ADR-010: Retire the Agent + Hangar Cloud Product Tier

Status: Accepted Date: 2026-07-16 Authors: MCP Hangar Team Supersedes: ADR-005 (fully), ADR-006 (fully); ADR-004, ADR-009 (in part)

Context

The hangar-agent Go sidecar and the Hangar Cloud SaaS backend it connected to have been retired:

  • hangar-cloud (the SaaS control plane) — repository archived and private; the REST API no longer exists.
  • mcp-hangar-agent (the Go interceptor sidecar) — repository archived.
  • The hangar-agent Helm chart — removed from helm-charts (helm-charts#43).
  • terraform-provider — a pure Hangar Cloud REST client with no other backend (11 resources + 3 data sources, all against cloud.mcp-hangar.io) — deprecated and archived (terraform-provider#13).
  • Core (mcp-hangar) — the src/mcp_hangar/cloud/ connector, the POST /agent/policy endpoint, the --cloud-key/--cloud-url flags, and the agent RBAC role are removed (mcp-hangar#490).

Four accepted ADRs assumed a live agent/cloud tier and are now partly or wholly invalidated.

Decision

Retire the agent + Hangar Cloud tier as a product surface. The supported deployment surface is the open-source control plane (mcp-hangar) + the Kubernetes operator + the Helm charts. Governance stays where it already runs live — in-process in core (per-tenant tool projection, digest pinning, and policy resolution on the call path) — not in an external interceptor sidecar or a SaaS control plane. Kernel-level runtime enforcement, which only ever made sense delivered through the agent, is retired with it.

Consequences

Supersedes

  • ADR-004 (SEP-1766 digest pinning) — partially superseded. The digest-pinning capability lives on, in-process in core (core already enforces per-tenant digest pins on the call path). ADR-004's component split — hangar-agent extracts digests, hangar-cloud stores the approved allowlist — is void. The capability stays in core; the agent/cloud scoping is dropped.
  • ADR-005 (SEP-1763 interceptor compliance) — fully superseded. The "hangar-agent as reference interceptor sidecar" roadmap is abandoned. Any continued SEP-1763 / interceptor alignment is in-process in core (see the experimental interceptor work, mcp-hangar#488), not a sidecar runtime.
  • ADR-006 (Tetragon runtime enforcement) — fully superseded. The enforcement pipeline it describes originated in Hangar Cloud (the MCP policy DSL) and hangar-agent (the policy compiler); with both retired, the kernel-level runtime-enforcement productization (Tetragon / KubeArmor / Falco backends) is retired as well. Governance is enforced in-process on the MCP call path, not via kernel hooks. If runtime enforcement is ever revived it will be a new decision on its own footing, not a continuation of this one.
  • ADR-009 (independent release topology) — partially superseded. The "four independent release lanes" become three: core, operator image, and OCI Helm charts. The agent-image lane (the fourth lane) is retired and its open follow-up ("author the agent release.yml") is closed won't-do.

Explicitly unaffected

Core multi-tenancy, front-door mode, per-tenant tool projection, OIDC trust, and the ToolAccessResolver / policy:write machinery are live features unrelated to the agent and are untouched. policy:write remains a valid permission, now granted via the admin role. The durable PolicyPushRejected event is retained (deprecated, producer-less) for event-replay compatibility.

References