fix(server): read Codex history in pages instead of one whole-thread reply

Opening a Codex agent whose timeline the daemon doesn't hold asked Codex
for the whole thread in one thread/read reply. Past the 128 MiB provider
line cap that reply killed the session; before the cap it crashed the
daemon. Codex 0.145 and newer reject that read on paginated threads, so
importing them failed.

Paginated threads now load through thread/items/list pages. A legacy
thread keeps its single read. A reply over the line cap fails only its own
request: for a legacy read, a warning row names the archive,
`codex migrate-rollouts`, unarchive steps; for a page, a warning row ends
the history there. Items are capped as they are projected, and rewind's
fork no longer returns the thread's turns.

Co-authored-by: hunterricks <hr@savagestrategic.io>
Co-authored-by: dundunHa <lixinpengde@gmail.com>

packages/server/scripts/reproduce-codex-history-string-limit.mts

@@ -0,0 +1,108 @@
+// Opt-in diagnostic for #3905. Run from the repository root:
+// node --import tsx packages/server/scripts/reproduce-codex-history-string-limit.mts 520 [legacy|paginated]
+// Requires Codex 0.148+ on PATH and approximately 2 GiB of available memory.
+// `paginated` migrates the synthetic rollout with `codex migrate-rollouts` first.
+import { execFileSync, spawn } from "node:child_process";
+import { randomUUID } from "node:crypto";
+import { mkdtemp, mkdir, open, rm } from "node:fs/promises";
+import path from "node:path";
+import pino from "pino";
+import { CodexAppServerAgentSession } from "../src/server/agent/providers/codex-app-server-agent.js";
+
+const megabytes = Number(process.argv[2] ?? "520");
+if (!Number.isSafeInteger(megabytes) || megabytes < 1 || megabytes > 600) {
+  throw new Error("Expected an integer size between 1 and 600 MiB");
+}
+const historyMode = process.argv[3] ?? "legacy";
+if (historyMode !== "legacy" && historyMode !== "paginated") {
+  throw new Error("Expected history mode legacy or paginated");
+}
+const root = await mkdtemp(path.join(process.cwd(), ".codex-history-repro-"));
+const home = path.join(root, "codex-home");
+const now = new Date();
+const timestamp = now.toISOString();
+const threadId = randomUUID();
+const turnId = randomUUID();
+const sessions = path.join(home, "sessions", ...timestamp.slice(0, 10).split("-"));
+await mkdir(sessions, { recursive: true });
+const rollout = await open(
+  path.join(sessions, `rollout-${timestamp.slice(0, 19).replaceAll(":", "-")}-${threadId}.jsonl`),
+  "w",
+);
+async function write(type: string, payload: unknown) {
+  await rollout.write(`${JSON.stringify({ timestamp, type, payload })}\n`);
+}
+await write("session_meta", {
+  id: threadId,
+  timestamp,
+  cwd: root,
+  originator: "codex_cli_rs",
+  cli_version: "0.159.0",
+  source: "cli",
+  model_provider: "openai",
+  history_mode: "legacy",
+});
+await write("event_msg", { type: "task_started", turn_id: turnId, model_context_window: 200000 });
+await write("event_msg", {
+  type: "user_message",
+  message: "Synthetic oversized history",
+  images: [],
+  local_images: [],
+  text_elements: [],
+});
+for (let index = 0; index < megabytes; index++) {
+  await write("event_msg", {
+    type: "agent_message",
+    message: "x".repeat(1024 * 1024),
+    phase: "commentary",
+  });
+}
+await write("event_msg", { type: "task_complete", turn_id: turnId, last_agent_message: "done" });
+await rollout.close();
+if (historyMode === "paginated") {
+  execFileSync("codex", ["migrate-rollouts", "--apply", "--thread", threadId], {
+    env: { ...process.env, CODEX_HOME: home },
+    stdio: "ignore",
+  });
+}
+console.log(
+  `Opening synthetic ${megabytes} MiB ${historyMode} history through the real Codex app-server`,
+);
+const session = new CodexAppServerAgentSession(
+  { provider: "codex", cwd: root },
+  { sessionId: threadId },
+  pino({ level: "silent" }),
+  async () =>
+    spawn(
+      "codex",
+      ["app-server", "--disable", "plugins", "--disable", "apps", "--disable", "remote_plugin"],
+      {
+        stdio: ["pipe", "pipe", "pipe"],
+        env: { ...process.env, CODEX_HOME: home },
+      },
+    ),
+  { codexHome: home },
+  false,
+  false,
+  false,
+  undefined,
+  "history",
+);
+try {
+  await session.connect();
+  let count = 0;
+  for await (const event of session.streamHistory()) {
+    if (event.type !== "timeline") continue;
+    count++;
+    if (event.item.type === "notification") console.log(event.item.message);
+  }
+  console.log(`History loaded: ${count} timeline rows`);
+} catch (error) {
+  // A recoverable session error is acceptable for the crash-isolation assertion.
+  console.log(
+    `History rejected without crashing: ${error instanceof Error ? error.message : String(error)}`,
+  );
+} finally {
+  await session.close();
+  await rm(root, { recursive: true, force: true, maxRetries: 10, retryDelay: 100 });
+}