v1.12 track A: container guidance + skills

apps/server/src/services/system-prompt.ts

@@ -0,0 +1,83 @@
+// v1.12: extracted from inference.ts to give the prompt-assembly logic its
+// own home + test surface. Adds the container-guidance layer (BOOCHAT.md
+// baked into the Docker image, injected between the base prompt and the
+// agent block).
+//
+// Resolution order, last-wins on conflicts:
+//   base prompt
+//   + container guidance (this layer, NEW in v1.12)
+//   + agent.system_prompt          (resolved from data/AGENTS.md by getAgentById)
+//   + session.system_prompt OR project.default_system_prompt
+
+import { readFile, stat } from 'node:fs/promises';
+import type { Agent, Project, Session } from '../types/api.js';
+
+const BASE_SYSTEM_PROMPT = (projectPath: string) =>
+  `You are BooCode Chat, a code investigation assistant. The user is working on a project located at ${projectPath}. Use the file-read tools (view_file, list_dir, grep, find_files) to investigate code when needed. Be concise. Cite file paths and line numbers when discussing code. Do not hallucinate file contents — read the file first. Tool results may be truncated; if so, narrow your query rather than guessing.`;
+
+// v1.12 mtime-watch cache. Mirrors the safeStat pattern in services/agents.ts.
+// On every call we stat the file; if the mtime matches the cached entry we
+// return the cached content without re-reading. If the file is missing we
+// cache { mtime: 0, content: null } so the not-found case still benefits
+// from caching (one stat per call, no readFile attempt on a known-missing
+// path). Because BOOCHAT.md is bind-mounted from the host, edits land
+// immediately on the next chat turn — no container restart needed.
+let cachedGuidance: { mtime: number; content: string | null } | null = null;
+
+function resolveGuidancePath(): string {
+  return process.env['CONTAINER_GUIDANCE_FILE'] ?? '/app/BOOCHAT.md';
+}
+
+export async function loadContainerGuidance(): Promise<string | null> {
+  const path = resolveGuidancePath();
+  try {
+    return await readFile(path, 'utf8');
+  } catch {
+    return null;
+  }
+}
+
+export async function getContainerGuidance(): Promise<string | null> {
+  const path = resolveGuidancePath();
+  let mtimeMs: number;
+  try {
+    const s = await stat(path);
+    mtimeMs = s.mtimeMs;
+  } catch {
+    cachedGuidance = { mtime: 0, content: null };
+    return null;
+  }
+  if (cachedGuidance && cachedGuidance.mtime === mtimeMs) {
+    return cachedGuidance.content;
+  }
+  const content = await loadContainerGuidance();
+  cachedGuidance = { mtime: mtimeMs, content };
+  return content;
+}
+
+// Test-only: clear the cache so consecutive tests don't share state.
+export function _resetContainerGuidanceCacheForTests(): void {
+  cachedGuidance = null;
+}
+
+export async function buildSystemPrompt(
+  project: Project,
+  session: Session,
+  agent: Agent | null
+): Promise<string> {
+  let out = BASE_SYSTEM_PROMPT(project.path);
+  const guidance = await getContainerGuidance();
+  if (guidance) {
+    out += `\n\n--- Container guidance ---\n${guidance}\n--- end container guidance ---\n`;
+  }
+  if (agent && agent.system_prompt.trim().length > 0) {
+    out += '\n\n' + agent.system_prompt.trim();
+  }
+  const sessionPrompt = session.system_prompt?.trim() ?? '';
+  const projectPrompt = project.default_system_prompt?.trim() ?? '';
+  const userPrompt = sessionPrompt || projectPrompt;
+  if (userPrompt.length > 0) {
+    out += '\n\n' + userPrompt;
+  }
+  return out;
+}