Diffler

Prove you understand the diff.

Diffler generates comprehension quizzes from Git branch diffs for Claude Code, OpenCode, and pull-request workflows. Its agent skill collects focused branch context, generates graded questions, and delivers them either as an offline quiz in your local terminal or as a published Google Form.

Status

Diffler is in early development. The repository contains the TypeScript project foundation, versioned quiz-document contract, local branch-context collection, interactive local quiz delivery, Google Forms authentication and publication, and a portable Claude Code and OpenCode skill.

Requirements

• Node.js 24 or newer
• pnpm 11.18.0
• Git 2.42 or newer

Development

Install dependencies and run all checks:

pnpm install --frozen-lockfile
pnpm check
pnpm build

Run the development CLI:

pnpm start --help
pnpm start context --base main
pnpm start quiz .diffler/quiz.json --context .diffler/context.json
pnpm start publish .diffler/quiz.json --context .diffler/context.json

Run an installed quiz locally, without Google authentication or network access:

diffler quiz .diffler/quiz.json --context .diffler/context.json

Google authentication is optional and needed only for Forms delivery. To authorize publication, follow the Google authentication setup, then run diffler auth login. Maintainers can still select a bring-your-own Desktop client with --credentials <path>. Install the packaged agent skill and check local readiness with:

diffler skill install claude --scope user
diffler doctor

See Google Forms publishing for the optional publication flow and manual verification steps. Install the agent workflow using the skill installation guide. Maintainers can inspect and install the exact npm tarball by following the npm publication guide.

The aggregate check command verifies formatting, linting, types, and tests. CI runs the same checks on pull requests and pushes to main. The stable Review Gate check and recommended branch protection are documented in Repository Settings. Maintainers can verify both canonical Google Cloud environments without making changes by running pnpm cloud:check; see Google Authentication.

Intended Workflow

1. Compare the current branch with its merge base.
2. Exclude generated and low-value changes.
3. Ask questions about behavior, rationale, risks, and changed invariants.
4. Validate the quiz document.
5. Choose an interactive local quiz or an automatically graded Google Form.

Repository Layout

src/                 TypeScript CLI and domain implementation
docs/                Context and quiz contracts
skills/diffler/      Packaged Claude Code and OpenCode skill
.github/workflows/   Continuous integration

Design Principles

• Prefer a small, verifiable implementation over speculative flexibility.
• Keep Git, quiz-domain, and Google API responsibilities separate.
• Treat diffs, generated questions, credentials, and OAuth tokens as sensitive.
• Make local commands and CI enforce the same checks.

License

MIT. See LICENSE.