feat: enable permission-aware subagents

2026-08-28 16:45:22 +00:00 · 2026-08-26 10:49:26 +08:00
parent d3bf562189
commit 7571ba6dd9
185 changed files with 48365 additions and 26 deletions
@@ -0,0 +1,116 @@
+/**
+ * prompts.ts — System prompt builder for agents.
+ */
+
+import type { AgentConfig, EnvInfo } from "./types.js";
+
+/** Extra sections to inject into the system prompt (memory, skills, etc.). */
+export interface PromptExtras {
+  /** Persistent memory content to inject (first 200 lines of MEMORY.md + instructions). */
+  memoryBlock?: string;
+  /** Preloaded skill contents to inject. */
+  skillBlocks?: { name: string; content: string }[];
+  /**
+   * Parent directory the worktree copy was created from. Set only for
+   * `isolation: "worktree"` spawns — triggers the block that tells the agent
+   * to stay in the copy.
+   */
+  worktreeBase?: string;
+}
+
+/**
+ * Build the system prompt for an agent from its config.
+ *
+ * - "replace" mode: env header + config.systemPrompt (full control, no parent identity)
+ * - "append" mode: parent system prompt + sub-agent context + env header + config.systemPrompt
+ * - "append" with empty systemPrompt: pure parent clone
+ *
+ * Both modes include an `<active_agent name="${config.name}"/>` tag so downstream
+ * extensions (e.g. permission/policy systems) can resolve per-agent policy
+ * inside the child session by parsing the system prompt. In replace mode the tag
+ * is prepended; in append mode it follows the shared inherited content so the
+ * parent prompt forms an identical, cacheable byte prefix with the parent
+ * session (the LLM's KV cache can then reuse those tokens across every spawn).
+ *
+ * @param parentSystemPrompt  The parent agent's effective system prompt (for append mode).
+ * @param extras  Optional extra sections to inject (memory, preloaded skills).
+ */
+export function buildAgentPrompt(
+  config: AgentConfig,
+  cwd: string,
+  env: EnvInfo,
+  parentSystemPrompt?: string,
+  extras?: PromptExtras,
+): string {
+  const activeAgentTag = `<active_agent name="${config.name}"/>\n\n`;
+
+  const envBlock = `# Environment
+Working directory: ${cwd}
+${env.isGitRepo ? `Git repository: yes\nBranch: ${env.branch}` : "Not a git repository"}
+Platform: ${env.platform}`;
+
+  // A worktree agent is told its cwd twice: by the env block above (the copy)
+  // and by whatever names the main checkout — the inherited parent prompt in
+  // append mode, or the task prompt in either mode. It follows the latter and
+  // works in the shared tree (#187), so resolve the contradiction explicitly.
+  const worktreeBlock = extras?.worktreeBase
+    ? `\n\n<worktree_isolation>
+Your working directory is an isolated git worktree copy of ${extras.worktreeBase}.
+Work only inside it — never in ${extras.worktreeBase}, even if other instructions name that path as your working directory.
+</worktree_isolation>`
+    : "";
+
+  // Build optional extras suffix
+  const extraSections: string[] = [];
+  if (extras?.memoryBlock) {
+    extraSections.push(extras.memoryBlock);
+  }
+  if (extras?.skillBlocks?.length) {
+    for (const skill of extras.skillBlocks) {
+      extraSections.push(`\n# Preloaded Skill: ${skill.name}\n${skill.content}`);
+    }
+  }
+  const extrasSuffix = extraSections.length > 0 ? "\n\n" + extraSections.join("\n") : "";
+
+  if (config.promptMode === "append") {
+    const identity = parentSystemPrompt || genericBase;
+
+    const bridge = `<sub_agent_context>
+You are operating as a sub-agent invoked to handle a specific task.
+- Use the read tool instead of cat/head/tail
+- Use the edit tool instead of sed/awk
+- Use the write tool instead of echo/heredoc
+- Use the find tool instead of bash find/ls for file search
+- Use the grep tool instead of bash grep/rg for content search
+- Make independent tool calls in parallel
+- Use absolute file paths
+- Do not use emojis
+- Be concise but complete
+</sub_agent_context>`;
+
+    const customSection = config.systemPrompt?.trim()
+      ? `\n\n<agent_instructions>\n${config.systemPrompt}\n</agent_instructions>`
+      : "";
+
+    // Place shared/stable content first so the LLM's KV cache can reuse the
+    // inherited prefix across all subagent invocations. The parent prompt is
+    // placed verbatim (no wrapper tag) so it forms an identical byte prefix
+    // with the parent session, maximising KV cache hits. The <active_agent>
+    // tag and env block vary per call and are placed after the cached prefix.
+    return identity + "\n\n" + bridge + "\n\n" + activeAgentTag + envBlock + worktreeBlock + customSection + extrasSuffix;
+  }
+
+  // "replace" mode — env header + the config's full system prompt
+  const replaceHeader = `You are a pi coding agent sub-agent.
+You have been invoked to handle a specific task autonomously.
+
+${envBlock}`;
+
+  return activeAgentTag + replaceHeader + worktreeBlock + "\n\n" + config.systemPrompt + extrasSuffix;
+}
+
+/** Fallback base prompt when parent system prompt is unavailable in append mode. */
+const genericBase = `# Role
+You are a general-purpose coding agent for complex, multi-step tasks.
+You have full access to read, write, edit files, and execute commands.
+Do what has been asked; nothing more, nothing less.`;