add optional system prompt environment injection

[Jacubeit]

Agents can have their custom system prompt. Environment system prompt gets added regardless.
Making this optional would reduce tokens and increase prompt adherence if this info is not needed for the agent to fulfill its task.

if (process.env.OPENCODE_NO_ENV_PROMPT !== 'true') {
  system.push(...(await SystemPrompt.environment()))
}

Or even better: per agent in config, as system prompts can be defined there anyways:

 "agent": {
    "build": {
      "mode": "primary",
      "model": "anthropic/claude-sonnet-4-20250514",
      "prompt": "{file:./prompts/build.txt}",
      "envinfo": false
      ...
   }
}

[calvinalkan]

Yes, this is very important to keep a clean context window.

The environent information is injected AFTER a custom Agent prompt, which puts limits on how you can end it.

I think, what makes much more send is having a placerholder in the prompt that gets replaced if it's present. Similar to arguments with / commands.

[rekram1-node]

that's an interesting idea, kinda like it

[taqtiqa-mark]

The environent information is injected AFTER a custom Agent prompt

Still getting my bearings, but shouldn't any system prompt be added separately:

    const result = await generateObject({
      model: openai('gpt-4o'),
      system: `You are a SQL (postgres) ...`, // SYSTEM PROMPT AS ABOVE - OMITTED FOR BREVITY
      prompt: `Generate the query necessary to retrieve the data the user wants: ${input}`,
      schema: z.object({
        query: z.string(),
      }),
    });

Also rather than optionally inject a hardcoded system prompt wouldn't it be better to allow users to define a SYSTEM.md per agent, say for the hypothetical IDE agent:

agent/ide.md
agent/ide/SYSTEM.md
agent/ide/create-ticket.md
...

This suggests there are three prompt types: Primary, System and Sub-Agents

[calvinalkan]

The environent information is injected AFTER a custom Agent prompt

Still getting my bearings, but shouldn't any system prompt be added separately:

const result = await generateObject({
  model: openai('gpt-4o'),
  system: `You are a SQL (postgres) ...`, // SYSTEM PROMPT AS ABOVE - OMITTED FOR BREVITY
  prompt: `Generate the query necessary to retrieve the data the user wants: ${input}`,
  schema: z.object({
    query: z.string(),
  }),
});

Also rather than optionally inject a hardcoded system prompt wouldn't it be better to allow users to define a SYSTEM.md per agent, say for the hypothetical IDE agent:

agent/ide.md
agent/ide/SYSTEM.md
agent/ide/create-ticket.md
...
This suggests there are three prompt types: Primary, System and Sub-Agents

AFAIK, the system prompt for an agent can be defined already and is used as it. The issue is how it's merged with environment specific stuff, which you have no control over.

[taqtiqa-mark]

AFAIK, the system prompt for an agent can be defined already and is used as it.

Thanks. I see that Modes is now deprecated in favor of an agent option mode, and a mode did have a prompt option (which was the system prompt). However, agent docs say that mode has one option:

https://opencode.ai/docs/agents#mode:

The mode option can be set to primary, subagent, or all. If no mode is specified, it defaults to all.

So no more mode#prompt?