diff --git a/packages/contract/src/builder.ts b/packages/contract/src/builder.ts
index 93bcd552f..522a46069 100644
--- a/packages/contract/src/builder.ts
+++ b/packages/contract/src/builder.ts
@@ -187,7 +187,7 @@ export class ContractBuilder<
 }
 
 export const oc = new ContractBuilder<
-  Schema<unknown, unknown>,
+  Schema<void, void>,
   Schema<unknown, unknown>,
   Record<never, never>,
   Record<never, never>
diff --git a/packages/contract/src/default-void-input.test-d.ts b/packages/contract/src/default-void-input.test-d.ts
new file mode 100644
index 000000000..605b4fb55
--- /dev/null
+++ b/packages/contract/src/default-void-input.test-d.ts
@@ -0,0 +1,85 @@
+import type { Schema } from '@orpc/contract'
+import { expectTypeOf } from 'vitest'
+import { z } from 'zod'
+import { oc } from './builder'
+
+describe('default void input - contract - type tests', () => {
+  it('should infer void input type when input() is not specified', () => {
+    const contract = oc
+      .output(z.string())
+
+    type InputSchema = typeof contract extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should match explicit void input type', () => {
+    const contractWithoutInput = oc
+      .output(z.string())
+
+    const contractWithVoidInput = oc
+      .input(z.void())
+      .output(z.string())
+
+    type InputSchema1 = typeof contractWithoutInput extends { '~orpc': { inputSchema?: infer S } } ? S : never
+    type InputSchema2 = typeof contractWithVoidInput extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema1>().toEqualTypeOf<InputSchema2>()
+  })
+
+  it('should still allow explicit input schema to override', () => {
+    const contract = oc
+      .input(z.object({ name: z.string() }))
+      .output(z.string())
+
+    type InputSchema = typeof contract extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().not.toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work with metadata chaining', () => {
+    const contract = oc
+      .meta({ description: 'A test procedure' })
+      .output(z.string())
+
+    type InputSchema = typeof contract extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work with route definition', () => {
+    const contract = oc
+      .route({ method: 'GET', path: '/test' })
+      .output(z.string())
+
+    type InputSchema = typeof contract extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work with error mapping', () => {
+    const contract = oc
+      .errors({ NOT_FOUND: z.object({ message: z.string() }) })
+      .output(z.string())
+
+    type InputSchema = typeof contract extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work in contract router definition', () => {
+    const contractRouter = {
+      withoutInput: oc
+        .output(z.string()),
+      withInput: oc
+        .input(z.object({ id: z.string() }))
+        .output(z.string()),
+    }
+
+    type WithoutInputSchema = typeof contractRouter.withoutInput extends { '~orpc': { inputSchema?: infer S } } ? S : never
+    type WithInputSchema = typeof contractRouter.withInput extends { '~orpc': { inputSchema?: infer S } } ? S : never
+
+    expectTypeOf<WithoutInputSchema>().toEqualTypeOf<Schema<void, void>>()
+    expectTypeOf<WithInputSchema>().not.toEqualTypeOf<Schema<void, void>>()
+  })
+})
diff --git a/packages/contract/src/default-void-input.test.ts b/packages/contract/src/default-void-input.test.ts
new file mode 100644
index 000000000..83f928197
--- /dev/null
+++ b/packages/contract/src/default-void-input.test.ts
@@ -0,0 +1,76 @@
+import { z } from 'zod'
+import { oc } from './builder'
+import { isContractProcedure } from './procedure'
+
+describe('default void input - contract', () => {
+  it('should be a valid contract procedure', () => {
+    const contract = oc
+      .output(z.string())
+
+    expect(isContractProcedure(contract)).toBe(true)
+  })
+
+  it('should work with explicit void input same as default', () => {
+    const contractWithoutInput = oc
+      .output(z.string())
+
+    const contractWithVoidInput = oc
+      .input(z.void())
+      .output(z.string())
+
+    expect(isContractProcedure(contractWithoutInput)).toBe(true)
+    expect(isContractProcedure(contractWithVoidInput)).toBe(true)
+  })
+
+  it('should still work with explicit input schema', () => {
+    const contract = oc
+      .input(z.object({ name: z.string() }))
+      .output(z.string())
+
+    const inputSchema = contract['~orpc'].inputSchema
+
+    expect(inputSchema).toBeDefined()
+    expect(inputSchema?.['~standard'].vendor).toBe('zod')
+  })
+
+  it('should work in contract router without input()', () => {
+    const contractRouter = {
+      getAll: oc
+        .output(z.array(z.string())),
+      getOne: oc
+        .input(z.object({ id: z.string() }))
+        .output(z.string()),
+    }
+
+    expect(isContractProcedure(contractRouter.getAll)).toBe(true)
+    expect(isContractProcedure(contractRouter.getOne)).toBe(true)
+    expect(contractRouter.getOne['~orpc'].inputSchema).toBeDefined()
+  })
+
+  it('should allow metadata chaining with default void input', () => {
+    const contract = oc
+      .meta({ description: 'A test procedure' })
+      .output(z.string())
+
+    expect(isContractProcedure(contract)).toBe(true)
+    expect(contract['~orpc'].meta).toEqual({ description: 'A test procedure' })
+  })
+
+  it('should allow route definition with default void input', () => {
+    const contract = oc
+      .route({ method: 'GET', path: '/test' })
+      .output(z.string())
+
+    expect(isContractProcedure(contract)).toBe(true)
+    expect(contract['~orpc'].route).toEqual({ method: 'GET', path: '/test' })
+  })
+
+  it('should allow error mapping with default void input', () => {
+    const contract = oc
+      .errors({ NOT_FOUND: z.object({ message: z.string() }) })
+      .output(z.string())
+
+    expect(isContractProcedure(contract)).toBe(true)
+    expect(contract['~orpc'].errorMap).toHaveProperty('NOT_FOUND')
+  })
+})
diff --git a/packages/server/src/builder.ts b/packages/server/src/builder.ts
index c1afe03fe..3fc56dea5 100644
--- a/packages/server/src/builder.ts
+++ b/packages/server/src/builder.ts
@@ -336,7 +336,7 @@ export class Builder<
 export const os = new Builder<
   Record<never, never>,
   Record<never, never>,
-  Schema<unknown, unknown>,
+  Schema<void, void>,
   Schema<unknown, unknown>,
   Record<never, never>,
   Record<never, never>
diff --git a/packages/server/src/default-void-input.test-d.ts b/packages/server/src/default-void-input.test-d.ts
new file mode 100644
index 000000000..b92462084
--- /dev/null
+++ b/packages/server/src/default-void-input.test-d.ts
@@ -0,0 +1,86 @@
+import type { Schema } from '@orpc/contract'
+import { expectTypeOf } from 'vitest'
+import { z } from 'zod'
+import { os } from './builder'
+
+describe('default void input - type tests', () => {
+  it('should infer void input type when input() is not specified', () => {
+    const procedure = os
+      .output(z.string())
+      .handler(() => 'result')
+
+    type InputSchema = typeof procedure extends { '~orpc': { inputSchema: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should allow handler without input parameter when input() is not specified', () => {
+    const procedure = os
+      .output(z.string())
+      .handler(() => 'result')
+
+    expectTypeOf(procedure).toMatchTypeOf<{
+      '~orpc': {
+        inputSchema: Schema<void, void>
+        outputSchema: Schema<string, string>
+      }
+    }>()
+  })
+
+  it('should match explicit void input type', () => {
+    const procedureWithoutInput = os
+      .output(z.string())
+      .handler(() => 'result1')
+
+    const procedureWithVoidInput = os
+      .input(z.void())
+      .output(z.string())
+      .handler(() => 'result2')
+
+    type InputSchema1 = typeof procedureWithoutInput extends { '~orpc': { inputSchema: infer S } } ? S : never
+    type InputSchema2 = typeof procedureWithVoidInput extends { '~orpc': { inputSchema: infer S } } ? S : never
+
+    expectTypeOf<InputSchema1>().toEqualTypeOf<InputSchema2>()
+  })
+
+  it('should still allow explicit input schema to override', () => {
+    const procedure = os
+      .input(z.object({ name: z.string() }))
+      .output(z.string())
+      .handler(({ input }) => `Hello ${input.name}`)
+
+    type InputSchema = typeof procedure extends { '~orpc': { inputSchema: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().not.toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work with middleware chaining', () => {
+    const middleware = os.middleware(() => ({ context: { user: 'test' } }))
+
+    const procedure = middleware
+      .output(z.string())
+      .handler(({ context }) => `User: ${context.user}`)
+
+    type InputSchema = typeof procedure extends { '~orpc': { inputSchema: infer S } } ? S : never
+
+    expectTypeOf<InputSchema>().toEqualTypeOf<Schema<void, void>>()
+  })
+
+  it('should work in router definition', () => {
+    const testRouter = {
+      withoutInput: os
+        .output(z.string())
+        .handler(() => 'result'),
+      withInput: os
+        .input(z.object({ id: z.string() }))
+        .output(z.string())
+        .handler(({ input }) => `ID: ${input.id}`),
+    }
+
+    type WithoutInputSchema = typeof testRouter.withoutInput extends { '~orpc': { inputSchema: infer S } } ? S : never
+    type WithInputSchema = typeof testRouter.withInput extends { '~orpc': { inputSchema: infer S } } ? S : never
+
+    expectTypeOf<WithoutInputSchema>().toEqualTypeOf<Schema<void, void>>()
+    expectTypeOf<WithInputSchema>().not.toEqualTypeOf<Schema<void, void>>()
+  })
+})
diff --git a/packages/server/src/default-void-input.test.ts b/packages/server/src/default-void-input.test.ts
new file mode 100644
index 000000000..866214e9d
--- /dev/null
+++ b/packages/server/src/default-void-input.test.ts
@@ -0,0 +1,119 @@
+import { z } from 'zod'
+import { os } from './builder'
+
+describe('default void input', () => {
+  it('should accept no input when input() is not specified', async () => {
+    const procedure = os
+      .output(z.string())
+      .handler(() => 'result')
+
+    // Should work without providing input
+    const result = await procedure['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    expect(result).toBe('result')
+  })
+
+  it('should accept undefined as input when input() is not specified', async () => {
+    const procedure = os
+      .output(z.string())
+      .handler(() => 'result')
+
+    // Should work with undefined input
+    const result = await procedure['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    expect(result).toBe('result')
+  })
+
+  it('should work with explicit void input same as default', async () => {
+    const procedureWithoutInput = os
+      .output(z.string())
+      .handler(() => 'result1')
+
+    const procedureWithVoidInput = os
+      .input(z.void())
+      .output(z.string())
+      .handler(() => 'result2')
+
+    const result1 = await procedureWithoutInput['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    const result2 = await procedureWithVoidInput['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    expect(result1).toBe('result1')
+    expect(result2).toBe('result2')
+  })
+
+  it('should still work with explicit input schema', async () => {
+    const procedure = os
+      .input(z.object({ name: z.string() }))
+      .output(z.string())
+      .handler(({ input }) => `Hello ${input.name}`)
+
+    const result = await procedure['~orpc'].handler({
+      context: {},
+      input: { name: 'World' },
+      rawInput: { name: 'World' },
+    })
+
+    expect(result).toBe('Hello World')
+  })
+
+  it('should work after use() without explicit input()', async () => {
+    const middleware = ({ next }) => next()
+
+    const procedure = os
+      .use(middleware)
+      .output(z.string())
+      .handler(() => 'result after middleware')
+
+    const result = await procedure['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    expect(result).toBe('result after middleware')
+  })
+
+  it('should work in router without input()', async () => {
+    const testRouter = {
+      getAll: os
+        .output(z.array(z.string()))
+        .handler(() => ['item1', 'item2']),
+      getOne: os
+        .input(z.object({ id: z.string() }))
+        .output(z.string())
+        .handler(({ input }) => `Item: ${input.id}`),
+    }
+
+    const result1 = await testRouter.getAll['~orpc'].handler({
+      context: {},
+      input: undefined,
+      rawInput: undefined,
+    })
+
+    const result2 = await testRouter.getOne['~orpc'].handler({
+      context: {},
+      input: { id: '123' },
+      rawInput: { id: '123' },
+    })
+
+    expect(result1).toEqual(['item1', 'item2'])
+    expect(result2).toBe('Item: 123')
+  })
+})