_NESTED } from "./lanes.js";
 import { readLatestAssistantReply, runAgentStep } from "./tools/agent-step.js";
 import { resolveAnnounceTarget } from "./tools/sessions-announce-target.js";
 import { isAnnounceSkip } from "./tools/sessions-send-helpers.js";
@@ -241,7 +243,8 @@ export async function runSubagentAnnounceFlow(params: {
       message: "Sub-agent announce step.",
       extraSystemPrompt: announcePrompt,
       timeoutMs: params.timeoutMs,
-      lane: "nested",
+      provider: INTERNAL_MESSAGE_PROVIDER,
+      lane: AGENT_LANE_NESTED,
     });
 
     if (

src/agents/tools/agent-step.ts

@@ -1,6 +1,8 @@
 import crypto from "node:crypto";
 
 import { callGateway } from "../../gateway/call.js";
+import { INTERNAL_MESSAGE_PROVIDER } from "../../utils/message-provider.js";
+import { AGENT_LANE_NESTED } from "../lanes.js";
 import { extractAssistantText, stripToolMessages } from "./sessions-helpers.js";
 
 export async function readLatestAssistantReply(params: {
@@ -34,8 +36,8 @@ export async function runAgentStep(params: {
       sessionKey: params.sessionKey,
       idempotencyKey: stepIdem,
       deliver: false,
-      provider: params.provider ?? "webchat",
-      lane: params.lane ?? "nested",
+      provider: params.provider ?? INTERNAL_MESSAGE_PROVIDER,
+      lane: params.lane ?? AGENT_LANE_NESTED,
       extraSystemPrompt: params.extraSystemPrompt,
     },
     timeoutMs: 10_000,

src/agents/tools/sessions-send-tool.ts

@@ -10,7 +10,11 @@ import {
   parseAgentSessionKey,
 } from "../../routing/session-key.js";
 import { SESSION_LABEL_MAX_LENGTH } from "../../sessions/session-label.js";
-import type { GatewayMessageProvider } from "../../utils/message-provider.js";
+import {
+  type GatewayMessageProvider,
+  INTERNAL_MESSAGE_PROVIDER,
+} from "../../utils/message-provider.js";
+import { AGENT_LANE_NESTED } from "../lanes.js";
 import { readLatestAssistantReply, runAgentStep } from "./agent-step.js";
 import type { AnyAgentTool } from "./common.js";
 import { jsonResult, readStringParam } from "./common.js";
@@ -297,8 +301,8 @@ export function createSessionsSendTool(opts?: {
         sessionKey: resolvedKey,
         idempotencyKey,
         deliver: false,
-        provider: "webchat",
-        lane: "nested",
+        provider: INTERNAL_MESSAGE_PROVIDER,
+        lane: AGENT_LANE_NESTED,
         extraSystemPrompt: agentMessageContext,
       };
       const requesterSessionKey = opts?.agentSessionKey;
@@ -362,7 +366,7 @@ export function createSessionsSendTool(opts?: {
                 message: incomingMessage,
                 extraSystemPrompt: replyPrompt,
                 timeoutMs: announceTimeoutMs,
-                lane: "nested",
+                lane: AGENT_LANE_NESTED,
               });
               if (!replyText || isReplySkip(replyText)) {
                 break;
@@ -388,7 +392,7 @@ export function createSessionsSendTool(opts?: {
             message: "Agent-to-agent announce step.",
             extraSystemPrompt: announcePrompt,
             timeoutMs: announceTimeoutMs,
-            lane: "nested",
+            lane: AGENT_LANE_NESTED,
           });
           if (
             announceTarget &&

src/agents/tools/sessions-spawn-tool.ts

@@ -11,6 +11,7 @@ import {
 } from "../../routing/session-key.js";
 import type { GatewayMessageProvider } from "../../utils/message-provider.js";
 import { resolveAgentConfig } from "../agent-scope.js";
+import { AGENT_LANE_SUBAGENT } from "../lanes.js";
 import { buildSubagentSystemPrompt } from "../subagent-announce.js";
 import { registerSubagentRun } from "../subagent-registry.js";
 import type { AnyAgentTool } from "./common.js";
@@ -174,7 +175,7 @@ export function createSessionsSpawnTool(opts?: {
             provider: opts?.agentProvider,
             idempotencyKey: childIdem,
             deliver: false,
-            lane: "subagent",
+            lane: AGENT_LANE_SUBAGENT,
             extraSystemPrompt: childSystemPrompt,
             timeout: runTimeoutSeconds > 0 ? runTimeoutSeconds : undefined,
             label: label || undefined,