AI companions · privacy architecture

For an AI companion, the model boundary is the privacy boundary.

Companion conversations invite personal disclosure. Persona runs its documented inference and memory path on the iPhone. Character.AI and Replika operate cloud services with accounts, service-side processing and different safety systems. The right choice depends on more than personality.

Publisher-authored comparisonSources checked 15 July 2026How we compare

Status and authorship. HighRoad publishes Persona, so this is first-party analysis, not an independent review. Product facts were checked against the current repository. Current status: Release candidate; public App Store listing not yet live.

One-glance comparison

DecisionPersonaCloud companion service
InferenceRuns on the iPhone after model downloadRequests processed by provider infrastructure and, in some cases, model partners
Conversation memoryLocal three-layer memory with user review controlsAccount-scoped service memory and history
AccountNot required for the documented local pathTypically required for persistent service use
Model capacityConstrained by phone memory and batteryCan use larger server models
Sync and webPrimarily device-localUsually stronger cross-device and web access
StatusRelease candidate; Store listing not liveLive services; policies and age rules can change

Read the data path, not the adjective “private”

On-device means the prompt can be processed without sending it to a model provider. Apple’s Core ML documentation explains the general advantage: strictly device-side execution removes the network requirement and helps keep data private. Persona’s repository describes local inference, local memory extraction and user-controlled deletion.

A cloud service may still apply strong encryption, access controls and contractual limits. It nonetheless needs to process conversation content to generate a reply. Replika’s current privacy policy explicitly describes messages, personalised conversation processing and third-party language-model providers; Character.AI’s policy describes the categories it collects and processes for its service.

Cloud and local products carry different safety risks

A local app reduces server exposure but cannot outsource moderation or recovery to a constantly updated service. Smaller models can be less capable and less predictable, and a deleted device without a backup can mean a lost history.

A cloud app can operate central safety systems, age controls and cross-device support, but the user must trust the provider’s current handling, retention and incident response. No companion should be treated as a therapist, crisis service or infallible person.

A privacy test that takes five minutes

Before using any companion, locate the privacy policy, account-deletion path, memory controls and current age requirement. Write down whether prompts leave the device, whether service providers receive them, how long messages remain, and what sync means.

Then share only what fits that boundary. Do not disclose another person’s secrets, authentication codes, financial details or health information merely because a character sounds empathetic.

Sources and update policy

Competitor and platform facts link to first-party documentation checked on 15 July 2026. Services change: verify the current regional product, policy and plan pages before deciding. Trademarks belong to their owners; no affiliation or endorsement is implied.

See the editorial policy or report a factual correction to support@highroadsoftware.com.