Connor's point: "several outlets carried this" covers situations that carry
different amounts of information, and origin_count() flattened them all to one
number. Splitting on same/different newsroom and same/different text gives four
cases:
same newsroom, same text -> pure duplicate (BBC World + BBC top). Zero
signal; the front-page placement it does carry is
already captured by sources.prominence.
same newsroom, diff text -> DEPTH. A newsroom filing four pieces on one story
is a real editorial judgement, previously
discarded entirely.
diff newsroom, same text -> PICKUPS. Syndicated copy; each carrier chose to
run it. Weak but non-zero.
diff newsroom, diff text -> ORIGINS. Independent judgement and independent
newsgathering. Strongest.
score = origins + 0.3*log1p(pickups) + 0.2*log1p(depth), weights in config.
Origins stay dominant; the others break ties among the many two- and
three-origin clusters, and log damping stops a high-volume feed inflating depth.
Measuring first changed the design. Depth outnumbers pickups 78 to 11 across 91
real clusters, because these sources are mostly national outlets writing their
own copy rather than local papers running wire -- so the more valuable half was
the one not originally proposed. UK settlements scores 10.55 from 10 origins
plus 15 same-newsroom pieces; AfD scores 5.55 from 5 origins plus 15.
Tests assert the four-case ordering directly, and that twenty pieces from one
newsroom still rank below two independent ones. Both needed a helper generating
vectors with exact pairwise cosine: the band between the 0.82 clustering
threshold and the 0.97 syndication threshold is narrow, and two earlier drafts
of these tests used ad-hoc vectors that fell outside it and asserted nothing.
Connor's observation: two outlets running the same story can be caught by
comparing the text, without anyone having to know who owns whom.
Corroboration is now origin_count(), a union-find where two items share an
origin if EITHER they are in the same bucket, OR their text is near-identical
(normalised title match, or cosine >= 0.97). The rules are complementary:
buckets are same-owner/different-text (NYT filing five distinct AfD pieces),
text matching is different-owner/same-text (a local station reprinting wire).
On real data it fires exactly where it should: the vote-by-mail cluster
collapses 2 buckets -> 1 origin, catching the States Newsroom syndication
automatically -- the case previously fixed by hand in config -- and a
Smithsonian story collapses 3 -> 2, catching WCPO reprinting wire, which no
static bucket can express since WCPO is genuinely independent on local stories.
The eight Renoir-heist reports, each independently written, correctly stay at 8.
Across 91 multi-item clusters: 174 buckets -> 163 true origins.
Note this is the one place a lexical comparison is right. Clustering fails on
lexical methods because paraphrases share no wording, which is why the SimHash
stage was measured and deleted -- but syndicated copy is literally the same
bytes.
First formulation was wrong and the data caught it: summing syndication groups
and solo buckets produced 3 origins for a 2-bucket cluster. Syndication may only
ever reduce corroboration, which the union-find guarantees and a test asserts.
Reading real clustered output caught a config error the tests could not:
Ohio Capital Journal and Kentucky Lantern are both States Newsroom outlets
syndicating the same national desk, and carried 10 byte-identical headlines in a
single poll -- more than any other source pair. Configured as separate buckets
they would have doubled the corroboration signal on every syndicated story,
which is exactly the failure the bucket concept exists to prevent.
Found by checking identical headlines across all source pairs rather than
spot-fixing the one noticed by eye. That sweep also confirmed the buckets
already set deliberately are right: BBC Top/World, Ars Technica/Science and
NPR News/Politics each share a bucket and each showed shared headlines.
Regression test added.
Pipeline: fetch -> normalise -> embed (CPU) -> cluster. `news poll` runs a
cycle; `news sources` and `news clusters` inspect the result. Replay and the
live service share run_cycle so tuning and production cannot diverge -- the old
system's replay harness hardcoded default params and could never sweep the
thresholds it existed to tune.
Calibrated, not guessed:
- Cluster threshold 0.82, from reading real output. 0.70 merged "Solheim Cup
capsules" with "FIBA Women's World Cup Glance"; 0.82 gives clean groups (76
items on the AfD Saxony-Anhalt election, 27 on the Nepal tunnel rescue). The
old system produced 515 clusters of which 514 were singletons.
- Corroboration counts DISTINCT buckets, not feeds, so ten outlets reprinting
one wire story is one confirmation rather than ten.
Removed after measurement: a SimHash near-duplicate stage. It gave +1.2 bits of
separation on titles and -0.2 with summaries -- news duplicates are paraphrases,
which is the same lexical trap that sank the old Jaccard clustering.
Sources: all 39 fetched against the live web, not assumed. Dropped CBC (every
feed URL times out from this host) and Tech Policy Press (serves HTML at every
documented feed path). Fixed WVXU (index.rss is an empty stub; local-news.rss
works). Reddit moved to .rss because .json now 403s without OAuth, and its
intervals raised because it 429s after three quick requests. Deutsche Welle is
back: it ships RSS 1.0/RDF, which feedparser reads and the old hand-rolled
quick-xml parser could not.
connor