Air-gapped instant messaging: selection and deployment

Air-gapped means no routed path between the deployment and the internet: software enters via removable media, updates arrive as offline packages, and monitoring and logs close the loop inside the network. True isolation is far stricter than “private cloud” — a private cloud still runs on someone else's infrastructure, while in an isolated network every layer (database, message queue, object storage, monitoring) must live inside. Overseas vendors serving defense and critical infrastructure have turned this into a mature market, proving the demand is real, well-funded, and evaluated in a standardized vocabulary: no phone-home, auditable, upgradable offline.

For every candidate, demand evidence per item rather than verbal assurances:

• No phone-home: enumerate every outbound connection attempt (license checks, update probes, crash reports, fonts and CDNs) and confirm each can be disabled
• Offline install: installation media that never touches public registries (tarballs / private image repositories)
• Bundled dependencies: database, cache, message queue and object storage deployable in-network, no cloud-service dependency
• Local licensing: licenses validate locally, without a vendor activation server
• Local identity: auth integrates with in-network LDAP / OIDC rather than public SSO
• Monitoring loop: metrics and health checks feed in-network Prometheus-class systems
• Offline upgrades: a formal offline package and rollback path for version upgrades
• Client reality: mobile push depends on vendor channels, so isolated networks lean on web / desktop clients — plan agent and user access accordingly

IMCore's deployment units are friendly to offline scenarios: a single Go binary with no runtime downloads; Compose and Helm layouts where PostgreSQL, Redis, RabbitMQ and MinIO ship as bundled dependencies whose images can be pre-loaded into an in-network registry; licensing via locally verified signed files with no online activation; no server-side telemetry. Operations provide systemd unit generation and health probes, with metrics exposed on a standard Prometheus interface for in-network monitoring.

For acceptance in an isolated environment, work the checklist literally: capture egress traffic after installation to confirm zero outbound connections, rehearse the offline upgrade package and its rollback in a mirrored environment, then distribute the agent workbench and web clients to users.