diff --git a/common/check_internal.cpp b/common/check_internal.cpp
index c00d9fd23265..ed08be1110a8 100644
--- a/common/check_internal.cpp
+++ b/common/check_internal.cpp
@@ -4,6 +4,8 @@
 
 #include "common/check_internal.h"
 
+#include "llvm/Support/Signals.h"
+
 namespace Carbon::Internal {
 
 // Prints the buffered message.
diff --git a/common/check_internal.h b/common/check_internal.h
index 2cad4789a307..cfaedc00e93f 100644
--- a/common/check_internal.h
+++ b/common/check_internal.h
@@ -7,8 +7,6 @@
 
 #include <cstdlib>
 
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/Signals.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace Carbon::Internal {
diff --git a/common/ostream.h b/common/ostream.h
index be1e250c3811..8033d131db60 100644
--- a/common/ostream.h
+++ b/common/ostream.h
@@ -9,7 +9,8 @@
 
 #include "common/metaprogramming.h"
 #include "llvm/Support/raw_os_ostream.h"
-#include "llvm/Support/raw_ostream.h"
+// Libraries should include this header instead of raw_ostream.
+#include "llvm/Support/raw_ostream.h"  // IWYU pragma: export
 
 namespace Carbon {
 
diff --git a/toolchain/parser/parse_tree_fuzzer.cpp b/toolchain/parser/parse_tree_fuzzer.cpp
index fd6ebdbb36d5..7dd1404a9086 100644
--- a/toolchain/parser/parse_tree_fuzzer.cpp
+++ b/toolchain/parser/parse_tree_fuzzer.cpp
@@ -6,7 +6,6 @@
 #include <cstdint>
 #include <cstring>
 
-#include "common/check.h"
 #include "llvm/ADT/StringRef.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/diagnostics/null_diagnostics.h"
diff --git a/toolchain/parser/parse_tree_test.cpp b/toolchain/parser/parse_tree_test.cpp
index 2955f9ec66ca..a9db43a5623d 100644
--- a/toolchain/parser/parse_tree_test.cpp
+++ b/toolchain/parser/parse_tree_test.cpp
@@ -9,7 +9,6 @@
 
 #include <forward_list>
 
-#include "llvm/Support/FormatVariadic.h"
 #include "toolchain/common/yaml_test_helpers.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/diagnostics/mocks.h"
diff --git a/toolchain/semantics/semantics_node_block_stack.h b/toolchain/semantics/semantics_node_block_stack.h
index 14425ee907ad..7a724b0cebf8 100644
--- a/toolchain/semantics/semantics_node_block_stack.h
+++ b/toolchain/semantics/semantics_node_block_stack.h
@@ -7,7 +7,6 @@
 
 #include <type_traits>
 
-#include "common/check.h"
 #include "llvm/ADT/SmallVector.h"
 #include "toolchain/semantics/semantics_node.h"
 
diff --git a/toolchain/semantics/semantics_parse_tree_handler.cpp b/toolchain/semantics/semantics_parse_tree_handler.cpp
index 54ae1ba114fa..6f65c2599601 100644
--- a/toolchain/semantics/semantics_parse_tree_handler.cpp
+++ b/toolchain/semantics/semantics_parse_tree_handler.cpp
@@ -13,7 +13,6 @@
 #include "toolchain/lexer/token_kind.h"
 #include "toolchain/lexer/tokenized_buffer.h"
 #include "toolchain/parser/parse_node_kind.h"
-#include "toolchain/semantics/semantics_builtin_kind.h"
 #include "toolchain/semantics/semantics_ir.h"
 #include "toolchain/semantics/semantics_node.h"
 #include "toolchain/semantics/semantics_node_block_stack.h"