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Sakur4

Your agent's compaction is the most expensive thing it does. Sakur4 makes it cheap, and makes it not lose anything.

Sakur4 is a local memory and context layer for long coding-agent sessions. It runs as a single Rust binary on your machine, speaks MCP over stdio or HTTP, and slots into whatever harness you already use — no cloud, no account, no telemetry.

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Why this exists

An agent that works for an hour does not run out of ability. It runs out of context, and the way it runs out is expensive:

What happens today	What it costs
The harness summarises the transcript	One inference call over the whole window — and the summary is lossy
The summary replaces the transcript	The provider's prompt cache is invalidated; the next turn re-prefills everything
A constraint stated forty turns ago	Silently gone, because nothing marked it as load-bearing
"What did we decide about auth?"	Unanswerable — the text is not there any more

Sakur4 addresses each of those separately rather than treating "compaction" as one problem.

The four ideas

1 · Cache-coherent compaction. Eviction cuts the transcript at a boundary the inference server's KV cache already holds, so the surviving prefix is a prefix of what the server has cached. The next turn is a longest-common-prefix match instead of a full re-prefill. The engine asks the backend what it can do and picks a strategy from the answer, rather than assuming.

2 · Two tracks, and a model can only write to one. A deterministic Symbolic Ledger records symbols, signatures and hashes extracted by parsing — no model output, so no hallucination. A Semantic Atlas holds model-written summaries, every one of which must anchor to a ledger fact, and whose staleness is resolved at read time by comparing hashes. A summary that contradicts the code is labelled [STALE] rather than trusted.

3 · Graduated eviction, not a cliff. Five tiers — Live → Masked → Referenced → Archived → Dropped — applied one step at a time, so a turn that must leave the window degrades instead of vanishing. Every plan ends in one of four reported verdicts, and context.plan_eviction shows the decision before it is taken.

4 · Pinned constraints survive everything. Anchors are rendered verbatim and are exempt from all compaction. If they ever cannot fit the budget, the operation refuses with an error rather than dropping one silently.

Install

curl -fsSL https://raw.githubusercontent.com/sc4rfurry/Sakur4/master/install.sh | sh

Detects your platform, verifies the archive checksum, installs the binary, and places the Agent Skill in ~/.agents/skills/. Refuses to install an archive it cannot verify.

Then print the configuration for your harness:

sakur4d config claude     # Claude Desktop / Claude Code
sakur4d config generic-stdio
sakur4d config hermes     # the default

Oh My Pi does not use config — it is a native extension, installed separately:

node integrations/omp-plugin/install.mjs

Where to go next

If you want to…	Read
Get it running in five minutes	Getting Started
Understand how eviction actually works	Architecture
See every tool and its arguments	Tool Reference
Wire it into a specific harness	Harnesses
Know what it costs and what it saves	Benchmarks
Run the checks yourself	Verification
Know what does not work yet	Limitations
Contribute	Contributing

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Honest status

Sakur4 is v0.1.0 and usable today. It is also a young project with a documented backlog, and the Limitations page is written to be read before you depend on it rather than after.

Three things worth knowing up front:

• If you batch tool calls, await each answer. MCP permits a server to process a queued batch in an arbitrary order, and Sakur4's tools are stateful. Sending a call and awaiting its reply — which every harness tested here does — is correct.
• One store holds one project. A project dimension exists for semantic memory and the transcript, but a session in a new directory starts with no history rather than someone else's.
• Nothing re-indexes automatically. sakur4d index after changing files; the repo map dates itself so you can see when it was built.

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_{Apache-2.0 · GitHub · Report an issue}