Fireweed: an MCP memory server whose write tool can refuse the model
External-Fee-8920 · reddit · 2026-08-25
Fireweed is a zero-dependency MCP memory server that inverts the usual design: the model doesn't decide what gets remembered — it proposes, and a deterministic gate (pure code, nothing you can talk around) decides admission.
Five tools:
- remember: admits a claim only if the quoted evidence actually supports it, with typed refusals (e.g., assertsmorethanevidence);
- recall: returns grounded claims with byte-range receipts, abstaining and naming the gap when it can't ground;
- verifyreceipts: re-hashes sources and re-slices ranges — tamper-evident;
- forget: erasure with exact closure and a signed certificate, bystanders survive;
- exportmemory: portable open-format export.
The author candidly notes the code is two days old, and self-installed it like a stranger the night before posting — immediately catching the worst bug a memory server can have: remember reporting ADMITTED while silently dropping the write, because the verb firewall matched by spelling (-s/-ed/-ing) and had never seen "wrote" or "went".
Install: claude mcp add fireweed -- uvx fireweed-mcp. Core thesis: a memory that can be caught lying is worth more than one that's confidently smooth.
Related event: Fireweed: Deterministic Gate Keeps AI Agent Memory Hallucination-Free(3 posts)→
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