diff --git a/.claude/settings.json b/.claude/settings.json
deleted file mode 100644
index cd5372a..0000000
--- a/.claude/settings.json
+++ /dev/null
@@ -1,19 +0,0 @@
-{
-  "attribution": {
-    "commit": "",
-    "pr": ""
-  },
-  "hooks": {
-    "PostToolUse": [
-      {
-        "matcher": "Write|Edit",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "jq -r '.tool_response.filePath // .tool_input.file_path' | { read -r f; case \"$f\" in *.rb) bin/stree write \"$f\" ;; esac; } 2>/dev/null || true"
-          }
-        ]
-      }
-    ]
-  }
-}
diff --git a/.envrc b/.envrc
deleted file mode 100644
index b50a72f..0000000
--- a/.envrc
+++ /dev/null
@@ -1 +0,0 @@
-export MUTANT_SINCE=HEAD
diff --git a/.githooks/pre-commit b/.githooks/pre-commit
deleted file mode 100755
index 3a43294..0000000
--- a/.githooks/pre-commit
+++ /dev/null
@@ -1,17 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-stash_ref=""
-cleanup() {
-  if [ -n "$stash_ref" ]; then
-    git stash pop --quiet "$stash_ref" || true
-  fi
-}
-trap cleanup EXIT
-
-if ! git diff --quiet || [ -n "$(git ls-files --others --exclude-standard)" ]; then
-  git stash push --keep-index --include-untracked --quiet --message "pre-commit: $(date +%s)"
-  stash_ref="stash@{0}"
-fi
-
-bin/rake
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ae00924..f629ca3 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -15,17 +15,29 @@ jobs:
     runs-on: ubuntu-latest
 
     env:
-      MUTANT_SINCE: ${{ github.event.pull_request.base.sha || 'HEAD^' }}
+      MUTANT_SINCE: ${{ github.event.pull_request.base.sha || github.event.before }}
 
     steps:
       - uses: actions/checkout@v6
         with:
           persist-credentials: false
           fetch-depth: 0
-      - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
         with:
-          ruby-version: '4.0.2'
-          bundler-cache: true
-      - name: Run the default task
-        run: bin/rake
+          extra_nix_config: |
+            accept-flake-config = true
+      - name: Set up cachix
+        uses: cachix/cachix-action@v16
+        with:
+          name: devenv
+      - name: Install devenv
+        run: nix profile install nixpkgs#devenv
+      - name: Cache gems
+        uses: actions/cache@v4
+        with:
+          path: .devenv/state/.bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('Gemfile.lock') }}
+          restore-keys: ${{ runner.os }}-gems-
+      - name: Run the tests
+        run: devenv tasks run test
diff --git a/.gitignore b/.gitignore
index eeca105..ca4d092 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,12 @@
+/.claude/settings.json
+/.mcp.json
 /.bundle/
 /.mutant/
 /pkg/
 /tmp/
 /test/pg_regress/results/
+.devenv*
+devenv.local.nix
+devenv.local.yaml
+.pre-commit-config.yaml
+/.githooks/
diff --git a/AGENTS.md b/AGENTS.md
index 6495684..4cc278e 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -1,5 +1,5 @@
 # Agent rules
 
 - Prefer inlining variables when they are not reused.
-- After editing files, run `bin/rake format`.
+- After editing files, run `treefmt`.
 - When adding and building a feature, follow the TDD process.
diff --git a/Gemfile.lock b/Gemfile.lock
index 9c1ddd0..abbd85f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -313,7 +313,6 @@ CHECKSUMS
   benchmark (0.5.0) sha256=465df122341aedcb81a2a24b4d3bd19b6c67c1530713fd533f3ff034e419236c
   bigdecimal (4.1.2) sha256=53d217666027eab4280346fba98e7d5b66baaae1b9c3c1c0ffe89d48188a3fbd
   builder (3.3.0) sha256=497918d2f9dca528fdca4b88d84e4ef4387256d984b8154e9d5d3fe5a9c8835f
-  bundler (4.0.11) sha256=5bcec0fb78302e48d02ee46f10ee6e6942be647ba5b44a6d1ddfda9a240ce785
   concurrent-ruby (1.3.6) sha256=6b56837e1e7e5292f9864f34b69c5a2cbc75c0cf5338f1ce9903d10fa762d5ab
   connection_pool (3.0.2) sha256=33fff5ba71a12d2aa26cb72b1db8bba2a1a01823559fb01d29eb74c286e62e0a
   crass (1.0.6) sha256=dc516022a56e7b3b156099abc81b6d2b08ea1ed12676ac7a5657617f012bd45d
@@ -396,4 +395,4 @@ CHECKSUMS
   zeitwerk (2.8.2) sha256=7212a61311083c604184b1ea2574b9aa05cd14f855a0841c06985cabe9181d12
 
 BUNDLED WITH
-  4.0.11
+   2.7.2
diff --git a/Rakefile b/Rakefile
index 153bf89..6a897fa 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,79 +1,4 @@
 # frozen_string_literal: true
 
 require "bundler/gem_tasks"
-require "fileutils"
-require "minitest/test_task"
-require "uri"
 require_relative "lib/en57/tasks"
-
-Minitest::TestTask.create
-
-def pg_regress_bin
-  candidates = [
-    ENV["PG_REGRESS"],
-    `command -v pg_regress`.strip,
-    "/opt/homebrew/lib/postgresql@18/pgxs/src/test/regress/pg_regress",
-  ]
-
-  candidates.find do |candidate|
-    candidate && !candidate.empty? && File.executable?(candidate)
-  end
-end
-
-task :format do
-  system("stree write **/*.rb")
-  system("pg_format -i db/**/*.sql")
-end
-
-task :mutate do
-  system("bin/mutant run")
-end
-
-task :mutate_since do
-  system("bin/mutant run --since #{ENV.fetch("MUTANT_SINCE")}")
-end
-
-desc "Run pg_regress tests against a pg-ephemeral instance"
-task :pg_regress do
-  require "pg_ephemeral"
-
-  pg_regress = pg_regress_bin
-  unless pg_regress
-    abort("pg_regress not found. Set PG_REGRESS=/path/to/pg_regress")
-  end
-
-  server = PgEphemeral.start
-  uri = URI(server.url)
-
-  host = uri.host
-  port = uri.port
-  user = uri.user
-  dbname = uri.path.delete_prefix("/")
-  bindir = ENV["PG_BINDIR"] || `pg_config --bindir`.strip
-  schedule = ENV["PG_REGRESS_SCHEDULE"] || "test/pg_regress/schedule_existing"
-
-  FileUtils.rm_rf("test/pg_regress/results")
-  FileUtils.mkdir_p("test/pg_regress/results")
-
-  success =
-    system(
-      { "PGPASSWORD" => uri.password },
-      pg_regress,
-      "--use-existing",
-      "--host=#{host}",
-      "--port=#{port}",
-      "--user=#{user}",
-      "--dbname=#{dbname}",
-      "--inputdir=test/pg_regress",
-      "--outputdir=test/pg_regress/results",
-      "--expecteddir=test/pg_regress",
-      "--bindir=#{bindir}",
-      "--schedule=#{schedule}",
-    )
-
-  abort("pg_regress failed") unless success
-ensure
-  server&.shutdown
-end
-
-task default: %i[test mutate_since]
diff --git a/bin/setup b/bin/setup
deleted file mode 100755
index dce67d8..0000000
--- a/bin/setup
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-IFS=$'\n\t'
-set -vx
-
-bundle install
-
-# Do any other automated setup that you need to do here
diff --git a/db/schema/0.1.0.sql b/db/schema/0.1.0.sql
index 4e2ad57..1f947a0 100644
--- a/db/schema/0.1.0.sql
+++ b/db/schema/0.1.0.sql
@@ -23,7 +23,7 @@ CREATE TYPE en57.event AS (
     type text,
     data jsonb,
     meta jsonb,
-    tags text[]
+    tags text []
 );
 
 CREATE TYPE en57.append_result AS (
@@ -31,11 +31,13 @@ CREATE TYPE en57.append_result AS (
     conflicting_events jsonb
 );
 
-CREATE FUNCTION en57.append_events (new_events en57.event[], append_condition jsonb DEFAULT '{}'::jsonb)
-    RETURNS en57.append_result
-    LANGUAGE plpgsql
-    SET enable_seqscan = OFF
-    AS $$
+CREATE FUNCTION en57.append_events(
+    new_events en57.event [], append_condition jsonb DEFAULT '{}'::jsonb
+)
+RETURNS en57.append_result
+LANGUAGE plpgsql
+SET enable_seqscan = OFF
+AS $$
 DECLARE
     criteria jsonb[] := ARRAY (
         SELECT
@@ -150,16 +152,21 @@ INSERT INTO en57.events (id, type, data, meta)
 END;
 $$;
 
-CREATE FUNCTION en57.read_events (criteria jsonb[], batch_size int DEFAULT NULL, after_position bigint DEFAULT NULL)
-    RETURNS TABLE (
-        "position" bigint,
-        id uuid,
-        type text,
-        data jsonb,
-        meta jsonb,
-        tags text[])
-    LANGUAGE SQL
-    AS $$
+CREATE FUNCTION en57.read_events(
+    criteria jsonb [],
+    batch_size int DEFAULT NULL,
+    after_position bigint DEFAULT NULL
+)
+RETURNS TABLE (
+    "position" bigint,
+    id uuid,
+    type text,
+    data jsonb,
+    meta jsonb,
+    tags text []
+)
+LANGUAGE sql
+AS $$
     WITH parsed_criteria AS (
         SELECT
             c,
@@ -226,4 +233,3 @@ ORDER BY
     e.position
 LIMIT batch_size;
 $$;
-
diff --git a/db/seeds/concurrent_append_non_conflicting_tags_seeded.sql b/db/seeds/concurrent_append_non_conflicting_tags_seeded.sql
index da205ff..bc73bbc 100644
--- a/db/seeds/concurrent_append_non_conflicting_tags_seeded.sql
+++ b/db/seeds/concurrent_append_non_conflicting_tags_seeded.sql
@@ -4,7 +4,7 @@
 -- of the same shape the benchmark queries.
 INSERT INTO en57.events (id, type)
 SELECT
-    gen_random_uuid (),
+    gen_random_uuid(),
     'event_benchmarked'
 FROM
     generate_series(1, 1000000);
@@ -15,4 +15,3 @@ SELECT
     'writer:' || substr(md5(random()::text), 1, 8)
 FROM
     en57.events;
-
diff --git a/db/seeds/res.sql b/db/seeds/res.sql
index 6902cb6..5ac9466 100644
--- a/db/seeds/res.sql
+++ b/db/seeds/res.sql
@@ -10,184 +10,206 @@ SET client_encoding = 'UTF8';
 
 SET standard_conforming_strings = ON;
 
-SELECT
-    pg_catalog.set_config('search_path', '', FALSE);
+SELECT pg_catalog.set_config('search_path', '', FALSE);
 
 SET check_function_bodies = FALSE;
 
-SET xmloption = content;
+SET xmloption = CONTENT;
 
-SET client_min_messages = warning;
+SET client_min_messages = WARNING;
 
 SET row_security = OFF;
 
 SET default_tablespace = '';
 
-SET default_table_access_method = heap;
+SET default_table_access_method = HEAP;
 
 --
 -- Name: ar_internal_metadata; Type: TABLE; Schema: public; Owner: -
 --
-CREATE TABLE public.ar_internal_metadata (
-    key character varying NOT NULL,
-    value character varying,
-    created_at timestamp(6) without time zone NOT NULL,
-    updated_at timestamp(6) without time zone NOT NULL
+CREATE TABLE PUBLIC.AR_INTERNAL_METADATA (
+    KEY character varying NOT NULL,
+    VALUE character varying,
+    CREATED_AT timestamp(6) without time zone NOT NULL,
+    UPDATED_AT timestamp(6) without time zone NOT NULL
 );
 
 --
 -- Name: event_store_events; Type: TABLE; Schema: public; Owner: -
 --
-CREATE TABLE public.event_store_events (
-    id bigint NOT NULL,
-    event_id uuid NOT NULL,
-    event_type character varying NOT NULL,
-    metadata jsonb,
-    data jsonb NOT NULL,
-    created_at timestamp(6) without time zone NOT NULL,
-    valid_at timestamp(6) without time zone
+CREATE TABLE PUBLIC.EVENT_STORE_EVENTS (
+    ID bigint NOT NULL,
+    EVENT_ID uuid NOT NULL,
+    EVENT_TYPE character varying NOT NULL,
+    METADATA jsonb,
+    DATA jsonb NOT NULL,
+    CREATED_AT timestamp(6) without time zone NOT NULL,
+    VALID_AT timestamp(6) without time zone
 );
 
 --
 -- Name: event_store_events_id_seq; Type: SEQUENCE; Schema: public; Owner: -
 --
-CREATE SEQUENCE public.event_store_events_id_seq
-    START WITH 1
-    INCREMENT BY 1
-    NO MINVALUE
-    NO MAXVALUE
-    CACHE 1;
+CREATE SEQUENCE PUBLIC.EVENT_STORE_EVENTS_ID_SEQ
+START WITH 1
+INCREMENT BY 1
+NO MINVALUE
+NO MAXVALUE
+CACHE 1;
 
 --
 -- Name: event_store_events_id_seq; Type: SEQUENCE OWNED BY; Schema: public; Owner: -
 --
-ALTER SEQUENCE public.event_store_events_id_seq OWNED BY public.event_store_events.id;
+ALTER SEQUENCE PUBLIC.EVENT_STORE_EVENTS_ID_SEQ OWNED BY PUBLIC.EVENT_STORE_EVENTS.ID;
 
 --
 -- Name: event_store_events_in_streams; Type: TABLE; Schema: public; Owner: -
 --
-CREATE TABLE public.event_store_events_in_streams (
-    id bigint NOT NULL,
-    stream character varying NOT NULL,
+CREATE TABLE PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS (
+    ID bigint NOT NULL,
+    STREAM character varying NOT NULL,
     "position" integer,
-    event_id uuid NOT NULL,
-    created_at timestamp(6) without time zone NOT NULL
+    EVENT_ID uuid NOT NULL,
+    CREATED_AT timestamp(6) without time zone NOT NULL
 );
 
 --
 -- Name: event_store_events_in_streams_id_seq; Type: SEQUENCE; Schema: public; Owner: -
 --
-CREATE SEQUENCE public.event_store_events_in_streams_id_seq
-    START WITH 1
-    INCREMENT BY 1
-    NO MINVALUE
-    NO MAXVALUE
-    CACHE 1;
+CREATE SEQUENCE PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS_ID_SEQ
+START WITH 1
+INCREMENT BY 1
+NO MINVALUE
+NO MAXVALUE
+CACHE 1;
 
 --
 -- Name: event_store_events_in_streams_id_seq; Type: SEQUENCE OWNED BY; Schema: public; Owner: -
 --
-ALTER SEQUENCE public.event_store_events_in_streams_id_seq OWNED BY public.event_store_events_in_streams.id;
+ALTER SEQUENCE PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS_ID_SEQ OWNED BY PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS.ID;
 
 --
 -- Name: schema_migrations; Type: TABLE; Schema: public; Owner: -
 --
-CREATE TABLE public.schema_migrations (
-    version character varying NOT NULL
+CREATE TABLE PUBLIC.SCHEMA_MIGRATIONS (
+    VERSION character varying NOT NULL
 );
 
 --
 -- Name: event_store_events id; Type: DEFAULT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.event_store_events
-    ALTER COLUMN id SET DEFAULT nextval('public.event_store_events_id_seq'::regclass);
+ALTER TABLE ONLY PUBLIC.EVENT_STORE_EVENTS
+ALTER COLUMN ID SET DEFAULT nextval(
+    'public.event_store_events_id_seq'::regclass
+);
 
 --
 -- Name: event_store_events_in_streams id; Type: DEFAULT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.event_store_events_in_streams
-    ALTER COLUMN id SET DEFAULT nextval('public.event_store_events_in_streams_id_seq'::regclass);
+ALTER TABLE ONLY PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS
+ALTER COLUMN ID SET DEFAULT nextval(
+    'public.event_store_events_in_streams_id_seq'::regclass
+);
 
 --
 -- Name: ar_internal_metadata ar_internal_metadata_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.ar_internal_metadata
-    ADD CONSTRAINT ar_internal_metadata_pkey PRIMARY KEY (key);
+ALTER TABLE ONLY PUBLIC.AR_INTERNAL_METADATA
+ADD CONSTRAINT AR_INTERNAL_METADATA_PKEY PRIMARY KEY (KEY);
 
 --
 -- Name: event_store_events_in_streams event_store_events_in_streams_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.event_store_events_in_streams
-    ADD CONSTRAINT event_store_events_in_streams_pkey PRIMARY KEY (id);
+ALTER TABLE ONLY PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS
+ADD CONSTRAINT EVENT_STORE_EVENTS_IN_STREAMS_PKEY PRIMARY KEY (ID);
 
 --
 -- Name: event_store_events event_store_events_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.event_store_events
-    ADD CONSTRAINT event_store_events_pkey PRIMARY KEY (id);
+ALTER TABLE ONLY PUBLIC.EVENT_STORE_EVENTS
+ADD CONSTRAINT EVENT_STORE_EVENTS_PKEY PRIMARY KEY (ID);
 
 --
 -- Name: schema_migrations schema_migrations_pkey; Type: CONSTRAINT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.schema_migrations
-    ADD CONSTRAINT schema_migrations_pkey PRIMARY KEY (version);
+ALTER TABLE ONLY PUBLIC.SCHEMA_MIGRATIONS
+ADD CONSTRAINT SCHEMA_MIGRATIONS_PKEY PRIMARY KEY (VERSION);
 
 --
 -- Name: index_event_store_events_in_streams_on_created_at; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_in_streams_on_created_at ON public.event_store_events_in_streams USING btree (created_at);
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_IN_STREAMS_ON_CREATED_AT ON PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS USING BTREE (
+    CREATED_AT
+);
 
 --
 -- Name: index_event_store_events_in_streams_on_event_id; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_in_streams_on_event_id ON public.event_store_events_in_streams USING btree (event_id);
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_IN_STREAMS_ON_EVENT_ID ON PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS USING BTREE (
+    EVENT_ID
+);
 
 --
 -- Name: index_event_store_events_in_streams_on_stream_and_event_id; Type: INDEX; Schema: public; Owner: -
 --
-CREATE UNIQUE INDEX index_event_store_events_in_streams_on_stream_and_event_id ON public.event_store_events_in_streams USING btree (stream, event_id);
+CREATE UNIQUE INDEX INDEX_EVENT_STORE_EVENTS_IN_STREAMS_ON_STREAM_AND_EVENT_ID ON PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS USING BTREE (
+    STREAM, EVENT_ID
+);
 
 --
 -- Name: index_event_store_events_in_streams_on_stream_and_position; Type: INDEX; Schema: public; Owner: -
 --
-CREATE UNIQUE INDEX index_event_store_events_in_streams_on_stream_and_position ON public.event_store_events_in_streams USING btree (stream, "position");
+CREATE UNIQUE INDEX INDEX_EVENT_STORE_EVENTS_IN_STREAMS_ON_STREAM_AND_POSITION ON PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS USING BTREE (
+    STREAM, "position"
+);
 
 --
 -- Name: index_event_store_events_on_as_of; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_on_as_of ON public.event_store_events USING btree (COALESCE(valid_at, created_at));
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_ON_AS_OF ON PUBLIC.EVENT_STORE_EVENTS USING BTREE (
+    coalesce(VALID_AT, CREATED_AT)
+);
 
 --
 -- Name: index_event_store_events_on_created_at; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_on_created_at ON public.event_store_events USING btree (created_at);
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_ON_CREATED_AT ON PUBLIC.EVENT_STORE_EVENTS USING BTREE (
+    CREATED_AT
+);
 
 --
 -- Name: index_event_store_events_on_event_id; Type: INDEX; Schema: public; Owner: -
 --
-CREATE UNIQUE INDEX index_event_store_events_on_event_id ON public.event_store_events USING btree (event_id);
+CREATE UNIQUE INDEX INDEX_EVENT_STORE_EVENTS_ON_EVENT_ID ON PUBLIC.EVENT_STORE_EVENTS USING BTREE (
+    EVENT_ID
+);
 
 --
 -- Name: index_event_store_events_on_event_type; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_on_event_type ON public.event_store_events USING btree (event_type);
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_ON_EVENT_TYPE ON PUBLIC.EVENT_STORE_EVENTS USING BTREE (
+    EVENT_TYPE
+);
 
 --
 -- Name: index_event_store_events_on_valid_at; Type: INDEX; Schema: public; Owner: -
 --
-CREATE INDEX index_event_store_events_on_valid_at ON public.event_store_events USING btree (valid_at);
+CREATE INDEX INDEX_EVENT_STORE_EVENTS_ON_VALID_AT ON PUBLIC.EVENT_STORE_EVENTS USING BTREE (
+    VALID_AT
+);
 
 --
 -- Name: event_store_events_in_streams fk_rails_c8d52b5857; Type: FK CONSTRAINT; Schema: public; Owner: -
 --
-ALTER TABLE ONLY public.event_store_events_in_streams
-    ADD CONSTRAINT fk_rails_c8d52b5857 FOREIGN KEY (event_id) REFERENCES public.event_store_events (event_id);
+ALTER TABLE ONLY PUBLIC.EVENT_STORE_EVENTS_IN_STREAMS
+ADD CONSTRAINT FK_RAILS_C8D52B5857 FOREIGN KEY (
+    EVENT_ID
+) REFERENCES PUBLIC.EVENT_STORE_EVENTS (EVENT_ID);
 
 --
 -- PostgreSQL database dump complete
 --
-SET search_path TO "$user", public;
-
-INSERT INTO "schema_migrations" (version)
-    VALUES ('20260521134825');
+SET search_path TO "$user", PUBLIC;
 
+INSERT INTO "schema_migrations" (VERSION)
+VALUES ('20260521134825');
diff --git a/devenv.lock b/devenv.lock
new file mode 100644
index 0000000..66f8095
--- /dev/null
+++ b/devenv.lock
@@ -0,0 +1,218 @@
+{
+  "nodes": {
+    "devenv": {
+      "locked": {
+        "dir": "src/modules",
+        "lastModified": 1782231411,
+        "narHash": "sha256-W/Yhek5L3nc0gaGgMHPrzO6DbLGq7Yb9DKw/kvLwij0=",
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "a4fd3348220d96f7602385adff0ace482e720586",
+        "type": "github"
+      },
+      "original": {
+        "dir": "src/modules",
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1767039857,
+        "narHash": "sha256-vNpUSpF5Nuw8xvDLj2KCwwksIbjua2LZCqhV1LNRDns=",
+        "owner": "NixOS",
+        "repo": "flake-compat",
+        "rev": "5edf11c44bc78a0d334f6334cdaf7d60d732daab",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "flake-compat_2": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1767039857,
+        "narHash": "sha256-vNpUSpF5Nuw8xvDLj2KCwwksIbjua2LZCqhV1LNRDns=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "5edf11c44bc78a0d334f6334cdaf7d60d732daab",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "git-hooks": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1781733627,
+        "narHash": "sha256-U3yTuGBnmXvXoQI3qkpfEDsn9RovQPAjN7ndRco+3u0=",
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "rev": "3bbec39bc90eadfa031e6f3b77272f3f60803e39",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "type": "github"
+      }
+    },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "git-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "narHash": "sha256-HG2cCnktfHsKV0s4XW83gU3F57gaTljL9KNSuG6bnQs=",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "inputs": {
+        "nixpkgs-src": "nixpkgs-src"
+      },
+      "locked": {
+        "lastModified": 1782132010,
+        "narHash": "sha256-ZnAVHdVrotp80iIMm5CSR1fdxPlw7Uwmwxb+O/wsgZ8=",
+        "owner": "cachix",
+        "repo": "devenv-nixpkgs",
+        "rev": "12866ae2dddbc0ab8b329915f8072bb9c75bde89",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "ref": "rolling",
+        "repo": "devenv-nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-ruby": {
+      "inputs": {
+        "flake-compat": "flake-compat_2",
+        "flake-utils": "flake-utils",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1782291298,
+        "narHash": "sha256-s5qd1ZWKoc8m6dnTvcHTMWerE8xXOSG82Vgp7eIPesk=",
+        "owner": "bobvanderlinden",
+        "repo": "nixpkgs-ruby",
+        "rev": "5a59e45e96465645c00422fedf5e62e337f6cfea",
+        "type": "github"
+      },
+      "original": {
+        "owner": "bobvanderlinden",
+        "repo": "nixpkgs-ruby",
+        "type": "github"
+      }
+    },
+    "nixpkgs-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1781607440,
+        "narHash": "sha256-rxO+uc/KFbSJp+pgyXRuAX6QlG9hJdnt0BXpEQRXY+U=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "3e41b24abd260e8f71dbe2f5737d24122f972158",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "git-hooks": "git-hooks",
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-ruby": "nixpkgs-ruby",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1780220602,
+        "narHash": "sha256-eynAfOmbmxJnkp7YewvCEbShNnnYJ9gLLqkzsYtBPeM=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "db947814a175b7ca6ded66e21383d938df01c227",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
\ No newline at end of file
diff --git a/devenv.nix b/devenv.nix
new file mode 100644
index 0000000..c7217c1
--- /dev/null
+++ b/devenv.nix
@@ -0,0 +1,124 @@
+{ pkgs, lib, ... }:
+
+{
+  languages.ruby.enable = true;
+  languages.ruby.version = "4.0.5";
+
+  packages = [
+    pkgs.postgresql_18
+    pkgs.postgresql_18.pg_config
+    pkgs.sqlfluff
+    pkgs.jq
+    pkgs.libyaml
+  ];
+
+  enterShell = ''
+    export MUTANT_SINCE="''${MUTANT_SINCE:-HEAD}"
+  '';
+
+  tasks = {
+    "dev:setup".exec = "bundle install --quiet";
+    "devenv:enterShell".after = [ "dev:setup" ];
+    "dev:format" = {
+      exec = "treefmt";
+      after = [ "dev:setup" ];
+    };
+    "test:unit" = {
+      exec = "bin/m test";
+      after = [ "dev:setup" ];
+    };
+    "test:mutate" = {
+      exec = ''bin/mutant run --since "''${MUTANT_SINCE:-HEAD}"'';
+      after = [ "dev:setup" ];
+    };
+    "test:pg".exec = "pg-regress";
+  };
+
+  treefmt.enable = true;
+  treefmt.config = {
+    programs = {
+      nixfmt.enable = true;
+    };
+    settings.formatter = {
+      ruby = {
+        command = "stree";
+        options = [ "write" ];
+        includes = [ "*.rb" ];
+      };
+      sql = {
+        command = "sqlfluff";
+        options = [
+          "format"
+          "--dialect"
+          "postgres"
+          "--exclude-rules"
+          "LT05"
+        ];
+        includes = [ "db/**/*.sql" ];
+      };
+    };
+  };
+
+  scripts.pg-regress.exec = ''
+    set -euo pipefail
+    cd "$DEVENV_ROOT"
+
+    pg_regress=${pkgs.postgresql_18.dev}/lib/pgxs/src/test/regress/pg_regress
+    bindir=${pkgs.postgresql_18}/bin
+    workdir=$(mktemp -d)
+    datadir=$workdir/data
+    socketdir=$workdir/socket
+    dbname=en57_regress
+    mkdir -p "$socketdir"
+
+    cleanup() {
+      "$bindir/pg_ctl" -D "$datadir" -m immediate stop >/dev/null 2>&1 || true
+      rm -rf "$workdir"
+    }
+    trap cleanup EXIT
+
+    "$bindir/initdb" -D "$datadir" -U postgres --auth=trust >/dev/null
+    "$bindir/pg_ctl" -D "$datadir" -w \
+      -o "-k $socketdir -c listen_addresses='''" start >/dev/null
+    "$bindir/createdb" -h "$socketdir" -U postgres "$dbname"
+    "$bindir/psql" -h "$socketdir" -U postgres -d "$dbname" \
+      -v ON_ERROR_STOP=1 -q -f db/schema/0.1.0.sql
+
+    rm -rf test/pg_regress/results
+    mkdir -p test/pg_regress/results
+
+    "$pg_regress" \
+      --use-existing \
+      --host="$socketdir" \
+      --user=postgres \
+      --dbname="$dbname" \
+      --inputdir=test/pg_regress \
+      --outputdir=test/pg_regress/results \
+      --expecteddir=test/pg_regress \
+      --bindir="$bindir" \
+      --schedule=test/pg_regress/schedule_existing
+  '';
+
+  claude.code.enable = true;
+  claude.code.hooks = {
+    format = {
+      name = "Format edited files with treefmt";
+      hookType = "PostToolUse";
+      matcher = "Write|Edit";
+      command = ''
+        jq -r '.tool_response.filePath // .tool_input.file_path' | { read -r f; treefmt "$f"; } 2>/dev/null || true
+      '';
+    };
+    test = {
+      name = "Run the test namespace on stop";
+      hookType = "Stop";
+      command = ''
+        input=$(cat)
+        cd "''${DEVENV_ROOT:-.}" || exit 0
+        devenv tasks run test 1>&2 && exit 0
+        [ "$(printf '%s' "$input" | jq -r '.stop_hook_active // false')" = "true" ] && exit 0
+        exit 2
+      '';
+    };
+  };
+}
diff --git a/devenv.yaml b/devenv.yaml
new file mode 100644
index 0000000..fa85261
--- /dev/null
+++ b/devenv.yaml
@@ -0,0 +1,18 @@
+inputs:
+  git-hooks:
+    url: github:cachix/git-hooks.nix
+    inputs:
+      nixpkgs:
+        follows: nixpkgs
+  nixpkgs:
+    url: github:cachix/devenv-nixpkgs/rolling
+  nixpkgs-ruby:
+    url: github:bobvanderlinden/nixpkgs-ruby
+    inputs:
+      nixpkgs:
+        follows: nixpkgs
+  treefmt-nix:
+    url: github:numtide/treefmt-nix
+    inputs:
+      nixpkgs:
+        follows: nixpkgs