System Prompt

agentOS automatically injects a system prompt into every agent session that describes the VM environment and available tools. The prompt is additive and never replaces the agent’s own instructions (CLAUDE.md, AGENTS.md, etc.).

The base prompt is embedded in the sidecar (not written to a file inside the VM). At session start the sidecar assembles the base prompt with your additional instructions and generated tool docs, then injects the result into the agent adapter’s launch arguments (for example, --append-system-prompt for Pi).

Customization

• additionalInstructions appends extra instructions to the agent’s system prompt. They are added after the base OS prompt and the generated tool docs, so they layer on top of (rather than replace) the agent’s own instructions.
• skipOsInstructions suppresses the base OS prompt while still injecting the generated tool docs.

const session = await vm.createSession("pi", {
  env: { ANTHROPIC_API_KEY: process.env.ANTHROPIC_API_KEY! },
  // Extra instructions appended to the agent system prompt
  additionalInstructions: "Always write tests before implementation.",
  // Suppress the base OS prompt (tool docs are still injected)
  skipOsInstructions: true,
});

additionalInstructions can also be set globally in agentOs({ options: { additionalInstructions } }) so it applies to every session.