@@ -23,7 +23,9 @@ use super::metadata::{
     ViewEncapsulation,
 };
 use super::namespace_registry::NamespaceRegistry;
-use crate::directive::{create_inputs_literal, create_outputs_literal};
+use crate::directive::{
+    create_host_directive_mappings_array, create_inputs_literal, create_outputs_literal,
+};
 use crate::output::ast::{
     FnParam, FunctionExpr, InstantiateExpr, InvokeFunctionExpr, LiteralArrayExpr, LiteralExpr,
     LiteralMapEntry, LiteralMapExpr, LiteralValue, OutputExpression, OutputStatement, ReadPropExpr,
@@ -1256,33 +1258,6 @@ fn create_host_directives_arg<'a>(
     }
 }
 
-/// Create a host directive mappings array.
-///
-/// Format: ['publicName', 'internalName', 'publicName2', 'internalName2']
-fn create_host_directive_mappings_array<'a>(
-    allocator: &'a Allocator,
-    mappings: &[(Atom<'a>, Atom<'a>)],
-) -> OutputExpression<'a> {
-    let mut entries: OxcVec<'a, OutputExpression<'a>> =
-        OxcVec::with_capacity_in(mappings.len() * 2, allocator);
-
-    for (public_name, internal_name) in mappings {
-        entries.push(OutputExpression::Literal(Box::new_in(
-            LiteralExpr { value: LiteralValue::String(public_name.clone()), source_span: None },
-            allocator,
-        )));
-        entries.push(OutputExpression::Literal(Box::new_in(
-            LiteralExpr { value: LiteralValue::String(internal_name.clone()), source_span: None },
-            allocator,
-        )));
-    }
-
-    OutputExpression::LiteralArray(Box::new_in(
-        LiteralArrayExpr { entries, source_span: None },
-        allocator,
-    ))
-}
-
 /// Generate `ɵɵExternalStylesFeature(['style.css', ...])` expression.
 ///
 /// See: packages/compiler/src/render3/view/compiler.ts:150-155
 
@@ -883,20 +883,20 @@ fn create_host_directives_feature_arg<'a>(
 
         // inputs (if any)
         if !hd.inputs.is_empty() {
-            let inputs_map = create_string_map(allocator, &hd.inputs);
+            let inputs_array = create_host_directive_mappings_array(allocator, &hd.inputs);
             entries.push(LiteralMapEntry {
                 key: Atom::from("inputs"),
-                value: inputs_map,
+                value: inputs_array,
                 quoted: false,
             });
         }
 
         // outputs (if any)
         if !hd.outputs.is_empty() {
-            let outputs_map = create_string_map(allocator, &hd.outputs);
+            let outputs_array = create_host_directive_mappings_array(allocator, &hd.outputs);
             entries.push(LiteralMapEntry {
                 key: Atom::from("outputs"),
-                value: outputs_map,
+                value: outputs_array,
                 quoted: false,
             });
         }
@@ -913,26 +913,31 @@ fn create_host_directives_feature_arg<'a>(
     ))
 }
 
-/// Creates a string-to-string map expression.
-fn create_string_map<'a>(
+/// Creates a host directive mappings array.
+///
+/// Format: `['publicName', 'internalName', 'publicName2', 'internalName2']`
+///
+/// Shared between directive and component compilers, mirroring Angular's
+/// `createHostDirectivesMappingArray` in `view/compiler.ts`.
+pub(crate) fn create_host_directive_mappings_array<'a>(
     allocator: &'a Allocator,
-    pairs: &[(Atom<'a>, Atom<'a>)],
+    mappings: &[(Atom<'a>, Atom<'a>)],
 ) -> OutputExpression<'a> {
-    let mut entries = Vec::new_in(allocator);
+    let mut entries = Vec::with_capacity_in(mappings.len() * 2, allocator);
 
-    for (key, value) in pairs {
-        entries.push(LiteralMapEntry {
-            key: key.clone(),
-            value: OutputExpression::Literal(Box::new_in(
-                LiteralExpr { value: LiteralValue::String(value.clone()), source_span: None },
-                allocator,
-            )),
-            quoted: false,
-        });
+    for (public_name, internal_name) in mappings {
+        entries.push(OutputExpression::Literal(Box::new_in(
+            LiteralExpr { value: LiteralValue::String(public_name.clone()), source_span: None },
+            allocator,
+        )));
+        entries.push(OutputExpression::Literal(Box::new_in(
+            LiteralExpr { value: LiteralValue::String(internal_name.clone()), source_span: None },
+            allocator,
+        )));
     }
 
-    OutputExpression::LiteralMap(Box::new_in(
-        LiteralMapExpr { entries, source_span: None },
+    OutputExpression::LiteralArray(Box::new_in(
+        LiteralArrayExpr { entries, source_span: None },
         allocator,
     ))
 }
@@ -1419,4 +1424,127 @@ mod tests {
             output
         );
     }
+
+    #[test]
+    fn test_host_directives_input_output_mappings_use_flat_array() {
+        // Issue #67: hostDirectives input/output mappings must be flat arrays
+        // ["publicName", "internalName"], NOT objects {publicName: "internalName"}
+        let allocator = Allocator::default();
+        let type_expr = OutputExpression::ReadVar(Box::new_in(
+            ReadVarExpr { name: Atom::from("TooltipTrigger"), source_span: None },
+            &allocator,
+        ));
+
+        let directive_expr = OutputExpression::ReadVar(Box::new_in(
+            ReadVarExpr { name: Atom::from("BrnTooltipTrigger"), source_span: None },
+            &allocator,
+        ));
+
+        let mut host_directive_inputs = Vec::new_in(&allocator);
+        host_directive_inputs.push((Atom::from("uTooltip"), Atom::from("brnTooltipTrigger")));
+
+        let mut host_directives = Vec::new_in(&allocator);
+        host_directives.push(R3HostDirectiveMetadata {
+            directive: directive_expr,
+            is_forward_reference: false,
+            inputs: host_directive_inputs,
+            outputs: Vec::new_in(&allocator),
+        });
+
+        let metadata = R3DirectiveMetadata {
+            name: Atom::from("TooltipTrigger"),
+            r#type: type_expr,
+            type_argument_count: 0,
+            deps: None,
+            selector: Some(Atom::from("[uTooltip]")),
+            queries: Vec::new_in(&allocator),
+            view_queries: Vec::new_in(&allocator),
+            host: R3HostMetadata::new(&allocator),
+            uses_on_changes: false,
+            inputs: Vec::new_in(&allocator),
+            outputs: Vec::new_in(&allocator),
+            uses_inheritance: false,
+            export_as: Vec::new_in(&allocator),
+            providers: None,
+            is_standalone: true,
+            is_signal: false,
+            host_directives,
+        };
+
+        let result = compile_directive(&allocator, &metadata, 0);
+        let emitter = JsEmitter::new();
+        let output = emitter.emit_expression(&result.expression);
+        let normalized = output.replace([' ', '\n', '\t'], "");
+
+        // Must contain flat array format: inputs:["uTooltip","brnTooltipTrigger"]
+        assert!(
+            normalized.contains(r#"inputs:["uTooltip","brnTooltipTrigger"]"#),
+            "Host directive inputs should be flat array [\"publicName\",\"internalName\"], not object. Got:\n{}",
+            output
+        );
+        // Must NOT contain object format: inputs:{uTooltip:"brnTooltipTrigger"}
+        assert!(
+            !normalized.contains(r#"inputs:{uTooltip:"brnTooltipTrigger"}"#),
+            "Host directive inputs should NOT be object format. Got:\n{}",
+            output
+        );
+    }
+
+    #[test]
+    fn test_host_directives_output_mappings_use_flat_array() {
+        // Issue #67: output mappings must also be flat arrays
+        let allocator = Allocator::default();
+        let type_expr = OutputExpression::ReadVar(Box::new_in(
+            ReadVarExpr { name: Atom::from("MyDirective"), source_span: None },
+            &allocator,
+        ));
+
+        let directive_expr = OutputExpression::ReadVar(Box::new_in(
+            ReadVarExpr { name: Atom::from("ClickTracker"), source_span: None },
+            &allocator,
+        ));
+
+        let mut host_directive_outputs = Vec::new_in(&allocator);
+        host_directive_outputs.push((Atom::from("clicked"), Atom::from("trackClick")));
+
+        let mut host_directives = Vec::new_in(&allocator);
+        host_directives.push(R3HostDirectiveMetadata {
+            directive: directive_expr,
+            is_forward_reference: false,
+            inputs: Vec::new_in(&allocator),
+            outputs: host_directive_outputs,
+        });
+
+        let metadata = R3DirectiveMetadata {
+            name: Atom::from("MyDirective"),
+            r#type: type_expr,
+            type_argument_count: 0,
+            deps: None,
+            selector: Some(Atom::from("[myDir]")),
+            queries: Vec::new_in(&allocator),
+            view_queries: Vec::new_in(&allocator),
+            host: R3HostMetadata::new(&allocator),
+            uses_on_changes: false,
+            inputs: Vec::new_in(&allocator),
+            outputs: Vec::new_in(&allocator),
+            uses_inheritance: false,
+            export_as: Vec::new_in(&allocator),
+            providers: None,
+            is_standalone: true,
+            is_signal: false,
+            host_directives,
+        };
+
+        let result = compile_directive(&allocator, &metadata, 0);
+        let emitter = JsEmitter::new();
+        let output = emitter.emit_expression(&result.expression);
+        let normalized = output.replace([' ', '\n', '\t'], "");
+
+        // Must contain flat array format: outputs:["clicked","trackClick"]
+        assert!(
+            normalized.contains(r#"outputs:["clicked","trackClick"]"#),
+            "Host directive outputs should be flat array. Got:\n{}",
+            output
+        );
+    }
 }
@@ -19,6 +19,7 @@ mod metadata;
 mod property_decorators;
 mod query;
 
+pub(crate) use compiler::create_host_directive_mappings_array;
 pub use compiler::{
     DirectiveCompileResult, compile_directive, compile_directive_from_metadata,
     create_inputs_literal, create_outputs_literal,
 
@@ -801,4 +801,91 @@ export class ForwardAllComponent {}
 `.trim(),
     expectedFeatures: ['ɵɵdefineComponent', 'ɵɵHostDirectivesFeature'],
   },
+
+  // ==========================================================================
+  // Host Directives on Directives (not just Components)
+  // ==========================================================================
+
+  {
+    type: 'full-transform',
+    name: 'directive-host-directive-input-mapping',
+    category: 'host-directives',
+    description: 'Directive with host directive input mappings (issue #67)',
+    className: 'UnityTooltipTrigger',
+    sourceCode: `
+import { Directive, Input } from '@angular/core';
+
+@Directive({ selector: '[brnTooltipTrigger]', standalone: true })
+export class BrnTooltipTrigger {
+  @Input() brnTooltipTrigger: string = '';
+}
+
+@Directive({
+  selector: '[uTooltip]',
+  standalone: true,
+  hostDirectives: [{
+    directive: BrnTooltipTrigger,
+    inputs: ['brnTooltipTrigger: uTooltip']
+  }]
+})
+export class UnityTooltipTrigger {}
+`.trim(),
+    expectedFeatures: ['ɵɵdefineDirective', 'ɵɵHostDirectivesFeature'],
+  },
+
+  {
+    type: 'full-transform',
+    name: 'directive-host-directive-output-mapping',
+    category: 'host-directives',
+    description: 'Directive with host directive output mappings',
+    className: 'MyWrapperDirective',
+    sourceCode: `
+import { Directive, Output, EventEmitter } from '@angular/core';
+
+@Directive({ selector: '[trackable]', standalone: true })
+export class TrackableDirective {
+  @Output() trackClick = new EventEmitter<void>();
+}
+
+@Directive({
+  selector: '[myWrapper]',
+  standalone: true,
+  hostDirectives: [{
+    directive: TrackableDirective,
+    outputs: ['trackClick: clicked']
+  }]
+})
+export class MyWrapperDirective {}
+`.trim(),
+    expectedFeatures: ['ɵɵdefineDirective', 'ɵɵHostDirectivesFeature'],
+  },
+
+  {
+    type: 'full-transform',
+    name: 'directive-host-directive-input-output-mapping',
+    category: 'host-directives',
+    description: 'Directive with both input and output host directive mappings',
+    className: 'EnhancedDirective',
+    sourceCode: `
+import { Directive, Input, Output, EventEmitter } from '@angular/core';
+
+@Directive({ selector: '[base]', standalone: true })
+export class BaseDirective {
+  @Input() baseValue: string = '';
+  @Output() baseChange = new EventEmitter<string>();
+}
+
+@Directive({
+  selector: '[enhanced]',
+  standalone: true,
+  hostDirectives: [{
+    directive: BaseDirective,
+    inputs: ['baseValue: value'],
+    outputs: ['baseChange: valueChange']
+  }]
+})
+export class EnhancedDirective {}
+`.trim(),
+    expectedFeatures: ['ɵɵdefineDirective', 'ɵɵHostDirectivesFeature'],
+  },
 ]