diff --git a/.changeset/long-radios-join.md b/.changeset/long-radios-join.md
new file mode 100644
index 000000000..e7140b780
--- /dev/null
+++ b/.changeset/long-radios-join.md
@@ -0,0 +1,5 @@
+---
+"@systemfsoftware/stryker-config": none
+---
+
+sharedConfig sets disableBail and mutator.mutantSetPolicy 'full' when STRYKER_KILL_MATRIX=1, for the kill-matrix CI lane; unset, the config is unchanged.
diff --git a/.github/workflows/kill-matrix.yml b/.github/workflows/kill-matrix.yml
new file mode 100644
index 000000000..eacc59dd2
--- /dev/null
+++ b/.github/workflows/kill-matrix.yml
@@ -0,0 +1,288 @@
+name: Kill matrix
+
+on:
+  workflow_call:
+    inputs:
+      projects:
+        description: Comma-separated projects to mutate, the dogfood corpus.
+        type: string
+        default: packages/stryker-js,packages/stryker-js-typescript-checker,packages/stryker-js-vitest-runner,test/e2e-core
+  workflow_dispatch:
+    inputs:
+      projects:
+        description: Comma-separated projects to mutate, the dogfood corpus.
+        type: string
+        default: packages/stryker-js,packages/stryker-js-typescript-checker,packages/stryker-js-vitest-runner,test/e2e-core
+
+concurrency:
+  group: kill-matrix-${{ github.ref }}
+  cancel-in-progress: false
+
+permissions:
+  contents: read
+
+env:
+  TARGET_SECONDS: 200
+  MAX_SHARDS: 20
+  PROJECTS: ${{ inputs.projects }}
+  PUBLISHED_CLI: ${{ github.workspace }}/packages/stryker-js/node_modules/.bin/stryker
+  PLAN: plan.json
+  KILL_MATRIX_OUT: kill-matrix-out
+  KILL_MATRIX_ARTIFACT: kill-matrix-${{ github.run_number }}
+  STRYKER_KILL_MATRIX: "1"
+
+jobs:
+  plan:
+    name: kill-matrix · plan
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    outputs:
+      matrix: ${{ steps.plan.outputs.matrix }}
+      count: ${{ steps.plan.outputs.count }}
+    steps:
+      - uses: actions/checkout@v7
+      - uses: pnpm/action-setup@v6
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          cache: pnpm
+      - uses: ./.github/actions/released-tarballs
+      - run: pnpm install --frozen-lockfile
+
+      - id: plan
+        name: Plan every mutant, from scratch
+        run: |
+          $PUBLISHED_CLI plan \
+            --target-seconds "$TARGET_SECONDS" \
+            --max-shards "$MAX_SHARDS" \
+            --projects "$PROJECTS" \
+            --full \
+            --out "$PLAN"
+          echo "matrix=$(jq -c '.matrix' "$PLAN")" >> "$GITHUB_OUTPUT"
+          echo "count=$(jq '.matrix.include | length' "$PLAN")" >> "$GITHUB_OUTPUT"
+
+      - uses: actions/upload-artifact@v7
+        with:
+          name: kill-matrix-plan
+          path: ${{ env.PLAN }}
+          retention-days: 7
+
+  build:
+    name: kill-matrix · build
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    outputs:
+      key: ${{ steps.key.outputs.key }}
+    steps:
+      - uses: actions/checkout@v7
+
+      - id: key
+        name: Content key of the build
+        env:
+          KEY: mutation-build-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml', 'turbo.json', 'packages/**', 'test/e2e-core/**') }}
+        run: echo "key=$KEY" >> "$GITHUB_OUTPUT"
+
+      - uses: pnpm/action-setup@v6
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          cache: pnpm
+      - uses: ./.github/actions/released-tarballs
+      - run: pnpm install --frozen-lockfile
+
+      - name: Restore the build the mutation lane cached
+        uses: actions/cache/restore@v6
+        with:
+          path: .turbo/cache
+          key: ${{ steps.key.outputs.key }}
+          restore-keys: |
+            mutation-build-${{ runner.os }}-
+
+      - name: Build every mutated project
+        run: |
+          mapfile -t filters < <(tr ',' '\n' <<< "$PROJECTS" | sed 's|^|--filter=./|')
+          pnpm exec turbo run build --output-logs=errors-only --log-order=stream "${filters[@]}"
+
+  mutation:
+    name: kill-matrix · shard ${{ matrix.shard }}
+    needs: [plan, build]
+    if: ${{ needs.plan.result == 'success' && needs.build.result == 'success' && needs.plan.outputs.count != '0' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJSON(needs.plan.outputs.matrix) }}
+    steps:
+      - uses: actions/checkout@v7
+      - uses: pnpm/action-setup@v6
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          cache: pnpm
+      - uses: ./.github/actions/released-tarballs
+      - run: pnpm install --frozen-lockfile
+      - uses: actions/download-artifact@v8
+        with:
+          name: kill-matrix-plan
+
+      - name: Restore the build every shard shares
+        uses: actions/cache/restore@v6
+        with:
+          path: .turbo/cache
+          key: ${{ needs.build.outputs.key }}
+
+      - name: Build the projects this shard mutates
+        env:
+          SHARD: ${{ matrix.shard }}
+        run: |
+          mapfile -t filters < <(
+            jq -r --arg shard "$SHARD" \
+              '.shards[] | select("\(.index)/\(.count)" == $shard) | .projects[].project' "$PLAN" \
+              | sort -u | sed 's|^|--filter=./|'
+          )
+          pnpm exec turbo run build --output-logs=errors-only --log-order=stream "${filters[@]}"
+
+      - id: shard
+        name: Name the shard output
+        env:
+          SHARD: ${{ matrix.shard }}
+        run: echo "slug=${SHARD//\//of}" >> "$GITHUB_OUTPUT"
+
+      - name: Mutation, recording every killer
+        env:
+          SHARD: ${{ matrix.shard }}
+        run: |
+          $PUBLISHED_CLI run \
+            --plan "$PLAN" \
+            --shard "$SHARD" \
+            --out "reports/shards/${{ steps.shard.outputs.slug }}"
+
+      - id: upload
+        name: Upload the shard's incremental parts
+        if: always()
+        uses: actions/upload-artifact@v7
+        with:
+          name: kill-matrix-shard-${{ steps.shard.outputs.slug }}
+          path: reports/shards
+          if-no-files-found: error
+          retention-days: 7
+          overwrite: true
+
+      - name: Annotate a failed shard
+        if: ${{ failure() }}
+        env:
+          SHARD: ${{ matrix.shard }}
+        run: |
+          echo "::error title=Kill matrix shard $SHARD failed::The full re-verification of shard $SHARD did not finish, so the kill matrix is incomplete. Read the log at ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} and any partial parts in artifact kill-matrix-shard-${SHARD//\//of}."
+
+  collect:
+    name: kill-matrix · collect
+    needs: [plan, mutation]
+    if: ${{ needs.mutation.result == 'success' && needs.plan.result == 'success' && needs.plan.outputs.count != '0' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v7
+      - uses: pnpm/action-setup@v6
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          cache: pnpm
+      - uses: ./.github/actions/released-tarballs
+      - run: pnpm install --frozen-lockfile
+      - uses: actions/download-artifact@v8
+        with:
+          name: kill-matrix-plan
+      - name: Download every shard's incremental parts into shards/<k>of<n>
+        uses: actions/download-artifact@v8
+        with:
+          pattern: kill-matrix-shard-*
+          path: shards
+          merge-multiple: true
+
+      - name: Merge into one incremental report per project
+        run: |
+          shards=()
+          while read -r shard; do
+            shards+=("shards/${shard//\//of}")
+          done < <(jq -r '.shards[] | "\(.index)/\(.count)"' "$PLAN")
+          $PUBLISHED_CLI merge \
+            --plan "$PLAN" \
+            "${shards[@]}" \
+            --out reports/mutation
+          for dir in ${PROJECTS//,/ }; do
+            merged="reports/mutation/$dir/stryker-incremental.json"
+            if [ ! -f "$merged" ]; then
+              echo "::error title=No kill matrix for $dir::$merged is missing, so this run did not cover $dir"
+              exit 1
+            fi
+            mkdir -p "$KILL_MATRIX_OUT/$dir"
+            cp "$merged" "$KILL_MATRIX_OUT/$dir/stryker-incremental.json"
+          done
+
+      - name: Summarise the kill matrix
+        run: |
+          node --input-type=module - <<'NODE'
+          import { appendFileSync, readFileSync } from 'node:fs'
+
+          const planned = new Map()
+          for (const shard of JSON.parse(readFileSync(process.env.PLAN, 'utf8')).shards) {
+            for (const { project, mutants } of shard.projects) {
+              planned.set(project, [...(planned.get(project) ?? []), ...mutants])
+            }
+          }
+          const rows = []
+          const notFull = []
+          const unreported = []
+          let corpusKilled = 0
+          let corpusMulti = 0
+          for (const project of process.env.PROJECTS.split(',').map((p) => p.trim()).filter(Boolean)) {
+            const report = JSON.parse(readFileSync(`${process.env.KILL_MATRIX_OUT}/${project}/stryker-incremental.json`, 'utf8'))
+            if (report.mutantSetPolicy !== 'full') notFull.push(`${project} (${report.mutantSetPolicy})`)
+            const mutants = Object.values(report.files ?? {}).flatMap((file) => file.mutants ?? [])
+            const reported = new Set(mutants.map((mutant) => mutant.id))
+            const missing = (planned.get(project) ?? []).filter((id) => !reported.has(id))
+            if (missing.length > 0) unreported.push(`${project}: ${missing.length} planned ids missing, e.g. ${missing.slice(0, 5).join(' ')}`)
+            const killed = mutants.filter((mutant) => mutant.status === 'Killed')
+            const multi = killed.filter((mutant) => (mutant.killedBy ?? []).length >= 2).length
+            const testsCompleted = mutants.reduce((total, mutant) => total + (mutant.testsCompleted ?? 0), 0)
+            corpusKilled += killed.length
+            corpusMulti += multi
+            rows.push(`| ${project} | ${mutants.length} | ${killed.length} | ${multi} | ${testsCompleted} |`)
+          }
+          if (notFull.length > 0) {
+            console.log(`::error title=Kill matrix is not a full matrix::${notFull.join(', ')} did not run with mutator.mutantSetPolicy 'full'; re-run the kill-matrix lane.`)
+            process.exitCode = 1
+          }
+          if (unreported.length > 0) {
+            console.log(`::error title=Kill matrix lost planned mutants::${unreported.join('; ')}. The shard runs emitted a different mutant set than the plan; check that every step loaded the config with STRYKER_KILL_MATRIX=1, then re-run the kill-matrix lane.`)
+            process.exitCode = 1
+          }
+          if (corpusKilled > 0 && corpusMulti === 0) {
+            console.log(`::error title=Kill matrix recorded only first killers::${corpusKilled} mutants were killed and none names a second killer, so the runner bailed on the first failing test. Check that every project's config keeps disableBail from sharedConfig, then re-run the kill-matrix lane.`)
+            process.exitCode = 1
+          }
+          appendFileSync(process.env.GITHUB_STEP_SUMMARY, [
+            '## Kill matrix',
+            '',
+            '| project | mutants | killed | mutants with ≥2 killers | tests completed |',
+            '| --- | ---: | ---: | ---: | ---: |',
+            ...rows,
+            '',
+            `Artifact: \`${process.env.KILL_MATRIX_ARTIFACT}\` · run: ${process.env.GITHUB_SERVER_URL}/${process.env.GITHUB_REPOSITORY}/actions/runs/${process.env.GITHUB_RUN_ID}`,
+            '',
+          ].join('\n'))
+          NODE
+
+      - uses: actions/upload-artifact@v7
+        with:
+          name: ${{ env.KILL_MATRIX_ARTIFACT }}
+          path: ${{ env.KILL_MATRIX_OUT }}/*
+          if-no-files-found: error
+          retention-days: 90
+          overwrite: true
+
+      - name: Annotate a failed collect
+        if: ${{ failure() }}
+        run: |
+          echo "::error title=Kill matrix was not published::No complete kill-matrix artifact was produced. Read the log at ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} for the missing project or failed merge, then re-run the kill-matrix lane."
diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index d487b55fe..827d085cb 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -13,6 +13,13 @@ on:
         description: Re-verify every mutant instead of reusing the incremental cache
         type: boolean
         default: false
+      lane:
+        description: Which lane to run. `kill-matrix` runs only the full kill-matrix lane.
+        type: choice
+        options:
+          - all
+          - kill-matrix
+        default: all
   schedule:
     - cron: "17 3 * * *"
 
@@ -39,7 +46,7 @@ env:
 jobs:
   plan:
     name: plan · shards from the incremental cost record
-    if: github.event_name != 'push' || github.event.head_commit.author.username != 'github-actions[bot]'
+    if: ${{ github.event.inputs.lane != 'kill-matrix' && (github.event_name != 'push' || github.event.head_commit.author.username != 'github-actions[bot]') }}
     runs-on: ubuntu-latest
     timeout-minutes: 20
     permissions:
@@ -95,7 +102,7 @@ jobs:
 
   build:
     name: build · once for every shard
-    if: github.event_name != 'push' || github.event.head_commit.author.username != 'github-actions[bot]'
+    if: ${{ github.event.inputs.lane != 'kill-matrix' && (github.event_name != 'push' || github.event.head_commit.author.username != 'github-actions[bot]') }}
     runs-on: ubuntu-latest
     timeout-minutes: 20
     outputs:
@@ -150,7 +157,7 @@ jobs:
   mutation:
     name: mutation · shard ${{ matrix.shard }}
     needs: [plan, build]
-    if: ${{ needs.plan.result == 'success' && needs.build.result == 'success' && needs.plan.outputs.count != '0' }}
+    if: ${{ github.event.inputs.lane != 'kill-matrix' && needs.plan.result == 'success' && needs.build.result == 'success' && needs.plan.outputs.count != '0' }}
     runs-on: ubuntu-latest
     timeout-minutes: 60
     strategy:
@@ -250,7 +257,7 @@ jobs:
   report:
     name: Mutation report
     needs: [plan, mutation]
-    if: ${{ !cancelled() && needs.plan.result == 'success' && needs.plan.outputs.count != '0' }}
+    if: ${{ github.event.inputs.lane != 'kill-matrix' && !cancelled() && needs.plan.result == 'success' && needs.plan.outputs.count != '0' }}
     runs-on: ubuntu-latest
     timeout-minutes: 30
     permissions:
@@ -350,3 +357,10 @@ jobs:
           gh api --paginate "repos/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID/artifacts" \
             --jq '.artifacts[] | select(.name | startswith("mutation-shard-")) | .id' \
           | while read -r id; do gh api -X DELETE "repos/$GITHUB_REPOSITORY/actions/artifacts/$id"; done
+
+  kill-matrix:
+    name: Kill matrix
+    if: ${{ (github.event_name == 'push' && github.event.head_commit.author.username != 'github-actions[bot]') || github.event.inputs.lane == 'kill-matrix' }}
+    permissions:
+      contents: read
+    uses: ./.github/workflows/kill-matrix.yml
diff --git a/packages/toolchain/stryker-config/lib/base.d.ts b/packages/toolchain/stryker-config/lib/base.d.ts
index 65be7062d..244ad0442 100644
--- a/packages/toolchain/stryker-config/lib/base.d.ts
+++ b/packages/toolchain/stryker-config/lib/base.d.ts
@@ -12,6 +12,8 @@ export interface SharedConfig {
   cleanTempDir: 'always'
   thresholds: { high: number; low: number; break: number }
   concurrency?: string
+  disableBail?: boolean
+  mutator?: { mutantSetPolicy: 'default' | 'full'; [key: string]: unknown }
 }
 
 export const sharedConfig: SharedConfig
diff --git a/packages/toolchain/stryker-config/lib/base.js b/packages/toolchain/stryker-config/lib/base.js
index cff53e075..c5dfbe75a 100644
--- a/packages/toolchain/stryker-config/lib/base.js
+++ b/packages/toolchain/stryker-config/lib/base.js
@@ -9,6 +9,8 @@ const envConcurrency = process.env['STRYKER_CONCURRENCY'] ??
 
 const restoredShardReports = ['reports/stryker-incremental-*.json']
 
+const killMatrixLane = process.env['STRYKER_KILL_MATRIX'] === '1'
+
 export const sharedConfig = {
   packageManager: 'pnpm',
   reporters: isAgent || isCI ? ['json', 'html'] : ['progress', 'html', 'json'],
@@ -22,6 +24,7 @@ export const sharedConfig = {
   cleanTempDir: 'always',
   thresholds: { high: 100, low: 80, break: 100 },
   ...(envConcurrency !== undefined ? { concurrency: envConcurrency } : {}),
+  ...(killMatrixLane ? { disableBail: true, mutator: { mutantSetPolicy: 'full' } } : {}),
 }
 
 /**