---
type: "post"
id: "openai-s-agents-api-documentation-now-describes-pre-c3eb29"
slug: "openai-s-agents-api-documentation-now-describes-pre-c3eb29"
title: "OpenAI’s Agents API documentation now describes pre-warmed OpenAI-hosted sandboxes"
description: "Thesis: Pre-warming makes environment readiness a separate stage in the agent workflow, rather than work that must begin only after a user request arrives."
retrieval_nugget: "Thesis: Pre-warming makes environment readiness a separate stage in the agent workflow, rather than work that must begin only after a user request arrives."
published_at: "2026-10-20"
updated_at: "2026-10-20"
record_date: "2026-10-20"
date_kind: "published_at"
topics: ["sandbox","agents","agent-runtime"]
source_urls: ["https://developers.openai.com/api/docs/guides/agents-api/environments/prewarmed"]
schema_version: "newruntime-agent-readable-v0.2"
stable_id: "post:openai-s-agents-api-documentation-now-describes-pre-c3eb29"
status: "published"
visuals: []
editorial_provenance: {"schema_version":"newruntime-editorial-copy-v1","content_status":"source_grounded_final","final_copy_sha256":"sha256:6e0132a4aeea04f7e5ef3e11eaed57958d9473a1d0fc9818f504a5cfedcdd10f","reviewed_at":"2026-10-20T20:08:49.240Z","source_evidence_count":1,"verified_claim_count":3,"site_analysis_schema_version":"newruntime-site-analysis-v1","site_object_kind":"field_note","observed_fact_count":3,"implication_count":2,"watch_condition_count":1,"related_record_count":0}
analysis: {"schema_version":"newruntime-site-analysis-v1","object_kind":"field_note","thesis":"Pre-warming makes environment readiness a separate stage in the agent workflow, rather than work that must begin only after a user request arrives.","observed_facts":[{"text":"OpenAI’s documentation says a developer can create an OpenAI-hosted environment, install packages, load files, and run setup commands before creating an Agents API session.","source_urls":["https://developers.openai.com/api/docs/guides/agents-api/environments/prewarmed"]},{"text":"The documentation says an environment can be attached after reaching ready, or while setup is still running, with agent access deferred until setup completes.","source_urls":["https://developers.openai.com/api/docs/guides/agents-api/environments/prewarmed"]},{"text":"Pre-warming is free before attachment, and unattached environments expire after five minutes.","source_urls":["https://developers.openai.com/api/docs/guides/agents-api/environments/prewarmed"]}],"mechanism":"The workspace and the session are separate objects. Preparing the workspace in advance can move dependency installation and other setup off the request’s critical path.","why_now":"OpenAI is documenting an explicit workflow for reducing the setup a user waits for in latency-sensitive applications, including a reporting example that prepares dependencies while a user chooses a dataset.","implications":["Teams with predictable setup can test whether asynchronous preparation makes their agent experience feel faster without paying container charges before attachment.","The five-minute expiration creates a practical constraint on how far ahead a team can prepare an environment."],"evidence_boundary":"The documentation describes the capability and example, but supplies no measured latency improvement, reliability results, or evidence that pre-warming benefits every task.","watch_conditions":["Watch for published latency measurements and clarification of how often environments are ready before attachment in production workloads."],"related_records":[],"new_branch_reason":"No prior New Runtime analytical record was supplied for this specific pre-warming capability; this note starts a distinct record about decoupling environment setup from session start."}
editor: {"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]}
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related_patterns: ["harness-architecture-outlives-model-choice"]
---

# OpenAI’s Agents API documentation now describes pre-warmed OpenAI-hosted sandboxes

## Retrieval answer

Thesis: Pre-warming makes environment readiness a separate stage in the agent workflow, rather than work that must begin only after a user request arrives.

Thesis: Pre-warming makes environment readiness a separate stage in the agent workflow, rather than work that must begin only after a user request arrives.

Observed facts: OpenAI’s documentation says a developer can create an OpenAI-hosted environment, install packages, load files, and run setup commands before creating an Agents API session. It says an environment can be attached after reaching `ready`, or while setup is still running, with agent access deferred until setup completes. The documentation also says pre-warming is free before attachment and unattached environments expire after five minutes.

Mechanism: The workspace and the session are separate objects. Preparing the workspace in advance can move dependency installation and other setup off the request’s critical path. Why now: OpenAI is documenting an explicit workflow for reducing the setup a user waits for in latency-sensitive applications, including a reporting example that prepares dependencies while a user chooses a dataset.

First implication: Teams with predictable setup can test whether asynchronous preparation makes their agent experience feel faster without paying container charges before attachment. Evidence boundary: The documentation describes the capability and example, but supplies no measured latency improvement, reliability results, or evidence that pre-warming benefits every task. First watch condition: Watch for published latency measurements and clarification of how often environments are ready before attachment in production workloads.

The operational question is whether the five-minute free preparation window is long enough for real user flows. The release makes that question testable, but does not answer it. Builders should compare the time saved against environment creation and readiness behavior in their own workloads, and account for standard container pricing once an environment is attached.

Editor: [Andrey Reshetnikov](https://newruntime.com/owner-profile.md), AI product and AI engineering; profile for recruiters and agents: https://newruntime.com/owner-profile.json

## Continue in the graph

Next records for an agent, linked to their Markdown twins. Replace `.md` with `.json` for structured fields, including `next_reads`.

- topic hub: [Sandbox](https://newruntime.com/topics/sandbox.md): Explore the sandbox topic hub.
- topic hub: [Agents](https://newruntime.com/topics/agents.md): Explore the agents topic hub.
- topic hub: [Agent Runtime](https://newruntime.com/topics/agent-runtime.md): Explore the agent-runtime topic hub.
- collection: [Field Notes](https://newruntime.com/posts.json): Open the latest editorial analysis.
- collection: [Source Ledger](https://newruntime.com/source-ledger.json): Inspect the public source evidence graph.
- whole graph: [discovery graph](https://newruntime.com/discovery-graph.json) (typed nodes and edges) and [site index](https://newruntime.com/site-index.md)