diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 137dd516..dae00344 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -127,7 +127,11 @@ cd workspace-server && go test -race ./...
 cd canvas && npm test
 
 # Workspace runtime (Python)
-cd workspace && python -m pytest -v
+# Runtime code is SSOT in molecule-ai-workspace-runtime, not molecule-core/workspace.
+cd ../molecule-ai-workspace-runtime
+python -m venv .venv && source .venv/bin/activate
+pip install --index-url https://git.moleculesai.app/api/packages/molecule-ai/pypi/simple/ -e . pytest pytest-asyncio
+pytest -q
 
 # E2E API tests (requires running platform)
 bash tests/e2e/test_api.sh
@@ -159,6 +163,19 @@ and run CI manually.
 | review-check-tests | `review-check.sh` evaluator regression suite (13 scenarios) |
 | ops-scripts | Python unittest suite for `scripts/*.py` |
 
+### Workspace runtime SSOT
+
+Runtime code lives in
+[`molecule-ai-workspace-runtime`](https://git.moleculesai.app/molecule-ai/molecule-ai-workspace-runtime).
+Do not reintroduce `molecule-core/workspace/` or vendored `molecule_runtime/`
+copies in consumers. Core and templates consume the published runtime package
+from the Gitea package registry.
+
+For local external MCP agents, multi-workspace config is
+`MOLECULE_WORKSPACES=[{"id":"...","token":"...","platform_url":"..."}]`.
+`platform_url` selects the tenant; `org_id` is not part of this config.
+Workspace IDs can differ across orgs.
+
 ## Local Testing
 
 ### review-check.sh
diff --git a/docs/guides/external-agent-registration.md b/docs/guides/external-agent-registration.md
index 5c7f25bd..4db4a42b 100644
--- a/docs/guides/external-agent-registration.md
+++ b/docs/guides/external-agent-registration.md
@@ -285,6 +285,39 @@ Canvas requests (no `X-Workspace-ID` header) and system callers
 
 ---
 
+## Multiple Workspaces From One Local MCP Bridge
+
+The standalone runtime package includes `molecule-mcp`, a local MCP bridge for
+external agents such as Claude Code, Codex, Hermes, and other tools that run
+outside the platform container fleet. One local bridge can serve multiple
+external workspaces by setting `MOLECULE_WORKSPACES`:
+
+```json
+[
+  {
+    "id": "workspace-id-local-to-hongming-org",
+    "token": "...",
+    "platform_url": "https://hongming.moleculesai.app"
+  },
+  {
+    "id": "different-workspace-id-local-to-agents-team-org",
+    "token": "...",
+    "platform_url": "https://agents-team.moleculesai.app"
+  }
+]
+```
+
+`platform_url` is the tenant routing key. The bridge registers, heartbeats,
+polls inboxes, and sends outbound A2A calls against the URL attached to the
+workspace that is doing the work.
+
+Do not add `org_id` to this config. The tenant already comes from
+`platform_url`, and the bearer token is issued by that tenant. Workspace IDs
+also do not need to be shared across orgs; each tenant can return its own
+workspace ID and token for the same local agent process.
+
+---
+
 ## Canvas Appearance
 
 External workspaces appear on the canvas with a purple **REMOTE** badge
diff --git a/docs/guides/external-workspace-quickstart.md b/docs/guides/external-workspace-quickstart.md
index c83c90d6..fdf36b2f 100644
--- a/docs/guides/external-workspace-quickstart.md
+++ b/docs/guides/external-workspace-quickstart.md
@@ -135,6 +135,33 @@ The `id` field is your workspace ID — remember it.
 
 ---
 
+## Optional — one local MCP bridge, multiple tenants
+
+If your local agent runtime uses `molecule-mcp`, one process can serve more
+than one external workspace:
+
+```bash
+export MOLECULE_WORKSPACES='[
+  {
+    "id": "workspace-id-local-to-you-org",
+    "token": "...",
+    "platform_url": "https://you.moleculesai.app"
+  },
+  {
+    "id": "different-workspace-id-local-to-team-org",
+    "token": "...",
+    "platform_url": "https://team.moleculesai.app"
+  }
+]'
+molecule-mcp
+```
+
+Use the workspace ID and token returned by each tenant. The IDs may differ
+across orgs. `org_id` is not required here because `platform_url` selects the
+tenant and the token is tenant-scoped.
+
+---
+
 ## Step 4 — Chat with it
 
 1. Open your Molecule canvas at `https://<TENANT>`
diff --git a/docs/guides/remote-workspaces.md b/docs/guides/remote-workspaces.md
index a6740665..fddbc267 100644
--- a/docs/guides/remote-workspaces.md
+++ b/docs/guides/remote-workspaces.md
@@ -125,6 +125,33 @@ The agent appears on the canvas with a **purple REMOTE badge** within seconds. F
 
 ---
 
+## Multi-Tenant Local MCP Bridge
+
+For local MCP-driven agents, use the standalone runtime's `molecule-mcp`
+entrypoint. A single local bridge can serve multiple external workspaces by
+setting `MOLECULE_WORKSPACES`:
+
+```json
+[
+  {
+    "id": "workspace-id-local-to-acme",
+    "token": "...",
+    "platform_url": "https://acme.moleculesai.app"
+  },
+  {
+    "id": "different-workspace-id-local-to-ops",
+    "token": "...",
+    "platform_url": "https://ops.moleculesai.app"
+  }
+]
+```
+
+`platform_url` selects the tenant for registration, heartbeat, inbox polling,
+and outbound A2A routing. `org_id` is not required in this config, and the
+workspace IDs do not need to match across tenants.
+
+---
+
 ## What Phase 30 Covers
 
 | Phase | What shipped | Endpoint |