diff --git a/tools/conformance/attach-plugin-witness.mjs b/tools/conformance/attach-plugin-witness.mjs
index 58faec0..c924a34 100644
--- a/tools/conformance/attach-plugin-witness.mjs
+++ b/tools/conformance/attach-plugin-witness.mjs
@@ -1,7 +1,7 @@
 import { mkdir, readFile, writeFile } from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import { validateSchemaSubset } from "../../runtimes/incubating/test-support/schema-subset.mjs";
+import { validateSchemaSubset } from "../lib/schema-subset.mjs";
 
 const [witnessArgument, exportArgument] = process.argv.slice(2);
 if (!witnessArgument || !exportArgument) {
@@ -12,8 +12,9 @@ const witnessPath = path.resolve(witnessArgument);
 const exportDirectory = path.resolve(exportArgument);
 const indexPath = path.join(exportDirectory, "index.json");
 const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
+const kernelRoot = path.resolve(process.env.EVE_KERNEL_ROOT || "E:\\Projects\\Eve");
 const witness = parseJson(await readFile(witnessPath, "utf8"));
-const schema = parseJson(await readFile(path.join(repoRoot, "schemas/gamecult.eve.plugin_witness.v1.schema.json"), "utf8"));
+const schema = parseJson(await readFile(path.join(kernelRoot, "schemas/gamecult.eve.plugin_witness.v1.schema.json"), "utf8"));
 const schemaErrors = validateSchemaSubset(schema, witness);
 if (schemaErrors.length) throw new Error(`Plugin witness schema errors: ${schemaErrors.join("; ")}`);
 
diff --git a/tools/conformance/attach-runtime-witness.mjs b/tools/conformance/attach-runtime-witness.mjs
index c42adad..e8c0a40 100644
--- a/tools/conformance/attach-runtime-witness.mjs
+++ b/tools/conformance/attach-runtime-witness.mjs
@@ -1,7 +1,7 @@
 import { copyFile, mkdir, readFile, writeFile } from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import { validateSchemaSubset } from "../../runtimes/incubating/test-support/schema-subset.mjs";
+import { validateSchemaSubset } from "../lib/schema-subset.mjs";
 
 const [witnessArgument, exportArgument] = process.argv.slice(2);
 if (!witnessArgument || !exportArgument) {
@@ -15,7 +15,8 @@ const indexPath = path.join(exportDirectory, "index.json");
 const witness = parseJson(await readFile(witnessPath, "utf8"));
 validateWitness(witness);
 const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
-const witnessSchema = parseJson(await readFile(path.join(repoRoot, "schemas/gamecult.eve.runtime_witness.v1.schema.json"), "utf8"));
+const kernelRoot = path.resolve(process.env.EVE_KERNEL_ROOT || "E:\\Projects\\Eve");
+const witnessSchema = parseJson(await readFile(path.join(kernelRoot, "schemas/gamecult.eve.runtime_witness.v1.schema.json"), "utf8"));
 const schemaErrors = validateSchemaSubset(witnessSchema, witness);
 if (schemaErrors.length) throw new Error(`Runtime witness schema errors: ${schemaErrors.join("; ")}`);
 
diff --git a/tools/lib/schema-subset.mjs b/tools/lib/schema-subset.mjs
new file mode 100644
index 0000000..5437df8
--- /dev/null
+++ b/tools/lib/schema-subset.mjs
@@ -0,0 +1,71 @@
+export function validateSchemaSubset(schema, value, pointer = "$", rootSchema = schema) {
+  const errors = [];
+  if (!schema || typeof schema !== "object") return errors;
+
+  if (schema.$ref) {
+    const resolved = resolveSchemaReference(rootSchema, schema.$ref);
+    return resolved
+      ? validateSchemaSubset(resolved, value, pointer, rootSchema)
+      : [`${pointer}:unresolved-ref:${schema.$ref}`];
+  }
+
+  if (schema.const !== undefined && value !== schema.const) {
+    errors.push(`${pointer}:const:${schema.const}`);
+  }
+  if (schema.enum && !schema.enum.includes(value)) {
+    errors.push(`${pointer}:enum:${schema.enum.join("|")}`);
+  }
+  if (schema.type && !matchesSchemaType(value, schema.type)) {
+    errors.push(`${pointer}:type:${schema.type}`);
+    return errors;
+  }
+  if (schema.minLength !== undefined && typeof value === "string" && value.length < schema.minLength) {
+    errors.push(`${pointer}:minLength:${schema.minLength}`);
+  }
+  if (schema.minItems !== undefined && Array.isArray(value) && value.length < schema.minItems) {
+    errors.push(`${pointer}:minItems:${schema.minItems}`);
+  }
+  if (schema.required && value && typeof value === "object" && !Array.isArray(value)) {
+    for (const key of schema.required) {
+      if (value[key] === undefined) errors.push(`${pointer}.${key}:required`);
+    }
+  }
+  if (schema.properties && value && typeof value === "object" && !Array.isArray(value)) {
+    for (const [key, childSchema] of Object.entries(schema.properties)) {
+      if (value[key] !== undefined) {
+        errors.push(...validateSchemaSubset(childSchema, value[key], `${pointer}.${key}`, rootSchema));
+      }
+    }
+  }
+  if (schema.items && Array.isArray(value)) {
+    value.forEach((item, index) => {
+      errors.push(...validateSchemaSubset(schema.items, item, `${pointer}[${index}]`, rootSchema));
+    });
+  }
+  return errors;
+}
+
+function resolveSchemaReference(rootSchema, reference) {
+  if (!reference.startsWith("#/")) return null;
+  return reference.slice(2).split("/").reduce((current, segment) => {
+    if (!current || typeof current !== "object") return null;
+    return current[segment.replaceAll("~1", "/").replaceAll("~0", "~")];
+  }, rootSchema);
+}
+
+function matchesSchemaType(value, type) {
+  switch (type) {
+    case "array":
+      return Array.isArray(value);
+    case "object":
+      return value !== null && typeof value === "object" && !Array.isArray(value);
+    case "string":
+      return typeof value === "string";
+    case "number":
+      return typeof value === "number";
+    case "boolean":
+      return typeof value === "boolean";
+    default:
+      return true;
+  }
+}