diff --git a/front/hir/tests/asm_result_types.rs b/front/hir/tests/asm_result_types.rs
new file mode 100644
index 00000000..0868345f
--- /dev/null
+++ b/front/hir/tests/asm_result_types.rs
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: MPL-2.0
+//! Expression-form assembly produces typed HIR facts at its scalar boundaries.
+use hir::conversions::{ConversionKind, ConversionMode};
+use hir::{HirExpressionType, TypedProgram};
+use lexer::Lexer;
+use parser::ast::{ASTNode, Expression, StatementNode, WaveType};
+use parser::parse_syntax_with_spans;
+
+fn lower(source: &str) -> Result<TypedProgram, hir::HirLoweringError> {
+    let tokens = Lexer::new_with_file(source, "asm-results.wave").tokenize().unwrap();
+    TypedProgram::lower(parse_syntax_with_spans(&tokens).unwrap())
+}
+
+fn initializer(program: &TypedProgram, index: usize) -> &Expression {
+    let ASTNode::Function(function) = &program.syntax()[0] else { panic!("function") };
+    let ASTNode::Variable(variable) = &function.body[index] else { panic!("variable") };
+    variable.initial_value.as_ref().unwrap()
+}
+
+#[test]
+fn typed_asm_result_retains_signed_extension_and_float_conversion() {
+    let program = lower(
+        r#"
+fun main() {
+    var small: i32 = 0;
+    var extended: i64 = asm { "mov eax, 7" out("eax") small clobber("nostack") };
+    var wide: i64 = 0;
+    var floating: f64 = asm { "mov rax, 7" out("rax") wide clobber("nostack") };
+}
+"#,
+    )
+    .unwrap();
+    program.verify_conversions().unwrap();
+
+    let extended = initializer(&program, 1);
+    assert_eq!(
+        program.type_of(extended),
+        Some(&HirExpressionType::Resolved(WaveType::Int(32)))
+    );
+    let fact = program.numeric_expression_of(extended).unwrap();
+    assert_eq!(fact.evaluation_type, WaveType::Int(32));
+    assert_eq!(fact.result_type, WaveType::Int(64));
+    assert_eq!(fact.conversions.len(), 1);
+    assert_eq!(fact.conversions[0].kind, ConversionKind::SignExtend);
+    assert_eq!(fact.conversions[0].mode, ConversionMode::Implicit);
+    assert_eq!(fact.conversions[0].span.file, "asm-results.wave");
+
+    let floating = initializer(&program, 3);
+    assert_eq!(
+        program.type_of(floating),
+        Some(&HirExpressionType::Resolved(WaveType::Int(64)))
+    );
+    let fact = program.numeric_expression_of(floating).unwrap();
+    assert_eq!(fact.evaluation_type, WaveType::Int(64));
+    assert_eq!(fact.result_type, WaveType::Float(64));
+    assert_eq!(fact.conversions.len(), 1);
+    assert_eq!(fact.conversions[0].kind, ConversionKind::SignedToFloat);
+    assert_eq!(fact.conversions[0].mode, ConversionMode::Implicit);
+}
+
+#[test]
+fn asm_results_participate_in_explicit_casts_arithmetic_and_returns() {
+    let source = r#"
+fun compute() -> i64 {
+    var sink: i32 = 0;
+    var flag: bool = (asm { "mov eax, 7" out("eax") sink }) as bool;
+    var sum: i32 = asm { "mov eax, 7" out("eax") sink } + 2;
+    return asm { "mov eax, 7" out("eax") sink };
+}
+"#;
+    let program = lower(source).unwrap();
+    program.verify_conversions().unwrap();
+    let flag = initializer(&program, 1);
+    let cast = program.numeric_expression_of(flag).unwrap();
+    assert_eq!(cast.conversions[0].kind, ConversionKind::IntegerToBool);
+    assert_eq!(cast.conversions[0].mode, ConversionMode::Explicit);
+
+    let sum = initializer(&program, 2);
+    let fact = program.numeric_expression_of(sum).unwrap();
+    assert_eq!(fact.computation_type, Some(WaveType::Int(32)));
+    let Expression::BinaryExpression { left, .. } = sum else { panic!("arithmetic") };
+    assert_eq!(
+        program.type_of(left),
+        Some(&HirExpressionType::Resolved(WaveType::Int(32)))
+    );
+
+    let ASTNode::Function(function) = &program.syntax()[0] else { panic!("function") };
+    let ASTNode::Statement(StatementNode::Return(Some(value))) = &function.body[3] else {
+        panic!("return");
+    };
+    let fact = program.numeric_expression_of(value).unwrap();
+    assert_eq!(fact.evaluation_type, WaveType::Int(32));
+    assert_eq!(fact.result_type, WaveType::Int(64));
+    assert_eq!(fact.conversions[0].kind, ConversionKind::SignExtend);
+}
+
+#[test]
+fn invalid_asm_value_contexts_fail_during_semantic_analysis() {
+    let cases = [
+        (
+            r#"fun main() { var sink: i64 = 0; var bad: bool = asm { "mov rax, 7" out("rax") sink }; }"#,
+            "type mismatch",
+        ),
+        (
+            r#"fun main() { var bad: i64 = asm { "nop" }; }"#,
+            "without an output cannot supply a value",
+        ),
+        (
+            r#"fun main() { var a: i64 = 0; var b: i64 = 0; var bad: i64 = asm { "nop" out("rax") a out("rdx") b }; }"#,
+            "exactly one output",
+        ),
+        (
+            r#"fun main() { var a: array<i64, 1> = [0]; var bad: i64 = asm { "nop" out("rax") a }; }"#,
+            "output must be scalar",
+        ),
+    ];
+    for (source, expected) in cases {
+        let failure = lower(source).unwrap_err();
+        assert!(
+            failure.to_string().contains(expected),
+            "expected {expected:?}, got {failure} for {source}"
+        );
+    }
+}
diff --git a/front/parser/src/verification/expression.rs b/front/parser/src/verification/expression.rs
index ba3bbe9b..3d1a6eae 100644
--- a/front/parser/src/verification/expression.rs
+++ b/front/parser/src/verification/expression.rs
@@ -602,15 +602,47 @@ impl Validator<'_> {
     fn validate_expr_asm_block(
         &mut self,
         expression: &Expression,
-        _expected: Option<&WaveType>,
+        expected: Option<&WaveType>,
     ) -> Result<ExpressionType, String> {
         let Expression::AsmBlock { inputs, outputs, .. } = expression else {
             unreachable!("expression dispatch")
         };
 
-        for (_, expression) in inputs.iter().chain(outputs.iter()) {
-            self.validate_expr(expression)?;
+        for (_, input) in inputs {
+            self.validate_expr(input)?;
+        }
+        match outputs.as_slice() {
+            [] if expected.is_none() => Ok(ExpressionType::Unknown),
+            [] => Err("asm expression without an output cannot supply a value".into()),
+            [(_, output)] => {
+                let actual = self.validate_expr(output)?;
+                let ExpressionType::Known(ty) = actual else {
+                    return Err("asm expression output must have a concrete scalar type".into());
+                };
+                let ty = self.program.canonical_type(&ty);
+                if !matches!(
+                    ty,
+                    WaveType::Int(_)
+                        | WaveType::Uint(_)
+                        | WaveType::Float(_)
+                        | WaveType::Bool
+                        | WaveType::Byte
+                        | WaveType::Char
+                        | WaveType::Isz
+                        | WaveType::Usz
+                        | WaveType::Pointer(_)
+                        | WaveType::String
+                ) {
+                    return Err(format!(
+                        "asm expression output must be scalar, found `{}`",
+                        display_wave_type(&ty)
+                    ));
+                }
+                // Record the actual result type, not the caller's expected
+                // type: HIR must plan implicit conversions in source order.
+                Ok(ExpressionType::Known(ty))
+            },
+            _ => Err("asm expression requires exactly one output".into()),
         }
-        Ok(ExpressionType::Unknown)
     }
 }
diff --git a/tests/codegen/asm_results.rs b/tests/codegen/asm_results.rs
new file mode 100644
index 00000000..0a7905d3
--- /dev/null
+++ b/tests/codegen/asm_results.rs
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: MPL-2.0
+//! Expression asm must preserve HIR conversions in both IR and native execution.
+#![cfg(any(feature = "llvm-target-x86", feature = "llvm-target-all"))]
+use super::*;
+
+#[test]
+#[cfg(any(feature = "llvm-target-x86", feature = "llvm-target-all"))]
+fn typed_expression_asm_conversions_emit_ir_and_objects() {
+    let dir = temp_case_dir("typed-asm-result");
+    let source = write_wave(
+        &dir,
+        "asm-results.wave",
+        r#"
+fun main() -> i32 {
+    var narrow: i32 = 0;
+    var wide: i64 = asm { "mov eax, 7" out("eax") narrow clobber("nostack") };
+    var sink: i64 = 0;
+    var floating: f64 = asm { "mov rax, 7" out("rax") sink clobber("nostack") };
+    var flag: bool = (asm { "mov rax, 7" out("rax") sink clobber("nostack") }) as bool;
+    var sum: i64 = asm { "mov rax, 7" out("rax") sink clobber("nostack") } + 5;
+    if (wide != 7 || floating != 7.0 || !flag || sum != 12) { return 1; }
+    return 0;
+}
+"#,
+    );
+    for opt in ["-O0", "-O2"] {
+        run_wavec([
+            OsStr::new("check"),
+            source.as_os_str(),
+            OsStr::new("--target=x86_64-unknown-linux-gnu"),
+        ]);
+        let out = dir.join(opt);
+        run_wavec([
+            OsStr::new("build"),
+            source.as_os_str(),
+            OsStr::new("--target=x86_64-unknown-linux-gnu"),
+            OsStr::new("--emit=ir,obj"),
+            OsStr::new(opt),
+            OsStr::new("--out-dir"),
+            out.as_os_str(),
+        ]);
+        let ir = fs::read_to_string(out.join("asm-results.ll")).unwrap();
+        if opt == "-O0" {
+            assert!(ir.contains("sext i32") && ir.contains("sitofp i64"), "{opt}: {ir}");
+        }
+        assert!(ir.contains("asm sideeffect"), "{opt}: {ir}");
+        assert!(out.join("asm-results.o").is_file());
+    }
+}
+
+#[test]
+#[cfg(all(
+    target_arch = "x86_64",
+    target_os = "linux",
+    any(feature = "llvm-target-x86", feature = "llvm-target-all")
+))]
+fn typed_expression_asm_conversions_execute_at_o0_and_o2() {
+    let dir = temp_case_dir("typed-asm-run");
+    let source = write_wave(
+        &dir,
+        "main.wave",
+        r#"
+fun main() -> i32 {
+    var narrow: i32 = 0;
+    var wide: i64 = asm { "mov eax, 7" out("eax") narrow clobber("nostack") };
+    var sink: i64 = 0;
+    var floating: f64 = asm { "mov rax, 7" out("rax") sink clobber("nostack") };
+    var flag: bool = (asm { "mov rax, 7" out("rax") sink clobber("nostack") }) as bool;
+    var sum: i64 = asm { "mov rax, 7" out("rax") sink clobber("nostack") } + 5;
+    if (wide != 7 || floating != 7.0 || !flag || sum != 12) { return 1; }
+    return 0;
+}
+"#,
+    );
+    for opt in ["-O0", "-O2"] {
+        let output = wavec_command()
+            .arg("build")
+            .arg(&source)
+            .arg(opt)
+            .arg("--run")
+            .arg("--out-dir")
+            .arg(dir.join(opt))
+            .output()
+            .unwrap();
+        assert!(
+            output.status.success(),
+            "{opt}: {}",
+            String::from_utf8_lossy(&output.stderr)
+        );
+    }
+}
+
+#[test]
+#[cfg(any(feature = "llvm-target-x86", feature = "llvm-target-all"))]
+fn invalid_expression_asm_initializer_is_a_source_diagnostic() {
+    let dir = temp_case_dir("typed-asm-errors");
+    let source = write_wave(
+        &dir,
+        "wrong.wave",
+        "fun main() { var sink: i64 = 0; var invalid: bool = asm { \"mov rax, 7\" out(\"rax\") sink }; }\n",
+    );
+    for emit in ["--emit=check", "--emit=ir"] {
+        let output = run_wavec_raw([
+            OsStr::new("build"),
+            source.as_os_str(),
+            OsStr::new("--target=x86_64-unknown-linux-gnu"),
+            OsStr::new("--error-format=json"),
+            OsStr::new(emit),
+        ]);
+        assert!(!output.status.success());
+        let diagnostic = String::from_utf8_lossy(&output.stderr);
+        assert!(diagnostic.contains("type mismatch"), "{diagnostic}");
+        assert!(!diagnostic.contains("E9001"), "{diagnostic}");
+    }
+}
diff --git a/tests/codegen_regressions.rs b/tests/codegen_regressions.rs
index 13b03953..3239e3e4 100644
--- a/tests/codegen_regressions.rs
+++ b/tests/codegen_regressions.rs
@@ -5,6 +5,8 @@ include!("codegen/support.rs");
 
 #[path = "codegen/abi.rs"]
 mod abi;
+#[path = "codegen/asm_results.rs"]
+mod asm_results;
 #[path = "codegen/diagnostics.rs"]
 mod diagnostics;
 #[path = "codegen/language.rs"]