Build an Autonomous Bug-Fixing Agent with GLM-5.2

# client.py
import os
from openai import OpenAI
# Self-hosted: run `vllm serve zai-org/GLM-5.2 --port 8000` first,
# then base_url = "http://localhost:8000/v1".
# Hosted: point base_url at your GLM-5.2 provider.
client = OpenAI(
base_url=os.environ.get("GLM_BASE_URL", "http://localhost:8000/v1"),
api_key=os.environ.get("GLM_API_KEY", "not-needed-for-local"),
)
MODEL = "zai-org/GLM-5.2"

# tools.py
import subprocess
from pathlib import Path
ROOT = Path("workspace").resolve() # the agent never escapes this dir
def read_file(path: str) -> str:
target = (ROOT / path).resolve()
target.relative_to(ROOT) # raises if path escapes ROOT
return target.read_text()
def write_file(path: str, content: str) -> str:
target = (ROOT / path).resolve()
target.relative_to(ROOT)
target.write_text(content)
return f"wrote {len(content)} chars to {path}"
def run_tests() -> str:
result = subprocess.run(
["python", "-m", "pytest", "-x", "-q"],
cwd=ROOT, capture_output=True, text=True, timeout=120,
)
return (result.stdout + result.stderr)[-4000:] # tail is where failures live

# schemas.py
TOOLS = [
{"type": "function", "function": {
"name": "read_file",
"description": "Read a file from the workspace.",
"parameters": {"type": "object", "properties": {
"path": {"type": "string"}}, "required": ["path"]}}},
{"type": "function", "function": {
"name": "write_file",
"description": "Overwrite a file in the workspace with new content.",
"parameters": {"type": "object", "properties": {
"path": {"type": "string"}, "content": {"type": "string"}},
"required": ["path", "content"]}}},
{"type": "function", "function": {
"name": "run_tests",
"description": "Run the pytest suite and return the output.",
"parameters": {"type": "object", "properties": {}}}},
]

# agent.py
import json
from client import client, MODEL
from schemas import TOOLS
import tools
DISPATCH = {"read_file": tools.read_file,
"write_file": tools.write_file,
"run_tests": tools.run_tests}
def fix_bug(task: str, max_steps: int = 12) -> bool:
messages = [
{"role": "system", "content":
"You fix failing tests. Read the code, write a patch, run the "
"tests. Repeat until they pass. Change as little as possible."},
{"role": "user", "content": task},
]
for step in range(max_steps):
reply = client.chat.completions.create(
model=MODEL, messages=messages, tools=TOOLS, temperature=0,
)
msg = reply.choices[0].message
messages.append(msg)
if not msg.tool_calls:
return False # model gave up or just chatted
for call in msg.tool_calls:
args = json.loads(call.function.arguments or "{}")
output = DISPATCH[call.function.name](**args)
messages.append({"role": "tool",
"tool_call_id": call.id, "content": output})
if call.function.name == "run_tests" and "passed" in output \
and "failed" not in output:
return True # green, we are done
return False

# run.py -> python run.py
import json
import subprocess
from pathlib import Path
from openai import OpenAI
ROOT = Path("workspace").resolve()
client = OpenAI(base_url="http://localhost:8000/v1", api_key="local")
MODEL = "zai-org/GLM-5.2"
def read_file(path):
t = (ROOT / path).resolve(); t.relative_to(ROOT); return t.read_text()
def write_file(path, content):
t = (ROOT / path).resolve(); t.relative_to(ROOT); t.write_text(content)
return f"wrote {path}"
def run_tests():
r = subprocess.run(["python", "-m", "pytest", "-x", "-q"], cwd=ROOT,
capture_output=True, text=True, timeout=120)
return (r.stdout + r.stderr)[-4000:]
DISPATCH = {"read_file": read_file, "write_file": write_file,
"run_tests": run_tests}
TOOLS = [
{"type": "function", "function": {"name": "read_file",
"description": "Read a workspace file.", "parameters": {"type": "object",
"properties": {"path": {"type": "string"}}, "required": ["path"]}}},
{"type": "function", "function": {"name": "write_file",
"description": "Overwrite a workspace file.", "parameters": {"type": "object",
"properties": {"path": {"type": "string"}, "content": {"type": "string"}},
"required": ["path", "content"]}}},
{"type": "function", "function": {"name": "run_tests",
"description": "Run pytest.", "parameters": {"type": "object",
"properties": {}}}},
]
def fix_bug(task, max_steps=12):
messages = [
{"role": "system", "content": "You fix failing tests. Read, patch, "
"run, repeat until green. Change as little as possible."},
{"role": "user", "content": task}]
for _ in range(max_steps):
msg = client.chat.completions.create(
model=MODEL, messages=messages, tools=TOOLS,
temperature=0).choices[0].message
messages.append(msg)
if not msg.tool_calls:
return False
for call in msg.tool_calls:
args = json.loads(call.function.arguments or "{}")
out = DISPATCH[call.function.name](**args)
messages.append({"role": "tool", "tool_call_id": call.id,
"content": out})
if call.function.name == "run_tests" and "passed" in out \
and "failed" not in out:
return True
return False
if __name__ == "__main__":
ok = fix_bug("The test in test_parser.py fails. Find and fix the bug.")
print("FIXED" if ok else "COULD NOT FIX")