🔐 keep

Use a secret without holding it. An encrypted vault whose values are injected into the commands an agent runs, and redacted from everything that comes back. The agent works with ‹keep:GH_TOKEN›. The token itself never enters its context, its transcript, or anything that reads the transcript later.

Part of tools-for-agents. Zero dependencies: the Node standard library plus your OS keychain. CLI + MCP.

Why this exists

An agent that needs an API key today has one way to get it: read it. It runs cat .env or echo $TOKEN, or it asks you to paste the key into the chat. From that moment the value sits in the model's context. It also sits in the session transcript on disk (~/.claude/projects/*.jsonl), and every process that reads transcripts can see it: summarisers, search indexes, memory systems that dream sessions into long-term memory.

Measured on the machine this was built on, on the day it was built: the first keep scan --transcripts went through 7,335 transcript files (1.28 GB) in ten seconds and found a Firebase service-account private key. An agent had read the key out of a project's .env weeks earlier, and it had been in a transcript ever since.

keep closes that path. The agent names the secret, and keep hands the value to the program, never to the agent:

keep run --with GH_TOKEN -- gh api user
keep run -- curl -H 'Authorization: Bearer {{OPENAI_API_KEY}}' https://api.openai.com/v1/models

Anything the program prints goes through a redactor built from every kept value, and the agent reads ‹keep:OPENAI_API_KEY› wherever the value would have appeared.

Related MCP server: Keiko

Install

git clone https://github.com/tools-for-agents/keep.git && cd keep
node src/cli.js init                      # creates ~/.keep; the master key goes into the OS keychain
ln -s "$PWD/src/cli.js" ~/.local/bin/keep
claude mcp add keep --scope user -- node "$PWD/mcp/mcp-server.js"

Node 22+. Nothing to npm install.

For the person

keep set GH_TOKEN                     # typed hidden, never echoed, never in shell history
pbpaste | keep set OPENAI_API_KEY     # or piped
keep set DEPLOY_KEY --allow gh,fly    # only these programs may receive it
keep import .env                      # keep every KEY=value in a dotenv file (then delete the file)
keep list                             # names, policy, usage — and what agents have asked for
keep audit                            # every use: when, which names, which command, exit code
keep scan --transcripts               # has anything already leaked?
keep redact --patterns < in > out     # a filter: kept values and known key shapes → their names

keep redact is for the other tools that store what an agent wrote: a memory that dreams transcripts, a log shipper, a search index. ghost pipes every session through it before dreaming, so a key an agent once printed does not end up in long-term memory. With --patterns it also masks anything shaped like a well-known key, and it masks a private key as a whole block, body included, not just its BEGIN line.

guard: an agent does not read a secret file

keep lets an agent use a secret without holding it, but nothing stopped an agent from holding one anyway. The leak keep's first scan found was exactly that: an agent looking for a database URL ran grep -n "…\|PG\|…" backend/.env, the base64 body of a Firebase private key happened to contain "PG", and the key went into the transcript. There was no intent and no attack, just a grep.

keep guard --install      # a Claude Code PreToolUse hook (Bash|Read); keeps every other hook; backs settings up
keep guard --uninstall

A command that prints a secret file (cat, grep, head, sed, awk, git diff, base64 <, curl -d @.env, and so on) or a Read of one (.env*, *.pem, *.key, id_rsa, *service-account*.json, credentials.json, .netrc, .npmrc, …) is refused. The refusal carries the way forward, which an agent can take on its own with no human awake: keep import <file> stores every value without printing one, and keep run --with NAME -- … uses it. Nothing that doesn't print a secret is touched: templates (.env.example), cp .env.example .env, source .env && npm start, writing to a secret file, ls, mv, and keep's own commands.

For the agent (MCP)

No tool returns a value. That is the design, not a gap in it, and a test fails if a tool whose name looks like get, read, reveal or export ever appears.

What the redactor catches

A secret leaks in more shapes than its own. curl -v prints the Authorization header, and a Basic header is base64("user:" + secret): the secret's bytes, shifted by the username and written in another alphabet. So every value becomes a set of needles:

• the raw value, its JSON-escaped form and its URL-encoded form;

• base64 and base64url at all three byte alignments. base64 works in 3-byte groups, so how the secret encodes depends on how many bytes came before it. keep encodes it after 0, 1 and 2 bytes of padding and keeps only the characters that depend on the secret alone, which finds it inside any base64 string.

Output is streamed, and a value can be split across two chunks. The redactor holds back (longest needle − 1) characters at each boundary. A test splits a secret at every possible position and checks all of them.

Policy

keep set NAME --allow gh,curl restricts a secret to named programs. A restricted secret:

• cannot be handed to sh -c, node -e or python -c, which is the move an agent would make if it had been talked into exfiltrating the value;

• must be run by name (gh) and not by path (./gh), because a file named gh in the working directory is not the gh you meant.

Honest limits

keep is built against accidental exposure (a value in a context window, a transcript or a log) and it narrows misuse. It is not a boundary against a hostile process running as you, and it says so here rather than let you find out:

• Anything running as your user can ask the keychain for the master key, or read ~/.keep/master.key on the file backend, just as it could read your .env.

• A program you allow can do whatever it likes with the value. --allow curl lets curl send the key to any host.

• Redaction catches the shapes listed above. It does not catch a value that was reversed, hashed, split or re-encoded some other way before it was printed.

• keep status says which backend holds the master key. On Linux without secret-tool it is a 0600 file next to the vault, which is weaker, and keep prints that when the vault is created.

Files

Every file is 0600 in a 0700 directory, and each write goes to a temp file first and is renamed into place, so a crash never leaves half a vault.

Test

node --test               # 29 tests; the file backend, no keychain touched
node scripts/mutants.mjs  # breaks each safety property on purpose and demands the suite goes red

The agent toolkit

keep is the hold secrets leg of tools-for-agents — an operating system for agents. Nine zero-dependency, MCP-native tools that form one loop, with a self at its centre:

Reading this as an agent? /llms.txt is the map, and /tools.json hands you all 79 MCP tools — every name, every description, every install command — in one fetch, without cloning anything.

License

MIT