feat(sidecars): add proxied sidecar tabs (#279)

## Summary - add SideCar support across the server and UI, including proxied tabs, picker/settings flows, and websocket-aware proxying - unify top-level tab handling so workspace instances and SideCars share the same tab model and navigation flows - limit SideCars to port-based services only, removing server-managed process control from the final API and UI --------- Co-authored-by: Shantur <shantur@Mac.home> Co-authored-by: Shantur <shantur@Shanturs-MacBook-Pro-M5.local>
2026-04-02 23:00:17 +01:00
parent 19a4c3df16
commit d0a0325d7e
47 changed files with 2139 additions and 218 deletions
--- a/packages/electron-app/electron/main/main.ts
+++ b/packages/electron-app/electron/main/main.ts
@@ -1,7 +1,7 @@
 import { app, BrowserView, BrowserWindow, nativeImage, session, shell } from "electron"
 import http from "node:http"
 import https from "node:https"
-import { existsSync } from "fs"
+import { existsSync, mkdirSync } from "fs"
 import { dirname, join } from "path"
 import { fileURLToPath } from "url"
 import { createApplicationMenu } from "./menu"
@@ -14,6 +14,31 @@ const mainDirname = dirname(mainFilename)

 const isMac = process.platform === "darwin"

+function configureDevStoragePaths() {
+  if (app.isPackaged) {
+    return
+  }
+
+  const appName = "CodeNomad"
+
+  try {
+    app.setName(appName)
+
+    const userDataPath = join(app.getPath("appData"), appName)
+    const sessionDataPath = join(userDataPath, "session-data")
+
+    mkdirSync(userDataPath, { recursive: true })
+    mkdirSync(sessionDataPath, { recursive: true })
+
+    app.setPath("userData", userDataPath)
+    app.setPath("sessionData", sessionDataPath)
+  } catch (error) {
+    console.warn("[cli] failed to configure dev storage paths", error)
+  }
+}
+
+configureDevStoragePaths()
+
 const cliManager = new CliProcessManager()
 let mainWindow: BrowserWindow | null = null
 let currentCliUrl: string | null = null
--- a/packages/server/src/api-types.ts
+++ b/packages/server/src/api-types.ts
@@ -170,6 +170,24 @@ export interface InstanceStreamEvent {
  [key: string]: unknown
 }

+export type SideCarKind = "port"
+
+export type SideCarPrefixMode = "strip" | "preserve"
+
+export type SideCarStatus = "running" | "stopped"
+
+export interface SideCar {
+  id: string
+  kind: SideCarKind
+  name: string
+  port: number
+  insecure: boolean
+  prefixMode: SideCarPrefixMode
+  status: SideCarStatus
+  createdAt: string
+  updatedAt: string
+}
+
 export interface BinaryRecord {
  id: string
  path: string
@@ -276,6 +294,8 @@ export type WorkspaceEventType =
  | "workspace.error"
  | "workspace.stopped"
  | "workspace.log"
+  | "sidecar.updated"
+  | "sidecar.removed"
  | "storage.configChanged"
  | "storage.stateChanged"
  | "instance.dataChanged"
@@ -288,6 +308,8 @@ export type WorkspaceEventPayload =
  | { type: "workspace.error"; workspace: WorkspaceDescriptor }
  | { type: "workspace.stopped"; workspaceId: string }
  | { type: "workspace.log"; entry: WorkspaceLogEntry }
+  | { type: "sidecar.updated"; sidecar: SideCar }
+  | { type: "sidecar.removed"; sidecarId: string }
  | { type: "storage.configChanged"; owner: SettingsOwner; value: SettingsBucket }
  | { type: "storage.stateChanged"; owner: SettingsOwner; value: SettingsBucket }
  | { type: "instance.dataChanged"; instanceId: string; data: InstanceData }
--- a/packages/server/src/auth/manager.ts
+++ b/packages/server/src/auth/manager.ts
@@ -104,13 +104,18 @@ export class AuthManager {
  }

  getSessionFromRequest(request: FastifyRequest): { username: string; sessionId: string } | null {
+    return this.getSessionFromHeaders(request.headers)
+  }
+
+  getSessionFromHeaders(headers: { cookie?: string | string[] | undefined }): { username: string; sessionId: string } | null {
    if (!this.authEnabled) {
      // When auth is disabled, treat all requests as authenticated.
      // We still return a stable username so callers can display it.
      return { username: this.init.username, sessionId: "auth-disabled" }
    }

-    const cookies = parseCookies(request.headers.cookie)
+    const cookieHeader = Array.isArray(headers.cookie) ? headers.cookie.join("; ") : headers.cookie
+    const cookies = parseCookies(cookieHeader)
    const sessionId = cookies[this.cookieName]
    const session = this.sessionManager.getSession(sessionId)
    if (!session) return null
--- a/packages/server/src/events/bus.ts
+++ b/packages/server/src/events/bus.ts
@@ -24,6 +24,8 @@ export class EventBus extends EventEmitter {
    this.on("workspace.error", handler)
    this.on("workspace.stopped", handler)
    this.on("workspace.log", handler)
+    this.on("sidecar.updated", handler)
+    this.on("sidecar.removed", handler)
    this.on("storage.configChanged", handler)
    this.on("storage.stateChanged", handler)
    this.on("instance.dataChanged", handler)
@@ -35,6 +37,8 @@ export class EventBus extends EventEmitter {
      this.off("workspace.error", handler)
      this.off("workspace.stopped", handler)
      this.off("workspace.log", handler)
+      this.off("sidecar.updated", handler)
+      this.off("sidecar.removed", handler)
      this.off("storage.configChanged", handler)
      this.off("storage.stateChanged", handler)
      this.off("instance.dataChanged", handler)
--- a/packages/server/src/index.ts
+++ b/packages/server/src/index.ts
@@ -24,6 +24,7 @@ import { resolveHttpsOptions } from "./server/tls"
 import { resolveNetworkAddresses, resolveRemoteAddresses } from "./server/network-addresses"
 import { startDevReleaseMonitor } from "./releases/dev-release-monitor"
 import { SpeechService } from "./speech/service"
+import { SideCarManager } from "./sidecars/manager"

 const require = createRequire(import.meta.url)

@@ -315,6 +316,11 @@ async function main() {
  const fileSystemBrowser = new FileSystemBrowser({ rootDir: options.rootDir, unrestricted: options.unrestrictedRoot })
  const instanceStore = new InstanceStore(configLocation.instancesDir)
  const speechService = new SpeechService(settings, logger.child({ component: "speech" }))
+  const sidecarManager = new SideCarManager({
+    settings,
+    eventBus,
+    logger: logger.child({ component: "sidecars" }),
+  })
  const instanceEventBridge = new InstanceEventBridge({
    workspaceManager,
    eventBus,
@@ -400,6 +406,7 @@ async function main() {
        serverMeta,
        instanceStore,
        speechService,
+        sidecarManager,
        authManager,
        uiStaticDir: uiResolution.uiStaticDir ?? DEFAULT_UI_STATIC_DIR,
        uiDevServerUrl: uiResolution.uiDevServerUrl,
@@ -421,6 +428,7 @@ async function main() {
        serverMeta,
        instanceStore,
        speechService,
+        sidecarManager,
        authManager,
        uiStaticDir: uiResolution.uiStaticDir ?? DEFAULT_UI_STATIC_DIR,
        uiDevServerUrl: undefined,
@@ -520,6 +528,12 @@ async function main() {
        logger.warn({ err: error }, "Instance event bridge shutdown failed")
      }

+      try {
+        await sidecarManager.shutdown()
+      } catch (error) {
+        logger.error({ err: error }, "SideCar manager shutdown failed")
+      }
+
      try {
        await workspaceManager.shutdown()
        logger.info("Workspace manager shutdown complete")
--- a/packages/server/src/server/http-server.ts
+++ b/packages/server/src/server/http-server.ts
@@ -3,7 +3,9 @@ import cors from "@fastify/cors"
 import fastifyStatic from "@fastify/static"
 import replyFrom from "@fastify/reply-from"
 import fs from "fs"
+import { connect as connectTcp, type Socket } from "net"
 import path from "path"
+import { connect as connectTls, type TLSSocket } from "tls"
 import { fetch } from "undici"
 import type { Logger } from "../logger"
 import { WorkspaceManager } from "../workspaces/manager"
@@ -23,6 +25,7 @@ import { registerBackgroundProcessRoutes } from "./routes/background-processes"
 import { registerWorktreeRoutes } from "./routes/worktrees"
 import { registerSpeechRoutes } from "./routes/speech"
 import { registerRemoteServerRoutes } from "./routes/remote-servers"
+import { registerSideCarRoutes } from "./routes/sidecars"
 import { ServerMeta } from "../api-types"
 import { InstanceStore } from "../storage/instance-store"
 import { BackgroundProcessManager } from "../background-processes/manager"
@@ -33,6 +36,7 @@ import type { SpeechService } from "../speech/service"
 import { ClientConnectionManager } from "../clients/connection-manager"
 import { PluginChannelManager } from "../plugins/channel"
 import { VoiceModeManager } from "../plugins/voice-mode"
+import type { SideCarManager } from "../sidecars/manager"

 interface HttpServerDeps {
  bindHost: string
@@ -48,6 +52,7 @@ interface HttpServerDeps {
  serverMeta: ServerMeta
  instanceStore: InstanceStore
  speechService: SpeechService
+  sidecarManager: SideCarManager
  authManager: AuthManager
  uiStaticDir: string
  uiDevServerUrl?: string
@@ -204,7 +209,7 @@ export function createHttpServer(deps: HttpServerDeps) {

    const session = deps.authManager.getSessionFromRequest(request)

-    const requiresAuthForApi = pathname.startsWith("/api/") || pathname.startsWith("/workspaces/")
+    const requiresAuthForApi = pathname.startsWith("/api/") || pathname.startsWith("/workspaces/") || pathname.startsWith("/sidecars/")
    if (requiresAuthForApi && !session) {
      // Allow OpenCode plugin -> CodeNomad calls with per-instance basic auth.
      const pluginMatch = pathname.match(/^\/workspaces\/([^/]+)\/plugin(?:\/|$)/)
@@ -273,6 +278,13 @@ export function createHttpServer(deps: HttpServerDeps) {
  })
  registerRemoteServerRoutes(app, { logger: apiLogger })
  registerSpeechRoutes(app, { speechService: deps.speechService })
+  registerSideCarRoutes(app, { sidecarManager: deps.sidecarManager })
+  registerSideCarProxyRoutes(app, { sidecarManager: deps.sidecarManager, logger: proxyLogger })
+  setupSideCarWebSocketProxy(app, {
+    sidecarManager: deps.sidecarManager,
+    authManager: deps.authManager,
+    logger: proxyLogger,
+  })
  registerPluginRoutes(app, {
    workspaceManager: deps.workspaceManager,
    eventBus: deps.eventBus,
@@ -355,6 +367,68 @@ interface InstanceProxyDeps {
  logger: Logger
 }

+interface SideCarProxyDeps {
+  sidecarManager: SideCarManager
+  logger: Logger
+}
+
+interface SideCarWebSocketProxyDeps extends SideCarProxyDeps {
+  authManager: AuthManager
+}
+
+function registerSideCarProxyRoutes(app: FastifyInstance, deps: SideCarProxyDeps) {
+  const proxyBaseHandler = async (
+    request: FastifyRequest<{ Params: { id: string } }>,
+    reply: FastifyReply,
+  ) => {
+    await proxySideCarRequest({
+      request,
+      reply,
+      sidecarManager: deps.sidecarManager,
+      logger: deps.logger,
+      pathSuffix: "",
+    })
+  }
+
+  const proxyWildcardHandler = async (
+    request: FastifyRequest<{ Params: { id: string; "*": string } }>,
+    reply: FastifyReply,
+  ) => {
+    await proxySideCarRequest({
+      request,
+      reply,
+      sidecarManager: deps.sidecarManager,
+      logger: deps.logger,
+      pathSuffix: request.params["*"] ?? "",
+    })
+  }
+
+  app.all("/sidecars/:id", proxyBaseHandler)
+  app.all("/sidecars/:id/*", proxyWildcardHandler)
+}
+
+function setupSideCarWebSocketProxy(app: FastifyInstance, deps: SideCarWebSocketProxyDeps) {
+  app.server.on("upgrade", (request, socket, head) => {
+    const rawUrl = request.url ?? "/"
+    const parsed = parseSideCarUpgradePath(rawUrl)
+    if (!parsed) {
+      return
+    }
+
+    void proxySideCarWebSocketUpgrade({
+      request,
+      socket: socket as Socket,
+      head,
+      sidecarId: parsed.sidecarId,
+      incomingPath: parsed.pathname,
+      search: parsed.search,
+      sidecarManager: deps.sidecarManager,
+      authManager: deps.authManager,
+      logger: deps.logger,
+    })
+  })
+}
+
 function registerInstanceProxyRoutes(app: FastifyInstance, deps: InstanceProxyDeps) {
  app.register(async (instance) => {
    instance.removeAllContentTypeParsers()
@@ -839,3 +913,281 @@ function buildProxyHeaders(headers: FastifyRequest["headers"]): Record<string, s
  }
  return result
 }
+
+async function proxySideCarRequest(args: {
+  request: FastifyRequest
+  reply: FastifyReply
+  sidecarManager: SideCarManager
+  logger: Logger
+  pathSuffix?: string
+}) {
+  const sidecarId = (args.request.params as { id?: string }).id ?? ""
+  const sidecar = await args.sidecarManager.get(sidecarId)
+  if (!sidecar) {
+    args.reply.code(404).send({ error: "SideCar not found" })
+    return
+  }
+
+  const pathname = (args.request.raw.url ?? args.request.url ?? "").split("?")[0] ?? ""
+  const queryIndex = (args.request.raw.url ?? args.request.url ?? "").indexOf("?")
+  const search = queryIndex >= 0 ? (args.request.raw.url ?? args.request.url ?? "").slice(queryIndex) : ""
+  const pathSuffix = args.pathSuffix ?? ""
+  const requestPath = pathSuffix ? `${args.sidecarManager.buildProxyBasePath(sidecarId)}/${pathSuffix.replace(/^\/+/, "")}` : args.sidecarManager.buildProxyBasePath(sidecarId)
+  const targetPath = args.sidecarManager.buildTargetPath(sidecarId, requestPath, search)
+  const targetOrigin = args.sidecarManager.buildTargetOrigin(sidecar)
+  const targetUrl = `${targetOrigin}${targetPath}`
+  args.logger.debug({ sidecarId: sidecar.id, targetUrl, pathname, prefixMode: sidecar.prefixMode }, "Proxying request to SideCar")
+
+  await args.reply.from(targetUrl, {
+    rewriteRequestHeaders: (_originalRequest, headers) =>
+      sanitizeSideCarProxyRequestHeaders(headers as Record<string, string | string[] | undefined>, targetOrigin),
+    rewriteHeaders: (headers) => rewriteSideCarResponseHeaders(headers, sidecarId, targetOrigin, sidecar.prefixMode),
+    onError: (reply, { error }) => {
+      args.logger.error({ sidecarId: sidecar.id, err: error, targetUrl }, "Failed to proxy SideCar request")
+      if (!reply.sent) {
+        reply.code(502).send({ error: "SideCar proxy failed" })
+      }
+    },
+  })
+}
+
+function parseSideCarUpgradePath(rawUrl: string): { sidecarId: string; pathname: string; search: string } | null {
+  let parsed: URL
+  try {
+    parsed = new URL(rawUrl, "http://localhost")
+  } catch {
+    return null
+  }
+
+  const match = parsed.pathname.match(/^\/sidecars\/([^/]+)(?:\/.*)?$/)
+  if (!match) {
+    return null
+  }
+
+  try {
+    return {
+      sidecarId: decodeURIComponent(match[1] ?? ""),
+      pathname: parsed.pathname,
+      search: parsed.search,
+    }
+  } catch {
+    return null
+  }
+}
+
+async function proxySideCarWebSocketUpgrade(args: {
+  request: import("http").IncomingMessage
+  socket: Socket
+  head: Buffer
+  sidecarId: string
+  incomingPath: string
+  search: string
+  sidecarManager: SideCarManager
+  authManager: AuthManager
+  logger: Logger
+}) {
+  const { request, socket, head, sidecarId, incomingPath, search, sidecarManager, authManager, logger } = args
+
+  if (!isWebSocketUpgradeRequest(request)) {
+    rejectUpgrade(socket, 400, "Bad Request")
+    return
+  }
+
+  const session = authManager.getSessionFromHeaders(request.headers)
+  if (!session) {
+    rejectUpgrade(socket, 401, "Unauthorized")
+    return
+  }
+
+  const sidecar = await sidecarManager.get(sidecarId)
+  if (!sidecar) {
+    rejectUpgrade(socket, 404, "Not Found")
+    return
+  }
+
+  const targetOrigin = sidecarManager.buildTargetOrigin(sidecar)
+  const targetPath = sidecarManager.buildTargetPath(sidecarId, incomingPath, search)
+  const targetUrl = new URL(`${targetOrigin}${targetPath}`)
+  logger.debug({ sidecarId, targetUrl: targetUrl.toString(), prefixMode: sidecar.prefixMode }, "Proxying websocket to SideCar")
+
+  const { socket: upstream, readyEvent } = createSideCarUpstreamSocket(targetUrl)
+
+  const closeBoth = () => {
+    if (!socket.destroyed) {
+      socket.destroy()
+    }
+    if (!upstream.destroyed) {
+      upstream.destroy()
+    }
+  }
+
+  upstream.once("error", (error) => {
+    logger.error({ sidecarId, err: error, targetUrl: targetUrl.toString() }, "Failed to proxy SideCar websocket")
+    rejectUpgrade(socket, 502, "Bad Gateway")
+    if (!upstream.destroyed) {
+      upstream.destroy()
+    }
+  })
+
+  socket.once("error", (error) => {
+    logger.debug({ sidecarId, err: error }, "SideCar websocket client socket errored")
+    if (!upstream.destroyed) {
+      upstream.destroy()
+    }
+  })
+
+  upstream.once(readyEvent, () => {
+    try {
+      upstream.write(buildSideCarWebSocketRequest(request, targetUrl))
+      if (head.length > 0) {
+        upstream.write(head)
+      }
+      upstream.pipe(socket)
+      socket.pipe(upstream)
+    } catch (error) {
+      logger.error({ sidecarId, err: error, targetUrl: targetUrl.toString() }, "Failed to forward SideCar websocket upgrade")
+      closeBoth()
+    }
+  })
+
+  upstream.once("close", () => {
+    if (!socket.destroyed) {
+      socket.end()
+    }
+  })
+
+  socket.once("close", () => {
+    if (!upstream.destroyed) {
+      upstream.end()
+    }
+  })
+}
+
+function createSideCarUpstreamSocket(targetUrl: URL): { socket: Socket | TLSSocket; readyEvent: "connect" | "secureConnect" } {
+  const port = Number(targetUrl.port || (targetUrl.protocol === "https:" ? 443 : 80))
+  if (targetUrl.protocol === "https:") {
+    return {
+      socket: connectTls({
+        host: targetUrl.hostname,
+        port,
+        servername: targetUrl.hostname,
+      }),
+      readyEvent: "secureConnect",
+    }
+  }
+  return {
+    socket: connectTcp(port, targetUrl.hostname),
+    readyEvent: "connect",
+  }
+}
+
+function buildSideCarWebSocketRequest(request: import("http").IncomingMessage, targetUrl: URL): string {
+  const pathWithQuery = `${targetUrl.pathname}${targetUrl.search}`
+  const requestLine = `${request.method ?? "GET"} ${pathWithQuery} HTTP/${request.httpVersion}\r\n`
+  const headerLines: string[] = []
+  const rawHeaders = request.rawHeaders ?? []
+  const blockedHeaders = getBlockedSideCarRequestHeaders()
+
+  for (let index = 0; index < rawHeaders.length; index += 2) {
+    const key = rawHeaders[index]
+    const value = rawHeaders[index + 1]
+    if (!key || value === undefined) continue
+    const lower = key.toLowerCase()
+    if (blockedHeaders.has(lower)) continue
+    if (lower === "origin") {
+      headerLines.push(`Origin: ${targetUrl.origin}\r\n`)
+      continue
+    }
+    headerLines.push(`${key}: ${value}\r\n`)
+  }
+
+  const hostValue = targetUrl.port ? `${targetUrl.hostname}:${targetUrl.port}` : targetUrl.hostname
+  headerLines.push(`Host: ${hostValue}\r\n`)
+  headerLines.push("\r\n")
+
+  return requestLine + headerLines.join("")
+}
+
+function isWebSocketUpgradeRequest(request: import("http").IncomingMessage): boolean {
+  const upgrade = request.headers.upgrade
+  if (typeof upgrade !== "string" || upgrade.toLowerCase() !== "websocket") {
+    return false
+  }
+  const connection = request.headers.connection
+  const connectionValue = Array.isArray(connection) ? connection.join(",") : connection ?? ""
+  return connectionValue.toLowerCase().split(",").map((part) => part.trim()).includes("upgrade")
+}
+
+function rejectUpgrade(socket: Socket, statusCode: number, statusText: string) {
+  if (socket.destroyed) {
+    return
+  }
+  socket.write(`HTTP/1.1 ${statusCode} ${statusText}\r\nConnection: close\r\nContent-Length: 0\r\n\r\n`)
+  socket.destroy()
+}
+
+function rewriteSideCarResponseHeaders(
+  headers: Record<string, string | string[] | undefined>,
+  sidecarId: string,
+  targetOrigin: string,
+  prefixMode: "strip" | "preserve",
+) {
+  if (prefixMode === "preserve") {
+    return headers
+  }
+
+  const next = { ...headers }
+  const locationHeader = next.location
+  const location = Array.isArray(locationHeader) ? locationHeader[0] : locationHeader
+  if (!location) {
+    return next
+  }
+
+  const publicBase = `/sidecars/${encodeURIComponent(sidecarId)}`
+
+  if (location.startsWith("/")) {
+    next.location = `${publicBase}${location}`
+    return next
+  }
+
+  try {
+    const parsed = new URL(location)
+    if (parsed.origin === targetOrigin) {
+      next.location = `${publicBase}${parsed.pathname}${parsed.search}${parsed.hash}`
+    }
+  } catch {
+    // Relative redirects should continue to resolve against the public sidecar path.
+  }
+
+  return next
+}
+
+function sanitizeSideCarProxyRequestHeaders(
+  headers: Record<string, string | string[] | undefined>,
+  targetOrigin: string,
+): Record<string, string | string[] | undefined> {
+  const blockedHeaders = getBlockedSideCarRequestHeaders()
+  const next: Record<string, string | string[] | undefined> = {}
+
+  for (const [key, value] of Object.entries(headers)) {
+    if (!value) continue
+    if (blockedHeaders.has(key.toLowerCase())) continue
+    next[key] = value
+  }
+
+  next.origin = targetOrigin
+  return next
+}
+
+function getBlockedSideCarRequestHeaders(): Set<string> {
+  return new Set([
+    "host",
+    "authorization",
+    "proxy-authorization",
+    "forwarded",
+    "x-forwarded-for",
+    "x-forwarded-host",
+    "x-forwarded-port",
+    "x-forwarded-proto",
+  ])
+}
--- a/packages/server/src/server/routes/sidecars.ts
+++ b/packages/server/src/server/routes/sidecars.ts
@@ -0,0 +1,56 @@
+import { FastifyInstance } from "fastify"
+import { z } from "zod"
+import type { SideCarManager } from "../../sidecars/manager"
+
+interface RouteDeps {
+  sidecarManager: SideCarManager
+}
+
+const SideCarCreateSchema = z.object({
+  kind: z.literal("port").default("port"),
+  name: z.string().trim().min(1),
+  port: z.number().int().min(1).max(65535),
+  insecure: z.boolean().default(false),
+  prefixMode: z.enum(["strip", "preserve"]).default("strip"),
+})
+
+const SideCarUpdateSchema = SideCarCreateSchema.omit({ kind: true }).partial().refine((value) => Object.keys(value).length > 0, {
+  message: "At least one field is required",
+})
+
+export function registerSideCarRoutes(app: FastifyInstance, deps: RouteDeps) {
+  app.get("/api/sidecars", async () => {
+    return { sidecars: await deps.sidecarManager.list() }
+  })
+
+  app.post("/api/sidecars", async (request, reply) => {
+    try {
+      const body = SideCarCreateSchema.parse(request.body ?? {})
+      const sidecar = await deps.sidecarManager.create(body)
+      reply.code(201)
+      return sidecar
+    } catch (error) {
+      reply.code(400)
+      return { error: error instanceof Error ? error.message : "Failed to create SideCar" }
+    }
+  })
+
+  app.put<{ Params: { id: string } }>("/api/sidecars/:id", async (request, reply) => {
+    try {
+      const body = SideCarUpdateSchema.parse(request.body ?? {})
+      return await deps.sidecarManager.update(request.params.id, body)
+    } catch (error) {
+      reply.code(400)
+      return { error: error instanceof Error ? error.message : "Failed to update SideCar" }
+    }
+  })
+
+  app.delete<{ Params: { id: string } }>("/api/sidecars/:id", async (request, reply) => {
+    const removed = await deps.sidecarManager.delete(request.params.id)
+    if (!removed) {
+      reply.code(404)
+      return { error: "SideCar not found" }
+    }
+    reply.code(204)
+  })
+}
--- a/packages/server/src/sidecars/manager.ts
+++ b/packages/server/src/sidecars/manager.ts
@@ -0,0 +1,256 @@
+import { connect } from "net"
+import type { EventBus } from "../events/bus"
+import type { Logger } from "../logger"
+import type { SettingsService } from "../settings/service"
+import type { SideCar, SideCarKind, SideCarPrefixMode, SideCarStatus } from "../api-types"
+
+interface SideCarManagerOptions {
+  settings: SettingsService
+  eventBus: EventBus
+  logger: Logger
+}
+
+interface SideCarConfigRecord {
+  id: string
+  kind: SideCarKind
+  name: string
+  port: number
+  insecure: boolean
+  prefixMode: SideCarPrefixMode
+  createdAt: string
+  updatedAt: string
+}
+
+interface SideCarRuntimeRecord {
+  status: SideCarStatus
+}
+
+export class SideCarManager {
+  private readonly configs = new Map<string, SideCarConfigRecord>()
+  private readonly runtime = new Map<string, SideCarRuntimeRecord>()
+
+  constructor(private readonly options: SideCarManagerOptions) {
+    for (const record of this.loadConfiguredSideCars()) {
+      this.configs.set(record.id, record)
+      this.runtime.set(record.id, { status: "stopped" })
+    }
+
+    queueMicrotask(() => {
+      for (const record of this.configs.values()) {
+        void this.refreshPortSideCar(record.id).catch((error) => {
+          this.options.logger.warn({ sidecarId: record.id, err: error }, "Failed to probe sidecar port")
+        })
+      }
+    })
+  }
+
+  async list(): Promise<SideCar[]> {
+    await this.refreshPortStatuses()
+    return Array.from(this.configs.values()).map((record) => this.toSideCar(record))
+  }
+
+  async get(id: string): Promise<SideCar | undefined> {
+    if (!this.configs.has(id)) return undefined
+    await this.refreshPortSideCar(id)
+    return this.toSideCar(this.requireConfig(id))
+  }
+
+  async create(input: {
+    kind: SideCarKind
+    name: string
+    port: number
+    insecure: boolean
+    prefixMode: SideCarPrefixMode
+  }): Promise<SideCar> {
+    const normalizedName = input.name.trim()
+    const id = this.buildSideCarId(normalizedName)
+    if (this.configs.has(id)) {
+      throw new Error(`SideCar '${id}' already exists`)
+    }
+
+    const now = new Date().toISOString()
+    const record: SideCarConfigRecord = {
+      id,
+      kind: input.kind,
+      name: normalizedName,
+      port: input.port,
+      insecure: input.insecure,
+      prefixMode: input.prefixMode,
+      createdAt: now,
+      updatedAt: now,
+    }
+
+    this.configs.set(record.id, record)
+    this.runtime.set(record.id, { status: "stopped" })
+    this.persistConfigs()
+    await this.refreshPortSideCar(record.id)
+    return this.toSideCar(record)
+  }
+
+  async update(
+    id: string,
+    input: Partial<{
+      name: string
+      port: number
+      insecure: boolean
+      prefixMode: SideCarPrefixMode
+    }>,
+  ): Promise<SideCar> {
+    const record = this.requireConfig(id)
+
+    record.name = typeof input.name === "string" ? input.name.trim() : record.name
+    record.port = typeof input.port === "number" ? input.port : record.port
+    record.insecure = typeof input.insecure === "boolean" ? input.insecure : record.insecure
+    record.prefixMode = typeof input.prefixMode === "string" ? input.prefixMode : record.prefixMode
+    record.updatedAt = new Date().toISOString()
+
+    this.persistConfigs()
+    await this.refreshPortSideCar(id)
+    return this.toSideCar(record)
+  }
+
+  async delete(id: string): Promise<boolean> {
+    const record = this.configs.get(id)
+    if (!record) return false
+
+    this.configs.delete(id)
+    this.runtime.delete(id)
+    this.persistConfigs()
+    this.options.eventBus.publish({ type: "sidecar.removed", sidecarId: id })
+    return true
+  }
+
+  async shutdown() {
+    return
+  }
+
+  buildTargetOrigin(sidecar: Pick<SideCar, "port" | "insecure">): string {
+    const protocol = sidecar.insecure ? "http" : "https"
+    return `${protocol}://127.0.0.1:${sidecar.port}`
+  }
+
+  buildProxyBasePath(id: string): string {
+    return `/sidecars/${encodeURIComponent(id)}`
+  }
+
+  buildTargetPath(id: string, incomingPath: string, search = ""): string {
+    const record = this.requireConfig(id)
+    const publicBase = this.buildProxyBasePath(id)
+    const normalizedPath = incomingPath || publicBase
+
+    if (record.prefixMode === "preserve") {
+      return `${normalizedPath}${search}`
+    }
+
+    let stripped = normalizedPath.startsWith(publicBase) ? normalizedPath.slice(publicBase.length) : normalizedPath
+    if (!stripped || stripped === "/") {
+      stripped = "/"
+    } else if (!stripped.startsWith("/")) {
+      stripped = `/${stripped}`
+    }
+    return `${stripped}${search}`
+  }
+
+  private async refreshPortStatuses() {
+    await Promise.all(Array.from(this.configs.values()).map((record) => this.refreshPortSideCar(record.id)))
+  }
+
+  private async refreshPortSideCar(id: string) {
+    const record = this.configs.get(id)
+    if (!record) return
+    const isAvailable = await this.isPortAvailable(record.port)
+    const current = this.runtime.get(id)
+    const nextStatus: SideCarStatus = isAvailable ? "running" : "stopped"
+    if (current?.status === nextStatus) {
+      return
+    }
+
+    this.runtime.set(id, { status: nextStatus })
+    record.updatedAt = new Date().toISOString()
+    this.publish(id)
+  }
+
+  private publish(id: string) {
+    const record = this.configs.get(id)
+    if (!record) return
+    this.options.eventBus.publish({ type: "sidecar.updated", sidecar: this.toSideCar(record) })
+  }
+
+  private toSideCar(record: SideCarConfigRecord): SideCar {
+    const runtime = this.runtime.get(record.id)
+    return {
+      id: record.id,
+      kind: record.kind,
+      name: record.name,
+      port: record.port,
+      insecure: record.insecure,
+      prefixMode: record.prefixMode,
+      status: runtime?.status ?? "stopped",
+      createdAt: record.createdAt,
+      updatedAt: record.updatedAt,
+    }
+  }
+
+  private requireConfig(id: string): SideCarConfigRecord {
+    const record = this.configs.get(id)
+    if (!record) {
+      throw new Error("SideCar not found")
+    }
+    return record
+  }
+
+  private persistConfigs() {
+    const sidecars = Array.from(this.configs.values()).map((record) => ({ ...record }))
+    this.options.settings.mergePatchOwner("config", "server", { sidecars })
+  }
+
+  private loadConfiguredSideCars(): SideCarConfigRecord[] {
+    const serverConfig = this.options.settings.getOwner("config", "server") as { sidecars?: unknown }
+    const list = Array.isArray(serverConfig?.sidecars) ? serverConfig.sidecars : []
+    const records: SideCarConfigRecord[] = []
+    for (const item of list) {
+      if (!item || typeof item !== "object") continue
+      const record = item as Record<string, unknown>
+      const kind = record.kind === "port" ? "port" : null
+      const id = typeof record.id === "string" && record.id.trim() ? record.id.trim() : null
+      const name = typeof record.name === "string" && record.name.trim() ? record.name.trim() : null
+      const port = typeof record.port === "number" && Number.isInteger(record.port) ? record.port : null
+      if (!kind || !id || !name || !port) continue
+
+      const insecure = record.insecure === true
+      const prefixMode = record.prefixMode === "preserve" ? "preserve" : "strip"
+      const createdAt = typeof record.createdAt === "string" && record.createdAt ? record.createdAt : new Date().toISOString()
+      const updatedAt = typeof record.updatedAt === "string" && record.updatedAt ? record.updatedAt : createdAt
+      records.push({ id, kind, name, port, insecure, prefixMode, createdAt, updatedAt })
+    }
+    return records
+  }
+
+  private isPortAvailable(port: number): Promise<boolean> {
+    return new Promise((resolve) => {
+      const socket = connect({ port, host: "127.0.0.1" }, () => {
+        socket.end()
+        resolve(true)
+      })
+      socket.once("error", () => {
+        socket.destroy()
+        resolve(false)
+      })
+    })
+  }
+
+  private buildSideCarId(name: string): string {
+    const normalized = name
+      .trim()
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/g, "-")
+      .replace(/-{2,}/g, "-")
+      .replace(/^-|-$/g, "")
+
+    if (!normalized) {
+      throw new Error("SideCar name must include letters or numbers")
+    }
+
+    return normalized
+  }
+}
--- a/packages/ui/src/App.tsx
+++ b/packages/ui/src/App.tsx
@@ -10,7 +10,10 @@ import InstanceTabs from "./components/instance-tabs"
 import InstanceDisconnectedModal from "./components/instance-disconnected-modal"
 import InstanceShell from "./components/instance/instance-shell2"
 import { SettingsScreen } from "./components/settings-screen"
+import { SideCarPickerDialog } from "./components/sidecar-picker-dialog"
+import { SideCarView } from "./components/sidecar-view"
 import { InstanceMetadataProvider } from "./lib/contexts/instance-metadata-context"
+import { showAlertDialog } from "./stores/alerts"
 import { initGithubStars } from "./stores/github-stars"

 import { useCommands } from "./lib/hooks/use-commands"
@@ -23,7 +26,6 @@ import { runtimeEnv } from "./lib/runtime-env"
 import { useI18n } from "./lib/i18n"
 import { setWakeLockDesired } from "./lib/native/wake-lock"
 import {
-  hasInstances,
  isSelectingFolder,
  setIsSelectingFolder,
  showFolderSelection,
@@ -33,10 +35,7 @@ import { useConfig } from "./stores/preferences"
 import {
  createInstance,
  instances,
-  activeInstanceId,
-  setActiveInstanceId,
  stopInstance,
-  getActiveInstance,
  disconnectedInstance,
  acknowledgeDisconnectedInstance,
 } from "./stores/instances"
@@ -53,6 +52,22 @@ import {

 import { getInstanceSessionIndicatorStatus } from "./stores/session-status"
 import { openSettings } from "./stores/settings-screen"
+import {
+  closeSidecarTab,
+  ensureSidecarsLoaded,
+  openSidecarTab,
+} from "./stores/sidecars"
+import {
+  activeAppTab,
+  activeAppTabId,
+  appTabs,
+  ensureActiveAppTab,
+  getAdjacentAppTabId,
+  getAppTabById,
+  selectAppTab,
+  selectInstanceTab,
+  selectSidecarTab,
+} from "./stores/app-tabs"

 const log = getLogger("actions")

@@ -77,6 +92,7 @@ const App: Component = () => {
  } = useConfig()
  const [escapeInDebounce, setEscapeInDebounce] = createSignal(false)
  const [instanceTabBarHeight, setInstanceTabBarHeight] = createSignal(0)
+  const [sidecarPickerOpen, setSidecarPickerOpen] = createSignal(false)

  const phoneQuery = useMediaQuery("(max-width: 767px)")
  const isPhoneLayout = createMemo(() => phoneQuery())
@@ -206,8 +222,7 @@ const App: Component = () => {
  })

  createEffect(() => {
-    instances()
-    hasInstances()
+    appTabs()
    requestAnimationFrame(() => updateInstanceTabBarHeight())
  })

@@ -219,7 +234,15 @@ const App: Component = () => {
    onCleanup(() => window.removeEventListener("resize", handleResize))
  })

-  const activeInstance = createMemo(() => getActiveInstance())
+  createEffect(() => {
+    appTabs()
+    ensureActiveAppTab()
+  })
+
+  const activeInstance = createMemo(() => {
+    const tab = activeAppTab()
+    return tab?.kind === "instance" ? tab.instance : null
+  })
  const activeSessionIdForInstance = createMemo(() => {
    const instance = activeInstance()
    if (!instance) return null
@@ -244,6 +267,7 @@ const App: Component = () => {
      recordWorkspaceLaunch(folderPath, selectedBinary)
      clearLaunchError()
      const instanceId = await createInstance(folderPath, selectedBinary)
+      selectInstanceTab(instanceId)
      setShowFolderSelection(false)

      log.info("Created instance", {
@@ -270,8 +294,27 @@ const App: Component = () => {
  }

  function handleNewInstanceRequest() {
-    if (hasInstances()) {
-      setShowFolderSelection(true)
+    setShowFolderSelection(true)
+  }
+
+  function handleOpenSidecarPicker() {
+    setSidecarPickerOpen(true)
+    void ensureSidecarsLoaded()
+  }
+
+  async function handleOpenSidecar(sidecarId: string) {
+    try {
+      const tab = await openSidecarTab(sidecarId)
+      selectSidecarTab(tab.token)
+      setShowFolderSelection(false)
+      setSidecarPickerOpen(false)
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error)
+      showAlertDialog(message, {
+        variant: "error",
+        title: t("sidecars.open.errorTitle"),
+      })
+      log.error("Failed to open SideCar", error)
    }
  }

@@ -332,6 +375,23 @@ const App: Component = () => {
    }
  }

+  async function handleCloseAppTab(tabId: string) {
+    const tab = getAppTabById(tabId)
+    if (!tab) return
+
+    const fallbackTabId = activeAppTabId() === tabId ? getAdjacentAppTabId(tabId) : activeAppTabId()
+
+    if (tab.kind === "instance") {
+      await handleCloseInstance(tab.instance.id)
+    } else {
+      closeSidecarTab(tab.sidecarTab.token)
+    }
+
+    if (!getAppTabById(tabId)) {
+      ensureActiveAppTab(fallbackTabId)
+    }
+  }
+
  const handleSidebarAgentChange = async (instanceId: string, sessionId: string, agent: string) => {
    if (!instanceId || !sessionId || sessionId === "info") return
    await updateSessionAgent(instanceId, sessionId, agent)
@@ -361,6 +421,7 @@ const App: Component = () => {
    setThinkingBlocksExpansion,
    setToolInputsVisibility,
    handleNewInstanceRequest,
+    handleCloseActiveTab: () => handleCloseAppTab(activeAppTabId() ?? ""),
    handleCloseInstance,
    handleNewSession,
    handleCloseSession,
@@ -371,6 +432,7 @@ const App: Component = () => {
  useAppLifecycle({
    setEscapeInDebounce,
    handleNewInstanceRequest,
+    handleCloseActiveTab: () => handleCloseAppTab(activeAppTabId() ?? ""),
    handleCloseInstance,
    handleNewSession,
    handleCloseSession,
@@ -470,52 +532,60 @@ const App: Component = () => {
          </div>
        </Show>
        <Show
-          when={!hasInstances()}
+          when={appTabs().length === 0}
          fallback={
            <>
              <Show when={!isPhoneLayout() || !mobileFullscreenMode()}>
                <InstanceTabs
-                  instances={instances()}
-                  activeInstanceId={activeInstanceId()}
-                  onSelect={setActiveInstanceId}
-                  onClose={handleCloseInstance}
+                  tabs={appTabs()}
+                  activeTabId={activeAppTabId()}
+                  onSelect={selectAppTab}
+                  onClose={(tabId) => void handleCloseAppTab(tabId)}
                  onNew={handleNewInstanceRequest}
                />
              </Show>
- 
-              <For each={Array.from(instances().values())}>
-                {(instance) => {
-                  const isActiveInstance = () => activeInstanceId() === instance.id
-                  const isVisible = () => isActiveInstance() && !showFolderSelection()
-                    return (
-                       <div
-                         class="flex-1 min-h-0 overflow-hidden"
-                         style={{ display: isVisible() ? "flex" : "none" }}
-                         data-instance-id={instance.id}
-                         data-instance-active={isActiveInstance() ? "true" : "false"}
-                         data-instance-visible={isVisible() ? "true" : "false"}
-                       >
-                         <InstanceMetadataProvider instance={instance}>
-                           <InstanceShell
-                             instance={instance}
-                             isActiveInstance={isActiveInstance()}
-                             escapeInDebounce={escapeInDebounce()}
-                             paletteCommands={paletteCommands}
-                             onCloseSession={(sessionId) => handleCloseSession(instance.id, sessionId)}
-                             onNewSession={() => handleNewSession(instance.id)}
-                             handleSidebarAgentChange={(sessionId, agent) => handleSidebarAgentChange(instance.id, sessionId, agent)}
-                             handleSidebarModelChange={(sessionId, model) => handleSidebarModelChange(instance.id, sessionId, model)}
-                             onExecuteCommand={executeCommand}
-                            tabBarOffset={isPhoneLayout() && mobileFullscreenMode() ? 0 : instanceTabBarHeight()}
-                            mobileFullscreenMode={isPhoneLayout() && mobileFullscreenMode()}
-                            onEnterMobileFullscreen={() => void enterMobileFullscreen()}
-                            onExitMobileFullscreen={() => void exitMobileFullscreen()}
-                          />
-                        </InstanceMetadataProvider>
-
-                      </div>
-                    )

+              <For each={appTabs()}>
+                {(tab) => {
+                  const isVisible = () => activeAppTabId() === tab.id && !showFolderSelection()
+                  return tab.kind === "instance" ? (
+                    <div
+                      class="flex-1 min-h-0 overflow-hidden"
+                      style={{ display: isVisible() ? "flex" : "none" }}
+                      data-instance-id={tab.instance.id}
+                      data-tab-id={tab.id}
+                      data-tab-kind={tab.kind}
+                      data-tab-visible={isVisible() ? "true" : "false"}
+                    >
+                      <InstanceMetadataProvider instance={tab.instance}>
+                        <InstanceShell
+                          instance={tab.instance}
+                          isActiveInstance={isVisible()}
+                          escapeInDebounce={escapeInDebounce()}
+                          paletteCommands={paletteCommands}
+                          onCloseSession={(sessionId) => handleCloseSession(tab.instance.id, sessionId)}
+                          onNewSession={() => handleNewSession(tab.instance.id)}
+                          handleSidebarAgentChange={(sessionId, agent) => handleSidebarAgentChange(tab.instance.id, sessionId, agent)}
+                          handleSidebarModelChange={(sessionId, model) => handleSidebarModelChange(tab.instance.id, sessionId, model)}
+                          onExecuteCommand={executeCommand}
+                          tabBarOffset={isPhoneLayout() && mobileFullscreenMode() ? 0 : instanceTabBarHeight()}
+                          mobileFullscreenMode={isPhoneLayout() && mobileFullscreenMode()}
+                          onEnterMobileFullscreen={() => void enterMobileFullscreen()}
+                          onExitMobileFullscreen={() => void exitMobileFullscreen()}
+                        />
+                      </InstanceMetadataProvider>
+                    </div>
+                  ) : (
+                    <div
+                      class="flex-1 min-h-0 overflow-hidden"
+                      style={{ display: isVisible() ? "flex" : "none" }}
+                      data-tab-id={tab.id}
+                      data-tab-kind={tab.kind}
+                      data-tab-visible={isVisible() ? "true" : "false"}
+                    >
+                      <SideCarView tab={tab.sidecarTab} />
+                    </div>
+                  )
                }}
              </For>

@@ -525,6 +595,7 @@ const App: Component = () => {
          <FolderSelectionView
            onSelectFolder={handleSelectFolder}
            isLoading={isSelectingFolder()}
+            onOpenSidecar={handleOpenSidecarPicker}
          />
        </Show>

@@ -534,6 +605,7 @@ const App: Component = () => {
              <FolderSelectionView
                onSelectFolder={handleSelectFolder}
                isLoading={isSelectingFolder()}
+                onOpenSidecar={handleOpenSidecarPicker}
                onClose={() => {
                  setShowFolderSelection(false)
                  clearLaunchError()
@@ -544,6 +616,7 @@ const App: Component = () => {
        </Show>
 
        <SettingsScreen />
+        <SideCarPickerDialog open={sidecarPickerOpen()} onClose={() => setSidecarPickerOpen(false)} onOpenSidecar={handleOpenSidecar} />
 
        <AlertDialog />

--- a/packages/ui/src/components/folder-selection-view.tsx
+++ b/packages/ui/src/components/folder-selection-view.tsx
@@ -27,6 +27,7 @@ type HomeTab = "local" | "servers"

 interface FolderSelectionViewProps {
  onSelectFolder: (folder: string, binaryPath?: string) => void
+  onOpenSidecar?: () => void
  isLoading?: boolean
  onClose?: () => void
 }
@@ -845,32 +846,43 @@ const FolderSelectionView: Component<FolderSelectionViewProps> = (props) => {
                </div>

                <div class="panel-body flex flex-col gap-3">
-                    <button
-                      onClick={() => void handleBrowse()}
-                      disabled={props.isLoading}
-                      class="button-primary w-full flex items-center justify-center text-sm disabled:cursor-not-allowed"
-                      onMouseEnter={() => setFocusMode("new")}
-                    >
-                      <div class="flex items-center gap-2">
-                        <FolderPlus class="w-4 h-4" />
-                        <span>
-                          {props.isLoading
-                            ? t("folderSelection.browse.buttonOpening")
-                            : t("folderSelection.browse.button")}
-                        </span>
-                      </div>
-                      <Kbd shortcut="cmd+n" class="ml-2 kbd-hint" />
-                    </button>
+                  <button
+                    onClick={() => void handleBrowse()}
+                    disabled={props.isLoading}
+                    class="button-primary w-full flex items-center justify-center text-sm disabled:cursor-not-allowed"
+                    onMouseEnter={() => setFocusMode("new")}
+                  >
+                    <div class="flex items-center gap-2">
+                      <FolderPlus class="w-4 h-4" />
+                      <span>
+                        {props.isLoading
+                          ? t("folderSelection.browse.buttonOpening")
+                          : t("folderSelection.browse.button")}
+                      </span>
+                    </div>
+                    <Kbd shortcut="cmd+n" class="ml-2 kbd-hint" />
+                  </button>

-                    <button
-                      onClick={openServerDialog}
-                      class="button-primary w-full flex items-center justify-center text-sm"
-                    >
-                      <div class="flex items-center gap-2">
-                        <Globe class="w-4 h-4" />
-                        <span>{t("folderSelection.actions.connectButton")}</span>
-                      </div>
-                    </button>
+                  <button
+                    type="button"
+                    onClick={() => props.onOpenSidecar?.()}
+                    class="button-primary mt-3 w-full flex items-center justify-center text-sm"
+                  >
+                    <div class="flex items-center gap-2">
+                      <MonitorUp class="w-4 h-4" />
+                      <span>{t("folderSelection.sidecars.button")}</span>
+                    </div>
+                  </button>
+
+                  <button
+                    onClick={openServerDialog}
+                    class="button-primary w-full flex items-center justify-center text-sm"
+                  >
+                    <div class="flex items-center gap-2">
+                      <Globe class="w-4 h-4" />
+                      <span>{t("folderSelection.actions.connectButton")}</span>
+                    </div>
+                  </button>
                </div>

                {/* OpenCode settings section */}
--- a/packages/ui/src/components/instance-tabs.tsx
+++ b/packages/ui/src/components/instance-tabs.tsx
@@ -1,6 +1,5 @@
 import { Component, For, Show, createMemo } from "solid-js"
 import { Dynamic } from "solid-js/web"
-import type { Instance } from "../types/instance"
 import InstanceTab from "./instance-tab"
 import KeyboardHint from "./keyboard-hint"
 import { Plus, MonitorUp, Bell, BellOff, Settings } from "lucide-solid"
@@ -9,12 +8,13 @@ import { useI18n } from "../lib/i18n"
 import { isOsNotificationSupportedSync } from "../lib/os-notifications"
 import { useConfig } from "../stores/preferences"
 import { openSettings } from "../stores/settings-screen"
+import type { AppTabRecord } from "../stores/app-tabs"

 interface InstanceTabsProps {
-  instances: Map<string, Instance>
-  activeInstanceId: string | null
-  onSelect: (instanceId: string) => void
-  onClose: (instanceId: string) => void
+  tabs: AppTabRecord[]
+  activeTabId: string | null
+  onSelect: (tabId: string) => void
+  onClose: (tabId: string) => void
  onNew: () => void
 }

@@ -42,15 +42,25 @@ const InstanceTabs: Component<InstanceTabsProps> = (props) => {
        <div class="tab-scroll">
          <div class="tab-strip">
            <div class="tab-strip-tabs">
-              <For each={Array.from(props.instances.entries())}>
-                {([id, instance]) => (
-                  <InstanceTab
-                    instance={instance}
-                    active={id === props.activeInstanceId}
-                    onSelect={() => props.onSelect(id)}
-                    onClose={() => props.onClose(id)}
-                  />
-                )}
+              <For each={props.tabs}>
+                {(tab) =>
+                  tab.kind === "instance" ? (
+                    <InstanceTab
+                      instance={tab.instance}
+                      active={tab.id === props.activeTabId}
+                      onSelect={() => props.onSelect(tab.id)}
+                      onClose={() => props.onClose(tab.id)}
+                    />
+                  ) : (
+                    <div class={`tab-pill ${tab.id === props.activeTabId ? "tab-pill-active" : ""}`}>
+                      <button class="tab-pill-button" onClick={() => props.onSelect(tab.id)}>
+                        <span class="truncate max-w-[180px]">{tab.sidecarTab.name}</span>
+                      </button>
+                      <button class="tab-pill-close" onClick={() => props.onClose(tab.id)} aria-label={tab.sidecarTab.name}>
+                        ×
+                      </button>
+                    </div>
+                  )}
              </For>
              <button
                class="new-tab-button"
@@ -62,7 +72,7 @@ const InstanceTabs: Component<InstanceTabsProps> = (props) => {
              </button>
            </div>
            <div class="tab-strip-spacer" />
-            <Show when={Array.from(props.instances.entries()).length > 1}>
+            <Show when={props.tabs.length > 1}>
              <div class="tab-shortcuts">
                <KeyboardHint
                  shortcuts={[keyboardRegistry.get("instance-prev")!, keyboardRegistry.get("instance-next")!].filter(
--- a/packages/ui/src/components/message-block.tsx
+++ b/packages/ui/src/components/message-block.tsx
@@ -9,7 +9,7 @@ import type { MessageRecord } from "../stores/message-v2/types"
 import { messageStoreBus } from "../stores/message-v2/bus"
 import { formatTokenTotal } from "../lib/formatters"
 import { sessions, setActiveParentSession, setActiveSession } from "../stores/sessions"
-import { setActiveInstanceId } from "../stores/instances"
+import { selectInstanceTab } from "../stores/app-tabs"
 import { showAlertDialog } from "../stores/alerts"
 import { deleteMessage } from "../stores/session-actions"
 import { useI18n } from "../lib/i18n"
@@ -130,7 +130,7 @@ function findTaskSessionLocation(sessionId: string, preferredInstanceId?: string
 }

 function navigateToTaskSession(location: TaskSessionLocation) {
-  setActiveInstanceId(location.instanceId)
+  selectInstanceTab(location.instanceId)
  const parentToActivate = location.parentId ?? location.sessionId
  setActiveParentSession(location.instanceId, parentToActivate)
  if (location.parentId) {
--- a/packages/ui/src/components/settings-screen.tsx
+++ b/packages/ui/src/components/settings-screen.tsx
@@ -1,5 +1,5 @@
 import { Dialog } from "@kobalte/core/dialog"
-import { Settings, Bell, MonitorUp, Paintbrush, Terminal, Volume2, X } from "lucide-solid"
+import { Settings, Bell, MonitorUp, Paintbrush, Terminal, Volume2, Globe, X } from "lucide-solid"
 import { createMemo, For, type Component } from "solid-js"
 import { useI18n } from "../lib/i18n"
 import {
@@ -14,6 +14,7 @@ import { NotificationsSettingsSection } from "./settings/notifications-settings-
 import { OpenCodeSettingsSection } from "./settings/opencode-settings-section"
 import { RemoteAccessSettingsSection } from "./settings/remote-access-settings-section"
 import { SpeechSettingsSection } from "./settings/speech-settings-section"
+import { SideCarsSettingsSection } from "./settings/sidecars-settings-section"

 export const SettingsScreen: Component = () => {
  const { t } = useI18n()
@@ -23,6 +24,7 @@ export const SettingsScreen: Component = () => {
    { id: "notifications" as SettingsSectionId, icon: Bell, label: t("settings.nav.notifications") },
    { id: "remote" as SettingsSectionId, icon: MonitorUp, label: t("settings.nav.remote") },
    { id: "speech" as SettingsSectionId, icon: Volume2, label: t("settings.nav.speech") },
+    { id: "sidecars" as SettingsSectionId, icon: Globe, label: t("settings.nav.sidecars") },
    { id: "opencode" as SettingsSectionId, icon: Terminal, label: t("settings.nav.opencode") },
  ])

@@ -34,6 +36,8 @@ export const SettingsScreen: Component = () => {
        return <RemoteAccessSettingsSection />
      case "speech":
        return <SpeechSettingsSection />
+      case "sidecars":
+        return <SideCarsSettingsSection />
      case "opencode":
        return <OpenCodeSettingsSection />
      case "appearance":
--- a/packages/ui/src/components/settings/sidecars-settings-section.tsx
+++ b/packages/ui/src/components/settings/sidecars-settings-section.tsx
@@ -0,0 +1,201 @@
+import { createMemo, createSignal, For, Show, onMount, type Component } from "solid-js"
+import { Globe, Loader2, Plus, Trash2 } from "lucide-solid"
+import { useI18n } from "../../lib/i18n"
+import { serverApi } from "../../lib/api-client"
+import { ensureSidecarsLoaded, sidecars, sidecarsLoading } from "../../stores/sidecars"
+
+function deriveSidecarId(value: string): string {
+  return value
+    .trim()
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/-{2,}/g, "-")
+    .replace(/^-|-$/g, "")
+}
+
+export const SideCarsSettingsSection: Component = () => {
+  const { t } = useI18n()
+  const [name, setName] = createSignal("")
+  const [port, setPort] = createSignal("3000")
+  const [insecure, setInsecure] = createSignal(false)
+  const [prefixMode, setPrefixMode] = createSignal<"strip" | "preserve">("strip")
+  const [busyId, setBusyId] = createSignal<string | null>(null)
+  const [creating, setCreating] = createSignal(false)
+  const [formError, setFormError] = createSignal<string | null>(null)
+  const [actionError, setActionError] = createSignal<string | null>(null)
+
+  onMount(() => {
+    void ensureSidecarsLoaded()
+  })
+
+  const orderedSidecars = createMemo(() => Array.from(sidecars().values()).sort((a, b) => a.name.localeCompare(b.name)))
+  const derivedId = createMemo(() => deriveSidecarId(name()) || "your-sidecar")
+
+  async function handleCreate() {
+    const trimmedName = name().trim()
+    const nextPort = Number(port())
+    if (!trimmedName || !Number.isInteger(nextPort) || nextPort <= 0 || nextPort > 65535) {
+      setFormError(t("sidecars.form.validation"))
+      return
+    }
+
+    setCreating(true)
+    setFormError(null)
+    try {
+      await serverApi.createSidecar({
+        kind: "port",
+        name: trimmedName,
+        port: nextPort,
+        insecure: insecure(),
+        prefixMode: prefixMode(),
+      })
+      setName("")
+      setPort("3000")
+      setInsecure(false)
+      setPrefixMode("strip")
+    } catch (error) {
+      setFormError(error instanceof Error ? error.message : String(error))
+    } finally {
+      setCreating(false)
+    }
+  }
+
+  async function handleDelete(id: string) {
+    setBusyId(id)
+    setActionError(null)
+    try {
+      await serverApi.deleteSidecar(id)
+    } catch (error) {
+      setActionError(error instanceof Error ? error.message : String(error))
+    } finally {
+      setBusyId(null)
+    }
+  }
+
+  return (
+    <div class="settings-section-stack">
+      <div class="settings-card">
+        <div class="settings-card-header">
+          <div class="settings-card-heading-with-icon">
+            <Globe class="settings-card-heading-icon" />
+            <div>
+              <h3 class="settings-card-title">{t("settings.section.sidecars.title")}</h3>
+              <p class="settings-card-subtitle">{t("settings.section.sidecars.subtitle")}</p>
+            </div>
+          </div>
+          <span class="settings-scope-badge settings-scope-badge-server">{t("settings.scope.server")}</span>
+        </div>
+
+        <div class="settings-card-content">
+          <div class="settings-toggle-row settings-toggle-row-compact">
+            <div>
+              <div class="settings-toggle-title">{t("sidecars.form.name")}</div>
+              <div class="settings-toggle-caption">{t("sidecars.basePath")}: <code>/sidecars/{derivedId()}</code></div>
+            </div>
+            <input
+              class="selector-input w-full max-w-xs"
+              value={name()}
+              onInput={(event) => {
+                setFormError(null)
+                setName(event.currentTarget.value)
+              }}
+            />
+          </div>
+
+          <div class="settings-toggle-row settings-toggle-row-compact">
+            <div>
+              <div class="settings-toggle-title">{t("sidecars.form.port")}</div>
+              <div class="settings-toggle-caption">127.0.0.1</div>
+            </div>
+            <input
+              class="selector-input w-full max-w-xs"
+              value={port()}
+              onInput={(event) => {
+                setFormError(null)
+                setPort(event.currentTarget.value)
+              }}
+              inputMode="numeric"
+            />
+          </div>
+
+          <div class="settings-toggle-row settings-toggle-row-compact">
+            <div>
+              <div class="settings-toggle-title">{t("sidecars.form.protocol")}</div>
+              <div class="settings-toggle-caption">{t("sidecars.form.protocol.help")}</div>
+            </div>
+            <select class="selector-input w-full max-w-xs" value={insecure() ? "http" : "https"} onChange={(event) => setInsecure(event.currentTarget.value === "http") }>
+              <option value="https">{t("sidecars.form.protocol.https")}</option>
+              <option value="http">{t("sidecars.form.protocol.http")}</option>
+            </select>
+          </div>
+
+          <div class="settings-toggle-row settings-toggle-row-compact">
+            <div>
+              <div class="settings-toggle-title">{t("sidecars.form.prefixMode")}</div>
+              <div class="settings-toggle-caption">{t("sidecars.form.prefixMode.help")}</div>
+            </div>
+            <select class="selector-input w-full max-w-xs" value={prefixMode()} onChange={(event) => setPrefixMode(event.currentTarget.value as "strip" | "preserve") }>
+              <option value="strip">{t("sidecars.form.prefixMode.strip")}</option>
+              <option value="preserve">{t("sidecars.form.prefixMode.preserve")}</option>
+            </select>
+          </div>
+
+          <Show when={formError()}>
+            <div class="text-sm text-red-500">{formError()}</div>
+          </Show>
+
+          <div class="flex justify-end">
+            <button type="button" class="selector-button selector-button-primary" disabled={creating()} onClick={() => void handleCreate()}>
+              <Show when={creating()} fallback={<Plus class="w-4 h-4" />}>
+                <Loader2 class="w-4 h-4 animate-spin" />
+              </Show>
+              <span>{t("sidecars.form.add")}</span>
+            </button>
+          </div>
+        </div>
+      </div>
+
+      <div class="settings-card">
+        <div class="settings-card-header">
+          <div>
+            <h3 class="settings-card-title">{t("sidecars.settings.listTitle")}</h3>
+            <p class="settings-card-subtitle">{t("sidecars.settings.listSubtitle")}</p>
+          </div>
+        </div>
+
+        <div class="settings-card-content">
+          <Show when={actionError()}>
+            <div class="text-sm text-red-500">{actionError()}</div>
+          </Show>
+
+          <Show when={!sidecarsLoading()} fallback={<div class="settings-card-message">{t("sidecars.picker.loading")}</div>}>
+            <Show when={orderedSidecars().length > 0} fallback={<div class="settings-card-message">{t("sidecars.settings.empty")}</div>}>
+              <For each={orderedSidecars()}>
+                {(sidecar) => (
+                  <div class="settings-toggle-row settings-toggle-row-compact">
+                    <div>
+                      <div class="settings-toggle-title">{sidecar.name}</div>
+                      <div class="settings-toggle-caption">
+                        {t("sidecars.kind.port")} · {sidecar.insecure ? "http" : "https"}://127.0.0.1:{sidecar.port}
+                      </div>
+                      <div class="settings-toggle-caption">
+                        {t("sidecars.basePath")}: <code>/sidecars/{sidecar.id}</code> · {t(`sidecars.form.prefixMode.${sidecar.prefixMode}`)}
+                      </div>
+                    </div>
+
+                    <div class="flex items-center gap-2">
+                      <span class="text-xs text-secondary min-w-[4.5rem] text-right">{t(`sidecars.status.${sidecar.status}`)}</span>
+                      <button type="button" class="selector-button selector-button-secondary" disabled={busyId() === sidecar.id} onClick={() => void handleDelete(sidecar.id)}>
+                        <Trash2 class="w-4 h-4" />
+                      </button>
+                    </div>
+                  </div>
+                )}
+              </For>
+            </Show>
+          </Show>
+        </div>
+      </div>
+    </div>
+  )
+}
--- a/packages/ui/src/components/sidecar-picker-dialog.tsx
+++ b/packages/ui/src/components/sidecar-picker-dialog.tsx
@@ -0,0 +1,82 @@
+import { Dialog } from "@kobalte/core/dialog"
+import { For, Show, createEffect, createMemo, type Component } from "solid-js"
+import { Globe, Square } from "lucide-solid"
+import { useI18n } from "../lib/i18n"
+import { ensureSidecarsLoaded, sidecars, sidecarsLoading } from "../stores/sidecars"
+
+interface SideCarPickerDialogProps {
+  open: boolean
+  onClose: () => void
+  onOpenSidecar: (sidecarId: string) => void | Promise<void>
+}
+
+export const SideCarPickerDialog: Component<SideCarPickerDialogProps> = (props) => {
+  const { t } = useI18n()
+  const orderedSidecars = createMemo(() => Array.from(sidecars().values()).sort((a, b) => a.name.localeCompare(b.name)))
+
+  createEffect(() => {
+    if (props.open) {
+      void ensureSidecarsLoaded()
+    }
+  })
+
+  return (
+    <Dialog open={props.open} onOpenChange={(open) => !open && props.onClose()}>
+      <Dialog.Portal>
+        <Dialog.Overlay class="modal-overlay" />
+        <div class="fixed inset-0 z-50 flex items-center justify-center p-4">
+          <Dialog.Content class="modal-surface w-full max-w-2xl p-6 flex flex-col gap-4 max-h-[80vh] overflow-hidden">
+            <div>
+              <Dialog.Title class="text-xl font-semibold text-primary">{t("sidecars.picker.title")}</Dialog.Title>
+              <Dialog.Description class="text-sm text-secondary mt-2">
+                {t("sidecars.picker.subtitle")}
+              </Dialog.Description>
+            </div>
+
+            <div class="flex-1 overflow-auto flex flex-col gap-3">
+              <Show when={!sidecarsLoading()} fallback={<div class="panel panel-empty-state">{t("sidecars.picker.loading")}</div>}>
+                <Show when={orderedSidecars().length > 0} fallback={<div class="panel panel-empty-state">{t("sidecars.picker.empty")}</div>}>
+                  <For each={orderedSidecars()}>
+                    {(sidecar) => (
+                      <button
+                        type="button"
+                        class="panel-list-item panel-list-item-content text-left disabled:cursor-not-allowed disabled:opacity-60"
+                        disabled={sidecar.status !== "running"}
+                        onClick={() => void props.onOpenSidecar(sidecar.id)}
+                      >
+                        <div class="flex items-center justify-between gap-4 w-full">
+                          <div class="flex items-center gap-3 min-w-0">
+                            <span class="panel-empty-state-icon !w-10 !h-10">
+                              <Globe class="w-5 h-5" />
+                            </span>
+                            <div class="min-w-0">
+                              <div class="text-sm font-medium text-primary truncate">{sidecar.name}</div>
+                              <div class="text-xs text-muted">
+                                {t("sidecars.kind.port")} - {sidecar.insecure ? "http" : "https"}://127.0.0.1:{sidecar.port}
+                              </div>
+                              <div class="text-xs text-muted mt-1">{t("sidecars.basePath")}: <code>/sidecars/{sidecar.id}</code></div>
+                            </div>
+                          </div>
+                          <div class="text-xs text-secondary flex items-center gap-2">
+                            <Square class="w-4 h-4" />
+                            <span>{t(`sidecars.status.${sidecar.status}`)}</span>
+                          </div>
+                        </div>
+                      </button>
+                    )}
+                  </For>
+                </Show>
+              </Show>
+            </div>
+
+            <div class="flex justify-end">
+              <button type="button" class="selector-button selector-button-secondary" onClick={props.onClose}>
+                {t("sidecars.picker.close")}
+              </button>
+            </div>
+          </Dialog.Content>
+        </div>
+      </Dialog.Portal>
+    </Dialog>
+  )
+}
--- a/packages/ui/src/components/sidecar-view.tsx
+++ b/packages/ui/src/components/sidecar-view.tsx
@@ -0,0 +1,197 @@
+import { ArrowLeft, ArrowRight, RefreshCw } from "lucide-solid"
+import { createEffect, createMemo, createSignal, type Component } from "solid-js"
+import type { SideCarTabRecord } from "../stores/sidecars"
+import { useI18n } from "../lib/i18n"
+
+interface SideCarViewProps {
+  tab: SideCarTabRecord
+}
+
+export const SideCarView: Component<SideCarViewProps> = (props) => {
+  const { t } = useI18n()
+  const [frameSrc, setFrameSrc] = createSignal(props.tab.shellUrl)
+  const [pathInput, setPathInput] = createSignal("/")
+  let iframeRef: HTMLIFrameElement | undefined
+
+  const lockedBaseLabel = createMemo(() => {
+    const hostLabel = props.tab.port ? `${props.tab.name}:${props.tab.port}` : props.tab.name
+    if (props.tab.prefixMode === "preserve") {
+      return `${hostLabel}${props.tab.proxyBasePath}`
+    }
+    return hostLabel
+  })
+
+  const getEditablePathFromUrl = (url: string): string => {
+    try {
+      const parsed = new URL(url, window.location.origin)
+      const basePath = props.tab.proxyBasePath
+      let pathname = parsed.pathname
+
+      if (basePath && pathname.startsWith(basePath)) {
+        pathname = pathname.slice(basePath.length) || "/"
+      }
+
+      if (!pathname.startsWith("/")) {
+        pathname = `/${pathname}`
+      }
+
+      return `${pathname}${parsed.search}${parsed.hash}`
+    } catch {
+      return "/"
+    }
+  }
+
+  const buildNormalizedTargetUrl = (rawInput: string): string => {
+    const trimmed = rawInput.trim()
+    const withLeadingSlash = trimmed.startsWith("/") ? trimmed : `/${trimmed}`
+    const parsed = new URL(withLeadingSlash || "/", window.location.origin)
+
+    const safeSegments: string[] = []
+    for (const segment of parsed.pathname.split("/")) {
+      if (!segment || segment === ".") {
+        continue
+      }
+      if (segment === "..") {
+        if (safeSegments.length > 0) {
+          safeSegments.pop()
+        }
+        continue
+      }
+      safeSegments.push(segment)
+    }
+
+    const normalizedPath = `/${safeSegments.join("/")}` || "/"
+    const basePath = props.tab.proxyBasePath
+    return `${basePath}${normalizedPath}${parsed.search}${parsed.hash}`
+  }
+
+  const syncPathInputFromFrame = () => {
+    try {
+      const currentHref = iframeRef?.contentWindow?.location.href
+      if (!currentHref) {
+        return
+      }
+      setPathInput(getEditablePathFromUrl(currentHref))
+    } catch {
+      setPathInput(getEditablePathFromUrl(frameSrc()))
+    }
+  }
+
+  createEffect(() => {
+    setFrameSrc(props.tab.shellUrl)
+    setPathInput(getEditablePathFromUrl(props.tab.shellUrl))
+  })
+
+  const handleBack = (event: MouseEvent) => {
+    event.preventDefault()
+    event.stopPropagation()
+
+    try {
+      const frameWindow = iframeRef?.contentWindow
+      if (!frameWindow) {
+        return
+      }
+
+      if (frameWindow.history.length <= 1) {
+        return
+      }
+
+      frameWindow.focus()
+      frameWindow.history.go(-1)
+    } catch {
+      // Ignore navigation errors from pages that do not expose history access.
+    }
+  }
+
+  const handleRefresh = () => {
+    try {
+      iframeRef?.contentWindow?.location.reload()
+      return
+    } catch {
+      // Fall back to resetting the iframe source if the frame cannot be reloaded directly.
+    }
+
+    setFrameSrc("about:blank")
+    requestAnimationFrame(() => setFrameSrc(props.tab.shellUrl))
+  }
+
+  const handleGo = (event?: Event) => {
+    event?.preventDefault()
+
+    const nextUrl = buildNormalizedTargetUrl(pathInput())
+    setFrameSrc(nextUrl)
+    setPathInput(getEditablePathFromUrl(nextUrl))
+  }
+
+  return (
+    <div class="flex h-full min-h-0 w-full flex-col bg-surface">
+      <div
+        class="flex shrink-0 items-center gap-2 px-3 py-2"
+        style={{ "border-bottom": "1px solid var(--border-base)" }}
+      >
+        <button
+          type="button"
+          class="new-tab-button"
+          onClick={handleBack}
+          title={t("sidecars.back")}
+          aria-label={t("sidecars.back")}
+        >
+          <ArrowLeft class="h-4 w-4" />
+        </button>
+        <button
+          type="button"
+          class="new-tab-button"
+          onClick={handleRefresh}
+          title={t("sidecars.refresh")}
+          aria-label={t("sidecars.refresh")}
+        >
+          <RefreshCw class="h-4 w-4" />
+        </button>
+        <div
+          class="shrink-0 rounded-md px-3 py-1.5 text-sm"
+          style={{
+            background: "var(--surface-secondary)",
+            color: "var(--text-secondary)",
+            border: "1px solid var(--border-base)",
+          }}
+        >
+          {lockedBaseLabel()}
+        </div>
+        <form class="flex min-w-0 flex-1 items-center gap-2" onSubmit={(event) => handleGo(event)}>
+          <input
+            type="text"
+            class="min-w-0 flex-1 rounded-md px-3 py-1.5 text-sm outline-none"
+            style={{
+              background: "var(--surface-secondary)",
+              color: "var(--text-primary)",
+              border: "1px solid var(--border-base)",
+            }}
+            value={pathInput()}
+            onInput={(event) => setPathInput(event.currentTarget.value)}
+            spellcheck={false}
+            autocomplete="off"
+            autocorrect="off"
+            autocapitalize="off"
+            aria-label={t("sidecars.path")}
+          />
+          <button
+            type="submit"
+            class="new-tab-button"
+            title={t("sidecars.go")}
+            aria-label={t("sidecars.go")}
+          >
+            <ArrowRight class="h-4 w-4" />
+          </button>
+        </form>
+      </div>
+      <iframe
+        ref={iframeRef}
+        src={frameSrc()}
+        title={props.tab.name}
+        class="min-h-0 flex-1 w-full border-0 bg-surface"
+        referrerPolicy="same-origin"
+        onLoad={syncPathInputFromFrame}
+      />
+    </div>
+  )
+}
--- a/packages/ui/src/lib/api-client.ts
+++ b/packages/ui/src/lib/api-client.ts
@@ -10,6 +10,7 @@ import type {
  SpeechCapabilitiesResponse,
  SpeechSynthesisResponse,
  SpeechTranscriptionResponse,
+  SideCar,
  ServerMeta,
  RemoteServerProbeRequest,
  RemoteServerProbeResponse,
@@ -193,6 +194,33 @@ export const serverApi = {
      body: JSON.stringify(payload),
    })
  },
+  fetchSidecars(): Promise<{ sidecars: SideCar[] }> {
+    return request<{ sidecars: SideCar[] }>("/api/sidecars")
+  },
+  createSidecar(payload: {
+    kind: "port"
+    name: string
+    port: number
+    insecure: boolean
+    prefixMode: "strip" | "preserve"
+  }): Promise<SideCar> {
+    return request<SideCar>("/api/sidecars", {
+      method: "POST",
+      body: JSON.stringify(payload),
+    })
+  },
+  updateSidecar(
+    id: string,
+    payload: Partial<{ name: string; port: number; insecure: boolean; prefixMode: "strip" | "preserve" }>,
+  ): Promise<SideCar> {
+    return request<SideCar>(`/api/sidecars/${encodeURIComponent(id)}`, {
+      method: "PUT",
+      body: JSON.stringify(payload),
+    })
+  },
+  deleteSidecar(id: string): Promise<void> {
+    return request(`/api/sidecars/${encodeURIComponent(id)}`, { method: "DELETE" })
+  },
  fetchServerMeta(): Promise<ServerMeta> {
    return request<ServerMeta>("/api/meta")
  },
@@ -438,4 +466,4 @@ function buildClientEventsUrl(identity: { clientId: string; connectionId: string
  return `${url.pathname}${url.search}`
 }

-export type { WorkspaceDescriptor, WorkspaceLogEntry, WorkspaceEventPayload, WorkspaceEventType }
+export type { WorkspaceDescriptor, WorkspaceLogEntry, WorkspaceEventPayload, WorkspaceEventType, SideCar }
--- a/packages/ui/src/lib/hooks/use-app-lifecycle.ts
+++ b/packages/ui/src/lib/hooks/use-app-lifecycle.ts
@@ -16,6 +16,7 @@ const log = getLogger("actions")
 interface UseAppLifecycleOptions {
  setEscapeInDebounce: (value: boolean) => void
  handleNewInstanceRequest: () => void
+  handleCloseActiveTab: () => Promise<void>
  handleCloseInstance: (instanceId: string) => Promise<void>
  handleNewSession: (instanceId: string) => Promise<void>
  handleCloseSession: (instanceId: string, sessionId: string) => Promise<void>
@@ -31,7 +32,7 @@ export function useAppLifecycle(options: UseAppLifecycleOptions) {

    setupTabKeyboardShortcuts(
      options.handleNewInstanceRequest,
-      options.handleCloseInstance,
+      options.handleCloseActiveTab,
      options.handleNewSession,
      options.handleCloseSession,
      () => {
--- a/packages/ui/src/lib/hooks/use-commands.ts
+++ b/packages/ui/src/lib/hooks/use-commands.ts
@@ -2,7 +2,8 @@ import { createSignal, onMount } from "solid-js"
 import type { Accessor } from "solid-js"
 import type { Preferences, ExpansionPreference, ToolInputsVisibilityPreference } from "../../stores/preferences"
 import { createCommandRegistry, type Command } from "../commands"
-import { instances, activeInstanceId, setActiveInstanceId } from "../../stores/instances"
+import { activeInstanceId } from "../../stores/instances"
+import { selectNextAppTab, selectPreviousAppTab } from "../../stores/app-tabs"
 import type { ClientPart, MessageInfo } from "../../types/message"
 import { getSessions, getVisibleSessionIds, setActiveSession, setActiveSessionFromList } from "../../stores/sessions"
 import { showAlertDialog } from "../../stores/alerts"
@@ -41,6 +42,7 @@ export interface UseCommandsOptions {
  setThinkingBlocksExpansion: (mode: ExpansionPreference) => void
  setToolInputsVisibility: (mode: ToolInputsVisibilityPreference) => void
  handleNewInstanceRequest: () => void
+  handleCloseActiveTab: () => Promise<void>
  handleCloseInstance: (instanceId: string) => Promise<void>
  handleNewSession: (instanceId: string) => Promise<void>
  handleCloseSession: (instanceId: string, sessionId: string) => Promise<void>
@@ -90,9 +92,7 @@ export function useCommands(options: UseCommandsOptions) {
      keywords: () => splitKeywords("commands.closeInstance.keywords"),
      shortcut: { key: "W", meta: true },
      action: async () => {
-        const instance = activeInstance()
-        if (!instance) return
-        await options.handleCloseInstance(instance.id)
+        await options.handleCloseActiveTab()
      },
    })

@@ -103,13 +103,7 @@ export function useCommands(options: UseCommandsOptions) {
      category: "Instance",
      keywords: () => splitKeywords("commands.nextInstance.keywords"),
      shortcut: { key: "]", meta: true },
-      action: () => {
-        const ids = Array.from(instances().keys())
-        if (ids.length <= 1) return
-        const current = ids.indexOf(activeInstanceId() || "")
-        const next = (current + 1) % ids.length
-        if (ids[next]) setActiveInstanceId(ids[next])
-      },
+      action: () => selectNextAppTab(),
    })

    commandRegistry.register({
@@ -119,13 +113,7 @@ export function useCommands(options: UseCommandsOptions) {
      category: "Instance",
      keywords: () => splitKeywords("commands.previousInstance.keywords"),
      shortcut: { key: "[", meta: true },
-      action: () => {
-        const ids = Array.from(instances().keys())
-        if (ids.length <= 1) return
-        const current = ids.indexOf(activeInstanceId() || "")
-        const prev = current <= 0 ? ids.length - 1 : current - 1
-        if (ids[prev]) setActiveInstanceId(ids[prev])
-      },
+      action: () => selectPreviousAppTab(),
    })

    commandRegistry.register({
--- a/packages/ui/src/lib/i18n/messages/en/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/en/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "Open folder picker to create new instance",
  "commands.newInstance.keywords": "folder, project, workspace",

-  "commands.closeInstance.label": "Close Instance",
-  "commands.closeInstance.description": "Stop current instance's server",
-  "commands.closeInstance.keywords": "stop, quit, close",
+  "commands.closeInstance.label": "Close Tab",
+  "commands.closeInstance.description": "Close the current top-level tab",
+  "commands.closeInstance.keywords": "stop, quit, close, tab",

-  "commands.nextInstance.label": "Next Instance",
-  "commands.nextInstance.description": "Cycle to next instance tab",
-  "commands.nextInstance.keywords": "switch, navigate",
+  "commands.nextInstance.label": "Next Tab",
+  "commands.nextInstance.description": "Cycle to the next top-level tab",
+  "commands.nextInstance.keywords": "switch, navigate, tab",

-  "commands.previousInstance.label": "Previous Instance",
-  "commands.previousInstance.description": "Cycle to previous instance tab",
-  "commands.previousInstance.keywords": "switch, navigate",
+  "commands.previousInstance.label": "Previous Tab",
+  "commands.previousInstance.description": "Cycle to the previous top-level tab",
+  "commands.previousInstance.keywords": "switch, navigate, tab",

  "commands.newSession.label": "New Session",
  "commands.newSession.description": "Create a new parent session",
--- a/packages/ui/src/lib/i18n/messages/en/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/en/folderSelection.ts
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "Connecting...",
  "folderSelection.servers.dialog.errorRequired": "Server name and URL are required.",
  "folderSelection.servers.dialog.errorConnect": "Could not connect to the remote server.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/en/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/en/settings.ts
@@ -195,4 +195,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "Saved",
  "settings.speech.save.unsaved": "Unsaved changes",
  "settings.speech.save.error": "Save failed",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/es/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/es/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "Abrir el selector de carpetas para crear una nueva instancia",
  "commands.newInstance.keywords": "carpeta, proyecto, workspace",

-  "commands.closeInstance.label": "Cerrar instancia",
-  "commands.closeInstance.description": "Detener el servidor de la instancia actual",
-  "commands.closeInstance.keywords": "detener, salir, cerrar",
+  "commands.closeInstance.label": "Cerrar pestaña",
+  "commands.closeInstance.description": "Cerrar la pestaña superior actual",
+  "commands.closeInstance.keywords": "detener, salir, cerrar, pestaña",

-  "commands.nextInstance.label": "Siguiente instancia",
-  "commands.nextInstance.description": "Cambiar a la siguiente pestaña de instancia",
-  "commands.nextInstance.keywords": "cambiar, navegar",
+  "commands.nextInstance.label": "Siguiente pestaña",
+  "commands.nextInstance.description": "Cambiar a la siguiente pestaña superior",
+  "commands.nextInstance.keywords": "cambiar, navegar, pestaña",

-  "commands.previousInstance.label": "Instancia anterior",
-  "commands.previousInstance.description": "Cambiar a la pestaña de instancia anterior",
-  "commands.previousInstance.keywords": "cambiar, navegar",
+  "commands.previousInstance.label": "Pestaña anterior",
+  "commands.previousInstance.description": "Cambiar a la pestaña superior anterior",
+  "commands.previousInstance.keywords": "cambiar, navegar, pestaña",

  "commands.newSession.label": "Nueva sesión",
  "commands.newSession.description": "Crear una nueva sesión principal",
--- a/packages/ui/src/lib/i18n/messages/es/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/es/folderSelection.ts
@@ -2,23 +2,23 @@ export const folderSelectionMessages = {
  "folderSelection.language.ariaLabel": "Idioma",

  "folderSelection.logoAlt": "Logo de CodeNomad",
-  "folderSelection.tagline": "Selecciona una carpeta para empezar a programar con IA",
+  "folderSelection.tagline": "Selecciona una carpeta para empezar a programar con AI",

  "folderSelection.links.github": "GitHub de CodeNomad",
-  "folderSelection.links.githubStars": "Estrellas de CodeNomad en GitHub",
+  "folderSelection.links.githubStars": "Estrellas de GitHub de CodeNomad",
  "folderSelection.links.discord": "Discord de CodeNomad",

  "folderSelection.empty.title": "No hay carpetas recientes",
-  "folderSelection.empty.description": "Explora una carpeta para comenzar",
+  "folderSelection.empty.description": "Busca una carpeta para comenzar",

  "folderSelection.recent.title": "Carpetas recientes",
  "folderSelection.recent.subtitle.one": "{count} carpeta disponible",
  "folderSelection.recent.subtitle.other": "{count} carpetas disponibles",
-  "folderSelection.recent.remove": "Quitar de recientes",
+  "folderSelection.recent.remove": "Eliminar de recientes",

-  "folderSelection.browse.title": "Explorar carpetas",
+  "folderSelection.browse.title": "Buscar carpeta",
  "folderSelection.browse.subtitle": "Selecciona cualquier carpeta en tu ordenador",
-  "folderSelection.browse.button": "Explorar carpetas",
+  "folderSelection.browse.button": "Buscar carpetas",
  "folderSelection.browse.buttonOpening": "Abriendo...",
  "folderSelection.actions.title": "Abrir carpeta o conectar servidor",
  "folderSelection.actions.subtitle": "Abre una carpeta local o conéctate a un servidor de CodeNomad",
@@ -29,11 +29,11 @@ export const folderSelectionMessages = {

  "folderSelection.hints.navigate": "Navegar",
  "folderSelection.hints.select": "Seleccionar",
-  "folderSelection.hints.remove": "Quitar",
-  "folderSelection.hints.browse": "Explorar",
+  "folderSelection.hints.remove": "Eliminar",
+  "folderSelection.hints.browse": "Buscar",

  "folderSelection.loading.title": "Iniciando instancia...",
-  "folderSelection.loading.subtitle": "Espera un momento mientras preparamos tu workspace.",
+  "folderSelection.loading.subtitle": "Espera mientras preparamos tu espacio de trabajo.",

  "folderSelection.drop.title": "Suelta una carpeta para abrirla",
  "folderSelection.drop.subtitle": "Inicia una nueva instancia en la carpeta soltada.",
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "Conectando...",
  "folderSelection.servers.dialog.errorRequired": "El nombre y la URL del servidor son obligatorios.",
  "folderSelection.servers.dialog.errorConnect": "No se pudo conectar al servidor remoto.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/es/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/es/settings.ts
@@ -194,4 +194,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "Guardado",
  "settings.speech.save.unsaved": "Cambios sin guardar",
  "settings.speech.save.error": "Error al guardar",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/fr/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/fr/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "Ouvrir le sélecteur de dossiers pour créer une nouvelle instance",
  "commands.newInstance.keywords": "dossier, projet, espace de travail",

-  "commands.closeInstance.label": "Fermer l'instance",
-  "commands.closeInstance.description": "Arrêter le serveur de l'instance actuelle",
-  "commands.closeInstance.keywords": "arrêter, quitter, fermer",
+  "commands.closeInstance.label": "Fermer l'onglet",
+  "commands.closeInstance.description": "Fermer l'onglet de premier niveau actuel",
+  "commands.closeInstance.keywords": "arrêter, quitter, fermer, onglet",

-  "commands.nextInstance.label": "Instance suivante",
-  "commands.nextInstance.description": "Passer à l'onglet d'instance suivant",
-  "commands.nextInstance.keywords": "changer, naviguer, suivant",
+  "commands.nextInstance.label": "Onglet suivant",
+  "commands.nextInstance.description": "Passer à l'onglet de premier niveau suivant",
+  "commands.nextInstance.keywords": "changer, naviguer, suivant, onglet",

-  "commands.previousInstance.label": "Instance précédente",
-  "commands.previousInstance.description": "Passer à l'onglet d'instance précédent",
-  "commands.previousInstance.keywords": "changer, naviguer, précédent",
+  "commands.previousInstance.label": "Onglet précédent",
+  "commands.previousInstance.description": "Passer à l'onglet de premier niveau précédent",
+  "commands.previousInstance.keywords": "changer, naviguer, précédent, onglet",

  "commands.newSession.label": "Nouvelle session",
  "commands.newSession.description": "Créer une nouvelle session parente",
--- a/packages/ui/src/lib/i18n/messages/fr/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/fr/folderSelection.ts
@@ -5,7 +5,7 @@ export const folderSelectionMessages = {
  "folderSelection.tagline": "Sélectionnez un dossier pour commencer à coder avec l'IA",

  "folderSelection.links.github": "GitHub de CodeNomad",
-  "folderSelection.links.githubStars": "Stars GitHub de CodeNomad",
+  "folderSelection.links.githubStars": "Étoiles GitHub de CodeNomad",
  "folderSelection.links.discord": "Discord de CodeNomad",

  "folderSelection.empty.title": "Aucun dossier récent",
@@ -16,13 +16,13 @@ export const folderSelectionMessages = {
  "folderSelection.recent.subtitle.other": "{count} dossiers disponibles",
  "folderSelection.recent.remove": "Retirer des récents",

-  "folderSelection.browse.title": "Parcourir les dossiers",
+  "folderSelection.browse.title": "Parcourir un dossier",
  "folderSelection.browse.subtitle": "Sélectionnez n'importe quel dossier sur votre ordinateur",
  "folderSelection.browse.button": "Parcourir les dossiers",
  "folderSelection.browse.buttonOpening": "Ouverture...",
-  "folderSelection.actions.title": "Ouvrir un dossier ou connecter un serveur",
+  "folderSelection.actions.title": "Ouvrir un dossier ou se connecter à un serveur",
  "folderSelection.actions.subtitle": "Ouvrez un dossier local ou connectez-vous à un serveur CodeNomad",
-  "folderSelection.actions.connectButton": "Connecter un serveur CodeNomad",
+  "folderSelection.actions.connectButton": "Se connecter au serveur CodeNomad",

  "folderSelection.advancedSettings": "Paramètres avancés",
  "folderSelection.opencode": "OpenCode",
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "Connexion...",
  "folderSelection.servers.dialog.errorRequired": "Le nom du serveur et l'URL sont requis.",
  "folderSelection.servers.dialog.errorConnect": "Impossible de se connecter au serveur distant.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/fr/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/fr/settings.ts
@@ -194,4 +194,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "Enregistré",
  "settings.speech.save.unsaved": "Modifications non enregistrées",
  "settings.speech.save.error": "Échec de l'enregistrement",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/he/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/he/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "פתח בורר תיקיות ליצירת מופע חדש",
  "commands.newInstance.keywords": "תיקייה, פרויקט, סביבת עבודה",

-  "commands.closeInstance.label": "סגור מופע",
-  "commands.closeInstance.description": "עצור את השרת של המופע הנוכחי",
-  "commands.closeInstance.keywords": "עצור, סגור",
+  "commands.closeInstance.label": "סגור לשונית",
+  "commands.closeInstance.description": "סגור את הלשונית העליונה הנוכחית",
+  "commands.closeInstance.keywords": "עצור, סגור, לשונית",

-  "commands.nextInstance.label": "מופע הבא",
-  "commands.nextInstance.description": "עבור למופע הבא",
-  "commands.nextInstance.keywords": "החלף, נווט",
+  "commands.nextInstance.label": "הלשונית הבאה",
+  "commands.nextInstance.description": "עבור ללשונית העליונה הבאה",
+  "commands.nextInstance.keywords": "החלף, נווט, לשונית",

-  "commands.previousInstance.label": "מופע קודם",
-  "commands.previousInstance.description": "עבור למופע הקודם",
-  "commands.previousInstance.keywords": "החלף, נווט",
+  "commands.previousInstance.label": "הלשונית הקודמת",
+  "commands.previousInstance.description": "עבור ללשונית העליונה הקודמת",
+  "commands.previousInstance.keywords": "החלף, נווט, לשונית",

  "commands.newSession.label": "סשן חדש",
  "commands.newSession.description": "צור סשן הורה חדש",
--- a/packages/ui/src/lib/i18n/messages/he/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/he/folderSelection.ts
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "מתחבר...",
  "folderSelection.servers.dialog.errorRequired": "שם השרת והכתובת הם שדות חובה.",
  "folderSelection.servers.dialog.errorConnect": "לא ניתן היה להתחבר לשרת המרוחק.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/he/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/he/settings.ts
@@ -193,4 +193,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "נשמר",
  "settings.speech.save.unsaved": "יש שינויים שלא נשמרו",
  "settings.speech.save.error": "השמירה נכשלה",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/ja/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/ja/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "フォルダ選択を開いて新しいインスタンスを作成",
  "commands.newInstance.keywords": "フォルダ, プロジェクト, ワークスペース, folder, project, workspace",

-  "commands.closeInstance.label": "インスタンスを閉じる",
-  "commands.closeInstance.description": "現在のインスタンスのサーバーを停止",
-  "commands.closeInstance.keywords": "停止, 終了, 閉じる, stop, quit, close",
+  "commands.closeInstance.label": "タブを閉じる",
+  "commands.closeInstance.description": "現在のトップレベルタブを閉じる",
+  "commands.closeInstance.keywords": "閉じる, タブ, stop, quit, close",

-  "commands.nextInstance.label": "次のインスタンス",
-  "commands.nextInstance.description": "次のインスタンスタブへ切り替え",
-  "commands.nextInstance.keywords": "切り替え, 移動, switch, navigate",
+  "commands.nextInstance.label": "次のタブ",
+  "commands.nextInstance.description": "次のトップレベルタブへ切り替え",
+  "commands.nextInstance.keywords": "切り替え, 移動, タブ, switch, navigate",

-  "commands.previousInstance.label": "前のインスタンス",
-  "commands.previousInstance.description": "前のインスタンスタブへ切り替え",
-  "commands.previousInstance.keywords": "切り替え, 移動, switch, navigate",
+  "commands.previousInstance.label": "前のタブ",
+  "commands.previousInstance.description": "前のトップレベルタブへ切り替え",
+  "commands.previousInstance.keywords": "切り替え, 移動, タブ, switch, navigate",

  "commands.newSession.label": "新しいセッション",
  "commands.newSession.description": "新しい親セッションを作成",
--- a/packages/ui/src/lib/i18n/messages/ja/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/ja/folderSelection.ts
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "接続中...",
  "folderSelection.servers.dialog.errorRequired": "サーバー名と URL は必須です。",
  "folderSelection.servers.dialog.errorConnect": "リモートサーバーに接続できませんでした。",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/ja/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/ja/settings.ts
@@ -194,4 +194,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "保存済み",
  "settings.speech.save.unsaved": "未保存の変更",
  "settings.speech.save.error": "保存に失敗しました",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/ru/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/ru/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "Открыть выбор папки для создания нового экземпляра",
  "commands.newInstance.keywords": "папка, проект, рабочее пространство",

-  "commands.closeInstance.label": "Закрыть экземпляр",
-  "commands.closeInstance.description": "Остановить сервер текущего экземпляра",
-  "commands.closeInstance.keywords": "остановить, выйти, закрыть",
+  "commands.closeInstance.label": "Закрыть вкладку",
+  "commands.closeInstance.description": "Закрыть текущую верхнеуровневую вкладку",
+  "commands.closeInstance.keywords": "остановить, выйти, закрыть, вкладка",

-  "commands.nextInstance.label": "Следующий экземпляр",
-  "commands.nextInstance.description": "Переключиться на следующую вкладку экземпляра",
-  "commands.nextInstance.keywords": "переключить, навигация",
+  "commands.nextInstance.label": "Следующая вкладка",
+  "commands.nextInstance.description": "Переключиться на следующую верхнеуровневую вкладку",
+  "commands.nextInstance.keywords": "переключить, навигация, вкладка",

-  "commands.previousInstance.label": "Предыдущий экземпляр",
-  "commands.previousInstance.description": "Переключиться на предыдущую вкладку экземпляра",
-  "commands.previousInstance.keywords": "переключить, навигация",
+  "commands.previousInstance.label": "Предыдущая вкладка",
+  "commands.previousInstance.description": "Переключиться на предыдущую верхнеуровневую вкладку",
+  "commands.previousInstance.keywords": "переключить, навигация, вкладка",

  "commands.newSession.label": "Новая сессия",
  "commands.newSession.description": "Создать новую родительскую сессию",
--- a/packages/ui/src/lib/i18n/messages/ru/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/ru/folderSelection.ts
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "Подключение...",
  "folderSelection.servers.dialog.errorRequired": "Имя сервера и URL обязательны.",
  "folderSelection.servers.dialog.errorConnect": "Не удалось подключиться к удаленному серверу.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/ru/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/ru/settings.ts
@@ -194,4 +194,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "Сохранено",
  "settings.speech.save.unsaved": "Есть несохранённые изменения",
  "settings.speech.save.error": "Не удалось сохранить",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/i18n/messages/zh-Hans/commands.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-Hans/commands.ts
@@ -15,17 +15,17 @@ export const commandMessages = {
  "commands.newInstance.description": "打开文件夹选择器以创建新实例",
  "commands.newInstance.keywords": "folder, project, workspace, 文件夹, 项目, 工作区",

-  "commands.closeInstance.label": "关闭实例",
-  "commands.closeInstance.description": "停止当前实例的服务器",
-  "commands.closeInstance.keywords": "stop, quit, close, 停止, 退出, 关闭",
+  "commands.closeInstance.label": "关闭标签页",
+  "commands.closeInstance.description": "关闭当前顶层标签页",
+  "commands.closeInstance.keywords": "stop, quit, close, 停止, 退出, 关闭, 标签",

-  "commands.nextInstance.label": "下一个实例",
-  "commands.nextInstance.description": "切换到下一个实例标签页",
-  "commands.nextInstance.keywords": "switch, navigate, 切换, 导航",
+  "commands.nextInstance.label": "下一个标签页",
+  "commands.nextInstance.description": "切换到下一个顶层标签页",
+  "commands.nextInstance.keywords": "switch, navigate, 切换, 导航, 标签",

-  "commands.previousInstance.label": "上一个实例",
-  "commands.previousInstance.description": "切换到上一个实例标签页",
-  "commands.previousInstance.keywords": "switch, navigate, 切换, 导航",
+  "commands.previousInstance.label": "上一个标签页",
+  "commands.previousInstance.description": "切换到上一个顶层标签页",
+  "commands.previousInstance.keywords": "switch, navigate, 切换, 导航, 标签",

  "commands.newSession.label": "新建会话",
  "commands.newSession.description": "创建新的父会话",
--- a/packages/ui/src/lib/i18n/messages/zh-Hans/folderSelection.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-Hans/folderSelection.ts
@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
  "folderSelection.servers.dialog.connecting": "连接中...",
  "folderSelection.servers.dialog.errorRequired": "服务器名称和 URL 为必填项。",
  "folderSelection.servers.dialog.errorConnect": "无法连接到远程服务器。",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const
--- a/packages/ui/src/lib/i18n/messages/zh-Hans/settings.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-Hans/settings.ts
@@ -194,4 +194,40 @@ export const settingsMessages = {
  "settings.speech.save.saved": "已保存",
  "settings.speech.save.unsaved": "有未保存的更改",
  "settings.speech.save.error": "保存失败",
+  "settings.nav.sidecars": "SideCars",
+  "settings.section.sidecars.eyebrow": "Server services",
+  "settings.section.sidecars.title": "SideCars",
+  "settings.section.sidecars.subtitle": "Configure local services listening on fixed ports that the server can proxy into tabs.",
+  "sidecars.form.name": "Name",
+  "sidecars.form.validation": "Enter a valid SideCar name and port.",
+  "sidecars.form.port": "Port",
+  "sidecars.form.insecure": "Use HTTP",
+  "sidecars.form.protocol": "Protocol",
+  "sidecars.form.protocol.help": "Choose how the proxy should connect to the local service.",
+  "sidecars.form.protocol.https": "HTTPS",
+  "sidecars.form.protocol.http": "HTTP",
+  "sidecars.form.prefixMode": "Prefix mode",
+  "sidecars.form.prefixMode.help": "Choose whether the SideCar receives the public /sidecars path prefix.",
+  "sidecars.form.prefixMode.strip": "Strip prefix",
+  "sidecars.form.prefixMode.preserve": "Preserve prefix",
+  "sidecars.form.add": "Add SideCar",
+  "sidecars.kind.port": "Port",
+  "sidecars.status.running": "Running",
+  "sidecars.status.stopped": "Stopped",
+  "sidecars.basePath": "Base path",
+  "sidecars.settings.listTitle": "Configured SideCars",
+  "sidecars.settings.listSubtitle": "Review the port-based SideCars available in the picker.",
+  "sidecars.settings.empty": "No SideCars configured yet.",
+  "sidecars.picker.title": "Open SideCar",
+  "sidecars.picker.loading": "Loading SideCars...",
+  "sidecars.picker.subtitle": "Choose an available SideCar to open in a new tab.",
+  "sidecars.picker.empty": "No port-based SideCars are available yet.",
+  "sidecars.picker.close": "Close",
+  "sidecars.open.errorTitle": "Unable to open SideCar",
+  "sidecars.open.notFound": "SideCar not found.",
+  "sidecars.open.notRunning": "SideCar is not reachable on its configured port.",
+  "sidecars.back": "Back",
+  "sidecars.refresh": "Refresh",
+  "sidecars.path": "Path",
+  "sidecars.go": "Go",
 } as const
--- a/packages/ui/src/lib/keyboard.ts
+++ b/packages/ui/src/lib/keyboard.ts
@@ -1,11 +1,12 @@
-import { instances, activeInstanceId, setActiveInstanceId } from "../stores/instances"
+import { activeInstanceId } from "../stores/instances"
+import { selectAppTabByIndex } from "../stores/app-tabs"
 import { activeSessionId, setActiveSession, getSessions, activeParentSessionId } from "../stores/sessions"
 import { keyboardRegistry } from "./keyboard-registry"
 import { isMac } from "./keyboard-utils"

 export function setupTabKeyboardShortcuts(
  handleNewInstance: () => void,
-  handleCloseInstance: (instanceId: string) => void,
+  handleCloseActiveTab: () => Promise<void>,
  handleNewSession: (instanceId: string) => void,
  handleCloseSession: (instanceId: string, sessionId: string) => void,
  handleCommandPalette: () => void,
@@ -35,11 +36,7 @@ export function setupTabKeyboardShortcuts(

    if ((e.metaKey || e.ctrlKey) && !e.shiftKey && e.key >= "1" && e.key <= "9") {
      e.preventDefault()
-      const index = parseInt(e.key) - 1
-      const instanceIds = Array.from(instances().keys())
-      if (instanceIds[index]) {
-        setActiveInstanceId(instanceIds[index])
-      }
+      selectAppTabByIndex(parseInt(e.key) - 1)
    }

    if ((e.metaKey || e.ctrlKey) && e.shiftKey && e.key >= "1" && e.key <= "9") {
@@ -67,10 +64,7 @@ export function setupTabKeyboardShortcuts(

    if ((e.metaKey || e.ctrlKey) && !e.shiftKey && e.key.toLowerCase() === "w") {
      e.preventDefault()
-      const instanceId = activeInstanceId()
-      if (instanceId) {
-        handleCloseInstance(instanceId)
-      }
+      void handleCloseActiveTab()
    }

    if ((e.metaKey || e.ctrlKey) && e.shiftKey && e.key.toLowerCase() === "w") {
--- a/packages/ui/src/lib/shortcuts/navigation.ts
+++ b/packages/ui/src/lib/shortcuts/navigation.ts
@@ -1,5 +1,6 @@
 import { keyboardRegistry } from "../keyboard-registry"
-import { instances, activeInstanceId, setActiveInstanceId } from "../../stores/instances"
+import { activeInstanceId } from "../../stores/instances"
+import { selectNextAppTab, selectPreviousAppTab } from "../../stores/app-tabs"
 import { activeSessionId, getVisibleSessionIds, setActiveSession, setActiveSessionFromList } from "../../stores/sessions"

 export function registerNavigationShortcuts() {
@@ -11,14 +12,8 @@ export function registerNavigationShortcuts() {
    id: "instance-prev",
    key: "[",
    modifiers: { ctrl: !isMac(), meta: isMac() },
-    handler: () => {
-      const ids = Array.from(instances().keys())
-      if (ids.length <= 1) return
-      const current = ids.indexOf(activeInstanceId() || "")
-      const prev = current <= 0 ? ids.length - 1 : current - 1
-      if (ids[prev]) setActiveInstanceId(ids[prev])
-    },
-    description: "previous instance",
+    handler: () => selectPreviousAppTab(),
+    description: "previous tab",
    context: "global",
  })

@@ -26,14 +21,8 @@ export function registerNavigationShortcuts() {
    id: "instance-next",
    key: "]",
    modifiers: { ctrl: !isMac(), meta: isMac() },
-    handler: () => {
-      const ids = Array.from(instances().keys())
-      if (ids.length <= 1) return
-      const current = ids.indexOf(activeInstanceId() || "")
-      const next = (current + 1) % ids.length
-      if (ids[next]) setActiveInstanceId(ids[next])
-    },
-    description: "next instance",
+    handler: () => selectNextAppTab(),
+    description: "next tab",
    context: "global",
  })

--- a/packages/ui/src/stores/app-tabs.ts
+++ b/packages/ui/src/stores/app-tabs.ts
@@ -0,0 +1,172 @@
+import { createMemo, createSignal } from "solid-js"
+import type { Instance } from "../types/instance"
+import { activeInstanceId, instances, setActiveInstanceId } from "./instances"
+import { activeSidecarToken, setActiveSidecarToken, sidecarTabs, type SideCarTabRecord } from "./sidecars"
+
+export interface InstanceAppTab {
+  id: string
+  kind: "instance"
+  instance: Instance
+}
+
+export interface SideCarAppTab {
+  id: string
+  kind: "sidecar"
+  sidecarTab: SideCarTabRecord
+}
+
+export type AppTabRecord = InstanceAppTab | SideCarAppTab
+
+function getInstanceAppTabId(instanceId: string): string {
+  return `instance:${instanceId}`
+}
+
+function getSidecarAppTabId(token: string): string {
+  return `sidecar:${token}`
+}
+
+function getAdjacentAppTabId(tabId: string): string | null {
+  const tabs = appTabs()
+  const index = tabs.findIndex((tab) => tab.id === tabId)
+  if (index < 0) return activeAppTabId()
+  return tabs[index - 1]?.id ?? tabs[index + 1]?.id ?? null
+}
+
+function getPreferredTabId(): string | null {
+  const sidecarToken = activeSidecarToken()
+  if (sidecarToken) {
+    return getSidecarAppTabId(sidecarToken)
+  }
+
+  const instanceId = activeInstanceId()
+  if (instanceId) {
+    return getInstanceAppTabId(instanceId)
+  }
+
+  return null
+}
+
+const [activeAppTabId, setActiveAppTabId] = createSignal<string | null>(null)
+const [tabOrder, setTabOrder] = createSignal<string[]>([])
+
+function rememberTabOrder(tabId: string) {
+  setTabOrder((prev) => (prev.includes(tabId) ? prev : [...prev, tabId]))
+}
+
+const appTabs = createMemo<AppTabRecord[]>(() => {
+  const currentTabs = [
+    ...Array.from(instances().values()).map((instance) => ({
+      id: getInstanceAppTabId(instance.id),
+      kind: "instance" as const,
+      instance,
+    })),
+    ...sidecarTabs().map((sidecarTab) => ({
+      id: getSidecarAppTabId(sidecarTab.token),
+      kind: "sidecar" as const,
+      sidecarTab,
+    })),
+  ]
+
+  const tabsById = new Map(currentTabs.map((tab) => [tab.id, tab]))
+  const orderedIds = tabOrder().filter((tabId) => tabsById.has(tabId))
+  const missingIds = currentTabs.map((tab) => tab.id).filter((tabId) => !orderedIds.includes(tabId))
+
+  return [...orderedIds, ...missingIds].map((tabId) => tabsById.get(tabId)!).filter(Boolean)
+})
+
+const activeAppTab = createMemo(() => appTabs().find((tab) => tab.id === activeAppTabId()) ?? null)
+
+function getAppTabById(tabId: string | null): AppTabRecord | null {
+  if (!tabId) return null
+  return appTabs().find((tab) => tab.id === tabId) ?? null
+}
+
+function selectAppTab(tabId: string | null) {
+  if (!tabId) {
+    setActiveAppTabId(null)
+    setActiveSidecarToken(null)
+    return
+  }
+
+  const tab = appTabs().find((entry) => entry.id === tabId)
+  if (!tab) return
+
+  rememberTabOrder(tab.id)
+  setActiveAppTabId(tab.id)
+
+  if (tab.kind === "instance") {
+    setActiveSidecarToken(null)
+    setActiveInstanceId(tab.instance.id)
+    return
+  }
+
+  setActiveInstanceId(null)
+  setActiveSidecarToken(tab.sidecarTab.token)
+}
+
+function selectInstanceTab(instanceId: string) {
+  selectAppTab(getInstanceAppTabId(instanceId))
+}
+
+function selectSidecarTab(token: string) {
+  selectAppTab(getSidecarAppTabId(token))
+}
+
+function selectNextAppTab() {
+  const tabs = appTabs()
+  if (tabs.length <= 1) return
+
+  const current = tabs.findIndex((tab) => tab.id === activeAppTabId())
+  const nextIndex = current < 0 ? 0 : (current + 1) % tabs.length
+  const nextTab = tabs[nextIndex]
+  if (nextTab) selectAppTab(nextTab.id)
+}
+
+function selectPreviousAppTab() {
+  const tabs = appTabs()
+  if (tabs.length <= 1) return
+
+  const current = tabs.findIndex((tab) => tab.id === activeAppTabId())
+  const previousIndex = current <= 0 ? tabs.length - 1 : current - 1
+  const previousTab = tabs[previousIndex]
+  if (previousTab) selectAppTab(previousTab.id)
+}
+
+function selectAppTabByIndex(index: number) {
+  const tab = appTabs()[index]
+  if (tab) selectAppTab(tab.id)
+}
+
+function ensureActiveAppTab(preferredTabId?: string | null) {
+  const tabs = appTabs()
+  const current = activeAppTabId()
+
+  if (current && tabs.some((tab) => tab.id === current)) {
+    return
+  }
+
+  const candidateId = preferredTabId ?? getPreferredTabId()
+  if (candidateId && tabs.some((tab) => tab.id === candidateId)) {
+    selectAppTab(candidateId)
+    return
+  }
+
+  selectAppTab(tabs[0]?.id ?? null)
+}
+
+export {
+  activeAppTabId,
+  activeAppTab,
+  appTabs,
+  ensureActiveAppTab,
+  getAdjacentAppTabId,
+  getAppTabById,
+  getInstanceAppTabId,
+  getSidecarAppTabId,
+  selectAppTab,
+  selectAppTabByIndex,
+  selectInstanceTab,
+  selectNextAppTab,
+  selectPreviousAppTab,
+  selectSidecarTab,
+}
--- a/packages/ui/src/stores/instances.ts
+++ b/packages/ui/src/stores/instances.ts
@@ -36,6 +36,7 @@ import { clearCacheForInstance } from "../lib/global-cache"
 import { getLogger } from "../lib/logger"
 import { mergeInstanceMetadata, clearInstanceMetadata } from "./instance-metadata"
 import { showWorkspaceLaunchError } from "./launch-errors"
+import { activeSidecarToken } from "./sidecars"

 const log = getLogger("api")

@@ -109,6 +110,8 @@ function workspaceDescriptorToInstance(descriptor: WorkspaceDescriptor): Instanc
 }

 function ensureActiveInstanceSelected(): void {
+  if (activeSidecarToken()) return
+
  const current = activeInstanceId()
  const instanceMap = instances()
  if (current && instanceMap.has(current)) return
--- a/packages/ui/src/stores/settings-screen.ts
+++ b/packages/ui/src/stores/settings-screen.ts
@@ -1,6 +1,6 @@
 import { createSignal } from "solid-js"

-export type SettingsSectionId = "appearance" | "notifications" | "remote" | "speech" | "opencode"
+export type SettingsSectionId = "appearance" | "notifications" | "remote" | "speech" | "opencode" | "sidecars"

 const [settingsOpen, setSettingsOpen] = createSignal(false)
 const [activeSettingsSection, setActiveSettingsSection] = createSignal<SettingsSectionId>("appearance")
--- a/packages/ui/src/stores/sidecars.ts
+++ b/packages/ui/src/stores/sidecars.ts
@@ -0,0 +1,149 @@
+import { createMemo, createSignal } from "solid-js"
+import { serverApi } from "../lib/api-client"
+import { tGlobal } from "../lib/i18n"
+import { serverEvents } from "../lib/server-events"
+import { getLogger } from "../lib/logger"
+import type { SideCar } from "../../../server/src/api-types"
+
+const log = getLogger("api")
+
+export interface SideCarTabRecord {
+  token: string
+  sidecarId: string
+  name: string
+  port?: number
+  prefixMode: SideCar["prefixMode"]
+  proxyBasePath: string
+  shellUrl: string
+}
+
+function buildSidecarShellUrl(sidecarId: string): string {
+  return `/sidecars/${encodeURIComponent(sidecarId)}/`
+}
+
+const [sidecars, setSidecars] = createSignal<Map<string, SideCar>>(new Map())
+const [sidecarTabs, setSidecarTabs] = createSignal<SideCarTabRecord[]>([])
+const [activeSidecarToken, setActiveSidecarToken] = createSignal<string | null>(null)
+const [sidecarsLoading, setSidecarsLoading] = createSignal(false)
+
+let loadPromise: Promise<void> | null = null
+
+async function ensureSidecarsLoaded() {
+  if (loadPromise) return loadPromise
+  setSidecarsLoading(true)
+  loadPromise = serverApi.fetchSidecars()
+    .then((result) => {
+      setSidecars(new Map(result.sidecars.map((sidecar) => [sidecar.id, sidecar])))
+    })
+    .catch((error) => {
+      log.error("Failed to load SideCars", error)
+    })
+    .finally(() => {
+      setSidecarsLoading(false)
+      loadPromise = null
+    })
+  return loadPromise
+}
+
+function upsertSidecar(sidecar: SideCar) {
+  setSidecars((prev) => {
+    const next = new Map(prev)
+    next.set(sidecar.id, sidecar)
+    return next
+  })
+
+  setSidecarTabs((prev) =>
+    prev.map((tab) =>
+      tab.sidecarId === sidecar.id
+        ? {
+            ...tab,
+            name: sidecar.name,
+            port: sidecar.port,
+            prefixMode: sidecar.prefixMode,
+            proxyBasePath: buildSidecarShellUrl(sidecar.id).replace(/\/$/, ""),
+            shellUrl: buildSidecarShellUrl(sidecar.id),
+          }
+        : tab,
+    ),
+  )
+}
+
+function removeSidecar(sidecarId: string) {
+  setSidecars((prev) => {
+    const next = new Map(prev)
+    next.delete(sidecarId)
+    return next
+  })
+
+  setSidecarTabs((prev) => {
+    const next = prev.filter((tab) => tab.sidecarId !== sidecarId)
+    if (!next.some((tab) => tab.token === activeSidecarToken())) {
+      setActiveSidecarToken(next[0]?.token ?? null)
+    }
+    return next
+  })
+}
+
+serverEvents.on("sidecar.updated", (event) => {
+  if (event.type !== "sidecar.updated") return
+  upsertSidecar(event.sidecar)
+})
+
+serverEvents.on("sidecar.removed", (event) => {
+  if (event.type !== "sidecar.removed") return
+  removeSidecar(event.sidecarId)
+})
+
+async function openSidecarTab(sidecarId: string) {
+  await ensureSidecarsLoaded()
+
+  const sidecar = sidecars().get(sidecarId)
+  if (!sidecar) {
+    throw new Error(tGlobal("sidecars.open.notFound"))
+  }
+  if (sidecar.status !== "running") {
+    throw new Error(tGlobal("sidecars.open.notRunning"))
+  }
+
+  const token = `${sidecarId}:${Date.now().toString(36)}`
+  const nextTab: SideCarTabRecord = {
+    token,
+    sidecarId,
+    name: sidecar.name,
+    port: sidecar.port,
+    prefixMode: sidecar.prefixMode,
+    proxyBasePath: buildSidecarShellUrl(sidecarId).replace(/\/$/, ""),
+    shellUrl: buildSidecarShellUrl(sidecarId),
+  }
+
+  setSidecarTabs((prev) => [...prev, nextTab])
+  setActiveSidecarToken(nextTab.token)
+  return nextTab
+}
+
+function closeSidecarTab(token: string) {
+  setSidecarTabs((prev) => {
+    const index = prev.findIndex((tab) => tab.token === token)
+    if (index < 0) return prev
+    const next = prev.filter((tab) => tab.token !== token)
+    if (activeSidecarToken() === token) {
+      const fallback = next[index - 1] ?? next[index] ?? null
+      setActiveSidecarToken(fallback?.token ?? null)
+    }
+    return next
+  })
+}
+
+const activeSidecarTab = createMemo(() => sidecarTabs().find((tab) => tab.token === activeSidecarToken()) ?? null)
+
+export {
+  sidecars,
+  sidecarTabs,
+  activeSidecarToken,
+  activeSidecarTab,
+  sidecarsLoading,
+  setActiveSidecarToken,
+  ensureSidecarsLoaded,
+  openSidecarTab,
+  closeSidecarTab,
+}
--- a/packages/ui/src/styles/panels/tabs.css
+++ b/packages/ui/src/styles/panels/tabs.css
@@ -154,6 +154,31 @@
  ring-offset-color: var(--surface-base);
 }

+.tab-pill {
+  @apply inline-flex items-center gap-1 px-3 py-2 rounded-t-md max-w-[220px] text-sm;
+  background-color: var(--tab-inactive-bg);
+  color: var(--tab-inactive-text);
+  border-bottom: 2px solid var(--tab-active-bg);
+}
+
+.tab-pill-active {
+  background-color: var(--tab-active-bg);
+  color: var(--tab-active-text);
+  border-bottom-color: var(--accent-primary);
+}
+
+.tab-pill-button {
+  @apply truncate;
+}
+
+.tab-pill-close {
+  @apply inline-flex items-center justify-center rounded w-5 h-5 text-xs;
+}
+
+.tab-pill-close:hover {
+  background-color: var(--new-tab-hover-bg);
+}
+
 /* Session tabs */
 .session-tab-base {
  @apply inline-flex items-center gap-2 px-3 py-1.5 rounded-t-md max-w-[150px] transition-colors text-sm;