feat(core): enforce prior read before Edit / WriteFile mutates a file

packages/core/src/services/fileReadCache.test.ts

@@ -213,11 +213,19 @@ describe('FileReadCache', () => {
       expect(entry.lastWriteAt).toBe(Date.now());
     });
 
-    it('does not set lastReadAt or flip lastReadWasFull', () => {
+    it('seeds read metadata when recording a write on a brand-new entry', () => {
+      // The model authored the bytes it just wrote — for the purposes
+      // of prior-read enforcement on the *next* Edit, that counts as
+      // having seen the full text content. Without this seeding a
+      // create→edit→edit chain would reject the second edit because
+      // lastReadWasFull / lastReadCacheable would still be unset on
+      // the entry recordWrite created.
       const cache = new FileReadCache();
       const entry = cache.recordWrite('/x/foo.ts', makeStats());
-      expect(entry.lastReadAt).toBeUndefined();
-      expect(entry.lastReadWasFull).toBe(false);
+      expect(entry.lastReadAt).toBeDefined();
+      expect(entry.lastReadAt).toBe(entry.lastWriteAt);
+      expect(entry.lastReadWasFull).toBe(true);
+      expect(entry.lastReadCacheable).toBe(true);
     });
 
     it('refreshes mtime+size so a follow-up Edit sees fresh', () => {

packages/core/src/services/fileReadCache.ts

@@ -118,10 +118,25 @@ export class FileReadCache {
    * differ from any prior Read snapshot, so we refresh the cached
    * fingerprint to the post-write Stats; otherwise the next Edit would
    * see its own write as a "stale" external change.
+   *
+   * If the entry has never been Read in this session (i.e. this is a
+   * fresh file just created by Edit / WriteFile), populate the read
+   * metadata as well: the model authored the bytes it just wrote, so
+   * for the purposes of prior-read enforcement it has effectively
+   * "seen" the full text content. Without this, a create→edit→edit
+   * chain would be rejected on the second edit because
+   * `lastReadAt`/`lastReadWasFull`/`lastReadCacheable` would still be
+   * undefined.
    */
   recordWrite(absPath: string, stats: Stats): FileReadEntry {
     const entry = this.upsert(absPath, stats);
-    entry.lastWriteAt = Date.now();
+    const now = Date.now();
+    entry.lastWriteAt = now;
+    if (entry.lastReadAt === undefined) {
+      entry.lastReadAt = now;
+      entry.lastReadWasFull = true;
+      entry.lastReadCacheable = true;
+    }
     return entry;
   }