diff --git a/compiler/src/generators/protobuf.ts b/compiler/src/generators/protobuf.ts
index 4fb895a..18e5246 100644
--- a/compiler/src/generators/protobuf.ts
+++ b/compiler/src/generators/protobuf.ts
@@ -22,7 +22,7 @@
  * existing determinism claim.
  */
 
-import { AST, SpeckNode, MemberNode, StateNode, EventNode, InterfaceNode, TypeExpr, ServiceNode } from '../parser.js';
+import { AST, SpeckNode, MemberNode, StateNode, EventNode, InterfaceNode, TypeExpr, ServiceNode, TransitionNode, OneofNode } from '../parser.js';
 import fs from 'fs';
 import path from 'path';
 
@@ -270,8 +270,8 @@ function emitSpeck(speck: SpeckNode, packageName?: string): string {
       let protoType = speckTypeToProto(v.typeExpr.name || '');
       if (v.typeExpr.type === 'map' && v.typeExpr.keyType && v.typeExpr.valueType) {
         const k = speckTypeToProto(v.typeExpr.keyType.name || 'string');
-        const val = speckTypeToProto(v.typeExpr.valueType.name || 'bytes');
-        protoType = `map<${k}, ${val}>`;
+        const v2 = speckTypeToProto(v.typeExpr.valueType.name || 'bytes');
+        protoType = `map<${k}, ${v2}>`;
       } else if (v.typeExpr.type === 'list' && v.typeExpr.elementType) {
         const inner = speckTypeToProto(v.typeExpr.elementType.name || 'string');
         protoType = `repeated ${inner}`;
@@ -282,6 +282,40 @@ function emitSpeck(speck: SpeckNode, packageName?: string): string {
     lines.push('');
   }
 
+  // Cycle 64: emit TransitionNode messages. A `transition Name { ... }`
+  // block produces a proto message with the regular fields plus an inline
+  // `oneof payload { ... }` block, whose variants are pulled from a
+  // sibling `oneof <Name> { ... }` block referenced by `payload: <Name>`.
+  // Field numbers are assigned starting at 1; the oneof variants use
+  // 10, 11, 12, ... (proto convention: leave 1-15 for the most stable
+  // fields so the wire format is forward-compatible).
+  const transitionNodes = members.filter(m => m.type === 'transition') as TransitionNode[];
+  const oneofNodes = members.filter(m => m.type === 'oneof') as OneofNode[];
+  for (const t of transitionNodes) {
+    lines.push(`message ${t.name} {`);
+    const fieldNums = assignFieldNumbers(t.fields);
+    for (const f of t.fields) {
+      const num = fieldNums.get(f.name) || 1;
+      const protoType = speckTypeToProto(f.type.name || '');
+      lines.push(`  ${protoType} ${snakeCase(f.name)} = ${num};`);
+    }
+    if (t.payloadOneof) {
+      const oneof = oneofNodes.find(o => o.name === t.payloadOneof);
+      if (oneof) {
+        lines.push('  oneof payload {');
+        oneof.variants.forEach((v, i) => {
+          // Reference the suffixed message name if event_suffix is set,
+          // so the oneof variants match what the consumer Go code expects.
+          const variantType = speck.eventSuffix ? v.typeName + speck.eventSuffix : v.typeName;
+          lines.push(`    ${variantType} ${v.fieldName} = ${i + 10};`);
+        });
+        lines.push('  }');
+      }
+    }
+    lines.push('}');
+    lines.push('');
+  }
+
   // ─── Service (RPC surface) ──────────────────────────────────
   // ServiceNode members emit proto3 service blocks. These map directly to
   // gRPC and ConnectRPC service definitions; buf generate + protoc-gen-go