diff --git a/loopx/control_plane/collaboration/inbox_read.ts b/loopx/control_plane/collaboration/inbox_read.ts
index cace31ba76..ada656aed9 100644
--- a/loopx/control_plane/collaboration/inbox_read.ts
+++ b/loopx/control_plane/collaboration/inbox_read.ts
@@ -55,11 +55,21 @@ function readRecord(path: string): JsonObject {
   try {
     const stat = fstatSync(fd);
     if (!stat.isFile()) fail("invalid manager context record");
-    if (stat.size > 128_000) fail("manager context record too large");
-    const buffer = Buffer.alloc(128_001);
+    const limit = 128_000;
+    if (stat.size > limit) fail("manager context record too large");
+    // Most receipts are small. Read one byte past the observed size so an
+    // in-place append still gets the same bounded read through EOF.
+    let buffer = Buffer.alloc(stat.size + 1);
     let size = 0, count: number;
-    while (size < buffer.length && (count = readSync(fd, buffer, size, buffer.length - size, null)) > 0) size += count;
-    if (size > 128_000) fail("manager context record too large");
+    while ((count = readSync(fd, buffer, size, buffer.length - size, null)) > 0) {
+      size += count;
+      if (size > limit) fail("manager context record too large");
+      if (size === buffer.length) {
+        const expanded = Buffer.alloc(limit + 1);
+        buffer.copy(expanded);
+        buffer = expanded;
+      }
+    }
     const bytes = buffer.subarray(0, size);
     let parsed: unknown;
     try {
diff --git a/tests/control_plane_ts/inbox_read_transaction.test.ts b/tests/control_plane_ts/inbox_read_transaction.test.ts
index c9ea35acf2..64023d378e 100644
--- a/tests/control_plane_ts/inbox_read_transaction.test.ts
+++ b/tests/control_plane_ts/inbox_read_transaction.test.ts
@@ -141,6 +141,15 @@ for (const bytes of [Buffer.from("\ufeff{}"), Buffer.from([0xff]), Buffer.alloc(
   });
 }
 
+test("a valid record at the byte limit retains its complete content", async t => {
+  const f = fixture(t), request = f.publish(1);
+  const path = join(f.folder, request.request_id + ".json");
+  const original = readFileSync(path);
+  writeFileSync(path, Buffer.concat([original, Buffer.alloc(128_000 - original.length, 32)]));
+  const result = (await f.call("pending", {request_id: request.request_id})).result as JsonObject;
+  assert.equal((result.items as JsonObject[])[0].message, request.message);
+});
+
 test("malformed receipts retain the request and recovery advice", async t => {
   const f = fixture(t), request = f.publish(1);
   mkdirSync(join(f.base, "decisions"));