From 7b9e1d94b3915da5085cf0fccff392db380f54fe Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 19:17:03 +0200
Subject: [PATCH 1/6] Transform JSON / JSONB parameter keys

---
 cf/src/connection.js   |  2 +-
 cf/src/types.js        |  8 +++++-
 cjs/src/connection.js  |  2 +-
 cjs/src/types.js       |  8 +++++-
 cjs/tests/index.js     | 61 ++++++++++++++++++++++++++++++++++++++++++
 deno/src/connection.js |  2 +-
 deno/src/types.js      |  8 +++++-
 deno/tests/index.js    | 61 ++++++++++++++++++++++++++++++++++++++++++
 deno/types/index.d.ts  | 30 ++++++++++++++-------
 src/connection.js      |  2 +-
 src/types.js           |  8 +++++-
 tests/index.js         | 61 ++++++++++++++++++++++++++++++++++++++++++
 types/index.d.ts       | 30 ++++++++++++++-------
 13 files changed, 257 insertions(+), 26 deletions(-)

diff --git a/cf/src/connection.js b/cf/src/connection.js
index 8e79170a..e1c1f1d2 100644
--- a/cf/src/connection.js
+++ b/cf/src/connection.js
@@ -959,7 +959,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x)
+        ? options.serializers[type](x, options)
         : '' + x
 
       prev = b.i
diff --git a/cf/src/types.js b/cf/src/types.js
index aa2ead29..dab82b02 100644
--- a/cf/src/types.js
+++ b/cf/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: x => JSON.stringify(x),
+    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -349,20 +349,26 @@ function createJsonTransform(fn) {
 toCamel.column = { from: toCamel }
 toCamel.value = { from: createJsonTransform(toCamel) }
 fromCamel.column = { to: fromCamel }
+fromCamel.value = { to: createJsonTransform(fromCamel) }
 
 export const camel = { ...toCamel }
 camel.column.to = fromCamel
+camel.value.to = fromCamel.value.to
 
 toPascal.column = { from: toPascal }
 toPascal.value = { from: createJsonTransform(toPascal) }
 fromPascal.column = { to: fromPascal }
+fromPascal.value = { to: createJsonTransform(fromPascal) }
 
 export const pascal = { ...toPascal }
 pascal.column.to = fromPascal
+pascal.value.to = fromPascal.value.to
 
 toKebab.column = { from: toKebab }
 toKebab.value = { from: createJsonTransform(toKebab) }
 fromKebab.column = { to: fromKebab }
+fromKebab.value = { to: createJsonTransform(fromKebab) }
 
 export const kebab = { ...toKebab }
 kebab.column.to = fromKebab
+kebab.value.to = fromKebab.value.to
diff --git a/cjs/src/connection.js b/cjs/src/connection.js
index 07f67167..4fe328aa 100644
--- a/cjs/src/connection.js
+++ b/cjs/src/connection.js
@@ -957,7 +957,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x)
+        ? options.serializers[type](x, options)
         : '' + x
 
       prev = b.i
diff --git a/cjs/src/types.js b/cjs/src/types.js
index 0578284c..79971466 100644
--- a/cjs/src/types.js
+++ b/cjs/src/types.js
@@ -16,7 +16,7 @@ const types = module.exports.types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: x => JSON.stringify(x),
+    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -348,20 +348,26 @@ function createJsonTransform(fn) {
 toCamel.column = { from: toCamel }
 toCamel.value = { from: createJsonTransform(toCamel) }
 fromCamel.column = { to: fromCamel }
+fromCamel.value = { to: createJsonTransform(fromCamel) }
 
 const camel = module.exports.camel = { ...toCamel }
 camel.column.to = fromCamel
+camel.value.to = fromCamel.value.to
 
 toPascal.column = { from: toPascal }
 toPascal.value = { from: createJsonTransform(toPascal) }
 fromPascal.column = { to: fromPascal }
+fromPascal.value = { to: createJsonTransform(fromPascal) }
 
 const pascal = module.exports.pascal = { ...toPascal }
 pascal.column.to = fromPascal
+pascal.value.to = fromPascal.value.to
 
 toKebab.column = { from: toKebab }
 toKebab.value = { from: createJsonTransform(toKebab) }
 fromKebab.column = { to: fromKebab }
+fromKebab.value = { to: createJsonTransform(fromKebab) }
 
 const kebab = module.exports.kebab = { ...toKebab }
 kebab.column.to = fromKebab
+kebab.value.to = fromKebab.value.to
diff --git a/cjs/tests/index.js b/cjs/tests/index.js
index 85d1aa46..44fd1ca5 100644
--- a/cjs/tests/index.js
+++ b/cjs/tests/index.js
@@ -106,6 +106,67 @@ t('Json', async() => {
   return ['hello,42', [x.a, x.b].join()]
 })
 
+t('Json transform parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform nested parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`
+    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+  `)[0].x
+  return ['Grace', x]
+})
+
+t('Json transform result keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
+  return ['Ada', x.firstName]
+})
+
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json type parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform typed json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/deno/src/connection.js b/deno/src/connection.js
index 796725de..8f63335d 100644
--- a/deno/src/connection.js
+++ b/deno/src/connection.js
@@ -960,7 +960,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x)
+        ? options.serializers[type](x, options)
         : '' + x
 
       prev = b.i
diff --git a/deno/src/types.js b/deno/src/types.js
index ea0da6a2..54e99acd 100644
--- a/deno/src/types.js
+++ b/deno/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: x => JSON.stringify(x),
+    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -349,20 +349,26 @@ function createJsonTransform(fn) {
 toCamel.column = { from: toCamel }
 toCamel.value = { from: createJsonTransform(toCamel) }
 fromCamel.column = { to: fromCamel }
+fromCamel.value = { to: createJsonTransform(fromCamel) }
 
 export const camel = { ...toCamel }
 camel.column.to = fromCamel
+camel.value.to = fromCamel.value.to
 
 toPascal.column = { from: toPascal }
 toPascal.value = { from: createJsonTransform(toPascal) }
 fromPascal.column = { to: fromPascal }
+fromPascal.value = { to: createJsonTransform(fromPascal) }
 
 export const pascal = { ...toPascal }
 pascal.column.to = fromPascal
+pascal.value.to = fromPascal.value.to
 
 toKebab.column = { from: toKebab }
 toKebab.value = { from: createJsonTransform(toKebab) }
 fromKebab.column = { to: fromKebab }
+fromKebab.value = { to: createJsonTransform(fromKebab) }
 
 export const kebab = { ...toKebab }
 kebab.column.to = fromKebab
+kebab.value.to = fromKebab.value.to
diff --git a/deno/tests/index.js b/deno/tests/index.js
index cc2a2518..f8cfe666 100644
--- a/deno/tests/index.js
+++ b/deno/tests/index.js
@@ -108,6 +108,67 @@ t('Json', async() => {
   return ['hello,42', [x.a, x.b].join()]
 })
 
+t('Json transform parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform nested parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`
+    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+  `)[0].x
+  return ['Grace', x]
+})
+
+t('Json transform result keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
+  return ['Ada', x.firstName]
+})
+
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json type parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform typed json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/deno/types/index.d.ts b/deno/types/index.d.ts
index 85112eda..c363b1f6 100644
--- a/deno/types/index.d.ts
+++ b/deno/types/index.d.ts
@@ -236,7 +236,7 @@ declare namespace postgres {
   function toPascal(str: string): string;
   namespace toPascal {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a PascalCase string to snake_case.
@@ -246,6 +246,7 @@ declare namespace postgres {
   function fromPascal(str: string): string;
   namespace fromPascal {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from PascalCase.
@@ -255,7 +256,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
   /**
    * Convert a snake_case string to camelCase.
@@ -265,7 +269,7 @@ declare namespace postgres {
   function toCamel(str: string): string;
   namespace toCamel {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a camelCase string to snake_case.
@@ -275,6 +279,7 @@ declare namespace postgres {
   function fromCamel(str: string): string;
   namespace fromCamel {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from camelCase.
@@ -284,7 +289,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
   /**
    * Convert a snake_case string to kebab-case.
@@ -294,7 +302,7 @@ declare namespace postgres {
   function toKebab(str: string): string;
   namespace toKebab {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a kebab-case string to snake_case.
@@ -304,6 +312,7 @@ declare namespace postgres {
   function fromKebab(str: string): string;
   namespace fromKebab {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from kebab-case.
@@ -313,7 +322,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
 
   const BigInt: PostgresType<bigint>;
@@ -321,7 +333,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T) => unknown;
+    serialize: (value: T, options?: ParsedOptions) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -386,7 +398,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any) => unknown>;
+    serializers: Record<number, (value: any, options?: ParsedOptions) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 
@@ -404,7 +416,7 @@ declare namespace postgres {
       /** Transform function for values in result rows */
       from: ((value: any, column?: Column<string>) => any) | undefined;
       /** Transform function for interpolated values passed to tagged template literal */
-      to: undefined; // (value: any) => any
+      to: ((value: any, column?: Column<string>) => any) | undefined;
     };
     row: {
       /** Transform function for entire result rows */
diff --git a/src/connection.js b/src/connection.js
index 1b1cccde..858535c2 100644
--- a/src/connection.js
+++ b/src/connection.js
@@ -957,7 +957,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x)
+        ? options.serializers[type](x, options)
         : '' + x
 
       prev = b.i
diff --git a/src/types.js b/src/types.js
index 7c7c2b93..ce12ef74 100644
--- a/src/types.js
+++ b/src/types.js
@@ -16,7 +16,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: x => JSON.stringify(x),
+    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -348,20 +348,26 @@ function createJsonTransform(fn) {
 toCamel.column = { from: toCamel }
 toCamel.value = { from: createJsonTransform(toCamel) }
 fromCamel.column = { to: fromCamel }
+fromCamel.value = { to: createJsonTransform(fromCamel) }
 
 export const camel = { ...toCamel }
 camel.column.to = fromCamel
+camel.value.to = fromCamel.value.to
 
 toPascal.column = { from: toPascal }
 toPascal.value = { from: createJsonTransform(toPascal) }
 fromPascal.column = { to: fromPascal }
+fromPascal.value = { to: createJsonTransform(fromPascal) }
 
 export const pascal = { ...toPascal }
 pascal.column.to = fromPascal
+pascal.value.to = fromPascal.value.to
 
 toKebab.column = { from: toKebab }
 toKebab.value = { from: createJsonTransform(toKebab) }
 fromKebab.column = { to: fromKebab }
+fromKebab.value = { to: createJsonTransform(fromKebab) }
 
 export const kebab = { ...toKebab }
 kebab.column.to = fromKebab
+kebab.value.to = fromKebab.value.to
diff --git a/tests/index.js b/tests/index.js
index 23e6c4d4..0687cdac 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -106,6 +106,67 @@ t('Json', async() => {
   return ['hello,42', [x.a, x.b].join()]
 })
 
+t('Json transform parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform nested parameter keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`
+    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+  `)[0].x
+  return ['Grace', x]
+})
+
+t('Json transform result keys', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
+  return ['Ada', x.firstName]
+})
+
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform implicit json type parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
+t('Json transform typed json parameters', async() => {
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
+  return ['Ada', x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/types/index.d.ts b/types/index.d.ts
index 13c3432f..627d3ebd 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -234,7 +234,7 @@ declare namespace postgres {
   function toPascal(str: string): string;
   namespace toPascal {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a PascalCase string to snake_case.
@@ -244,6 +244,7 @@ declare namespace postgres {
   function fromPascal(str: string): string;
   namespace fromPascal {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from PascalCase.
@@ -253,7 +254,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
   /**
    * Convert a snake_case string to camelCase.
@@ -263,7 +267,7 @@ declare namespace postgres {
   function toCamel(str: string): string;
   namespace toCamel {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a camelCase string to snake_case.
@@ -273,6 +277,7 @@ declare namespace postgres {
   function fromCamel(str: string): string;
   namespace fromCamel {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from camelCase.
@@ -282,7 +287,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
   /**
    * Convert a snake_case string to kebab-case.
@@ -292,7 +300,7 @@ declare namespace postgres {
   function toKebab(str: string): string;
   namespace toKebab {
     namespace column { function from(str: string): string; }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value { function from(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert a kebab-case string to snake_case.
@@ -302,6 +310,7 @@ declare namespace postgres {
   function fromKebab(str: string): string;
   namespace fromKebab {
     namespace column { function to(str: string): string }
+    namespace value { function to(str: unknown, column: Column<string>): unknown }
   }
   /**
    * Convert snake_case to and from kebab-case.
@@ -311,7 +320,10 @@ declare namespace postgres {
       function from(str: string): string;
       function to(str: string): string;
     }
-    namespace value { function from(str: unknown, column: Column<string>): string }
+    namespace value {
+      function from(str: unknown, column: Column<string>): unknown;
+      function to(str: unknown, column: Column<string>): unknown;
+    }
   }
 
   const BigInt: PostgresType<bigint>;
@@ -319,7 +331,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T) => unknown;
+    serialize: (value: T, options?: ParsedOptions) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -384,7 +396,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any) => unknown>;
+    serializers: Record<number, (value: any, options?: ParsedOptions) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 
@@ -402,7 +414,7 @@ declare namespace postgres {
       /** Transform function for values in result rows */
       from: ((value: any, column?: Column<string>) => any) | undefined;
       /** Transform function for interpolated values passed to tagged template literal */
-      to: undefined; // (value: any) => any
+      to: ((value: any, column?: Column<string>) => any) | undefined;
     };
     row: {
       /** Transform function for entire result rows */

From 7c2916c199330a53f9d15ec7303f2fa49becfbe1 Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 19:28:44 +0200
Subject: [PATCH 2/6] Make test data consistent with existing test data

---
 cjs/tests/index.js  | 28 ++++++++++++++--------------
 deno/tests/index.js | 28 ++++++++++++++--------------
 tests/index.js      | 28 ++++++++++++++--------------
 3 files changed, 42 insertions(+), 42 deletions(-)

diff --git a/cjs/tests/index.js b/cjs/tests/index.js
index 44fd1ca5..f2d440a0 100644
--- a/cjs/tests/index.js
+++ b/cjs/tests/index.js
@@ -111,8 +111,8 @@ t('Json transform parameter keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform nested parameter keys', async() => {
@@ -121,9 +121,9 @@ t('Json transform nested parameter keys', async() => {
     transform: postgres.camel
   })
   const x = (await sql`
-    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+    select ${ sql.json({ aTest: [{ bTest: 1 }, { bTest: 2 }] }) }#>>'{a_test,1,b_test}' as x
   `)[0].x
-  return ['Grace', x]
+  return ['2', x]
 })
 
 t('Json transform result keys', async() => {
@@ -131,13 +131,13 @@ t('Json transform result keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
-  return ['Ada', x.firstName]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
 t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json parameters', async() => {
@@ -145,8 +145,8 @@ t('Json transform implicit json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::jsonb->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json type parameters', async() => {
@@ -154,8 +154,8 @@ t('Json transform implicit json type parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::json->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform typed json parameters', async() => {
@@ -163,8 +163,8 @@ t('Json transform typed json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('implicit json', async() => {
diff --git a/deno/tests/index.js b/deno/tests/index.js
index f8cfe666..9442e1eb 100644
--- a/deno/tests/index.js
+++ b/deno/tests/index.js
@@ -113,8 +113,8 @@ t('Json transform parameter keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform nested parameter keys', async() => {
@@ -123,9 +123,9 @@ t('Json transform nested parameter keys', async() => {
     transform: postgres.camel
   })
   const x = (await sql`
-    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+    select ${ sql.json({ aTest: [{ bTest: 1 }, { bTest: 2 }] }) }#>>'{a_test,1,b_test}' as x
   `)[0].x
-  return ['Grace', x]
+  return ['2', x]
 })
 
 t('Json transform result keys', async() => {
@@ -133,13 +133,13 @@ t('Json transform result keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
-  return ['Ada', x.firstName]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
 t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json parameters', async() => {
@@ -147,8 +147,8 @@ t('Json transform implicit json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::jsonb->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json type parameters', async() => {
@@ -156,8 +156,8 @@ t('Json transform implicit json type parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::json->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform typed json parameters', async() => {
@@ -165,8 +165,8 @@ t('Json transform typed json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('implicit json', async() => {
diff --git a/tests/index.js b/tests/index.js
index 0687cdac..dd873ff8 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -111,8 +111,8 @@ t('Json transform parameter keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform nested parameter keys', async() => {
@@ -121,9 +121,9 @@ t('Json transform nested parameter keys', async() => {
     transform: postgres.camel
   })
   const x = (await sql`
-    select ${ sql.json({ userNames: [{ firstName: 'Ada' }, { firstName: 'Grace' }] }) }#>>'{user_names,1,first_name}' as x
+    select ${ sql.json({ aTest: [{ bTest: 1 }, { bTest: 2 }] }) }#>>'{a_test,1,b_test}' as x
   `)[0].x
-  return ['Grace', x]
+  return ['2', x]
 })
 
 t('Json transform result keys', async() => {
@@ -131,13 +131,13 @@ t('Json transform result keys', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"first_name":"Ada"}'::jsonb as x`)[0].x
-  return ['Ada', x.firstName]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
 t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ firstName: 'Ada' }) }->>'firstName' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json parameters', async() => {
@@ -145,8 +145,8 @@ t('Json transform implicit json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::jsonb->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::jsonb->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform implicit json type parameters', async() => {
@@ -154,8 +154,8 @@ t('Json transform implicit json type parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ { firstName: 'Ada' } }::json->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ { aTest: 1 } }::json->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('Json transform typed json parameters', async() => {
@@ -163,8 +163,8 @@ t('Json transform typed json parameters', async() => {
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ firstName: 'Ada' }, 114) }->>'first_name' as x`)[0].x
-  return ['Ada', x]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
 t('implicit json', async() => {

From 43bb705ff1598d97cfd624b8e614013e67171562 Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 21:41:30 +0200
Subject: [PATCH 3/6] Preserve non-plain JSON parameter values

---
 cf/src/connection.js   |  2 +-
 cf/src/types.js        |  6 ++++--
 cjs/src/connection.js  |  2 +-
 cjs/src/types.js       |  6 ++++--
 cjs/tests/index.js     | 10 ++++++++++
 deno/src/connection.js |  2 +-
 deno/src/types.js      |  6 ++++--
 deno/tests/index.js    | 10 ++++++++++
 deno/types/index.d.ts  |  4 ++--
 src/connection.js      |  2 +-
 src/types.js           |  6 ++++--
 tests/index.js         | 10 ++++++++++
 types/index.d.ts       |  4 ++--
 13 files changed, 54 insertions(+), 16 deletions(-)

diff --git a/cf/src/connection.js b/cf/src/connection.js
index e1c1f1d2..bd9b9a58 100644
--- a/cf/src/connection.js
+++ b/cf/src/connection.js
@@ -959,7 +959,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options)
+        ? options.serializers[type](x, options, type)
         : '' + x
 
       prev = b.i
diff --git a/cf/src/types.js b/cf/src/types.js
index dab82b02..79b642ad 100644
--- a/cf/src/types.js
+++ b/cf/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
+    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -341,7 +341,9 @@ function createJsonTransform(fn) {
     return typeof x === 'object' && x !== null && (column.type === 114 || column.type === 3802)
       ? Array.isArray(x)
         ? x.map(x => jsonTransform(x, column))
-        : Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+        : Object.getPrototypeOf(x) === Object.prototype || Object.getPrototypeOf(x) === null
+          ? Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+          : x
       : x
   }
 }
diff --git a/cjs/src/connection.js b/cjs/src/connection.js
index 4fe328aa..a120bd0c 100644
--- a/cjs/src/connection.js
+++ b/cjs/src/connection.js
@@ -957,7 +957,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options)
+        ? options.serializers[type](x, options, type)
         : '' + x
 
       prev = b.i
diff --git a/cjs/src/types.js b/cjs/src/types.js
index 79971466..67facb87 100644
--- a/cjs/src/types.js
+++ b/cjs/src/types.js
@@ -16,7 +16,7 @@ const types = module.exports.types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
+    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -340,7 +340,9 @@ function createJsonTransform(fn) {
     return typeof x === 'object' && x !== null && (column.type === 114 || column.type === 3802)
       ? Array.isArray(x)
         ? x.map(x => jsonTransform(x, column))
-        : Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+        : Object.getPrototypeOf(x) === Object.prototype || Object.getPrototypeOf(x) === null
+          ? Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+          : x
       : x
   }
 }
diff --git a/cjs/tests/index.js b/cjs/tests/index.js
index f2d440a0..97378295 100644
--- a/cjs/tests/index.js
+++ b/cjs/tests/index.js
@@ -167,6 +167,16 @@ t('Json transform typed json parameters', async() => {
   return ['1', x]
 })
 
+t('Json transform toJSON parameter values', async() => {
+  const now = new Date()
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ aTest: now }) }->>'a_test' as x`)[0].x
+  return [now.toJSON(), x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/deno/src/connection.js b/deno/src/connection.js
index 8f63335d..7dd619de 100644
--- a/deno/src/connection.js
+++ b/deno/src/connection.js
@@ -960,7 +960,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options)
+        ? options.serializers[type](x, options, type)
         : '' + x
 
       prev = b.i
diff --git a/deno/src/types.js b/deno/src/types.js
index 54e99acd..0167d171 100644
--- a/deno/src/types.js
+++ b/deno/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
+    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -341,7 +341,9 @@ function createJsonTransform(fn) {
     return typeof x === 'object' && x !== null && (column.type === 114 || column.type === 3802)
       ? Array.isArray(x)
         ? x.map(x => jsonTransform(x, column))
-        : Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+        : Object.getPrototypeOf(x) === Object.prototype || Object.getPrototypeOf(x) === null
+          ? Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+          : x
       : x
   }
 }
diff --git a/deno/tests/index.js b/deno/tests/index.js
index 9442e1eb..f957f6b5 100644
--- a/deno/tests/index.js
+++ b/deno/tests/index.js
@@ -169,6 +169,16 @@ t('Json transform typed json parameters', async() => {
   return ['1', x]
 })
 
+t('Json transform toJSON parameter values', async() => {
+  const now = new Date()
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ aTest: now }) }->>'a_test' as x`)[0].x
+  return [now.toJSON(), x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/deno/types/index.d.ts b/deno/types/index.d.ts
index c363b1f6..608d4c19 100644
--- a/deno/types/index.d.ts
+++ b/deno/types/index.d.ts
@@ -333,7 +333,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T, options?: ParsedOptions) => unknown;
+    serialize: (value: T, options?: ParsedOptions, type?: number) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -398,7 +398,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any, options?: ParsedOptions) => unknown>;
+    serializers: Record<number, (value: any, options?: ParsedOptions, type?: number) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 
diff --git a/src/connection.js b/src/connection.js
index 858535c2..f126036f 100644
--- a/src/connection.js
+++ b/src/connection.js
@@ -957,7 +957,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
 
       type = types[i]
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options)
+        ? options.serializers[type](x, options, type)
         : '' + x
 
       prev = b.i
diff --git a/src/types.js b/src/types.js
index ce12ef74..20f775df 100644
--- a/src/types.js
+++ b/src/types.js
@@ -16,7 +16,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type: 3802 }) : x),
+    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
     parse: x => JSON.parse(x)
   },
   boolean: {
@@ -340,7 +340,9 @@ function createJsonTransform(fn) {
     return typeof x === 'object' && x !== null && (column.type === 114 || column.type === 3802)
       ? Array.isArray(x)
         ? x.map(x => jsonTransform(x, column))
-        : Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+        : Object.getPrototypeOf(x) === Object.prototype || Object.getPrototypeOf(x) === null
+          ? Object.entries(x).reduce((acc, [k, v]) => Object.assign(acc, { [fn(k)]: jsonTransform(v, column) }), {})
+          : x
       : x
   }
 }
diff --git a/tests/index.js b/tests/index.js
index dd873ff8..fbf9f339 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -167,6 +167,16 @@ t('Json transform typed json parameters', async() => {
   return ['1', x]
 })
 
+t('Json transform toJSON parameter values', async() => {
+  const now = new Date()
+  const sql = postgres({
+    ...options,
+    transform: postgres.camel
+  })
+  const x = (await sql`select ${ sql.json({ aTest: now }) }->>'a_test' as x`)[0].x
+  return [now.toJSON(), x]
+})
+
 t('implicit json', async() => {
   const x = (await sql`select ${ { a: 'hello', b: 42 } }::json as x`)[0].x
   return ['hello,42', [x.a, x.b].join()]
diff --git a/types/index.d.ts b/types/index.d.ts
index 627d3ebd..3a2c025d 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -331,7 +331,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T, options?: ParsedOptions) => unknown;
+    serialize: (value: T, options?: ParsedOptions, type?: number) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -396,7 +396,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any, options?: ParsedOptions) => unknown>;
+    serializers: Record<number, (value: any, options?: ParsedOptions, type?: number) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 

From e3059aa718dab4db8e6af9caecb4d9f2637acf36 Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 22:11:05 +0200
Subject: [PATCH 4/6] Apply value transforms before serialization

---
 cf/src/connection.js   | 3 ++-
 cf/src/types.js        | 2 +-
 cjs/src/connection.js  | 3 ++-
 cjs/src/types.js       | 2 +-
 deno/src/connection.js | 3 ++-
 deno/src/types.js      | 2 +-
 deno/types/index.d.ts  | 4 ++--
 src/connection.js      | 3 ++-
 src/types.js           | 2 +-
 types/index.d.ts       | 4 ++--
 10 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/cf/src/connection.js b/cf/src/connection.js
index bd9b9a58..1b768cfc 100644
--- a/cf/src/connection.js
+++ b/cf/src/connection.js
@@ -958,8 +958,9 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
         return b.i32(0xFFFFFFFF)
 
       type = types[i]
+      x = options.transform.value.to ? options.transform.value.to(x, { type }) : x
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options, type)
+        ? options.serializers[type](x)
         : '' + x
 
       prev = b.i
diff --git a/cf/src/types.js b/cf/src/types.js
index 79b642ad..712ee1b4 100644
--- a/cf/src/types.js
+++ b/cf/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
+    serialize: x => JSON.stringify(x),
     parse: x => JSON.parse(x)
   },
   boolean: {
diff --git a/cjs/src/connection.js b/cjs/src/connection.js
index a120bd0c..4ce3f9b3 100644
--- a/cjs/src/connection.js
+++ b/cjs/src/connection.js
@@ -956,8 +956,9 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
         return b.i32(0xFFFFFFFF)
 
       type = types[i]
+      x = options.transform.value.to ? options.transform.value.to(x, { type }) : x
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options, type)
+        ? options.serializers[type](x)
         : '' + x
 
       prev = b.i
diff --git a/cjs/src/types.js b/cjs/src/types.js
index 67facb87..44a35068 100644
--- a/cjs/src/types.js
+++ b/cjs/src/types.js
@@ -16,7 +16,7 @@ const types = module.exports.types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
+    serialize: x => JSON.stringify(x),
     parse: x => JSON.parse(x)
   },
   boolean: {
diff --git a/deno/src/connection.js b/deno/src/connection.js
index 7dd619de..bce667e3 100644
--- a/deno/src/connection.js
+++ b/deno/src/connection.js
@@ -959,8 +959,9 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
         return b.i32(0xFFFFFFFF)
 
       type = types[i]
+      x = options.transform.value.to ? options.transform.value.to(x, { type }) : x
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options, type)
+        ? options.serializers[type](x)
         : '' + x
 
       prev = b.i
diff --git a/deno/src/types.js b/deno/src/types.js
index 0167d171..6e57930b 100644
--- a/deno/src/types.js
+++ b/deno/src/types.js
@@ -17,7 +17,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
+    serialize: x => JSON.stringify(x),
     parse: x => JSON.parse(x)
   },
   boolean: {
diff --git a/deno/types/index.d.ts b/deno/types/index.d.ts
index 608d4c19..36613696 100644
--- a/deno/types/index.d.ts
+++ b/deno/types/index.d.ts
@@ -333,7 +333,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T, options?: ParsedOptions, type?: number) => unknown;
+    serialize: (value: T) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -398,7 +398,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any, options?: ParsedOptions, type?: number) => unknown>;
+    serializers: Record<number, (value: any) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 
diff --git a/src/connection.js b/src/connection.js
index f126036f..0513ce4e 100644
--- a/src/connection.js
+++ b/src/connection.js
@@ -956,8 +956,9 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
         return b.i32(0xFFFFFFFF)
 
       type = types[i]
+      x = options.transform.value.to ? options.transform.value.to(x, { type }) : x
       parameters[i] = x = type in options.serializers
-        ? options.serializers[type](x, options, type)
+        ? options.serializers[type](x)
         : '' + x
 
       prev = b.i
diff --git a/src/types.js b/src/types.js
index 20f775df..58ce74cb 100644
--- a/src/types.js
+++ b/src/types.js
@@ -16,7 +16,7 @@ export const types = {
   json: {
     to: 114,
     from: [114, 3802],
-    serialize: (x, options, type) => JSON.stringify(options && options.transform.value.to ? options.transform.value.to(x, { type }) : x),
+    serialize: x => JSON.stringify(x),
     parse: x => JSON.parse(x)
   },
   boolean: {
diff --git a/types/index.d.ts b/types/index.d.ts
index 3a2c025d..c165c452 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -331,7 +331,7 @@ declare namespace postgres {
   interface PostgresType<T = any> {
     to: number;
     from: number[];
-    serialize: (value: T, options?: ParsedOptions, type?: number) => unknown;
+    serialize: (value: T) => unknown;
     parse: (raw: any) => T;
   }
 
@@ -396,7 +396,7 @@ declare namespace postgres {
     pass: null;
     /** @inheritdoc */
     transform: Transform;
-    serializers: Record<number, (value: any, options?: ParsedOptions, type?: number) => unknown>;
+    serializers: Record<number, (value: any) => unknown>;
     parsers: Record<number, (value: any) => unknown>;
   }
 

From 690f730802493226888b933e681c36673bef5de6 Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 22:22:08 +0200
Subject: [PATCH 5/6] Move negative test up

---
 cjs/tests/index.js  | 10 +++++-----
 deno/tests/index.js | 10 +++++-----
 tests/index.js      | 10 +++++-----
 3 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/cjs/tests/index.js b/cjs/tests/index.js
index 97378295..52d737a9 100644
--- a/cjs/tests/index.js
+++ b/cjs/tests/index.js
@@ -115,6 +115,11 @@ t('Json transform parameter keys', async() => {
   return ['1', x]
 })
 
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
+})
+
 t('Json transform nested parameter keys', async() => {
   const sql = postgres({
     ...options,
@@ -135,11 +140,6 @@ t('Json transform result keys', async() => {
   return [1, x.aTest]
 })
 
-t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
-  return ['1', x]
-})
-
 t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,
diff --git a/deno/tests/index.js b/deno/tests/index.js
index f957f6b5..2e49c075 100644
--- a/deno/tests/index.js
+++ b/deno/tests/index.js
@@ -117,6 +117,11 @@ t('Json transform parameter keys', async() => {
   return ['1', x]
 })
 
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
+})
+
 t('Json transform nested parameter keys', async() => {
   const sql = postgres({
     ...options,
@@ -137,11 +142,6 @@ t('Json transform result keys', async() => {
   return [1, x.aTest]
 })
 
-t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
-  return ['1', x]
-})
-
 t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,
diff --git a/tests/index.js b/tests/index.js
index fbf9f339..58a2cc1d 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -115,6 +115,11 @@ t('Json transform parameter keys', async() => {
   return ['1', x]
 })
 
+t('Json without transform keeps parameter keys', async() => {
+  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
+  return ['1', x]
+})
+
 t('Json transform nested parameter keys', async() => {
   const sql = postgres({
     ...options,
@@ -135,11 +140,6 @@ t('Json transform result keys', async() => {
   return [1, x.aTest]
 })
 
-t('Json without transform keeps parameter keys', async() => {
-  const x = (await sql`select ${ sql.json({ aTest: 1 }) }->>'aTest' as x`)[0].x
-  return ['1', x]
-})
-
 t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,

From 5d73037d48a2c9afea66ca9490dffa287fe5fe96 Mon Sep 17 00:00:00 2001
From: Karl Horky <karl.horky@gmail.com>
Date: Wed, 27 May 2026 22:54:38 +0200
Subject: [PATCH 6/6] Order tests with interpolation first

---
 cjs/tests/index.js  | 18 +++++++++---------
 deno/tests/index.js | 18 +++++++++---------
 tests/index.js      | 18 +++++++++---------
 3 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/cjs/tests/index.js b/cjs/tests/index.js
index 52d737a9..83970b5d 100644
--- a/cjs/tests/index.js
+++ b/cjs/tests/index.js
@@ -131,16 +131,16 @@ t('Json transform nested parameter keys', async() => {
   return ['2', x]
 })
 
-t('Json transform result keys', async() => {
+t('Json transform typed json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
-  return [1, x.aTest]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
-t('Json transform implicit json parameters', async() => {
+t('Json transform implicit jsonb parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -149,7 +149,7 @@ t('Json transform implicit json parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform implicit json type parameters', async() => {
+t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -158,16 +158,16 @@ t('Json transform implicit json type parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform typed json parameters', async() => {
+t('Json transform result keys', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
-  return ['1', x]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
-t('Json transform toJSON parameter values', async() => {
+t('Json transform does not transform parameter values with .toJSON()', async() => {
   const now = new Date()
   const sql = postgres({
     ...options,
diff --git a/deno/tests/index.js b/deno/tests/index.js
index 2e49c075..4542db42 100644
--- a/deno/tests/index.js
+++ b/deno/tests/index.js
@@ -133,16 +133,16 @@ t('Json transform nested parameter keys', async() => {
   return ['2', x]
 })
 
-t('Json transform result keys', async() => {
+t('Json transform typed json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
-  return [1, x.aTest]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
-t('Json transform implicit json parameters', async() => {
+t('Json transform implicit jsonb parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -151,7 +151,7 @@ t('Json transform implicit json parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform implicit json type parameters', async() => {
+t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -160,16 +160,16 @@ t('Json transform implicit json type parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform typed json parameters', async() => {
+t('Json transform result keys', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
-  return ['1', x]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
-t('Json transform toJSON parameter values', async() => {
+t('Json transform does not transform parameter values with .toJSON()', async() => {
   const now = new Date()
   const sql = postgres({
     ...options,
diff --git a/tests/index.js b/tests/index.js
index 58a2cc1d..55b54ad7 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -131,16 +131,16 @@ t('Json transform nested parameter keys', async() => {
   return ['2', x]
 })
 
-t('Json transform result keys', async() => {
+t('Json transform typed json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
-  return [1, x.aTest]
+  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
+  return ['1', x]
 })
 
-t('Json transform implicit json parameters', async() => {
+t('Json transform implicit jsonb parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -149,7 +149,7 @@ t('Json transform implicit json parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform implicit json type parameters', async() => {
+t('Json transform implicit json parameters', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
@@ -158,16 +158,16 @@ t('Json transform implicit json type parameters', async() => {
   return ['1', x]
 })
 
-t('Json transform typed json parameters', async() => {
+t('Json transform result keys', async() => {
   const sql = postgres({
     ...options,
     transform: postgres.camel
   })
-  const x = (await sql`select ${ sql.typed({ aTest: 1 }, 114) }->>'a_test' as x`)[0].x
-  return ['1', x]
+  const x = (await sql`select '{"a_test":1}'::jsonb as x`)[0].x
+  return [1, x.aTest]
 })
 
-t('Json transform toJSON parameter values', async() => {
+t('Json transform does not transform parameter values with .toJSON()', async() => {
   const now = new Date()
   const sql = postgres({
     ...options,