diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5aa7082..cb92ce2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,7 +2,7 @@ name: CI
 
 on:
   push:
-    branches: [master]
+    branches: [main]
   pull_request:
 
 permissions:
diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index f329da3..0546d79 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -2,7 +2,7 @@ name: Mutation
 
 on:
   push:
-    branches: [master]
+    branches: [main]
   pull_request:
     types: [opened, ready_for_review, synchronize, reopened]
   workflow_dispatch:
@@ -11,7 +11,7 @@ permissions:
   contents: read
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.event.pull_request.number || (github.event_name == 'push' && 'master') || github.run_id }}
+  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.event.pull_request.number || (github.event_name == 'push' && github.ref) || github.run_id }}
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 jobs:
@@ -37,20 +37,20 @@ jobs:
       - name: Rebuild mutation results
         if: github.event_name == 'push'
         run: npm run mutation -- --force
-      # Runs on master go one at a time and only the tip saves, so an older run cannot replace newer results.
+      # Runs on the default branch go one at a time and only the tip saves, so an older run cannot replace newer results.
       - name: Check baseline revision
-        id: master-tip
+        id: default-branch-tip
         if: ${{ !cancelled() && github.event_name == 'push' && hashFiles('reports/stryker-incremental.json') != '' }}
         shell: bash
         run: |
-          tip=$(git ls-remote --exit-code origin refs/heads/master)
+          tip=$(git ls-remote --exit-code origin "$GITHUB_REF")
           if [[ "${tip%%$'\t'*}" == "$GITHUB_SHA" ]]; then
             echo "current=true" >> "$GITHUB_OUTPUT"
           else
             echo "current=false" >> "$GITHUB_OUTPUT"
           fi
       - uses: actions/cache/save@v6
-        if: ${{ !cancelled() && steps.master-tip.outputs.current == 'true' }}
+        if: ${{ !cancelled() && steps.default-branch-tip.outputs.current == 'true' }}
         with:
           path: reports/stryker-incremental.json
           key: mutation-${{ runner.os }}-${{ github.run_id }}-${{ github.run_attempt }}
diff --git a/README.md b/README.md
index 15b3ec6..6b301b5 100644
--- a/README.md
+++ b/README.md
@@ -32,4 +32,4 @@ Run `npm install` at the root to install dependencies and link the packages decl
 - [index.html](index.html) is the entry page. Vite uses its defaults without a configuration file, including its browser target and no production source maps.
 - Vite transpiles TypeScript without type-checking. Run `npm run typecheck` to check types; `npm run verify-gate` includes it before the tests and build.
 - TypeScript is pinned to the 6.x line.
-- Mutation testing uses [Stryker's incremental mode](https://stryker-mutator.io/docs/stryker-js/incremental/). Changes outside mutated source and test files can leave reused results stale; run `npm run mutation -- --force` for a fresh full run. CI does this on pushes to `master`.
+- Mutation testing uses [Stryker's incremental mode](https://stryker-mutator.io/docs/stryker-js/incremental/). Changes outside mutated source and test files can leave reused results stale; run `npm run mutation -- --force` for a fresh full run. CI does this on pushes to the default branch.