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shareai-lab--learn-claude-code/s10_system_prompt/code.py
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chore: import upstream snapshot with attribution
2026-07-13 12:12:24 +08:00

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7.4 KiB
Python

#!/usr/bin/env python3
"""
s10: System Prompt — Runtime prompt assembly with caching.
Run: python s10_system_prompt/code.py
Need: pip install anthropic python-dotenv + .env with ANTHROPIC_API_KEY
Changes from s09:
- PROMPT_SECTIONS: topic-keyed dict of prompt fragments
- assemble_system_prompt(context): select + join sections by real state
- get_system_prompt(context): deterministic cache via json.dumps
- agent_loop uses get_system_prompt(context) instead of hardcoded SYSTEM
Memory section loads when .memory/MEMORY.md exists (real state, not keywords).
"""
import os, subprocess, json
from pathlib import Path
try:
import readline
readline.parse_and_bind('set bind-tty-special-chars off')
except ImportError:
pass
from anthropic import Anthropic
from dotenv import load_dotenv
load_dotenv(override=True)
if os.getenv("ANTHROPIC_BASE_URL"):
os.environ.pop("ANTHROPIC_AUTH_TOKEN", None)
WORKDIR = Path.cwd()
MEMORY_DIR = WORKDIR / ".memory"
MEMORY_INDEX = MEMORY_DIR / "MEMORY.md"
client = Anthropic(base_url=os.getenv("ANTHROPIC_BASE_URL"))
MODEL = os.environ["MODEL_ID"]
# ── Prompt Sections ──
PROMPT_SECTIONS = {
"identity": "You are a coding agent. Act, don't explain.",
"tools": "Available tools: bash, read_file, write_file.",
"workspace": f"Working directory: {WORKDIR}",
"memory": "Relevant memories are injected below when available.",
}
def assemble_system_prompt(context: dict) -> str:
"""Select and join prompt sections based on current context."""
sections = []
# Always loaded — identity, tools, workspace
sections.append(PROMPT_SECTIONS["identity"])
sections.append(PROMPT_SECTIONS["tools"])
sections.append(PROMPT_SECTIONS["workspace"])
# Conditional — memory loaded when MEMORY.md exists and has content
memories = context.get("memories", "")
if memories:
sections.append(f"Relevant memories:\n{memories}")
return "\n\n".join(sections)
_last_context_key = None
_last_prompt = None
def get_system_prompt(context: dict) -> str:
"""Cache wrapper — reassemble only when context changes.
Uses json.dumps for deterministic serialization, not Python's hash()
which has process randomization and fails on nested dicts/lists.
This cache only avoids redundant string assembly within a process.
Real Claude Code additionally protects API-level prompt cache via
stable section ordering and SYSTEM_PROMPT_DYNAMIC_BOUNDARY.
"""
global _last_context_key, _last_prompt
key = json.dumps(context, sort_keys=True, ensure_ascii=False, default=str)
if key == _last_context_key and _last_prompt:
print(" \033[90m[cache hit] system prompt unchanged\033[0m")
return _last_prompt
_last_context_key = key
_last_prompt = assemble_system_prompt(context)
loaded = ["identity", "tools", "workspace"]
if context.get("memories"):
loaded.append("memory")
print(f" \033[32m[assembled] sections: {', '.join(loaded)}\033[0m")
return _last_prompt
# ── Tools ──
def safe_path(p: str) -> Path:
path = (WORKDIR / p).resolve()
if not path.is_relative_to(WORKDIR):
raise ValueError(f"Path escapes workspace: {p}")
return path
def run_bash(command: str) -> str:
try:
r = subprocess.run(command, shell=True, cwd=WORKDIR,
capture_output=True, text=True, timeout=120)
out = (r.stdout + r.stderr).strip()
return out[:50000] if out else "(no output)"
except subprocess.TimeoutExpired:
return "Error: Timeout (120s)"
def run_read(path: str, limit: int | None = None) -> str:
try:
lines = safe_path(path).read_text().splitlines()
if limit and limit < len(lines):
lines = lines[:limit] + [f"... ({len(lines) - limit} more lines)"]
return "\n".join(lines)
except Exception as e:
return f"Error: {e}"
def run_write(path: str, content: str) -> str:
try:
file_path = safe_path(path)
file_path.parent.mkdir(parents=True, exist_ok=True)
file_path.write_text(content)
return f"Wrote {len(content)} bytes to {path}"
except Exception as e:
return f"Error: {e}"
TOOLS = [
{"name": "bash", "description": "Run a shell command.",
"input_schema": {"type": "object",
"properties": {"command": {"type": "string"}},
"required": ["command"]}},
{"name": "read_file", "description": "Read file contents.",
"input_schema": {"type": "object",
"properties": {"path": {"type": "string"},
"limit": {"type": "integer"}},
"required": ["path"]}},
{"name": "write_file", "description": "Write content to a file.",
"input_schema": {"type": "object",
"properties": {"path": {"type": "string"},
"content": {"type": "string"}},
"required": ["path", "content"]}},
]
TOOL_HANDLERS = {"bash": run_bash, "read_file": run_read, "write_file": run_write}
# ── Context ──
def update_context(context: dict, messages: list) -> dict:
"""Derive context from real state: which tools exist, whether memory files exist."""
memories = ""
if MEMORY_INDEX.exists():
content = MEMORY_INDEX.read_text().strip()
if content:
memories = content
return {
"enabled_tools": list(TOOL_HANDLERS.keys()),
"workspace": str(WORKDIR),
"memories": memories,
}
# ── Agent Loop ──
def agent_loop(messages: list, context: dict):
"""Main loop — uses assembled system prompt instead of hardcoded SYSTEM."""
system = get_system_prompt(context)
while True:
response = client.messages.create(
model=MODEL, system=system, messages=messages,
tools=TOOLS, max_tokens=8000)
messages.append({"role": "assistant", "content": response.content})
if response.stop_reason != "tool_use":
return
results = []
for block in response.content:
if block.type != "tool_use":
continue
print(f"\033[36m> {block.name}\033[0m")
handler = TOOL_HANDLERS.get(block.name)
output = handler(**block.input) if handler else f"Unknown: {block.name}"
print(str(output)[:200])
results.append({"type": "tool_result",
"tool_use_id": block.id, "content": output})
messages.append({"role": "user", "content": results})
# Re-evaluate context and prompt after each tool round
context = update_context(context, messages)
system = get_system_prompt(context)
if __name__ == "__main__":
print("s10: system prompt — runtime assembly")
print("Enter a question, press Enter to send. Type q to quit.\n")
history = []
context = update_context({}, [])
while True:
try:
query = input("\033[36ms10 >> \033[0m")
except (EOFError, KeyboardInterrupt):
break
if query.strip().lower() in ("q", "exit", ""):
break
history.append({"role": "user", "content": query})
agent_loop(history, context)
context = update_context(context, history)
for block in history[-1]["content"]:
if getattr(block, "type", None) == "text":
print(block.text)
print()