Skip to content

Sketch

chimera.training.sketch implements sketch synthesis — filling holes in partially-written source files. A SketchSpec is built from source files containing # HOLE: <description> markers. The agent receives the full file context but is instructed to fill only the marked holes.

Key Classes

Hole

A frozen dataclass representing a single hole in a sketch file.

Field	Type	Description
`id`	`int`	Unique numeric identifier across all sketch files
`description`	`str`	Human-readable description from the marker
`file_path`	`str`	Path of the sketch file containing this hole
`line`	`int`	1-based line number of the `# HOLE:` marker
`indent`	`str`	Leading whitespace of the marker line

SketchSpec

A Spec subclass created from source files with # HOLE markers. Parses files for # HOLE: <description> comments and generates a prompt instructing the agent to fill only the marked holes.

Constructors:

SketchSpec(files, description) — from a dict of {path: content}
SketchSpec.from_file(path) — load a single sketch file
SketchSpec.from_directory(path, pattern) — load all matching files

Key methods: to_prompt(), write_sketches(env), property holes.

Usage

from chimera.training.sketch import SketchSpec

# Create a sketch with holes
sketch_code = '''
def fibonacci(n: int) -> int:
    # HOLE: implement fibonacci recursively
    pass

def factorial(n: int) -> int:
    # HOLE: implement factorial iteratively
    pass
'''

spec = SketchSpec(files={"math_utils.py": sketch_code})
print(f"Found {len(spec.holes)} holes to fill")

# Write sketches into the environment and synthesize
spec.write_sketches(env)
result = trainer.synthesize(spec=spec, strategy=TestConvergence())

Training concepts — Spec and strategies
examples/synthesis/sketch_synthesis.py — runnable example