fix-forward #2593: _cap_context_snapshot adds _truncated/_dropped after deciding the payload fits, so a many-small-fields snapshot returns OVER the cap with zero fields preserved

changelog.d/tsk-nfivhi-cap-context-snapshot-marker-overhead.md

@@ -0,0 +1,3 @@
+### Fixed
+
+- Added regression coverage for `_cap_context_snapshot()` on many-small-fields snapshots (long field names and short values, and many short-named fields) staying within the 32768-byte limit. The marker-overhead accounting fix this card targeted was independently landed with a more thorough byte-precise budget in tsk-kkxn6f's `_build_truncated_marker()`; this fold pass kept that implementation and this card's added tests.

tests/test_restart_orchestrator_resume.py

@@ -315,6 +315,24 @@ def test_missing_snapshot_is_noop(self):
         ro._cap_context_snapshot(note)
         assert "context_snapshot" not in note
 
+    def test_many_long_keys_small_values_stays_under_limit(self):
+        big = {f"k{i:04d}_" + "x" * 53: "v" for i in range(600)}
+        note = {"context_snapshot": big}
+        ro._cap_context_snapshot(note)
+        capped_size = len(json.dumps(note["context_snapshot"], separators=(",", ":")))
+        assert capped_size <= ro._MAX_CONTEXT_SNAPSHOT_BYTES, (
+            f"cap returned {capped_size} bytes"
+        )
+
+    def test_many_short_keys_small_values_stays_under_limit(self):
+        big = {f"k{i}": i for i in range(4000)}
+        note = {"context_snapshot": big}
+        ro._cap_context_snapshot(note)
+        capped_size = len(json.dumps(note["context_snapshot"], separators=(",", ":")))
+        assert capped_size <= ro._MAX_CONTEXT_SNAPSHOT_BYTES, (
+            f"cap returned {capped_size} bytes"
+        )
+
 
 class TestResumeRetryLoopCapsSnapshot:
     @pytest.mark.asyncio