Castmates: Private, On-Device AI Roleplay for iPhone

Introduction

Castmates is a roleplay application designed exclusively for iPhone. It allows users to engage in deep, cinematic storytelling with 32 hand-crafted AI characters. The app distinguishes itself by running entirely on the device. This means conversations never leave the user's phone, no internet connection is required, and no account creation is necessary.

Benefits

Castmates offers several key advantages that set it apart from other AI apps. First, it is 100% private. The app uses local inference architecture, which means the AI model runs directly on the iPhone. Conversations are generated and stored locally. They are never sent to a server, used for training models, or logged by a third party. Users do not need to sign up or create a profile. The app only sends anonymous usage statistics.

Second, the characters have real depth and memory. The app includes a cinematic cast of 32 unique characters. Each one has a distinct voice, backstory, and the ability to narrate scenes. Characters do not reply with flat one-liners. Instead, they include actions and descriptions, such as a detective lighting a cigarette or a knight drawing a sword. The app also summarizes past sessions. This allows characters to recall who the user is and the history of the story, even if the user returns days or weeks later.

Third, users can create their own characters. They can define a persona, including name, tagline, genre, personality, and tone. They can choose an interaction style like friendship, romance, mentorship, or rivalry. Users can also set an avatar using a photo from their library and write a custom starting scenario.

Use Cases

Castmates is perfect for anyone who wants to explore stories without worrying about privacy or internet access. Because it works offline, users can roleplay on planes, in subways, or in areas with no signal. It is ideal for fans of specific genres like noir detective stories, fantasy, sci-fi, or historical dramas. The app includes characters like a hardboiled detective, an elven ranger, a sardonic ship AI, and a pirate captain.

The app is also great for creative writing. Users can build their own characters and test out different storylines. The long-term memory feature helps maintain continuity in long-running narratives. It serves as a tool for entertainment, relaxation, and creative exploration. The mature mode option allows for romance-forward roleplay for users who are 18 and older.

Pricing

Castmates offers a tiered pricing structure. All plans keep conversations on the device.

The Free Plan costs $0. It gives users access to the full safe-for-work cast of 32 characters. Users get 10 messages per day and can create one custom character. No account is required.

The Pro Plan offers more flexibility. The monthly cost is $9.99. The annual cost is $39.99, which saves about 50 percent. There is also a lifetime option for $59.99. This is the best value for long-term users. The Pro plan includes unlimited messages, unlimited custom characters, and access to the mature mode. Users can cancel anytime via the App Store.

Vibes

The app emphasizes privacy and personal ownership of the story. The tagline is "Your story. Your phone. No one else." This message resonates with users who are concerned about data security. The ability to play without an internet connection adds a sense of freedom and reliability. Reviews and public reception highlight the unique selling point of on-device processing. Users appreciate that their personal conversations remain private and are not shared with external servers.

Additional Information

Castmates requires an iPhone running iOS 17 or later. The on-device model requires a one-time download of approximately 2 GB. This space can be freed up anytime by deleting the model. Generating replies uses the iPhone's chip similarly to a game. Long sessions consume more power than standard texting, but the app is light for day-to-day use and does not run in the background. The app includes 32 hand-crafted characters across eight genres, totaling 96 ready-made scenarios.