Hands-on lab: the point-group classifier¶
Build a Python package that reads a molecule's XYZ file and returns its Schoenflies point group
(H2O_C2v.xyz → C2v). The specification is a single AGENTS.md; the acceptance tests are the XYZ files in
core_xyz/, from H₂ to ferrocene, B₁₂H₁₂ (Ih) and cubane (Oh). The package must get every one right using only
the coordinates, without hard-coding filenames or formulas.
Demo repositories¶
Both packages were built from the same specification by different agents. Each has a web app where you can load a molecule and see its point group and symmetry elements in 3D, and a replay of the agent session that wrote the code: every prompt, tool call, failed attempt and fix.
| Repository | Built with | Web app (3D) | Agent trace replay |
|---|---|---|---|
| keceli/claude-pgmol | Claude Code (Claude Opus 5) | keceli.github.io/claude-pgmol | traces |
| Autonomous-Scientific-Agents/PGMol | OpenCode (GPT-5.6 Sol) | PGMol app | traces |
Watch a replay before you start: it shows what working with an agent really looks like, including the dead ends.
The replays were published with the publish-agent-trace skill and
claude-replay; see Skills.
Steps¶
git clone https://github.com/keceli/claude-pgmol.git
cd claude-pgmol
git switch -c my-try a6ff35f # first commit: only AGENTS.md and core_xyz/
/path/to/run.sh # optional: work inside the tutorial container
claude # or codex, opencode
| Step | You do | Checkpoint |
|---|---|---|
| 1 | Read AGENTS.md yourself first. What is the goal, what are the limits, how is success checked? |
you can state the success criterion |
| 2 | Ask the agent for a plan before any code. Approve or correct it. | a plan you agree with |
| 3 | Let it build, one step per prompt. Read every diff; commit each green step. | all core_xyz/ fixtures pass |
| 4 | Verify the verifier: try rotated and shuffled copies of a molecule, and a few challenge_xyz/ files from main. |
failures you understand |
| 5 | Review with a second tool or model; ask it to find defects, then fix them with tests. | review findings fixed |
| 6 | Stretch: profile on a large molecule and speed it up, or add a small GUI, keeping the tests green. | before/after numbers, or an app |
Compare your result with main of claude-pgmol and with PGMol: same specification, different agents, different
code. To split the work across sessions, see Working with multiple agents.