diff --git a/package-lock.json b/package-lock.json
index 0742559..a0a2aed 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@clawnify/clawflow",
-  "version": "0.9.2",
+  "version": "0.9.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@clawnify/clawflow",
-      "version": "0.9.2",
+      "version": "0.9.4",
       "license": "MIT",
       "devDependencies": {
         "@types/node": "^25.5.0",
diff --git a/package.json b/package.json
index 6576411..aa034b2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@clawnify/clawflow",
-  "version": "0.9.4",
+  "version": "0.9.5",
   "description": "The n8n for agents. A declarative, AI-native workflow format that agents can read, write, and run.",
   "type": "module",
   "main": "./dist/index.js",
diff --git a/src/core/validate.ts b/src/core/validate.ts
index 4e09133..b2dd1db 100644
--- a/src/core/validate.ts
+++ b/src/core/validate.ts
@@ -153,6 +153,25 @@ function validateNodes(
   }
 }
 
+// ---- Allowed keys per node type (BaseNode keys are always allowed) ----------------
+
+const BASE_KEYS = new Set(["name", "do", "output", "retry", "timeout"]);
+
+const ALLOWED_KEYS: Record<string, Set<string>> = {
+  ai: new Set([...BASE_KEYS, "prompt", "input", "schema", "model", "temperature", "maxTokens", "attachments"]),
+  agent: new Set([...BASE_KEYS, "task", "input", "tools", "agentId"]),
+  branch: new Set([...BASE_KEYS, "on", "paths", "default"]),
+  condition: new Set([...BASE_KEYS, "if", "then", "else"]),
+  loop: new Set([...BASE_KEYS, "over", "as", "nodes"]),
+  parallel: new Set([...BASE_KEYS, "nodes", "mode"]),
+  http: new Set([...BASE_KEYS, "url", "method", "body", "headers"]),
+  memory: new Set([...BASE_KEYS, "action", "key", "value"]),
+  wait: new Set([...BASE_KEYS, "for", "prompt", "preview", "event"]),
+  sleep: new Set([...BASE_KEYS, "duration"]),
+  code: new Set([...BASE_KEYS, "run", "input"]),
+  exec: new Set([...BASE_KEYS, "command", "cwd"]),
+};
+
 /** Validate required fields per node type */
 function validateNodeFields(node: FlowNode, errors: ValidationError[]): void {
   const e = (field: string, msg: string) =>
@@ -164,6 +183,16 @@ function validateNodeFields(node: FlowNode, errors: ValidationError[]): void {
     return;
   }
 
+  // Check for unknown keys
+  const allowed = ALLOWED_KEYS[nodeType];
+  if (allowed) {
+    for (const key of Object.keys(node)) {
+      if (!allowed.has(key)) {
+        e(key, `Unknown field "${key}" on ${nodeType} node "${node.name}"`);
+      }
+    }
+  }
+
   switch (nodeType) {
     case "ai": {
       const n = node as AiNode;
diff --git a/tests/core.test.ts b/tests/core.test.ts
index 7345588..614cedc 100644
--- a/tests/core.test.ts
+++ b/tests/core.test.ts
@@ -1166,6 +1166,38 @@ describe("validateFlow", () => {
     assert.equal(result.ok, true);
   });
 
+  it("catches branch path placed as sibling of paths", () => {
+    const flow: FlowDefinition = {
+      flow: "misplaced-branch-path",
+      nodes: [
+        { name: "classify", do: "code" as const, run: "'densita'", output: "order_type" },
+        {
+          name: "route", do: "branch" as const, on: "order_type",
+          paths: {
+            densita: [{ name: "d1", do: "code" as const, run: "'ok'", output: "x" }],
+          },
+          // This is the bug: diametri is a sibling of paths, not inside it
+          diametri: [{ name: "d2", do: "code" as const, run: "'ok'", output: "y" }],
+        } as any,
+      ],
+    };
+    const result = validateFlow(flow);
+    assert.equal(result.ok, false);
+    assert.ok(result.errors.some((e) => e.message.includes("Unknown field \"diametri\"")));
+  });
+
+  it("catches unknown fields on any node type", () => {
+    const flow: FlowDefinition = {
+      flow: "unknown-field",
+      nodes: [
+        { name: "bad", do: "ai" as const, prompt: "hello", bogus: true } as any,
+      ],
+    };
+    const result = validateFlow(flow);
+    assert.equal(result.ok, false);
+    assert.ok(result.errors.some((e) => e.message.includes("Unknown field \"bogus\"")));
+  });
+
   it("catches unknown node type", () => {
     const flow: FlowDefinition = {
       flow: "unknown-type",