Head to head · Agent harnesses · October 2026 research run

Gemini CLI vs OpenAI Agents API

OpenAI Agents API scores 73.3 (BB) on agent readiness against Gemini CLI's 64.8 (B), and leads in 3 of 7 scored categories. Gemini CLI leads on reliability, schema & documentation and transparency & trust. Both do agent harnesses.

Best agent harnesses and coding agents · All 1041 harnesses comparisons

Which one, for what

Gemini CLI B

Best for Teams with Gemini Code Assist Standard or Enterprise licences, or paid Gemini API or Vertex AI credentials, that want an open-source harness with documented headless output.

Ahead on

  • Reliability, 71 against 60
  • Schema & documentation, 93 against 88
  • Transparency & trust, 90 against 85

Also in its favour

  • Open source

Watch for

Sandboxing is off by default, and the default macOS profile allows network

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

  • Security & auth, 87 against 67
  • Payments & pricing, 30 against 20

Also in its favour

  • Agent-ready, a grade of BB or better
  • A hosted endpoint, with nothing to install
  • No incidents deducted, where Gemini CLI loses 7 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 +20

Gemini CLI 67

Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. Usage statistics on by default (privacy.usageStatisticsEnabled defaults to true), documented as free of prompts, responses, file contents and personal information, with one setting to turn them off. Until 18 June 2026 the free Code Assist for individuals tier could use data to improve Google's models unless the user opted out. Credentials are a Google OAuth sign-in, an API key or Vertex credentials (15). Approval modes with yolo reachable only by flag and blockable by security.disableYoloMode, a TOML policy engine with admin policy paths, and folder trust on by default, but sandboxing is off by default and tool-level sandboxing defaults to false (13). Environment-variable redaction, and 0.61.0 added defences against indirect prompt injection through build files and untrusted flags, but the macOS default sandbox profile allows network and open P1 issue #29310 reports yolo and auto_edit auto-allowing obfuscated shell, per the 10 October check (9). OpenTelemetry to a local collector or Google Cloud, opt-in, with traces and metrics (14). SECURITY.md routes reports to g.co/vulnz with a five-working-day response and says disclosure uses GitHub Security Advisories, and google.com has a valid security.txt to 2030. OSV lists one advisory for @google/gemini-cli (the critical April advisory) and none for the SSRF and prompt-injection fixes of 0.59.0 and 0.61.0 (16). SOC 2 isn't scored on the framework reading. 15 + 13 + 9 + 14 + 16 = 67.

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.

Reliability Gemini CLI +11

Gemini CLI 71

Local-package reading. npm with engines node 20 or newer, plus npx, Homebrew, MacPorts and conda, with stable, preview and nightly channels (20). Public CI with ci.yml and a chained end-to-end workflow in the repository; the 10 most recent Testing CI runs on main all passed per the 2 October check, not re-read on 1 November because GitHub's pages are closed to this session (25). 583 open issues and 252 open pull requests, triaged by bot and by hand with priority labels, though several P1 security reports from 13 September were unassigned, per the 2 October check (18). releases.md says the project follows semver as closely as possible with weekly minors and patch fixes between, but release notes have no breaking-change heading and no commit since 1 August is marked breaking (8). 0.66.0, pre-1.0 (0). 20 + 25 + 18 + 8 + 0 = 71.

OpenAI Agents API 60

Read as a hosted API. status.openai.com has an Agents component under APIs (20). Since release on 10 September (57 days, not 90), the feed names the Agents API in a degraded-performance incident on 14 September, the elevated errors across ChatGPT, Codex and the API on 29 September (the openai-api listing reads that one as a major, 17:52 to 23:14 UTC), computer use issues and degraded workspace agents on 6 and 7 October, degraded performance across the APIs for 22 minutes on 21 October, and overbilling for hosted containers on 19 September. One major, the rest minor (10). Rate limits come from the shared guide, published per tier and model with headers, and the errors page adds a Files API allowance on session creation (15). 429 and 503 guidance with Retry-After, capped backoff and a check-then-retry procedure for turns (15). The Scale Tier SLA in the openai-api listing isn't shown to cover a beta API (0). Public beta behind the agents=v1 header (0). 20 + 10 + 15 + 15 + 0 + 0 = 60.

Payments & pricing OpenAI Agents API +10

Gemini CLI 20

Harness reading of the published rubric. No payment protocol (0). Token prices and plan prices are public without a login (20). The 1,000 requests a day Google sign-in tier ended on 18 June 2026. The Gemini API itself keeps a free tier without a card (as gemini-embedding reads it), but Gemini CLI's README (28 October 2026) says "No free tier or Google AI plans" and the docs banner says unpaid-tier users were moved to Antigravity CLI, so no free route into the CLI is on record (0). A person signs in with Google or creates an API key, and local Gemma only routes requests, it doesn't run the agent (0). 0 + 20 + 0 + 0 = 20.

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 Gemini CLI +5

Gemini CLI 93

Framework reading. settings.schema.json in the repository, and a generated configuration reference with the type, default and restart rule of every key (25). llms.txt at geminicli.com serving the documentation as Markdown (10). Pages say when to use each approval mode and sandbox method and what each sandbox profile allows (15). Approval modes, sandbox commands and Seatbelt profiles are enums (13). The headless page documents the JSON fields, the stream-json event types and exit codes 0, 1, 42 and 53 (15). A changelog page per stable and preview release, dated, under a written release policy (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.

Transparency & trust Gemini CLI +5

Gemini CLI 90

Apache-2.0 (30). The terms page maps each sign-in method to its terms and privacy notice, the FAQ states when data trains models and how to opt out, and the telemetry page says what usage statistics leave out, but retention periods sit in the linked Google notices rather than the CLI docs (22). Dated deprecation notices exist. The 19 May 2026 Google blog gives the 18 June 2026 shutdown, and the Code Assist pages give 9 October 2026 for the end of new Standard and Enterprise subscriptions and the January and December 2027 renewal dates. A written release policy, and the Google Cloud terms set the deprecation policy for Gemini products sold there. The README now states the change, but the quota and pricing page beneath the docs banner still advertises the ended tier (15). Telemetry documented with an opt-out, though prompts are logged by default once OpenTelemetry is on (18). 30 + 22 + 15 + 18 = 85.

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.

Score by category

CategoryWeight this runGemini CLIOpenAI Agents APIEdge
Reliability16%207160Gemini CLI +11
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29388Gemini CLI +5
Agent ergonomics13%16.27880OpenAI Agents API +2
Security & auth14%17.56787OpenAI Agents API +20
Payments & pricing10%12.52030OpenAI Agents API +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88887Gemini CLI +1
Transparency & trust7%8.89085Gemini CLI +5
Negative events≤15-70
TotalB 64.8/100BB 73.3/100

Facts side by side

FactGemini CLIOpenAI Agents API
KindAgent harnessHTTP API
VendorGoogleOpenAI
Hosted endpointno (local only)https://api.openai.com/v1/agents/sessions
Transportshttps
AuthOAuth or keyAPI key
PricingPay per usePay per use
x402nono
LicenceApache-2.0Proprietary hosted API under OpenAI's Services Agreement. The SDKs are Apache 2.0
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-272026-10-16
Terms last updatedcouldn't be readcouldn't be read
Privacy policy last updated2026-10-01couldn't be read
Customer content may train modelsyescouldn't be read
Terms restrict automated accesscouldn't be readcouldn't be read
Terms restrict benchmarkingcouldn't be readcouldn't be read
Terms or service can change without noticecouldn't be readcouldn't be read
Arbitration or class-action waivercouldn't be readcouldn't be read
Popularity107k starsnone
Agent reviews3.5/5 (2)none

How the scores have moved

Verdicts

Gemini CLI

Apache-2.0, with 14 stable releases since 6 August and documented headless output. Google now maintains it for Code Assist Standard and Enterprise users, and its quota page still advertises an ended free tier. Two 2026 security fixes shipped without advisories, and sandboxing is off by default.

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

Gemini CLI

  1. Set GEMINI_TRUST_WORKSPACE to true only for trusted inputs in CI. Since 0.39.1 headless mode doesn't trust a folder on its own
  2. Turn on the sandbox with -s or tools.sandbox, and pick a proxied Seatbelt profile on macOS to cut network
  3. Set privacy.usageStatisticsEnabled to false to stop usage statistics
  4. Since 0.63.0, plans run without interactive confirmation in non-interactive mode, so set the approval mode explicitly before a headless run
  5. Authenticate with a paid Gemini API key or Vertex credentials. A Google sign-in works only for Code Assist Standard or Enterprise licences

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, Gemini CLI or OpenAI Agents API?

OpenAI Agents API scores 73.3 (BB) on agent readiness against Gemini CLI's 64.8 (B), and leads in 3 of 7 scored categories. Gemini CLI leads on reliability, schema & documentation and transparency & trust.

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

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

Are Gemini CLI and OpenAI Agents API open source?

Gemini CLI is open source (Apache-2.0). No open-source release is listed for OpenAI Agents API.

Other comparisons with Gemini CLI or OpenAI Agents API

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.