feat: govern frontend contract compatibility

config/compatibility/fixtures.json

@@ -0,0 +1,63 @@
+{
+  "schemaVersion": 1,
+  "families": {
+    "api": {
+      "additive": {
+        "before": { "required": ["id"], "properties": { "id": {} } },
+        "after": {
+          "required": ["id"],
+          "properties": { "id": {}, "displayName": {} }
+        }
+      },
+      "breaking": {
+        "before": { "required": ["id"], "properties": { "id": {} } },
+        "after": {
+          "required": ["id", "name"],
+          "properties": { "id": {}, "name": {} }
+        }
+      }
+    },
+    "config": {
+      "additive": {
+        "before": { "required": ["APP_ENV"], "properties": { "APP_ENV": {} } },
+        "after": {
+          "required": ["APP_ENV"],
+          "properties": { "APP_ENV": {}, "OPTIONAL_FLAG": {} }
+        }
+      },
+      "breaking": {
+        "before": { "required": ["APP_ENV"], "properties": { "APP_ENV": {} } },
+        "after": {
+          "required": ["APP_ENV", "NEW_REQUIRED"],
+          "properties": { "APP_ENV": {}, "NEW_REQUIRED": {} }
+        }
+      }
+    },
+    "storage": {
+      "additive": {
+        "before": { "properties": { "theme": {} } },
+        "after": { "properties": { "theme": {}, "contrast": {} } }
+      },
+      "breaking": {
+        "before": { "properties": { "theme": {} } },
+        "after": { "properties": {} }
+      }
+    },
+    "release": {
+      "additive": {
+        "before": { "required": ["buildId"], "properties": { "buildId": {} } },
+        "after": {
+          "required": ["buildId"],
+          "properties": { "buildId": {}, "builtAt": {} }
+        }
+      },
+      "breaking": {
+        "before": { "required": ["buildId"], "properties": { "buildId": {} } },
+        "after": {
+          "required": ["buildId", "assetManifestHash"],
+          "properties": { "buildId": {}, "assetManifestHash": {} }
+        }
+      }
+    }
+  }
+}

docs/contracts/compatibility.md

@@ -0,0 +1,11 @@
+# Contract compatibility and rollback rules
+
+The blocking tuple is `(buildId, configSchemaVersion, apiContractVersion,
+assetManifestHash, releaseId)`. Versions are parsed numerically.
+
+1. additive changes preserve current required fields
+2. breaking changes require a major version bump
+3. persisted cache is discarded unless an explicit tested migration exists
+4. an incompatible config or API contract blocks product mount
+5. rollback restores HTML, assets, runtime config, API compatibility, and
+   release manifest as one coherent set

package.json

@@ -30,7 +30,8 @@
     "generate:supply-chain": "node scripts/generate-supply-chain.mjs",
     "scan:security": "node scripts/security-scan.mjs",
     "check:browser-security": "node scripts/check-browser-security.mjs",
-    "check:registries": "node scripts/check-registries.mjs"
+    "check:registries": "node scripts/check-registries.mjs",
+    "verify:compatibility": "node scripts/check-compatibility.mjs"
   },
   "dependencies": {
     "@tanstack/react-query": "5.101.4",

scripts/check-compatibility.mjs

@@ -0,0 +1,43 @@
+import { mkdir, readFile, writeFile } from "node:fs/promises";
+
+import { classifyObjectSchemaChange } from "../src/application/policies/compatibility.js";
+
+const fixtures = JSON.parse(
+  await readFile("config/compatibility/fixtures.json", "utf8"),
+);
+const results = [];
+
+for (const [family, cases] of Object.entries(fixtures.families)) {
+  for (const expected of ["additive", "breaking"]) {
+    const fixture = cases[expected];
+    const actual = classifyObjectSchemaChange(fixture.before, fixture.after);
+    results.push({ family, expected, actual, passed: actual === expected });
+  }
+}
+
+await mkdir("artifacts/release", { recursive: true });
+await writeFile(
+  "artifacts/release/compatibility.json",
+  `${JSON.stringify(
+    {
+      schemaVersion: 1,
+      generatedAt: new Date().toISOString(),
+      rules: [
+        "additive changes preserve required fields",
+        "breaking changes require version bump and migration, discard, fallback, or rollback",
+        "config and API major versions must match",
+        "incompatible persisted cache is discarded by default",
+        "rollback uses a coherent compatibility tuple",
+      ],
+      results,
+    },
+    null,
+    2,
+  )}\n`,
+);
+
+if (results.some((result) => !result.passed)) {
+  process.stderr.write("Compatibility fixture classification failed.\n");
+  process.exit(1);
+}
+process.stdout.write("Compatibility fixtures: PASS\n");

src/application/policies/compatibility.js

@@ -0,0 +1,102 @@
+export const COMPATIBILITY_TUPLE_FIELDS = Object.freeze([
+  "buildId",
+  "configSchemaVersion",
+  "apiContractVersion",
+  "assetManifestHash",
+  "releaseId",
+]);
+
+/** @param {string} version */
+export function parseNumericVersion(version) {
+  const match = /^(\d+)(?:\.(\d+))?(?:\.(\d+))?$/.exec(version);
+  if (!match) return null;
+  return {
+    major: Number(match[1]),
+    minor: Number(match[2] ?? 0),
+    patch: Number(match[3] ?? 0),
+  };
+}
+
+/** @param {string} supported @param {string} actual */
+export function isVersionCompatible(supported, actual) {
+  const expected = parseNumericVersion(supported);
+  const candidate = parseNumericVersion(actual);
+  if (!expected || !candidate) return false;
+  return (
+    expected.major === candidate.major &&
+    candidate.minor >= expected.minor
+  );
+}
+
+/**
+ * @param {{
+ *   frontend: {
+ *     buildId: string,
+ *     configSchemaVersion: string,
+ *     apiContractVersion: string,
+ *     assetManifestHash: string,
+ *     releaseId: string
+ *   },
+ *   runtime: {
+ *     buildId: string,
+ *     configSchemaVersion: string,
+ *     apiContractVersion: string,
+ *     assetManifestHash: string,
+ *     releaseId: string
+ *   }
+ * }} input
+ */
+export function verifyCompatibilityTuple(input) {
+  const mismatches = [];
+  if (input.frontend.buildId !== input.runtime.buildId) mismatches.push("buildId");
+  if (
+    !isVersionCompatible(
+      input.frontend.configSchemaVersion,
+      input.runtime.configSchemaVersion,
+    )
+  ) {
+    mismatches.push("configSchemaVersion");
+  }
+  if (
+    !isVersionCompatible(
+      input.frontend.apiContractVersion,
+      input.runtime.apiContractVersion,
+    )
+  ) {
+    mismatches.push("apiContractVersion");
+  }
+  if (input.frontend.assetManifestHash !== input.runtime.assetManifestHash) {
+    mismatches.push("assetManifestHash");
+  }
+
+  const releaseWarning =
+    input.frontend.releaseId === input.runtime.releaseId
+      ? null
+      : "releaseId";
+  return Object.freeze({
+    compatible: mismatches.length === 0,
+    mismatches: Object.freeze(mismatches),
+    warnings: Object.freeze(releaseWarning ? [releaseWarning] : []),
+  });
+}
+
+/**
+ * @param {{ required?: string[], properties?: Record<string, unknown> }} before
+ * @param {{ required?: string[], properties?: Record<string, unknown> }} after
+ */
+export function classifyObjectSchemaChange(before, after) {
+  const beforeRequired = new Set(before.required ?? []);
+  const afterRequired = new Set(after.required ?? []);
+  const removedProperties = Object.keys(before.properties ?? {}).filter(
+    (key) => !(key in (after.properties ?? {})),
+  );
+  const addedRequired = [...afterRequired].filter(
+    (key) => !beforeRequired.has(key),
+  );
+  if (removedProperties.length > 0 || addedRequired.length > 0) return "breaking";
+
+  const addedProperties = Object.keys(after.properties ?? {}).filter(
+    (key) => !(key in (before.properties ?? {})),
+  );
+  return addedProperties.length > 0 ? "additive" : "none";
+}

tests/unit/compatibility.test.js

@@ -0,0 +1,77 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  classifyObjectSchemaChange,
+  isVersionCompatible,
+  parseNumericVersion,
+  verifyCompatibilityTuple,
+} from "../../src/application/policies/compatibility.js";
+
+describe("contract compatibility", () => {
+  it("uses numeric version parsing rather than lexical comparison", () => {
+    expect(parseNumericVersion("1.10.0")).toEqual({ major: 1, minor: 10, patch: 0 });
+    expect(isVersionCompatible("1.9", "1.10")).toBe(true);
+    expect(isVersionCompatible("1.9", "2.0")).toBe(false);
+    expect(isVersionCompatible("next", "1.0")).toBe(false);
+  });
+
+  it("distinguishes additive and breaking object changes", () => {
+    const base = { required: ["id"], properties: { id: {} } };
+    expect(
+      classifyObjectSchemaChange(base, {
+        required: ["id"],
+        properties: { id: {}, name: {} },
+      }),
+    ).toBe("additive");
+    expect(
+      classifyObjectSchemaChange(base, {
+        required: ["id", "name"],
+        properties: { id: {}, name: {} },
+      }),
+    ).toBe("breaking");
+  });
+
+  it("treats release ID mismatch as a warning when the blocking tuple is coherent", () => {
+    const frontend = {
+      buildId: "build-a",
+      configSchemaVersion: "1.0",
+      apiContractVersion: "1.0",
+      assetManifestHash: "hash-a",
+      releaseId: "release-a",
+    };
+    expect(
+      verifyCompatibilityTuple({
+        frontend,
+        runtime: { ...frontend, releaseId: "release-b" },
+      }),
+    ).toEqual({
+      compatible: true,
+      mismatches: [],
+      warnings: ["releaseId"],
+    });
+  });
+
+  it("blocks mixed build, config, API, or asset tuples", () => {
+    const frontend = {
+      buildId: "build-a",
+      configSchemaVersion: "1.0",
+      apiContractVersion: "1.0",
+      assetManifestHash: "hash-a",
+      releaseId: "release-a",
+    };
+    expect(
+      verifyCompatibilityTuple({
+        frontend,
+        runtime: {
+          ...frontend,
+          buildId: "build-b",
+          configSchemaVersion: "2.0",
+          assetManifestHash: "hash-b",
+        },
+      }),
+    ).toMatchObject({
+      compatible: false,
+      mismatches: ["buildId", "configSchemaVersion", "assetManifestHash"],
+    });
+  });
+});