diff --git a/.github/bin/merge_rust_coverage.py b/.github/bin/merge_rust_coverage.py
new file mode 100644
index 000000000000..e49f4232c9cf
--- /dev/null
+++ b/.github/bin/merge_rust_coverage.py
@@ -0,0 +1,97 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+import collections
+import sys
+
+import coverage
+
+
+class RustCoveragePlugin(coverage.CoveragePlugin):
+    def file_reporter(self, filename: str):
+        return RustCoverageFileReporter(filename)
+
+
+class RustCoverageFileReporter(coverage.FileReporter):
+    def lines(self) -> set[int]:
+        # XXX: Need a better way to handle this state!
+        return set(raw_data[self.filename])
+
+
+def coverage_init(
+    reg: coverage.plugin_support.Plugins,
+    options: coverage.types.TConfigSectionOut,
+) -> None:
+    reg.add_file_tracer(RustCoveragePlugin())
+
+
+def main(*lcov_paths: str):
+    cov = coverage.Coverage()
+    # XXX: Nasty mucking in semi-public APIs
+    cov.config.plugins.append("coverage_rust_plugin")
+    sys.modules["coverage_rust_plugin"] = sys.modules[__name__]
+
+    coverage_data = coverage.CoverageData(suffix="rust")
+
+    # XXX: global state! Bad!
+    global raw_data
+    # {filename: {line_number: count}}
+    raw_data = collections.defaultdict(lambda: collections.defaultdict(int))
+    current_file = None
+    for p in lcov_paths:
+        with open(p) as f:
+            for line in f:
+                line = line.strip()
+                if line == "end_of_record":
+                    assert current_file is not None
+                    current_file = None
+                    continue
+
+                prefix, suffix = line.split(":", 1)
+                match prefix:
+                    case "SF":
+                        current_file = raw_data[suffix]
+                    case "DA":
+                        assert current_file is not None
+                        line_number, count = suffix.split(",")
+                        current_file[int(line_number)] += int(count)
+                    case (
+                        "BRF"
+                        | "BRH"
+                        | "FN"
+                        | "FNDA"
+                        | "FNF"
+                        | "FNH"
+                        | "LF"
+                        | "LH"
+                    ):
+                        # These are various forms of metadata and summary stats
+                        # that we don't need.
+                        pass
+                    case _:
+                        raise NotImplementedError(prefix)
+
+    covered_lines = {
+        file_name: [line for line, c in lines.items() if c > 0]
+        for file_name, lines in raw_data.items()
+    }
+    coverage_data.add_lines(covered_lines)
+    coverage_data.add_file_tracers(
+        {
+            file_name: "coverage_rust_plugin.RustCoveragePlugin"
+            for file_name in covered_lines
+        }
+    )
+    coverage_data.write()
+
+    cov.combine()
+    coverage_percent = cov.report(show_missing=True)
+    if coverage_percent < 100:
+        print("+++ Python coverage under 100% +++")
+        cov.html_report()
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main(*sys.argv[1:])
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 57240787d843..f555a025daa0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -449,50 +449,21 @@ jobs:
         id: combinecoverage
         run: |
           set +e
-          python -m coverage combine
-          echo "## Python Coverage" >> $GITHUB_STEP_SUMMARY
-          python -m coverage report -m --fail-under=100 > COV_REPORT
+          echo "## Coverage" >> $GITHUB_STEP_SUMMARY
+          python .github/bin/merge_rust_coverage.py *.lcov > COV_REPORT
           COV_EXIT_CODE=$?
           cat COV_REPORT
           if [ $COV_EXIT_CODE -ne 0 ]; then
-            echo "🚨 Python Coverage failed. Under 100" | tee -a $GITHUB_STEP_SUMMARY
+            echo "🚨 Coverage failed. Under 100" | tee -a $GITHUB_STEP_SUMMARY
           fi
-          echo '```' >> $GITHUB_STEP_SUMMARY
+          echo "```" >> $GITHUB_STEP_SUMMARY
           cat COV_REPORT >> $GITHUB_STEP_SUMMARY
-          echo '```' >> $GITHUB_STEP_SUMMARY
+          echo "```" >> $GITHUB_STEP_SUMMARY
           exit $COV_EXIT_CODE
-      - name: Combine rust coverage and fail if it's <100%.
-        if: ${{ always() }}
-        id: combinerustcoverage
-        run: |
-          set +e
-          sudo apt-get install -y lcov
-          RUST_COVERAGE_OUTPUT=$(lcov $(for f in *.lcov; do echo --add-tracefile "$f"; done) -o combined.lcov | grep lines)
-          echo "## Rust Coverage" >> $GITHUB_STEP_SUMMARY
-          echo '```' >> $GITHUB_STEP_SUMMARY
-          echo $RUST_COVERAGE_OUTPUT >> $GITHUB_STEP_SUMMARY
-          echo '```' >> $GITHUB_STEP_SUMMARY
-          if ! echo "$RUST_COVERAGE_OUTPUT" | grep "100.0%"; then
-            echo "🚨 Rust Coverage failed. Under 100" | tee -a $GITHUB_STEP_SUMMARY
-            exit 1
-          fi
-      - name: Create rust coverage HTML
-        run: genhtml combined.lcov -o rust-coverage
-        if: ${{ failure() && steps.combinerustcoverage.outcome == 'failure' }}
-      - name: Create coverage HTML
-        run: python -m coverage html
-        if: ${{ failure() && steps.combinecoverage.outcome == 'failure' }}
       - name: Upload HTML report.
         uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
         with:
-          name: _html-report
+          name: _html-coverage-report
           path: htmlcov
           if-no-files-found: ignore
         if: ${{ failure() && steps.combinecoverage.outcome == 'failure' }}
-      - name: Upload rust HTML report.
-        uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
-        with:
-          name: _html-rust-report
-          path: rust-coverage
-          if-no-files-found: ignore
-        if: ${{ failure() && steps.combinerustcoverage.outcome == 'failure' }}