diff --git a/.changeset/steady-codex-refresh.md b/.changeset/steady-codex-refresh.md
new file mode 100644
index 00000000000..2d8438541e1
--- /dev/null
+++ b/.changeset/steady-codex-refresh.md
@@ -0,0 +1,5 @@
+---
+"@kilocode/cli": patch
+---
+
+Prevent concurrent Kilo processes from reusing a ChatGPT Codex refresh token.
diff --git a/packages/opencode/src/kilocode/provider/codex-refresh.ts b/packages/opencode/src/kilocode/provider/codex-refresh.ts
index 81a160a3411..0d20e059e30 100644
--- a/packages/opencode/src/kilocode/provider/codex-refresh.ts
+++ b/packages/opencode/src/kilocode/provider/codex-refresh.ts
@@ -1,4 +1,4 @@
-import type { PluginInput } from "@kilocode/plugin"
+import { Flock } from "@opencode-ai/core/util/flock"
 
 export class CodexAuthExpiredError extends Error {
   constructor(
@@ -25,14 +25,24 @@ type Tokens = {
 }
 
 type Input = {
-  input: PluginInput
+  input: {
+    client: {
+      auth: {
+        set: (input: { path: { id: string }; body: Auth }) => Promise<unknown>
+      }
+    }
+  }
   getAuth: () => Promise<unknown>
   auth: Auth
-  refresh: (refresh: string) => Promise<Tokens>
+  refresh: (refresh: string, signal: AbortSignal) => Promise<Tokens>
   account: (tokens: Tokens) => string | undefined
+  lock?: Flock.Options
+  timeout?: number
 }
 
 const pending = new Map<string, Promise<Auth>>()
+const lock = "codex-auth-refresh:openai"
+const timeout = 30_000
 
 function valid(auth: Auth) {
   return auth.access && auth.expires > Date.now()
@@ -59,43 +69,53 @@ function recoverable(err: unknown) {
 }
 
 export async function refreshCodexAuth(input: Input) {
-  const inflight = pending.get(input.auth.refresh)
+  const token = input.auth.refresh
+  const inflight = pending.get(token)
   if (inflight) {
     const next = await inflight
     assign(input.auth, next)
     return next
   }
 
-  const promise = (async () => {
-    const fresh = await input.getAuth()
-    const current = oauth(fresh)
-    if (current && valid(current)) return current
-
-    try {
-      const base = current && current.refresh !== input.auth.refresh ? current : input.auth
-      const tokens = await input.refresh(base.refresh)
-      const id = input.account(tokens) || base.accountId
-      const next = {
-        type: "oauth" as const,
-        refresh: tokens.refresh_token,
-        access: tokens.access_token,
-        expires: Date.now() + (tokens.expires_in ?? 3600) * 1000,
-        ...(id && { accountId: id }),
+  const promise = Flock.withLock(
+    lock,
+    async () => {
+      const fresh = await input.getAuth()
+      const current = oauth(fresh)
+      if (current && valid(current)) return current
+
+      try {
+        const base = current && current.refresh !== token ? current : input.auth
+        const controller = new AbortController()
+        const timer = setTimeout(
+          () => controller.abort(new DOMException("The operation timed out.", "TimeoutError")),
+          input.timeout ?? timeout,
+        )
+        const tokens = await input.refresh(base.refresh, controller.signal).finally(() => clearTimeout(timer))
+        const id = input.account(tokens) || base.accountId
+        const next = {
+          type: "oauth" as const,
+          refresh: tokens.refresh_token,
+          access: tokens.access_token,
+          expires: Date.now() + (tokens.expires_in ?? 3600) * 1000,
+          ...(id && { accountId: id }),
+        }
+        await input.input.client.auth.set({ path: { id: "openai" }, body: next })
+        return next
+      } catch (err) {
+        if (!recoverable(err)) throw err
+
+        const latest = await input.getAuth()
+        const next = oauth(latest)
+        if (next && usable(next, token)) return next
+
+        throw new CodexAuthExpiredError()
       }
-      await input.input.client.auth.set({ path: { id: "openai" }, body: next })
-      return next
-    } catch (err) {
-      if (!recoverable(err)) throw err
-
-      const latest = await input.getAuth()
-      const next = oauth(latest)
-      if (next && usable(next, input.auth.refresh)) return next
-
-      throw new CodexAuthExpiredError()
-    }
-  })().finally(() => pending.delete(input.auth.refresh))
+    },
+    input.lock,
+  ).finally(() => pending.delete(token))
 
-  pending.set(input.auth.refresh, promise)
+  pending.set(token, promise)
   const next = await promise
   assign(input.auth, next)
   return next
diff --git a/packages/opencode/src/plugin/codex.ts b/packages/opencode/src/plugin/codex.ts
index 65892fa7111..887a1443385 100644
--- a/packages/opencode/src/plugin/codex.ts
+++ b/packages/opencode/src/plugin/codex.ts
@@ -142,10 +142,13 @@ async function exchangeCodeForTokens(code: string, redirectUri: string, pkce: Pk
   return response.json()
 }
 
-async function refreshAccessToken(refreshToken: string): Promise<TokenResponse> {
+// kilocode_change start
+async function refreshAccessToken(refreshToken: string, signal?: AbortSignal): Promise<TokenResponse> {
   const response = await fetch(`${ISSUER}/oauth/token`, {
     method: "POST",
-    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    signal,
+    headers: { "Content-Type": "application/x-www-form-urlencoded", "User-Agent": `kilo/${InstallationVersion}` },
+    // kilocode_change end
     body: new URLSearchParams({
       grant_type: "refresh_token",
       refresh_token: refreshToken,
diff --git a/packages/opencode/test/kilocode/agent-permission-overrides.test.ts b/packages/opencode/test/kilocode/agent-permission-overrides.test.ts
index 202af60df0c..d55f04629e9 100644
--- a/packages/opencode/test/kilocode/agent-permission-overrides.test.ts
+++ b/packages/opencode/test/kilocode/agent-permission-overrides.test.ts
@@ -99,7 +99,7 @@ test("system utility agents ignore per-agent permission allows", async () => {
     },
   })
 
-  await WithInstance.provide({
+  await provideTestInstance({
     directory: tmp.path,
     fn: async () => {
       const title = await load(tmp.path, (svc) => svc.get("title"))
@@ -131,7 +131,7 @@ test("system utility agents deny tools after configured name override", async ()
     },
   })
 
-  await WithInstance.provide({
+  await provideTestInstance({
     directory: tmp.path,
     fn: async () => {
       const title = await load(tmp.path, (svc) => svc.get("title"))
diff --git a/packages/opencode/test/kilocode/codex-auth-refresh.test.ts b/packages/opencode/test/kilocode/codex-auth-refresh.test.ts
index 28ea37c41ae..1388149615d 100644
--- a/packages/opencode/test/kilocode/codex-auth-refresh.test.ts
+++ b/packages/opencode/test/kilocode/codex-auth-refresh.test.ts
@@ -1,8 +1,11 @@
 import { describe, expect, test } from "bun:test"
 import { CodexAuthExpiredError, refreshCodexAuth } from "../../src/kilocode/provider/codex-refresh"
-import type { PluginInput } from "@kilocode/plugin"
 import { MessageV2 } from "../../src/session/message-v2"
 import { ProviderID } from "../../src/provider/schema"
+import { spawn } from "child_process"
+import fs from "fs/promises"
+import os from "os"
+import path from "path"
 
 type Auth = {
   type: "oauth"
@@ -12,6 +15,13 @@ type Auth = {
   accountId?: string
 }
 
+type Lock = {
+  staleMs: number
+  timeoutMs: number
+  baseDelayMs: number
+  maxDelayMs: number
+}
+
 const expired = (): Auth => ({
   type: "oauth",
   access: "old-access",
@@ -19,7 +29,10 @@ const expired = (): Auth => ({
   expires: 0,
 })
 
-function plugin(persist: (auth: Auth) => void): PluginInput {
+const root = path.join(import.meta.dir, "../..")
+const worker = path.join(import.meta.dir, "fixture/codex-auth-refresh-worker.ts")
+
+function plugin(persist: (auth: Auth) => void) {
   const set = async (req: { body: Auth }) => {
     persist(req.body)
   }
@@ -27,7 +40,101 @@ function plugin(persist: (auth: Auth) => void): PluginInput {
     client: {
       auth: { set },
     },
-  } as unknown as PluginInput
+  }
+}
+
+function sleep(ms: number) {
+  return new Promise<void>((resolve) => setTimeout(resolve, ms))
+}
+
+async function wait(file: string) {
+  const stop = Date.now() + 10_000
+  while (Date.now() < stop) {
+    if (
+      await fs
+        .stat(file)
+        .then(() => true)
+        .catch(() => false)
+    )
+      return
+    await sleep(10)
+  }
+  throw new Error(`Timed out waiting for file: ${file}`)
+}
+
+function run(input: { root: string; url: string; ready: string; start: string; lock?: Lock }) {
+  const proc = spawn(process.execPath, [worker, JSON.stringify(input)], {
+    cwd: root,
+    windowsHide: true,
+  })
+  const stdout: Buffer[] = []
+  const stderr: Buffer[] = []
+  proc.stdout?.on("data", (data) => stdout.push(Buffer.from(data)))
+  proc.stderr?.on("data", (data) => stderr.push(Buffer.from(data)))
+  return {
+    proc,
+    done: new Promise<{ code: number; stdout: string; stderr: string }>((resolve) => {
+      proc.on("close", (code) => {
+        resolve({
+          code: code ?? 1,
+          stdout: Buffer.concat(stdout).toString(),
+          stderr: Buffer.concat(stderr).toString(),
+        })
+      })
+    }),
+  }
+}
+
+async function race(input: { reuse: "early" | "late"; delay: number; lock?: Lock }) {
+  const dir = await fs.mkdtemp(path.join(os.tmpdir(), "codex-auth-refresh-"))
+  const calls: string[] = []
+  const used = new Set<string>()
+  const server = Bun.serve({
+    hostname: "127.0.0.1",
+    port: 0,
+    async fetch(req) {
+      const body = new URLSearchParams(await req.text())
+      const token = body.get("refresh_token")
+      if (!token) return new Response("missing refresh token", { status: 400 })
+      calls.push(token)
+      if (used.has(token)) {
+        if (input.reuse === "late") await sleep(input.delay + 50)
+        return new Response("refresh token reused", { status: 401 })
+      }
+      used.add(token)
+      await sleep(input.delay)
+      return Response.json({
+        id_token: "",
+        access_token: "next-access",
+        refresh_token: "next-refresh",
+        expires_in: 60,
+      })
+    },
+  })
+
+  try {
+    const data = path.join(dir, "share", "kilo")
+    const start = path.join(dir, "start")
+    const first = path.join(dir, "first")
+    const second = path.join(dir, "second")
+    await fs.mkdir(data, { recursive: true })
+    await fs.writeFile(path.join(data, "auth.json"), JSON.stringify({ openai: expired() }))
+    const url = `http://127.0.0.1:${server.port}/oauth/token`
+    const a = run({ root: dir, url, ready: first, start, lock: input.lock })
+    const b = run({ root: dir, url, ready: second, start, lock: input.lock })
+    try {
+      await Promise.all([wait(first), wait(second)])
+      await fs.writeFile(start, "")
+      const out = await Promise.all([a.done, b.done])
+      return { calls, out }
+    } finally {
+      if (a.proc.exitCode === null) a.proc.kill()
+      if (b.proc.exitCode === null) b.proc.kill()
+    }
+  } finally {
+    await server.stop(true)
+    await fs.rm(dir, { recursive: true, force: true })
+  }
 }
 
 describe("Codex auth refresh", () => {
@@ -121,4 +228,113 @@ describe("Codex auth refresh", () => {
       }),
     ).rejects.toBeInstanceOf(CodexAuthExpiredError)
   })
+
+  test("refreshes a newer stored token instead of the stale caller token", async () => {
+    const auth = expired()
+    const fresh = { ...expired(), refresh: "fresh-refresh", accountId: "account-1" }
+    const calls: string[] = []
+
+    const result = await refreshCodexAuth({
+      input: plugin(() => {}),
+      getAuth: async () => fresh,
+      auth,
+      refresh: async (token) => {
+        calls.push(token)
+        return { id_token: "", access_token: "next-access", refresh_token: "next-refresh", expires_in: 60 }
+      },
+      account: () => undefined,
+    })
+
+    expect(calls).toEqual(["fresh-refresh"])
+    expect(result.accountId).toBe("account-1")
+  })
+
+  test("releases the lock and pending entry after a transient failure", async () => {
+    const auth = expired()
+    const calls: string[] = []
+    const failed = await refreshCodexAuth({
+      input: plugin(() => {}),
+      getAuth: async () => auth,
+      auth,
+      refresh: async (token) => {
+        calls.push(token)
+        throw new Error("offline")
+      },
+      account: () => undefined,
+    }).catch((err) => err)
+
+    expect(failed).toEqual(new Error("offline"))
+
+    await refreshCodexAuth({
+      input: plugin(() => {}),
+      getAuth: async () => auth,
+      auth,
+      refresh: async (token) => {
+        calls.push(token)
+        return { id_token: "", access_token: "next-access", refresh_token: "next-refresh", expires_in: 60 }
+      },
+      account: () => undefined,
+    })
+
+    expect(calls).toEqual(["old-refresh", "old-refresh"])
+  })
+
+  test("aborts a stalled refresh and releases the lock", async () => {
+    const auth = expired()
+    const calls: string[] = []
+    const failed = await refreshCodexAuth({
+      input: plugin(() => {}),
+      getAuth: async () => auth,
+      auth,
+      refresh: async (token, signal) => {
+        calls.push(token)
+        return new Promise<never>((_, reject) => {
+          signal.addEventListener("abort", () => reject(signal.reason), { once: true })
+        })
+      },
+      account: () => undefined,
+      timeout: 20,
+    }).catch((err) => err)
+
+    expect(failed).toBeInstanceOf(DOMException)
+    expect(failed.name).toBe("TimeoutError")
+
+    await refreshCodexAuth({
+      input: plugin(() => {}),
+      getAuth: async () => auth,
+      auth,
+      refresh: async (token) => {
+        calls.push(token)
+        return { id_token: "", access_token: "next-access", refresh_token: "next-refresh", expires_in: 60 }
+      },
+      account: () => undefined,
+    })
+
+    expect(calls).toEqual(["old-refresh", "old-refresh"])
+  })
+
+  test("serializes refreshes across processes before token reuse", async () => {
+    for (const reuse of ["early", "late"] as const) {
+      for (let trial = 0; trial < 5; trial++) {
+        const result = await race({ reuse, delay: 100 })
+        expect(result.calls).toEqual(["old-refresh"])
+        expect(result.out.map((x) => x.code)).toEqual([0, 0])
+        expect(result.out.map((x) => x.stderr)).toEqual(["", ""])
+      }
+    }
+  }, 30_000)
+
+  test("keeps the process lock alive during a delayed token response", async () => {
+    const lock = {
+      staleMs: 300,
+      timeoutMs: 10_000,
+      baseDelayMs: 20,
+      maxDelayMs: 30,
+    }
+    const result = await race({ reuse: "early", delay: 1_000, lock })
+
+    expect(result.calls).toEqual(["old-refresh"])
+    expect(result.out.map((x) => x.code)).toEqual([0, 0])
+    expect(result.out.map((x) => x.stderr)).toEqual(["", ""])
+  }, 15_000)
 })
diff --git a/packages/opencode/test/kilocode/codex-refresh-user-agent.test.ts b/packages/opencode/test/kilocode/codex-refresh-user-agent.test.ts
new file mode 100644
index 00000000000..2e4ad682286
--- /dev/null
+++ b/packages/opencode/test/kilocode/codex-refresh-user-agent.test.ts
@@ -0,0 +1,55 @@
+import { expect, test } from "bun:test"
+import type { PluginInput } from "@kilocode/plugin"
+import { CodexAuthPlugin } from "../../src/plugin/codex"
+
+test("identifies Codex refresh requests as Kilo", async () => {
+  const original = globalThis.fetch
+  const seen: Request[] = []
+  const signals: (AbortSignal | null | undefined)[] = []
+  let auth = {
+    type: "oauth" as const,
+    access: "old-access",
+    refresh: "old-refresh",
+    expires: 0,
+  }
+  const input = {
+    client: {
+      auth: {
+        set: async (req: { body: typeof auth }) => {
+          auth = req.body
+        },
+      },
+    },
+  } as unknown as PluginInput
+  globalThis.fetch = Object.assign(
+    async (...args: Parameters<typeof globalThis.fetch>) => {
+      const req = new Request(...args)
+      seen.push(req)
+      signals.push(args[1]?.signal)
+      if (req.url === "https://auth.openai.com/oauth/token") {
+        return Response.json({
+          id_token: "",
+          access_token: "next-access",
+          refresh_token: "next-refresh",
+          expires_in: 60,
+        })
+      }
+      return new Response("", { status: 200 })
+    },
+    { preconnect: original.preconnect },
+  )
+
+  try {
+    const plugin = await CodexAuthPlugin(input)
+    const loaded = await plugin.auth!.loader!(async () => auth, {} as never)
+    await loaded.fetch("https://api.openai.com/v1/responses")
+  } finally {
+    globalThis.fetch = original
+  }
+
+  const refresh = seen[0]
+  expect(refresh.url).toBe("https://auth.openai.com/oauth/token")
+  expect(refresh.headers.get("user-agent")).toMatch(/^kilo\//)
+  expect(signals[0]).toBeInstanceOf(AbortSignal)
+  expect(await refresh.text()).toContain("refresh_token=old-refresh")
+})
diff --git a/packages/opencode/test/kilocode/fixture/codex-auth-refresh-worker.ts b/packages/opencode/test/kilocode/fixture/codex-auth-refresh-worker.ts
new file mode 100644
index 00000000000..845b25fde88
--- /dev/null
+++ b/packages/opencode/test/kilocode/fixture/codex-auth-refresh-worker.ts
@@ -0,0 +1,113 @@
+import fs from "fs/promises"
+import path from "path"
+import z from "zod"
+
+const Auth = z.object({
+  type: z.literal("oauth"),
+  refresh: z.string(),
+  access: z.string(),
+  expires: z.number(),
+  accountId: z.string().optional(),
+})
+type Auth = z.infer<typeof Auth>
+
+const Tokens = z.object({
+  id_token: z.string(),
+  access_token: z.string(),
+  refresh_token: z.string(),
+  expires_in: z.number().optional(),
+})
+
+const Msg = z.object({
+  root: z.string(),
+  url: z.string(),
+  ready: z.string(),
+  start: z.string(),
+  lock: z
+    .object({
+      staleMs: z.number(),
+      timeoutMs: z.number(),
+      baseDelayMs: z.number(),
+      maxDelayMs: z.number(),
+    })
+    .optional(),
+})
+
+function input() {
+  const raw = process.argv[2]
+  if (!raw) throw new Error("Missing Codex auth refresh worker input")
+  return Msg.parse(JSON.parse(raw))
+}
+
+function sleep(ms: number) {
+  return new Promise<void>((resolve) => setTimeout(resolve, ms))
+}
+
+async function wait(file: string) {
+  const stop = Date.now() + 10_000
+  while (Date.now() < stop) {
+    if (
+      await fs
+        .stat(file)
+        .then(() => true)
+        .catch(() => false)
+    )
+      return
+    await sleep(10)
+  }
+  throw new Error(`Timed out waiting for file: ${file}`)
+}
+
+async function main() {
+  const msg = input()
+  process.env.XDG_DATA_HOME = path.join(msg.root, "share")
+  process.env.XDG_CACHE_HOME = path.join(msg.root, "cache")
+  process.env.XDG_CONFIG_HOME = path.join(msg.root, "config")
+  process.env.XDG_STATE_HOME = path.join(msg.root, "state")
+  process.env.KILO_TEST_HOME = path.join(msg.root, "home")
+
+  const { Path } = await import("@opencode-ai/core/global")
+  const { refreshCodexAuth } = await import("../../../src/kilocode/provider/codex-refresh")
+  const file = path.join(Path.data, "auth.json")
+  const read = async () => {
+    const data = z.object({ openai: Auth }).parse(JSON.parse(await fs.readFile(file, "utf8")))
+    return data.openai
+  }
+  const plugin = {
+    client: {
+      auth: {
+        set: async (req: { body: Auth }) => {
+          await fs.writeFile(file, JSON.stringify({ openai: req.body }))
+        },
+      },
+    },
+  }
+
+  await fs.writeFile(msg.ready, String(process.pid))
+  await wait(msg.start)
+  const auth = await read()
+  const next = await refreshCodexAuth({
+    input: plugin,
+    getAuth: read,
+    auth,
+    refresh: async (token) => {
+      const response = await fetch(msg.url, {
+        method: "POST",
+        headers: { "Content-Type": "application/x-www-form-urlencoded" },
+        body: new URLSearchParams({ refresh_token: token }).toString(),
+      })
+      if (!response.ok) throw new Error(`Token refresh failed: ${response.status}`)
+      return Tokens.parse(await response.json())
+    },
+    account: () => undefined,
+    lock: msg.lock,
+  })
+
+  process.stdout.write(JSON.stringify(next))
+}
+
+await main().catch((err) => {
+  const text = err instanceof Error ? (err.stack ?? err.message) : String(err)
+  process.stderr.write(text)
+  process.exit(1)
+})
diff --git a/packages/opencode/test/kilocode/oauth-branding.test.ts b/packages/opencode/test/kilocode/oauth-branding.test.ts
index 1a8556a5b5c..71cc234b3db 100644
--- a/packages/opencode/test/kilocode/oauth-branding.test.ts
+++ b/packages/opencode/test/kilocode/oauth-branding.test.ts
@@ -8,6 +8,7 @@ describe("Kilo OAuth branding", () => {
     const src = await Bun.file(path.join(root, "src", "plugin", "codex.ts")).text()
 
     expect(src).toContain('originator: "kilo"')
+    expect(src).toContain('"User-Agent": `kilo/${InstallationVersion}`')
     expect(src).toContain("return to Kilo")
     expect(src).not.toContain('originator: "opencode"')
     expect(src).not.toContain("return to OpenCode")