diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 2575b04530..bf274ec823 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -149,7 +149,7 @@ module Cask
         return []
       end
 
-      latest_version = if ENV["HOMEBREW_JSON_CORE"].present? &&
+      latest_version = if ENV["HOMEBREW_INSTALL_FROM_API"].present? &&
                           (latest_cask_version = Homebrew::API::Versions.latest_cask_version(token))
         DSL::Version.new latest_cask_version.to_s
       else
diff --git a/Library/Homebrew/cli/named_args.rb b/Library/Homebrew/cli/named_args.rb
index 7ef5b5a695..19d6c07799 100644
--- a/Library/Homebrew/cli/named_args.rb
+++ b/Library/Homebrew/cli/named_args.rb
@@ -94,7 +94,7 @@ module Homebrew
         unreadable_error = nil
 
         if only != :cask
-          if prefer_loading_from_api && ENV["HOMEBREW_JSON_CORE"].present? &&
+          if prefer_loading_from_api && ENV["HOMEBREW_INSTALL_FROM_API"].present? &&
              Homebrew::API::Bottle.available?(name)
             Homebrew::API::Bottle.fetch_bottles(name)
           end
@@ -133,7 +133,7 @@ module Homebrew
         end
 
         if only != :formula
-          if prefer_loading_from_api && ENV["HOMEBREW_JSON_CORE"].present? &&
+          if prefer_loading_from_api && ENV["HOMEBREW_INSTALL_FROM_API"].present? &&
              Homebrew::API::CaskSource.available?(name)
             contents = Homebrew::API::CaskSource.fetch(name)
           end
diff --git a/Library/Homebrew/cmd/info.rb b/Library/Homebrew/cmd/info.rb
index fec292ee77..46819f606c 100644
--- a/Library/Homebrew/cmd/info.rb
+++ b/Library/Homebrew/cmd/info.rb
@@ -244,7 +244,7 @@ module Homebrew
   def info_formula(f, args:)
     specs = []
 
-    if ENV["HOMEBREW_JSON_CORE"].present? && Homebrew::API::Bottle.available?(f.name)
+    if ENV["HOMEBREW_INSTALL_FROM_API"].present? && Homebrew::API::Bottle.available?(f.name)
       info = Homebrew::API::Bottle.fetch(f.name)
 
       latest_version = info["pkg_version"].split("_").first
diff --git a/Library/Homebrew/cmd/outdated.rb b/Library/Homebrew/cmd/outdated.rb
index e6999fd641..7d46a5ec06 100644
--- a/Library/Homebrew/cmd/outdated.rb
+++ b/Library/Homebrew/cmd/outdated.rb
@@ -98,7 +98,7 @@ module Homebrew
         if verbose?
           outdated_kegs = f.outdated_kegs(fetch_head: args.fetch_HEAD?)
 
-          current_version = if ENV["HOMEBREW_JSON_CORE"].present? && (f.core_formula? || f.tap.blank?)
+          current_version = if ENV["HOMEBREW_INSTALL_FROM_API"].present? && (f.core_formula? || f.tap.blank?)
             Homebrew::API::Versions.latest_formula_version(f.name)&.to_s || f.pkg_version.to_s
           elsif f.alias_changed? && !f.latest_formula.latest_version_installed?
             latest = f.latest_formula
diff --git a/Library/Homebrew/cmd/reinstall.rb b/Library/Homebrew/cmd/reinstall.rb
index 791b299ed3..08e197b5e3 100644
--- a/Library/Homebrew/cmd/reinstall.rb
+++ b/Library/Homebrew/cmd/reinstall.rb
@@ -88,7 +88,7 @@ module Homebrew
     # We need to use the bottle API instead of just using the formula file
     # from an installed keg because it will not contain bottle information.
     # As a consequence, `brew reinstall` will also upgrade outdated formulae
-    if ENV["HOMEBREW_JSON_CORE"].present?
+    if ENV["HOMEBREW_INSTALL_FROM_API"].present?
       args.named.each do |name|
         formula = Formulary.factory(name)
         next unless formula.any_version_installed?
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index 02ba88f316..6e076bba81 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -25,7 +25,7 @@ module Homebrew
     args = untap_args.parse
 
     args.named.to_installed_taps.each do |tap|
-      odie "Untapping #{tap} is not allowed" if tap.core_tap? && ENV["HOMEBREW_JSON_CORE"].blank?
+      odie "Untapping #{tap} is not allowed" if tap.core_tap? && ENV["HOMEBREW_INSTALL_FROM_API"].blank?
 
       installed_tap_formulae = Formula.installed.select { |formula| formula.tap == tap }
       installed_tap_casks = Cask::Caskroom.casks.select { |cask| cask.tap == tap }
diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index 752b4008e9..392a799965 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -102,7 +102,7 @@ module Homebrew
     updated_taps = []
     Tap.each do |tap|
       next unless tap.git?
-      next if tap.core_tap? && ENV["HOMEBREW_JSON_CORE"].present? && args.preinstall?
+      next if tap.core_tap? && ENV["HOMEBREW_INSTALL_FROM_API"].present? && args.preinstall?
 
       begin
         reporter = Reporter.new(tap)
@@ -208,7 +208,7 @@ module Homebrew
 
   def install_core_tap_if_necessary
     return if ENV["HOMEBREW_UPDATE_TEST"]
-    return if ENV["HOMEBREW_JSON_CORE"].present?
+    return if ENV["HOMEBREW_INSTALL_FROM_API"].present?
 
     core_tap = CoreTap.instance
     return if core_tap.installed?
diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index 4c7918ab39..a062c8edb5 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -498,7 +498,7 @@ EOS
 
   for DIR in "${HOMEBREW_REPOSITORY}" "${HOMEBREW_LIBRARY}"/Taps/*/*
   do
-    if [[ -n "${HOMEBREW_JSON_CORE}" ]] && [[ -n "${HOMEBREW_UPDATE_PREINSTALL}" ]] &&
+    if [[ -n "${HOMEBREW_INSTALL_FROM_API}" ]] && [[ -n "${HOMEBREW_UPDATE_PREINSTALL}" ]] &&
        [[ "${DIR}" = "${HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-core" ]]
     then
       continue
@@ -647,7 +647,7 @@ EOS
   do
     # HOMEBREW_UPDATE_PREINSTALL wasn't modified in subshell.
     # shellcheck disable=SC2031
-    if [[ -n "${HOMEBREW_JSON_CORE}" ]] && [[ -n "${HOMEBREW_UPDATE_PREINSTALL}" ]] &&
+    if [[ -n "${HOMEBREW_INSTALL_FROM_API}" ]] && [[ -n "${HOMEBREW_UPDATE_PREINSTALL}" ]] &&
        [[ "${DIR}" = "${HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-core" ||
           "${DIR}" = "${HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-cask" ]]
     then
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index c673975f63..6c1c8a1427 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -160,7 +160,7 @@ module Homebrew
       puts pinned.map { |f| "#{f.full_specified_name} #{f.pkg_version}" } * ", "
     end
 
-    if ENV["HOMEBREW_JSON_CORE"].present?
+    if ENV["HOMEBREW_INSTALL_FROM_API"].present?
       formulae_to_install.map! do |formula|
         next formula if formula.tap.present? && !formula.core_formula?
         next formula unless Homebrew::API::Bottle.available?(formula.name)
@@ -225,7 +225,7 @@ module Homebrew
   def upgrade_outdated_casks(casks, args:)
     return false if args.formula?
 
-    if ENV["HOMEBREW_JSON_CORE"].present?
+    if ENV["HOMEBREW_INSTALL_FROM_API"].present?
       casks = casks.map do |cask|
         next cask if cask.tap.present? && cask.tap != "homebrew/cask"
         next cask unless Homebrew::API::CaskSource.available?(cask.token)
diff --git a/Library/Homebrew/extend/os/mac/tap.rb b/Library/Homebrew/extend/os/mac/tap.rb
index d2e5b89212..d88902a1d3 100644
--- a/Library/Homebrew/extend/os/mac/tap.rb
+++ b/Library/Homebrew/extend/os/mac/tap.rb
@@ -4,7 +4,7 @@
 class Tap
   def self.install_default_cask_tap_if_necessary(force: false)
     return false if default_cask_tap.installed?
-    return false if ENV["HOMEBREW_JSON_CORE"].present?
+    return false if ENV["HOMEBREW_INSTALL_FROM_API"].present?
     return false if !force && Tap.untapped_official_taps.include?(default_cask_tap.name)
 
     default_cask_tap.install
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index f55ca41444..ffa5520f10 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -520,7 +520,7 @@ class Formula
   # exists and is not empty.
   # @private
   def latest_version_installed?
-    latest_prefix = if ENV["HOMEBREW_JSON_CORE"].present? &&
+    latest_prefix = if ENV["HOMEBREW_INSTALL_FROM_API"].present? &&
                        (latest_pkg_version = Homebrew::API::Versions.latest_formula_version(name))
       prefix latest_pkg_version
     else
@@ -1340,7 +1340,7 @@ class Formula
     Formula.cache[:outdated_kegs][cache_key] ||= begin
       all_kegs = []
       current_version = T.let(false, T::Boolean)
-      latest_version = if ENV["HOMEBREW_JSON_CORE"].present? && (core_formula? || tap.blank?)
+      latest_version = if ENV["HOMEBREW_INSTALL_FROM_API"].present? && (core_formula? || tap.blank?)
         Homebrew::API::Versions.latest_formula_version(name) || pkg_version
       else
         pkg_version
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 3a54b0465f..dc88595f48 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -361,7 +361,9 @@ module Formulary
     end
 
     def get_formula(*)
-      raise CoreTapFormulaUnavailableError, name if !CoreTap.instance.installed? && ENV["HOMEBREW_JSON_CORE"].present?
+      if !CoreTap.instance.installed? && ENV["HOMEBREW_INSTALL_FROM_API"].present?
+        raise CoreTapFormulaUnavailableError, name
+      end
 
       raise FormulaUnavailableError, name
     end
@@ -397,7 +399,7 @@ module Formulary
   )
     raise ArgumentError, "Formulae must have a ref!" unless ref
 
-    if ENV["HOMEBREW_JSON_CORE"].present? &&
+    if ENV["HOMEBREW_INSTALL_FROM_API"].present? &&
        @formula_name_local_bottle_path_map.present? &&
        @formula_name_local_bottle_path_map.key?(ref)
       ref = @formula_name_local_bottle_path_map[ref]
@@ -429,7 +431,9 @@ module Formulary
   # @param formula_name the formula name string to map.
   # @param local_bottle_path a path pointing to the target bottle archive.
   def self.map_formula_name_to_local_bottle_path(formula_name, local_bottle_path)
-    raise UsageError, "HOMEBREW_JSON_CORE not set but required for #{__method__}!" if ENV["HOMEBREW_JSON_CORE"].blank?
+    if ENV["HOMEBREW_INSTALL_FROM_API"].blank?
+      raise UsageError, "HOMEBREW_INSTALL_FROM_API not set but required for #{__method__}!"
+    end
 
     @formula_name_local_bottle_path_map ||= {}
     @formula_name_local_bottle_path_map[formula_name] = Pathname(local_bottle_path).realpath
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 810a9ea474..6aba948771 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -735,7 +735,7 @@ class CoreTap < Tap
 
   def self.ensure_installed!
     return if instance.installed?
-    return if ENV["HOMEBREW_JSON_CORE"].present?
+    return if ENV["HOMEBREW_INSTALL_FROM_API"].present?
 
     safe_system HOMEBREW_BREW_FILE, "tap", instance.name
   end
@@ -752,7 +752,7 @@ class CoreTap < Tap
   # @private
   sig { params(manual: T::Boolean).void }
   def uninstall(manual: false)
-    raise "Tap#uninstall is not available for CoreTap" if ENV["HOMEBREW_JSON_CORE"].blank?
+    raise "Tap#uninstall is not available for CoreTap" if ENV["HOMEBREW_INSTALL_FROM_API"].blank?
 
     super
   end
diff --git a/Library/Homebrew/test/api/bottle_spec.rb b/Library/Homebrew/test/api/bottle_spec.rb
index 17f9b1a066..8b98ae772e 100644
--- a/Library/Homebrew/test/api/bottle_spec.rb
+++ b/Library/Homebrew/test/api/bottle_spec.rb
@@ -64,7 +64,7 @@ describe Homebrew::API::Bottle do
 
   describe "::fetch_bottles" do
     before do
-      ENV["HOMEBREW_JSON_CORE"] = "1"
+      ENV["HOMEBREW_INSTALL_FROM_API"] = "1"
       allow(described_class).to receive(:fetch).and_return bottle_hash
     end
 
diff --git a/Library/Homebrew/test/formulary_spec.rb b/Library/Homebrew/test/formulary_spec.rb
index 7370a04d13..7b5825cbb5 100644
--- a/Library/Homebrew/test/formulary_spec.rb
+++ b/Library/Homebrew/test/formulary_spec.rb
@@ -216,12 +216,12 @@ describe Formulary do
         described_class.factory("formula-to-map")
       }.to raise_error(FormulaUnavailableError)
 
-      ENV["HOMEBREW_JSON_CORE"] = nil
+      ENV["HOMEBREW_INSTALL_FROM_API"] = nil
       expect {
         described_class.map_formula_name_to_local_bottle_path "formula-to-map", formula_path
-      }.to raise_error(UsageError, /HOMEBREW_JSON_CORE not set/)
+      }.to raise_error(UsageError, /HOMEBREW_INSTALL_FROM_API not set/)
 
-      ENV["HOMEBREW_JSON_CORE"] = "1"
+      ENV["HOMEBREW_INSTALL_FROM_API"] = "1"
       described_class.map_formula_name_to_local_bottle_path "formula-to-map", formula_path
 
       expect(described_class.factory("formula-to-map")).to be_kind_of(Formula)