diff --git a/docs/REPO_DESCRIPTOR_GUIDE.md b/docs/REPO_DESCRIPTOR_GUIDE.md
index 81a69bf..6a8de75 100644
--- a/docs/REPO_DESCRIPTOR_GUIDE.md
+++ b/docs/REPO_DESCRIPTOR_GUIDE.md
@@ -58,6 +58,7 @@ The descriptor should reference this shared context and vocabulary rather than r
 - `roleOSSubstrate`
 - `rolePublicDocsSurface`
 - `roleStarterScaffold`
+- `roleDeveloperToolchain`
 
 ## Current rule of use
 
@@ -76,3 +77,4 @@ Next we should add one real `semantic/repo.jsonld` file to each core repo:
 - `SociOS-Linux/SourceOS`
 - `SociOS-Linux/socios`
 - `SociOS-Linux/socioslinux-web`
+- `SourceOS-Linux/sourceos-devtools`
diff --git a/docs/adr/ADR-2026-04-devtools-boundary.md b/docs/adr/ADR-2026-04-devtools-boundary.md
new file mode 100644
index 0000000..283ccfd
--- /dev/null
+++ b/docs/adr/ADR-2026-04-devtools-boundary.md
@@ -0,0 +1,47 @@
+# ADR: Developer Tools Repo Boundary
+
+**Date:** 2026-04-30  
+**Status:** Accepted
+
+---
+
+## Context
+
+SourceOS needs a dedicated home for Linux-native developer tooling: Nix/devshell orchestration, NLBoot/operator tooling, lab profile selection, release tooling, local AI governance utilities, and SourceOS workstation bootstrap scripts.
+
+Without a clear boundary, developer tooling risks drifting into `sourceos-spec` (the typed-contract registry) or into OS substrate repos, causing confusion about ownership, validation scope, and consumable contracts.
+
+## Decision
+
+`SourceOS-Linux/sourceos-devtools` is established as the canonical home for all SourceOS developer tooling. Its topology role is `roleDeveloperToolchain`.
+
+`sourceos-spec` registers the repo in the canonical topology (repo descriptor example and `connectsTo` link) but does **not** carry any devtools implementation, shell scripts, Nix expressions, or operator tooling.
+
+Specifically, `sourceos-devtools` owns:
+
+- Nix flakes and devshell configurations
+- NLBoot operator and lab-profile selection scripts
+- Release tooling (cut, sign, publish)
+- Local AI governance CLI utilities
+- SourceOS workstation bootstrap helpers
+- `repo.maturity.yaml` for its own maturity tracking
+
+## Alternatives considered
+
+| Alternative | Reason not chosen |
+|-------------|------------------|
+| Embed devtools in `sourceos-spec` | Violates the typed-contract-registry boundary; spec must stay normative-only |
+| Embed devtools in `agentos-spine` | Spine owns Linux integration, not developer ergonomics or release tooling |
+| Embed devtools in `SourceOS` (substrate) | Substrate is immutable OS layer; devtools are operator-time, not build-time |
+
+## Consequences
+
+- `sourceos-spec` remains a pure typed-contract and vocabulary registry with no executable devtools content.
+- `sourceos-devtools` consumes contracts and vocabulary from `sourceos-spec` but does not redefine them.
+- Agents and tooling can resolve the devtools repo via `urn:sourceos:repo:SourceOS-Linux:sourceos-devtools` using the canonical topology descriptor.
+
+## References
+
+- [GitHub issue #70: Admin task: create and bootstrap sourceos-devtools repo](https://github.com/SourceOS-Linux/sourceos-spec/issues/70)
+- `examples/repo-descriptor.sourceos-devtools.jsonld` — canonical topology entry
+- `semantic/repo-ontology.jsonld` — `roleDeveloperToolchain` definition
diff --git a/examples/repo-descriptor.sourceos-devtools.jsonld b/examples/repo-descriptor.sourceos-devtools.jsonld
new file mode 100644
index 0000000..2a78caa
--- /dev/null
+++ b/examples/repo-descriptor.sourceos-devtools.jsonld
@@ -0,0 +1,25 @@
+{
+  "@context": "../semantic/context.jsonld",
+  "@id": "urn:sourceos:repo:SourceOS-Linux:sourceos-devtools",
+  "@type": ["RepoDescriptor", "Repository"],
+  "name": "sourceos-devtools",
+  "description": "SourceOS Developer Tools: Linux-native developer tooling, lab profile selection, Nix/devshell orchestration, release tooling, local AI governance utilities, and SourceOS workstation bootstrap.",
+  "repositoryFullName": "SourceOS-Linux/sourceos-devtools",
+  "repoUrl": "https://github.com/SourceOS-Linux/sourceos-devtools",
+  "organization": "SourceOS-Linux",
+  "defaultBranch": "main",
+  "semanticDescriptorVersion": "0.1.0",
+  "topologyRole": "roleDeveloperToolchain",
+  "connectsTo": [
+    "urn:sourceos:repo:SourceOS-Linux:sourceos-spec",
+    "urn:sourceos:repo:SociOS-Linux:agentos-spine",
+    "urn:sourceos:repo:SociOS-Linux:SourceOS"
+  ],
+  "consumesVocabularyFrom": "urn:sourceos:repo:SourceOS-Linux:sourceos-spec",
+  "notThisRepo": [
+    "typed-contract registry",
+    "immutable OS substrate",
+    "public docs site",
+    "platform workspace controller"
+  ]
+}
diff --git a/examples/repo-descriptor.sourceos-spec.jsonld b/examples/repo-descriptor.sourceos-spec.jsonld
index 7a23f24..f040d87 100644
--- a/examples/repo-descriptor.sourceos-spec.jsonld
+++ b/examples/repo-descriptor.sourceos-spec.jsonld
@@ -16,7 +16,8 @@
     "urn:sourceos:repo:SociOS-Linux:SourceOS",
     "urn:sourceos:repo:SociOS-Linux:socios",
     "urn:sourceos:repo:SocioProphet:sociosphere",
-    "urn:sourceos:repo:SociOS-Linux:socioslinux-web"
+    "urn:sourceos:repo:SociOS-Linux:socioslinux-web",
+    "urn:sourceos:repo:SourceOS-Linux:sourceos-devtools"
   ],
   "consumesVocabularyFrom": "urn:sourceos:repo:SourceOS-Linux:sourceos-spec",
   "notThisRepo": [
diff --git a/semantic/context.jsonld b/semantic/context.jsonld
index d0e4dee..31d4f12 100644
--- a/semantic/context.jsonld
+++ b/semantic/context.jsonld
@@ -29,6 +29,7 @@
     "roleAutomationCommons": "srcos:role/AutomationCommons",
     "roleOSSubstrate": "srcos:role/OSSubstrate",
     "rolePublicDocsSurface": "srcos:role/PublicDocsSurface",
-    "roleStarterScaffold": "srcos:role/StarterScaffold"
+    "roleStarterScaffold": "srcos:role/StarterScaffold",
+    "roleDeveloperToolchain": "srcos:role/DeveloperToolchain"
   }
 }
diff --git a/semantic/repo-ontology.jsonld b/semantic/repo-ontology.jsonld
index 55ed947..3fbacb5 100644
--- a/semantic/repo-ontology.jsonld
+++ b/semantic/repo-ontology.jsonld
@@ -48,6 +48,12 @@
       "@type": "TopologyRole",
       "name": "Starter Scaffold",
       "description": "Bootstrap or starter repository for interfaces, policy, integration, or registry scaffolding. Not the canonical controller or spec lane."
+    },
+    {
+      "@id": "roleDeveloperToolchain",
+      "@type": "TopologyRole",
+      "name": "Developer Toolchain",
+      "description": "Linux-native developer tooling home: Nix/devshell orchestration, NLBoot/operator tooling, lab profile selection, release tooling, local AI governance utilities, and SourceOS workstation bootstrap."
     }
   ]
 }
diff --git a/semantic/repo.jsonld b/semantic/repo.jsonld
index 947e412..c24dd16 100644
--- a/semantic/repo.jsonld
+++ b/semantic/repo.jsonld
@@ -16,7 +16,8 @@
     "urn:sourceos:repo:SociOS-Linux:SourceOS",
     "urn:sourceos:repo:SociOS-Linux:socios",
     "urn:sourceos:repo:SocioProphet:sociosphere",
-    "urn:sourceos:repo:SociOS-Linux:socioslinux-web"
+    "urn:sourceos:repo:SociOS-Linux:socioslinux-web",
+    "urn:sourceos:repo:SourceOS-Linux:sourceos-devtools"
   ],
   "consumesVocabularyFrom": "urn:sourceos:repo:SourceOS-Linux:sourceos-spec",
   "notThisRepo": [