cameronrye/openzim-mcp

Post-b3 sweep packaged from PR #169 (commit f69db46). ONE pre-existing
defect surfaced by deeper live-MCP probing of the tell me about X's Y
shape — the attack surface b2 D3 partially closed. All six post-b2 fix
families verified clean on live MCP first (D1-D4 + the pass-2/pass-3
siblings).

Defect — X's Y auto-fetch silent-wrong-answer

_promote_topic_via_title_index (simple_tools.py:3868) iterates trailing
tails via iter_query_tails (title_promotion.py:191). iter_query_tails
tokenizes on alphanumeric runs, so the apostrophe in X's Y is treated
as a separator. The topic "einstein's theory" becomes the tokens
["einstein", "s", "theory"]; tails yielded longest-first:

• "einstein s theory" — no canonical match (the canonical is stored
  WITH the apostrophe — Einstein's_theory is a redirect to
  Theory_of_relativity)
• "s theory" — no canonical match
• "theory" — matches the generic Theory article at score 1.0 →
  wins → wrong article fetched

Live impact (post-b3 live probe):

• tell me about Einstein's theory → Theory (expected
  Theory_of_relativity — confirmed canonical at 1.00 via
  find article titled einstein's theory)
• tell me about Plato's cave → Cave (expected
  Allegory_of_the_cave — confirmed at 1.00)
• tell me about Plato's Republic → Republic (expected
  Republic_(Plato) — confirmed at 0.95)
• tell me about Darwin's evolution → Evolution

The bug is pre-existing — it would have affected any user typing tell me about X's Y for years — but was masked because:

• Pre-b1, fuzzy-search rescues at search time often surfaced the right
  article through different ranking paths.
• Pre-b2 D3, the retry that exposes the probe gate's True/False
  decision didn't exist.
• The specific repros (Einstein's theory, Plato's cave/Republic)
  weren't in the prior adversarial set.

Why b2 D3 doesn't catch this: D3's probe gate correctly suppresses
decomposition when title_probe(topic) finds a canonical (because
Einstein's_theory redirects to Theory_of_relativity at score 1.0).
So topic stays as einstein's theory → the buggy old auto-fetch flow
runs → wrong tail wins. The defect is in the older auto-fetch flow's
tail-iteration, not in the b2 D3 retry.

Fix

Probe the FULL topic (with original punctuation preserved) BEFORE
entering the tail iteration in _promote_topic_via_title_index.
find_title_match uses libzim's title index directly — it correctly
handles apostrophes and redirects. The new probe uses min_score=0.95
to mirror the canonical-or-fuzzy gate Rule 2/3/4 already use
(intent_parser.py:317), accepting both direct hits (1.0) and
high-confidence redirects (0.95). Live verification of the threshold:
find article titled returns score 1.00 for Einstein's theory /
Plato's cave; score 0.95 for Plato's Republic. All three need the 0.95
gate.

Non-possessive queries hit this new probe with the same behavior they'd
get from pass-1's longest tail — the call returns redundantly on those,
never less correct. The pre-existing prose-query case (famous people from big rapids michigan) still falls through to tail iteration
cleanly because the prose phrase isn't itself canonical.

Tests

9 new tests in tests/test_post_b3_beta_fixes.py across 3 classes:

• TestPossessiveAutofetchProbe — verifies the full-topic probe fires
  first, uses min_score=0.95, runs before tail iteration, falls
  through cleanly on no-canonical, and preserves the apostrophe in the
  probed topic.
• TestPossessivePromoteIntegration — three end-to-end-shaped tests
  covering the live repros (Einstein's theory → Theory_of_relativity;
  Plato's cave → Allegory_of_the_cave; Plato's Republic →
  Republic_(Plato) at the 0.95 threshold).
• TestRegressionGuards — structural guard pinning that the first
  find_title_match call inside the method must use the bare topic
  argument (not a tail/window form).

Full suite: 2369 passing, 54 skipped. mypy clean across 52 source
files. black + flake8 clean. All 14 CI checks pass.

Methodology evolution

• "Fix unlocks new paths" — now 10 sweeps strong. Classic shape:
  b1 P1-D5 made Photosythesis's reproduction REACH the auto-fetch
  path; b2 D3 added the possessive retry to fix the immediate
  silent-wrong-answer; the post-b3 sweep's live probing of MORE
  possessive shapes (Einstein's theory, Plato's Republic, Plato's
  cave) revealed that the underlying auto-fetch flow has a
  tokenization bug for possessives where the full phrase is a
  canonical REDIRECT to a different article. Each sweep peels back
  another layer.
• Single-defect sweep. All eight b2 fix families + b3 sweep's
  three passes (b3 D1, pass-2 sibling, pass-3 sibling) verified
  clean on live MCP. The adversarial set was clean. The defect
  surfaced only via deeper probing of one specific query shape.
  Reinforces the post-a17 methodology refinement: "live re-probe
  is mandatory after deploy" — the auto-fetch tokenization bug
  is structurally invisible to unit tests but trivially visible
  to live-MCP probing of the right query shape.