diff --git a/Library/Homebrew/ast_constants.rb b/Library/Homebrew/ast_constants.rb
index 38df04869e65d..1b28d06bf9e9f 100644
--- a/Library/Homebrew/ast_constants.rb
+++ b/Library/Homebrew/ast_constants.rb
@@ -46,6 +46,7 @@
   [{ name: :needs, type: :method_call }],
   [{ name: :allow_network_access!, type: :method_call }],
   [{ name: :deny_network_access!, type: :method_call }],
+  [{ name: :allow_in_sandbox!, type: :method_call }],
   [{ name: :install, type: :method_definition }],
   [{ name: :post_install, type: :method_definition }],
   [{ name: :caveats, type: :method_definition }],
diff --git a/Library/Homebrew/dev-cmd/test.rb b/Library/Homebrew/dev-cmd/test.rb
index bcab2320235c1..2c17d2360d714 100644
--- a/Library/Homebrew/dev-cmd/test.rb
+++ b/Library/Homebrew/dev-cmd/test.rb
@@ -86,7 +86,7 @@ def run
                 sandbox = Sandbox.new
                 f.logs.mkpath
                 sandbox.record_log(f.logs/"test.sandbox.log")
-                sandbox.allow_write_temp_and_cache(f)
+                sandbox.allow_write_temp_and_cache
                 sandbox.allow_write_log(f)
                 sandbox.allow_write_xcode
                 sandbox.allow_write_path(HOMEBREW_PREFIX/"var/cache")
@@ -94,6 +94,8 @@ def run
                 sandbox.allow_write_path(HOMEBREW_PREFIX/"var/log")
                 sandbox.allow_write_path(HOMEBREW_PREFIX/"var/run")
                 sandbox.deny_all_network_except_pipe(error_pipe) unless f.class.network_access_allowed?(:test)
+                sandbox.allow_write_global_temp if f.allowed_in_sandbox?(:write_to_temp, phase: :test)
+                sandbox.deny_signal if f.allowed_in_sandbox?(:signal, phase: :test)
                 sandbox.exec(*exec_args)
               else
                 exec(*exec_args)
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 6298a2da05b3f..e9c107ec5b3a7 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1551,13 +1551,17 @@ def link_overwrite?(path)
   # @see .disable!
   delegate disable_reason: :"self.class"
 
-  # Sandbox rules that should be skipped when installing or testing this {Formula}.
-  # Returns `nil` if there are no sandbox rules to skip.
-  # @!method reduced_sandbox
-  # @return [Array<Symbol>]
-  # @see .reduce_sandbox
-  def reduced_sandbox
-    self.class.reduced_sandbox || []
+  # Whether or not the given sandbox rule should be skipped during the given phase in this {Formula}.
+  # @!method allowed_in_sandbox?
+  # @param type [Symbol] the type of sandbox rule
+  # @param phase [Symbol] the phase to check
+  # @return [Boolean]
+  # @see .allow_in_sandbox
+  def allowed_in_sandbox?(type, phase:)
+    return false unless self.class.allowed_in_sandbox
+    return false unless self.class.allowed_in_sandbox.key?(phase)
+
+    self.class.allowed_in_sandbox[phase].include?(type)
   end
 
   sig { returns(T::Boolean) }
@@ -3287,7 +3291,7 @@ def freeze
     attr_reader :keg_only_reason
 
     # The types of sandbox restrictions that should be lifted from the formula.
-    attr_reader :reduced_sandbox
+    attr_reader :allowed_in_sandbox
 
     # A one-line description of the software. Used by users to get an overview
     # of the software and Homebrew maintainers.
@@ -4309,29 +4313,59 @@ def link_overwrite(*paths)
       link_overwrite_paths.merge(paths)
     end
 
-    # Skip certain sandbox restrictions when installing this formula.
+    # Skip certain sandbox restrictions when installing and testing this formula.
     # This can be useful if the upstream build system needs to write to
-    # locations that are protected by sandbox restrictions.
+    # locations that are protected by sandbox restrictions. Passing a
+    # phase is optional, and if not provided, the rule will be applied to
+    # all phases. The possible phases are `:build`, `:postinstall`, and `:test`.
     #
     # ### Example
     #
-    # If upstream needs to write to `/private/tmp`:
+    # If the formula needs to write to `/private/tmp` in all phases:
     #
     # ```ruby
-    # reduce_sandbox :allow_write_to_temp
+    # allow_in_sandbox! :write_to_temp
     # ```
-    def reduce_sandbox!(*types)
-      invalid_types = types.select { |type| Sandbox::SANDBOX_REDUCTIONS.exclude?(type) }
+    #
+    # If the formula needs to send signals in the `:test` phase:
+    # ```ruby
+    # allow_in_sandbox! :signal, phase: :test
+    # ```
+    #
+    # If the formula needs to write to `/private/tmp` and send signals
+    # in the `:test` and `:install` phase:
+    # ```ruby
+    # allow_in_sandbox! :write_to_temp, :signal, phase: [:test, :install]
+    # ```
+    def allow_in_sandbox!(*types, phase: nil)
+      invalid_types = types.select { |type| Sandbox::SANDBOX_DSL_RULES.exclude?(type) }
       if invalid_types.any?
         noun = if invalid_types.count > 1
           "types"
         else
           "type"
         end
-        raise ArgumentError, "Unsupported sandbox reduction #{noun}: #{invalid_types.join(", ")}"
+        raise ArgumentError, "Unsupported allow in sandbox item #{noun}: #{invalid_types.join(", ")}"
+      end
+
+      phase ||= Sandbox::SANDBOX_DSL_PHASES
+      phases = Array(phase)
+      invalid_phases = phases.select { |p| Sandbox::SANDBOX_DSL_PHASES.exclude?(p) }
+      if invalid_phases.any?
+        noun = if invalid_phases.count > 1
+          "phases"
+        else
+          "phase"
+        end
+        raise ArgumentError, "Unsupported sandbox phase #{noun}: #{invalid_phases.join(", ")}"
       end
 
-      @reduced_sandbox = types
+      @allowed_in_sandbox ||= {}
+      phases.each do |p|
+        @allowed_in_sandbox[p] ||= []
+        @allowed_in_sandbox[p].concat(types)
+        @allowed_in_sandbox[p] = @allowed_in_sandbox[p].uniq
+      end
     end
   end
 end
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 29b9d4da152de..5d81cfc56e54d 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -937,14 +937,15 @@ def build
         formula.logs.mkpath
         sandbox.record_log(formula.logs/"build.sandbox.log")
         sandbox.allow_write_path(Dir.home) if interactive?
-        sandbox.allow_write_temp_and_cache(formula)
+        sandbox.allow_write_temp_and_cache
         sandbox.allow_write_log(formula)
         sandbox.allow_cvs
         sandbox.allow_fossil
         sandbox.allow_write_xcode
         sandbox.allow_write_cellar(formula)
-        sandbox.deny_signal(formula)
         sandbox.deny_all_network_except_pipe(error_pipe) unless formula.network_access_allowed?(:build)
+        sandbox.allow_write_global_temp if formula.allowed_in_sandbox?(:write_to_temp, phase: :build)
+        sandbox.deny_signal if formula.allowed_in_sandbox?(:signal, phase: :build)
         sandbox.exec(*args)
       else
         exec(*args)
@@ -1154,7 +1155,7 @@ def post_install
         sandbox = Sandbox.new
         formula.logs.mkpath
         sandbox.record_log(formula.logs/"postinstall.sandbox.log")
-        sandbox.allow_write_temp_and_cache(formula)
+        sandbox.allow_write_temp_and_cache
         sandbox.allow_write_log(formula)
         sandbox.allow_write_xcode
         sandbox.deny_write_homebrew_repository
@@ -1163,6 +1164,8 @@ def post_install
         Keg::KEG_LINK_DIRECTORIES.each do |dir|
           sandbox.allow_write_path "#{HOMEBREW_PREFIX}/#{dir}"
         end
+        sandbox.allow_write_global_temp if formula.allowed_in_sandbox?(:write_to_temp, phase: :postinstall)
+        sandbox.deny_signal if formula.allowed_in_sandbox?(:signal, phase: :postinstall)
         sandbox.exec(*args)
       else
         exec(*args)
diff --git a/Library/Homebrew/sandbox.rb b/Library/Homebrew/sandbox.rb
index ba923b9cc9a66..b65c2ebbaec27 100644
--- a/Library/Homebrew/sandbox.rb
+++ b/Library/Homebrew/sandbox.rb
@@ -11,7 +11,8 @@ class Sandbox
   SANDBOX_EXEC = "/usr/bin/sandbox-exec"
   private_constant :SANDBOX_EXEC
 
-  SANDBOX_REDUCTIONS = [:allow_write_to_temp, :allow_signal].freeze
+  SANDBOX_DSL_RULES = [:write_to_temp, :signal].freeze
+  SANDBOX_DSL_PHASES = [:build, :postinstall, :test].freeze
 
   sig { returns(T::Boolean) }
   def self.available?
@@ -57,23 +58,22 @@ def deny_write_path(path)
     deny_write path:, type: :subpath
   end
 
-  sig { params(formula: T.nilable(Formula)).void }
-  def allow_write_temp_and_cache(formula = nil)
-    if formula&.reduced_sandbox&.include?(:allow_write_to_temp)
-      allow_write_path "/private/tmp"
-      allow_write_path "/private/var/tmp"
-    end
+  sig { void }
+  def allow_write_temp_and_cache
     allow_write path: "^/private/var/folders/[^/]+/[^/]+/[C,T]/", type: :regex
     allow_write_path HOMEBREW_TEMP
     allow_write_path HOMEBREW_CACHE
   end
 
-  sig { params(formula: T.nilable(Formula)).void }
-  def deny_signal(formula = nil)
-    puts "deny_signal:  #{formula&.reduced_sandbox&.include?(:allow_signal)}"
-    unless formula&.reduced_sandbox&.include?(:allow_signal)
-      add_rule allow: false, operation: "signal", filter: "target others"
-    end
+  sig { void }
+  def allow_write_global_temp
+    allow_write_path "/private/tmp"
+    allow_write_path "/private/var/tmp"
+  end
+
+  sig { void }
+  def deny_signal
+    add_rule allow: false, operation: "signal", filter: "target others"
   end
 
   sig { void }