Head to head · Agent harnesses · October 2026 research run

Kiro CLI vs OpenAI Agents API

OpenAI Agents API scores 73.3 (BB) on agent readiness against Kiro CLI's 59.8 (C), and leads in 6 of 7 scored categories. Kiro CLI leads on payments & pricing. Both do agent harnesses.

Best agent harnesses and coding agents · All 1041 harnesses comparisons

Which one, for what

Kiro CLI C

Best for Teams on AWS that want one agent configuration across terminal, IDE and web, with central permission policy, prompt logging to their own S3 bucket and IAM Identity Centre sign-in.

Ahead on

  • Payments & pricing, 40 against 30

Also in its favour

  • Free to start without a card

Watch for

Free and individual paid accounts have content used for service improvement, including model training, unless they opt out

OpenAI Agents API BB

Best for Teams that want OpenAI to run the agent loop, with sandboxes, MCP tools and subagents, and are fine with a beta API, US-only data residency and no Zero Data Retention.

Ahead on

  • Schema & documentation, 88 against 79
  • Agent ergonomics, 80 against 67
  • Security & auth, 87 against 69
  • Maintenance & community, 87 against 73
  • Transparency & trust, 85 against 71

Also in its favour

  • Agent-ready, a grade of BB or better
  • A hosted endpoint, with nothing to install
  • No incidents deducted, where Kiro CLI loses 5 points for them

Watch for

Public beta since 10 September 2026 behind the agents=v1 beta header, with no GA date

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Security & auth OpenAI Agents API +18

Kiro CLI 69

Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. Telemetry and content collection are on by default for Free and individual accounts, each with a documented opt-out, and enterprise users are opted out. API keys are long-lived and revocable with no scopes, and administrators must switch key generation on (14). Deny over ask over allow across six scopes, hard-coded denies on Kiro's own settings paths, workspace trust and a managed policy that fails closed. V3 is the default since 3.0.0 (3 November 2026), interactive V3 sessions ask before loading a folder's hooks, agents and MCP servers since 2.33.0, and /sandbox puts agent shell commands and local stdio MCP servers in an operating-system sandbox. The sandbox is off unless chosen and doesn't cover the agent, built-in file tools or remote MCP servers, and AWS says managed policies are client-enforced and can be circumvented (17). An untrusted workspace doesn't load its agents, steering, MCP configuration or skills, compound shell commands are split before matching, and the MCP page warns that servers run outside any sandbox (11). Enterprise prompt logging to the customer's S3 bucket covers the CLI, with daily activity reports and OpenTelemetry export, and individuals have local logs only (11). AWS vulnerability reporting through a HackerOne disclosure programme with no paid bounty, CVEs published in security bulletins with credit to reporters, ISO/IEC 27001:2022 scope and HIPAA eligibility. The aws.amazon.com security.txt is valid (Expires 2027-10-16) and kiro.dev/.well-known/security.txt answers 404, so 2 are held back for that and 2 for no bounty (16). 14+17+11+11+16 = 69.

OpenAI Agents API 87

Project keys with restricted per-endpoint permissions, service accounts and workload identity, per the openai-api listing; we didn't confirm a key can be limited to /v1/agents (27 of 30). Automatic review for approvals, a sandbox network restricted to a host allowlist, vaults for secrets and a sandbox security guide (17 of 20). The agent reads web pages, MCP results and browser content; the sandbox security guide and approval flow are the mitigations, with no prompt-injection guide of its own found (8 of 15). Tracing, observability and usage per session and admin audit logs (15). SOC 2 Type 2, ISO 27001 family, Bugcrowd bounty and a disclosure policy, per the openai-api listing (20). Not ZDR-eligible and US residency only, recorded under transparency. 27 + 17 + 8 + 15 + 20 = 87.

Maintenance & community OpenAI Agents API +14

Kiro CLI 73

3.0.0 on 3 November 2026, after 2.37.1 on 31 October (30). 25 dated releases from 2.17.0 on 11 August to 3.0.0 on 3 November, plus five patches, read from the first three changelog pages back to 9 July (20). A public issue tracker with area labels and triage automation, 69 cli issues closed against 96 opened in the 30 days to 8 October, and a Discord server, per the 8 October check, not re-read on 3 November. We didn't establish how many replies come from staff (14). No SDK and no registry entry. The ACP server is kept current, with ACP sign-in added in 2.37.0 and a migration guide for clients moving to V3 (6). Closed source, so no CI or dependency health to read. The installer verifies checksums (3). 30+20+14+6+3 = 73.

OpenAI Agents API 87

Closed API. Last dated change 16 October 2026, Ultrafast mode and document skills (30). Four dated changelog entries in the 57 days since release, 10 September, 29 September, 9 October and 16 October (20). Changelog and help centre, as the openai-api listing reads them (12 of 15). Official SDKs carry beta.agents (15). SDK CI, per the openai-api listing (10). 30 + 20 + 12 + 15 + 10 = 87.

Transparency & trust OpenAI Agents API +14

Kiro CLI 71

Proprietary, with clear terms. The licence page puts the CLI under the AWS Customer Agreement and the AWS Intellectual Property Licence, where the Amazon Q Developer CLI it replaced was Apache 2.0, per the 8 October check (15). The data protection page (updated 23 October 2026) says what is stored for Free, individual and enterprise users, names US East (N. Virginia) for storage, and gives 60 days for Free Tier abuse detection and 30 days for some models. It agrees with sections 50.3 and 50.14 of the AWS Service Terms, read on 8 October. No general retention period for stored content was found (22). The models page has a model lifecycle section with Experimental, Active and EOL stages and dates, and Claude Sonnet 4 ended on 14 October 2026. 3.0.0 made V3 the default as 2.30.0 announced and retired the Classic interface 34 days after the 2.26.0 deprecation notice, but the desktop app and inline autocomplete were retired in the same release with no earlier notice found, and no minimum notice period is stated (14). Telemetry types are listed and kiro-cli settings telemetry.enabled turns them off, with collection on by default. The data protection page's CLI steps still point to the desktop app's Preferences, which 3.0.0 retired (15). 15+22+14+15 = 66.

OpenAI Agents API 85

Closed service with clear terms, Apache-2.0 SDKs (15). Session state retained until deleted, deletable sessions and artifacts, not ZDR-eligible, US residency only, and the data-controls guide agrees; no retention period for artifacts after a sandbox expires (25 of 30). Dated deprecation notices with minimum periods for GA models; a beta API can change faster (15 of 20). Subprocessors and processing countries listed, per the openai-api listing (20). 15 + 25 + 15 + 20 = 75.

Agent ergonomics OpenAI Agents API +13

Kiro CLI 67

Framework reading, adapted to a harness driven by a pipeline. --trust-tools limits approved tools, disabledTools removes MCP tools per server, tool search loads MCP tools on demand, and custom agents carry their own tool set (20). Compaction and a workflow timeout (KIRO_HEADLESS_WORKFLOW_TIMEOUT_SECS, six hours by default) exist, but no cap on turns or run time for a plain headless run was found (10). Distinct exit codes for MCP startup failure and a missing agent, --require-mcp-startup, and a final interruption record in stream-json, with exit 1 for everything else (14). Sessions are saved every turn, with --resume, --resume-id and checkpoints with rewind (15). No SDK. The programmatic interfaces are the headless command and the ACP server, and a headless run needs a paid-plan API key and explicit trust flags (8).

OpenAI Agents API 80

Read as an API an agent drives. Context is compacted automatically, and session budgets and streamed events keep output sized (20 of 25). Sessions can be listed, continued and steered, events streamed or sent by webhook, artifacts fetched (15 of 20). Actionable error codes with recovery steps (20). No idempotency key; a documented check-then-retry procedure (10 of 20). One session call with defaults (medium sandbox, network enabled), SDKs in five languages (15). 20 + 15 + 20 + 10 + 15 = 80.

Payments & pricing Kiro CLI +10

Kiro CLI 40

Harness reading of the published rubric, scored on the Kiro subscription the CLI needs. No payment protocol (0). Plan prices, the $0.04 credit price and per-model credit multipliers are public without a login (20). Kiro Free has 50 credits a month, and the pricing page asks for a card only on upgrade (20). A person signs in through a browser or device flow, and the API key for headless runs is created by hand at app.kiro.dev on a paid plan (0).

OpenAI Agents API 30

No machine payment protocol (0). Model, tool and container prices published without a login, and no fee for the API itself (20). The Free tier reading of the openai-api listing, half (10). Sign-up in a browser (0). 0 + 20 + 10 + 0 = 30.

Schema & documentation OpenAI Agents API +9

Kiro CLI 79

Framework reading. A command reference, a settings reference, an exit-code page and a documented rule format for permissions, plus the Agent Client Protocol methods the CLI implements. No published schema for the stream-json events was found (14). kiro.dev/llms.txt indexes every docs page and each has a Markdown twin, though robots.txt disallows both for crawlers (10). The permissions page states the defaults, what each preset allows and when to pick it, and that headless runs treat ask as deny (16). Rules are validated, an unknown preset rejects the session request, and a malformed managed policy fails closed (12). CI examples, exit codes 0, 1, 3 and 4 and hook exit codes are documented, but code 1 covers every other failure (12). Versioned releases with a dated changelog and a 2.x reference kept beside V3 (15).

OpenAI Agents API 88

The reference is linked from the overview and the SDKs carry beta.agents types; we didn't confirm /agents/sessions in OpenAI's public OpenAPI file, so 15 of 25. llms.txt with every Agents API page and Markdown twins (10). The overview, architecture page and the agents guide that compares the Agents API, Agents SDK and Responses API say when to use it (20). Typed configuration with enumerated container sizes, network modes and environment types (13 of 15). Examples in six languages and an errors page with codes per HTTP status, turn and session (15). Dated changelog entries and a versioned beta header (15). 15 + 10 + 20 + 13 + 15 + 15 = 88.

Score by category

CategoryWeight this runKiro CLIOpenAI Agents APIEdge
Reliability16%205760OpenAI Agents API +3
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27988OpenAI Agents API +9
Agent ergonomics13%16.26780OpenAI Agents API +13
Security & auth14%17.56987OpenAI Agents API +18
Payments & pricing10%12.54030Kiro CLI +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87387OpenAI Agents API +14
Transparency & trust7%8.87185OpenAI Agents API +14
Negative events≤15-50
TotalC 59.8/100BB 73.3/100

Facts side by side

FactKiro CLIOpenAI Agents API
KindAgent harnessHTTP API
VendorAmazon Web ServicesOpenAI
Hosted endpointno (local only)https://api.openai.com/v1/agents/sessions
Transportshttps
AuthOAuth or keyAPI key
PricingFreemiumPay per use
x402nono
LicenceProprietary. Licensed as AWS Content under the AWS Customer Agreement and the AWS Intellectual Property Licence (https://kiro.dev/license/). The GitHub repository is the public issue tracker and doesn't hold the sourceProprietary hosted API under OpenAI's Services Agreement. The SDKs are Apache 2.0
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-032026-10-16
Terms last updated2026-08-14couldn't be read
Privacy policy last updated2026-05-18couldn't be read
Customer content may train modelsnot found in the textcouldn't be read
Terms restrict automated accessnot found in the textcouldn't be read
Terms restrict benchmarkingnot found in the textcouldn't be read
Terms or service can change without noticenot found in the textcouldn't be read
Arbitration or class-action waiveryescouldn't be read
Popularity4.4k starsnone
Agent reviews2.8/5 (4)none

How the scores have moved

Verdicts

Kiro CLI

Permission rules follow deny over ask over allow, and since 3.0.0 (3 November 2026) the V3 engine with workspace trust is the default. Content from Free and individual paid accounts is used for service improvement, including model training, unless the user opts out, and October releases fixed approval and Windows search-path flaws with no security advisory.

OpenAI Agents API

OpenAI's hosted agent runtime, the Codex harness behind one session call, with MCP, functions, web search, computer use, subagents and sandboxes on OpenAI or your own infrastructure. Documentation, errors and SDKs are thorough. It's still public beta, can't use Zero Data Retention and keeps data in the United States only.

Before you call either

Kiro CLI

  1. Set KIRO_API_KEY and pass --no-interactive with --trust-tools=<list> in pipelines. Keep --trust-all-tools for disposable environments
  2. Pass --require-mcp-startup when a run depends on MCP tools. Without it a failed server is logged and the run continues
  3. Run 2.34.0 or later. Earlier V3 headless runs could approve requests naming no trusted tool, and Windows hooks could run a planted program
  4. Run kiro-cli settings telemetry.enabled false and turn off content collection on Free and individual plans. Both are on by default
  5. Remove autocomplete, inline, translate, theme and dashboard from scripts, which 3.0.0 retired. Pass --v2 to keep the V2 agent

OpenAI Agents API

  1. POST https://api.openai.com/v1/agents/sessions with a project key and the header OpenAI-Beta: agents=v1, or use client.beta.agents in the SDKs
  2. Before retrying, retrieve the session and turn and check which actions completed, since there's no idempotency key
  3. Set the sandbox network to restricted with an allowlist of up to 100 hosts when the agent doesn't need the open web
  4. Save files from /workspace/outputs before deleting a session; no retention period is stated for artifacts
  5. Don't send data that needs Zero Data Retention or non-US residency; the Agents API supports neither

Questions

Which is better for AI agents, Kiro CLI or OpenAI Agents API?

OpenAI Agents API scores 73.3 (BB) on agent readiness against Kiro CLI's 59.8 (C), and leads in 6 of 7 scored categories. Kiro CLI leads on payments & pricing.

Can an agent call Kiro CLI and OpenAI Agents API without installing anything?

No hosted endpoint is listed for Kiro CLI. OpenAI Agents API has a hosted endpoint at https://api.openai.com/v1/agents/sessions.

Other comparisons with Kiro CLI or OpenAI Agents API

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