diff --git a/packages/paperclip-runner/runner/DURABLE_TRANSPORT.md b/packages/paperclip-runner/runner/DURABLE_TRANSPORT.md
index ca4697d8c46..ab44e35d6e1 100644
--- a/packages/paperclip-runner/runner/DURABLE_TRANSPORT.md
+++ b/packages/paperclip-runner/runner/DURABLE_TRANSPORT.md
@@ -179,6 +179,18 @@ validate the exact Runner identity and acknowledged sequence cut.
 
 ### Hosted park and reclaim loop
 
+On Unix builds, `paperclip-runnerd --build-metadata` reports
+`privateHostControlVersion: 1` for the existing private fd 4 protocol below.
+Other builds omit this field. A consumer must verify the selected executable's
+identity and require the exact supported version before using this channel;
+an absent or unknown version does not establish support. Recovery and warm-task
+versions do not establish it either. Ordinary artifact admission can ignore this
+optional field.
+
+This field describes protocol support only. It does not mean a provider is ready
+to park or that a host implements the public `releaseResumeVersion` contract.
+Runner readiness checks and host sleep/wake qualification are still required.
+
 A trusted Launcher may pass a connected Unix stream at fd 4 and start durable
 listener mode with `--host-control-fd 4`. The descriptor is close-on-exec before
 provider startup. The private channel accepts the `park`, `claim`, and `retire`
diff --git a/packages/paperclip-runner/runner/crates/runner-core/src/bin/paperclip-runnerd.rs b/packages/paperclip-runner/runner/crates/runner-core/src/bin/paperclip-runnerd.rs
index 4d3c6da791c..895de31d866 100644
--- a/packages/paperclip-runner/runner/crates/runner-core/src/bin/paperclip-runnerd.rs
+++ b/packages/paperclip-runner/runner/crates/runner-core/src/bin/paperclip-runnerd.rs
@@ -115,7 +115,7 @@ fn install_crypto_provider() {
 }
 
 fn build_metadata() -> serde_json::Value {
-    json!({
+    let mut metadata = json!({
         "schema": RUNNERD_BUILD_METADATA_SCHEMA,
         "binaryName": "paperclip-runnerd",
         "packageName": "@paperclipai/paperclip-runner",
@@ -133,7 +133,11 @@ fn build_metadata() -> serde_json::Value {
             "maximumVersion": 2
         },
         "prpTransportModes": ["dial_ws_loopback", "dial_wss", "listen_ws"]
-    })
+    });
+    if cfg!(unix) {
+        metadata["privateHostControlVersion"] = json!(1);
+    }
+    metadata
 }
 
 // The publisher seals image installations. Check only path metadata at startup;
@@ -726,6 +730,12 @@ mod tests {
         assert_eq!(metadata["acpxRecoveryIntegrityVersion"], 1);
         assert!(metadata.get("acpxSourceRecoveryVersion").is_none());
         assert!(metadata.get("hostedParkingVersion").is_none());
+        assert!(metadata.get("releaseResumeVersion").is_none());
+        if cfg!(unix) {
+            assert_eq!(metadata["privateHostControlVersion"], 1);
+        } else {
+            assert!(metadata.get("privateHostControlVersion").is_none());
+        }
         assert_eq!(metadata["schema"], RUNNERD_BUILD_METADATA_SCHEMA);
         assert_eq!(metadata["binaryContractVersion"], 2);
         assert_eq!(
diff --git a/packages/paperclip-runner/runner/crates/runner-core/tests/local_runner.rs b/packages/paperclip-runner/runner/crates/runner-core/tests/local_runner.rs
index e71ef5778a5..eb2eacbf6bd 100644
--- a/packages/paperclip-runner/runner/crates/runner-core/tests/local_runner.rs
+++ b/packages/paperclip-runner/runner/crates/runner-core/tests/local_runner.rs
@@ -79,6 +79,13 @@ fn runnerd_startup_reports_build_metadata_without_panicking() {
     let metadata: Value =
         serde_json::from_slice(&output.stdout).expect("build metadata should be valid JSON");
     assert_eq!(metadata["binaryName"], "paperclip-runnerd");
+    if cfg!(unix) {
+        assert_eq!(metadata["privateHostControlVersion"], 1);
+    } else {
+        assert!(metadata.get("privateHostControlVersion").is_none());
+    }
+    assert!(metadata.get("hostedParkingVersion").is_none());
+    assert!(metadata.get("releaseResumeVersion").is_none());
 }
 
 #[test]
diff --git a/packages/paperclip-runner/src/evals/runnerd-artifact.test.ts b/packages/paperclip-runner/src/evals/runnerd-artifact.test.ts
index 4463571f3cf..8f208d99e02 100644
--- a/packages/paperclip-runner/src/evals/runnerd-artifact.test.ts
+++ b/packages/paperclip-runner/src/evals/runnerd-artifact.test.ts
@@ -28,6 +28,11 @@ describe("runnerd artifact metadata", () => {
     expect(parsePaperclipRunnerdBuildMetadata(valid)).toEqual(valid);
   });
 
+  it("accepts private host-control metadata without changing ordinary artifact admission", () => {
+    expect(parsePaperclipRunnerdBuildMetadata({ ...valid, privateHostControlVersion: 1 }))
+      .toEqual(valid);
+  });
+
   it("rejects an unknown binary metadata schema", () => {
     expect(() => parsePaperclipRunnerdBuildMetadata({ ...valid, schema: "runnerd/v2" }))
       .toThrow(PaperclipRunnerdArtifactError);