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credential-paster

Give your AI coding agent API keys – without giving them to the AI.

<img src="docs/demo.svg" alt="Claude Code asks for OPENAI_API_KEY, a masked paste field opens, the key is written to .env without entering the chat" width="760"> </div> <br>

When an agent needs a credential, the usual answer is to paste it into the chat. From then on it lives in the transcript, the model's context and your logs.

credential-paster splits the job: the agent decides where a secret goes, you supply the value through a channel the agent cannot read, and a tiny script writes it straight into the file.

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Never in the chat

The value doesn't show up in the transcript, the model's context, shell history, ps or tool output. The agent only ever sees SET / MISSING.

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Any file format

.env out of the box. JSON, YAML, TOML, .npmrc, .netrc, connection URLs, PEM keys via placeholders, with the right escaping.

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Paste field in Claude Code

A masked input right above the prompt. Paste, Enter, done. Also: native password dialog, clipboard, hidden terminal prompt, password managers.

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Works with every agent

Claude Code, Codex, Cursor, Gemini CLI, Copilot, OpenCode and anything else that reads Agent Skills. Bash + awk only.

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Install

| Agent | Command | |---|---| | Claude Code – recommended, includes the paste field | /plugin marketplace add timarnoldev/credential-paster<br>/plugin install credential-paster@credential-paster | | Codex, Cursor, Gemini CLI, Copilot, OpenCode, … | npx skills add timarnoldev/credential-paster | | Manual – also puts paste-secret on your PATH | git clone https://github.com/timarnoldev/credential-paster && ./credential-paster/install.sh |

[!TIP] After installing, run /reload-plugins (or restart). The paste field is available from your next message on. Using the plugin? Don't also select Claude Code in npx skills add, otherwise the skill is installed twice.

Optionally pick a default input method so the agent doesn't ask:

export PASTE_SECRET_METHOD=dialog   # dialog | clipboard | tty | stdin

How it works

sequenceDiagram
    actor You
    participant Agent
    participant PS as paste-secret
    participant File as .env / config

    Agent->>PS: request OPENAI_API_KEY for .env
    PS->>You: masked field / password dialog
    You-->>PS: paste secret
    PS->>File: write value (escaped, mode 600)
    PS-->>Agent: "OK: OPENAI_API_KEY set in .env"
    Note over Agent: never sees the value,<br/>uses it by reference only

Just ask for what you need – "hook up the OpenAI client", "add my npm token" – the skill kicks in when a credential is missing. You can also open the field yourself in Claude Code:

/paste-secret .env OPENAI_API_KEY

Input methods

| Method | How you paste | macOS | Linux | |---|---|---|---| | Paste field | masked field inside Claude Code | yes | yes | | Dialog | native password dialog pops up | built-in | zenity / kdialog | | Clipboard | copy, say "ok" – cleared afterwards | built-in | wl-paste / xclip / xsel | | Terminal | hidden prompt in your own terminal | yes | yes | | Password manager | op read … \| paste-secret --stdin … | yes | yes |

CLI

<details> <summary><b>Examples</b></summary>

# .env files: set KEY (file created if missing, mode 600)
paste-secret .env OPENAI_API_KEY                 # hidden terminal prompt
paste-secret --dialog    .env OPENAI_API_KEY     # native password dialog
paste-secret --clipboard .env OPENAI_API_KEY     # from clipboard, then clears it
op read "op://Private/OpenAI/key" | paste-secret --stdin .env OPENAI_API_KEY

# any format: replace a placeholder the agent put into the file
paste-secret --dialog --placeholder __PASTE_SECRET_TOKEN__ config.json            # JSON-escaped (auto)
paste-secret --dialog --placeholder __PASTE_SECRET_DB__ --escape url compose.yml  # percent-encoded

# status without revealing anything
paste-secret --check .env OPENAI_API_KEY                                # SET | EMPTY | MISSING
paste-secret --check --placeholder __PASTE_SECRET_TOKEN__ config.json   # DONE | PENDING
paste-secret --info                                                     # preferred + available methods

</details> <details> <summary><b>Placeholders & escape modes</b></summary>

| File | The agent writes | Escape | |---|---|---| | config.json | "token": "__PASTE_SECRET_TOKEN__" | json (auto) | | YAML / TOML | token: "__PASTE_SECRET_TOKEN__" | json | | .npmrc | //registry.npmjs.org/:_authToken=__PASTE_SECRET_NPM__ | none | | .netrc | machine api.x.com login me password __PASTE_SECRET_PW__ | none | | connection URL | postgres://user:__PASTE_SECRET_DB__@host/db | url | | shell script | TOKEN=__PASTE_SECRET_TOKEN__ | shell | | PEM / multi-line | __PASTE_SECRET_KEY__ on its own line | none |

auto picks json for *.json, dotenv for .env*, otherwise none. See paste-secret --help.

</details>

Security

• The value reaches awk via the environment, never via argv – invisible in ps.
• The script never prints the value; output is file, key and status only.
• Clipboard mode is convenient, but clipboard managers with history may keep a copy.
• The Claude Code paste field is built on the plugin hooks API (early access); without an interactive UI the agent falls back to the other methods.
• For a hard guarantee that Claude never reads secret files, add to ~/.claude/settings.json:

  { "permissions": { "deny": ["Read(**/.env)", "Read(**/.env.*)"] } }
  

Why

A masked input for secrets was requested for Claude Code and closed as not planned. credential-paster fills that gap – for Claude Code and every other agent.

Development

claude plugin test .                                                        # Claude Code plugin
tests/test.sh                                                               # CLI on macOS
docker run --rm -v "$PWD":/w -w /w debian:stable-slim bash tests/test.sh   # CLI on Linux

<div align="center">_{MIT © <a href="https://github.com/timarnoldev">Tim Arnold</a>}</div>