{
  "change": "Two internal rear-cover driver approach reliefs, diameter3mm, constructed by subtraction only.",
  "reconstruction": "Rebuilt from saved pre-relief BRep by the two cuts; final volume, area and face count match. Coincident-solid subtraction produced an invalid result and was not accepted as a set-equivalence test.",
  "removed_volume_mm3": 29.443954154179664,
  "only_changed_manufactured_step": [
    "C27_R2_02_Back_Shell_Chalk.step"
  ],
  "unchanged_manufactured_step_count": 55,
  "rechecked_retention_rows": [
    {
      "component": "PCB",
      "direction": "+X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 1.0129460274987985,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 1.0129460274987985,
      "retention_preserved": true
    },
    {
      "component": "PCB",
      "direction": "-Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 1.4893813503525766,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 1.4893813503525766,
      "retention_preserved": true
    },
    {
      "component": "PCB",
      "direction": "+Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 6.821653980562308,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 6.821653980562308,
      "retention_preserved": true
    },
    {
      "component": "LTE",
      "direction": "-X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 1.6957236963295346,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 1.6957236963295346,
      "retention_preserved": true
    },
    {
      "component": "LTE",
      "direction": "+X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 1.695723696352486,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 1.695723696352486,
      "retention_preserved": true
    },
    {
      "component": "LTE",
      "direction": "-Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.3457248029736875,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.3457248029736875,
      "retention_preserved": true
    },
    {
      "component": "LTE",
      "direction": "+Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.001914336917244493,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.001914336917244493,
      "retention_preserved": true
    },
    {
      "component": "PTT_Switch",
      "direction": "-X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 3.388358375205238,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 3.388358375205238,
      "retention_preserved": true
    },
    {
      "component": "PTT_Switch",
      "direction": "+X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 2.566453248980056,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 2.566453248980056,
      "retention_preserved": true
    },
    {
      "component": "PTT_Switch",
      "direction": "-Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544171621,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544171621,
      "retention_preserved": true
    },
    {
      "component": "PTT_Switch",
      "direction": "+Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544235984,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544235984,
      "retention_preserved": true
    },
    {
      "component": "PTT_Switch",
      "direction": "-Z",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.12000000655616298,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.12000000655616298,
      "retention_preserved": true
    },
    {
      "component": "Volume_Up_Switch",
      "direction": "-X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 2.5664532489318344,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 2.5664532489318344,
      "retention_preserved": true
    },
    {
      "component": "Volume_Up_Switch",
      "direction": "+X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 3.388358375356608,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 3.388358375356608,
      "retention_preserved": true
    },
    {
      "component": "Volume_Up_Switch",
      "direction": "-Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544172956,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544172956,
      "retention_preserved": true
    },
    {
      "component": "Volume_Up_Switch",
      "direction": "+Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544157964,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544157964,
      "retention_preserved": true
    },
    {
      "component": "Volume_Up_Switch",
      "direction": "-Z",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.12000000655616287,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.12000000655616287,
      "retention_preserved": true
    },
    {
      "component": "Volume_Down_Switch",
      "direction": "-X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 2.5664532489318477,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 2.5664532489318477,
      "retention_preserved": true
    },
    {
      "component": "Volume_Down_Switch",
      "direction": "+X",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 3.388358375356618,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 3.388358375356618,
      "retention_preserved": true
    },
    {
      "component": "Volume_Down_Switch",
      "direction": "-Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544173344,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544173344,
      "retention_preserved": true
    },
    {
      "component": "Volume_Down_Switch",
      "direction": "+Y",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.11249993544157795,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.11249993544157795,
      "retention_preserved": true
    },
    {
      "component": "Volume_Down_Switch",
      "direction": "-Z",
      "old_back_contacts": [
        {
          "part": "C27_R2_02_Back_Shell_Chalk",
          "material": "chalk",
          "overlap_mm3": 0.12000000655616287,
          "interpretation": "rigid geometric stop"
        }
      ],
      "current_back_overlap_mm3": 0.12000000655616287,
      "retention_preserved": true
    }
  ],
  "clearance_checks": "Final static and cover checks are rerun after this edit. Control sweep geometry and actual actuators are unchanged; back obstacle is reduced by construction.",
  "access": "Separately rerun final access_and_exterior.json uses the final back.",
  "scope": "Construction verification and affected-contact rechecks, not a physical qualification."
}