Hyperlight CodeAct

Collapse multi-step tool chains into a single sandboxed Python execution inside an isolated Hyperlight micro-VM (WebAssembly).

Syntax

Use call_tool(name, **kwargs) — built-in global, no import needed:

content = call_tool('view', path='src/main.py')
files = call_tool('glob', pattern='**/*.py')
hits = call_tool('grep', pattern='TODO', paths='src')
result = call_tool('bash', command='git log --oneline -5')
call_tool('edit', path='config.json', old_str='"debug": false', new_str='"debug": true')

Return types (critical — wrong assumptions cause retries)

• call_tool('glob', ...) → list of strings like ["src/app.py", ...]
• call_tool('view', ...) → string (file content)
• call_tool('bash', ...) → dict with stdout, stderr, returncode
• call_tool('mcp_call', ...) → string

Pattern

for f in call_tool('glob', pattern='src/**/*.py'):
    try:
        content = call_tool('view', path=f)
    except Exception:
        continue
    # analyze content...
    print(f"{f}: {result}")

Rules

• One bash call, one program. Do not scout with separate tool calls first.
• Wrap file reads in try/except.
• glob() returns workspace-relative paths — pass directly to view().
• Brace expansion works: call_tool('glob', pattern='src/{db,services}/**/*.py')

Discover tools

python3 scripts/codeact.py --discover       # JSON manifest
python3 scripts/codeact.py --instructions   # LLM-ready reference

Tools are auto-detected based on what's installed on the host.

Execute

uv run --python 3.13 --with 'hyperlight-sandbox[wasm,python_guest]>=0.3.0' \
  python3 scripts/codeact.py --auto --workspace . --code '...'

Output: {"stdout": "...", "stderr": "...", "exit_code": 0, "success": true}

Trust model

Sandboxed code can only reach the outside world through call_tool() bridges. Tools run on the host with full process access. Use --workspace to restrict file tools to a directory tree.

Prerequisites

• Python 3.10–3.13 (Wasm backend has no wheels for 3.14+)
• uv (recommended) or pip install 'hyperlight-sandbox[wasm,python_guest]>=0.3.0'

References

• references/tool-patterns.md