diff --git a/examples/minimal-react/CHANGELOG.md b/examples/minimal-react/CHANGELOG.md
index 643236b5..22149ff5 100644
--- a/examples/minimal-react/CHANGELOG.md
+++ b/examples/minimal-react/CHANGELOG.md
@@ -1,5 +1,15 @@
 # @examples/minimal-react
 
+## 10.38.5
+
+### Patch Changes
+
+- Updated dependencies
+  - @beff/client@0.0.8
+  - @beff/hono@0.0.8
+  - @beff/cli@0.0.8
+  - @beff/react@0.0.8
+
 ## 10.38.4
 
 ### Patch Changes
diff --git a/examples/minimal-react/package.json b/examples/minimal-react/package.json
index 688b06d8..28f0d0fd 100644
--- a/examples/minimal-react/package.json
+++ b/examples/minimal-react/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@examples/minimal-react",
   "private": true,
-  "version": "10.38.4",
+  "version": "10.38.5",
   "workspaces": [
     "client",
     "server"
@@ -26,10 +26,10 @@
     "wait-port": "^1.0.1"
   },
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7",
-    "@beff/client": "workspace:^0.0.7",
-    "@beff/hono": "workspace:^0.0.7",
-    "@beff/react": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
+    "@beff/client": "workspace:^0.0.8",
+    "@beff/hono": "workspace:^0.0.8",
+    "@beff/react": "workspace:^0.0.8",
     "@hono/node-server": "^1.1.1",
     "@tanstack/react-query": "^4.33.0",
     "@types/node": "^20.5.7",
diff --git a/examples/node-server/CHANGELOG.md b/examples/node-server/CHANGELOG.md
index d98ad376..015be89f 100644
--- a/examples/node-server/CHANGELOG.md
+++ b/examples/node-server/CHANGELOG.md
@@ -1,5 +1,13 @@
 # node-server
 
+## 1.0.4
+
+### Patch Changes
+
+- Updated dependencies
+  - @beff/hono@0.0.8
+  - @beff/cli@0.0.8
+
 ## 1.0.3
 
 ### Patch Changes
diff --git a/examples/node-server/package.json b/examples/node-server/package.json
index a89d75f8..b6435009 100644
--- a/examples/node-server/package.json
+++ b/examples/node-server/package.json
@@ -1,6 +1,6 @@
 {
   "name": "node-server",
-  "version": "1.0.3",
+  "version": "1.0.4",
   "description": "",
   "main": "index.js",
   "scripts": {
@@ -12,8 +12,8 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7",
-    "@beff/hono": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
+    "@beff/hono": "workspace:^0.0.8",
     "@hono/node-server": "^1.1.1",
     "esbuild": "^0.19.2",
     "vitest": "^0.34.3"
diff --git a/examples/standalone-parser/CHANGELOG.md b/examples/standalone-parser/CHANGELOG.md
index 9d89d213..41c7d883 100644
--- a/examples/standalone-parser/CHANGELOG.md
+++ b/examples/standalone-parser/CHANGELOG.md
@@ -1,5 +1,12 @@
 # node-server
 
+## 1.0.5
+
+### Patch Changes
+
+- Updated dependencies
+  - @beff/cli@0.0.8
+
 ## 1.0.4
 
 ### Patch Changes
diff --git a/examples/standalone-parser/package.json b/examples/standalone-parser/package.json
index 93ed679a..45170037 100644
--- a/examples/standalone-parser/package.json
+++ b/examples/standalone-parser/package.json
@@ -1,6 +1,6 @@
 {
   "name": "standalone-parser",
-  "version": "1.0.4",
+  "version": "1.0.5",
   "description": "",
   "main": "index.js",
   "scripts": {
@@ -11,7 +11,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
     "vitest": "^0.34.3"
   }
 }
\ No newline at end of file
diff --git a/packages/beff-cli/CHANGELOG.md b/packages/beff-cli/CHANGELOG.md
index 0bfe22ce..ab6f2566 100644
--- a/packages/beff-cli/CHANGELOG.md
+++ b/packages/beff-cli/CHANGELOG.md
@@ -1,5 +1,11 @@
 # @beff/cli
 
+## 0.0.8
+
+### Patch Changes
+
+- Support for optional parameters
+
 ## 0.0.7
 
 ### Patch Changes
diff --git a/packages/beff-cli/package.json b/packages/beff-cli/package.json
index 0a3d5e95..70076df6 100644
--- a/packages/beff-cli/package.json
+++ b/packages/beff-cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@beff/cli",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "",
   "bin": {
     "beff": "./bin/index.js"
diff --git a/packages/beff-client/CHANGELOG.md b/packages/beff-client/CHANGELOG.md
index e4b62943..7522264c 100644
--- a/packages/beff-client/CHANGELOG.md
+++ b/packages/beff-client/CHANGELOG.md
@@ -1,5 +1,13 @@
 # @beff/client
 
+## 0.0.8
+
+### Patch Changes
+
+- Support for optional parameters
+- Updated dependencies
+  - @beff/cli@0.0.8
+
 ## 0.0.7
 
 ### Patch Changes
diff --git a/packages/beff-client/package.json b/packages/beff-client/package.json
index 63063b9f..cf2a2ce9 100644
--- a/packages/beff-client/package.json
+++ b/packages/beff-client/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@beff/client",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "",
   "main": "dist/cjs/index.js",
   "scripts": {
@@ -18,7 +18,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7"
+    "@beff/cli": "workspace:^0.0.8"
   },
   "devDependencies": {
     "typescript": "^5.2.2"
diff --git a/packages/beff-client/src/index.ts b/packages/beff-client/src/index.ts
index 5b51ea02..f99eb739 100644
--- a/packages/beff-client/src/index.ts
+++ b/packages/beff-client/src/index.ts
@@ -72,17 +72,25 @@ export class BffRequest {
           break;
         }
         case "query": {
-          if (!hasAddedQueryParams) {
-            path += "?";
-            hasAddedQueryParams = true;
-            path += `${metadata.name}=${param}`;
+          if (!metadata.required && param == null) {
+            // skip optional query params
           } else {
-            path += `&${metadata.name}=${param}`;
+            if (!hasAddedQueryParams) {
+              path += "?";
+              hasAddedQueryParams = true;
+              path += `${metadata.name}=${param}`;
+            } else {
+              path += `&${metadata.name}=${param}`;
+            }
           }
           break;
         }
         case "header": {
-          init.headers[metadata.name] = String(param);
+          if (!metadata.required && param == null) {
+            // skip optional headers
+          } else {
+            init.headers[metadata.name] = String(param);
+          }
           break;
         }
         case "body": {
diff --git a/packages/beff-core/src/api_extractor.rs b/packages/beff-core/src/api_extractor.rs
index c63e658b..fc350d6f 100644
--- a/packages/beff-core/src/api_extractor.rs
+++ b/packages/beff-core/src/api_extractor.rs
@@ -61,6 +61,36 @@ pub enum HandlerParameter {
     Context(Span),
 }
 
+impl HandlerParameter {
+    pub fn make_optional(self: HandlerParameter) -> HandlerParameter {
+        match self {
+            HandlerParameter::PathOrQueryOrBody {
+                schema,
+                description,
+                span,
+                ..
+            } => HandlerParameter::PathOrQueryOrBody {
+                schema,
+                required: false,
+                description,
+                span,
+            },
+            HandlerParameter::Header {
+                span,
+                schema,
+                description,
+                ..
+            } => HandlerParameter::Header {
+                span,
+                schema,
+                required: false,
+                description,
+            },
+            HandlerParameter::Context(_) => self,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum MethodKind {
     Get(Span),
@@ -477,7 +507,7 @@ impl<'a, R: FileManager> ExtractExportDefaultVisitor<'a, R> {
         &mut self,
         param: &Pat,
         parent_span: &Span,
-    ) -> Result<Vec<(String, HandlerParameter)>> {
+    ) -> Result<(String, HandlerParameter)> {
         match param {
             Pat::Ident(BindingIdent { id, type_ann }) => {
                 if type_ann.is_none() {
@@ -492,12 +522,15 @@ impl<'a, R: FileManager> ExtractExportDefaultVisitor<'a, R> {
                     comments.and_then(|it| self.parse_description_comment(it, &id.span));
                 let ty = self.assert_and_extract_type_from_ann(type_ann, &id.span);
                 let param = self.parse_parameter_type(&ty, !id.optional, description, &id.span)?;
-                Ok(vec![(id.sym.to_string(), param)])
+                Ok((id.sym.to_string(), param))
+            }
+            Pat::Assign(AssignPat { span, left, .. }) => {
+                let (name, ty) = self.parse_arrow_parameter(left, span)?;
+                Ok((name, ty.make_optional()))
             }
             Pat::Rest(RestPat { span, .. })
             | Pat::Array(ArrayPat { span, .. })
             | Pat::Object(ObjectPat { span, .. })
-            | Pat::Assign(AssignPat { span, .. })
             | Pat::Invalid(Invalid { span, .. }) => {
                 self.error(span, DiagnosticInfoMessage::ParameterPatternNotSupported)
             }
@@ -557,7 +590,6 @@ impl<'a, R: FileManager> ExtractExportDefaultVisitor<'a, R> {
             .iter()
             .map(|it| self.parse_arrow_parameter(&it.pat, parent_span))
             .collect::<Result<Vec<_>>>()?;
-        let parameters = parameters.into_iter().flatten().collect();
         let e = FnHandler {
             method_kind: self.parse_method_kind(key)?,
             parameters,
@@ -625,7 +657,6 @@ impl<'a, R: FileManager> ExtractExportDefaultVisitor<'a, R> {
                 .map(|it| self.parse_arrow_parameter(it, parent_span))
                 .collect::<Result<Vec<_>>>()?
                 .into_iter()
-                .flatten()
                 .collect(),
             summary: endpoint_comments.summary,
             description: endpoint_comments.description,
diff --git a/packages/beff-core/src/print/coercer.rs b/packages/beff-core/src/print/coercer.rs
index 74ce3470..4ee68c7e 100644
--- a/packages/beff-core/src/print/coercer.rs
+++ b/packages/beff-core/src/print/coercer.rs
@@ -1,4 +1,4 @@
-use crate::{swc_builder::SwcBuilder, ast::json_schema::JsonSchema};
+use crate::{ast::json_schema::JsonSchema, swc_builder::SwcBuilder};
 use swc_common::DUMMY_SP;
 use swc_ecma_ast::{
     BindingIdent, BlockStmt, CallExpr, Callee, Expr, ExprOrSpread, FnExpr, Function, Ident, Param,
@@ -25,11 +25,31 @@ fn coerce_primitive(value: Expr, p: &str) -> Expr {
     })
 }
 
+fn coercion_noop(value: Expr) -> Expr {
+    let decoder_ref_fn = Ident {
+        span: DUMMY_SP,
+        sym: format!("CoercionNoop").into(),
+        optional: false,
+    };
+    let callee = Callee::Expr(Expr::Ident(decoder_ref_fn).into());
+    Expr::Call(CallExpr {
+        span: DUMMY_SP,
+        callee: callee,
+        args: vec![ExprOrSpread {
+            spread: None,
+            expr: value.into(),
+        }],
+        type_args: None,
+    })
+}
+
 struct CoercerFnGenerator {}
 impl CoercerFnGenerator {
     fn coerce_schema(&mut self, schema: &JsonSchema, value_ref: &Expr, depth: usize) -> Expr {
         match schema {
-            JsonSchema::Null | JsonSchema::Const(_) | JsonSchema::Any => value_ref.clone(),
+            JsonSchema::Null | JsonSchema::Const(_) | JsonSchema::Any => {
+                coercion_noop(value_ref.clone())
+            }
             JsonSchema::Boolean => coerce_primitive(value_ref.clone(), "boolean"),
             JsonSchema::String => coerce_primitive(value_ref.clone(), "string"),
             JsonSchema::StringWithFormat(_) => coerce_primitive(value_ref.clone(), "string"),
@@ -90,7 +110,7 @@ impl CoercerFnGenerator {
         let input = SwcBuilder::input_expr();
         let stmts = vec![Stmt::Return(ReturnStmt {
             span: DUMMY_SP,
-            arg: Some(Box::new(self.coerce_schema(schema, &input, depth))),
+            arg: Some(self.coerce_schema(schema, &input, depth).into()),
         })];
 
         Function {
diff --git a/packages/beff-hono/CHANGELOG.md b/packages/beff-hono/CHANGELOG.md
index 89a00041..f8455326 100644
--- a/packages/beff-hono/CHANGELOG.md
+++ b/packages/beff-hono/CHANGELOG.md
@@ -1,5 +1,14 @@
 # @beff/hono
 
+## 0.0.8
+
+### Patch Changes
+
+- Support for optional parameters
+- Updated dependencies
+  - @beff/client@0.0.8
+  - @beff/cli@0.0.8
+
 ## 0.0.7
 
 ### Patch Changes
diff --git a/packages/beff-hono/package.json b/packages/beff-hono/package.json
index ff61e06d..cb4bf1d9 100644
--- a/packages/beff-hono/package.json
+++ b/packages/beff-hono/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@beff/hono",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "",
   "main": "dist/cjs/index.js",
   "scripts": {
@@ -18,8 +18,8 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7",
-    "@beff/client": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
+    "@beff/client": "workspace:^0.0.8",
     "hono": "^3.5.6",
     "vitest": "^0.34.3"
   },
diff --git a/packages/beff-hono/src/index.ts b/packages/beff-hono/src/index.ts
index 0e120bc0..1a95a704 100644
--- a/packages/beff-hono/src/index.ts
+++ b/packages/beff-hono/src/index.ts
@@ -76,7 +76,7 @@ const redocTemplate = (baseUrl: string) => `
 `;
 
 const coerce = (coercer: any, value: any): any => {
-  return coercer(value);
+  return coercer(value).data;
 };
 
 const toHonoPattern = (pattern: string): string => {
@@ -115,23 +115,7 @@ const prettyPrintErrorMessage = (it: DecodeError): string => {
   }
 };
 
-type CoercionFailure = {
-  __isCoercionFailure: true;
-  original: unknown;
-};
-
-const isCoercionFailure = (it: unknown): it is CoercionFailure => {
-  return (
-    typeof it === "object" &&
-    it != null &&
-    "__isCoercionFailure" in it &&
-    Boolean(it?.__isCoercionFailure)
-  );
-};
 const prettyPrintValue = (it: unknown): string => {
-  if (isCoercionFailure(it)) {
-    return prettyPrintValue(it.original);
-  }
   if (typeof it === "string") {
     return `"${it}"`;
   }
diff --git a/packages/beff-react/CHANGELOG.md b/packages/beff-react/CHANGELOG.md
index 5381dae4..50ff22da 100644
--- a/packages/beff-react/CHANGELOG.md
+++ b/packages/beff-react/CHANGELOG.md
@@ -1,5 +1,13 @@
 # @beff/react
 
+## 0.0.8
+
+### Patch Changes
+
+- Support for optional parameters
+- Updated dependencies
+  - @beff/client@0.0.8
+
 ## 0.0.7
 
 ### Patch Changes
diff --git a/packages/beff-react/package.json b/packages/beff-react/package.json
index 3b30a75d..d8c485fb 100644
--- a/packages/beff-react/package.json
+++ b/packages/beff-react/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@beff/react",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "",
   "main": "dist/cjs/index.js",
   "scripts": {
@@ -18,7 +18,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/client": "workspace:^0.0.7",
+    "@beff/client": "workspace:^0.0.8",
     "@tanstack/react-query": "^4.33.0",
     "react": "^18.2.0",
     "typescript": "^5.2.2"
diff --git a/packages/beff-wasm/CHANGELOG.md b/packages/beff-wasm/CHANGELOG.md
index 388f1b43..cb7d3d49 100644
--- a/packages/beff-wasm/CHANGELOG.md
+++ b/packages/beff-wasm/CHANGELOG.md
@@ -1,5 +1,11 @@
 # beff-vscode
 
+## 0.0.8
+
+### Patch Changes
+
+- Support for optional parameters
+
 ## 0.0.7
 
 ### Patch Changes
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/decoder/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/decoder/bff-generated/router.js
index 63827b3a..51331160 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/decoder/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/decoder/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/export-decoder/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/export-decoder/bff-generated/router.js
index e42168bc..4daf2ac8 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/export-decoder/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/export-decoder/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/hello-server/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/hello-server/bff-generated/router.js
index 7471a7f4..8d42b939 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/hello-server/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/hello-server/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/hono-context/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/hono-context/bff-generated/router.js
index 231fd360..138d62cb 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/hono-context/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/hono-context/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/qualified-nested/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/qualified-nested/bff-generated/router.js
index f416f212..53c25c58 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/qualified-nested/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/qualified-nested/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/codegen-snaps/qualified-types/bff-generated/router.js b/packages/beff-wasm/fixtures/codegen-snaps/qualified-types/bff-generated/router.js
index 675872cf..3f4f9419 100644
--- a/packages/beff-wasm/fixtures/codegen-snaps/qualified-types/bff-generated/router.js
+++ b/packages/beff-wasm/fixtures/codegen-snaps/qualified-types/bff-generated/router.js
@@ -1,44 +1,63 @@
 
 import vals from "./validators.js"; const { validators, add_path_to_errors, registerStringFormat, isCustomFormatInvalid } = vals;
 
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 
 const meta = [
diff --git a/packages/beff-wasm/fixtures/errors/pattern-args/stderr.log b/packages/beff-wasm/fixtures/errors/pattern-args/stderr.log
index 3c3c0735..bd5482e8 100644
--- a/packages/beff-wasm/fixtures/errors/pattern-args/stderr.log
+++ b/packages/beff-wasm/fixtures/errors/pattern-args/stderr.log
@@ -18,12 +18,12 @@ Error: Parameter pattern is not supported
    16 |     },
    17 |   },
 
-Error: Parameter pattern is not supported
+Error: Invalid context usage
  /errors/pattern-args/app.ts:19:17
    17 |   },
    18 |   [`/user2`]: {
  > 19 |     get: async (a: string[] = []): Promise<User[]> => {
-      |                 ^^^^^^^^^^^^^^^^ Parameter pattern is not supported
+      |                 ^^^^^^^^^^^ Context must be the first parameter
    20 |       return todo();
    21 |     },
    22 |   },
diff --git a/packages/beff-wasm/package.json b/packages/beff-wasm/package.json
index 05e62f06..03f7f631 100644
--- a/packages/beff-wasm/package.json
+++ b/packages/beff-wasm/package.json
@@ -1,7 +1,7 @@
 {
   "name": "beff-vscode",
   "publisher": "beff",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "",
   "engines": {
     "vscode": "^1.73.0"
@@ -40,8 +40,8 @@
   },
   "devDependencies": {
     "@babel/code-frame": "^7.22.13",
-    "@beff/cli": "workspace:^0.0.7",
-    "@beff/hono": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
+    "@beff/hono": "workspace:^0.0.8",
     "@types/babel__code-frame": "^7.0.3",
     "@types/node": "^20.5.7",
     "@types/vscode": "^1.73.0",
diff --git a/packages/beff-wasm/ts-node/bundle-to-disk.ts b/packages/beff-wasm/ts-node/bundle-to-disk.ts
index 97dc6bbe..23277de9 100644
--- a/packages/beff-wasm/ts-node/bundle-to-disk.ts
+++ b/packages/beff-wasm/ts-node/bundle-to-disk.ts
@@ -39,44 +39,63 @@ declare const _exports: { meta: HandlerMetaClient[] };
 export default _exports;
 `;
 const coercerCode = `
-class CoercionFailure {
-  constructor(original) {
-    this.__isCoercionFailure = true;
-    this.original = original
+
+function CoercionOk(data) {
+  return {
+    ok: true,
+    data,
   }
 }
+
+function CoercionNoop(data) {
+  return {
+    ok: false,
+    data,
+  }
+}
+  
+
 function coerce_string(input) {
-  return input;
+  if (typeof input === "string") {
+    return CoercionOk(input)
+  }
+  return CoercionNoop(input);
 }
 const isNumeric = (num) =>
   (typeof num === "number" || (typeof num === "string" && num.trim() !== "")) &&
   !isNaN(num );
 function coerce_number(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (isNumeric(input)) {
-    return Number(input);
+    return CoercionOk(Number(input));
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_boolean(input) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   if (input === "true" || input === "false") {
-    return input === "true";
+    return CoercionOk(input === "true");
   }
   if (input === "1" || input === "0") {
-    return input === "1";
+    return CoercionOk(input === "1");
   }
-  return new CoercionFailure(input);
+  return CoercionNoop(input);
 }
 function coerce_union(input, ...cases) {
+  if (input == null) {
+    return CoercionNoop(input);
+  }
   for (const c of cases) {
-    const r = coerce(c, input);
-    if (!(r instanceof CoercionFailure)) {
+    const r = c(input);
+    if (r.ok) {
       return r;
     }
   }
-  return new CoercionFailure(input);
-}
-function coerce(coercer, value) {
-  return coercer(value);
+  return CoercionNoop(input);
 }
 `;
 
diff --git a/packages/beff-wasm/vitest/params/__tests__/router.test.ts b/packages/beff-wasm/vitest/params/__tests__/router.test.ts
index a5f50b61..3b174ef6 100644
--- a/packages/beff-wasm/vitest/params/__tests__/router.test.ts
+++ b/packages/beff-wasm/vitest/params/__tests__/router.test.ts
@@ -97,3 +97,11 @@ it("coerce", async () => {
     '"456"'
   );
 });
+
+it("default param", async () => {
+  expect(await beff["/with-default"].get()).toMatchInlineSnapshot("1");
+  expect(await beff["/with-default"].post()).toMatchInlineSnapshot("1");
+
+  expect(await beff["/with-default"].get(5)).toMatchInlineSnapshot("5");
+  expect(await beff["/with-default"].post(5)).toMatchInlineSnapshot("5");
+});
diff --git a/packages/beff-wasm/vitest/params/router.ts b/packages/beff-wasm/vitest/params/router.ts
index 72af6c71..6e2d1a98 100644
--- a/packages/beff-wasm/vitest/params/router.ts
+++ b/packages/beff-wasm/vitest/params/router.ts
@@ -60,5 +60,13 @@ export default {
       return id;
     },
   },
+  "/with-default": {
+    get: async (c: Ctx, page: number = 1) => {
+      return page;
+    },
+    post: async (c: Ctx, page: number | undefined = 1) => {
+      return page;
+    },
+  },
 };
 type ValidIds = 123 | 456;
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 004f55df..d48e9a61 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -19,16 +19,16 @@ importers:
   examples/minimal-react:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-cli
       '@beff/client':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-client
       '@beff/hono':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-hono
       '@beff/react':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-react
       '@hono/node-server':
         specifier: ^1.1.1
@@ -80,10 +80,10 @@ importers:
   examples/node-server:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-cli
       '@beff/hono':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-hono
       '@hono/node-server':
         specifier: ^1.1.1
@@ -98,7 +98,7 @@ importers:
   examples/standalone-parser:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-cli
       vitest:
         specifier: ^0.34.3
@@ -109,7 +109,7 @@ importers:
   packages/beff-client:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-cli
     devDependencies:
       typescript:
@@ -121,10 +121,10 @@ importers:
   packages/beff-hono:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-cli
       '@beff/client':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-client
       hono:
         specifier: ^3.5.6
@@ -140,7 +140,7 @@ importers:
   packages/beff-react:
     dependencies:
       '@beff/client':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-client
       '@tanstack/react-query':
         specifier: ^4.33.0
@@ -162,10 +162,10 @@ importers:
         specifier: ^7.22.13
         version: 7.22.13
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-cli
       '@beff/hono':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../beff-hono
       '@types/babel__code-frame':
         specifier: ^7.0.3
@@ -201,10 +201,10 @@ importers:
   tests/node-docs:
     dependencies:
       '@beff/cli':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-cli
       '@beff/hono':
-        specifier: workspace:^0.0.7
+        specifier: workspace:^0.0.8
         version: link:../../packages/beff-hono
       '@hono/node-server':
         specifier: ^1.1.1
diff --git a/tests/node-docs/CHANGELOG.md b/tests/node-docs/CHANGELOG.md
index 08637c43..fc24beda 100644
--- a/tests/node-docs/CHANGELOG.md
+++ b/tests/node-docs/CHANGELOG.md
@@ -1,5 +1,13 @@
 # node-docs
 
+## 1.0.5
+
+### Patch Changes
+
+- Updated dependencies
+  - @beff/hono@0.0.8
+  - @beff/cli@0.0.8
+
 ## 1.0.4
 
 ### Patch Changes
diff --git a/tests/node-docs/package.json b/tests/node-docs/package.json
index 89ccbb8c..40d9d6a1 100644
--- a/tests/node-docs/package.json
+++ b/tests/node-docs/package.json
@@ -1,6 +1,6 @@
 {
   "name": "node-docs",
-  "version": "1.0.4",
+  "version": "1.0.5",
   "description": "",
   "main": "index.js",
   "scripts": {
@@ -13,8 +13,8 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@beff/cli": "workspace:^0.0.7",
-    "@beff/hono": "workspace:^0.0.7",
+    "@beff/cli": "workspace:^0.0.8",
+    "@beff/hono": "workspace:^0.0.8",
     "@hono/node-server": "^1.1.1",
     "esbuild": "^0.19.2",
     "vitest": "^0.34.3"