---
id: MEM-12
family: GR-MEM
level: extended
profiles: [storage-api, runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-mem/mem-12
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# MEM-12 — Concurrent buffer appends are serialized, and never fatal

*GR-MEM (Part I) · level: extended · profiles: storage-api, runtime · added in 1.0*

Two branches appending at once would each read the buffer before the other's turn and write back a version missing it. Serializing the read-modify-write prevents that, but losing a turn is worse than a rare interleave.

## The rule

> **Normative.** This is the rule.
>
> 1. The read-modify-write of a conversation buffer is serialized per storage scope (scope, scope identifier and key together), so concurrent appends queue instead of overwriting one another.
>
> 2. The wait is bounded: an append that still cannot take its turn proceeds unserialized and emits a warning rather than failing or discarding the turn.
>
> 3. Serialization taken is always released.
>
> 4. Nothing more is claimed: not storage-level atomicity, and no protection against a writer that does not go through this path.

## Related rules

- Names: MEM-7

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.