diff --git a/.github/scripts/check-breaking.cjs b/.github/scripts/check-breaking.cjs
new file mode 100644
index 000000000..5d90b958f
--- /dev/null
+++ b/.github/scripts/check-breaking.cjs
@@ -0,0 +1,326 @@
+const fs = require("node:fs");
+const os = require("node:os");
+const path = require("node:path");
+
+const COMMENT_MARKER = "<!-- cargo-semver-checks: breaking-change -->";
+const LABEL = "breaking change";
+const MAX_REPORT_LENGTH = 50_000;
+const REMOVED_PACKAGE_REPORT = "Package removed from the current workspace.";
+
+const CHECKED_PACKAGES = new Set(["compio", "compio-driver"]);
+
+function stableFeatureNames(features) {
+  const unstable = new Set();
+  const visit = (name) => {
+    if (unstable.has(name) || !Object.hasOwn(features, name)) {
+      return;
+    }
+    unstable.add(name);
+    for (const member of features[name]) {
+      visit(member);
+    }
+  };
+  visit("nightly");
+
+  let changed;
+  do {
+    changed = false;
+    for (const [name, members] of Object.entries(features)) {
+      if (
+        !unstable.has(name) &&
+        members.some((member) => unstable.has(member))
+      ) {
+        unstable.add(name);
+        changed = true;
+      }
+    }
+  } while (changed);
+
+  return Object.keys(features)
+    .filter((name) => !unstable.has(name))
+    .sort();
+}
+
+function workspacePackages(metadata) {
+  const members = new Set(metadata.workspace_members);
+  return metadata.packages
+    .filter(
+      ({ id, name }) => members.has(id) && CHECKED_PACKAGES.has(name),
+    )
+    .map(({ features = {}, name }) => ({
+      name,
+      stableFeatures: stableFeatureNames(features),
+    }))
+    .sort(({ name: left }, { name: right }) => left.localeCompare(right));
+}
+
+function classifyPackages(currentPackages, baselinePackages) {
+  const current = new Map(
+    currentPackages.map((package) => [package.name, package]),
+  );
+  const baseline = new Set(baselinePackages.map(({ name }) => name));
+  return {
+    common: [...current.values()].filter(({ name }) => baseline.has(name)),
+    removed: [...baseline].filter((name) => !current.has(name)).sort(),
+  };
+}
+
+async function readWorkspacePackages(exec, manifestPath) {
+  const result = await exec.getExecOutput(
+    "cargo",
+    [
+      "metadata",
+      "--manifest-path",
+      manifestPath,
+      "--no-deps",
+      "--format-version",
+      "1",
+    ],
+    { silent: true },
+  );
+  return workspacePackages(JSON.parse(result.stdout));
+}
+
+async function checkPackage({
+  baselineRev,
+  core,
+  exec,
+  packageName,
+  stableFeatures,
+}) {
+  core.startGroup(`Checking ${packageName}`);
+  const args = [
+    "semver-checks",
+    "check-release",
+    "--package",
+    packageName,
+    "--baseline-rev",
+    baselineRev,
+    "--release-type",
+    "minor",
+    "--only-explicit-features",
+  ];
+  if (stableFeatures.length > 0) {
+    args.push("--features", stableFeatures.join(","));
+  }
+
+  let result;
+  try {
+    result = await exec.getExecOutput("cargo", args, {
+      ignoreReturnCode: true,
+    });
+  } finally {
+    core.endGroup();
+  }
+
+  if (result.exitCode === 0) {
+    return null;
+  }
+  if (result.exitCode === 100) {
+    const output = [result.stdout, result.stderr]
+      .map((value) => value.trim())
+      .filter(Boolean)
+      .join("\n");
+    return [
+      `$ cargo ${args.join(" ")}`,
+      output || "cargo-semver-checks reported a breaking public API change.",
+    ].join("\n");
+  }
+  throw new Error(
+    `cargo-semver-checks could not check ${packageName} (exit code ${result.exitCode}).`,
+  );
+}
+
+async function check({
+  baselineRev = process.env.BASELINE_REV,
+  core,
+  cwd = process.cwd(),
+  exec,
+  reportPath = process.env.BREAKING_REPORT_PATH,
+}) {
+  if (!baselineRev) {
+    throw new Error("BASELINE_REV is required.");
+  }
+
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "compio-semver-"));
+  const baselineDir = path.join(tempDir, "baseline");
+  let worktreeAdded = false;
+
+  try {
+    await exec.exec("git", ["worktree", "add", "--detach", baselineDir, baselineRev]);
+    worktreeAdded = true;
+
+    const currentPackages = await readWorkspacePackages(
+      exec,
+      path.join(cwd, "Cargo.toml"),
+    );
+    const baselinePackages = await readWorkspacePackages(
+      exec,
+      path.join(baselineDir, "Cargo.toml"),
+    );
+    const { common, removed } = classifyPackages(
+      currentPackages,
+      baselinePackages,
+    );
+    const breaking = [...removed];
+    const reports = new Map(
+      removed.map((name) => [name, REMOVED_PACKAGE_REPORT]),
+    );
+
+    if (removed.length > 0) {
+      core.info(`Removed workspace crates: ${removed.join(", ")}`);
+    }
+
+    for (const { name, stableFeatures } of common) {
+      const packageReport = await checkPackage({
+        baselineRev,
+        core,
+        exec,
+        packageName: name,
+        stableFeatures,
+      });
+      if (packageReport !== null) {
+        breaking.push(name);
+        reports.set(name, packageReport);
+      }
+    }
+
+    breaking.sort();
+    const report = breaking
+      .map((name) => `[${name}]\n${reports.get(name)}`)
+      .join("\n\n");
+    core.setOutput("breaking", breaking.length > 0);
+    core.setOutput("crates", breaking.join("\n"));
+    if (reportPath) {
+      fs.mkdirSync(path.dirname(reportPath), { recursive: true });
+      fs.writeFileSync(
+        reportPath,
+        `${JSON.stringify({ crates: breaking, report })}\n`,
+      );
+    }
+    return breaking;
+  } finally {
+    if (worktreeAdded) {
+      await exec.exec("git", ["worktree", "remove", "--force", baselineDir], {
+        ignoreReturnCode: true,
+        silent: true,
+      });
+    }
+    fs.rmSync(tempDir, { force: true, recursive: true });
+  }
+}
+
+function escapeHtml(value) {
+  return value
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;");
+}
+
+function formatDiagnostics(diagnostics) {
+  const escaped = escapeHtml(diagnostics.trim());
+  const suffix = "\n\n... report truncated to fit the GitHub comment limit.";
+  return escaped.length <= MAX_REPORT_LENGTH
+    ? escaped
+    : `${escaped.slice(0, MAX_REPORT_LENGTH - suffix.length)}${suffix}`;
+}
+
+function buildReportBody({ crates, diagnostics }) {
+  const crateList = crates.map((name) => `- \`${name}\``).join("\n");
+  return `${COMMENT_MARKER}
+### Breaking API change detected
+
+\`cargo-semver-checks\` found breaking public API changes in these crates:
+
+${crateList}
+
+Add \`!\` before the colon in the PR title, for example \`feat!: ...\` or \`feat(runtime)!: ...\`. In the PR description, explain the affected API, the impact on users, and the migration path.
+
+<details>
+<summary>cargo-semver-checks report</summary>
+
+<pre><code>${formatDiagnostics(diagnostics)}</code></pre>
+</details>`;
+}
+
+function readReport(reportPath) {
+  return JSON.parse(fs.readFileSync(reportPath, "utf8"));
+}
+
+async function report({
+  crates,
+  diagnostics,
+  github,
+  context,
+  issueNumber = context.issue?.number,
+}) {
+  if (crates.length === 0) {
+    throw new Error("At least one breaking crate is required.");
+  }
+  if (!issueNumber) {
+    throw new Error("A pull request number is required.");
+  }
+  if (typeof diagnostics !== "string" || !diagnostics.trim()) {
+    throw new Error("Breaking change diagnostics are required.");
+  }
+
+  const body = buildReportBody({ crates, diagnostics });
+
+  await github.rest.issues.addLabels({
+    ...context.repo,
+    issue_number: issueNumber,
+    labels: [LABEL],
+  });
+
+  const comments = await github.paginate(github.rest.issues.listComments, {
+    ...context.repo,
+    issue_number: issueNumber,
+    per_page: 100,
+  });
+  const existing = comments.find(
+    (comment) =>
+      comment.user?.type === "Bot" && comment.body?.includes(COMMENT_MARKER),
+  );
+
+  if (existing) {
+    await github.rest.issues.updateComment({
+      ...context.repo,
+      comment_id: existing.id,
+      body,
+    });
+  } else {
+    await github.rest.issues.createComment({
+      ...context.repo,
+      issue_number: issueNumber,
+      body,
+    });
+  }
+}
+
+async function reportFromFile({ core, reportPath, ...options }) {
+  const { crates, report: diagnostics } = readReport(reportPath);
+  if (!Array.isArray(crates)) {
+    throw new Error("The breaking change report has no crate list.");
+  }
+  if (crates.length === 0) {
+    core.info("No breaking public API changes detected.");
+    return false;
+  }
+  if (typeof diagnostics !== "string" || !diagnostics.trim()) {
+    throw new Error("The breaking change report has no diagnostics.");
+  }
+
+  await report({ crates, diagnostics, ...options });
+  return true;
+}
+
+module.exports = {
+  buildReportBody,
+  check,
+  classifyPackages,
+  readReport,
+  report,
+  reportFromFile,
+  stableFeatureNames,
+  workspacePackages,
+};
diff --git a/.github/scripts/check-breaking.test.cjs b/.github/scripts/check-breaking.test.cjs
new file mode 100644
index 000000000..de3b7c8b2
--- /dev/null
+++ b/.github/scripts/check-breaking.test.cjs
@@ -0,0 +1,246 @@
+const test = require("node:test");
+const assert = require("node:assert/strict");
+const fs = require("node:fs");
+const os = require("node:os");
+const path = require("node:path");
+
+const { check, reportFromFile } = require("./check-breaking.cjs");
+
+function metadata(packages) {
+  const entries = packages.map((package) =>
+    typeof package === "string" ? { name: package, features: {} } : package,
+  );
+  const records = entries.map(({ features, name }) => ({
+    features,
+    id: `${name} 0.1.0`,
+    name,
+  }));
+  return {
+    packages: records,
+    workspace_members: records.map(({ id }) => id),
+  };
+}
+
+function mockCore() {
+  return {
+    groups: [],
+    info() {},
+    outputs: {},
+    endGroup() {},
+    setOutput(name, value) {
+      this.outputs[name] = value;
+    },
+    startGroup(name) {
+      this.groups.push(name);
+    },
+  };
+}
+
+function mockExec({
+  baseline,
+  current,
+  outputs = {},
+  semverArgs = [],
+  statuses = {},
+}) {
+  let metadataCall = 0;
+  return {
+    async exec() {
+      return 0;
+    },
+    async getExecOutput(tool, args) {
+      assert.equal(tool, "cargo");
+      if (args[0] === "metadata") {
+        const value = metadataCall++ === 0 ? current : baseline;
+        return { exitCode: 0, stderr: "", stdout: JSON.stringify(metadata(value)) };
+      }
+
+      semverArgs.push(args);
+      const packageName = args[args.indexOf("--package") + 1];
+      return {
+        exitCode: statuses[packageName] ?? 0,
+        stderr: "",
+        stdout: outputs[packageName] ?? "",
+      };
+    },
+  };
+}
+
+test("reports incompatible and removed checked crates", async () => {
+  const core = mockCore();
+  const exec = mockExec({
+    baseline: ["compio", "compio-driver", "compio-fs"],
+    current: ["compio", "compio-net"],
+    statuses: { compio: 100 },
+    outputs: { compio: "compio compatibility report" },
+  });
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "compio-semver-test-"));
+  const reportPath = path.join(tempDir, "report.json");
+  try {
+    const breaking = await check({
+      baselineRev: "base",
+      core,
+      exec,
+      reportPath,
+    });
+
+    assert.deepEqual(breaking, ["compio", "compio-driver"]);
+    assert.deepEqual(core.outputs, {
+      breaking: true,
+      crates: "compio\ncompio-driver",
+    });
+    const report = JSON.parse(fs.readFileSync(reportPath, "utf8"));
+    assert.deepEqual(report.crates, ["compio", "compio-driver"]);
+    assert.match(report.report, /\[compio\]/);
+    assert.match(report.report, /compio compatibility report/);
+    assert.match(report.report, /\[compio-driver\]/);
+    assert.match(report.report, /removed from the current workspace/);
+  } finally {
+    fs.rmSync(tempDir, { force: true, recursive: true });
+  }
+});
+
+test("reports a compatible workspace", async () => {
+  const core = mockCore();
+  const exec = mockExec({
+    baseline: ["compio", "compio-driver", "compio-runtime"],
+    current: ["compio", "compio-driver", "compio-runtime"],
+  });
+
+  const breaking = await check({ baselineRev: "base", core, exec });
+
+  assert.deepEqual(breaking, []);
+  assert.deepEqual(core.outputs, { breaking: false, crates: "" });
+});
+
+test("checks only compio and compio-driver", async () => {
+  const core = mockCore();
+  const semverArgs = [];
+  const packages = ["compio", "compio-driver", "compio-macros", "compio-net"];
+  const exec = mockExec({
+    baseline: packages,
+    current: packages,
+    semverArgs,
+  });
+
+  await check({ baselineRev: "base", core, exec });
+
+  assert.deepEqual(
+    semverArgs.map((args) => args[args.indexOf("--package") + 1]),
+    ["compio", "compio-driver"],
+  );
+});
+
+test("checks one package with stable features only", async () => {
+  const core = mockCore();
+  const semverArgs = [];
+  const packages = [
+    {
+      features: {
+        all: ["bytes"],
+        bytes: ["dep:bytes"],
+        default: ["bytes"],
+        nightly: ["read_buf"],
+        "nightly-all": ["nightly"],
+        read_buf: [],
+      },
+      name: "compio-driver",
+    },
+  ];
+  const exec = mockExec({
+    baseline: packages,
+    current: packages,
+    semverArgs,
+  });
+
+  await check({ baselineRev: "base", core, exec });
+
+  assert.deepEqual(semverArgs, [
+    [
+      "semver-checks",
+      "check-release",
+      "--package",
+      "compio-driver",
+      "--baseline-rev",
+      "base",
+      "--release-type",
+      "minor",
+      "--only-explicit-features",
+      "--features",
+      "all,bytes,default",
+    ],
+  ]);
+});
+
+test("fails when cargo-semver-checks cannot complete", async () => {
+  const core = mockCore();
+  const exec = mockExec({
+    baseline: ["compio"],
+    current: ["compio"],
+    statuses: { compio: 101 },
+  });
+
+  await assert.rejects(
+    check({ baselineRev: "base", core, exec }),
+    /could not check compio \(exit code 101\)/,
+  );
+});
+
+test("labels the PR and lists each breaking crate", async () => {
+  const calls = [];
+  const github = {
+    paginate: async () => [],
+    rest: {
+      issues: {
+        addLabels: async (args) => calls.push(["addLabels", args]),
+        createComment: async (args) => calls.push(["createComment", args]),
+        listComments: async () => {},
+      },
+    },
+  };
+  const context = {
+    issue: { number: 42 },
+    repo: { owner: "compio-rs", repo: "compio" },
+    runId: 123,
+  };
+
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "compio-report-test-"));
+  const reportPath = path.join(tempDir, "report.json");
+  fs.writeFileSync(
+    reportPath,
+    JSON.stringify({
+      crates: ["compio-runtime", "compio-net"],
+      report:
+        "[compio-runtime]\n<breaking> runtime API\n\n[compio-net]\nremoved API",
+    }),
+  );
+  try {
+    assert.equal(
+      await reportFromFile({
+        core: mockCore(),
+        github,
+        context,
+        issueNumber: 42,
+        reportPath,
+      }),
+      true,
+    );
+  } finally {
+    fs.rmSync(tempDir, { force: true, recursive: true });
+  }
+
+  const comment = calls.find(([name]) => name === "createComment")[1];
+  assert.match(comment.body, /- `compio-runtime`/);
+  assert.match(comment.body, /- `compio-net`/);
+  assert.match(comment.body, /`feat!: \.\.\.`/);
+  assert.match(comment.body, /migration path/);
+  assert.match(comment.body, /<details>/);
+  assert.match(comment.body, /<summary>cargo-semver-checks report<\/summary>/);
+  assert.match(comment.body, /<pre><code>/);
+  assert.match(comment.body, /&lt;breaking&gt; runtime API/);
+  assert.match(comment.body, /<\/code><\/pre>/);
+  assert.doesNotMatch(comment.body, /workflow run|actions\/runs/);
+  assert.ok(calls.some(([name]) => name === "addLabels"));
+  assert.ok(!calls.some(([name]) => name === "getLabel"));
+  assert.ok(!calls.some(([name]) => name === "createLabel"));
+});
diff --git a/.github/workflows/ci_check_breaking.yml b/.github/workflows/ci_check_breaking.yml
new file mode 100644
index 000000000..8bdea42aa
--- /dev/null
+++ b/.github/workflows/ci_check_breaking.yml
@@ -0,0 +1,42 @@
+name: Check Breaking Changes
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  check-breaking:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+      - name: Setup Rust Toolchain
+        run: rustup default stable
+      - uses: taiki-e/install-action@cargo-semver-checks
+      - name: Check Public API Compatibility
+        id: semver
+        uses: actions/github-script@v8
+        env:
+          BASELINE_REV: ${{ github.event.pull_request.base.sha }}
+          BREAKING_REPORT_PATH: ${{ runner.temp }}/breaking-change/report.json
+          CARGO_INCREMENTAL: 0
+        with:
+          script: |
+            const { check } = require("./.github/scripts/check-breaking.cjs");
+            await check({ core, exec });
+      - name: Save Breaking Change Report
+        uses: actions/upload-artifact@v7
+        with:
+          name: breaking-change-report
+          path: ${{ runner.temp }}/breaking-change/report.json
+          if-no-files-found: error
+          retention-days: 1
+
diff --git a/.github/workflows/ci_report_breaking.yml b/.github/workflows/ci_report_breaking.yml
new file mode 100644
index 000000000..f5c653293
--- /dev/null
+++ b/.github/workflows/ci_report_breaking.yml
@@ -0,0 +1,48 @@
+name: Report Breaking Changes
+
+on:
+  workflow_run:
+    workflows: [Check Breaking Changes]
+    types: [completed]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.workflow_run.id }}
+  cancel-in-progress: true
+
+jobs:
+  report-breaking:
+    if: ${{ github.event.workflow_run.conclusion == 'success' && github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.pull_requests[0].number }}
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          ref: ${{ github.event.repository.default_branch }}
+          persist-credentials: false
+      - name: Load Breaking Change Report
+        uses: actions/download-artifact@v8
+        with:
+          name: breaking-change-report
+          path: ${{ runner.temp }}/breaking-change
+          repository: ${{ github.repository }}
+          run-id: ${{ github.event.workflow_run.id }}
+          github-token: ${{ github.token }}
+      - name: Label PR and Report Breaking Changes
+        uses: actions/github-script@v8
+        env:
+          BREAKING_REPORT_PATH: ${{ runner.temp }}/breaking-change/report.json
+          PR_NUMBER: ${{ github.event.workflow_run.pull_requests[0].number }}
+        with:
+          script: |
+            const { reportFromFile } = require("./.github/scripts/check-breaking.cjs");
+            await reportFromFile({
+              core,
+              github,
+              context,
+              issueNumber: Number(process.env.PR_NUMBER),
+              reportPath: process.env.BREAKING_REPORT_PATH,
+            });