diff --git a/.changeset/shaggy-mugs-agree.md b/.changeset/shaggy-mugs-agree.md
new file mode 100644
index 0000000000..fba6ebfeb0
--- /dev/null
+++ b/.changeset/shaggy-mugs-agree.md
@@ -0,0 +1,8 @@
+---
+"graphile-build-pg": patch
+"postgraphile": patch
+"@dataplan/pg": patch
+---
+
+Tweak some types to allow defining the types of the final PgRegistry via
+declaration merging (requires codegen).
diff --git a/grafast/dataplan-pg/src/codecs.ts b/grafast/dataplan-pg/src/codecs.ts
index 26eb80ebe8..8cd4e495b8 100644
--- a/grafast/dataplan-pg/src/codecs.ts
+++ b/grafast/dataplan-pg/src/codecs.ts
@@ -961,8 +961,7 @@ export function rangeOfCodec<
       : null),
     fromPg: needsCast
       ? function (value) {
-          const json = JSON.parse(value);
-          const [lowerInc, lower, upper, upperInc, empty] = json;
+          const [lowerInc, lower, upper, upperInc, empty] = JSON.parse(value);
           return empty
             ? { empty: true }
             : {
diff --git a/grafast/dataplan-pg/src/datasource.ts b/grafast/dataplan-pg/src/datasource.ts
index 56709a5f7b..89c0d713aa 100644
--- a/grafast/dataplan-pg/src/datasource.ts
+++ b/grafast/dataplan-pg/src/datasource.ts
@@ -137,11 +137,14 @@ export interface PgResourceParameter<
  */
 export interface PgResourceUnique<
   TAttributes extends PgCodecAttributes = PgCodecAttributes,
+  TUniqueAttributes extends ReadonlyArray<
+    keyof TAttributes & string
+  > = ReadonlyArray<keyof TAttributes & string>,
 > {
   /**
    * The attributes that are unique
    */
-  attributes: ReadonlyArray<keyof TAttributes & string>;
+  attributes: TUniqueAttributes;
   /**
    * If this is true, this represents the "primary key" of the resource.
    */
diff --git a/grafast/dataplan-pg/src/index.ts b/grafast/dataplan-pg/src/index.ts
index 429aee6172..fbf77fc20a 100644
--- a/grafast/dataplan-pg/src/index.ts
+++ b/grafast/dataplan-pg/src/index.ts
@@ -236,6 +236,8 @@ export type {
   PgCodecAttributeVia,
   PgCodecAttributeViaExplicit,
   PgCodecExtensions,
+  PgCodecFromJavaScriptType,
+  PgCodecFromPostgresType,
   PgCodecList,
   PgCodecPolymorphism,
   PgCodecPolymorphismRelational,
@@ -281,6 +283,7 @@ export type {
   PgPath,
   PgPoint,
   PgPolygon,
+  PgRangeValue,
   PgRecordTypeCodecSpec,
   PgRefDefinition,
   PgRefDefinitionExtensions,
@@ -318,11 +321,6 @@ export type {
   TuplePlanMap,
   WithPgClient,
 };
-export type {
-  PgCodecFromJavaScriptType,
-  PgCodecFromPostgresType,
-  PgRangeValue,
-};
 export {
   assertPgClassSingleStep,
   domainOfCodec,
diff --git a/grafast/dataplan-pg/src/interfaces.ts b/grafast/dataplan-pg/src/interfaces.ts
index b0281b5ac5..adc271affb 100644
--- a/grafast/dataplan-pg/src/interfaces.ts
+++ b/grafast/dataplan-pg/src/interfaces.ts
@@ -462,10 +462,7 @@ export type PlanByUniques<
   TAttributes extends PgCodecAttributes,
   TUniqueAttributes extends ReadonlyArray<PgResourceUnique<TAttributes>>,
 > = TAttributes extends PgCodecAttributes
-  ? TuplePlanMap<
-      TAttributes,
-      TUniqueAttributes[number]["attributes"] & string[]
-    >[number]
+  ? TuplePlanMap<TAttributes, TUniqueAttributes[number]["attributes"]>[number]
   : undefined;
 
 export type PgConditionLike = Modifier<any> & {
@@ -652,12 +649,7 @@ export interface PgRegistry<
     PgCodec<string, PgCodecAttributes | undefined, any, any, any, any, any>
   >,
   TResourceOptions extends {
-    [name in string]: PgResourceOptions<
-      name,
-      PgCodec, // TCodecs[keyof TCodecs],
-      ReadonlyArray<PgResourceUnique<PgCodecAttributes>>,
-      readonly PgResourceParameter[] | undefined
-    >;
+    [name in string]: PgResourceOptions<any, any, any, any>;
   } = Record<
     string,
     PgResourceOptions<
@@ -670,18 +662,7 @@ export interface PgRegistry<
   >,
   TRelations extends {
     [codecName in keyof TCodecs]?: {
-      [relationName in string]: PgCodecRelationConfig<
-        // TCodecs[keyof TCodecs] &
-        PgCodec<string, PgCodecAttributes, any, any, undefined, any, undefined>,
-        // TResourceOptions[keyof TResourceOptions] &
-        PgResourceOptions<
-          any,
-          // TCodecs[keyof TCodecs] &
-          PgCodecWithAttributes,
-          any,
-          any
-        >
-      >;
+      [relationName in string]: PgCodecRelationConfig<any, any>;
     };
   } = Record<
     string,
diff --git a/graphile-build/graphile-build-pg/src/index.ts b/graphile-build/graphile-build-pg/src/index.ts
index 4de5d97eb1..7877ecd759 100644
--- a/graphile-build/graphile-build-pg/src/index.ts
+++ b/graphile-build/graphile-build-pg/src/index.ts
@@ -108,8 +108,15 @@ declare global {
       [tagName: string]: null | true | string | (string | true)[];
     }
 
+    /** Augment this interface to provide generated build-time types. */
+    interface GeneratedTypes {}
+
     interface BuildInput {
-      pgRegistry: PgRegistry;
+      pgRegistry: GeneratedTypes extends {
+        pgRegistry: infer TRegistry extends PgRegistry;
+      }
+        ? TRegistry
+        : PgRegistry;
     }
 
     interface SchemaOptions {
diff --git a/graphile-build/graphile-build-pg/src/plugins/PgBasicsPlugin.ts b/graphile-build/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
index 78c318f759..a758e1df84 100644
--- a/graphile-build/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
+++ b/graphile-build/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
@@ -5,7 +5,6 @@ import type {
   PgCodec,
   PgCodecRelation,
   PgCodecWithAttributes,
-  PgExecutor,
   PgRefDefinition,
   PgResource,
   PgResourceUnique,
@@ -142,8 +141,13 @@ declare global {
       /**
        * Shortcut to primary executor; equivalent for most users to `build.input.pgRegistry.pgExecutors.main`.
        * (strictly it's `build.input.pgRegistry.pgExecutors[Object.keys(build.input.pgRegistry.pgExecutors)[0]]`)
+       *
+       * Note: the TypeScript type for this is an approximation, because
+       * TypeScript doesn't have a concept of "first key". For most people
+       * there will be just a single executor anyway, and the type of the
+       * executor doesn't tend to matter much.
        */
-      pgExecutor: PgExecutor;
+      pgExecutor: GraphileBuild.Build["input"]["pgRegistry"]["pgExecutors"][keyof GraphileBuild.Build["input"]["pgRegistry"]["pgExecutors"]];
       /** Shortcut to the resources in the registry */
       pgResources: GraphileBuild.Build["input"]["pgRegistry"]["pgResources"];
       /** Shortcut to the codecs in the registry */