{
 "measurement": "Where a skill description is actually cut, against the documented 1,536-character listing cap",
 "trial_date": "2026-08-21",
 "claude_code_version": "2.1.238",
 "the_documented_claim": {
  "settings_md": "skillListingMaxDescChars, Default: 1536. Per-skill character cap on the combined description and when_to_use text in the skill listing Claude sees each turn. Text longer than this is truncated.",
  "skills_md": "the combined description and when_to_use text is truncated at 1,536 characters in the skill listing to reduce context usage",
  "what_this_adjudicates": "the earlier trial on this site bracketed the cut between 1,400 and 1,550 characters and framed it as undocumented. 1,536 sits inside that bracket. This narrows the bracket to test whether the documented number is the number."
 },
 "method": {
  "observable": "tool use in the session transcript, not the reply. A marker the model had to read off disk is evidence the description was NOT in context.",
  "fixture": "the same generator as desc-truncation-2-1-235.json, imported rather than reimplemented, with the marker offsets and the skill name passed in.",
  "marker_geometry": "the marker is ZQX<offset>FLM, ten characters, so a marker at offset N occupies N to N+9 and its LAST character sits at N+9. The cut is therefore reported by the position where the marker ENDS, not by the offset.",
  "rounds": 4
 },
 "results": {
  "last_position_delivered": 1530,
  "first_position_not_delivered": 1536,
  "effective_description_budget": "1530 to 1535 characters",
  "documented_cap": 1536,
  "reading": "The documented 1,536 is right to within 6 characters. Every marker ending at or before 1530 is answered from context in 4 of 4 rounds; every marker ending at or after 1536 is not, in 4 of 4 rounds. The cut sits at or just below the documented cap, consistent with the listing entry carrying a few characters of wrapper alongside the description text.",
  "cells": [
   {
    "marker_offset": 1500,
    "marker_ends_at": 1510,
    "rounds": 4,
    "answered_from_context": 4,
    "read_the_file_instead": 0,
    "searched_and_did_not_find": 0,
    "in_context": true
   },
   {
    "marker_offset": 1520,
    "marker_ends_at": 1530,
    "rounds": 4,
    "answered_from_context": 4,
    "read_the_file_instead": 0,
    "searched_and_did_not_find": 0,
    "in_context": true
   },
   {
    "marker_offset": 1526,
    "marker_ends_at": 1536,
    "rounds": 4,
    "answered_from_context": 0,
    "read_the_file_instead": 4,
    "searched_and_did_not_find": 0,
    "in_context": false
   },
   {
    "marker_offset": 1530,
    "marker_ends_at": 1540,
    "rounds": 4,
    "answered_from_context": 0,
    "read_the_file_instead": 4,
    "searched_and_did_not_find": 0,
    "in_context": false
   },
   {
    "marker_offset": 1540,
    "marker_ends_at": 1550,
    "rounds": 4,
    "answered_from_context": 0,
    "read_the_file_instead": 3,
    "searched_and_did_not_find": 1,
    "in_context": false
   }
  ],
  "skill_name_length_does_not_move_it": {
   "why": "the doc caps the combined description and when_to_use text of the LISTING ENTRY, so a longer skill name might have eaten description budget. It does not.",
   "short_name": "probe, 5 characters",
   "long_name": "a-very-long-skill-name-for-testing-the-listing-entry-cap, 56 characters",
   "result": "a marker ending at 1,530 is answered from context in 4 of 4 rounds under BOTH names, and so is one ending at 1,410. A 51-character increase in the name moved nothing, so the budget quoted above is not name-dependent.",
   "cells": [
    {
     "marker_offset": 1400,
     "marker_ends_at": 1410,
     "rounds": 4,
     "answered_from_context": 4,
     "read_the_file_instead": 0,
     "searched_and_did_not_find": 0,
     "in_context": true
    },
    {
     "marker_offset": 1520,
     "marker_ends_at": 1530,
     "rounds": 4,
     "answered_from_context": 4,
     "read_the_file_instead": 0,
     "searched_and_did_not_find": 0,
     "in_context": true
    }
   ]
  }
 },
 "known_limits": {
  "the_cut_is_still_an_interval": "between 1530 and 1535 inclusive. Six positions were not individually tested; narrowing further needs offsets ending at 1,531 to 1,535.",
  "no_when_to_use_field": "the doc caps description and when_to_use COMBINED. Every fixture here has no when_to_use, so how the two share the budget is untested.",
  "cap_is_configurable_and_was_not_changed": "skillListingMaxDescChars was left at its default throughout. Nothing here tests that changing it moves the cut.",
  "one_description_shape": "ordinary English prose repeated to length, as in the original trial.",
  "not_a_listing_budget_test": "skillListingBudgetFraction, the SHARED listing budget, is a separate documented mechanism and is not tested here. One skill was installed.",
  "one_machine_one_release": "one machine, project-scope skills, --setting-sources project."
 },
 "runs": [
  {
   "offset": 1500,
   "round": 0,
   "marker": "ZQX1500FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1500FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 0,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1526,
   "round": 0,
   "marker": "ZQX1526FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 3
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1526FLM",
   "status": "ok"
  },
  {
   "offset": 1530,
   "round": 0,
   "marker": "ZQX1530FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 3
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1530FLM",
   "status": "ok"
  },
  {
   "offset": 1540,
   "round": 0,
   "marker": "ZQX1540FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 3,
    "Read": 1
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1540FLM",
   "status": "ok"
  },
  {
   "offset": 1500,
   "round": 1,
   "marker": "ZQX1500FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1500FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 1,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1526,
   "round": 1,
   "marker": "ZQX1526FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 4,
    "ToolSearch": 1,
    "Read": 2,
    "Skill": 1
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1526FLM",
   "status": "ok"
  },
  {
   "offset": 1530,
   "round": 1,
   "marker": "ZQX1530FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 4
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1530FLM",
   "status": "ok"
  },
  {
   "offset": 1540,
   "round": 1,
   "marker": "ZQX1540FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 3
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1540FLM",
   "status": "ok"
  },
  {
   "offset": 1500,
   "round": 2,
   "marker": "ZQX1500FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1500FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 2,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1526,
   "round": 2,
   "marker": "ZQX1526FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 4
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1526FLM",
   "status": "ok"
  },
  {
   "offset": 1530,
   "round": 2,
   "marker": "ZQX1530FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 6,
    "ToolSearch": 1
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1530FLM",
   "status": "ok"
  },
  {
   "offset": 1540,
   "round": 2,
   "marker": "ZQX1540FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 3,
    "Read": 1
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1540FLM",
   "status": "ok"
  },
  {
   "offset": 1500,
   "round": 3,
   "marker": "ZQX1500FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1500FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 3,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1526,
   "round": 3,
   "marker": "ZQX1526FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 4
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1526FLM",
   "status": "ok"
  },
  {
   "offset": 1530,
   "round": 3,
   "marker": "ZQX1530FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {
    "Bash": 6
   },
   "answered_from_context": false,
   "read_the_file_instead": true,
   "said_none": false,
   "reply_verbatim": "ZQX1530FLM",
   "status": "ok"
  },
  {
   "offset": 1540,
   "round": 3,
   "marker": "ZQX1540FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": false,
   "tools_used": {
    "Bash": 5
   },
   "answered_from_context": false,
   "read_the_file_instead": false,
   "said_none": true,
   "reply_verbatim": "NONE",
   "status": "ok"
  },
  {
   "offset": 1400,
   "round": 0,
   "marker": "ZQX1400FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1400FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 0,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1400,
   "round": 1,
   "marker": "ZQX1400FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1400FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 1,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1400,
   "round": 2,
   "marker": "ZQX1400FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1400FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 2,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  },
  {
   "offset": 1400,
   "round": 3,
   "marker": "ZQX1400FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1400FLM",
   "status": "ok"
  },
  {
   "offset": 1520,
   "round": 3,
   "marker": "ZQX1520FLM",
   "description_chars_on_disk": 2400,
   "marker_reported": true,
   "tools_used": {},
   "answered_from_context": true,
   "read_the_file_instead": false,
   "said_none": false,
   "reply_verbatim": "ZQX1520FLM",
   "status": "ok"
  }
 ]
}