diff --git a/test/loading.jl b/test/loading.jl
index 664bd778ca926..8f0c4897e24eb 100644
--- a/test/loading.jl
+++ b/test/loading.jl
@@ -1158,6 +1158,74 @@ end
         cmd = addenv(cmd, "JULIA_LOAD_PATH" => proj)
         @test occursin("Hello Cycles!", String(read(cmd)))
 
+        # Extension-to-extension dependencies
+
+        mktempdir() do depot # Parallel pre-compilation
+            code = """
+            Base.disable_parallel_precompile = false
+            using ExtToExtDependency
+            Base.get_extension(ExtToExtDependency, :ExtA) isa Module || error("expected extension to load")
+            Base.get_extension(ExtToExtDependency, :ExtAB) isa Module || error("expected extension to load")
+            ExtToExtDependency.greet()
+            """
+            proj = joinpath(@__DIR__, "project", "Extensions", "ExtToExtDependency")
+            cmd =  `$(Base.julia_cmd()) --startup-file=no -e $code`
+            cmd = addenv(cmd,
+                "JULIA_LOAD_PATH" => proj,
+                "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
+            )
+            @test occursin("Hello ext-to-ext!", String(read(cmd)))
+        end
+        mktempdir() do depot # Serial pre-compilation
+            code = """
+            Base.disable_parallel_precompile = true
+            using ExtToExtDependency
+            Base.get_extension(ExtToExtDependency, :ExtA) isa Module || error("expected extension to load")
+            Base.get_extension(ExtToExtDependency, :ExtAB) isa Module || error("expected extension to load")
+            ExtToExtDependency.greet()
+            """
+            proj = joinpath(@__DIR__, "project", "Extensions", "ExtToExtDependency")
+            cmd =  `$(Base.julia_cmd()) --startup-file=no -e $code`
+            cmd = addenv(cmd,
+                "JULIA_LOAD_PATH" => proj,
+                "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
+            )
+            @test occursin("Hello ext-to-ext!", String(read(cmd)))
+        end
+
+        mktempdir() do depot # Parallel pre-compilation
+            code = """
+            Base.disable_parallel_precompile = false
+            using CrossPackageExtToExtDependency
+            Base.get_extension(CrossPackageExtToExtDependency.CyclicExtensions, :ExtA) isa Module || error("expected extension to load")
+            Base.get_extension(CrossPackageExtToExtDependency, :ExtAB) isa Module || error("expected extension to load")
+            CrossPackageExtToExtDependency.greet()
+            """
+            proj = joinpath(@__DIR__, "project", "Extensions", "CrossPackageExtToExtDependency")
+            cmd =  `$(Base.julia_cmd()) --startup-file=no -e $code`
+            cmd = addenv(cmd,
+                "JULIA_LOAD_PATH" => proj,
+                "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
+            )
+            @test occursin("Hello x-package ext-to-ext!", String(read(cmd)))
+        end
+        mktempdir() do depot # Serial pre-compilation
+            code = """
+            Base.disable_parallel_precompile = true
+            using CrossPackageExtToExtDependency
+            Base.get_extension(CrossPackageExtToExtDependency.CyclicExtensions, :ExtA) isa Module || error("expected extension to load")
+            Base.get_extension(CrossPackageExtToExtDependency, :ExtAB) isa Module || error("expected extension to load")
+            CrossPackageExtToExtDependency.greet()
+            """
+            proj = joinpath(@__DIR__, "project", "Extensions", "CrossPackageExtToExtDependency")
+            cmd =  `$(Base.julia_cmd()) --startup-file=no -e $code`
+            cmd = addenv(cmd,
+                "JULIA_LOAD_PATH" => proj,
+                "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
+            )
+            @test occursin("Hello x-package ext-to-ext!", String(read(cmd)))
+        end
+
     finally
         try
             rm(depot_path, force=true, recursive=true)
diff --git a/test/project/Extensions/CrossPackageExtToExtDependency/Manifest.toml b/test/project/Extensions/CrossPackageExtToExtDependency/Manifest.toml
new file mode 100644
index 0000000000000..5497fdb7091bb
--- /dev/null
+++ b/test/project/Extensions/CrossPackageExtToExtDependency/Manifest.toml
@@ -0,0 +1,32 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.11.1"
+manifest_format = "2.0"
+project_hash = "dc35c2cf8c6b82fb5b9624c9713c2df34ca30499"
+
+[[deps.CyclicExtensions]]
+deps = ["ExtDep"]
+path = "../CyclicExtensions"
+uuid = "17d4f0df-b55c-4714-ac4b-55fa23f7355c"
+version = "0.1.0"
+weakdeps = ["SomePackage"]
+
+    [deps.CyclicExtensions.extensions]
+    ExtA = ["SomePackage"]
+    ExtB = ["SomePackage"]
+
+[[deps.ExtDep]]
+deps = ["SomeOtherPackage", "SomePackage"]
+path = "../ExtDep.jl"
+uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
+version = "0.1.0"
+
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
+[[deps.SomePackage]]
+path = "../SomePackage"
+uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+version = "0.1.0"
diff --git a/test/project/Extensions/CrossPackageExtToExtDependency/Project.toml b/test/project/Extensions/CrossPackageExtToExtDependency/Project.toml
new file mode 100644
index 0000000000000..76ffb7bd1c882
--- /dev/null
+++ b/test/project/Extensions/CrossPackageExtToExtDependency/Project.toml
@@ -0,0 +1,12 @@
+name = "CrossPackageExtToExtDependency"
+uuid = "30f07f2e-c47e-40db-93a2-cbc4d1b301cc"
+version = "0.1.0"
+
+[deps]
+CyclicExtensions = "17d4f0df-b55c-4714-ac4b-55fa23f7355c"
+
+[weakdeps]
+SomePackage = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+
+[extensions]
+ExtAB = ["CyclicExtensions", "SomePackage"]
diff --git a/test/project/Extensions/CrossPackageExtToExtDependency/ext/ExtAB.jl b/test/project/Extensions/CrossPackageExtToExtDependency/ext/ExtAB.jl
new file mode 100644
index 0000000000000..1ded9f2df5097
--- /dev/null
+++ b/test/project/Extensions/CrossPackageExtToExtDependency/ext/ExtAB.jl
@@ -0,0 +1,12 @@
+module ExtAB
+
+using CrossPackageExtToExtDependency
+using SomePackage
+using CyclicExtensions
+
+const ExtA = Base.get_extension(CyclicExtensions, :ExtA)
+if !(ExtA isa Module)
+    error("expected extension to load")
+end
+
+end
diff --git a/test/project/Extensions/CrossPackageExtToExtDependency/src/CrossPackageExtToExtDependency.jl b/test/project/Extensions/CrossPackageExtToExtDependency/src/CrossPackageExtToExtDependency.jl
new file mode 100644
index 0000000000000..28b229e2d61bf
--- /dev/null
+++ b/test/project/Extensions/CrossPackageExtToExtDependency/src/CrossPackageExtToExtDependency.jl
@@ -0,0 +1,7 @@
+module CrossPackageExtToExtDependency
+
+using CyclicExtensions
+
+greet() = print("Hello x-package ext-to-ext!")
+
+end # module CrossPackageExtToTextDependency
diff --git a/test/project/Extensions/CyclicExtensions/Manifest.toml b/test/project/Extensions/CyclicExtensions/Manifest.toml
index a506825cf7995..0f280293c07b6 100644
--- a/test/project/Extensions/CyclicExtensions/Manifest.toml
+++ b/test/project/Extensions/CyclicExtensions/Manifest.toml
@@ -5,7 +5,7 @@ manifest_format = "2.0"
 project_hash = "ec25ff8df3a5e2212a173c3de2c7d716cc47cd36"
 
 [[deps.ExtDep]]
-deps = ["SomePackage"]
+deps = ["SomePackage", "SomeOtherPackage"]
 path = "../ExtDep.jl"
 uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
 version = "0.1.0"
@@ -15,6 +15,11 @@ path = "../ExtDep2"
 uuid = "55982ee5-2ad5-4c40-8cfe-5e9e1b01500d"
 version = "0.1.0"
 
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
 [[deps.SomePackage]]
 path = "../SomePackage"
 uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
diff --git a/test/project/Extensions/EnvWithDeps/Manifest.toml b/test/project/Extensions/EnvWithDeps/Manifest.toml
index 85ff259f0a4d5..554a317b370eb 100644
--- a/test/project/Extensions/EnvWithDeps/Manifest.toml
+++ b/test/project/Extensions/EnvWithDeps/Manifest.toml
@@ -5,7 +5,7 @@ manifest_format = "2.0"
 project_hash = "ec25ff8df3a5e2212a173c3de2c7d716cc47cd36"
 
 [[deps.ExtDep]]
-deps = ["SomePackage"]
+deps = ["SomePackage", "SomeOtherPackage"]
 path = "../ExtDep.jl"
 uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
 version = "0.1.0"
@@ -15,6 +15,11 @@ path = "../ExtDep2"
 uuid = "55982ee5-2ad5-4c40-8cfe-5e9e1b01500d"
 version = "0.1.0"
 
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
 [[deps.SomePackage]]
 path = "../SomePackage"
 uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
diff --git a/test/project/Extensions/EnvWithHasExtensions/Manifest.toml b/test/project/Extensions/EnvWithHasExtensions/Manifest.toml
index 004ef7892c173..ca2be57c61596 100644
--- a/test/project/Extensions/EnvWithHasExtensions/Manifest.toml
+++ b/test/project/Extensions/EnvWithHasExtensions/Manifest.toml
@@ -5,7 +5,7 @@ manifest_format = "2.0"
 project_hash = "a4c480cfa7da9610333d5c42623bf746bd286c5f"
 
 [[deps.ExtDep]]
-deps = ["SomePackage"]
+deps = ["SomePackage", "SomeOtherPackage"]
 path = "../ExtDep.jl"
 uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
 version = "0.1.0"
@@ -25,6 +25,11 @@ version = "0.1.0"
     ExtDep2 = "55982ee5-2ad5-4c40-8cfe-5e9e1b01500d"
     LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
 [[deps.SomePackage]]
 path = "../SomePackage"
 uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
diff --git a/test/project/Extensions/EnvWithHasExtensionsv2/Manifest.toml b/test/project/Extensions/EnvWithHasExtensionsv2/Manifest.toml
index 66781a5701363..9f8c717041b6e 100644
--- a/test/project/Extensions/EnvWithHasExtensionsv2/Manifest.toml
+++ b/test/project/Extensions/EnvWithHasExtensionsv2/Manifest.toml
@@ -5,7 +5,7 @@ manifest_format = "2.0"
 project_hash = "caa716752e6dff3d77c3de929ebbb5d2024d04ef"
 
 [[deps.ExtDep]]
-deps = ["SomePackage"]
+deps = ["SomePackage", "SomeOtherPackage"]
 path = "../ExtDep.jl"
 uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
 version = "0.1.0"
@@ -19,6 +19,11 @@ weakdeps = ["ExtDep"]
     [deps.HasExtensions.extensions]
     Extension2 = "ExtDep"
 
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
 [[deps.SomePackage]]
 path = "../SomePackage"
 uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
diff --git a/test/project/Extensions/ExtDep.jl/Project.toml b/test/project/Extensions/ExtDep.jl/Project.toml
index d246934b7f958..1ece7bf11f95a 100644
--- a/test/project/Extensions/ExtDep.jl/Project.toml
+++ b/test/project/Extensions/ExtDep.jl/Project.toml
@@ -4,3 +4,4 @@ version = "0.1.0"
 
 [deps]
 SomePackage = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+SomeOtherPackage = "178f68a2-4498-45ee-a775-452b36359b63"
diff --git a/test/project/Extensions/ExtDep.jl/src/ExtDep.jl b/test/project/Extensions/ExtDep.jl/src/ExtDep.jl
index 1c0022d879f51..2d3c6b7f28827 100644
--- a/test/project/Extensions/ExtDep.jl/src/ExtDep.jl
+++ b/test/project/Extensions/ExtDep.jl/src/ExtDep.jl
@@ -2,6 +2,7 @@ module ExtDep
 
 # loading this package makes the check for loading extensions trigger
 # which tests #47921
+using SomeOtherPackage
 using SomePackage
 
 struct ExtDepStruct end
diff --git a/test/project/Extensions/ExtToExtDependency/Manifest.toml b/test/project/Extensions/ExtToExtDependency/Manifest.toml
new file mode 100644
index 0000000000000..41546213cdd41
--- /dev/null
+++ b/test/project/Extensions/ExtToExtDependency/Manifest.toml
@@ -0,0 +1,21 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.11.1"
+manifest_format = "2.0"
+project_hash = "90b427e837c654fabb1434527ea698dabad46d29"
+
+[[deps.ExtDep]]
+deps = ["SomeOtherPackage", "SomePackage"]
+path = "../ExtDep.jl"
+uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
+version = "0.1.0"
+
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
+[[deps.SomePackage]]
+path = "../SomePackage"
+uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+version = "0.1.0"
diff --git a/test/project/Extensions/ExtToExtDependency/Project.toml b/test/project/Extensions/ExtToExtDependency/Project.toml
new file mode 100644
index 0000000000000..980db74c04dc4
--- /dev/null
+++ b/test/project/Extensions/ExtToExtDependency/Project.toml
@@ -0,0 +1,14 @@
+name = "ExtToExtDependency"
+uuid = "594ddb71-72fb-4cfe-9471-775d48a5b70b"
+version = "0.1.0"
+
+[deps]
+ExtDep = "fa069be4-f60b-4d4c-8b95-f8008775090c"
+
+[weakdeps]
+SomeOtherPackage = "178f68a2-4498-45ee-a775-452b36359b63"
+SomePackage = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+
+[extensions]
+ExtA = ["SomePackage"]
+ExtAB = ["SomePackage", "SomeOtherPackage"]
diff --git a/test/project/Extensions/ExtToExtDependency/ext/ExtA.jl b/test/project/Extensions/ExtToExtDependency/ext/ExtA.jl
new file mode 100644
index 0000000000000..71ed09795157c
--- /dev/null
+++ b/test/project/Extensions/ExtToExtDependency/ext/ExtA.jl
@@ -0,0 +1,6 @@
+module ExtA
+
+using ExtToExtDependency
+using SomePackage
+
+end
diff --git a/test/project/Extensions/ExtToExtDependency/ext/ExtAB.jl b/test/project/Extensions/ExtToExtDependency/ext/ExtAB.jl
new file mode 100644
index 0000000000000..a5b2c43cafd58
--- /dev/null
+++ b/test/project/Extensions/ExtToExtDependency/ext/ExtAB.jl
@@ -0,0 +1,12 @@
+module ExtAB
+
+using ExtToExtDependency
+using SomePackage
+using SomeOtherPackage
+
+const ExtA = Base.get_extension(ExtToExtDependency, :ExtA)
+if !(ExtA isa Module)
+    error("expected extension to load")
+end
+
+end
diff --git a/test/project/Extensions/ExtToExtDependency/src/ExtToExtDependency.jl b/test/project/Extensions/ExtToExtDependency/src/ExtToExtDependency.jl
new file mode 100644
index 0000000000000..ec2bf58f18641
--- /dev/null
+++ b/test/project/Extensions/ExtToExtDependency/src/ExtToExtDependency.jl
@@ -0,0 +1,7 @@
+module ExtToExtDependency
+
+using ExtDep
+
+greet() = print("Hello ext-to-ext!")
+
+end # module ExtToExtDependency
diff --git a/test/project/Extensions/HasDepWithExtensions.jl/Manifest.toml b/test/project/Extensions/HasDepWithExtensions.jl/Manifest.toml
index 5706aba59d1e0..59bd802c9710a 100644
--- a/test/project/Extensions/HasDepWithExtensions.jl/Manifest.toml
+++ b/test/project/Extensions/HasDepWithExtensions.jl/Manifest.toml
@@ -5,7 +5,7 @@ manifest_format = "2.0"
 project_hash = "4e196b07f2ee7adc48ac9d528d42b3cf3737c7a0"
 
 [[deps.ExtDep]]
-deps = ["SomePackage"]
+deps = ["SomePackage", "SomeOtherPackage"]
 path = "../ExtDep.jl"
 uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
 version = "0.1.0"
@@ -37,6 +37,11 @@ version = "0.1.0"
     ExtDep2 = "55982ee5-2ad5-4c40-8cfe-5e9e1b01500d"
     LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
+[[deps.SomeOtherPackage]]
+path = "../SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+version = "0.1.0"
+
 [[deps.SomePackage]]
 path = "../SomePackage"
 uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
diff --git a/test/project/Extensions/SomeOtherPackage/Project.toml b/test/project/Extensions/SomeOtherPackage/Project.toml
new file mode 100644
index 0000000000000..6e7eee40c7be2
--- /dev/null
+++ b/test/project/Extensions/SomeOtherPackage/Project.toml
@@ -0,0 +1,4 @@
+name = "SomeOtherPackage"
+uuid = "178f68a2-4498-45ee-a775-452b36359b63"
+authors = ["Cody Tapscott <topolarity@tapscott.me>"]
+version = "0.1.0"
diff --git a/test/project/Extensions/SomeOtherPackage/src/SomeOtherPackage.jl b/test/project/Extensions/SomeOtherPackage/src/SomeOtherPackage.jl
new file mode 100644
index 0000000000000..ba23eb3914561
--- /dev/null
+++ b/test/project/Extensions/SomeOtherPackage/src/SomeOtherPackage.jl
@@ -0,0 +1,5 @@
+module SomeOtherPackage
+
+greet() = print("Hello World!")
+
+end # module SomeOtherPackage