Concepts

Agent context

Give an agent durable storage for files, memory and results.

Agent context is durable storage that belongs to an agent. It holds the files that the agent works on, the observations that it keeps, the knowledge that it builds and the results that it produces.

Agent context is not the context window of a model. It is storage that continues to exist after a run ends.

Beta, and a separate installation

Sentinel provides agent context through Context Service. Context Service is not part of the Sentinel installation. Install it first, and then configure Sentinel to use it.

Enable the integration#

The integration is inactive while CONTEXT_SERVICE_URL is empty. A cluster administrator sets the address in the Helm chart:

# context-service-values.yaml
ui:
  backend:
    contextServiceUrl: http://context-service.serverless-harness.svc.cluster.local:8080

helm upgrade sentinel ./charts/sentinel \
  --namespace sentinel-system \
  --reuse-values \
  -f context-service-values.yaml

To disable the integration, set the value to an empty string.

The four context types#

Type	Purpose
`workspace`	Files that the agent changes. This type is the default.
`memory`	Observations that the agent keeps.
`knowledge`	Understanding that the agent builds and uses again.
`artifacts`	Reports, media and other results.

Note

The type is a label only. Each type is a Kubernetes PersistentVolumeClaim, and all four types operate in the same way today. The four names exist so that the interface stays stable when type-specific behaviour arrives. Do not expect memory to do more than workspace does.

The two access modes#

Option	Kubernetes mode	Meaning
default	`ReadWriteOnce`	Pods on one node at a time can write.
`--shared`	`ReadWriteMany`	Pods on more than one node can write at the same time.

ReadWriteOnce is not a security boundary. It does not limit the volume to one pod. Pods on the same node can all use the volume.

Use --shared when agents on different nodes need the same files. Confirm first that your storage class supports ReadWriteMany.

Create a context#

List the storage that the cluster offers. This command uses the Sentinel interface, so you do not need direct access to Kubernetes:

sentinel context storage-classes

Create a context:

sentinel context create research \
  --shared \
  --size 1Gi \
  --storage-class ibm-scale-csi

sentinel context list
sentinel context get research

If you omit --storage-class, the command uses the default storage class of the cluster.

The other types use the same options:

sentinel context create research-memory    --type memory    --size 5Gi
sentinel context create research-knowledge --type knowledge --shared --size 10Gi
sentinel context create research-results   --type artifacts --shared --size 20Gi

Give a context to an agent#

Name the context and the path when you import the agent:

sentinel agents import \
  --deployment-type statefulset \
  --context research:/workspace \
  from-image --name research-agent --containerImage IMAGE

A sandboxed agent uses the same option:

sentinel agents import \
  --deployment-type sandbox \
  --context research:/workspace \
  from-image --name research-sandbox --containerImage IMAGE

You can attach any type at any path. For example, use --context research-memory:/memory. Sentinel accepts the attachment after Context Service returns a claim.

Delete a context#

A context has its own life cycle. When you delete an agent, its context continues to exist:

sentinel agents delete research-agent
sentinel context delete research

Delete the agents before you delete the context.

Deletion has no dependency check

The sentinel context list command reports whether the storage is ready. It does not report which agents use the storage. If you delete a context that an agent uses, Sentinel does not reject the request and does not give a warning.

Kubernetes does not remove a volume while a pod uses it. The claim stays in the Terminating state instead. That behaviour is a protection, not a dependency check. For the design of usage reporting and safe deletion, follow context-service#2.