feat(gateway): support per-channel and per-session queue policy overrides

src/gateway/handlers/agent.test.ts

@@ -124,3 +124,62 @@ describe('createAgentHandlers command fast-path', () => {
     expect(((sent[0] as GatewayEvent).data as { content: string }).content).toBe('agent response');
   });
 });
+
+describe('createAgentHandlers queue policy resolution', () => {
+  it('passes resolved per-request queue policy into lane enqueue', async () => {
+    const mockAgent = {
+      process: vi.fn(async () => 'ok'),
+      getUsage: vi.fn(() => ({
+        primary: { inputTokens: 0, outputTokens: 0, calls: 0 },
+        delegation: {},
+        total: { inputTokens: 0, outputTokens: 0, calls: 0, estimatedCost: 0 },
+      })),
+      getModelTier: vi.fn(() => 'default'),
+      setModelTier: vi.fn(),
+      compact: vi.fn(async () => null),
+      reset: vi.fn(),
+      setOnToolUse: vi.fn(),
+    };
+
+    const sessionBridge = {
+      getAgent: vi.fn(() => mockAgent),
+      getSessionId: vi.fn(() => 'ws:s1'),
+      setBusy: vi.fn(),
+      setOnToolUse: vi.fn(),
+      isBusy: vi.fn(() => false),
+    };
+
+    const laneQueue = {
+      enqueue: vi.fn(async (_laneId: string, work: () => Promise<unknown>) => work()),
+      cancel: vi.fn(),
+    } as unknown as LaneQueue;
+
+    const resolveQueuePolicy = vi.fn(() => ({ mode: 'steer' as const, cap: 3 }));
+
+    const handlers = createAgentHandlers({
+      sessionBridge: sessionBridge as unknown as AgentHandlerDeps['sessionBridge'],
+      laneQueue,
+      resolveQueuePolicy,
+    });
+
+    const sent: OutboundMessage[] = [];
+    const send = vi.fn((msg: OutboundMessage) => sent.push(msg));
+
+    await handlers['agent.send']({
+      id: 1,
+      method: 'agent.send',
+      params: { message: 'hello', connectionId: 'conn-1' },
+    }, send);
+
+    expect(resolveQueuePolicy).toHaveBeenCalledWith({
+      laneId: 'ws:s1',
+      sessionId: 'ws:s1',
+      connectionId: 'conn-1',
+      channel: 'ws',
+    });
+    expect((laneQueue.enqueue as unknown as ReturnType<typeof vi.fn>).mock.calls[0][2]).toEqual({
+      mode: 'steer',
+      cap: 3,
+    });
+  });
+});

src/gateway/handlers/agent.ts

@@ -3,6 +3,7 @@ import type { SendFn } from '../router.js';
 import { makeEvent, makeError, ErrorCode } from '../protocol.js';
 import type { SessionBridge } from '../session-bridge.js';
 import type { LaneQueue } from '../lane-queue.js';
+import type { LaneQueueConfig } from '../lane-queue.js';
 import type { MetricsCollector } from '../metrics.js';
 import type { Attachment } from '../../channels/types.js';
 import type { SessionManager } from '../../session/manager.js';
@@ -14,6 +15,12 @@ import { randomUUID } from 'crypto';
 export interface AgentHandlerDeps {
   sessionBridge: SessionBridge;
   laneQueue: LaneQueue;
+  resolveQueuePolicy?: (ctx: {
+    laneId: string;
+    sessionId?: string;
+    connectionId: string;
+    channel: string;
+  }) => Partial<LaneQueueConfig> | undefined;
   metrics?: MetricsCollector;
   sessionManager?: SessionManager;
   commandRegistry?: CommandRegistry;
@@ -48,6 +55,7 @@ export function createAgentHandlers(deps: AgentHandlerDeps) {
       // Falls back to connectionId if session lookup fails (shouldn't happen).
       const sessionId = deps.sessionBridge.getSessionId(connectionId);
       const laneId = sessionId ?? connectionId;
+      const channel = sessionId?.split(':', 1)[0] ?? 'ws';
 
       // Enqueue the work — if the lane is idle it runs immediately,
       // otherwise it waits for earlier requests on the same session to finish.
@@ -312,7 +320,7 @@ export function createAgentHandlers(deps: AgentHandlerDeps) {
           deps.sessionBridge.setOnToolUse(connectionId, undefined);
           deps.metrics?.endRequest(requestId);
         }
-      });
+      }, deps.resolveQueuePolicy?.({ laneId, sessionId, connectionId, channel }));
     },
 
     'agent.cancel': async (request: GatewayRequest): Promise<OutboundMessage> => {

src/gateway/lane-queue.test.ts

@@ -248,4 +248,23 @@ describe('LaneQueue', () => {
     await expect(p1).resolves.toBe('active');
     await expect(p3).resolves.toBe('new-pending');
   });
+
+  it('supports per-enqueue policy overrides', async () => {
+    const queue = new LaneQueue({ mode: 'collect', cap: 10, overflow: 'drop_old' });
+    let resolveFirst!: () => void;
+    const firstBlocks = new Promise<void>((r) => { resolveFirst = r; });
+
+    const p1 = queue.enqueue('lane-a', async () => {
+      await firstBlocks;
+      return 'active';
+    });
+    const p2 = queue.enqueue('lane-a', async () => 'old-pending', { mode: 'steer' });
+    const p3 = queue.enqueue('lane-a', async () => 'latest-pending', { mode: 'steer' });
+
+    await expect(p2).rejects.toThrow('Superseded by newer request');
+    resolveFirst();
+
+    await expect(p1).resolves.toBe('active');
+    await expect(p3).resolves.toBe('latest-pending');
+  });
 });

src/gateway/lane-queue.ts

@@ -47,7 +47,8 @@ export class LaneQueue {
    * Returns a promise that resolves with the work's return value
    * once it has been executed (which may be immediately if the lane is idle).
    */
-  async enqueue<T>(laneId: string, work: () => Promise<T>): Promise<T> {
+  async enqueue<T>(laneId: string, work: () => Promise<T>, policy?: Partial<LaneQueueConfig>): Promise<T> {
+    const effective = this.resolvePolicy(policy);
     let lane = this.lanes.get(laneId);
     if (!lane) {
       lane = { active: false, queue: [] };
@@ -65,12 +66,12 @@ export class LaneQueue {
       }
     }
 
-    if (this.config.mode === 'steer' || this.config.mode === 'interrupt') {
+    if (effective.mode === 'steer' || effective.mode === 'interrupt') {
       this.rejectPending(lane, 'Superseded by newer request');
     }
 
-    if (lane.queue.length >= this.config.cap) {
-      if (this.config.overflow === 'drop_new') {
+    if (lane.queue.length >= effective.cap) {
+      if (effective.overflow === 'drop_new') {
         return Promise.reject(new Error('Lane queue full (drop_new)'));
       }
       // drop_old
@@ -131,6 +132,14 @@ export class LaneQueue {
     }
   }
 
+  private resolvePolicy(policy?: Partial<LaneQueueConfig>): LaneQueueConfig {
+    return {
+      mode: policy?.mode ?? this.config.mode,
+      cap: Math.max(1, policy?.cap ?? this.config.cap),
+      overflow: policy?.overflow ?? this.config.overflow,
+    };
+  }
+
   /**
    * Process the next queued entry for a lane (called after current work finishes).
    * Runs asynchronously so the caller's finally block completes first.

src/gateway/server.ts

@@ -85,7 +85,12 @@ export interface GatewayServerConfig {
     maxViolations?: number;
     violationWindowMs?: number;
   };
-  queue?: Partial<LaneQueueConfig>;
+  queue?: Partial<LaneQueueConfig> & {
+    overrides?: {
+      channels?: Record<string, Partial<LaneQueueConfig>>;
+      sessions?: Record<string, Partial<LaneQueueConfig>>;
+    };
+  };
   /** Optional pairing manager for DM pairing code management via gateway. */
   pairingManager?: PairingManager;
   memoryStore?: MemoryStore;
@@ -199,6 +204,16 @@ export class GatewayServer {
     const agentHandlers = createAgentHandlers({
       sessionBridge: this.sessionBridge,
       laneQueue: this.laneQueue,
+      resolveQueuePolicy: ({ sessionId, channel }) => {
+        const sessionPolicy = sessionId
+          ? this.config.queue?.overrides?.sessions?.[sessionId]
+          : undefined;
+        if (sessionPolicy) {
+          return sessionPolicy;
+        }
+
+        return this.config.queue?.overrides?.channels?.[channel];
+      },
       metrics: this.metrics,
       sessionManager: this.config.sessionManager,
       commandRegistry: this.config.commandRegistry,