Foundry Hosted Agents (Azure)

Foundry Hosted Agents are Fabric Harness's primary Azure target. The build target emits a Dockerfile, an azd project file, Bicep infra, and Foundry agent metadata.

Status: scaffold + preview metadata. This target emits deployable scaffolding ready for azd up. Live Hosted Agent create/update/invoke is pending Azure MCP Foundry discovery or an official stable Hosted Agent deployment schema.

Build

fh build --target foundry-hosted-agent

Output:

.fabricharness/build/foundry-hosted-agent/
  Dockerfile
  azure.yaml
  foundry-agent.yaml
  infra/main.bicep
  dist/server.mjs
  manifest.json

You can also build the worker variant:

fh build --target foundry-hosted-agent --runtime temporal-worker
fh build --target foundry-hosted-agent --runtime node

Deploy

cd .fabricharness/build/foundry-hosted-agent
azd up

azd provisions the Foundry project, identity, networking, and deploys the container image.

Why Foundry

Foundry capability	Why it matters for Fabric agents
Per-session hypervisor sandbox	Maps 1:1 onto Fabric's `SandboxEnv` semantics.
Disk persistence across scale-to-zero	Backs `sandbox.snapshot()` / `restore()`.
Per-agent Entra Agent ID + on-behalf-of (OBO) auth	Fits Fabric's two-identity actor schema.
Foundry-native Azure OpenAI access	Models, identity, and observability in one runtime.
Toolbox, Memory (preview)	Optional Fabric integrations, behind feature flags.

Architecture decision

Fabric runs inside the Foundry session substrate. Foundry provides the per-session sandbox; Fabric provides the harness loop, governance, and (optionally) Temporal durability.
Temporal workers run outside Foundry. Use the temporal-worker runtime variant when you need durable, replayable agent sessions; the worker calls Foundry-hosted activities for sandbox effects.
Entra Agent ID + OBO identities are recorded in the session entry's actor field so audit trails answer "which agent acted, on whose behalf, who approved?".
Foundry preview integrations (Toolbox, Memory, Activity Protocol) live in @fabric-harness/azure only — no Foundry SDK types leak into @fabric-harness/sdk.

Identity model

actor?: {
  agentId?: string;        // Entra Agent ID
  onBehalfOf?: string;     // upstream user identity
};

Approval requests record both identities for compliance.