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.

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Fireweed: an MCP memory server whose write tool can refuse the model

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