diff --git a/CMakeLists.txt b/CMakeLists.txt
index 88eb67a5..f28811dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,6 +36,11 @@ project(
 # set this to "${PROJECT_VERSION}" on release
 #set(INSTALL_VERSION "${PROJECT_VERSION}")
 set(INSTALL_VERSION "unreleased")
+if(INSTALL_VERSION STREQUAL "unreleased")
+  set(INSTALL_OUTPUT_VERSION "${PROJECT_VERSION}dev")
+else()
+  set(INSTALL_OUTPUT_VERSION "${INSTALL_VERSION}")
+endif()
 set(H3_CORE_VERSION 4.5.0)
 set(H3_CORE_SHA256 0da8a392a6ff77e76b60e6a331a49497d0935b6b7b6899da7a3e2786139b0441)
 
diff --git a/cmake/AddPostgreSQLExtension.cmake b/cmake/AddPostgreSQLExtension.cmake
index e195a630..eedc852e 100644
--- a/cmake/AddPostgreSQLExtension.cmake
+++ b/cmake/AddPostgreSQLExtension.cmake
@@ -167,6 +167,21 @@ function(PostgreSQL_add_extension_bitcode LIBRARY_NAME EXTENSION_NAME EXTENSION_
   )
 endfunction()
 
+macro(PostgreSQL_append_update_transition SOURCE_VERSION)
+  set(UPDATE_TRANSITION_NAME "${EXTENSION_NAME}--${SOURCE_VERSION}--${EXTENSION_VERSION}.sql")
+  set(UPDATE_TRANSITION_OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${UPDATE_TRANSITION_NAME}")
+  set(UPDATE_TRANSITION_CONTENT [=[
+-- Generated transition from @SOURCE_VERSION@ development installs.
+\echo Use "ALTER EXTENSION @EXTENSION_NAME@ UPDATE TO '@EXTENSION_VERSION@'" to load this file. \quit
+]=])
+  string(REPLACE "@SOURCE_VERSION@" "${SOURCE_VERSION}" UPDATE_TRANSITION_CONTENT "${UPDATE_TRANSITION_CONTENT}")
+  string(REPLACE "@EXTENSION_NAME@" "${EXTENSION_NAME}" UPDATE_TRANSITION_CONTENT "${UPDATE_TRANSITION_CONTENT}")
+  string(REPLACE "@EXTENSION_VERSION@" "${EXTENSION_VERSION}" UPDATE_TRANSITION_CONTENT "${UPDATE_TRANSITION_CONTENT}")
+  file(WRITE "${UPDATE_TRANSITION_OUTPUT}" "${UPDATE_TRANSITION_CONTENT}")
+  list(APPEND UPDATE_TRANSITION_NAMES "${UPDATE_TRANSITION_NAME}")
+  list(APPEND UPDATE_TRANSITION_OUTPUTS "${UPDATE_TRANSITION_OUTPUT}")
+endmacro()
+
 # Helper command to add extensions
 function(PostgreSQL_add_extension LIBRARY_NAME)
   set(options RELOCATABLE)
@@ -271,25 +286,70 @@ function(PostgreSQL_add_extension LIBRARY_NAME)
 
   # Apply the same compatibility preprocessing to update scripts.
   set(EXTENSION_UPDATES_PROCESSED "")
+  set(EXTENSION_UNRELEASED_TRANSITION_EMITTED FALSE)
+  set(EXTENSION_PROJECT_DEV_RELEASE_TRANSITION_EMITTED FALSE)
+  set(EXTENSION_SOURCE_DEV_RELEASE_TRANSITION_EMITTED FALSE)
   foreach(file ${EXTENSION_UPDATES})
     get_filename_component(UPDATE_NAME "${file}" NAME)
-    set(UPDATE_OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${UPDATE_NAME}")
+    set(UPDATE_OUTPUT_NAME "${UPDATE_NAME}")
+    set(UPDATE_TRANSITION_NAMES "")
+    set(UPDATE_TRANSITION_OUTPUTS "")
+    set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS "${file}")
+    file(READ "${file}" UPDATE_CONTENTS)
+    if(UPDATE_OUTPUT_NAME MATCHES "--unreleased\\.sql$" AND NOT EXTENSION_VERSION STREQUAL "unreleased")
+      string(REGEX REPLACE "--unreleased\\.sql$" "--${EXTENSION_VERSION}.sql" UPDATE_OUTPUT_NAME "${UPDATE_OUTPUT_NAME}")
+      string(REPLACE "UPDATE TO 'unreleased'" "UPDATE TO '${EXTENSION_VERSION}'" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
+      string(REPLACE "availability: unreleased" "availability: ${EXTENSION_VERSION}" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
+    endif()
+
+    if(NOT EXTENSION_VERSION STREQUAL "unreleased" AND NOT EXTENSION_UNRELEASED_TRANSITION_EMITTED)
+      if(UPDATE_OUTPUT_NAME MATCHES "--${EXTENSION_VERSION}\\.sql$")
+        # Let old local development installs marked as "unreleased" move to
+        # the generated development version, and later to the real release.
+        set(EXTENSION_UNRELEASED_TRANSITION_EMITTED TRUE)
+        PostgreSQL_append_update_transition("unreleased")
+      endif()
+    endif()
+
+    if(DEFINED PROJECT_VERSION AND EXTENSION_VERSION STREQUAL PROJECT_VERSION
+        AND (NOT EXTENSION_PROJECT_DEV_RELEASE_TRANSITION_EMITTED OR NOT EXTENSION_SOURCE_DEV_RELEASE_TRANSITION_EMITTED))
+      if(UPDATE_OUTPUT_NAME MATCHES "^${EXTENSION_NAME}--(.+)--${EXTENSION_VERSION}\\.sql$")
+        set(UPDATE_SOURCE_VERSION "${CMAKE_MATCH_1}")
+        if(NOT EXTENSION_PROJECT_DEV_RELEASE_TRANSITION_EMITTED)
+          set(EXTENSION_PROJECT_DEV_RELEASE_TRANSITION_EMITTED TRUE)
+          PostgreSQL_append_update_transition("${PROJECT_VERSION}dev")
+        endif()
+        if(NOT UPDATE_SOURCE_VERSION STREQUAL "unreleased")
+          set(UPDATE_SOURCE_DEV_VERSION "${UPDATE_SOURCE_VERSION}dev")
+          if(NOT UPDATE_SOURCE_DEV_VERSION STREQUAL "${PROJECT_VERSION}dev" AND NOT EXTENSION_SOURCE_DEV_RELEASE_TRANSITION_EMITTED)
+            set(EXTENSION_SOURCE_DEV_RELEASE_TRANSITION_EMITTED TRUE)
+            PostgreSQL_append_update_transition("${UPDATE_SOURCE_DEV_VERSION}")
+          endif()
+        endif()
+      endif()
+    endif()
+    set(UPDATE_OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${UPDATE_OUTPUT_NAME}")
     if(PostgreSQL_VERSION_MAJOR VERSION_LESS "16")
-      file(READ "${file}" UPDATE_CONTENTS)
       string(REPLACE "@extschema:${EXTENSION_NAME}@." "" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
       string(REPLACE "@extschema:h3@." "" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
       string(REPLACE "@extschema:postgis@." "" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
       string(REPLACE "@extschema:postgis_raster@." "" UPDATE_CONTENTS "${UPDATE_CONTENTS}")
-      file(WRITE "${UPDATE_OUTPUT}" "${UPDATE_CONTENTS}")
-    else()
-      configure_file("${file}" "${UPDATE_OUTPUT}" COPYONLY)
     endif()
+    file(WRITE "${UPDATE_OUTPUT}" "${UPDATE_CONTENTS}")
     configure_file(
       "${UPDATE_OUTPUT}"
-      "${EXTENSION_BUILD_EXTENSION_DIR}/${UPDATE_NAME}"
+      "${EXTENSION_BUILD_EXTENSION_DIR}/${UPDATE_OUTPUT_NAME}"
       COPYONLY
     )
     list(APPEND EXTENSION_UPDATES_PROCESSED "${UPDATE_OUTPUT}")
+    foreach(UPDATE_TRANSITION_NAME UPDATE_TRANSITION_OUTPUT IN ZIP_LISTS UPDATE_TRANSITION_NAMES UPDATE_TRANSITION_OUTPUTS)
+      configure_file(
+        "${UPDATE_TRANSITION_OUTPUT}"
+        "${EXTENSION_BUILD_EXTENSION_DIR}/${UPDATE_TRANSITION_NAME}"
+        COPYONLY
+      )
+      list(APPEND EXTENSION_UPDATES_PROCESSED "${UPDATE_TRANSITION_OUTPUT}")
+    endforeach()
   endforeach()
 
   # Install everything else into share-dir
diff --git a/docs/development.md b/docs/development.md
index 52ffbf36..12494eb9 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -2,6 +2,13 @@
 
 In order to build and test your changes, simply run `./scripts/develop`.
 
+During development, repository source files keep `INSTALL_VERSION` and the
+latest update SQL filenames at `unreleased`. CMake derives the installed
+PostgreSQL extension version from that placeholder as `${PROJECT_VERSION}dev`,
+so a development build of project version `4.5.0` installs control, SQL, and
+module metadata for `4.5.0dev`. Release scripts still replace the source
+placeholder with the exact release version.
+
 For local upgrade-validation coverage, install `pg_validate_extupgrade` so
 `ctest` can run the same extension-upgrade checks as CI. Without it, CTest
 registers explicit `*_validate_extupgrade_unavailable` placeholder tests and
@@ -30,8 +37,9 @@ This command also validates that all extension GUCs are documented in `h3/src/gu
    - The script creates `release-X.Y.Z` and leaves the release changes
      uncommitted for review.
 2. Review the release diff
-   - Root `CMakeLists.txt` has `VERSION X.Y.Z` and installs
-     `${PROJECT_VERSION}` instead of `unreleased`.
+   - Root `CMakeLists.txt` has `VERSION X.Y.Z`, sets `INSTALL_VERSION` to
+     `${PROJECT_VERSION}`, and therefore installs exactly `X.Y.Z` instead of
+     the generated development version.
    - The `h3` and `h3_postgis` update files that ended in `--unreleased.sql`
      have been renamed to end in `--X.Y.Z.sql`, and their CMake references were
      renamed with them.
@@ -60,6 +68,6 @@ This command also validates that all extension GUCs are documented in `h3/src/gu
    - Run `scripts/postrelease`. The script restores `INSTALL_VERSION` to
      `unreleased`, creates the next empty `h3--X.Y.Z--unreleased.sql` and
      `h3_postgis--X.Y.Z--unreleased.sql` files, adds them to the extension CMake
-     files, restores the upgrade regression target to `unreleased`, and runs the
-     release metadata checks.
+     files, keeps the upgrade regression target pointed at the default
+     extension version, and runs the release metadata checks.
    - Review, commit, push, and merge the post-release development branch.
diff --git a/h3/CMakeLists.txt b/h3/CMakeLists.txt
index 4a325cdd..e0088bb9 100644
--- a/h3/CMakeLists.txt
+++ b/h3/CMakeLists.txt
@@ -2,7 +2,7 @@ PostgreSQL_add_extension(postgresql_h3
   RELOCATABLE
   NAME h3
   COMMENT "H3 bindings for PostgreSQL"
-  VERSION ${INSTALL_VERSION}
+  VERSION ${INSTALL_OUTPUT_VERSION}
   COMPONENT ${PROJECT_NAME}
   SOURCES
     src/binding/edge.c
diff --git a/h3/src/config.h.in b/h3/src/config.h.in
index 8a880437..9669e60f 100644
--- a/h3/src/config.h.in
+++ b/h3/src/config.h.in
@@ -17,6 +17,6 @@
 #ifndef H3_CONFIG_H
 #define H3_CONFIG_H
 
-#define POSTGRESQL_H3_VERSION "@INSTALL_VERSION@"
+#define POSTGRESQL_H3_VERSION "@INSTALL_OUTPUT_VERSION@"
 
 #endif /* H3_CONFIG_H */
diff --git a/h3/test/CMakeLists.txt b/h3/test/CMakeLists.txt
index 276bc665..c5949314 100644
--- a/h3/test/CMakeLists.txt
+++ b/h3/test/CMakeLists.txt
@@ -73,7 +73,7 @@ PostgreSQL_add_extupgrade_test(
   NAME h3_validate_extupgrade
   EXTNAME h3
   FROM_VERSION 0.1.0
-  TO_VERSION ${INSTALL_VERSION}
+  TO_VERSION ${INSTALL_OUTPUT_VERSION}
   TEMP_ROOT ${CMAKE_CURRENT_BINARY_DIR}/extupgrade-h3
   TEMP_PORT 65441
   DYNAMIC_LIBRARY_PATH ${H3_REGRESS_TEMP_CONFIG_DYNAMIC_LIBRARY_PATH}
diff --git a/h3/test/expected/extension.out b/h3/test/expected/extension.out
index d7fb76a3..20aea75c 100644
--- a/h3/test/expected/extension.out
+++ b/h3/test/expected/extension.out
@@ -2,7 +2,7 @@
 --
 -- TEST h3_get_extension_version
 --
-SELECT h3_get_extension_version() ~ '^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$'
+SELECT h3_get_extension_version() ~ '^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:dev|-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$'
     OR h3_get_extension_version() = 'unreleased';
  t
 
@@ -97,7 +97,7 @@ SELECT
     hex,
     h3_distance_user_wrapper(hex) AS dist
 FROM h3_distance_expr_fail_userfn;
-ALTER EXTENSION h3 UPDATE TO 'unreleased';
+ALTER EXTENSION h3 UPDATE;
 SELECT (current_setting('server_version_num')::int >= 140000) = EXISTS (
     SELECT 1
     FROM pg_amproc ap
diff --git a/h3/test/sql/extension.sql b/h3/test/sql/extension.sql
index e8266ea4..e1767f4b 100644
--- a/h3/test/sql/extension.sql
+++ b/h3/test/sql/extension.sql
@@ -4,7 +4,7 @@
 -- TEST h3_get_extension_version
 --
 
-SELECT h3_get_extension_version() ~ '^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$'
+SELECT h3_get_extension_version() ~ '^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:dev|-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$'
     OR h3_get_extension_version() = 'unreleased';
 
 --
@@ -114,7 +114,7 @@ SELECT
     h3_distance_user_wrapper(hex) AS dist
 FROM h3_distance_expr_fail_userfn;
 
-ALTER EXTENSION h3 UPDATE TO 'unreleased';
+ALTER EXTENSION h3 UPDATE;
 
 SELECT (current_setting('server_version_num')::int >= 140000) = EXISTS (
     SELECT 1
diff --git a/h3_postgis/CMakeLists.txt b/h3_postgis/CMakeLists.txt
index 855ec635..695f6afb 100644
--- a/h3_postgis/CMakeLists.txt
+++ b/h3_postgis/CMakeLists.txt
@@ -2,7 +2,7 @@ PostgreSQL_add_extension(postgresql_h3_postgis
   RELOCATABLE
   NAME h3_postgis
   COMMENT "H3 PostGIS integration"
-  VERSION ${INSTALL_VERSION}
+  VERSION ${INSTALL_OUTPUT_VERSION}
   COMPONENT ${PROJECT_NAME}
   REQUIRES
     h3
diff --git a/h3_postgis/src/config.h.in b/h3_postgis/src/config.h.in
index fb4bb002..9ab16de0 100644
--- a/h3_postgis/src/config.h.in
+++ b/h3_postgis/src/config.h.in
@@ -17,6 +17,6 @@
 #ifndef PGH3_CONFIG_H
 #define PGH3_CONFIG_H
 
-#define POSTGRESQL_PGH3_VERSION "@INSTALL_VERSION@"
+#define POSTGRESQL_PGH3_VERSION "@INSTALL_OUTPUT_VERSION@"
 
 #endif /* PGH3_CONFIG_H */
diff --git a/h3_postgis/test/CMakeLists.txt b/h3_postgis/test/CMakeLists.txt
index 1c7c473d..d87b8f38 100644
--- a/h3_postgis/test/CMakeLists.txt
+++ b/h3_postgis/test/CMakeLists.txt
@@ -90,7 +90,7 @@ PostgreSQL_add_extupgrade_test(
   NAME h3_postgis_validate_extupgrade
   EXTNAME h3_postgis
   FROM_VERSION 4.0.0
-  TO_VERSION ${INSTALL_VERSION}
+  TO_VERSION ${INSTALL_OUTPUT_VERSION}
   TEMP_ROOT ${CMAKE_CURRENT_BINARY_DIR}/extupgrade-h3_postgis
   TEMP_PORT 65442
   DYNAMIC_LIBRARY_PATH ${H3_POSTGIS_REGRESS_TEMP_CONFIG_DYNAMIC_LIBRARY_PATH}
diff --git a/scripts/postrelease b/scripts/postrelease
index 1cd4a8ff..f6d0014d 100755
--- a/scripts/postrelease
+++ b/scripts/postrelease
@@ -87,11 +87,9 @@ main() {
 
   make_next_update h3 h3/sql/updates h3/CMakeLists.txt "$version"
   make_next_update h3_postgis h3_postgis/sql/updates h3_postgis/CMakeLists.txt "$version"
-  sed -i "s/ALTER EXTENSION h3 UPDATE TO '${version}'/ALTER EXTENSION h3 UPDATE TO 'unreleased'/g" \
-    h3/test/sql/extension.sql h3/test/expected/extension.out
   for test_file in h3/test/sql/extension.sql h3/test/expected/extension.out; do
-    grep -q "ALTER EXTENSION h3 UPDATE TO 'unreleased'" "$test_file" ||
-      die "${test_file} extension regression target was not restored to unreleased"
+    grep -q "ALTER EXTENSION h3 UPDATE;" "$test_file" ||
+      die "${test_file} extension regression target does not update to the default version"
   done
 
   verify_update_references
diff --git a/scripts/release b/scripts/release
index 62271b05..e1dcb77f 100755
--- a/scripts/release
+++ b/scripts/release
@@ -72,7 +72,8 @@ release_update_file() {
   [[ ! -e "$new_file" ]] || die "${new_file} already exists"
 
   git mv "$old_file" "$new_file"
-  sed -i "s/unreleased/${version}/g" "$new_file"
+  sed -i "s/UPDATE TO 'unreleased'/UPDATE TO '${version}'/g" "$new_file"
+  sed -i "s/availability: unreleased/availability: ${version}/g" "$new_file"
   sed -i -E 's/[[:space:]]+$//' "$new_file"
   grep -qF "$old_name" "$cmake_file" || die "${cmake_file} does not reference ${old_name}"
   OLD_NAME="$old_name" NEW_NAME="$new_name" \
@@ -211,9 +212,6 @@ main() {
   release_update_file h3 h3/sql/updates h3/CMakeLists.txt "$version"
   release_update_file h3_postgis h3_postgis/sql/updates h3_postgis/CMakeLists.txt "$version"
 
-  sed -i "s/ALTER EXTENSION h3 UPDATE TO 'unreleased'/ALTER EXTENSION h3 UPDATE TO '${version}'/g" \
-    h3/test/sql/extension.sql h3/test/expected/extension.out
-
   sed -i -E "s/^version: v[0-9]+\.[0-9]+\.[0-9]+/version: v${version}/" CITATION.cff
   sed -i -E "s/^date-released: [0-9]{4}-[0-9]{2}-[0-9]{2}/date-released: ${release_date}/" CITATION.cff