Gap 6 closed. _is_opaque has a fourth branch for host labels and path
segments of 8-19 chars (calibration.URL_SHORT_B64_MIN_LEN). It fires when
the token is alphanumeric, not 1 mod 4, not itself a word, and its base64
plaintext reads as text: only letters, digits, space and . , : @ _ - + / !
? ' =, at least 80% letters/digits/spaces (URL_SHORT_B64_TEXT_SHARE), and
no lowercase-to-uppercase seam. 
is now HIGH; a link with it MEDIUM.
"Printable" alone fired on Pygments, a Norwegian path word and a JSON size
parameter. Each condition removes a measured twin (Pygments, aktuelle,
Slovenly, {"w":200}, PT00M01S, endsWith). Measured before building, with
the shipped tokenizer: 0 of 22,725 URLs in the 3,583 clean documents and
577 package READMEs, 0 of 530,625 dictionary words, 9 of 336,122
identifiers and prose tokens (all real base64 of text). Recall 32 of 35.
Measured before and after on the same trees: all 4,160 documents are
byte-identical under both presets (disposition, labels, severity, count,
offset); OKF import stays 47/31; positive control WARN -> FAIL_SECURE.
is_ordinary_url about 4 us slower per URL; 1M-char worst case unchanged.
26 new tests (attacks red first), 11 of 11 mutations red. Matrix 147/147 +
4/4 gaps, suite 1300 passed, ReDoS sweep 173 patterns, 0 flags on the new.
Three consumers reconstructed is_ordinary_url from prose we sent in coordination
messages and each produced a different wrong number on a real corpus: one omitted
the base64 20-char floor and fired on path words like /blog/; one omitted the
opaque-token condition entirely and undercounted; one computed Shannon entropy
over whole filenames instead of tokens and concluded the 4.4 floor over-blocks
ordinary documents. Same cause each time -- our prose described the rules without
their tokenizer.
docs/URL-SHAPE.md states the algorithm in order, spells out the separator class
and all three length floors, and lists the three reconstruction errors as worked
counter-examples. Its example table is parsed and asserted against the real
predicate by tests/test_url_shape_doc.py, so the reference cannot drift from the
code -- all 18 rows verified load-bearing.
LIMITATIONS.md brought current with the field measurements:
- Percent-escape is no longer zero. Two English corpora measured 0; a 389-file
Norwegian/Microsoft corpus found 10, all Norwegian (%C3%B8, %C3%A5 are just
o-slash and a-ring). It is a non-ASCII-language tax, and both zero-measuring
corpora being English was a sampling bias invisible from inside.
- The query over-block now has THREE disjoint benign populations: utm_* tracking,
content identity (?v=, ?channel_id=), and Microsoft Learn's ?view= version
selector. No parameter-level remedy covers any two, which moves this from a
conclusion to a settled constraint on 0.4.0.
- Legitimate CDN asset ids trip the hex branch permanently; the branch is otherwise
precise (no other FP in 2401 distinct URLs) and stays.
- Raw HTML with a relative URL attribute is HIGH though it reaches no external
host, and end tags are counted.
- OKF frontmatter: a one-key block-sequence item is silently misparsed to a string
where two keys hard-reject, so a pointer can ride past the resource allowlist.
Consequence: a conformant OKF v0.2 concept cannot traverse door C at all, since
both backward-breaking migration targets are nested. Fail-secure, but a
compatibility wall that needs a deliberate parse-safety decision.
- A persist gate cannot cover execution risk, and that boundary is unowned.
New behaviour claims are pinned by tests so a closed concession fails and forces
this doc to be updated. 593 -> 631 passed.
