@rehydra/opencode

Prevent your coding agent from leaking secrets to LLM providers.

This plugin intercepts the conversation between OpenCode and the LLM. Secrets from your .env files are replaced with placeholders before they leave your machine, and transparently restored before any tool (shell commands, file writes, etc.) executes locally.

The LLM never sees real secret values. Your tools run with them.

Install

npm install @rehydra/opencode

Add to opencode.json:

{
  "plugin": ["@rehydra/opencode"]
}

By default, the plugin reads .env in your project root. Secrets with values of 4+ characters are detected and scrubbed.

Configuration

For custom settings, create .opencode/plugins/rehydra.ts:

import { createRehydraPlugin } from "@rehydra/opencode";

export default createRehydraPlugin({
  // Scan multiple env files
  envFiles: [".env", ".env.local", ".env.production"],

  // Always redact these values, even if not in .env
  redactValues: ["sk-live-abc123..."],

  // Minimum value length to consider a secret (default: 4)
  minValueLength: 6,

  // Disable detection of specific PII types
  disableTypes: ["URL", "IP_ADDRESS"],
});

What gets detected

• Environment variable values from .env files
• API keys, tokens, and credentials (pattern-based)
• AWS access keys and secret keys
• JWTs, private keys, connection strings
• Any values passed via redactValues

How it works

The plugin uses five OpenCode hooks:

| Hook | What it does | |---|---| | messages.transform | Scrubs secrets from all message text before it reaches the LLM | | system.transform | Tells the LLM to treat placeholders as real values | | tool.execute.before | Restores real values in tool arguments before local execution | | tool.execute.after | Restores real values in displayed tool output | | text.complete | Restores real values in LLM response text shown to you |

Everything runs locally. No data leaves your machine except the scrubbed conversation sent to the LLM provider.

Logging

Plugin activity is logged to OpenCode's log directory (~/.local/share/opencode/log/). Run with --log-level DEBUG for detailed output.

INFO service=rehydra scrubbed={"ENV_VAR_SECRET":2} messageCount=3 scrubbed 2 secret(s) from messages
INFO service=rehydra tool=bash callID=call_abc123 rehydrated PII tags in tool args

Rehydra

This plugin is part of Rehydra, an open-source SDK for PII anonymization and rehydration. Rehydra combines regex-based pattern matching with NER-based detection and supports any LLM provider via fetch wrappers, proxy servers, or framework plugins.

Full documentation at docs.rehydra.ai.

License

MIT