diff --git a/.github/workflows/service-topology.yml b/.github/workflows/service-topology.yml
new file mode 100644
index 00000000..2b4f15b9
--- /dev/null
+++ b/.github/workflows/service-topology.yml
@@ -0,0 +1,25 @@
+name: Service topology
+on:
+  pull_request:
+    paths:
+      - 'applications/service-topology/**'
+      - '.github/workflows/service-topology.yml'
+  push:
+    paths:
+      - 'applications/service-topology/**'
+      - '.github/workflows/service-topology.yml'
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: applications/service-topology
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: '1.4.2'
+      - run: bun install --frozen-lockfile --ignore-scripts
+      - run: bun run typecheck
+      - run: bun test tests/graph.test.ts
+      - run: bun run build
diff --git a/applications/service-topology/.env.example b/applications/service-topology/.env.example
new file mode 100644
index 00000000..b50d4182
--- /dev/null
+++ b/applications/service-topology/.env.example
@@ -0,0 +1,7 @@
+# Runtime login only. Cloud requires the downloaded CA file.
+DATABASE_URL=postgres://topology_app:YOUR_PASSWORD@YOUR_HOST:5432/postgres
+PG_CA_CERT_PATH=.deployment/postgres-ca.pem
+# Enable only for a loopback development database without TLS:
+# DATABASE_LOCAL=true
+PORT=3000
+APP_ORIGIN=http://127.0.0.1:3000
diff --git a/applications/service-topology/.gitignore b/applications/service-topology/.gitignore
new file mode 100644
index 00000000..1b5df4e8
--- /dev/null
+++ b/applications/service-topology/.gitignore
@@ -0,0 +1,7 @@
+.env
+.deployment/
+.clickhouse/
+node_modules/
+dist/
+test-results/
+playwright-report/
diff --git a/applications/service-topology/README.md b/applications/service-topology/README.md
new file mode 100644
index 00000000..ff9aeb29
--- /dev/null
+++ b/applications/service-topology/README.md
@@ -0,0 +1,302 @@
+# Service atlas
+
+Build and save a small service architecture map with React Flow, Zustand, ELK,
+Elysia, Eden Treaty, and Drizzle's Bun SQL driver, backed by
+[ClickHouse Managed Postgres](https://clickhouse.com/cloud/postgres).
+
+Add services, connect them, drag them into place, or let ELK arrange the graph.
+Every save commits the current document and a revision snapshot together. If two
+tabs edit the same revision, one saves and the other gets a visible conflict.
+
+![A saved storefront service map with six services and directed connections](docs/service-topology.png)
+
+This is a trusted local demo using synthetic architecture metadata. It listens
+on loopback and checks the configured Host and write Origin. There are no user
+accounts, network discovery, automatic service execution, or live collaboration.
+
+## How the pieces fit
+
+| Library           | Actual use                                                             |
+| ----------------- | ---------------------------------------------------------------------- |
+| React Flow        | Draggable service cards, connection handles, edges, zoom and selection |
+| Zustand           | Draft nodes/edges, unsaved state, revision and conflict state          |
+| ELK.js            | Layered automatic layout using the actual graph's nodes and edges      |
+| Elysia            | Typed routes, structural validation and explicit error responses       |
+| Eden Treaty       | Typed reads and saves using a type-only backend import                 |
+| Drizzle + Bun SQL | Conditional updates, JSONB documents and atomic snapshot inserts       |
+
+`service_topology.graphs` stores a header, revision and current JSONB document.
+`service_topology.revisions` has a primary key on `(graph_id, revision)` and
+stores each committed snapshot. The runtime login can read both tables, update
+the current document/revision, and insert snapshots. It cannot update or delete
+snapshots or change the schema.
+
+Maps allow up to 100 services and 200 directed connections. Service names are
+1–60 characters, IDs are UUIDs, coordinates are bounded finite numbers, and
+connections must reference existing services. Self connections and repeated
+connections in the same direction are rejected. Reverse connections are allowed.
+
+[repository.ts](src/server/repository.ts) updates with both ID and base revision
+in its predicate. It inserts the snapshot in the same transaction. A zero-row
+update returns `409`. If insertion fails, the current document also rolls back.
+Reads return the document and revision from one row.
+
+## Get the source and tools
+
+Run application dependencies inside Linux. On macOS, an isolated
+[OrbStack machine](https://docs.orbstack.dev/machines/isolated) keeps dependencies
+off the host:
+
+```sh
+orbctl create ubuntu:noble topology-dev --isolated --arch arm64 --memory 4G --cpus 2
+orbctl run -m topology-dev -w /home/$USER bash
+```
+
+Inside Linux:
+
+```sh
+sudo apt-get update
+sudo apt-get install -y ca-certificates curl git unzip jq openssl postgresql-client docker.io
+sudo systemctl start docker
+sudo usermod -aG docker "$USER"
+# Reopen your Linux shell so the Docker group applies.
+curl -fsSL https://bun.sh/install -o /tmp/bun-install.sh
+bash /tmp/bun-install.sh bun-v1.4.2
+export PATH="$HOME/.bun/bin:$HOME/.local/bin:$PATH"
+curl -fsSL https://clickhouse.com/cli | sh
+git clone https://github.com/ClickHouse/examples.git
+cd examples/applications/service-topology
+bun install --frozen-lockfile --ignore-scripts
+```
+
+The checked-in lockfile pins the library versions. Bun must report `1.4.2`.
+No third-party application service is required. Cloud lifecycle commands may
+instead run with an existing host `clickhousectl`; copy only the database CA and
+step-specific credentials into the VM, keeping Cloud API keys on the host.
+
+## Choose a database
+
+### Local Postgres with clickhousectl
+
+```sh
+umask 077
+mkdir -p .deployment
+clickhousectl local postgres start --name topology --version 18 --json \
+  > .deployment/local-create.json
+export PGHOST=127.0.0.1
+export PGPORT="$(jq -er '.port' .deployment/local-create.json)"
+export PGDATABASE="$(jq -er '.database' .deployment/local-create.json)"
+export PGADMIN="$(jq -er '.user' .deployment/local-create.json)"
+export PGPASSWORD="$(jq -er '.password' .deployment/local-create.json)"
+export PGSSLMODE=disable
+```
+
+Use the actual returned port. This receipt contains a password and belongs in
+the ignored private directory.
+
+### ClickHouse Managed Postgres with clickhousectl
+
+Create an Admin API key following the
+[Cloud API guide](https://clickhouse.com/docs/cloud/manage/openapi), then enter
+it interactively:
+
+```sh
+clickhousectl cloud auth login --interactive
+clickhousectl cloud auth status
+clickhousectl cloud org list
+umask 077
+mkdir -p .deployment
+```
+
+Create `.deployment/resources.env` in an editor with your organization, an
+available AWS region and Postgres size:
+
+```dotenv
+CH_ORG_ID=YOUR_ORGANIZATION_UUID
+CLOUD_REGION=YOUR_AVAILABLE_REGION
+PG_SIZE=YOUR_AVAILABLE_SIZE
+```
+
+One non-HA Postgres 18 service is enough for this example. Review
+[pricing](https://clickhouse.com/pricing) before creating it. Compute, storage,
+backups and network usage can incur charges; stopping the application or VM
+does not stop the managed service's billing.
+
+```sh
+source .deployment/resources.env
+clickhousectl cloud postgres create --org-id "$CH_ORG_ID" \
+  --name service-topology-example --provider aws --region "$CLOUD_REGION" \
+  --size "$PG_SIZE" --pg-version 18 --ha-type none \
+  --tag project=service-topology --json > .deployment/postgres-create.json
+PG_SERVICE_ID="$(jq -er '.id' .deployment/postgres-create.json)"
+```
+
+Save the service ID in `.deployment/resources.env`. Preserve the create receipt:
+its initial password is returned once. If creation is interrupted, inspect
+`clickhousectl cloud postgres list --org-id "$CH_ORG_ID" --json` before retrying.
+
+Repeat inspection until `state` is `running`:
+
+```sh
+clickhousectl cloud postgres get "$PG_SERVICE_ID" --org-id "$CH_ORG_ID" --json \
+  > .deployment/postgres-status.json
+jq '{id,state,hostname,username,postgresVersion,size}' .deployment/postgres-status.json
+clickhousectl cloud postgres certs get "$PG_SERVICE_ID" --org-id "$CH_ORG_ID" \
+  --output .deployment/postgres-ca.pem
+```
+
+Use the service's actual direct hostname, port, database and administrator.
+For a direct service connection, use port 5432 and database `postgres`; check the service response for the actual connection details:
+
+```sh
+export PGHOST="$(jq -er '.hostname' .deployment/postgres-status.json)"
+export PGPORT=5432 PGDATABASE=postgres
+export PGADMIN="$(jq -er '.username' .deployment/postgres-status.json)"
+export PGPASSWORD="$(jq -er '.password' .deployment/postgres-create.json)"
+export PGSSLMODE=verify-full
+export PGSSLROOTCERT="$PWD/.deployment/postgres-ca.pem"
+```
+
+## Apply roles, schema and seed
+
+Run once on your dedicated fresh database. Passwords are read by psql from
+environment variables and do not become command arguments.
+
+```sh
+cat > .deployment/passwords.env <<PASSWORDS
+PG_MIGRATION_PASSWORD=Aa1_$(openssl rand -hex 24)
+PG_APP_PASSWORD=Aa1_$(openssl rand -hex 24)
+PASSWORDS
+source .deployment/passwords.env
+export PG_MIGRATION_PASSWORD PG_APP_PASSWORD
+psql -X -v ON_ERROR_STOP=1 -U "$PGADMIN" -f sql/001_roles.sql
+export PGPASSWORD="$PG_MIGRATION_PASSWORD"
+psql -X -v ON_ERROR_STOP=1 -U topology_migration -f sql/002_schema.sql
+psql -X -v ON_ERROR_STOP=1 -U topology_migration -f sql/003_seed.sql
+unset PGPASSWORD
+```
+
+The migration login is a member of a non-login schema owner. The runtime
+`topology_app` login has narrower grants. The seed creates five services and
+four connections; repeating only the seed preserves existing edits.
+
+## Configure and open the editor
+
+Create the runtime environment while the generated runtime password is available.
+These hex passwords are URL-safe; percent-encode passwords you supply yourself.
+
+```sh
+cat > .env <<RUNTIME
+DATABASE_URL=postgres://topology_app:${PG_APP_PASSWORD}@${PGHOST}:${PGPORT}/${PGDATABASE}
+PG_CA_CERT_PATH=.deployment/postgres-ca.pem
+PORT=3000
+APP_ORIGIN=http://127.0.0.1:3000
+RUNTIME
+unset PG_MIGRATION_PASSWORD PG_APP_PASSWORD
+```
+
+For VM-local Postgres only, add `DATABASE_LOCAL=true` to `.env`. This bypass is
+restricted to loopback database hosts. Managed connections use the downloaded
+CA, certificate/hostname verification, and a bounded five-connection pool.
+Bun 1.4.2 can reject CA rotation bundles with duplicate subjects. On that specific
+signature failure, the connector retries only certificates from the downloaded
+bundle, with certificate and hostname verification still enabled. Restart the app
+after updating the CA bundle.
+Use a plain URL without query parameters; the server configures TLS explicitly.
+
+```sh
+bun run typecheck
+bun run test
+bun run build
+bun start
+```
+
+Open `http://127.0.0.1:3000`. If the app runs in an isolated OrbStack VM, forward
+its loopback port from a host terminal:
+
+```sh
+ssh -N -L 3000:127.0.0.1:3000 topology-dev@orb
+```
+
+1. Add an API service and click it to rename it.
+2. Drag its card, then drag a right handle to another service's left handle.
+3. Click **Auto layout**, then **Save revision**. The committed revision increases.
+4. Refresh; your names, positions and connections remain.
+5. Load two tabs, change both, save the first, then save the second. The second
+   reports a conflict. Its reload button explicitly discards the stale draft.
+6. Remove a service and save. Its incident connections disappear too.
+
+For a Vite development client, set `APP_ORIGIN=http://127.0.0.1:5173` in the
+server environment, run `bun run dev` and `bun run dev:web` in separate terminals,
+and open that origin. Both servers bind to loopback; Vite proxies `/api`.
+
+## Check the meaningful behavior
+
+Secret-free checks:
+
+```sh
+bun run typecheck
+bun run test
+bun run build
+```
+
+Database tests create and remove their own temporary graph rows. Run only against
+a dedicated example database. Put the migration login URL in a private
+`.deployment/test.env` as `DATABASE_TEST_ADMIN_URL`, then:
+
+```sh
+set -a
+source .deployment/test.env
+set +a
+bun run test:integration
+unset DATABASE_TEST_ADMIN_URL
+```
+
+The suite tests 16 concurrent edits, JSONB roundtrip, invalid graphs, rollback
+when snapshot insertion fails, and denied runtime privileges. The intended
+snapshot-failure check logs `Graph save failed.` while the test passes.
+
+With the built server running, install Chromium inside Linux and run the actual
+browser flow:
+
+```sh
+bunx playwright install --with-deps chromium
+bun run test:browser
+```
+
+It exercises dragging, connection creation, layout, save/reload, a second tab's
+conflict and persisted removal. It advances the seeded graph's revision and
+writes a screenshot to `test-results/topology.png`. For a process-restart check,
+save a map, stop Bun with Ctrl-C, run `bun start` again, and compare the graph.
+
+The [custom JSONB type](src/server/schema.ts) is deliberate: Bun 1.4.2 encodes
+objects for JSONB itself. Passing Drizzle's default stringified JSON parameter
+would encode a string twice. The application keeps the graph object intact
+through the Bun SQL integration and verifies the database's JSONB object type.
+
+## Scope and cleanup
+
+Revision snapshots are retained; the UI edits the current map and does not offer
+history browsing or restoration. A lost save response can leave your tab with a
+stale revision; reload to resolve it. Graph metadata is synthetic and the server
+has no per-user authorization. Keep it local.
+
+Stop the app before cleanup. Preserve any source you want to keep.
+
+```sh
+# Local database: stop preserves its data.
+clickhousectl local postgres stop topology
+
+# Managed service: inspect the owned fixture, then permanently delete it.
+source .deployment/resources.env
+clickhousectl cloud postgres get "$PG_SERVICE_ID" --org-id "$CH_ORG_ID" --json
+clickhousectl cloud postgres delete "$PG_SERVICE_ID" --org-id "$CH_ORG_ID"
+clickhousectl cloud postgres list --org-id "$CH_ORG_ID" --json
+# Verify the owned PG_SERVICE_ID is absent from the returned list.
+
+# If you used OrbStack:
+orbctl stop topology-dev
+```
+
+Only delete the service you created for this example. Remove its private
+credential files when they are no longer needed.
diff --git a/applications/service-topology/bun.lock b/applications/service-topology/bun.lock
new file mode 100644
index 00000000..7b7a8d22
--- /dev/null
+++ b/applications/service-topology/bun.lock
@@ -0,0 +1,262 @@
+{
+  "lockfileVersion": 2,
+  "configVersion": 1,
+  "workspaces": {
+    "": {
+      "name": "service-topology",
+      "dependencies": {
+        "@elysiajs/eden": "1.4.9",
+        "@sinclair/typebox": "0.34.52",
+        "@xyflow/react": "12.12.0",
+        "drizzle-orm": "0.45.3",
+        "elkjs": "0.12.0",
+        "elysia": "1.4.30",
+        "react": "19.3.0",
+        "react-dom": "19.3.0",
+        "zustand": "5.0.15",
+      },
+      "devDependencies": {
+        "@playwright/test": "1.63.0",
+        "@types/bun": "1.4.2",
+        "@types/react": "19.3.0",
+        "@types/react-dom": "19.3.0",
+        "@vitejs/plugin-react": "6.1.1",
+        "typescript": "7.0.2",
+        "vite": "8.3.2",
+      },
+    },
+  },
+  "packages": {
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+
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+
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+
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+
+    "memoirist": ["memoirist@0.4.0", "", {}, "sha512-zxTgA0mSYELa66DimuNQDvyLq36AwDlTuVRbnQtB+VuTcKWm5Qc4z3WkSpgsFWHNhexqkIooqpv4hdcqrX5Nmg=="],
+
+    "ms": ["ms@2.1.3", "", {}, "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA=="],
+
+    "nanoid": ["nanoid@3.3.19", "", { "bin": { "nanoid": "bin/nanoid.cjs" } }, "sha512-Y2tUNy4ouw6tq5oDSKeQYGOyhkUBhNOcGV/02KC+6kd9eDGqdZd++mjMiIDilrBYvjEnCYvVtsuHCuP+okSfug=="],
+
+    "openapi-types": ["openapi-types@12.1.3", "", {}, "sha512-N4YtSYJqghVu4iek2ZUvcN/0aqH1kRDuNqzcycDxhOUpg7GdvLa2F3DgS6yBNhInhv2r/6I0Flkn7CqL8+nIcw=="],
+
+    "picocolors": ["picocolors@1.1.1", "", {}, "sha512-xceH2snhtb5M9liqDsmEw56le376mTZkEX/jEb/RxNFyegNul7eNslCXP9FDj/Lcu0X8KEyMceP2ntpaHrDEVA=="],
+
+    "picomatch": ["picomatch@4.0.7", "", {}, "sha512-qcJu88Q2IWqJsDD529JKMdwGm/dvInW4HvQnRwiH9JtihJvzGOscDtHE3x1pBKeUOTysQ8kVmLnJ2kJu7yhcGA=="],
+
+    "playwright": ["playwright@1.63.0", "", { "dependencies": { "playwright-core": "1.63.0" }, "bin": { "playwright": "cli.js" } }, "sha512-+7ziBLidS4NaNCdt57SUDT+wYmmd5fmiQejUic/kb+YsYSCPyOOE9sebzMjNmQrsnNpDJqd4WHvV/8lfKfUDUg=="],
+
+    "playwright-core": ["playwright-core@1.63.0", "", { "bin": { "playwright-core": "cli.js" } }, "sha512-rYCsBF/M5HjUch52bbtVONEFjv6Xu8sm8h72dNlR5bzIE1fvC/bxgspzkjSfU+MweEMmPM8KJebG6nnyxo5mCg=="],
+
+    "postcss": ["postcss@8.5.28", "", { "dependencies": { "nanoid": "^3.3.18", "picocolors": "^1.1.1", "source-map-js": "^1.2.1" } }, "sha512-RRuzqDtt5Y9h3quz5hWhK+TPnsmVs6WwSU6LkJMeY4HstUEDuYTG8UJSdawMRzmzAtV+KEoG8N3Qg2qLy5vM/A=="],
+
+    "react": ["react@19.3.0", "", {}, "sha512-E8LUcbtBWt20bbl2YoHfx4ZDBdxVTfOKtCZn9cDSJ4l6/nuoApcpIBcj47t2wZoVX8g2ZHuMHbiShgCR1T5Sog=="],
+
+    "react-dom": ["react-dom@19.3.0", "", { "dependencies": { "scheduler": "^0.28.0" }, "peerDependencies": { "react": "^19.3.0" } }, "sha512-JDk8dgif51OjFoDE70+OT9ICyYr+69HlmihNwp1+Nsfbna3t5sIiCa9ZJktDmQ4/1b/rn26hIAR2uYXDMr5r0Q=="],
+
+    "rolldown": ["rolldown@1.2.12", "", { "dependencies": { "@oxc-project/types": "=0.152.0", "@rolldown/pluginutils": "^1.0.0" }, "optionalDependencies": { "@rolldown/binding-android-arm-eabi": "1.2.12", "@rolldown/binding-android-arm64": "1.2.12", "@rolldown/binding-darwin-arm64": "1.2.12", "@rolldown/binding-darwin-x64": "1.2.12", "@rolldown/binding-freebsd-x64": "1.2.12", "@rolldown/binding-linux-arm-gnueabihf": "1.2.12", "@rolldown/binding-linux-arm64-gnu": "1.2.12", "@rolldown/binding-linux-arm64-musl": "1.2.12", "@rolldown/binding-linux-ppc64-gnu": "1.2.12", "@rolldown/binding-linux-s390x-gnu": "1.2.12", "@rolldown/binding-linux-x64-gnu": "1.2.12", "@rolldown/binding-linux-x64-musl": "1.2.12", "@rolldown/binding-openharmony-arm64": "1.2.12", "@rolldown/binding-win32-arm64-msvc": "1.2.12", "@rolldown/binding-win32-x64-msvc": "1.2.12" }, "bin": { "rolldown": "./bin/cli.mjs" } }, "sha512-8wafseiaG80xmXSfqidUNqZcylTlhmPZZt+za2m+js2sFZ8dTNlhIOV2WcbIPx2hgwPBJpEUGFAMZ9bgBBLTSQ=="],
+
+    "scheduler": ["scheduler@0.28.0", "", {}, "sha512-juorfCmIkIw8tT+p5BXSm6PJjQF/ycEYmKyzURCIt/RaZIhL+PulbQ9Yu2z1HdOJDdqDTlxA1+xKBmHXJsczAw=="],
+
+    "source-map-js": ["source-map-js@1.2.2", "", {}, "sha512-KGj/8Y43x35aZVDtt+J4mK1hoLGHULMYfSkODJNQjNDC3oW1PqPoxMwo0pLUsWM/UEGzON/NxeHywEfNXNP3Vw=="],
+
+    "strtok3": ["strtok3@10.3.5", "", { "dependencies": { "@tokenizer/token": "^0.3.0" } }, "sha512-ki4hZQfh5rX0QDLLkOCj+h+CVNkqmp/CMf8v8kZpkNVK6jGQooMytqzLZYUVYIZcFZ6yDB70EfD8POcFXiF5oA=="],
+
+    "tinyglobby": ["tinyglobby@0.2.17", "", { "dependencies": { "fdir": "^6.5.0", "picomatch": "^4.0.4" } }, "sha512-wXR/dYpcqKmfWpEdZjiKJOwCNFndD0DMnrW/cYjVGttEkBfVgcLFHoNrlj47mjOVic9yyNu65alsgF4NQyTa2g=="],
+
+    "token-types": ["token-types@6.1.2", "", { "dependencies": { "@borewit/text-codec": "^0.2.1", "@tokenizer/token": "^0.3.0", "ieee754": "^1.2.1" } }, "sha512-dRXchy+C0IgK8WPC6xvCHFRIWYUbqqdEIKPaKo/AcTUNzwLTK6AH7RjdLWsEZcAN/TBdtfUw3PYEgPr5VPr6ww=="],
+
+    "typescript": ["typescript@7.0.2", "", { "optionalDependencies": { "@typescript/typescript-aix-ppc64": "7.0.2", "@typescript/typescript-darwin-arm64": "7.0.2", "@typescript/typescript-darwin-x64": "7.0.2", "@typescript/typescript-freebsd-arm64": "7.0.2", "@typescript/typescript-freebsd-x64": "7.0.2", "@typescript/typescript-linux-arm": "7.0.2", "@typescript/typescript-linux-arm64": "7.0.2", "@typescript/typescript-linux-loong64": "7.0.2", "@typescript/typescript-linux-mips64el": "7.0.2", "@typescript/typescript-linux-ppc64": "7.0.2", "@typescript/typescript-linux-riscv64": "7.0.2", "@typescript/typescript-linux-s390x": "7.0.2", "@typescript/typescript-linux-x64": "7.0.2", "@typescript/typescript-netbsd-arm64": "7.0.2", "@typescript/typescript-netbsd-x64": "7.0.2", "@typescript/typescript-openbsd-arm64": "7.0.2", "@typescript/typescript-openbsd-x64": "7.0.2", "@typescript/typescript-sunos-x64": "7.0.2", "@typescript/typescript-win32-arm64": "7.0.2", "@typescript/typescript-win32-x64": "7.0.2" }, "bin": { "tsc": "bin/tsc" } }, "sha512-8FYau96o3NKOhbjKi/qNvG/W5jhzxkbdm5sj9AbZ/5T5sWqn3hJgLfGx27sRKZWTvyzCP8dLRBTf5tBTSRVUNA=="],
+
+    "uint8array-extras": ["uint8array-extras@1.6.0", "", {}, "sha512-8iAasVS4wUx0gPLjH8Xtz2PeDzTSiy8QiLGu2DT3X5GU+egFEQhpnbtkehbAwjvDcxIERmCYcysiODFmE3Ud0Q=="],
+
+    "undici-types": ["undici-types@8.9.0", "", {}, "sha512-KTDyRTYX8sWmKXAikPHHSyc63CRPETMctyjKFupcC6OBLXT3xsN0e9aF7m+mIXutFWpUXuedtowG7iLOzp0kQg=="],
+
+    "use-sync-external-store": ["use-sync-external-store@1.7.0", "", { "peerDependencies": { "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0" } }, "sha512-6L+EeigHMQhdaIPNIFUKwfWJSwWFQ8gJbJ2DLOs5sDIegTwR9fRxvnM3uciHKjIZhFz+KAv2emhWMRvDmMcY8A=="],
+
+    "vite": ["vite@8.3.2", "", { "dependencies": { "lightningcss": "^1.33.0", "picomatch": "^4.0.7", "postcss": "^8.5.28", "rolldown": "~1.2.11", "tinyglobby": "^0.2.17" }, "optionalDependencies": { "fsevents": "~2.3.3" }, "peerDependencies": { "@types/node": "^20.19.0 || >=22.12.0", "@vitejs/devtools": "^0.7.1", "esbuild": "^0.27.0 || ^0.28.0", "jiti": ">=1.21.0", "less": "^4.0.0", "sass": "^1.70.0", "sass-embedded": "^1.70.0", "stylus": ">=0.54.8", "sugarss": "^5.0.0", "terser": "^5.16.0", "tsx": "^4.8.1", "yaml": "^2.4.2" }, "optionalPeers": ["@types/node", "@vitejs/devtools", "esbuild", "jiti", "less", "sass", "sass-embedded", "stylus", "sugarss", "terser", "tsx", "yaml"], "bin": { "vite": "bin/vite.js" } }, "sha512-SQr1x6W5vVSbROg7vsyXIaxK9b0G7zsT68acdWWRmnBUsgDieLCRG+Rep9WdZgcposvv/GSnr4GUUBqB3vXq6w=="],
+
+    "zustand": ["zustand@5.0.15", "", { "peerDependencies": { "@types/react": ">=18.0.0", "immer": ">=9.0.6", "react": ">=18.0.0", "use-sync-external-store": ">=1.2.0" }, "optionalPeers": ["@types/react", "immer", "react", "use-sync-external-store"] }, "sha512-MpSEjRiBkA9crSYeOUH32rJC7SVqAbm0Fqcqge/bUi2PPoLcBWKOsG+C8mevmpr8TwXHBVkChbbJiyvkE+i/3A=="],
+
+    "@xyflow/react/zustand": ["zustand@4.5.7", "", { "dependencies": { "use-sync-external-store": "^1.2.2" }, "peerDependencies": { "@types/react": ">=16.8", "immer": ">=9.0.6", "react": ">=16.8" }, "optionalPeers": ["@types/react", "immer", "react"] }, "sha512-CHOUy7mu3lbD6o6LJLfllpjkzhHXSBlX8B9+qPddUsIfeF5S/UZ5q0kmCsnRqT1UHFQZchNFDDzMbQsuesHWlw=="],
+  }
+}
diff --git a/applications/service-topology/docs/service-topology.png b/applications/service-topology/docs/service-topology.png
new file mode 100644
index 00000000..a01e836e
Binary files /dev/null and b/applications/service-topology/docs/service-topology.png differ
diff --git a/applications/service-topology/index.html b/applications/service-topology/index.html
new file mode 100644
index 00000000..2552bdf6
--- /dev/null
+++ b/applications/service-topology/index.html
@@ -0,0 +1 @@
+<!doctype html><html lang="en"><head><meta charset="UTF-8"/><meta name="viewport" content="width=device-width, initial-scale=1.0"/><title>Service atlas</title></head><body><div id="root"></div><script type="module" src="/src/client/main.tsx"></script></body></html>
diff --git a/applications/service-topology/package.json b/applications/service-topology/package.json
new file mode 100644
index 00000000..34469e84
--- /dev/null
+++ b/applications/service-topology/package.json
@@ -0,0 +1,35 @@
+{
+  "name": "service-topology",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "bun --watch src/server/index.ts",
+    "dev:web": "vite --host 127.0.0.1",
+    "build": "vite build",
+    "start": "bun src/server/index.ts",
+    "typecheck": "tsc --noEmit",
+    "test": "bun test tests/graph.test.ts",
+    "test:integration": "bun test tests/database.test.ts",
+    "test:browser": "playwright test"
+  },
+  "dependencies": {
+    "@elysiajs/eden": "1.4.9",
+    "@sinclair/typebox": "0.34.52",
+    "@xyflow/react": "12.12.0",
+    "drizzle-orm": "0.45.3",
+    "elysia": "1.4.30",
+    "elkjs": "0.12.0",
+    "react": "19.3.0",
+    "react-dom": "19.3.0",
+    "zustand": "5.0.15"
+  },
+  "devDependencies": {
+    "@playwright/test": "1.63.0",
+    "@types/bun": "1.4.2",
+    "@types/react": "19.3.0",
+    "@types/react-dom": "19.3.0",
+    "@vitejs/plugin-react": "6.1.1",
+    "typescript": "7.0.2",
+    "vite": "8.3.2"
+  }
+}
diff --git a/applications/service-topology/playwright.config.ts b/applications/service-topology/playwright.config.ts
new file mode 100644
index 00000000..18552ef1
--- /dev/null
+++ b/applications/service-topology/playwright.config.ts
@@ -0,0 +1,10 @@
+import { defineConfig } from "@playwright/test";
+export default defineConfig({
+  testDir: "./tests/browser",
+  use: {
+    baseURL: process.env.BROWSER_BASE_URL || "http://127.0.0.1:3000",
+    viewport: { width: 1440, height: 1000 },
+  },
+  workers: 1,
+  reporter: "list",
+});
diff --git a/applications/service-topology/sql/001_roles.sql b/applications/service-topology/sql/001_roles.sql
new file mode 100644
index 00000000..7aa487c6
--- /dev/null
+++ b/applications/service-topology/sql/001_roles.sql
@@ -0,0 +1,10 @@
+\set ON_ERROR_STOP on
+\getenv migration_password PG_MIGRATION_PASSWORD
+\getenv app_password PG_APP_PASSWORD
+CREATE ROLE topology_owner NOLOGIN;
+CREATE ROLE topology_migration LOGIN PASSWORD :'migration_password';
+CREATE ROLE topology_app LOGIN PASSWORD :'app_password';
+GRANT topology_owner TO topology_migration;
+CREATE SCHEMA service_topology AUTHORIZATION topology_owner;
+REVOKE ALL ON SCHEMA service_topology FROM PUBLIC;
+GRANT USAGE ON SCHEMA service_topology TO topology_app;
diff --git a/applications/service-topology/sql/002_schema.sql b/applications/service-topology/sql/002_schema.sql
new file mode 100644
index 00000000..c1da665b
--- /dev/null
+++ b/applications/service-topology/sql/002_schema.sql
@@ -0,0 +1,28 @@
+\set ON_ERROR_STOP on
+BEGIN;
+SET LOCAL ROLE topology_owner;
+CREATE TABLE service_topology.graphs (
+  id UUID PRIMARY KEY,
+  title TEXT NOT NULL CHECK (length(title) BETWEEN 1 AND 80),
+  revision INTEGER NOT NULL CHECK (revision > 0),
+  document JSONB NOT NULL CHECK (
+    document ? 'nodes' AND document ? 'edges' AND
+    jsonb_typeof(document) = 'object' AND
+    jsonb_typeof(document->'nodes') = 'array' AND
+    jsonb_typeof(document->'edges') = 'array' AND
+    jsonb_array_length(document->'nodes') <= 100 AND
+    jsonb_array_length(document->'edges') <= 200
+  ),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp()
+);
+CREATE TABLE service_topology.revisions (
+  graph_id UUID NOT NULL REFERENCES service_topology.graphs(id) ON DELETE CASCADE,
+  revision INTEGER NOT NULL CHECK (revision > 0),
+  document JSONB NOT NULL,
+  saved_at TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp(),
+  PRIMARY KEY (graph_id, revision)
+);
+GRANT SELECT ON service_topology.graphs, service_topology.revisions TO topology_app;
+GRANT UPDATE (revision, document, updated_at) ON service_topology.graphs TO topology_app;
+GRANT INSERT ON service_topology.revisions TO topology_app;
+COMMIT;
diff --git a/applications/service-topology/sql/003_seed.sql b/applications/service-topology/sql/003_seed.sql
new file mode 100644
index 00000000..b56cf032
--- /dev/null
+++ b/applications/service-topology/sql/003_seed.sql
@@ -0,0 +1,24 @@
+\set ON_ERROR_STOP on
+BEGIN;
+SET LOCAL ROLE topology_owner;
+INSERT INTO service_topology.graphs (id, title, revision, document) VALUES
+('67bc2cf0-5b0f-45c8-bf6a-7b4bb5155a50', 'Storefront architecture', 1, '{
+  "nodes": [
+    {"id":"11111111-1111-4111-8111-111111111111","type":"service","position":{"x":80,"y":100},"data":{"label":"Storefront","kind":"web"}},
+    {"id":"22222222-2222-4222-8222-222222222222","type":"service","position":{"x":350,"y":100},"data":{"label":"Checkout API","kind":"api"}},
+    {"id":"33333333-3333-4333-8333-333333333333","type":"service","position":{"x":620,"y":20},"data":{"label":"Orders Postgres","kind":"database"}},
+    {"id":"44444444-4444-4444-8444-444444444444","type":"service","position":{"x":620,"y":180},"data":{"label":"Fulfilment worker","kind":"worker"}},
+    {"id":"55555555-5555-4555-8555-555555555555","type":"service","position":{"x":890,"y":180},"data":{"label":"Warehouse API","kind":"api"}}
+  ],
+  "edges": [
+    {"id":"aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaaa","source":"11111111-1111-4111-8111-111111111111","target":"22222222-2222-4222-8222-222222222222"},
+    {"id":"bbbbbbbb-bbbb-4bbb-8bbb-bbbbbbbbbbbb","source":"22222222-2222-4222-8222-222222222222","target":"33333333-3333-4333-8333-333333333333"},
+    {"id":"cccccccc-cccc-4ccc-8ccc-cccccccccccc","source":"22222222-2222-4222-8222-222222222222","target":"44444444-4444-4444-8444-444444444444"},
+    {"id":"dddddddd-dddd-4ddd-8ddd-dddddddddddd","source":"44444444-4444-4444-8444-444444444444","target":"55555555-5555-4555-8555-555555555555"}
+  ]
+}'::jsonb) ON CONFLICT (id) DO NOTHING;
+INSERT INTO service_topology.revisions (graph_id, revision, document)
+SELECT id, revision, document FROM service_topology.graphs
+WHERE id = '67bc2cf0-5b0f-45c8-bf6a-7b4bb5155a50'
+ON CONFLICT DO NOTHING;
+COMMIT;
diff --git a/applications/service-topology/src/client/api.ts b/applications/service-topology/src/client/api.ts
new file mode 100644
index 00000000..41ed3323
--- /dev/null
+++ b/applications/service-topology/src/client/api.ts
@@ -0,0 +1,3 @@
+import { treaty } from "@elysiajs/eden";
+import type { App } from "../server/app";
+export const api = treaty<App>(window.location.origin);
diff --git a/applications/service-topology/src/client/main.tsx b/applications/service-topology/src/client/main.tsx
new file mode 100644
index 00000000..8b0e5826
--- /dev/null
+++ b/applications/service-topology/src/client/main.tsx
@@ -0,0 +1,366 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+import {
+  ReactFlow,
+  Background,
+  Controls,
+  Handle,
+  Position,
+  MarkerType,
+  type NodeProps,
+  type Node,
+  type ReactFlowInstance,
+} from "@xyflow/react";
+import { api } from "./api";
+import { useGraph, documentFromState } from "./store";
+import {
+  DEMO_GRAPH_ID,
+  type ServiceKind,
+  type ServiceNode,
+  type ServiceEdge,
+} from "../shared/types";
+import "@xyflow/react/dist/style.css";
+import "./style.css";
+
+const kinds: ServiceKind[] = ["web", "api", "worker", "database"];
+function ServiceCard({
+  id,
+  data,
+  selected,
+}: NodeProps<Node<{ label: string; kind: ServiceKind }, "service">>) {
+  return (
+    <div
+      className={"service-card " + data.kind + (selected ? " selected" : "")}
+      data-testid="service-card"
+    >
+      <Handle type="target" position={Position.Left} />
+      <div className="service-kind">{data.kind}</div>
+      <strong>{data.label || "Untitled service"}</strong>
+      <span className="service-ref">{id.slice(0, 8)}</span>
+      <Handle type="source" position={Position.Right} />
+    </div>
+  );
+}
+const nodeTypes = { service: ServiceCard };
+
+function App() {
+  const state = useGraph();
+  const [selected, select] = React.useState<string>();
+  const [kind, setKind] = React.useState<ServiceKind>("api");
+  const [flow, setFlow] =
+    React.useState<ReactFlowInstance<ServiceNode, ServiceEdge>>();
+  const node = state.nodes.find((n) => n.id === selected);
+  async function reload() {
+    state.begin();
+    const generation = useGraph.getState().generation;
+    try {
+      const { data, error } = await api.api.graphs({ id: DEMO_GRAPH_ID }).get();
+      if (error || !data || !("document" in data))
+        throw new Error("Could not load the map.");
+      if (useGraph.getState().generation !== generation)
+        return state.fail(
+          "The draft changed while loading. Reload again when ready.",
+        );
+      useGraph.getState().load(data);
+      select(undefined);
+    } catch {
+      state.fail(
+        "Could not load the map. Check the server and database connection.",
+      );
+    } finally {
+      useGraph.setState({ busy: false });
+    }
+  }
+  React.useEffect(() => {
+    void reload();
+  }, []);
+  async function save() {
+    const { saved, generation } = useGraph.getState();
+    if (!saved) return;
+    const document = documentFromState();
+    state.begin();
+    try {
+      const { data, error } = await api.api
+        .graphs({ id: saved.id })
+        .put({ baseRevision: saved.revision, document });
+      if (error) {
+        const message =
+          typeof error.value === "object" &&
+          error.value &&
+          "message" in error.value
+            ? String(error.value.message)
+            : "Save failed.";
+        return state.fail(message, error.status === 409);
+      }
+      if (data && "document" in data) state.finish(data, generation);
+    } catch {
+      state.fail("Could not reach the server. Your draft is still here.");
+    }
+  }
+  async function layout() {
+    state.begin();
+    const startGeneration = useGraph.getState().generation;
+    try {
+      const { default: ELK } = await import("elkjs/lib/elk.bundled.js");
+      const elk = new ELK();
+      const graph = await elk.layout({
+        id: "root",
+        layoutOptions: {
+          "elk.algorithm": "layered",
+          "elk.direction": "RIGHT",
+          "elk.spacing.nodeNode": "70",
+          "elk.layered.spacing.nodeNodeBetweenLayers": "100",
+        },
+        children: state.nodes.map((n) => ({
+          id: n.id,
+          width: 200,
+          height: 104,
+        })),
+        edges: state.edges.map((e) => ({
+          id: e.id,
+          sources: [e.source],
+          targets: [e.target],
+        })),
+      });
+      if (useGraph.getState().generation !== startGeneration)
+        return state.fail("The map changed during layout. Run layout again.");
+      state.layout(
+        new Map(
+          (graph.children ?? []).map((n) => [
+            n.id,
+            { x: n.x ?? 0, y: n.y ?? 0 },
+          ]),
+        ),
+      );
+      requestAnimationFrame(() => {
+        void flow?.fitView({ padding: 0.25 });
+      });
+    } catch {
+      state.fail(
+        "Automatic layout could not finish. You can still drag services.",
+      );
+    } finally {
+      useGraph.setState({ busy: false });
+    }
+  }
+  const status = state.conflict
+    ? "Save conflict"
+    : state.dirty
+      ? "Unsaved changes"
+      : "Saved";
+  return (
+    <div className="shell">
+      <header>
+        <div className="brand">
+          <span className="brand-mark">↗</span>
+          <div>
+            <strong>Service atlas</strong>
+            <small>Architecture, kept in view</small>
+          </div>
+        </div>
+        <div className="header-meta">
+          <span className="local-dot" />
+          Trusted local demo
+        </div>
+      </header>
+      <main>
+        <section className="intro">
+          <div>
+            <div className="eyebrow">YOUR SERVICE MAP</div>
+            <h1>{state.saved?.title ?? "Storefront architecture"}</h1>
+            <p>
+              Map the services behind a request. Save a revision your team can
+              return to.
+            </p>
+          </div>
+          <div className="revision">
+            <span>COMMITTED REVISION</span>
+            <strong data-testid="revision">
+              {state.saved
+                ? String(state.saved.revision).padStart(2, "0")
+                : "—"}
+            </strong>
+          </div>
+        </section>
+        <div className="toolbar">
+          <div className="add-tools">
+            <select
+              aria-label="Service type"
+              value={kind}
+              onChange={(e) => setKind(e.target.value as ServiceKind)}
+            >
+              {kinds.map((k) => (
+                <option key={k} value={k}>
+                  {k[0].toUpperCase() + k.slice(1)} service
+                </option>
+              ))}
+            </select>
+            <button
+              onClick={() => state.add(kind)}
+              disabled={state.busy || !state.saved}
+            >
+              + Add service
+            </button>
+          </div>
+          <div className="actions">
+            <button
+              onClick={() => void layout()}
+              disabled={state.busy || !state.saved}
+            >
+              Auto layout
+            </button>
+            <span
+              className={"save-state " + (state.dirty ? "dirty" : "")}
+              data-testid="save-state"
+            >
+              {status}
+            </span>
+            <button
+              className="primary"
+              onClick={() => void save()}
+              disabled={state.busy || !state.dirty || state.conflict}
+            >
+              Save revision
+            </button>
+          </div>
+        </div>
+        {state.message && (
+          <div
+            role="status"
+            className={"notice " + (state.conflict ? "conflict" : "")}
+          >
+            {state.message}
+            {state.conflict && (
+              <button
+                onClick={() => {
+                  if (
+                    window.confirm(
+                      "Discard your local draft and load the saved revision?",
+                    )
+                  )
+                    void reload();
+                }}
+              >
+                Reload saved revision
+              </button>
+            )}
+          </div>
+        )}
+        <div className="workspace">
+          <div className="canvas">
+            <ReactFlow<ServiceNode, ServiceEdge>
+              nodes={state.nodes}
+              edges={state.edges}
+              nodeTypes={nodeTypes}
+              onInit={setFlow}
+              onNodesChange={state.nodeChanges}
+              onEdgesChange={state.edgeChanges}
+              onConnect={state.connect}
+              onNodeClick={(_, n) => select(n.id)}
+              onPaneClick={() => select(undefined)}
+              fitView
+              minZoom={0.2}
+              maxZoom={2}
+              defaultEdgeOptions={{
+                type: "smoothstep",
+                markerEnd: { type: MarkerType.ArrowClosed, color: "#758897" },
+                style: { stroke: "#758897", strokeWidth: 2 },
+              }}
+              deleteKeyCode={["Backspace", "Delete"]}
+            >
+              <Background color="#d3dce0" gap={24} />
+              <Controls />
+            </ReactFlow>
+            <div className="canvas-caption">
+              Drag to arrange · Connect right handle to left handle
+            </div>
+          </div>
+          <aside>
+            <div className="eyebrow">MAP DETAILS</div>
+            <h2>{node ? "Edit service" : "A clear path through the stack"}</h2>
+            {node ? (
+              <>
+                <label htmlFor="service-name">Service name</label>
+                <input
+                  id="service-name"
+                  aria-label="Service name"
+                  maxLength={60}
+                  value={node.data.label}
+                  onChange={(e) => state.rename(node.id, e.target.value)}
+                />
+                <div className="detail-kind">{node.data.kind} service</div>
+                <button
+                  className="danger"
+                  onClick={() => {
+                    state.remove(node.id);
+                    select(undefined);
+                  }}
+                >
+                  Remove service
+                </button>
+                <p>
+                  Removing a service also removes its connections. Save to
+                  commit the change.
+                </p>
+              </>
+            ) : (
+              <>
+                <p>
+                  Choose a service to rename it, or add a new part of your
+                  architecture.
+                </p>
+                <div className="counts">
+                  <div>
+                    <strong>{state.nodes.length}</strong>
+                    <span>services</span>
+                  </div>
+                  <div>
+                    <strong>{state.edges.length}</strong>
+                    <span>connections</span>
+                  </div>
+                </div>
+                <div className="legend">
+                  {kinds.map((k) => (
+                    <div key={k}>
+                      <span className={"swatch " + k} />
+                      {k}
+                    </div>
+                  ))}
+                </div>
+                <p>
+                  One connection per direction. Self connections are not
+                  allowed. Up to 100 services and 200 connections.
+                </p>
+              </>
+            )}
+            <div className="storage-note">
+              <strong>Remembered in Postgres</strong>
+              <p>
+                Every save commits the map and its revision together. A stale
+                tab must reload before saving.
+              </p>
+            </div>
+            <button
+              className="reload"
+              disabled={state.busy}
+              onClick={() => {
+                if (
+                  !state.dirty ||
+                  window.confirm("Discard your local draft and reload?")
+                )
+                  void reload();
+              }}
+            >
+              Reload map
+            </button>
+          </aside>
+        </div>
+      </main>
+      <footer>
+        <span>React Flow · Zustand · ELK · Elysia + Eden · Drizzle</span>
+        <span>ClickHouse Managed Postgres</span>
+      </footer>
+    </div>
+  );
+}
+createRoot(document.getElementById("root")!).render(<App />);
diff --git a/applications/service-topology/src/client/store.ts b/applications/service-topology/src/client/store.ts
new file mode 100644
index 00000000..d9bf8082
--- /dev/null
+++ b/applications/service-topology/src/client/store.ts
@@ -0,0 +1,161 @@
+import { create } from "zustand";
+import {
+  applyEdgeChanges,
+  applyNodeChanges,
+  type EdgeChange,
+  type NodeChange,
+  type Connection,
+} from "@xyflow/react";
+import type {
+  GraphDocument,
+  SavedGraph,
+  ServiceNode,
+  ServiceEdge,
+  ServiceKind,
+} from "../shared/types";
+type State = {
+  saved?: SavedGraph;
+  nodes: ServiceNode[];
+  edges: ServiceEdge[];
+  dirty: boolean;
+  busy: boolean;
+  message: string;
+  conflict: boolean;
+  generation: number;
+  load: (graph: SavedGraph) => void;
+  nodeChanges: (changes: NodeChange<ServiceNode>[]) => void;
+  edgeChanges: (changes: EdgeChange<ServiceEdge>[]) => void;
+  connect: (connection: Connection) => void;
+  add: (kind: ServiceKind) => void;
+  rename: (id: string, label: string) => void;
+  remove: (id: string) => void;
+  layout: (positions: Map<string, { x: number; y: number }>) => void;
+  begin: () => void;
+  finish: (graph: SavedGraph, generation: number) => void;
+  fail: (message: string, conflict?: boolean) => void;
+};
+export const useGraph = create<State>((set, get) => ({
+  nodes: [],
+  edges: [],
+  dirty: false,
+  busy: false,
+  message: "",
+  conflict: false,
+  generation: 0,
+  load: (graph) =>
+    set({
+      saved: graph,
+      nodes: graph.document.nodes,
+      edges: graph.document.edges,
+      dirty: false,
+      conflict: false,
+      message: "",
+      generation: get().generation + 1,
+    }),
+  nodeChanges: (changes) => {
+    const contentChange = changes.some(
+      (c) => c.type !== "select" && c.type !== "dimensions",
+    );
+    const nodes = applyNodeChanges(changes, get().nodes);
+    const ids = new Set(nodes.map((n) => n.id));
+    set({
+      nodes,
+      edges: get().edges.filter((e) => ids.has(e.source) && ids.has(e.target)),
+      ...(contentChange
+        ? { dirty: true, generation: get().generation + 1 }
+        : {}),
+    });
+  },
+  edgeChanges: (changes) =>
+    set({
+      edges: applyEdgeChanges(changes, get().edges),
+      ...(changes.some((c) => c.type !== "select")
+        ? { dirty: true, generation: get().generation + 1 }
+        : {}),
+    }),
+  connect: (c) => {
+    if (!c.source || !c.target) return;
+    if (c.source === c.target)
+      return set({ message: "A service cannot connect to itself." });
+    if (get().edges.some((e) => e.source === c.source && e.target === c.target))
+      return set({ message: "That connection already exists." });
+    if (get().edges.length >= 200)
+      return set({ message: "This map allows up to 200 connections." });
+    set({
+      edges: [
+        ...get().edges,
+        { id: crypto.randomUUID(), source: c.source, target: c.target },
+      ],
+      dirty: true,
+      generation: get().generation + 1,
+      message: "",
+    });
+  },
+  add: (kind) => {
+    if (get().nodes.length >= 100)
+      return set({ message: "This map allows up to 100 services." });
+    set({
+      nodes: [
+        ...get().nodes,
+        {
+          id: crypto.randomUUID(),
+          type: "service",
+          position: { x: 120 + get().nodes.length * 30, y: 320 },
+          data: { label: "New " + kind, kind },
+        },
+      ],
+      dirty: true,
+      generation: get().generation + 1,
+    });
+  },
+  rename: (id, label) =>
+    set({
+      nodes: get().nodes.map((n) =>
+        n.id === id ? { ...n, data: { ...n.data, label } } : n,
+      ),
+      dirty: true,
+      generation: get().generation + 1,
+    }),
+  remove: (id) =>
+    set({
+      nodes: get().nodes.filter((n) => n.id !== id),
+      edges: get().edges.filter((e) => e.source !== id && e.target !== id),
+      dirty: true,
+      generation: get().generation + 1,
+    }),
+  layout: (positions) =>
+    set({
+      nodes: get().nodes.map((n) => ({
+        ...n,
+        position: positions.get(n.id) ?? n.position,
+      })),
+      dirty: true,
+      generation: get().generation + 1,
+    }),
+  begin: () => set({ busy: true, message: "" }),
+  finish: (graph, generation) =>
+    set({
+      saved: graph,
+      busy: false,
+      conflict: false,
+      dirty: get().generation !== generation,
+      message:
+        get().generation === generation
+          ? "All changes saved."
+          : "Snapshot saved. Your newer edits are still unsaved.",
+    }),
+  fail: (message, conflict = false) => set({ message, conflict, busy: false }),
+}));
+export function documentFromState(): GraphDocument {
+  const { nodes, edges } = useGraph.getState();
+  // React Flow keeps selection and measured dimensions locally; persist only the document.
+  return {
+    nodes: nodes.map(({ id, type, position, data }) => ({
+      id,
+      type,
+      position: { ...position },
+      data: { ...data },
+    })),
+    edges: edges.map(({ id, source, target }) => ({ id, source, target })),
+  };
+}
diff --git a/applications/service-topology/src/client/style.css b/applications/service-topology/src/client/style.css
new file mode 100644
index 00000000..fd98ca72
--- /dev/null
+++ b/applications/service-topology/src/client/style.css
@@ -0,0 +1,392 @@
+:root {
+  font-family: system-ui, sans-serif;
+  color: #233a3c;
+  background: #f4f6f2;
+  font-synthesis: none;
+}
+* {
+  box-sizing: border-box;
+}
+body {
+  margin: 0;
+}
+button,
+input,
+select {
+  font: inherit;
+}
+button,
+select {
+  border: 1px solid #cad4d0;
+  border-radius: 7px;
+  background: #fff;
+  color: #284548;
+  padding: 10px 14px;
+}
+button {
+  cursor: pointer;
+  font-weight: 600;
+}
+button:hover {
+  background: #edf3ec;
+}
+button:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+.primary {
+  background: #294e46;
+  color: #fff;
+  border-color: #294e46;
+}
+.primary:hover {
+  background: #37665b;
+}
+.shell {
+  min-height: 100vh;
+}
+header {
+  height: 82px;
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  border-bottom: 1px solid #dde3db;
+  padding: 0 42px;
+  background: #fbfcf8;
+}
+.brand {
+  display: flex;
+  gap: 13px;
+  align-items: center;
+}
+.brand-mark {
+  background: #d4e7b6;
+  display: grid;
+  place-items: center;
+  width: 39px;
+  height: 39px;
+  border-radius: 10px;
+  font-size: 29px;
+}
+.brand strong {
+  font-family: "Trebuchet MS", sans-serif;
+  font-size: 20px;
+  display: block;
+}
+.brand small {
+  font-size: 12px;
+  color: #75857e;
+}
+.header-meta {
+  font-size: 12px;
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+.local-dot {
+  height: 7px;
+  width: 7px;
+  border-radius: 50%;
+  background: #699963;
+}
+main {
+  max-width: 1500px;
+  margin: auto;
+  padding: 35px 42px 18px;
+}
+.intro {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 28px;
+}
+.eyebrow {
+  font-size: 10px;
+  letter-spacing: 2px;
+  font-weight: 700;
+  color: #73826f;
+}
+h1 {
+  font-family: "Trebuchet MS", sans-serif;
+  font-weight: 500;
+  font-size: 32px;
+  letter-spacing: -1px;
+  margin: 10px 0;
+}
+p {
+  color: #74827e;
+  line-height: 1.65;
+  font-size: 13px;
+  margin: 8px 0;
+}
+.intro p {
+  font-size: 14px;
+}
+.revision {
+  display: flex;
+  gap: 20px;
+  align-items: center;
+  background: #e9eee1;
+  padding: 15px 20px;
+  border-radius: 8px;
+}
+.revision span {
+  width: 85px;
+  line-height: 1.7;
+  font-size: 9px;
+  letter-spacing: 1px;
+  color: #6e7e66;
+}
+.revision strong {
+  font-family: "Trebuchet MS", sans-serif;
+  font-size: 35px;
+  font-weight: 500;
+}
+.toolbar {
+  display: flex;
+  justify-content: space-between;
+  gap: 10px;
+  background: #fbfcf8;
+  padding: 14px 16px;
+  border: 1px solid #d8e1d7;
+  border-radius: 12px 12px 0 0;
+}
+.add-tools,
+.actions {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+.save-state {
+  font-size: 11px;
+  padding: 0 8px;
+  color: #638165;
+}
+.save-state.dirty {
+  color: #ac792d;
+}
+.workspace {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) 275px;
+  border: 1px solid #d8e1d7;
+  border-top: 0;
+  border-radius: 0 0 12px 12px;
+  overflow: hidden;
+}
+.canvas {
+  height: 590px;
+  position: relative;
+  background: #f9fbf6;
+}
+.canvas-caption {
+  position: absolute;
+  bottom: 18px;
+  left: 60px;
+  font-size: 10px;
+  color: #889690;
+  pointer-events: none;
+  background: #f9fbf6cc;
+  padding: 4px 8px;
+}
+aside {
+  background: #fbfcf8;
+  border-left: 1px solid #d8e1d7;
+  padding: 25px 22px;
+}
+h2 {
+  font-family: "Trebuchet MS", sans-serif;
+  font-size: 20px;
+  font-weight: 500;
+  line-height: 1.4;
+  margin: 14px 0;
+}
+label {
+  display: block;
+  font-size: 12px;
+  margin: 20px 0 7px;
+}
+input {
+  width: 100%;
+  padding: 10px;
+  border: 1px solid #c9d3ce;
+  border-radius: 6px;
+  background: white;
+}
+.service-card {
+  width: 200px;
+  min-height: 104px;
+  padding: 17px 19px;
+  border-radius: 9px;
+  border: 1px solid #cad6c5;
+  border-top: 4px solid #91ad73;
+  box-shadow: 0 3px 10px #233a3c07;
+  background: white;
+}
+.service-card.api {
+  border-top-color: #6c9da9;
+}
+.service-card.worker {
+  border-top-color: #bda273;
+}
+.service-card.database {
+  border-top-color: #a193b6;
+}
+.service-card.selected {
+  outline: 2px solid #345b4d;
+  outline-offset: 3px;
+}
+.service-kind {
+  text-transform: uppercase;
+  font-size: 9px;
+  letter-spacing: 1.5px;
+  color: #7a8c81;
+}
+.service-card strong {
+  font-size: 13px;
+  margin: 8px 0;
+  display: block;
+}
+.service-ref {
+  font-size: 9px;
+  color: #a0aea8;
+}
+.react-flow__handle {
+  background: #6b9180;
+  width: 9px;
+  height: 9px;
+  border: 2px solid white;
+}
+.counts {
+  display: flex;
+  gap: 30px;
+  border-top: 1px solid #e1e7dd;
+  border-bottom: 1px solid #e1e7dd;
+  padding: 20px 0;
+  margin: 20px 0;
+}
+.counts strong {
+  display: block;
+  font-family: "Trebuchet MS", sans-serif;
+  font-size: 28px;
+  font-weight: 500;
+}
+.counts span {
+  font-size: 11px;
+  color: #8b958e;
+}
+.legend {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 12px;
+  font-size: 11px;
+  margin: 22px 0;
+}
+.legend div {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+}
+.swatch {
+  width: 8px;
+  height: 8px;
+  border-radius: 2px;
+  background: #91ad73;
+}
+.swatch.api {
+  background: #6c9da9;
+}
+.swatch.worker {
+  background: #bda273;
+}
+.swatch.database {
+  background: #a193b6;
+}
+.storage-note {
+  border-top: 1px solid #e1e7dd;
+  padding-top: 20px;
+  margin-top: 30px;
+}
+.storage-note strong {
+  font-size: 12px;
+}
+.reload {
+  width: 100%;
+  margin-top: 18px;
+  background: transparent;
+  font-size: 11px;
+}
+.detail-kind {
+  font-size: 11px;
+  color: #73826f;
+  padding: 12px 0;
+}
+.danger {
+  color: #9c564d;
+  margin: 10px 0;
+  font-size: 12px;
+}
+.notice {
+  padding: 12px 16px;
+  font-size: 13px;
+  background: #e9efe1;
+  border-left: 3px solid #91ad73;
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+.notice.conflict {
+  background: #fff3df;
+  border-color: #bda273;
+}
+.notice button {
+  font-size: 12px;
+}
+footer {
+  max-width: 1500px;
+  margin: auto;
+  padding: 18px 42px 30px;
+  display: flex;
+  justify-content: space-between;
+  color: #8e9a92;
+  font-size: 10px;
+}
+@media (max-width: 900px) {
+  main {
+    padding: 24px 16px;
+  }
+  header {
+    padding: 0 16px;
+  }
+  .workspace {
+    grid-template-columns: 1fr;
+  }
+  aside {
+    border-left: 0;
+    border-top: 1px solid #d8e1d7;
+  }
+  .toolbar {
+    flex-wrap: wrap;
+  }
+  .intro {
+    gap: 10px;
+  }
+  h1 {
+    font-size: 25px;
+  }
+  .revision {
+    padding: 10px;
+  }
+  .canvas {
+    height: 450px;
+  }
+  footer {
+    padding: 20px 16px;
+    gap: 15px;
+  }
+  .header-meta {
+    display: none;
+  }
+  .actions {
+    flex-wrap: wrap;
+  }
+}
diff --git a/applications/service-topology/src/server/app.ts b/applications/service-topology/src/server/app.ts
new file mode 100644
index 00000000..b36be7d6
--- /dev/null
+++ b/applications/service-topology/src/server/app.ts
@@ -0,0 +1,55 @@
+import { Elysia, t } from "elysia";
+import type { Database } from "./database";
+import { graphProblem, saveSchema } from "./graph";
+import { readGraph, saveGraph, StaleRevision } from "./repository";
+import { allowedRequest } from "./origin";
+export const createApi = (db: Database) =>
+  new Elysia({ prefix: "/api" })
+    .onRequest(({ request, status }) => {
+      if (!allowedRequest(request))
+        return status(403, { message: "Use the configured local app origin." });
+    })
+    .get(
+      "/graphs/:id",
+      async ({ params, status }) => {
+        const graph = await readGraph(db, params.id);
+        return graph ?? status(404, { message: "Map not found." });
+      },
+      { params: t.Object({ id: t.String({ format: "uuid" }) }) },
+    )
+    .put(
+      "/graphs/:id",
+      async ({ params, body, status }) => {
+        const problem = graphProblem(body.document);
+        if (problem) return status(400, { message: problem });
+        try {
+          return await saveGraph(
+            db,
+            params.id,
+            body.baseRevision,
+            body.document,
+          );
+        } catch (error) {
+          if (error instanceof StaleRevision)
+            return status(409, { message: error.message });
+          console.error("Graph save failed.");
+          return status(500, {
+            message: "Save failed. Your draft is still available.",
+          });
+        }
+      },
+      {
+        params: t.Object({ id: t.String({ format: "uuid" }) }),
+        body: saveSchema,
+      },
+    )
+    .onError(({ code, status }) => {
+      if (code === "VALIDATION")
+        return status(422, {
+          message:
+            "The graph format is invalid. Check names, coordinates and size limits.",
+        });
+      console.error("API request failed.");
+      return status(500, { message: "The map could not be loaded." });
+    });
+export type App = ReturnType<typeof createApi>;
diff --git a/applications/service-topology/src/server/database.ts b/applications/service-topology/src/server/database.ts
new file mode 100644
index 00000000..ea2bba38
--- /dev/null
+++ b/applications/service-topology/src/server/database.ts
@@ -0,0 +1,89 @@
+import { SQL } from "bun";
+import { drizzle } from "drizzle-orm/bun-sql";
+export async function connectDatabase(
+  urlText = process.env.DATABASE_URL,
+  caPath = process.env.PG_CA_CERT_PATH,
+) {
+  if (!urlText) throw new Error("DATABASE_URL is required.");
+  const url = new URL(urlText);
+  if (
+    !["postgres:", "postgresql:"].includes(url.protocol) ||
+    url.search ||
+    url.hash
+  )
+    throw new Error("Use a plain Postgres URL without query parameters.");
+  const local = process.env.DATABASE_LOCAL === "true";
+  if (local && !["localhost", "127.0.0.1", "[::1]"].includes(url.hostname))
+    throw new Error("DATABASE_LOCAL requires a loopback host.");
+  if (!local && !caPath)
+    throw new Error("PG_CA_CERT_PATH is required for verified TLS.");
+  url.searchParams.set("sslmode", local ? "disable" : "verify-full");
+  const ca = local ? undefined : await Bun.file(caPath!).text();
+  const certificates =
+    ca?.match(
+      /-----BEGIN CERTIFICATE-----[\s\S]+?-----END CERTIFICATE-----/g,
+    ) ?? [];
+  if (!local && (certificates.length === 0 || certificates.length > 16))
+    throw new Error(
+      "PG_CA_CERT_PATH must contain between 1 and 16 PEM certificates.",
+    );
+  async function connect(trustedCa: string | undefined) {
+    const client = new SQL(url, {
+      max: 5,
+      connectionTimeout: 10,
+      idleTimeout: 30,
+      maxLifetime: 1800,
+      ...(local
+        ? {}
+        : {
+            tls: {
+              ca: trustedCa,
+              serverName: url.hostname,
+              rejectUnauthorized: true,
+            },
+          }),
+    });
+    try {
+      await client`SELECT 1`;
+      return { client, db: drizzle({ client }) };
+    } catch (error) {
+      await client.close({ timeout: 0 });
+      throw error;
+    }
+  }
+  try {
+    return await connect(ca);
+  } catch (originalError) {
+    if (
+      errorCode(originalError) !== "CERT_SIGNATURE_FAILURE" ||
+      certificates.length < 2
+    )
+      throw originalError;
+    // Bun can reject rotation bundles containing roots with the same subject.
+    // Retry only supplied anchors; certificate and hostname verification stay enabled.
+    for (const certificate of certificates) {
+      try {
+        return await connect(certificate);
+      } catch (error) {
+        if (!CA_ERRORS.has(errorCode(error))) throw error;
+      }
+    }
+    throw originalError;
+  }
+}
+function errorCode(error: unknown): string {
+  return error !== null && typeof error === "object" && "code" in error
+    ? String(error.code)
+    : "";
+}
+const CA_ERRORS = new Set([
+  "CERT_SIGNATURE_FAILURE",
+  "UNABLE_TO_GET_ISSUER_CERT",
+  "UNABLE_TO_GET_ISSUER_CERT_LOCALLY",
+  "UNABLE_TO_VERIFY_LEAF_SIGNATURE",
+  "SELF_SIGNED_CERT_IN_CHAIN",
+  "DEPTH_ZERO_SELF_SIGNED_CERT",
+  "CERT_HAS_EXPIRED",
+  "CERT_NOT_YET_VALID",
+]);
+export type Database = Awaited<ReturnType<typeof connectDatabase>>["db"];
diff --git a/applications/service-topology/src/server/graph.ts b/applications/service-topology/src/server/graph.ts
new file mode 100644
index 00000000..e4155bda
--- /dev/null
+++ b/applications/service-topology/src/server/graph.ts
@@ -0,0 +1,62 @@
+import { t } from "elysia";
+import type { GraphDocument } from "../shared/types";
+export const graphSchema = t.Object({
+  nodes: t.Array(
+    t.Object({
+      id: t.String({ format: "uuid" }),
+      type: t.Literal("service"),
+      position: t.Object({
+        x: t.Number({ minimum: -100000, maximum: 100000 }),
+        y: t.Number({ minimum: -100000, maximum: 100000 }),
+      }),
+      data: t.Object({
+        label: t.String({ minLength: 1, maxLength: 60 }),
+        kind: t.Union([
+          t.Literal("web"),
+          t.Literal("api"),
+          t.Literal("worker"),
+          t.Literal("database"),
+        ]),
+      }),
+    }),
+    { maxItems: 100 },
+  ),
+  edges: t.Array(
+    t.Object({
+      id: t.String({ format: "uuid" }),
+      source: t.String({ format: "uuid" }),
+      target: t.String({ format: "uuid" }),
+    }),
+    { maxItems: 200 },
+  ),
+});
+export const saveSchema = t.Object({
+  baseRevision: t.Integer({ minimum: 1, maximum: 2147483646 }),
+  document: graphSchema,
+});
+export function graphProblem(document: GraphDocument): string | undefined {
+  const ids = new Set(document.nodes.map((n) => n.id));
+  if (ids.size !== document.nodes.length) return "Service IDs must be unique.";
+  if (document.nodes.some((n) => !n.data.label.trim()))
+    return "Service names cannot be blank.";
+  if (
+    document.nodes.some(
+      (n) => !Number.isFinite(n.position.x) || !Number.isFinite(n.position.y),
+    )
+  )
+    return "Coordinates must be finite.";
+  const edges = new Set<string>();
+  const pairs = new Set<string>();
+  for (const edge of document.edges) {
+    if (edges.has(edge.id)) return "Connection IDs must be unique.";
+    if (!ids.has(edge.source) || !ids.has(edge.target))
+      return "Connections must reference existing services.";
+    if (edge.source === edge.target)
+      return "A service cannot connect to itself.";
+    const pair = edge.source + ":" + edge.target;
+    if (pairs.has(pair))
+      return "Only one connection in each direction is allowed.";
+    pairs.add(pair);
+    edges.add(edge.id);
+  }
+}
diff --git a/applications/service-topology/src/server/index.ts b/applications/service-topology/src/server/index.ts
new file mode 100644
index 00000000..9e339cbb
--- /dev/null
+++ b/applications/service-topology/src/server/index.ts
@@ -0,0 +1,24 @@
+import { Elysia } from "elysia";
+import { connectDatabase } from "./database";
+import { createApi } from "./app";
+import { allowedRequest } from "./origin";
+const { db, client } = await connectDatabase();
+const app = new Elysia()
+  .onRequest(({ request, status }) => {
+    if (!allowedRequest(request)) return status(403);
+  })
+  .use(createApi(db))
+  .get("/", () => Bun.file("dist/index.html"))
+  .get("/assets/:file", ({ params, status }) =>
+    /^[a-zA-Z0-9_.-]+$/.test(params.file)
+      ? Bun.file("dist/assets/" + params.file)
+      : status(404),
+  )
+  .listen({ port: Number(process.env.PORT || 3000), hostname: "127.0.0.1" });
+console.log("Service atlas listening on http://127.0.0.1:" + app.server?.port);
+for (const signal of ["SIGTERM", "SIGINT"] as const)
+  process.on(signal, async () => {
+    await app.stop();
+    await client.close();
+    process.exit(0);
+  });
diff --git a/applications/service-topology/src/server/origin.ts b/applications/service-topology/src/server/origin.ts
new file mode 100644
index 00000000..8990fdde
--- /dev/null
+++ b/applications/service-topology/src/server/origin.ts
@@ -0,0 +1,18 @@
+export function allowedRequest(
+  request: Request,
+  appOrigin = process.env.APP_ORIGIN || "http://127.0.0.1:3000",
+) {
+  const origin = new URL(appOrigin);
+  if (
+    origin.protocol !== "http:" ||
+    origin.origin !== appOrigin ||
+    !["127.0.0.1", "localhost", "[::1]"].includes(origin.hostname)
+  )
+    throw new Error(
+      "APP_ORIGIN must be a loopback HTTP origin without a trailing slash.",
+    );
+  if (new URL(request.url).host !== origin.host) return false;
+  return (
+    request.method !== "PUT" || request.headers.get("origin") === appOrigin
+  );
+}
diff --git a/applications/service-topology/src/server/repository.ts b/applications/service-topology/src/server/repository.ts
new file mode 100644
index 00000000..2c0d48af
--- /dev/null
+++ b/applications/service-topology/src/server/repository.ts
@@ -0,0 +1,36 @@
+import { and, eq, sql } from "drizzle-orm";
+import type { Database } from "./database";
+import { graphs, revisions } from "./schema";
+import type { GraphDocument, SavedGraph } from "../shared/types";
+export class StaleRevision extends Error {}
+function view(row: typeof graphs.$inferSelect): SavedGraph {
+  return { ...row, updatedAt: row.updatedAt.toISOString() };
+}
+export async function readGraph(db: Database, id: string) {
+  const [row] = await db.select().from(graphs).where(eq(graphs.id, id));
+  return row ? view(row) : undefined;
+}
+export async function saveGraph(
+  db: Database,
+  id: string,
+  baseRevision: number,
+  document: GraphDocument,
+) {
+  return db.transaction(async (tx) => {
+    const [saved] = await tx
+      .update(graphs)
+      .set({
+        revision: baseRevision + 1,
+        document,
+        updatedAt: sql`clock_timestamp()`,
+      })
+      .where(and(eq(graphs.id, id), eq(graphs.revision, baseRevision)))
+      .returning();
+    if (!saved)
+      throw new StaleRevision("The graph changed. Reload before saving.");
+    await tx
+      .insert(revisions)
+      .values({ graphId: id, revision: saved.revision, document });
+    return view(saved);
+  });
+}
diff --git a/applications/service-topology/src/server/schema.ts b/applications/service-topology/src/server/schema.ts
new file mode 100644
index 00000000..1b9e6389
--- /dev/null
+++ b/applications/service-topology/src/server/schema.ts
@@ -0,0 +1,44 @@
+import {
+  pgSchema,
+  uuid,
+  text,
+  integer,
+  customType,
+  timestamp,
+  primaryKey,
+} from "drizzle-orm/pg-core";
+import type { GraphDocument } from "../shared/types";
+const topology = pgSchema("service_topology");
+// Bun 1.4 serializes JSONB parameters itself. Drizzle's default JSONB string
+// encoder would encode a JSON string a second time, so pass the object through.
+const graphJson = customType<{
+  data: GraphDocument;
+  driverData: GraphDocument;
+}>({
+  dataType: () => "jsonb",
+  toDriver: (value) => value,
+  fromDriver: (value) => value,
+});
+export const graphs = topology.table("graphs", {
+  id: uuid("id").primaryKey(),
+  title: text("title").notNull(),
+  revision: integer("revision").notNull(),
+  document: graphJson("document").notNull(),
+  updatedAt: timestamp("updated_at", { withTimezone: true })
+    .notNull()
+    .defaultNow(),
+});
+export const revisions = topology.table(
+  "revisions",
+  {
+    graphId: uuid("graph_id")
+      .notNull()
+      .references(() => graphs.id),
+    revision: integer("revision").notNull(),
+    document: graphJson("document").notNull(),
+    savedAt: timestamp("saved_at", { withTimezone: true })
+      .notNull()
+      .defaultNow(),
+  },
+  (table) => [primaryKey({ columns: [table.graphId, table.revision] })],
+);
diff --git a/applications/service-topology/src/shared/types.ts b/applications/service-topology/src/shared/types.ts
new file mode 100644
index 00000000..dea86593
--- /dev/null
+++ b/applications/service-topology/src/shared/types.ts
@@ -0,0 +1,17 @@
+export type ServiceKind = "web" | "api" | "worker" | "database";
+export type ServiceNode = {
+  id: string;
+  type: "service";
+  position: { x: number; y: number };
+  data: { label: string; kind: ServiceKind };
+};
+export type ServiceEdge = { id: string; source: string; target: string };
+export type GraphDocument = { nodes: ServiceNode[]; edges: ServiceEdge[] };
+export type SavedGraph = {
+  id: string;
+  title: string;
+  revision: number;
+  document: GraphDocument;
+  updatedAt: string;
+};
+export const DEMO_GRAPH_ID = "67bc2cf0-5b0f-45c8-bf6a-7b4bb5155a50";
diff --git a/applications/service-topology/tests/browser/editor.spec.ts b/applications/service-topology/tests/browser/editor.spec.ts
new file mode 100644
index 00000000..7840e8b1
--- /dev/null
+++ b/applications/service-topology/tests/browser/editor.spec.ts
@@ -0,0 +1,92 @@
+import { expect, test } from "@playwright/test";
+test("edit, connect, layout, save, reload and stale tab conflict", async ({
+  page,
+  context,
+}) => {
+  const other = await context.newPage();
+  await page.goto("/");
+  await other.goto("/");
+  await expect(page.getByTestId("revision")).not.toHaveText("—");
+  const originalRevision = Number(
+    await page.getByTestId("revision").innerText(),
+  );
+  await page.getByRole("button", { name: "+ Add service" }).click();
+  await page.getByTestId("service-card").filter({ hasText: "New api" }).click();
+  await page
+    .getByRole("textbox", { name: "Service name" })
+    .fill("Inventory API");
+  const node = page
+    .locator(".react-flow__node")
+    .filter({ hasText: "Inventory API" });
+  const prior = await node.boundingBox();
+  if (!prior) throw new Error("Node not rendered");
+  await page.mouse.move(prior.x + 100, prior.y + 55);
+  await page.mouse.down();
+  await page.mouse.move(prior.x + 160, prior.y + 105, { steps: 8 });
+  await page.mouse.up();
+  await expect(page.getByTestId("save-state")).toHaveText("Unsaved changes");
+  // React Flow's actual source/target handles create an edge.
+  const edgeCount = await page.locator(".react-flow__edge").count();
+  const source = await page
+    .locator(".react-flow__node")
+    .filter({ hasText: "Inventory API" })
+    .locator(".react-flow__handle.source")
+    .boundingBox();
+  const target = await page
+    .locator(".react-flow__node")
+    .filter({ hasText: "Checkout API" })
+    .locator(".react-flow__handle.target")
+    .boundingBox();
+  if (!source || !target) throw new Error("Handles not rendered");
+  await page.mouse.move(
+    source.x + source.width / 2,
+    source.y + source.height / 2,
+  );
+  await page.mouse.down();
+  await page.mouse.move(
+    target.x + target.width / 2,
+    target.y + target.height / 2,
+    { steps: 12 },
+  );
+  await page.mouse.up();
+  await expect(page.locator(".react-flow__edge")).toHaveCount(edgeCount + 1);
+  await page.getByRole("button", { name: "Auto layout" }).click();
+  await expect(
+    page.getByRole("button", { name: "Save revision" }),
+  ).toBeEnabled();
+  await page.getByRole("button", { name: "Save revision" }).click();
+  await expect(page.getByTestId("revision")).toHaveText(
+    String(originalRevision + 1).padStart(2, "0"),
+  );
+  await page.reload();
+  await expect(
+    page.getByTestId("service-card").filter({ hasText: "Inventory API" }),
+  ).toBeVisible();
+  await other.getByRole("button", { name: "+ Add service" }).click();
+  await other.getByRole("button", { name: "Save revision" }).click();
+  await expect(other.getByTestId("save-state")).toHaveText("Save conflict");
+  other.once("dialog", (dialog) => dialog.accept());
+  await other.getByRole("button", { name: "Reload saved revision" }).click();
+  await expect(other.getByTestId("revision")).toHaveText(
+    String(originalRevision + 1).padStart(2, "0"),
+  );
+  await page.locator(".react-flow__pane").click({ position: { x: 20, y: 20 } });
+  await page.screenshot({
+    path: process.env.SCREENSHOT_PATH || "test-results/topology.png",
+    fullPage: true,
+  });
+  await other.close();
+  await page
+    .getByTestId("service-card")
+    .filter({ hasText: "Inventory API" })
+    .click();
+  await page.getByRole("button", { name: "Remove service" }).click();
+  await page.getByRole("button", { name: "Save revision" }).click();
+  await expect(page.getByTestId("revision")).toHaveText(
+    String(originalRevision + 2).padStart(2, "0"),
+  );
+  await page.reload();
+  await expect(
+    page.getByTestId("service-card").filter({ hasText: "Inventory API" }),
+  ).toHaveCount(0);
+});
diff --git a/applications/service-topology/tests/database.test.ts b/applications/service-topology/tests/database.test.ts
new file mode 100644
index 00000000..c3191471
--- /dev/null
+++ b/applications/service-topology/tests/database.test.ts
@@ -0,0 +1,191 @@
+import {
+  afterAll,
+  afterEach,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  test,
+} from "bun:test";
+import { connectDatabase } from "../src/server/database";
+import { createApi } from "../src/server/app";
+import type { GraphDocument } from "../src/shared/types";
+let runtime: Awaited<ReturnType<typeof connectDatabase>>;
+let admin: Awaited<ReturnType<typeof connectDatabase>>;
+let id: string;
+const doc: GraphDocument = {
+  nodes: [
+    {
+      id: "11111111-1111-4111-8111-111111111111",
+      type: "service",
+      position: { x: 10, y: 20 },
+      data: { label: "Test API", kind: "api" },
+    },
+  ],
+  edges: [],
+};
+beforeAll(async () => {
+  if (!process.env.DATABASE_TEST_ADMIN_URL)
+    throw new Error(
+      "Set DATABASE_TEST_ADMIN_URL to the migration login for a dedicated test database.",
+    );
+  runtime = await connectDatabase();
+  admin = await connectDatabase(process.env.DATABASE_TEST_ADMIN_URL);
+});
+beforeEach(async () => {
+  id = crypto.randomUUID();
+  await admin.client.begin(async (tx) => {
+    await tx`SET LOCAL ROLE topology_owner`;
+    await tx`INSERT INTO service_topology.graphs(id,title,revision,document) VALUES (${id},'Test',1,${doc}::jsonb)`;
+    await tx`INSERT INTO service_topology.revisions(graph_id,revision,document) VALUES (${id},1,${doc}::jsonb)`;
+  });
+});
+afterEach(async () => {
+  await admin.client.begin(async (tx) => {
+    await tx`SET LOCAL ROLE topology_owner`;
+    await tx`DELETE FROM service_topology.graphs WHERE id=${id}`;
+  });
+});
+afterAll(async () => {
+  await runtime?.client.close();
+  await admin?.client.close();
+});
+function request(body: unknown) {
+  return createApi(runtime.db).handle(
+    new Request("http://127.0.0.1:3000/api/graphs/" + id, {
+      method: "PUT",
+      headers: {
+        "content-type": "application/json",
+        origin: "http://127.0.0.1:3000",
+      },
+      body: JSON.stringify(body),
+    }),
+  );
+}
+describe("real Postgres saves", () => {
+  test("sixteen concurrent edits commit one revision", async () => {
+    const replies = await Promise.all(
+      Array.from({ length: 16 }, () =>
+        request({ baseRevision: 1, document: doc }),
+      ),
+    );
+    expect(replies.filter((r) => r.status === 200)).toHaveLength(1);
+    expect(replies.filter((r) => r.status === 409)).toHaveLength(15);
+    const row =
+      await runtime.client`SELECT revision,document,jsonb_typeof(document) AS document_type FROM service_topology.graphs WHERE id=${id}`;
+    expect(row[0].revision).toBe(2);
+    expect(row[0].document_type).toBe("object");
+    expect(row[0].document).toEqual(doc);
+    const count =
+      await runtime.client`SELECT count(*)::int AS total FROM service_topology.revisions WHERE graph_id=${id}`;
+    expect(count[0].total).toBe(2);
+  });
+  test("snapshot failure rolls current graph back", async () => {
+    await admin.client.begin(async (tx) => {
+      await tx`SET LOCAL ROLE topology_owner`;
+      await tx`INSERT INTO service_topology.revisions(graph_id,revision,document) VALUES(${id},2,${doc}::jsonb)`;
+    });
+    const changed = structuredClone(doc);
+    changed.nodes[0].data.label = "Should roll back";
+    expect((await request({ baseRevision: 1, document: changed })).status).toBe(
+      500,
+    );
+    const rows =
+      await runtime.client`SELECT revision,document,jsonb_typeof(document) AS document_type FROM service_topology.graphs WHERE id=${id}`;
+    expect(rows[0].revision).toBe(1);
+    expect(rows[0].document).toEqual(doc);
+  });
+  test("rejects malformed and semantically invalid graph before storage", async () => {
+    expect(
+      (
+        await request({
+          baseRevision: 1,
+          document: { nodes: [{ bad: "shape" }], edges: [] },
+        })
+      ).status,
+    ).toBe(422);
+    const invalid = structuredClone(doc);
+    invalid.edges = [
+      {
+        id: crypto.randomUUID(),
+        source: doc.nodes[0].id,
+        target: crypto.randomUUID(),
+      },
+    ];
+    expect((await request({ baseRevision: 1, document: invalid })).status).toBe(
+      400,
+    );
+    const duplicate = structuredClone(doc);
+    duplicate.nodes.push(duplicate.nodes[0]);
+    expect(
+      (await request({ baseRevision: 1, document: duplicate })).status,
+    ).toBe(400);
+    const huge = structuredClone(doc);
+    huge.nodes = Array.from({ length: 101 }, () => ({
+      ...doc.nodes[0],
+      id: crypto.randomUUID(),
+    }));
+    expect((await request({ baseRevision: 1, document: huge })).status).toBe(
+      422,
+    );
+    const rows =
+      await runtime.client`SELECT revision FROM service_topology.graphs WHERE id=${id}`;
+    expect(rows[0].revision).toBe(1);
+  });
+  test("database requires both graph arrays and rejects untrusted requests", async () => {
+    await expect(
+      Promise.resolve(
+        runtime.client`UPDATE service_topology.graphs SET document=${{ nodes: [] }}::jsonb WHERE id=${id}`,
+      ),
+    ).rejects.toThrow();
+    await expect(
+      Promise.resolve(
+        runtime.client`UPDATE service_topology.graphs SET document=${{ nodes: null, edges: [] }}::jsonb WHERE id=${id}`,
+      ),
+    ).rejects.toThrow();
+    const api = createApi(runtime.db);
+    expect(
+      (
+        await api.handle(
+          new Request("http://untrusted.example:3000/api/graphs/" + id),
+        )
+      ).status,
+    ).toBe(403);
+    expect(
+      (
+        await api.handle(
+          new Request("http://127.0.0.1:3000/api/graphs/" + id, {
+            method: "PUT",
+            headers: {
+              origin: "http://untrusted.example",
+              "content-type": "application/json",
+            },
+            body: JSON.stringify({ baseRevision: 1, document: doc }),
+          }),
+        )
+      ).status,
+    ).toBe(403);
+  });
+  test("runtime role cannot change schema or overwrite snapshots", async () => {
+    await expect(
+      Promise.resolve(
+        runtime.client`CREATE TABLE service_topology.forbidden(id int)`,
+      ),
+    ).rejects.toThrow();
+    await expect(
+      Promise.resolve(
+        runtime.client`UPDATE service_topology.revisions SET document='{}' WHERE graph_id=${id}`,
+      ),
+    ).rejects.toThrow();
+    await expect(
+      Promise.resolve(
+        runtime.client`DELETE FROM service_topology.revisions WHERE graph_id=${id}`,
+      ),
+    ).rejects.toThrow();
+    await expect(
+      Promise.resolve(
+        runtime.client`UPDATE service_topology.graphs SET title='Other' WHERE id=${id}`,
+      ),
+    ).rejects.toThrow();
+  });
+});
diff --git a/applications/service-topology/tests/graph.test.ts b/applications/service-topology/tests/graph.test.ts
new file mode 100644
index 00000000..09ab1f1b
--- /dev/null
+++ b/applications/service-topology/tests/graph.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect, test } from "bun:test";
+import { graphProblem } from "../src/server/graph";
+import type { GraphDocument } from "../src/shared/types";
+const first = "11111111-1111-4111-8111-111111111111";
+const second = "22222222-2222-4222-8222-222222222222";
+const document = (): GraphDocument => ({
+  nodes: [first, second].map((id) => ({
+    id,
+    type: "service",
+    position: { x: 1, y: 2 },
+    data: { label: "API", kind: "api" },
+  })),
+  edges: [],
+});
+describe("graph meaning", () => {
+  test("allows cycles between distinct services", () => {
+    const d = document();
+    d.edges = [
+      { id: crypto.randomUUID(), source: first, target: second },
+      { id: crypto.randomUUID(), source: second, target: first },
+    ];
+    expect(graphProblem(d)).toBeUndefined();
+  });
+  test("rejects dangling connections", () => {
+    const d = document();
+    d.edges = [
+      { id: crypto.randomUUID(), source: first, target: crypto.randomUUID() },
+    ];
+    expect(graphProblem(d)).toContain("existing");
+  });
+  test("rejects repeated nodes and blank names", () => {
+    const d = document();
+    d.nodes.push(d.nodes[0]);
+    expect(graphProblem(d)).toContain("unique");
+    d.nodes.pop();
+    d.nodes[0].data.label = "  ";
+    expect(graphProblem(d)).toContain("blank");
+  });
+  test("rejects self connections and duplicates", () => {
+    const d = document();
+    d.edges = [{ id: crypto.randomUUID(), source: first, target: first }];
+    expect(graphProblem(d)).toContain("itself");
+    d.edges = [
+      { id: crypto.randomUUID(), source: first, target: second },
+      { id: crypto.randomUUID(), source: first, target: second },
+    ];
+    expect(graphProblem(d)).toContain("one connection");
+  });
+  test("rejects non-finite coordinates", () => {
+    const d = document();
+    d.nodes[0].position.x = Infinity;
+    expect(graphProblem(d)).toContain("finite");
+  });
+});
diff --git a/applications/service-topology/tsconfig.json b/applications/service-topology/tsconfig.json
new file mode 100644
index 00000000..e10361bc
--- /dev/null
+++ b/applications/service-topology/tsconfig.json
@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "jsx": "react-jsx",
+    "strict": true,
+    "noEmit": true,
+    "allowImportingTsExtensions": true,
+    "skipLibCheck": true,
+    "types": ["bun", "vite/client"]
+  },
+  "include": ["src", "tests", "vite.config.ts", "playwright.config.ts"]
+}
diff --git a/applications/service-topology/vite.config.ts b/applications/service-topology/vite.config.ts
new file mode 100644
index 00000000..1d8d85cc
--- /dev/null
+++ b/applications/service-topology/vite.config.ts
@@ -0,0 +1,6 @@
+import { defineConfig } from "vite";
+import react from "@vitejs/plugin-react";
+export default defineConfig({
+  plugins: [react()],
+  server: { proxy: { "/api": "http://127.0.0.1:3000" } },
+});