diff --git a/.cargo/mutants.toml b/.cargo/mutants.toml
new file mode 100644
index 000000000..ede43a210
--- /dev/null
+++ b/.cargo/mutants.toml
@@ -0,0 +1,10 @@
+# Configuration for cargo-mutants <https://mutants.rs>.
+# Run locally with `cargo mutants`; CI runs it against the pull request diff.
+
+# ignore build.rs downloads and hashes frontend assets at build time as well as
+# executing the build.
+exclude_globs = ["build.rs"]
+
+# The suite starts a web server and talks to a database, so a mutant that
+# deadlocks needs a longer leash than the ~4s baseline would allow.
+minimum_test_timeout = 60
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e3977c512..1db1162a4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -543,3 +543,30 @@ jobs:
           TAG_SUFFIX: ${{ matrix.variant != 'minimal' && format('-{0}', matrix.variant) || '' }}
         run: |
           docker buildx imagetools inspect "${REGISTRY_IMAGE}:${GITHUB_REF_NAME}${TAG_SUFFIX}"
+
+  mutants:
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    continue-on-error: true
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-mutants
+      - name: Set up cargo cache
+        uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4
+        with:
+          shared-key: rust-sqlpage-mutants
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: Mutate only the lines this pull request changed
+        run: |
+          git diff "origin/${{ github.base_ref }}...HEAD" > mutants.diff
+          cargo mutants --in-diff mutants.diff --jobs 2
+      - uses: actions/upload-artifact@v7
+        if: always()
+        with:
+          name: mutants-report
+          path: mutants.out/
diff --git a/.gitignore b/.gitignore
index 994459944..328c531b8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,5 @@ sqlpage/sqlpage.db
 tests_uploads/
 /test-results/
 /playwright-report/
+/mutants.out*/
+mutants.diff
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5144ae1e4..003c8dcc4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
  - `stacked` is now ignored on chart types that cannot stack, instead of displaying an empty chart.
  - Screen readers now announce the title of the modal component instead of an unnamed dialog.
  - `sqlpage.request_body` and `sqlpage.request_body_base64` now return NULL when the request has no body. A body that cannot be read, such as one exceeding the payload limit, is now reported as an error instead of being silently replaced with an empty body.
+ - `sqlpage.fetch_with_meta` now returns JSON response bodies under the documented `body` key.
 
 ## v0.45
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index f764460e2..c5dc394a1 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -95,6 +95,19 @@ export DATABASE_URL=mssql://root:Password123!@localhost/sqlpage
 cargo test
 ```
 
+### Mutation Testing
+
+[cargo-mutants](https://mutants.rs) finds dead code or missing tests by mutating 
+params and re-running the suite.
+
+```bash
+cargo mutants --in-diff <(git diff origin/main...HEAD) # what your branch changed
+```
+
+A whole-codebase run takes hours, so CI only mutates the lines a pull request
+touches, and reports without failing the build. Results are attached to the run
+as the `mutants-report` artifact.
+
 ### End-to-End Tests
 
 We use Playwright for end-to-end testing of dynamic frontend features.
@@ -225,6 +238,7 @@ git checkout -b feature/your-feature-name
    - Execute all tests across multiple platforms (Linux, Windows)
    - Build Docker images for multiple architectures
    - Run frontend linting, typechecking and unit tests (`npm test`)
+   - Report surviving mutants for the lines the pull request changed
    - Test against multiple databases (SQLite, PostgreSQL, MySQL, MSSQL, Oracle, and ODBC)
 
 ## Release Process