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  • v6.5.0

      • Prompt Slots

      Prompt slots are session options that shape the agent's system prompt declaratively. Use them for host-level behavior — persona, coding standards, output style — that should not live inside each user prompt. The slots layer on top of the agent's built-in instructions, so core tool behavior (reading, writing, running commands) is preserved.

      There are four slots:

      SlotPurpose
      role / roleThe persona the agent adopts.
      guidelines / guidelinesStandards and rules the agent must follow.
      responseStyle / response_styleHow the agent should format its replies.
      extra / extraFreeform instructions appended verbatim.

      Basic usage

      Set any subset of the slots when you open a session. They apply to every turn of that session.

      Node.js
      Python
      TypeScript
      import { Agent } from '@a3s-lab/code';

      

      async function main() {

        // create() accepts an .acl file path or inline ACL string.

        const agent = await Agent.create('agent.acl');

      

        const session = agent.session('/repo', {

          role: 'release-readiness reviewer',

          guidelines:

            'Find blockers before improvements. Require command evidence for done claims.',

          responseStyle: 'concise, findings first',

        });

      

        const result = await session.send('Is this repo ready to ship?');

        console.log(result.text);

      

        session.close();

      }

      

      main().catch((err) => {

        console.error(err);

        process.exit(1);

      });

      Each slot in turn

      The four slots compose independently. A persona-only session, a reviewer with strict guidelines, and a session that appends a freeform instruction all use the same option set.

      Node.js
      Python
      TypeScript
      // 1. Custom role only.

      let session = agent.session(workspace, {

        role: 'You are a senior Rust developer who specializes in async programming.',

      });

      

      // 2. Role + guidelines + response style.

      session = agent.session(workspace, {

        role: 'You are a Python code reviewer.',

        guidelines: 'Always check for type hints. Flag any use of `eval()`.',

        responseStyle: 'Reply in bullet points. Be concise.',

      });

      

      // 3. Extra freeform instructions only.

      session = agent.session(workspace, {

        extra: "Always end your response with '-- A3S'",

      });

      

      // Core tool behavior is preserved regardless of the slots.

      session = agent.session(workspace, {

        role: 'You are a minimalist file manager.',

        guidelines: 'Only create files when explicitly asked.',

      });

      const result = await session.send(

        "Create a file called test.txt with the content 'prompt slots work'. Then read it back.",

      );

      Slots customize personality and house rules; they do not disable tools or change the agent's core loop. Keep task-specific requests in the send message and reserve the slots for behavior that should hold across every turn of the session.

      A runnable version ships at crates/code/sdk/node/examples/skills/test_prompt_slots.ts.