Theme: "Following Protocol" - Each HTTP error is re-phrased as knight-related:
22. HTTP 504: Knight fails to return to castle before portcullis closes for curfew: GATEWAY TIME OUT.
35. HTTP 403: Knight not approved to embark on second search for the Holy Grail: FORBIDDEN REQUEST.
49. HTTP 419: Knight's squire's apprenticeship no longer in force: PAGE EXPIRED.
80. HTTP 500: Knight fails to tip waitstaff at banquet: SERVER ERROR.
96. HTTP 405: Knight illegally aims for opponent's head during joust: METHOD NOT ALLOWED.
Reveal:
113. Medieval protocol for knights, or an alternate title for this puzzle?: CODE OF CHIVALRY.
I bet D-Otto and Anon-T enjoyed this puzzle. They know all the errors. Thankfully you don't need to know those error messages to solve this grid.
Don't recall seeing such a theme anywhere before. Love the freshness and originality.
Across:
1. Totally wiped: BEAT.
5. College Board exam for jrs.: PSAT.
9. Fondant colorer: DYE. I did not know the meaning of "fondant", cake icing.
12. Dream big: ASPIRE.
18. Roman aqueduct section: ARCH.
19. Active volcano on Sicily: ETNA.
20. Timely benefit: BOON.
21. Bedouin, e.g.: ROAMER. Brave souls, those who live in the Sahara.
25. Soft cotton fabric: MUSLIN.
26. Literary comparisons: SIMILES.
27. Organs that affect balance: EARS. 39. Swab for 27-Across: Q-TIP.
28. Boutonniere counterpart: CORSAGE.
29. Bed cover: DUVET.
30. "Turn up the heat!": BRR. Bill & Margret's new co-op place is toasty. And I feel so safe and loved. Margaret painted these.
31. Fade, say: WEAR.
33. Triangles on a map, typically: Abbr.: MTNS.
34. Flower in some O'Keeffe paintings: IRIS.
40. Snap veggies: PEAS.
41. Sign into law: ENACT.
42. Push notifications: E-ALERTS. Not a word I use. All my notifications are off. I check when I want to check.
43. DOJ staffers: ATTYS.
45. Ryan of "Star Trek: Picard": JERI.
46. Puglia lang.: ITAL. Not familiar with Puglia.
53. Gets fit: SHAPES UP.
57. Routine material: JOKES. Stand-up routine.
58. Store securely: STOW.
59. Blues label based in Memphis: STAX.
60. Icy layer: RIME.
61. "Pressure" singer Lennox: ARI.
62. Tennis unit: SET.
65. Some fossils: TEETH.
67. Citi player: MET. Patti is long-time Mets fan.
69. 16th POTUS: ABE.
70. Baby carrier: WOMB.
72. Spindly: BONY.
74. Villain's hideaway: LAIR.
76. "The Sparks Brothers" director Wright: EDGAR. He often collaborates with Simon Pegg.
78. Commuters' region: SUBURBIA.
83. Meh: SO SO.
84. Lump of soil: CLOD.
86. Finnish tech giant: NOKIA.
87. Lowered a lot, as prices: SLASHED.
90. New cadet: PLEBE.
92. Rowdy crowds: MOBS.
100. French friend: AMIE.
101. Fairy tale meanie: OGRE.
102. White peg in Battleship: MISS.
103. Car port?: AUX. Connection port.
104. Waterfall on a doughnut production line: GLAZE.
105. Fuel mining site: COAL PIT.
107. Angry speech: RANT.
109. Toyota sedan: COROLLA.
112. Suggest: HINT AT.
116. Rise: ASCENT.
117. "Sadly ... ": ALAS.
118. Spark interest?: LEND. Great clue.
119. For a __ pittance: MERE.
120. Hi-fi system: STEREO.
121. Civil rights initialism: BLM. Black Lives Matters.
122. Brouhahas: ADOS.
123. 115-Down votes: AYES. 115. Affirmative: YES.
Down:
2. Error remnant: ERASURE.
3. Probiotic yogurt brand: ACTIVIA.
4. Rap anthem by Grandmaster Flash & the Furious Five: THE MESSAGE. 1982. Another learning moment for me.
5. Ring out: PEAL.
6. Warm compress target, maybe: STYE.
7. Termite eaters: ANTS.
8. Mai __: cocktail: TAI.
9. "Monsters, Inc." factory product: DOOR.
10. "Pinkie promise?": YOU SWEAR. Also 14. Make the grade: PASS MUSTER. 71. Place for a pick-me-up?: BUS SHELTER. 85. "Time to blow this popsicle stand": LET'S ROLL. Excellent entries.
11. Isengard attacker: ENT.
12. Weapons expert: ARMORER.
13. Sweet and __: SOUR.
15. "Better get a move on!": I'M LATE.
16. Royal tenures: REIGNS.
17. "Ready Player One" author Cline: ERNEST.
20. Santa costume need: BEARD.
23. Sharp quality: WIT.
24. Warrant: MERIT.
28. Attention: CARE.
29. Swing dance move: DIP.
30. "The Graham Norton Show" airer: BBC.
32. Recruit: ENLIST.
35. Big bash: FETE.
36. Agate kin: ONYX.
37. Speaks with a sore throat: RASPS.
38. "No good __ goes unpunished": DEED.
44. Model/activist Holliday: TESS.
45. Like tiaras: JEWELED.
47. Parmesan substitute: ASIAGO.
48. __ support: LUMBAR.
49. Like a sponge: POROUS.
50. With hands on hips: AKIMBO.
51. Teensy: ITTY.
52. Fishy topping: ROE.
54. Goofy sort: HAM.
55. Splitting tool: AXE.
56. Coeval: PEER. Is "coeval" a common word?
57. Spielberg shark thriller: JAWS.
59. Sister on "Succession": SHIV. Unknown to me. Happy for the new clue angle.
63. Flow partner: EBB.
64. You, in Montréal: TOI.
66. Driveway-patching gunk: TAR.
68. Actress Hatcher: TERI.
73. Cheesy layered snack: NACHOS.
75. Keep up on the issues?: RENEW.
77. One prone to histrionics, informally: DRAMA LLAMA. Learned from doing crosswords.
79. Hershey caramel candy: ROLO.
80. Faygo or Fanta: SODA. Wikipedia says Faygo is "a soft drink company headquartered in Detroit, Michigan."
81. Get-up on Sunday morning?: ROBE. Sweet clue also.
82. __ out a living: EKED.
88. Come clean about: ADMIT TO.
89. Sulky mood: SNIT.
90. Ninth planet, until 2006: PLUTO.
91. Fishy topping: LOX.
93. Ill-fated "Grey's Anatomy" resident George: O'MALLEY.
94. Nutty: BIZARRE.
95. Match at the poker table: SEE.
96. Coffee-and-chocolate concoctions: MOCHAS.
97. Narcissist: EGOIST.
98. Hypnotic state: TRANCE.
99. Areas of expertise: LANES. Splynter's lane is wide.
104. Sen.'s domain: GOV.
106. Greenhouse unit: PANE.
108. Genesis figure: ADAM.
109. Included in an email thread: CC'ED.
110. "How terrible!": OH NO.
111. Divests (of): RIDS.
113. Uber or Lyft alternative: CAB.
114. Tampa's st.: FLA.
C.C.
I was very sad to learn that Old Man Keith passed away. He was an active member of our blog for so many years. Always a gentleman. You can learn more his life here.