I built persistent AI memory for Claude on Cloudflare’s free tier

Posted by DevegygiebyOL

Every Claude session starts fresh. You copy context, explain your setup, reintroduce your project, and then do it all over again the next day. I got tired of this and created a solution.

second-brain-cloudflare is a self-hosted MCP server that provides Claude, ChatGPT, Cursor, and any MCP-compatible client with persistent memory across sessions. It operates entirely on Cloudflare’s free tier. Here’s how it works.

The stack

  • Cloudflare Workers: MCP server, REST API, and web UI, all from one wrangler deploy
  • D1 (SQLite): stores entry content, tags, source, timestamps, and vector chunk IDs
  • Vectorize: the vector index (bge-small-en-v1.5, 384 dimensions)
  • Workers AI: bge-small-en-v1.5 for embeddings,
    @cf/meta/llama-4-scout-17b-16e-instruct for web UI synthesis

One deployment. No external databases. No API keys needed beyond your Cloudflare account token.

Tag-based time-decay reranking

Pure vector similarity has a drawback. A memory from three months ago can outrank something you saved yesterday if it’s semantically closer. The solution is to fetch three times more candidates than needed (topK=5 pulls 15), then score each using a tag-aware half-life:

  • Tasks: 7-day half-life
  • Work: 3-month half-life
  • Context: 6-month half-life
  • Default: 30-day half-life

adjusted_score = cosine_similarity × e^(-age_in_days / half_life)

Duplicate detection

Before storing anything, embed the incoming content and query Vectorize for its nearest neighbor:

  • Score ≥ 95%: block
  • Score 85–94%: store with duplicate-candidate tag
  • Score < 85%: store normally

Without this step, Claude creates 20–30 nearly identical entries for the same decision.

Smart chunking

Long notes split at sentence ends, with a 200-character overlap. Each chunk receives its own vector. Chunk IDs are stored in D1, so forget() reliably removes all related vectors.

Temporal recall (v1.2.0)

Queries now support time limits:

  • recall(“API decisions”, after=”7 days ago”)
  • recall(“standup notes”, after=”2026-05-12″)
    Supports: “today”, “yesterday”, “last week”, “this month”, ISO dates, and epoch timestamps.

AI synthesis in the web UI

Queries flow through @cf/meta/llama-4-scout-17b-16e-instruct before being rendered. Answers stream in real time, with source memories that can be collapsed underneath. You’ll find Append and Forget buttons. This runs on your own Cloudflare account.

Why the free tier works

  • D1: 5GB storage, 5 million row reads per day
  • Vectorize: 5 million vectors, 30 million queried dimensions per month (adequate for team scale but fine for personal use)
  • Workers AI: 10,000 Neurons per day

Try it

Deploy: https://thesecondbrain.dev
GitHub: https://github.com/rahilp/second-brain-cloudflare

If this was helpful, please give it a star.