Grass vs Cursor: Which Should You Use for Mobile Agent Access?

TL;DR: Cursor iOS and Grass both let you control AI coding agents from your phone, but they represent opposite bets. Cursor iOS is a model-aligned client — post-SpaceX acquisition, it runs inside Cursor's cloud infrastructure and defaults toward Grok. Grass is a model-neutral control layer — it runs Claude Code, Codex, and OpenCode with equal priority, your API keys never transit Grass servers, and there is no vendor lock-in. If you use Cursor IDE and are comfortable with the xAI direction, Cursor iOS is the natural extension. If you use Claude Code, Codex, or OpenCode — or if you want to stay independent of any model vendor — Grass is the only mobile surface built for that use case.

What changed: Cursor iOS launch and SpaceX acquisition

Two events in summer 2026 permanently reframe the Cursor vs Grass comparison.

Cursor iOS launched June 29, 2026 as a public beta with a "Remote Control" feature. The app lets you monitor Cursor agent sessions, approve tool calls, and resume cloud agent loops from your iPhone. At launch, the Remote Control feature moved the agent execution loop to Cursor's cloud infrastructure — meaning the agent runs on Cursor's servers, not your local machine or a VM you control. Cloud agents worked reliably at launch; the local Remote Control path (where your local Cursor session appears in the mobile app) had documented friction, with multiple developers reporting sessions failing to appear after following setup steps.

SpaceX's acquisition of Cursor closed August 14, 2026 for approximately $60 billion. Since closing, Cursor's model pool has shifted: Cursor Models now default to Grok 4.5/4.6 (jointly trained with xAI), OpenAI models are scheduled to exit Cursor on November 12, 2026 following OpenAI's official termination notice, and Anthropic models are "hidden by default" in the model selector. The formerly multi-model IDE is becoming a Grok-first platform. As one developer summarized on Reddit: "Cursor is now just going to be a Grok shop, just like Claude Code is only Anthropic, they won't be wanting to send money to OpenAI or Anthropic."

These two events are not independent stories. Cursor iOS was architected as a Cursor IDE extension — not as a neutral agent control layer. The iOS app connects to Cursor's cloud, runs Cursor agents, and inherits Cursor's model alignment. After the SpaceX acquisition, choosing Cursor iOS means choosing the xAI ecosystem for your mobile agent surface. That may be exactly what you want. But it is a meaningful architectural commitment.

The core architectural divide: control layer vs. model-aligned client

Cursor iOS is a client for the Cursor IDE ecosystem. It extends Cursor's existing agent infrastructure to your phone. Cloud agents run on Cursor's infrastructure; Remote Control attempts to bridge your local Cursor IDE session to the mobile app via Cursor's cloud relay. Agent execution happens inside Cursor's environment, under Cursor's (now SpaceX's) infrastructure. Model choices default toward Grok, and the platform's model-provider relationships — with OpenAI exiting and Anthropic sidelined — are contracting rather than expanding.

Grass is an agent-agnostic control layer. It is not affiliated with Anthropic, OpenAI, or any model vendor. Grass runs Claude Code, Codex, and OpenCode as equal first-class citizens from a single mobile surface. The CLI (@grass-ai/ide) runs on your laptop or a cloud VM you control, connects your phone to that session over WiFi or Tailscale, and your API keys never leave your network. The cloud VM product (codeongrass.com) runs on Daytona infrastructure under your control. There is no Grass cloud relay for agent execution — the agent runs where you put it.

The defining question is not "which app has a better UI." It is: do you want your mobile agent surface owned by a model vendor, or independent of one?

Feature comparison: Grass vs Cursor iOS

How Cursor iOS Remote Control actually works

Cursor iOS has two modes. Cloud agents run on Cursor's infrastructure — you start an agent task in the mobile app and it executes on Cursor's servers. This worked reliably at launch and is the primary mobile experience Cursor is pushing. Remote Control attempts to connect your local Cursor IDE session to the mobile app via Cursor's cloud relay. At launch, multiple developers reported local sessions not appearing in the mobile app after following setup steps exactly. One representative report: "in my iOS cursor app, even if I turned on the agents → remote control, and then typed in /remote-control in my local repo session, the session still no show in my iOS cursor app, only cloud agents are there."

The practical implication: if you want reliable Cursor iOS access today, you are using cloud agents — which means your code executes on Cursor's (SpaceX's) infrastructure, not on your own machine. For proprietary codebases or security-sensitive work, that is a meaningful distinction.

How Grass works on mobile

Grass uses a local server model. You run grass start in your project directory, which launches an HTTP server on port 32100–32199. The mobile app scans a QR code to connect over your local network (or Tailscale for remote access). The agent — Claude Code, Codex, or OpenCode — runs in your project directory on your machine or a VM you control. Your API keys are passed directly to the agent; they never transit Grass servers.

Sessions survive disconnects via SSE replay. If your phone connection drops and reconnects, the server replays buffered events from the last received position. Permission requests — when the agent wants to run a bash command, write a file, or make a web request — appear as native modals in the mobile app. You tap Allow or Deny; the agent receives the response immediately and continues or stops accordingly.

The cloud VM product on codeongrass.com adds persistent Daytona workspaces — the agent keeps running even when your laptop is closed, and you connect to it from your phone anywhere. Grass internal data shows that 68% of sessions start on iPhone and sessions run to 3× completion rate vs. laptop-only, reflecting how much of the agent-blocking friction lives in permission gates that nobody is watching.

For a technical walkthrough of running Claude Code on a persistent VM and connecting via Grass, see How to Set Up Claude Code on Daytona and Setting Up Grass with a Daytona Remote Server. For a broader look at how mobile approval gates fit into a safe agent workflow, see How to Build Human-in-the-Loop Approval Gates for AI Coding Agents.

The model lock-in risk: why it matters now

Before the SpaceX acquisition, Cursor's model-agnosticism was a genuine differentiator. Developers picked Cursor because they could run Claude, GPT-4, Gemini, or whatever was best for the task. That story is ending.

OpenAI issued an official statement announcing termination of Cursor's model access on November 12, 2026: "We cannot be confident that SpaceX will use our technology within our terms of service, based on our experience with Elon Musk's companies violating contracts." The Channel Insider coverage of this exit noted that Anthropic had previously restricted Windsurf access when its acquisition by OpenAI was rumored — the same pattern of model-provider relationships collapsing inside IDE-owned platforms is repeating.

For Cursor iOS specifically, this means the mobile surface marketed as multi-model at launch is contracting toward Grok on a timeline of months. Developers who chose Cursor for model flexibility are now facing a different product than they signed up for. As one developer noted: "The contracts with Anthropic and other providers apparently have 90-day termination clauses, meaning the model powering your editor could quietly switch to Grok before the year is out."

The data sovereignty concern is separate but compounding. SpaceX's IPO filing characterized developer behavior data as a "goldmine." Every repository opened, every suggestion accepted, every permission granted in Cursor iOS flows through Cursor's (now SpaceX's) infrastructure. For teams working on proprietary codebases, it is worth a deliberate decision before defaulting into the Cursor iOS workflow.

Grass's BYOK architecture sidesteps this entirely. The Grass server never sees your code or your API calls — it passes prompts to the agent and streams responses back. The agent's API calls go directly from your machine to Anthropic, OpenAI, or whichever provider you configured. There is no intermediary holding your credentials.

Who should use Cursor iOS

Cursor iOS makes sense if you are already a paid Cursor subscriber and use Cursor IDE as your primary editor, you are aligned with or neutral about the xAI/Grok direction, you want cloud agent execution without managing your own VM or server, and your primary use case is extending your existing Cursor workflow to your phone — not switching agents or running parallel Claude Code and Codex tasks.

For this profile, Cursor iOS is the path of least friction. The cloud agent experience is reliable, the integration is seamless within the Cursor ecosystem, and the platform investment is already made.

Who should use Grass

Grass makes sense if you use Claude Code, Codex, or OpenCode — not Cursor IDE — as your primary agent; if you want to switch between agents without switching control surfaces; if you want your API keys to stay on your own infrastructure; if you are on Android (Cursor iOS has no Android app at launch); if you want to run long-running agent sessions overnight on a persistent VM with phone-based oversight and approval gates; or if you work on a team or a proprietary codebase where data sovereignty matters.

The developer who benefits most from Grass is running multi-hour autonomous tasks, managing parallel repos, and starting to feel the friction of jumping between a sleep-prone laptop and fragmented agent tools. Grass is a machine built for AI coding agents — not an extension of any single IDE.

The broader market context

Between early 2025 and mid-2026, Claude Code and Codex took significant market share from Cursor. Developers who moved to Claude Code or Codex have no mobile control option within Cursor's ecosystem — Cursor iOS serves Cursor IDE users, not Claude Code or Codex users. That gap is exactly what Grass fills.

Developer sentiment after the SpaceX acquisition split into two camps. A Grok-optimist camp finds Grok 4.6 reviews positive and the Cursor $60 plan well-priced. A migrating camp is actively moving to Claude Code, Codex, and OpenCode with model-agnostic tooling. The latter camp has no native mobile agent control option within the tools they've migrated to — which is the market gap Grass occupies.

One developer captured the stakes plainly: "We have two options remaining for the tools we use everyday. You are either in the Microsoft/OpenAI ecosystem, or you are moving to this new SpaceX/Cursor/xAI monolith. The indie dev tool era might be closing." For developers who want neither of those ecosystems to own their mobile agent surface, a neutral option matters.

Verdict

Choose Cursor iOS if you are a committed Cursor IDE user who is comfortable with the xAI model direction and wants the simplest extension of your existing workflow to mobile. Cloud agent execution is reliable, and the integration is seamless within the Cursor ecosystem.

Choose Grass if you use Claude Code, Codex, or OpenCode; if you want your API keys to stay on your own infrastructure; if you need Android support; or if you want a mobile agent surface that stays model-neutral regardless of which vendor relationship shifts next.

The SpaceX acquisition simplified the choice. Cursor iOS is the xAI-aligned mobile client for Cursor IDE users. Grass is the model-neutral control layer for developers who want one surface for every agent, always on, without picking a side.

Frequently asked questions

Is Cursor iOS available for Android?
Cursor iOS is iPhone-only at launch and requires recent iOS; per community reports iOS 26+. Android is listed as "planned" with no announced release date. Grass supports iOS, Android, and web browsers from the same mobile app, with no iOS version requirement.

Does Cursor iOS require a paid plan?
Cursor iOS appears to require an active paid Cursor plan based on community reports; verify against Cursor's current App Store listing before assuming. Grass has a free tier with 10 hours of cloud VM access and no credit card required. The open-source Grass CLI has no usage limits beyond your own API quota.

How does Cursor Remote Control work on iOS — and why does it fail for some users?
Cursor Remote Control is designed to bridge your local Cursor IDE session to the mobile app via Cursor's cloud relay. Multiple developers reported at launch that local sessions did not appear in the mobile app even after following setup steps, and only cloud agents were accessible. Cloud agents — running on Cursor's infrastructure rather than your local machine — worked reliably. The local bridge path appears to be the less-stable option at launch.

After the SpaceX acquisition, which models does Cursor support on iOS?
As of September 2026, Cursor Models default to Grok 4.5/4.6. OpenAI models are scheduled to exit on November 12, 2026 following OpenAI's official termination. Anthropic models remain available but are hidden by default. Grass has no model preferences — it runs whatever model you configure in Claude Code, Codex, or OpenCode, with your own API key.

Does Grass send my code or API keys to any third party?
No. Grass uses a local server model. Your API keys go directly from your machine to the model provider (Anthropic, OpenAI, etc.) — they never pass through Grass. The Grass server only relays prompts and agent events between your mobile app and the agent running on your machine or VM. On the cloud VM product, the agent runs on a Daytona VM under your credentials.

Can Grass replace Cursor iOS if I use both Claude Code and Codex on the same project?
Yes. Grass runs Claude Code and Codex from a single mobile interface. You can switch between agents for different repos without switching apps, and session history is tracked per agent per repo. Cursor iOS does not support Claude Code or Codex — it is limited to Cursor agents.

Grass is a machine built for AI coding agents — an always-on cloud VM where Claude Code, Codex, and OpenCode live as first-class citizens, accessible from your laptop, phone, or an automation. Free tier at codeongrass.com — no credit card.