Format Detection

Detection chooses which transformations can apply; it is not a format validator and does not certify output syntax.

Probe order

The first matching probe wins, in this exact order:

Order	Result	Test
1	JSON	Starts with { or [ after trimming, and json.loads succeeds
2	XML	XML declaration or an XML-looking root outside the known HTML-tag set; no XML parse
3	YAML	YAML indicator pattern, and yaml.safe_load returns a dict/list
4	Markdown	Indicator score reaches two
5	TOML	tomllib.loads returns a nonempty mapping
6	CSV	Sniffed delimiter and at least two nonempty rows with equal width of at least two columns
7	Text	Fallback, including empty/whitespace-only input

Markdown scores two for multiple heading levels, two for a pipe table with separator, one for a heading level, one for a pair of recognized backtick-fence lines, and one for a Markdown link. A single heading or fenced block alone may therefore be labelled text.

CSV sniffing considers comma, semicolon, tab, and pipe. XML excludes strings starting with <!, including a leading DOCTYPE; the heuristic does not check balanced tags. Malformed JSON falls through to later probes, rather than automatically receiving the JSON label. JSON scalars are not classified by the initial object/array probe.

Format and transformations

Input	Relevant transformations
JSON objects/arrays	minify, drop_nulls, flatten, tabular, dedup_values_with_refs, round_numbers, strip_quotes
YAML	minify
XML	minify
Markdown	collapse_whitespace, compact_tables, strip_html_comments
Text	collapse_whitespace, strip_html_comments
TOML / CSV	No dedicated compactor; detected to avoid prose whitespace transformations

This table covers ordinary object/array and prose inputs. Some JSON-aware strategies also attempt to parse their text or reuse an available parsed value; they are not all gated solely by the format enum. Detection does not mean a strategy will save tokens. Every candidate still passes the acceptance guard.

Inspect the input label

Python

from axm_smelt import Format, smelt

report = smelt('{"a": 1}')
assert report.format is Format.JSON
print(report.format.value)  # json

The label is retained across transformations. In particular, tabular and strip_quotes can make output invalid JSON without changing report.format. Read the strategy contracts and fidelity limits before deciding whether the result can be passed to another parser.