hush — keep API keys out of AI agent chats

He says nothing. He keeps your keys. It still works.

Scope honesty

hush protects the transcript: values never enter chat, tool outputs, or logs through its own channels. It does not protect against a hostile or prompt-injected agent with shell access — such an agent can cat the vault, tee stdin to disk, or transform values (base64/reverse) past literal redaction. If your adversary is the agent itself, you need OS-level isolation (keychain, daemon + socket auth), not hush. See SECURITY.md.

npm i -g --allow-scripts=hush-secrets hush-secrets  # installs binary + skill
hush set MY_API_KEY            # in YOUR terminal, never in chat
hush update                    # self-update via npm (needs npm on PATH)

Why

Pasting a secret into a harness chat leaves it in the transcript forever. hush separates the channels: the human loads values via TTY or the harness native prompt (over MCP), the agent only orchestrates names. No tool ever returns a value.

MCP (harness-agnostic: claude, opencode, cursor, codex)

hush serve exposes stdio with 4 tools: hush_check, hush_list, hush_need (asks for the value via elicitation and stores it), hush_run (injects + redacts). hush setup installs the skill, registers the server, and offers to add harness permission rules so the agent cannot read ~/.hush with its file tools (Claude Code, opencode v2) or runs hush without confirmation (Codex).

CLI

openssl rand -hex 24 | hush set WHATSAPP_VERIFY_TOKEN
hush check WHATSAPP_VERIFY_TOKEN META_APP_SECRET
hush stdin WHATSAPP_VERIFY_TOKEN -- npx wrangler secret put WHATSAPP_VERIFY_TOKEN
hush run --only META_APP_SECRET -- npx wrangler deploy
hush status

check and list print names only. run and stdin inject into the child process and redact output to [REDACTED].

hush run waits for the command to exit before printing, so redaction sees the whole output. To wrap a long-lived stdio process such as an MCP server, add --stream: output is forwarded line by line as it arrives (trade-offs in SECURITY.md).

"jira": {"type": "local", "command": ["hush", "run", "--stream", "--only", "JIRA_API_TOKEN", "--", "jira-mcp"]}

Where secrets live, and getting them back

Values are stored in ~/.hush/vault (file 0600, dir 0700), one NAME=value per line. There is intentionally no read-back over MCP and no get command — anything an agent can call ends up in its context.

To recover a value (rotation, migration, backup), use a real terminal:

hush export                  # prints all, NAME=value per line
hush export META_APP_SECRET  # prints one

export refuses to run unless stdout is a TTY, so a harness cannot capture it by piping (a pty is not proof of a human — see SECURITY.md). Back up the file itself (cp ~/.hush/vault …) for disaster recovery; wipe with rm -rf ~/.hush. See SECURITY.md and PRIVACY.md.

Notes

• Linux and macOS only (amd64/arm64). No Windows (TTY model).
• hush_run over MCP asks for human confirmation on every call and times out slow commands at 5 minutes, so don't start long-lived processes through it: run them in your terminal, or wrap an MCP server with hush run --stream in your harness config.
• Elicitation (native secret prompts) needs an interactive session; headless runs get the safe fallback (hush set in your terminal).

Verified harnesses

Harness	MCP tools	Elicitation UI
OpenCode	✅ verified live	interactive sessions
Codex	✅ via exec --approve-for-me (headless denies MCP by policy)	interactive sessions
Pi	✅ verified headless	interactive sessions
Claude Code	registration via claude mcp add (CLI needs login here)	interactive sessions
Cursor	~/.cursor/mcp.json (agent needs agent login here)	interactive sessions

Docs

SECURITY.md (threat model) · PRIVACY.md · CONTRIBUTING.md · CHANGELOG.md

Alternatives

	hush	psst	key-amnesia	akm	1Password MCP
Values hidden from transcript	✅	✅	✅	✅	✅
Hostile-agent isolation	❌ honest	❌	parcial	parcial	❌
MCP server	✅	❌	❌	❌	✅ (Codex only)
Load via native prompt (no chat)	✅ elicitation	❌	✅ popup	❌	✅
TTY-only export	✅	❌	❌	❌	❌
Vault corruption guard	✅	n/a	❌	❌	n/a
Harness-agnostic setup	✅	❌	parcial	❌	❌
Single binary, no runtime	✅ Go	✅	❌ Python	✅ Rust*	❌
Works offline / local-only	✅	✅	✅	✅	❌

*akm is macOS-only (Keychain). hush keeps a plain 0600 file so any dev can inspect, back up, and recover it with standard tools.

Development

make check   # generate + fmt + vet + test + build
make hook    # pre-commit (generate + fmt + vet + test)
./scripts/release.sh 0.2.0  # bump + tag (workflow publishes npm + release)

Conventional commits: feat:, fix:, chore:, docs:, refactor:, test:. SKILL.md is the single source of the skill; internal/setup/skill.md is regenerated with go generate ./... (a test enforces it).