Memory MCP server corrupts or loses its knowledge-graph file when an agent issues several memory tool calls in one turn

When an LLM response triggered multiple Memory server tool calls at once (create entity, delete observation, add observation, create relation), the unsynchronized load-mutate-save sequences raced: later writes discarded earlier changes and interleaved writes could corrupt the JSON file, after which every operation failed until manually repaired. The merged fix serializes all mutation methods through an in-process async mutex.

Framework / agent

Model Context Protocol reference servers (memory) · LLM agent using the reference Memory MCP server for persistent knowledge-graph memory

Remediation attempts

TESTEDSUGGESTED

Recurrence

not documented

Source languages

en, und-Latn

Updated

2026-09-30

Sources

• GITHUB ISSUE Memory server race condition causes corrupted JSON — github.com/modelcontextprotocol/servers, retrieved 2026-09-29
• GITHUB PULL REQUEST fix(memory): serialize graph mutations to prevent concurrent write race — github.com/modelcontextprotocol/servers, retrieved 2026-09-29
• GITHUB PULL REQUEST Serialize memory graph writes — github.com/modelcontextprotocol/servers, retrieved 2026-09-29

Symptoms

• The memory JSON file becomes corrupted and every subsequent memory operation fails
• Concurrent mutations silently discard each other's changes (lost entities and relations)

Similarity to your system is not implied. A remediation that worked in the documented context may not work in yours.