refactor: centralize gateway module and address review fixes

Move the gateway runtime files into a dedicated core/gateway module and fix follow-up issues in session deletion, history import batching, message IDs, and legacy thread parsing.

Fixes #253

Co-authored-by: Codex <noreply@openai.com>

packages/coding-agent/src/core/gateway/helpers.ts

@@ -1,4 +1,4 @@
-import type { AgentSession } from "./agent-session.js";
+import type { AgentSession } from "../agent-session.js";
 
 export function extractMessageText(message: { content: unknown }): string {
   if (!Array.isArray(message.content)) {

packages/coding-agent/src/core/gateway/index.ts

@@ -0,0 +1,19 @@
+export {
+  createGatewaySessionManager,
+  GatewayRuntime,
+  getActiveGatewayRuntime,
+  sanitizeSessionKey,
+  setActiveGatewayRuntime,
+} from "./runtime.js";
+export type {
+  ChannelStatus,
+  GatewayConfig,
+  GatewayMessageRequest,
+  GatewayMessageResult,
+  GatewayRuntimeOptions,
+  GatewaySessionFactory,
+  GatewaySessionSnapshot,
+  HistoryMessage,
+  HistoryPart,
+  ModelInfo,
+} from "./runtime.js";

packages/coding-agent/src/core/gateway/internal-types.ts

@@ -1,9 +1,9 @@
-import type { AgentSession } from "./agent-session.js";
+import type { AgentSession } from "../agent-session.js";
 import type {
   GatewayMessageRequest,
   GatewayMessageResult,
   GatewaySessionSnapshot,
-} from "./gateway-runtime-types.js";
+} from "./types.js";
 
 export interface GatewayQueuedMessage {
   request: GatewayMessageRequest;

packages/coding-agent/src/core/gateway/runtime.ts

@@ -8,18 +8,15 @@ import { rm } from "node:fs/promises";
 import { join } from "node:path";
 import { URL } from "node:url";
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
-import type { AgentSession, AgentSessionEvent } from "./agent-session.js";
-import {
-  extractMessageText,
-  getLastAssistantText,
-} from "./gateway-runtime-helpers.js";
+import type { AgentSession, AgentSessionEvent } from "../agent-session.js";
+import { extractMessageText, getLastAssistantText } from "./helpers.js";
 import {
   type GatewayEvent,
   type GatewayQueuedMessage,
   HttpError,
   type ManagedGatewaySession,
-} from "./gateway-runtime-internal-types.js";
-import { sanitizeSessionKey } from "./gateway-session-manager.js";
+} from "./internal-types.js";
+import { sanitizeSessionKey } from "./session-manager.js";
 import type {
   ChannelStatus,
   GatewayConfig,
@@ -31,8 +28,8 @@ import type {
   HistoryMessage,
   HistoryPart,
   ModelInfo,
-} from "./gateway-runtime-types.js";
-import type { Settings } from "./settings-manager.js";
+} from "./types.js";
+import type { Settings } from "../settings-manager.js";
 import {
   createVercelStreamListener,
   errorVercelStream,
@@ -42,7 +39,7 @@ import {
 export {
   createGatewaySessionManager,
   sanitizeSessionKey,
-} from "./gateway-session-manager.js";
+} from "./session-manager.js";
 export type {
   ChannelStatus,
   GatewayConfig,
@@ -54,7 +51,7 @@ export type {
   HistoryMessage,
   HistoryPart,
   ModelInfo,
-} from "./gateway-runtime-types.js";
+} from "./types.js";
 
 let activeGatewayRuntime: GatewayRuntime | null = null;
 
@@ -966,7 +963,7 @@ export class GatewayRuntime {
     const managed = await this.ensureSession(sessionKey);
     const rawMessages = managed.session.messages;
     const messages: HistoryMessage[] = [];
-    for (const msg of rawMessages) {
+    for (const [index, msg] of rawMessages.entries()) {
       if (
         msg.role !== "user" &&
         msg.role !== "assistant" &&
@@ -975,7 +972,7 @@ export class GatewayRuntime {
         continue;
       }
       messages.push({
-        id: `${msg.timestamp}-${msg.role}`,
+        id: `${msg.timestamp}-${msg.role}-${index}`,
         role: msg.role,
         parts: this.messageContentToParts(msg),
         timestamp: msg.timestamp,
@@ -1006,7 +1003,8 @@ export class GatewayRuntime {
     if (sessionKey === this.primarySessionKey) {
       throw new HttpError(400, "Cannot delete primary session");
     }
-    const managed = await this.ensureSession(sessionKey);
+    const managed = this.sessions.get(sessionKey);
+    if (managed) {
       if (managed.processing) {
         await managed.session.abort();
       }
@@ -1014,6 +1012,7 @@ export class GatewayRuntime {
       managed.unsubscribe();
       managed.session.dispose();
       this.sessions.delete(sessionKey);
+    }
     await rm(this.getGatewaySessionDir(sessionKey), {
       recursive: true,
       force: true,

packages/coding-agent/src/core/gateway/session-manager.ts

@@ -1,5 +1,5 @@
 import { join } from "node:path";
-import { SessionManager } from "./session-manager.js";
+import { SessionManager } from "../session-manager.js";
 
 export function sanitizeSessionKey(sessionKey: string): string {
   return sessionKey.replace(/[^a-zA-Z0-9._-]/g, "_");

packages/coding-agent/src/core/gateway/types.ts

@@ -1,5 +1,5 @@
-import type { AgentSession } from "./agent-session.js";
 import type { ImageContent } from "@mariozechner/pi-ai";
+import type { AgentSession } from "../agent-session.js";
 
 export interface GatewayConfig {
   bind: string;

packages/coding-agent/src/core/gateway/vercel-ai-stream.ts

@@ -1,6 +1,6 @@
 import { randomUUID } from "node:crypto";
 import type { ServerResponse } from "node:http";
-import type { AgentSessionEvent } from "./agent-session.js";
+import type { AgentSessionEvent } from "../agent-session.js";
 
 /**
  * Write a single Vercel AI SDK v5+ SSE chunk to the response.

packages/coding-agent/src/index.ts

@@ -156,7 +156,7 @@ export {
   getActiveGatewayRuntime,
   sanitizeSessionKey,
   setActiveGatewayRuntime,
-} from "./core/gateway-runtime.js";
+} from "./core/gateway/index.js";
 export { convertToLlm } from "./core/messages.js";
 export { ModelRegistry } from "./core/model-registry.js";
 export type {

packages/coding-agent/src/main.ts

@@ -22,7 +22,7 @@ import { APP_NAME, getAgentDir, getModelsPath, VERSION } from "./config.js";
 import { AuthStorage } from "./core/auth-storage.js";
 import { exportFromFile } from "./core/export-html/index.js";
 import type { LoadExtensionsResult } from "./core/extensions/index.js";
-import { createGatewaySessionManager } from "./core/gateway-runtime.js";
+import { createGatewaySessionManager } from "./core/gateway/index.js";
 import { KeybindingsManager } from "./core/keybindings.js";
 import { ModelRegistry } from "./core/model-registry.js";
 import {

packages/coding-agent/src/modes/daemon-mode.ts

@@ -12,7 +12,7 @@ import {
   GatewayRuntime,
   type GatewaySessionFactory,
   setActiveGatewayRuntime,
-} from "../core/gateway-runtime.js";
+} from "../core/gateway/index.js";
 import type { GatewaySettings } from "../core/settings-manager.js";
 
 /**