Note: This is another in my sequence of post-Mystery-Hunt cryptics, which started with "Still There," "Post-Game Predictions," "The Sequel," "Power Lines," "A Lesson in Cryptography," "Yet More Villainy," "Further Escapades," "Time X*X," "Honeymoon in Segas," "If At First You Succeed," "Another One From The Vault," "Next Winter: Wonderland," "DAB," "Some Extraction on the Side," "Another Campaign," "Mind The Sharp Bits!", "Through The Wood," "Newbie Toonie," and "Tomezone"; this one was written before the 2024 hunt and refers to (inter alia) the 2023 hunt.

Nearly a year after those old AIs added their enhancements to the museum, two more issues have come up:

(A) One more AI has been found, but it's hard to get it working because it's in an old FORmula TRANslation language. This AI shortens ten two-word or compound-word answers before entry, combining the answer's first part's start with its second part's start, end, or entirety. (One altered entry is a two-word phrase.) In each case, if the answer's parts have lengths p and q in order, note the clue's (i) pth letter from the start and (ii) qth letter from the end; in clue order, the (i) letters and (separately) the (ii) letters will give two descriptions of the AI.

(B) The museum has a lot of valuable artifacts from other times that could easily be stolen. Correspondingly:

1. Each of fourteen Across clues has an extra word that must be stolen before solving. In clue order, the last letters of these words will name a group that previously succeeded at banditry of this kind.
2. In each Across clue not yet used, and each Room clue, the wordplay yields one extra letter, which must be stolen before solving; in clue order, these letters will say when the above banditry happened.

Fortunately, (B) provides a solution to (A)! Specifically:

(C) Each (B1) clue corresponds to one of the four Rooms in the grid; left to right by Room, these clues have:

1. (Science Center) Answers each of which is about space.
2. (Art Gallery) Cryptic readings involving a sort of ars magna.
3. (Natural History Collection) Answers with two valuable specimens, worth 3 or 4 each.
4. (World History Hall) Cryptic readings involving looking back.

If such a clue's nth word is extra, change the row-n letter in the corresponding Room (shaded grid column) to the extra word's last letter. Once all these changes are made, you can (maintaining 180° grid symmetry) replace the two bars in each Room with only one bar, separating two one- or two-word phrases. The letter-changes will also alter all of (B2)'s Across answers (six resulting Across entries will be capitalized, foreign, and/or abbreviated).

1. (B1)'s extra clue words, in clue order, can be grouped into straight clues of 1–3 words for the altered Across entries (C) creates (in an arbitrary order). For each such altered entry in grid order, read the initial letters of the 1–3 (B1) clues yielding the words in its straight clue, to see how to get the AI working.
2. (B2)'s Across and Room clues, in clue order, contain straight clues (of 1–9 words) for, respectively, the Room entries (C) creates (in Room order) and (A)'s altered entries (in clue order); if such a straight clue has n words, note the nth letter from (i) the start and (ii) the end of the (B2) clue it is in. In clue order, the (i) letters and (separately) the (ii) letters will form phrases (appropriate to the group and its activities) saying, respectively, what the action from 1 is and what it does to the AI.

ACROSS

2. Narrative or musical element Oscar Levant's last piece provided after minute enclosures
5. Second, Mr. Yastremski, at retro nunnery, shelled red-flowered bean (2 wds.)
10. Castle containing key U-, E-, H-, or J-shaped object a first responder employs (2 wds.)
11. Slangy, clipped way to say a rug is what a youngster at a school gym might make
13. Transylvanian from Young Frankenstein of Georgia following wain that's abandoned area
14. Awfully dire trio of Francophone Swiss people
16. Note penned by physician describes an oddly outspoken equine government (2 wds., abbr.)
17. From subpar college tintype you can extract the first section (2 wds.)
19. Old instrument outside of Antipodic roadhouse became bisected
22. Scratch OK currency once used in Lübeck
24. Flip fauna Gabor had to show Bautista
25. Upsettingly, one record depicts Michael from The Martian and The Vatican Picnic's Tapes
26. Duo opening one soliloquy behind multitude's heads
28. Remarkable lama Mahler, who wed playwright Franz and playwright Walter after Gustav
30. Tan E has turned cool color
31. Not very calmly declaim (for example) "Con noncheapo artist" reflectively
32. Grand, robust Dorothy who in 2000 was seeking treasure Mystery Hunters seek
34. In the looking glass, each perceived Cato the Elder's German clothing
38. Tesla auto that's 60% too short to carry Wisconsin catcher more than once
40. Objects enclosing one mineral lacking carbon and other things (2 wds., abbr.)
41. Doing what needs doing with pond Gotham City unveiled (2 wds.)
42. Moniker by which Hostess has designated a cake or (uh-oh!) ringlet (2 wds.)
43. Organs that detect scent coming from Enos's locality improved
44. Rotating removed resin from Greek symbol that's insufficiently esteemed
45. Plants that shed leaves stranger outside secured (2 wds.)
46. Egg assuages the hunger of Joyce Carol, who wrote a book called Son of the Morning

ROOM

Science Center (shaded column #1)
3. The aforementioned caseless Utahan digitizer in location five
21. Foremost trio of Erlenmeyers that's jarred again disheartened member of the nobility
36. Finally pair English lady with no year-round Mariner or Yank (abbr.)

Art Gallery (shaded column #2)
4. In favor of Massachusetts laws excluding W's official
32. Couple of looms inside good playwright Jonson's theater for playwright Will

Natural History Collection (shaded column #3)
6. Create penny-like sounds Washington put on part of the Web
29. You're pale if you're as pale as one all-beef Italian not filled with (ultimately) tomato

OTHER DOWN

1. Sold excellent carp
2. Dozen-part sequence from Vehement Al's Pacesetting Worlds of Cognitive Theory (2 wds.)
5. Make clothing incorporating Kay's boas
8. Mentioned beast whose ancestors traded two leus for arms (a sword)
9. Middling quartets of tiredest Pomptine lioncels reentering site bottles are returned to (2 wds.)
12. More sophisticated tome of Abraham's father confused Abner
15. Five-zeptosecond description, perhaps, of soft cheese egoless Fisk put lines on or in (2 wds.)
18. I. M. Pei guzzling red in the style of the Belgian beers that are darker and stronger (2 wds.)
20. Belch-suppressing Barbuda neighbor's ignoring Lou's hail
23. Oder begins at the second largest city in Italia
25. Adult films about potassium-10, the Teutonic-Gallic law, and piggish meat (2 wds.)
27. Silly wretches taunt Eleocharis dulcis plant (2 wds.)
33. Say elevated words that praise crystal-filled Baal of stone
35. Sat opposite outwardly Midwestern people
37. Wildebeest's blown the thistle up