DDD — Harness Engineering

Streamlit harness for deepagents with assignment-driven implementation modules.

• SCORECARD.md — the 12 components of an agent, as a checklist you keep afterwards
• docs/modules/ — base-to-solution module branch flow and per-module assignment READMEs
• CLAUDE.md — architecture and implementation conventions

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Setup

Install uv:

Windows (PowerShell)

powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

macOS and Linux

curl -LsSf https://astral.sh/uv/install.sh | sh

Open a new terminal and verify the installation:

uv --version

Then set up and run the project:

git clone https://github.com/DatacationOrg/ddd-harness-engineering-public.git
cd ddd-harness-engineering-public

uv sync                                          # install everything
cp .env.example .env                             # PowerShell: Copy-Item .env.example .env
                                                 # then paste in the key you were given
uv run python scripts/seed_sandbox.py --reset    # generate the agent's sandbox
uv run streamlit run ddd_harness_engineering/main.py

Then ask it something in the collapsible chat drawer on the right. The Activity workspace shows agent actions, arguments, results, and approval decisions.

uv run pytest        # no API key required

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Sandbox

scripts/seed_sandbox.py generates sandbox/northwind-freight/.

Use it as the only runtime workspace for assignments.

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How a station works

Every module follows this sequence:

Beat
Ship	Apply the guided change manually, or brief your coding agent. Get it working.
Break	Feed it garbage, oversized input, malicious input. Try to escape the sandbox.
Guard	Add the constraint that makes your break impossible.
Observe	Find the whole story in the execution trace.
Log	Tick the scorecard. Write one line on what surprised you.

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Safety

• Never commit .env. It is gitignored. Never paste your key into chat and never screen-share it.
• Point the agent at sandbox/ and nothing else. Station 2 is where you make that a hard boundary rather than a good intention.
• Station 4 enables shell execution. Keep command guardrails enabled.