Ports and file paths

This is the reference for the network ports and filesystem paths Kerno uses on your machine.

Ports

Service	Default port	Override
Agent REST API (used by the IDE extension and CLI)	8085	PORT env var
MCP server (used by coding agents)	8086	MCP_PORT env var

Both ports listen on localhost only and are not reachable from other machines on your network.

If the default port is taken, Kerno auto-allocates a free one. The actual port is always printed in the output of kerno mcp. Always copy the URL from the terminal rather than assuming the default.

File paths

Kerno uses three locations on your filesystem.

~/.kerno/

Installed agent binaries, runtime state, and per-workspace data.

Path	Purpose
~/.kerno/assets/agent/{version}/aicore-agent/	Installed agent JAR
~/.kerno/assets/runtime/{version}/custom-jre/	Custom JRE bundled with the agent
~/.kerno/workspaces/	Per-workspace snapshots and indexed data
~/.kerno/ (top level)	Agent port, PID, workspace, and version state files

.kerno/ (in your repository)

Per-app directory Kerno creates inside your repository. In a monorepo, each enabled app has its own .kerno/ under that app's root.

Kerno auto-writes a .kerno/.gitignore that ignores hooks/* and mcp-jobs/*, so you do not need to add anything to your repo's own .gitignore for those. The rest of .kerno/ is intended to be committed alongside your code.

Persistent state

Path	Purpose
scenarios/endpoints/<METHOD>/<path>/	Generated TypeScript scenario files (*.scenario.ts), grouped by endpoint
analysis/	Markdown reports from Kerno's analysis (workspace, endpoints, environment), reused as context across runs
hooks/	Git hooks Kerno installs in your repo (ignored)
mcp-jobs/<job_id>.log	Logs for in-flight MCP async jobs (ignored)

Build artifacts

Written when you build the environment for the app. Kerno regenerates them when you apply feedback and rebuild.

File	Purpose
Dockerfile	Dockerfile Kerno generates to build your app
docker-compose.yml	Main orchestration compose that ties all services together
docker-compose.sut.yaml	Compose definition for your app (the system under test)
docker-compose.<service>.yaml	Compose definition for each detected dependency, for example docker-compose.postgres.yaml
docker-compose.ts-sandbox.yaml	Compose definition for Kerno's sandbox container, which transparently intercepts outbound HTTPS from your app so external APIs can be mocked locally
.env	Environment variables for your app
.env.<service>	Environment variables for each dependency, for example .env.postgres

/tmp/kerno/

Temporary working directory for compose projects and scenario workspaces.

Path	Purpose
/tmp/kerno/compose/...	Generated Docker Compose projects
/tmp/kerno/scenario-workspace/...	Working directory for scenario planning

Removing Kerno

To stop the agent and remove the installed binaries, run:

kerno uninstall

This stops the running agent and clears ~/.kerno/assets/ (the agent JAR and bundled JRE). Other state — ~/.kerno/workspaces/, your repository's .kerno/ directory, and any /tmp/kerno/ data — is preserved unless you delete it manually.