[GLD Serializer Benchmark] Python flexbuffers — spec compliance misses

Hi — this is a friendly report from the [GLD Serializer Benchmark](https://github.com/leo-gan/GLD.SerializerBenchmark), an independent multi-language suite that times serializers **and** checks them against the published format specs (RFC 8259, YAML 1.2, …).

We measured **flexbuffers the pin this suite last measured** on **Python**. The suite recorded spec-profile misses for this pin. The catalog is **report-only**: a miss is not a CI failure, and some cases are older or stricter profiles (for example RFC 4627 vs RFC 8259) rather than a crash.

## Compliance results (please start here)

This link opens the live heatmap on **Python** with **flexbuffers** already selected (All standards). Click a scored cell for each FAIL and the cited spec paragraph:

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/#compliance/python/flexbuffers

How the catalog is built, and how to read a FAIL line:

- https://leo-gan.github.io/GLD.SerializerBenchmark/compliance/
- https://leo-gan.github.io/GLD.SerializerBenchmark/compliance/reading-results/

I am not pasting the case list here so you can use the Dashboard (filters, heatmap, and spec links) rather than a static dump.

Optional: one standard family only — `#compliance/python/flexbuffers/json` (or `yaml`, `cbor`, …).

## Benchmark timings (same pin)

The same suite also publishes encode / decode time and payload size for this library on Python:

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/?lang=python&data=document@n=1&mode=bytes#dashboard

Details table (this library pre-selected):

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/?lang=python&ser=flexbuffers&data=document@n=1&mode=bytes#detailed-analytics

That page is the live L1 snapshot, not a claim that one library is “best.”

## Ask

Please look at the Compliance view for **flexbuffers**. If a miss is a real decoder/encoder bug you want to fix, great. If it is an intentional default (accepting NaN, YAML 1.1 bools, …), a short note here is enough — we will keep the catalog as-is unless the library’s documented contract changes.

Thanks for the library.

Start with the Compliance dashboard for Python flexbuffers, click each FAIL cell, and read the linked specification paragraph and the compliance reading guide. Compare each reported miss with the library's documented contract; done means fixing confirmed encoder or decoder bugs, or documenting intentional defaults in the issue.

Written by the indexing model from the issue text.