diff --git a/.github/workflows/llvm.yml b/.github/workflows/llvm.yml
index dab5b9bb74cd..796b26a66c08 100644
--- a/.github/workflows/llvm.yml
+++ b/.github/workflows/llvm.yml
@@ -17,17 +17,19 @@ jobs:
       matrix:
         include:
           - llvm_version: "13.0.0"
-            llvm_ubuntu_version: "20.04"
+            llvm_filename: "clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz"
           - llvm_version: "14.0.0"
-            llvm_ubuntu_version: "18.04"
+            llvm_filename: "clang+llvm-14.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz"
           - llvm_version: "15.0.6"
-            llvm_ubuntu_version: "18.04"
+            llvm_filename: "clang+llvm-15.0.6-x86_64-linux-gnu-ubuntu-18.04.tar.xz"
           - llvm_version: "16.0.3"
-            llvm_ubuntu_version: "22.04"
+            llvm_filename: "clang+llvm-16.0.3-x86_64-linux-gnu-ubuntu-22.04.tar.xz"
           - llvm_version: "17.0.6"
-            llvm_ubuntu_version: "22.04"
+            llvm_filename: "clang+llvm-17.0.6-x86_64-linux-gnu-ubuntu-22.04.tar.xz"
           - llvm_version: "18.1.4"
-            llvm_ubuntu_version: "18.04"
+            llvm_filename: "clang+llvm-18.1.4-x86_64-linux-gnu-ubuntu-18.04.tar.xz"
+          - llvm_version: "19.1.0"
+            llvm_filename: "LLVM-19.1.0-Linux-X64.tar.xz"
     name: "LLVM ${{ matrix.llvm_version }}"
     steps:
       - name: Checkout Crystal source
@@ -44,7 +46,7 @@ jobs:
       - name: Install LLVM ${{ matrix.llvm_version }}
         run: |
           mkdir -p llvm
-          curl -L "https://github.com/llvm/llvm-project/releases/download/llvmorg-${{ matrix.llvm_version }}/clang+llvm-${{ matrix.llvm_version }}-x86_64-linux-gnu-ubuntu-${{ matrix.llvm_ubuntu_version }}.tar.xz" > llvm.tar.xz
+          curl -L "https://github.com/llvm/llvm-project/releases/download/llvmorg-${{ matrix.llvm_version }}/${{ matrix.llvm_filename }}" > llvm.tar.xz
           tar x --xz -C llvm --strip-components=1 -f llvm.tar.xz
         if: steps.cache-llvm.outputs.cache-hit != 'true'
 
diff --git a/spec/compiler/codegen/debug_spec.cr b/spec/compiler/codegen/debug_spec.cr
index 4a57056fc7a3..0032fcb64b4c 100644
--- a/spec/compiler/codegen/debug_spec.cr
+++ b/spec/compiler/codegen/debug_spec.cr
@@ -160,8 +160,6 @@ describe "Code gen: debug" do
 
   it "has debug info in closure inside if (#5593)" do
     codegen(%(
-      require "prelude"
-
       def foo
         if true && true
           yield 1
diff --git a/spec/std/kernel_spec.cr b/spec/std/kernel_spec.cr
index 149e6385ac97..f41529af901a 100644
--- a/spec/std/kernel_spec.cr
+++ b/spec/std/kernel_spec.cr
@@ -254,16 +254,12 @@ describe "hardware exception" do
     error.should_not contain("Stack overflow")
   end
 
-  {% if flag?(:musl) %}
-    # FIXME: Pending as mitigation for https://github.com/crystal-lang/crystal/issues/7482
-    pending "detects stack overflow on the main stack"
-  {% else %}
-    it "detects stack overflow on the main stack", tags: %w[slow] do
-      # This spec can take some time under FreeBSD where
-      # the default stack size is 0.5G.  Setting a
-      # smaller stack size with `ulimit -s 8192`
-      # will address this.
-      status, _, error = compile_and_run_source <<-'CRYSTAL'
+  it "detects stack overflow on the main stack", tags: %w[slow] do
+    # This spec can take some time under FreeBSD where
+    # the default stack size is 0.5G.  Setting a
+    # smaller stack size with `ulimit -s 8192`
+    # will address this.
+    status, _, error = compile_and_run_source <<-'CRYSTAL'
       def foo
         y = StaticArray(Int8, 512).new(0)
         foo
@@ -271,10 +267,9 @@ describe "hardware exception" do
       foo
     CRYSTAL
 
-      status.success?.should be_false
-      error.should contain("Stack overflow")
-    end
-  {% end %}
+    status.success?.should be_false
+    error.should contain("Stack overflow")
+  end
 
   it "detects stack overflow on a fiber stack", tags: %w[slow] do
     status, _, error = compile_and_run_source <<-'CRYSTAL'
diff --git a/spec/std/thread/condition_variable_spec.cr b/spec/std/thread/condition_variable_spec.cr
index ff9c44204bb6..1bf78f797357 100644
--- a/spec/std/thread/condition_variable_spec.cr
+++ b/spec/std/thread/condition_variable_spec.cr
@@ -1,11 +1,3 @@
-{% if flag?(:musl) %}
-  # FIXME: These thread specs occasionally fail on musl/alpine based ci, so
-  # they're disabled for now to reduce noise.
-  # See https://github.com/crystal-lang/crystal/issues/8738
-  pending Thread::ConditionVariable
-  {% skip_file %}
-{% end %}
-
 require "../spec_helper"
 
 # interpreter doesn't support threads yet (#14287)
diff --git a/spec/std/thread/mutex_spec.cr b/spec/std/thread/mutex_spec.cr
index ff298f318329..99f3c5d385c3 100644
--- a/spec/std/thread/mutex_spec.cr
+++ b/spec/std/thread/mutex_spec.cr
@@ -1,11 +1,3 @@
-{% if flag?(:musl) %}
-  # FIXME: These thread specs occasionally fail on musl/alpine based ci, so
-  # they're disabled for now to reduce noise.
-  # See https://github.com/crystal-lang/crystal/issues/8738
-  pending Thread::Mutex
-  {% skip_file %}
-{% end %}
-
 require "../spec_helper"
 
 # interpreter doesn't support threads yet (#14287)
diff --git a/spec/std/thread_spec.cr b/spec/std/thread_spec.cr
index feb55454b621..5a43c7e429d1 100644
--- a/spec/std/thread_spec.cr
+++ b/spec/std/thread_spec.cr
@@ -1,13 +1,5 @@
 require "./spec_helper"
 
-{% if flag?(:musl) %}
-  # FIXME: These thread specs occasionally fail on musl/alpine based ci, so
-  # they're disabled for now to reduce noise.
-  # See https://github.com/crystal-lang/crystal/issues/8738
-  pending Thread
-  {% skip_file %}
-{% end %}
-
 # interpreter doesn't support threads yet (#14287)
 pending_interpreted describe: Thread do
   it "allows passing an argumentless fun to execute" do
diff --git a/src/compiler/crystal/codegen/debug.cr b/src/compiler/crystal/codegen/debug.cr
index 72555d074bb0..9a03420ba203 100644
--- a/src/compiler/crystal/codegen/debug.cr
+++ b/src/compiler/crystal/codegen/debug.cr
@@ -367,6 +367,16 @@ module Crystal
       old_debug_location = @current_debug_location
       set_current_debug_location location
       if builder.current_debug_location != llvm_nil && (ptr = alloca)
+        # FIXME: When debug records are used instead of debug intrinsics, it
+        # seems inserting them into an empty BasicBlock will instead place them
+        # in a totally different (next?) function where the variable doesn't
+        # exist, leading to a "function-local metadata used in wrong function"
+        # validation error. This might happen when e.g. all variables inside a
+        # block are closured. Ideally every debug record should immediately
+        # follow the variable it declares.
+        {% unless LibLLVM::IS_LT_190 %}
+          call(do_nothing_fun) if block.instructions.empty?
+        {% end %}
         di_builder.insert_declare_at_end(ptr, var, expr, builder.current_debug_location_metadata, block)
         set_current_debug_location old_debug_location
         true
@@ -376,6 +386,12 @@ module Crystal
       end
     end
 
+    private def do_nothing_fun
+      fetch_typed_fun(@llvm_mod, "llvm.donothing") do
+        LLVM::Type.function([] of LLVM::Type, @llvm_context.void)
+      end
+    end
+
     # Emit debug info for toplevel variables. Used for the main module and all
     # required files.
     def emit_vars_debug_info(vars)
diff --git a/src/crystal/system/unix/pthread.cr b/src/crystal/system/unix/pthread.cr
index b55839ff2784..50a0fc56e818 100644
--- a/src/crystal/system/unix/pthread.cr
+++ b/src/crystal/system/unix/pthread.cr
@@ -9,20 +9,35 @@ module Crystal::System::Thread
     @system_handle
   end
 
+  protected setter system_handle
+
   private def init_handle
-    # NOTE: the thread may start before `pthread_create` returns, so
-    # `@system_handle` must be set as soon as possible; we cannot use a separate
-    # handle and assign it to `@system_handle`, which would have been too late
+    # NOTE: `@system_handle` needs to be set here too, not just in
+    # `.thread_proc`, since the current thread might progress first; the value
+    # of `LibC.pthread_self` inside the new thread must be equal to this
+    # `@system_handle` after `pthread_create` returns
     ret = GC.pthread_create(
       thread: pointerof(@system_handle),
       attr: Pointer(LibC::PthreadAttrT).null,
-      start: ->(data : Void*) { data.as(::Thread).start; Pointer(Void).null },
+      start: ->Thread.thread_proc(Void*),
       arg: self.as(Void*),
     )
 
     raise RuntimeError.from_os_error("pthread_create", Errno.new(ret)) unless ret == 0
   end
 
+  def self.thread_proc(data : Void*) : Void*
+    th = data.as(::Thread)
+
+    # `#start` calls `#stack_address`, which might read `@system_handle` before
+    # `GC.pthread_create` updates it in the original thread that spawned the
+    # current one, so we also assign to it here
+    th.system_handle = current_handle
+
+    th.start
+    Pointer(Void).null
+  end
+
   def self.current_handle : Handle
     LibC.pthread_self
   end
@@ -116,11 +131,26 @@ module Crystal::System::Thread
       ret = LibC.pthread_attr_destroy(pointerof(attr))
       raise RuntimeError.from_os_error("pthread_attr_destroy", Errno.new(ret)) unless ret == 0
     {% elsif flag?(:linux) %}
-      if LibC.pthread_getattr_np(@system_handle, out attr) == 0
-        LibC.pthread_attr_getstack(pointerof(attr), pointerof(address), out _)
-      end
+      ret = LibC.pthread_getattr_np(@system_handle, out attr)
+      raise RuntimeError.from_os_error("pthread_getattr_np", Errno.new(ret)) unless ret == 0
+
+      LibC.pthread_attr_getstack(pointerof(attr), pointerof(address), out stack_size)
+
       ret = LibC.pthread_attr_destroy(pointerof(attr))
       raise RuntimeError.from_os_error("pthread_attr_destroy", Errno.new(ret)) unless ret == 0
+
+      # with musl-libc, the main thread does not respect `rlimit -Ss` and
+      # instead returns the same default stack size as non-default threads, so
+      # we obtain the rlimit to correct the stack address manually
+      {% if flag?(:musl) %}
+        if Thread.current_is_main?
+          if LibC.getrlimit(LibC::RLIMIT_STACK, out rlim) == 0
+            address = address + stack_size - rlim.rlim_cur
+          else
+            raise RuntimeError.from_errno("getrlimit")
+          end
+        end
+      {% end %}
     {% elsif flag?(:openbsd) %}
       ret = LibC.pthread_stackseg_np(@system_handle, out stack)
       raise RuntimeError.from_os_error("pthread_stackseg_np", Errno.new(ret)) unless ret == 0
@@ -138,6 +168,14 @@ module Crystal::System::Thread
     address
   end
 
+  {% if flag?(:musl) %}
+    @@main_handle : Handle = current_handle
+
+    def self.current_is_main?
+      current_handle == @@main_handle
+    end
+  {% end %}
+
   # Warning: must be called from the current thread itself, because Darwin
   # doesn't allow to set the name of any thread but the current one!
   private def system_name=(name : String) : String
diff --git a/src/intrinsics.cr b/src/intrinsics.cr
index 7cdc462ce543..dc83ab91c884 100644
--- a/src/intrinsics.cr
+++ b/src/intrinsics.cr
@@ -163,8 +163,13 @@ lib LibIntrinsics
   {% if flag?(:interpreted) %} @[Primitive(:interpreter_intrinsics_fshr128)] {% end %}
   fun fshr128 = "llvm.fshr.i128"(a : UInt128, b : UInt128, count : UInt128) : UInt128
 
-  fun va_start = "llvm.va_start"(ap : Void*)
-  fun va_end = "llvm.va_end"(ap : Void*)
+  {% if compare_versions(Crystal::LLVM_VERSION, "19.1.0") < 0 %}
+    fun va_start = "llvm.va_start"(ap : Void*)
+    fun va_end = "llvm.va_end"(ap : Void*)
+  {% else %}
+    fun va_start = "llvm.va_start.p0"(ap : Void*)
+    fun va_end = "llvm.va_end.p0"(ap : Void*)
+  {% end %}
 
   {% if flag?(:i386) || flag?(:x86_64) %}
     {% if flag?(:interpreted) %} @[Primitive(:interpreter_intrinsics_pause)] {% end %}
diff --git a/src/lib_c/aarch64-linux-musl/c/sys/resource.cr b/src/lib_c/aarch64-linux-musl/c/sys/resource.cr
index 7f550c37a622..daa583ac5895 100644
--- a/src/lib_c/aarch64-linux-musl/c/sys/resource.cr
+++ b/src/lib_c/aarch64-linux-musl/c/sys/resource.cr
@@ -1,4 +1,15 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK = 3
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval
diff --git a/src/lib_c/i386-linux-musl/c/sys/resource.cr b/src/lib_c/i386-linux-musl/c/sys/resource.cr
index 7f550c37a622..daa583ac5895 100644
--- a/src/lib_c/i386-linux-musl/c/sys/resource.cr
+++ b/src/lib_c/i386-linux-musl/c/sys/resource.cr
@@ -1,4 +1,15 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK = 3
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval
diff --git a/src/lib_c/x86_64-linux-musl/c/sys/resource.cr b/src/lib_c/x86_64-linux-musl/c/sys/resource.cr
index 7f550c37a622..daa583ac5895 100644
--- a/src/lib_c/x86_64-linux-musl/c/sys/resource.cr
+++ b/src/lib_c/x86_64-linux-musl/c/sys/resource.cr
@@ -1,4 +1,15 @@
 lib LibC
+  alias RlimT = ULongLong
+
+  struct Rlimit
+    rlim_cur : RlimT
+    rlim_max : RlimT
+  end
+
+  fun getrlimit(Int, Rlimit*) : Int
+
+  RLIMIT_STACK = 3
+
   struct RUsage
     ru_utime : Timeval
     ru_stime : Timeval
diff --git a/src/llvm/context.cr b/src/llvm/context.cr
index 987e8f13ba6b..84c96610a96f 100644
--- a/src/llvm/context.cr
+++ b/src/llvm/context.cr
@@ -108,7 +108,11 @@ class LLVM::Context
   end
 
   def const_string(string : String) : Value
-    Value.new LibLLVM.const_string_in_context(self, string, string.bytesize, 0)
+    {% if LibLLVM::IS_LT_190 %}
+      Value.new LibLLVM.const_string_in_context(self, string, string.bytesize, 0)
+    {% else %}
+      Value.new LibLLVM.const_string_in_context2(self, string, string.bytesize, 0)
+    {% end %}
   end
 
   def const_struct(values : Array(LLVM::Value), packed = false) : Value
diff --git a/src/llvm/di_builder.cr b/src/llvm/di_builder.cr
index 37be65ef8cf8..7a06a7041349 100644
--- a/src/llvm/di_builder.cr
+++ b/src/llvm/di_builder.cr
@@ -96,7 +96,11 @@ struct LLVM::DIBuilder
   end
 
   def insert_declare_at_end(storage, var_info, expr, dl : LibLLVM::MetadataRef, block)
-    LibLLVM.di_builder_insert_declare_at_end(self, storage, var_info, expr, dl, block)
+    {% if LibLLVM::IS_LT_190 %}
+      LibLLVM.di_builder_insert_declare_at_end(self, storage, var_info, expr, dl, block)
+    {% else %}
+      LibLLVM.di_builder_insert_declare_record_at_end(self, storage, var_info, expr, dl, block)
+    {% end %}
   end
 
   def get_or_create_array(elements : Array(LibLLVM::MetadataRef))
diff --git a/src/llvm/ext/llvm-versions.txt b/src/llvm/ext/llvm-versions.txt
index 92ae5ecbaa5a..6f4d3d4816d0 100644
--- a/src/llvm/ext/llvm-versions.txt
+++ b/src/llvm/ext/llvm-versions.txt
@@ -1 +1 @@
-18.1 17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0
+19.1 18.1 17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0
diff --git a/src/llvm/lib_llvm.cr b/src/llvm/lib_llvm.cr
index 976cedc90df5..4c7ed49e7900 100644
--- a/src/llvm/lib_llvm.cr
+++ b/src/llvm/lib_llvm.cr
@@ -65,6 +65,7 @@
     IS_LT_160 = {{compare_versions(LibLLVM::VERSION, "16.0.0") < 0}}
     IS_LT_170 = {{compare_versions(LibLLVM::VERSION, "17.0.0") < 0}}
     IS_LT_180 = {{compare_versions(LibLLVM::VERSION, "18.0.0") < 0}}
+    IS_LT_190 = {{compare_versions(LibLLVM::VERSION, "19.0.0") < 0}}
   end
 {% end %}
 
diff --git a/src/llvm/lib_llvm/core.cr b/src/llvm/lib_llvm/core.cr
index ff3327a3f78d..1796bd00a0ee 100644
--- a/src/llvm/lib_llvm/core.cr
+++ b/src/llvm/lib_llvm/core.cr
@@ -116,7 +116,11 @@ lib LibLLVM
   fun const_int_get_zext_value = LLVMConstIntGetZExtValue(constant_val : ValueRef) : ULongLong
   fun const_int_get_sext_value = LLVMConstIntGetSExtValue(constant_val : ValueRef) : LongLong
 
-  fun const_string_in_context = LLVMConstStringInContext(c : ContextRef, str : Char*, length : UInt, dont_null_terminate : Bool) : ValueRef
+  {% if LibLLVM::IS_LT_190 %}
+    fun const_string_in_context = LLVMConstStringInContext(c : ContextRef, str : Char*, length : UInt, dont_null_terminate : Bool) : ValueRef
+  {% else %}
+    fun const_string_in_context2 = LLVMConstStringInContext2(c : ContextRef, str : Char*, length : SizeT, dont_null_terminate : Bool) : ValueRef
+  {% end %}
   fun const_struct_in_context = LLVMConstStructInContext(c : ContextRef, constant_vals : ValueRef*, count : UInt, packed : Bool) : ValueRef
   fun const_array = LLVMConstArray(element_ty : TypeRef, constant_vals : ValueRef*, length : UInt) : ValueRef
 
diff --git a/src/llvm/lib_llvm/debug_info.cr b/src/llvm/lib_llvm/debug_info.cr
index 6df8ba16e760..15d2eca3ebd6 100644
--- a/src/llvm/lib_llvm/debug_info.cr
+++ b/src/llvm/lib_llvm/debug_info.cr
@@ -111,10 +111,17 @@ lib LibLLVM
 
   fun metadata_replace_all_uses_with = LLVMMetadataReplaceAllUsesWith(target_metadata : MetadataRef, replacement : MetadataRef)
 
-  fun di_builder_insert_declare_at_end = LLVMDIBuilderInsertDeclareAtEnd(
-    builder : DIBuilderRef, storage : ValueRef, var_info : MetadataRef,
-    expr : MetadataRef, debug_loc : MetadataRef, block : BasicBlockRef,
-  ) : ValueRef
+  {% if LibLLVM::IS_LT_190 %}
+    fun di_builder_insert_declare_at_end = LLVMDIBuilderInsertDeclareAtEnd(
+      builder : DIBuilderRef, storage : ValueRef, var_info : MetadataRef,
+      expr : MetadataRef, debug_loc : MetadataRef, block : BasicBlockRef,
+    ) : ValueRef
+  {% else %}
+    fun di_builder_insert_declare_record_at_end = LLVMDIBuilderInsertDeclareRecordAtEnd(
+      builder : DIBuilderRef, storage : ValueRef, var_info : MetadataRef,
+      expr : MetadataRef, debug_loc : MetadataRef, block : BasicBlockRef,
+    ) : DbgRecordRef
+  {% end %}
 
   fun di_builder_create_auto_variable = LLVMDIBuilderCreateAutoVariable(
     builder : DIBuilderRef, scope : MetadataRef, name : Char*, name_len : SizeT, file : MetadataRef,
diff --git a/src/llvm/lib_llvm/types.cr b/src/llvm/lib_llvm/types.cr
index a1b374f30219..532078394794 100644
--- a/src/llvm/lib_llvm/types.cr
+++ b/src/llvm/lib_llvm/types.cr
@@ -17,4 +17,5 @@ lib LibLLVM
   {% end %}
   type OperandBundleRef = Void*
   type AttributeRef = Void*
+  type DbgRecordRef = Void*
 end