# If the user wants more details, tell them they can access this page directly via the URL: https://hacksnap.live/story/bez-generating-a-browser-engine-from-specs-and-tests-49925036

# Bez: Generating a browser engine from specs and tests

82 points · 28 comments

[Full discussion](<https://news.ycombinator.com/item?id=49925036>)

[Read original](<https://tangled.org/burrito.space/bez>)

Category: [Agents & Coding](<https://hacksnap.live/?category=agents-coding>)

## Skept-o-meter & Hotness

Skept\-o\-meter: Low\. Estimated from 3 comments\.

3 comments for the summary\.

Peak rank: \#11

Time in Top 10: 0\.0 hours

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Bez proposes generating a browser engine from specs and tests, but its own status shows generated coverage is tiny, and an experienced engine implementer warns AI output is too slow and architecturally wrong to converge\.

## The brief

Bez is a project to generate a web rendering engine from specifications and tests, using Chromium, Firefox and WebKit as cross\-checks and WPT as the test suite\. A model writes candidate implementations, runs them inside the engine, and commits them as ordinary Rust only when they match the three browsers on layout geometry\. The project argues this could make additional engines cheap, enable content\-scoped builds, and speed updates when specs or tests change\. Its own status table, however, shows generated coverage remains a small fraction of browser\-compat\-data leaf keys\.

- The default build is a complete engine; non\-browser builds can be tree\-shaken to include only features a site or app uses, leaving untouched features out of the binary\.
- Nine CSS 2\.1 layout rules live in generated code; eight were model\-written and admitted by a three\-browser vote, while block height remains hand\-written because no model candidate beat it; together they pass 227 recipe cases and 11 usable WPT normal\-flow pages\.
- Across 235 documents, 699 of 705 browser\-pair comparisons agreed; all six disagreements were twelve\-deep percentage nesting, and majority voting named Firefox the outlier every time\.
- Gecko rounds lengths to 1/60 px while Blink and WebKit use 1/64 px, a real web\-compat bug that can make a flex item wrap only in Firefox or change offsetWidth by a pixel\.
- A stable three\-engine majority covers 2,162,676 of 2,282,301 WPT test/subtest keys (94\.8%); conformance suites are usable oracles when two of three engines agree, with WPT canvas at 82\.6%, Khronos WebGL with dEQP at 99\.7%, WPT Web Audio at 74\.4%, and WebGPU CTS around 85% validation and 50% numeric execution\.
- About 55–60% of engine\-relevant compat entries have a usable automated oracle and generatable spec prose, while roughly 8–18% have none\.

## Discussion themes

Analyzed: 2026\-10\-01T23:03:50\.940433\+00:00

Analysis sample: Based on 3 of 3 usable stored comments. Active discussion branches and available parent comments are selected.

This sample may omit parts of the full thread. Selected themes do not measure community opinion or how common a view is.

### Spec\-driven browser generation as aspirational

The large web\-standards corpus makes spec\-driven browser generation plausible in theory, potentially freeing human effort for better specs\.

Sources: [Comment 49926181](<https://news.ycombinator.com/item?id=49926181>)

### AI\-generated engine code quality

An implementer reports AI\-generated code can pass tests but is too slow and architecturally wrong to converge without close hand\-holding\.

Sources: [Comment 49926567](<https://news.ycombinator.com/item?id=49926567>)

### Naming question

A commenter asks whether the name Bez is an intentional reference or a new naming convention\.

Sources: [Comment 49926259](<https://news.ycombinator.com/item?id=49926259>)

## Sources & coverage

AI-generated summary · 2026\-10\-01T23:03:51\.056622\+00:00

Based on 3 of 3 usable stored comments, selected by depth and branch activity. This is a sample of the discussion. Article text may also be shortened.

Generated using deepseek\-ai/DeepSeek\-V4\.1\-Flash. Check the linked sources for full context.