Property strings with U+0000 or a lone surrogate pass the add-memories request and are refused by some stores after others have written them #1793

What happens

Measured on main at ad8ff24, one value at a time through each store's own code, on SQLite and PostgreSQL where a store supports both, with Qdrant 1.17.0 (REST and gRPC) and Milvus 2.6.24 and Milvus Lite. The value is a string that becomes a property value: a metadata key or value, producer, produced_for, or role of a message, which are producer_id, producer_role, produced_for_id, and metadata of an EpisodeEntry.

Semantic memory receives the value inside a set id, for producer and for a metadata value whose key a set type names.

The request accepts both: JSON "\u0000" decodes to U+0000, and the route's JSON decoding turns "\ud800" into a lone surrogate. Through POST /api/v2/memories with the real stores (episode store, segment store, and semantic storage on PostgreSQL, and SQLiteVectorStore):

• metadata {"k": "a\u0000b"} or {"k": "a\ud800b"}: 500, with the episode recorded in semantic memory's three sets and in no other store;
• producer "a\u0000b": 500, nothing written;
• with the same stores on SQLite, all three: 200, stored everywhere.

Why

• MemoryMessage types these fields as str (packages/common/src/memmachine_common/api/spec.py:458-477), and EpisodeEntry does too (packages/server/src/memmachine_server/common/episode_store/episode_model.py:29-35).
• MemMachine.add_episodes writes the episode store, episodic memory, and semantic memory concurrently and raises the first failure once all of them return (packages/server/src/memmachine_server/main/memmachine.py:795-819), so the stores that keep the value have written it.
• PostgreSQL text and JSONB refuse U+0000, and UTF-8 encoding refuses a lone surrogate.

Expected

The request refuses such a string with 422 before any store writes, and building an EpisodeEntry with one raises.

Fix

#1792 types these fields as PropertyStr, which refuses a string with U+0000 or a surrogate code point.

🤖 Written by Claude Code (Claude Opus 5.5) on behalf of @edwinyyyu.