diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..0ea371b
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,22 @@
+# Dependabot security updates were already on for this repo, but without this
+# config there were no scheduled version-update PRs — so a dependency could sit
+# on a vulnerable-but-unadvised release indefinitely. This adds weekly checks
+# for both the Python deps and the GitHub Actions used by CI.
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    labels: ["dependencies"]
+    groups:
+      # One PR for routine bumps; security fixes still arrive individually.
+      python-minor-and-patch:
+        update-types: ["minor", "patch"]
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    labels: ["dependencies", "ci"]
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4952df7..95f6d9f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,7 +11,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
-        python: ["3.10", "3.13"]
+        python: ["3.10", "3.13"]  # matches requires-python floor
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v5
@@ -20,9 +20,26 @@ jobs:
           python-version: ${{ matrix.python }}
       - run: pip install -e '.[dev]'
       - run: pytest
+      - name: Lint
+        run: ruff check abapit tests
+      - name: Security lint
+        run: bandit -q -r abapit -ll
       - name: Demo smoke test
         run: |
           abapit export devices --demo | head -1 | grep serialNumber
           abapit changes --demo 2>&1 | grep -q "Need at least two snapshots"
         env:
           ABAPIT_DATA_DIR: ${{ runner.temp }}/abapit-data
+
+  audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+      # Fails the build on a known-vulnerable dependency. Paired with the
+      # version floors in pyproject.toml, this is what stops the app shipping
+      # a CVE-carrying starlette/python-multipart again.
+      - run: pip install -e . pip-audit
+      - run: pip-audit --strict
diff --git a/README.md b/README.md
index 3ecaea4..1124c4f 100644
--- a/README.md
+++ b/README.md
@@ -50,14 +50,18 @@ it to your Dock. For a standalone window with its own icon, open
 After pulling new code, run `abapit restart-app` so the service loads it.
 `abapit uninstall-app` removes both.
 
-`install-app` reuses whatever Python you ran it with (it works against the
-3.9 that ships with macOS Command Line Tools — abapit supports 3.9+).
+`install-app` reuses whatever Python you ran it with, so it needs **Python
+3.10+**. That floor is a security one, not a syntax one: every patched
+`starlette` and `python-multipart` release requires 3.10, and the last
+3.9-compatible versions carry unfixed CVEs. The 3.9 that ships with macOS
+Command Line Tools is therefore not supported — use the self-contained
+bundle below, which brings its own interpreter.
 
 ### Self-contained app (bundled Python)
 
 To get an `abapit.app` that depends on **no** system Python — so it runs on a
-clean Mac, and isn't tied to Apple's aging 3.9 — build a bundle with its own
-CPython:
+clean Mac, with a current interpreter and patched dependencies — build a
+bundle with its own CPython:
 
 ```sh
 scripts/build_app.sh                 # -> ~/Applications/abapit.app + login service
@@ -222,6 +226,11 @@ profiles; switch from the header dropdown.
 - **Egress**: the only hosts ever contacted are `account.apple.com`,
   `api-business.apple.com` / `api-school.apple.com`, and — for a Mosyle org —
   `businessapi.mosyle.com` plus `businessapilogs.mosyle.com`.
+- **Dependencies**: `pyproject.toml` carries security floors for the packages
+  that parse or transport untrusted input (`python-multipart`, `starlette`,
+  `cryptography`, `h2`). CI runs `pip-audit --strict`, `ruff`, and `bandit`, so
+  a newly-disclosed CVE in a dependency fails the build even if nothing in the
+  repo changed; Dependabot opens weekly update PRs on top of that.
 - **Honest limits**: anything running as *your user* can read the config and
   key files — the same trust model as `~/.ssh`; secrets are not in the
   Keychain. The Apple API account can read inventory, reassign devices, and
diff --git a/pyproject.toml b/pyproject.toml
index d766309..7ed5c7e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -8,10 +8,12 @@ version = "0.2.0"
 description = "Apple Business API Tool — a local web GUI for the Apple Business and Apple School Manager APIs, built for Mac admins."
 readme = "README.md"
 license = { text = "MIT" }
-# 3.9 is the Python that ships with macOS (Command Line Tools); abapit runs
-# on it (no 3.10+ syntax/stdlib), so admins can install against the system
-# Python without adding a newer one.
-requires-python = ">=3.9"
+# 3.10+ is a SECURITY floor, not a syntax one. Every patched starlette and
+# python-multipart release requires >=3.10; the last 3.9-compatible versions
+# (starlette 0.49.3, python-multipart 0.0.20) carry unfixed CVEs. macOS ships
+# 3.9, but abapit no longer needs it — scripts/build_app.sh bundles its own
+# CPython, so the supported install has a current interpreter either way.
+requires-python = ">=3.10"
 authors = [{ name = "abapit contributors" }]
 keywords = ["apple", "abm", "asm", "mdm", "macadmin", "apple-business-manager"]
 classifiers = [
@@ -20,19 +22,27 @@ classifiers = [
     "Intended Audience :: System Administrators",
     "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Topic :: System :: Systems Administration",
 ]
 dependencies = [
-    "fastapi>=0.110",
+    "fastapi>=0.121",
     "uvicorn>=0.29",
     "jinja2>=3.1",
     "httpx[http2]>=0.27",
     "PyJWT[crypto]>=2.8",
-    "python-multipart>=0.0.9",
+    # Security floors (pip-audit). These parse or transport untrusted input, so
+    # they are pinned above the advisories rather than left to transitive luck:
+    #   python-multipart <0.0.31  - multipart form parsing DoS chain
+    #   starlette        <1.3.1   - request handling advisories
+    #   cryptography     <50.0.0  - PYSEC-2026-3552
+    #   h2               <4.4.1   - PYSEC-2026-3628 (HTTP/2, enabled in client.py)
+    "python-multipart>=0.0.31",
+    "starlette>=1.3.1",
+    "cryptography>=50.0.0",
+    "h2>=4.4.1",
 ]
 
 [project.optional-dependencies]
@@ -53,7 +63,7 @@ packages = ["abapit"]
 # for best-effort launchctl calls — are left out on purpose. A linter that
 # cries wolf gets ignored, which defeats the point of having one.
 [tool.ruff]
-target-version = "py39"
+target-version = "py310"
 line-length = 100
 
 [tool.ruff.lint]