Show HN: Diff Glance – CLI that turns a Git diff into a summary and a diagram

Diff Glance, a new command-line tool announced on Hacker News, turns Git diffs into plain-English summaries and architecture diagrams using AI. The tool, requiring Node.js 18+ and an OpenAI-compatible API key, supports multiple providers including OpenAI, Google Gemini, OpenRouter, Groq, and Ollama, and serves results via a local HTTP viewer. It filters out lockfiles and binaries before sending the diff to the model, and offers flags for staged changes, specific commits, JSON output, and custom model endpoints.

Turn messy git diffs into plain-English summaries and architecture diagrams. npx diff-glance npx diff-glance origin/main HEAD Requires Node.js 18+, git on PATH , and an OpenAI-compatible API key or a local Ollama endpoint . Default range is HEAD vs the worktree staged + unstaged + untracked . If the worktree is clean, that falls back to --commit HEAD . The second command diffs two refs. There is no stdin pipe. bash $ diff-glance diff-glance: analyzing diff... diff-glance: generating summary... diff-glance: viewer at http://127.0.0.1:53102 diff-glance: press Ctrl+C to stop The local viewer bound to 127.0.0.1 opens in your browser: Use --json to print the same analysis to stdout, or -o report.html to write the HTML file instead of serving it. - Line-by-line diffs do not answer “what changed and what might break.” - A 30-second ELI5 plus a module graph is a usable mental model before a PR review. - Lockfiles, binaries, and generated dirs are dropped before the model sees the patch. - The viewer is an ephemeral local HTTP server. Nothing is uploaded except the truncated diff you send to the model you configured. | Provider | How it is selected | Default model | |---|---|---| | OpenAI | OPENAI API KEY | gpt-4o-mini | | Google Gemini | GEMINI API KEY or GOOGLE API KEY | gemini-3.6-flash | | OpenRouter | OPENROUTER API KEY | openai/gpt-4o-mini | | Groq | GROQ API KEY | llama-3.3-70b-versatile | | Ollama | --base-url http://127.0.0.1:11434/v1 | llama3.2 | | Custom | --base-url + --api-key | gpt-4o-mini unless the URL matches a row above | Anthropic is not a native SDK path. Route it through OpenRouter --model anthropic/claude-sonnet-4 or any other OpenAI-compatible gateway. Vertex AI works the same way: pass its OpenAI-compatible --base-url . If more than one key is set, resolution order is: --api-key → DIFF GLANCE API KEY → OPENAI API KEY → OPENROUTER API KEY → GROQ API KEY → GEMINI API KEY / GOOGLE API KEY / GOOGLE GENERATIVE AI API KEY . A dummy key of ollama is used only when the base URL is local and no other key is present. | Flag | Behavior | |---|---| from to | Git refs. One arg diffs that ref vs the worktree; two args diffs from..to . | -s, --staged | Staged changes only git diff --cached . | -c, --commit <sha | That commit vs its parent <sha ^ . | -m, --model <id | Model id. | --base-url <url | OpenAI-compatible API base URL. | --api-key <key | API key. | -p, --port <n | Viewer port. 0 default picks an ephemeral port. | --host <host | Viewer bind host. Default 127.0.0.1 . | --no-open | Do not open a browser. | --json | Print analysis JSON to stdout; skip the viewer. | --max-chars <n | Max diff characters sent to the model. Default 80000 . | -o, --output <file | Write HTML to a file instead of serving. | diff-glance --staged diff-glance --commit HEAD diff-glance --json diff-glance -o glance.html --no-open diff-glance --base-url http://127.0.0.1:11434/v1 --model llama3.2 | Variable | Role | |---|---| OPENAI API KEY | OpenAI key also used as a generic key if you set a custom base URL . | OPENAI BASE URL | OpenAI-compatible base URL. | OPENAI MODEL | Model id fallback. | DIFF GLANCE API KEY | Overrides other keys except --api-key . | DIFF GLANCE BASE URL | Overrides OPENAI BASE URL . | DIFF GLANCE MODEL | Overrides OPENAI MODEL . | OPENROUTER API KEY | Selects OpenRouter. | GROQ API KEY | Selects Groq. | GEMINI API KEY / GOOGLE API KEY / GOOGLE GENERATIVE AI API KEY | Selects Gemini. | DIFF GLANCE DEBUG | If set, print the raw error after the one-line stderr message. | --base-url and --model beat the env vars. There is no AI BASE URL or AI MODEL . The HTML viewer never leaves the machine. It listens on 127.0.0.1 and serves one generated page. Cloud providers receive the truncated unified diff lockfiles and binaries already stripped . Point --base-url at http://127.0.0.1:11434/v1 Ollama or any other local OpenAI-compatible server and the request stays on localhost — no --local flag; the loopback URL is what keeps the payload off the network. git clone https://github.com/alvynmcq/diff-glance.git cd diff-glance npm install npm run dev npm run dev runs tsx src/index.ts . npm run build emits dist/ for node bin/diff-glance.js . npm run typecheck runs tsc --noEmit .