BayesChat vs OpenCat — Native iOS BYOK Clients Compared (2026)

Sep 18, 2026

OpenCat is the most established native Apple client in the BYOK space — and as of September 2026 it supports MCP, local models, and multiple model sources on Mac, iPhone, and iPad. BayesChat is newer, built on the same "native SwiftUI + BYOK" idea for iPhone and iPad (Mac coming soon). Since the feature lists now overlap a lot, this comparison focuses on what actually differs: pricing model, privacy architecture, and workflow design.

What they agree on (so we can skip it)

Both apps are native on Apple platforms, both let you bring your own API key, both connect to local models like Ollama and LM Studio over OpenAI-compatible URLs, and both support MCP tool calling. Credit where it's due — OpenCat's flexibility across model sources (API keys, cloud subscription, Apple Intelligence, local models) is the widest in its category, and it already ships on Mac today.

Difference 1: How you pay

OpenCat: free to download; premium features via subscription (monthly or annual). Its cloud-usage option lets you pay for tokens through the app — with Apple's 30% commission deducted from what your money buys, per OpenCat's own FAQ.
BayesChat: free tier with limits; Pro is $14.99 one-time, lifetime. No hosted AI service exists inside the app at all, so there's nothing to subscribe to and no markup on your tokens — you always pay providers directly at cost.

If you keep an AI client for years, one-time pricing usually wins on total cost. If you prefer a low monthly commitment, OpenCat's model is perfectly reasonable.

Difference 2: Where your data can go

OpenCat keeps data local by default, with iCloud sync available as an option.
BayesChat has no sync and no cloud: keys in the Apple Keychain, history in SwiftData on device, no account system. The architecture has no server component that could receive your chats.

This is a values choice, not a checkbox. iCloud sync is genuinely convenient; "nothing leaves my device, ever" is genuinely private. Pick the one you believe.

Difference 3: Workflow design

This is the most practical difference in daily use:

BayesChat is preset-centric. You save model + system prompt + parameters
- MCP tools as named Chat Presets and switch in one tap — a coding agent preset, a cheap daily-model preset, a web-search preset. Themes, styled PDF/HTML export, and one-file backup sit around that workflow.
OpenCat is feature-broad. Translation, writing, search, keyboard extension, Siri Shortcuts, and agent modes live in one flexible app; you configure per conversation rather than through a full preset system.

If you keep restarting the same configurations, presets remove that friction. If you explore new setups constantly — or need Mac + iOS today — OpenCat's breadth fits better.

Side by side

	BayesChat	OpenCat
Native SwiftUI	Yes (iPhone, iPad; Mac coming soon)	Yes (Mac, iPhone, iPad)
BYOK	Core model, only model	Supported
Local models (Ollama/LM Studio)	Yes	Yes
MCP tool calling	Yes (Pro)	Yes
Pricing	$14.99 once	Subscription
Cloud sync	None — device-only	iCloud optional
Account required	No	Apple account for sync
Hosted AI service	None	Optional (pay-as-you-go)
Chat Presets	Full (model + prompt + tools)	Prompt / mode oriented

Checked September 2026 from public app-store listings and vendor pages.

Switching from OpenCat to BayesChat

Copy your provider API keys from OpenCat's settings.
Install BayesChat free, add the same providers, paste each key.
Recreate your common setups as Chat Presets.
Export any conversations you want to archive from OpenCat first — BayesChat keeps history on-device and does not import chat logs.

The verdict

Maximum flexibility, Mac today, and iCloud sync in a mature native app; subscription is fine: OpenCat is a strong choice with nothing to apologize for.
One-time purchase, strict device-only privacy, preset-driven workflow on iPhone/iPad: BayesChat.

Both are native, both respect BYOK — the difference is which trade-offs you want to live with.