alvynmcq/diff-glance

CLI that turns git diffs into ELI5 summaries and Mermaid architecture diagrams.

stars

commits

TypeScript

primary language

Aug 27, 2026

updated

README

diff-glance

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.

What you get

$ 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:

diff-glance local viewer with ELI5 summary, architecture diagram, and file notes

Use --json to print the same analysis to stdout, or -o report.html to write the HTML file instead of serving it.

Why it exists

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.

Configuration

Providers

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.

CLI

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

Environment

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.

Local-first and privacy

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.

Development

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.

License

MIT

Contributors

alvynmcq

4 commits

See what people are saying

Hacker News (1)

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

4 points · Aug 27, 2026

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alvynmcq/diff-glance

CLI that turns git diffs into ELI5 summaries and Mermaid architecture diagrams.

stars

commits

TypeScript

primary language

Aug 27, 2026

updated

README

diff-glance

Turn messy git diffs into plain-English summaries and architecture diagrams.

npx diff-glance

npx diff-glance origin/main HEAD

What you get

$ 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:

diff-glance local viewer with ELI5 summary, architecture diagram, and file notes

Use --json to print the same analysis to stdout, or -o report.html to write the HTML file instead of serving it.

Why it exists

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.

Configuration

Providers

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

CLI

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

Environment

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.

Local-first and privacy

The HTML viewer never leaves the machine. It listens on 127.0.0.1 and serves one generated page.

Development

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.

License

MIT

See what people are saying

Hacker News (1)

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

4 points · Aug 27, 2026

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Contributors

alvynmcq

4 commits

Languages

TypeScript

77.9%

HTML

22.0%