opencode-stream-rules

Inject rules when needed, without wasting context.

You can write custom streaming rules for the agent.

These rules are injected only as a steering notice after a pattern match, then agent retry from the same point. This allows you to control the boundaries of agent behavior, without wasting context.

Similar to oh-my-pi's "Time-traveling stream rules", but with a very simple and compact code implementation.

Install

opencode plugin opencode-stream-rules

Or add to opencode.json:

{ "plugin": ["opencode-stream-rules"] }

After installing

You need to write the rules in your own .ts file. This plugin WON'T WORK by default until you edit the rules.

You can start with:

1. Locate the this plugin's path

such as: ~/.cache/opencode/packages/opencode-stream-rules@latest/node_modules/opencode-stream-rules

alternatively, if it's a local installation: ~/.config/opencode/plugins/opencode-stream-rules

2. Write rules

mv rules/rules.ts.example rules/rules.local.ts

• Rules live in the rules/ directory next to this plugin
  • Files starting with _ are skipped.
  • To point at a different rules directory: { "plugin": [["opencode-stream-rules", { "rules": "path/to/your/rules" }]] }
• Using .ts as rules makes it easier to write pattern match functions without being limited to regx. Code is cheap; let your agent write the code!
• A rule with reject: true will only be rejected on the first toolcall; subsequent attempts by the agent will be allowed. This provides steering while avoiding overly restricting the model (e.g., allowing pip install if it's already in a container).

Writing rules

Example:

// rules/rules.local.ts
import type { Rule } from "../index.ts"

export default [
  {
    match: (v) =>
      v.includes("pip") &&
      v.includes("install") &&
      !v.includes("uv pip") &&
      !v.includes("uvx"),
    reject: true,
    prompt: "Use `uvx` or `uv venv` + `uv pip` instead of `pip install` directly",
  },
  {
    match: (v) => v.includes("curl") && v.includes("api.github.com"),
    prompt: "Prefer using `gh` cli over `curl https://api.github.com/...`. gh offers more requests limits.",
  },
  {
    match: (v) => v.includes("pdf"),
    prompt: "Use the `markitdown` skill to read PDF files.",
  },
  // add your rules here
]

A rule has three fields:

field	required	description
match	✅	(v: string) => boolean, any responses/toolcalls returned by LLM will attempted to be matched
prompt	✅	The prompt for steering
reject		If true, prevent toolcalls first, instead of just steering