diff --git a/tools/coverage/coverage-integrity.mjs b/tools/coverage/coverage-integrity.mjs
new file mode 100644
index 000000000..ca74632c0
--- /dev/null
+++ b/tools/coverage/coverage-integrity.mjs
@@ -0,0 +1,486 @@
+import { createRequire } from 'node:module';
+import { existsSync, readFileSync, readdirSync, statSync } from 'node:fs';
+import path from 'node:path';
+import ts from 'typescript';
+
+const require = createRequire(import.meta.url);
+const { createCoverageMap } = require('istanbul-lib-coverage');
+
+export const COVERAGE_COLLECTION_FAILURE = 'Failed to collect coverage';
+const ANSI_ESCAPE = /\u001b\[[0-?]*[ -/]*[@-~]/g;
+const COVERAGE_METRICS = [
+    'statements',
+    'branches',
+    'functions',
+    'lines',
+];
+
+function toPosix(filePath) {
+    return filePath.split(path.sep).join('/');
+}
+
+function hasDeclareModifier(statement) {
+    const modifiers = ts.canHaveModifiers(statement)
+        ? (ts.getModifiers(statement) ?? [])
+        : [];
+    return modifiers.some(
+        (modifier) => modifier.kind === ts.SyntaxKind.DeclareKeyword
+    );
+}
+
+export function hasRuntimeOwnedStatement(sourceText, fileName = 'source.ts') {
+    const source = ts.createSourceFile(
+        fileName,
+        sourceText,
+        ts.ScriptTarget.Latest,
+        true
+    );
+
+    return source.statements.some((statement) => {
+        if (hasDeclareModifier(statement)) {
+            return false;
+        }
+
+        return !(
+            ts.isImportDeclaration(statement) ||
+            ts.isImportEqualsDeclaration(statement) ||
+            ts.isInterfaceDeclaration(statement) ||
+            ts.isTypeAliasDeclaration(statement) ||
+            ts.isExportDeclaration(statement) ||
+            ts.isEmptyStatement(statement)
+        );
+    });
+}
+
+export function createCoverageOutputScanner(maxCharacters = 4096) {
+    let tail = '';
+    let collectionFailed = false;
+    let ansiState = 'text';
+
+    function stripAnsi(chunk) {
+        const input = String(chunk).replace(ANSI_ESCAPE, '');
+        let output = '';
+
+        for (let index = 0; index < input.length; index += 1) {
+            const character = input[index];
+            const code = character.charCodeAt(0);
+
+            if (ansiState === 'text') {
+                if (code === 0x1b) {
+                    ansiState = 'escape';
+                } else {
+                    output += character;
+                }
+                continue;
+            }
+
+            if (ansiState === 'escape') {
+                if (character === '[') {
+                    ansiState = 'parameters';
+                } else {
+                    output += '\u001b';
+                    ansiState = 'text';
+                    index -= 1;
+                }
+                continue;
+            }
+
+            if (ansiState === 'parameters') {
+                if (code >= 0x30 && code <= 0x3f) {
+                    continue;
+                }
+                if (code >= 0x20 && code <= 0x2f) {
+                    ansiState = 'intermediates';
+                    continue;
+                }
+                if (code >= 0x40 && code <= 0x7e) {
+                    ansiState = 'text';
+                    continue;
+                }
+
+                ansiState = 'text';
+                index -= 1;
+                continue;
+            }
+
+            if (code >= 0x20 && code <= 0x2f) {
+                continue;
+            }
+            if (code >= 0x40 && code <= 0x7e) {
+                ansiState = 'text';
+                continue;
+            }
+
+            ansiState = 'text';
+            index -= 1;
+        }
+
+        return output;
+    }
+
+    return {
+        get collectionFailed() {
+            return collectionFailed;
+        },
+        get tail() {
+            return tail;
+        },
+        push(chunk) {
+            const output = `${tail}${stripAnsi(chunk)}`;
+            if (output.includes(COVERAGE_COLLECTION_FAILURE)) {
+                collectionFailed = true;
+            }
+            tail = output.slice(-maxCharacters);
+        },
+    };
+}
+
+function isExcludedSource(filePath) {
+    const file = toPosix(filePath);
+    return (
+        /\.(spec|test)\.ts$/.test(file) ||
+        file.endsWith('.d.ts') ||
+        file.endsWith('/test-setup.ts') ||
+        file.includes('/test-stubs/') ||
+        /\.generated\./.test(file) ||
+        file.includes('/environments/') ||
+        file.endsWith('/index.ts')
+    );
+}
+
+function runtimeOwningSourceFiles(workspaceRoot, sourceRoot) {
+    const absoluteSourceRoot = path.resolve(workspaceRoot, sourceRoot);
+    const runtimeFiles = [];
+    const directories = [absoluteSourceRoot];
+
+    while (directories.length > 0) {
+        const directory = directories.pop();
+        for (const name of readdirSync(directory)) {
+            const filePath = path.join(directory, name);
+            const stats = statSync(filePath);
+
+            if (stats.isDirectory()) {
+                directories.push(filePath);
+                continue;
+            }
+            if (
+                !stats.isFile() ||
+                !filePath.endsWith('.ts') ||
+                isExcludedSource(filePath)
+            ) {
+                continue;
+            }
+            if (
+                hasRuntimeOwnedStatement(
+                    readFileSync(filePath, 'utf8'),
+                    filePath
+                )
+            ) {
+                runtimeFiles.push(path.resolve(filePath));
+            }
+        }
+    }
+
+    return runtimeFiles.sort();
+}
+
+function isObjectRecord(value) {
+    return value !== null && typeof value === 'object' && !Array.isArray(value);
+}
+
+function indexCoverageFilesByAbsolutePath(coverageMap, workspaceRoot) {
+    const filesByAbsolutePath = new Map();
+    const duplicateAbsolutePaths = new Set();
+
+    for (const reportedPath of coverageMap.files().sort()) {
+        const absolutePath = path.resolve(workspaceRoot, reportedPath);
+        if (filesByAbsolutePath.has(absolutePath)) {
+            duplicateAbsolutePaths.add(absolutePath);
+            continue;
+        }
+        filesByAbsolutePath.set(absolutePath, reportedPath);
+    }
+
+    return {
+        duplicateAbsolutePaths: [...duplicateAbsolutePaths].sort(),
+        filesByAbsolutePath,
+    };
+}
+
+export function validateProjectCoverage({ workspaceRoot, project }) {
+    const reportPath = path.resolve(
+        workspaceRoot,
+        'coverage',
+        project.root,
+        'coverage-final.json'
+    );
+    const relativeReportPath = toPosix(
+        path.relative(workspaceRoot, reportPath)
+    );
+
+    if (!existsSync(reportPath)) {
+        return {
+            errors: [
+                `${project.name} did not produce ${relativeReportPath}.`,
+            ],
+            report: undefined,
+        };
+    }
+
+    let data;
+    try {
+        data = JSON.parse(readFileSync(reportPath, 'utf8'));
+    } catch (error) {
+        return {
+            errors: [
+                `${project.name} coverage report ${relativeReportPath} contains invalid JSON: ${error.message}`,
+            ],
+            report: undefined,
+        };
+    }
+
+    if (
+        !isObjectRecord(data) ||
+        Object.values(data).some((entry) => !isObjectRecord(entry))
+    ) {
+        return {
+            errors: [
+                `${project.name} coverage report ${relativeReportPath} must contain a JSON object mapping source paths to JSON objects.`,
+            ],
+            report: undefined,
+        };
+    }
+
+    let coverageMap;
+    try {
+        coverageMap = createCoverageMap(data);
+        for (const filePath of coverageMap.files()) {
+            coverageMap.fileCoverageFor(filePath).toSummary();
+        }
+    } catch (error) {
+        return {
+            errors: [
+                `${project.name} coverage report ${relativeReportPath} is not valid Istanbul coverage: ${error.message}`,
+            ],
+            report: undefined,
+        };
+    }
+
+    const {
+        duplicateAbsolutePaths,
+        filesByAbsolutePath: reportedFiles,
+    } = indexCoverageFilesByAbsolutePath(coverageMap, workspaceRoot);
+    if (duplicateAbsolutePaths.length > 0) {
+        return {
+            errors: duplicateAbsolutePaths.map(
+                (filePath) =>
+                    `${project.name} coverage report ${relativeReportPath} contains a duplicate entry for ${toPosix(
+                        path.relative(workspaceRoot, filePath)
+                    )} after path normalization.`
+            ),
+            report: undefined,
+        };
+    }
+
+    const errors = [];
+    for (const filePath of runtimeOwningSourceFiles(
+        workspaceRoot,
+        project.sourceRoot
+    )) {
+        const reportedPath = reportedFiles.get(filePath);
+        const relativeSourcePath = toPosix(
+            path.relative(workspaceRoot, filePath)
+        );
+        if (reportedPath === undefined) {
+            errors.push(
+                `${project.name} coverage report is missing runtime-owning source ${relativeSourcePath}.`
+            );
+            continue;
+        }
+
+        const summary = coverageMap
+            .fileCoverageFor(reportedPath)
+            .toSummary()
+            .toJSON();
+        const hasUsableInstrumentation = [
+            summary.statements,
+            summary.functions,
+            summary.branches,
+        ].some((metric) => metric.total > 0);
+        if (!hasUsableInstrumentation) {
+            errors.push(
+                `${project.name} coverage report ${relativeReportPath} has no usable instrumentation for runtime-owning source ${relativeSourcePath}.`
+            );
+        }
+    }
+
+    return {
+        errors,
+        report: {
+            data,
+            path: reportPath,
+            project,
+        },
+    };
+}
+
+export function validateRequiredProjectReports({ projects, workspaceRoot }) {
+    const errors = [];
+    const reports = [];
+
+    for (const project of projects) {
+        const result = validateProjectCoverage({ project, workspaceRoot });
+        errors.push(...result.errors);
+        if (result.report) {
+            reports.push(result.report);
+        }
+    }
+
+    return { errors, reports };
+}
+
+function formatConfigurationValue(value) {
+    return typeof value === 'string' ? JSON.stringify(value) : String(value);
+}
+
+function validateCoverageRatchetConfiguration(ratchet) {
+    const errors = [];
+
+    for (const metric of COVERAGE_METRICS) {
+        const value = ratchet?.merged?.[metric];
+        if (
+            typeof value !== 'number' ||
+            !Number.isFinite(value) ||
+            value < 0 ||
+            value > 100
+        ) {
+            errors.push(
+                `Invalid coverage ratchet merged.${metric}: expected a finite number between 0 and 100, received ${formatConfigurationValue(value)}.`
+            );
+        }
+    }
+
+    const criticalFiles = ratchet?.criticalFiles;
+    if (!Array.isArray(criticalFiles)) {
+        errors.push(
+            `Invalid coverage ratchet criticalFiles: expected an array, received ${formatConfigurationValue(criticalFiles)}.`
+        );
+        return errors;
+    }
+
+    for (const [index, criticalFile] of criticalFiles.entries()) {
+        const criticalPath = criticalFile?.path;
+        const hasValidPath =
+            typeof criticalPath === 'string' &&
+            criticalPath.trim().length > 0;
+        if (!hasValidPath) {
+            errors.push(
+                `Invalid coverage ratchet criticalFiles[${index}].path: expected a non-empty string, received ${formatConfigurationValue(criticalPath)}.`
+            );
+        }
+        const filePath = hasValidPath
+            ? toPosix(criticalPath)
+            : `criticalFiles[${index}]`;
+        const minimumCovered =
+            criticalFile?.statements?.minimumCovered;
+        if (
+            typeof minimumCovered !== 'number' ||
+            !Number.isFinite(minimumCovered) ||
+            !Number.isInteger(minimumCovered) ||
+            minimumCovered < 0
+        ) {
+            errors.push(
+                `Invalid coverage ratchet ${filePath} statements.minimumCovered: expected a non-negative integer, received ${formatConfigurationValue(minimumCovered)}.`
+            );
+        }
+
+        const minimumPercent =
+            criticalFile?.statements?.minimumPercent;
+        if (
+            typeof minimumPercent !== 'number' ||
+            !Number.isFinite(minimumPercent) ||
+            minimumPercent < 0 ||
+            minimumPercent > 100
+        ) {
+            errors.push(
+                `Invalid coverage ratchet ${filePath} statements.minimumPercent: expected a finite number between 0 and 100, received ${formatConfigurationValue(minimumPercent)}.`
+            );
+        }
+    }
+
+    return errors;
+}
+
+export function evaluateCoverageRatchets({
+    coverageData,
+    mergedSummary,
+    ratchet,
+    workspaceRoot,
+}) {
+    const configurationErrors =
+        validateCoverageRatchetConfiguration(ratchet);
+    if (configurationErrors.length > 0) {
+        return configurationErrors;
+    }
+
+    const errors = [];
+
+    for (const metric of COVERAGE_METRICS) {
+        const required = ratchet.merged[metric];
+        const observed = mergedSummary[metric]?.pct;
+        if (!Number.isFinite(observed) || observed < required) {
+            errors.push(
+                `Merged ${metric} coverage regressed: observed ${observed}%, required at least ${required}%.`
+            );
+        }
+    }
+
+    const coverageMap = createCoverageMap(coverageData);
+    const {
+        duplicateAbsolutePaths,
+        filesByAbsolutePath: reportedFiles,
+    } = indexCoverageFilesByAbsolutePath(coverageMap, workspaceRoot);
+    if (duplicateAbsolutePaths.length > 0) {
+        return [
+            ...errors,
+            ...duplicateAbsolutePaths.map(
+                (filePath) =>
+                    `Merged coverage contains a duplicate entry for ${toPosix(
+                        path.relative(workspaceRoot, filePath)
+                    )} after path normalization.`
+            ),
+        ];
+    }
+
+    for (const criticalFile of ratchet.criticalFiles) {
+        const filePath = path.resolve(workspaceRoot, criticalFile.path);
+        const relativePath = toPosix(path.relative(workspaceRoot, filePath));
+        const reportedPath = reportedFiles.get(filePath);
+        if (reportedPath === undefined) {
+            errors.push(
+                `Critical coverage ${relativePath} is missing from merged coverage.`
+            );
+            continue;
+        }
+
+        const statements = coverageMap
+            .fileCoverageFor(reportedPath)
+            .toSummary()
+            .toJSON().statements;
+        const minimumCovered = criticalFile.statements.minimumCovered;
+        if (statements.covered < minimumCovered) {
+            errors.push(
+                `Critical coverage ${relativePath} statements covered regressed: observed ${statements.covered}, required at least ${minimumCovered}.`
+            );
+        }
+
+        const minimumPercent = criticalFile.statements.minimumPercent;
+        if (statements.pct < minimumPercent) {
+            errors.push(
+                `Critical coverage ${relativePath} statements percent regressed: observed ${statements.pct}%, required at least ${minimumPercent}%.`
+            );
+        }
+    }
+
+    return errors;
+}
diff --git a/tools/coverage/coverage-integrity.test.mjs b/tools/coverage/coverage-integrity.test.mjs
new file mode 100644
index 000000000..e1f553d04
--- /dev/null
+++ b/tools/coverage/coverage-integrity.test.mjs
@@ -0,0 +1,739 @@
+import assert from 'node:assert/strict';
+import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import { afterEach, describe, it } from 'node:test';
+
+import {
+    createCoverageOutputScanner,
+    evaluateCoverageRatchets,
+    hasRuntimeOwnedStatement,
+    validateProjectCoverage,
+    validateRequiredProjectReports,
+} from './coverage-integrity.mjs';
+
+const temporaryRoots = [];
+
+afterEach(() => {
+    for (const root of temporaryRoots.splice(0)) {
+        rmSync(root, { recursive: true, force: true });
+    }
+});
+
+function makeProjectFixture({
+    name = 'example',
+    projectRoot = `libs/${name}`,
+    workspaceRoot = undefined,
+} = {}) {
+    const ownsWorkspace = workspaceRoot === undefined;
+    const fixtureRoot =
+        workspaceRoot ??
+        mkdtempSync(path.join(tmpdir(), 'iptvnator-coverage-integrity-'));
+    if (ownsWorkspace) {
+        temporaryRoots.push(fixtureRoot);
+    }
+
+    const sourceRoot = `${projectRoot}/src`;
+    const sourcePath = path.join(fixtureRoot, sourceRoot, 'runtime.ts');
+    const reportPath = path.join(
+        fixtureRoot,
+        'coverage',
+        projectRoot,
+        'coverage-final.json'
+    );
+
+    mkdirSync(path.dirname(sourcePath), { recursive: true });
+    mkdirSync(path.dirname(reportPath), { recursive: true });
+    writeFileSync(sourcePath, 'export const runtime = true;\n');
+
+    const project = {
+        name,
+        root: projectRoot,
+        sourceRoot,
+    };
+
+    return {
+        project,
+        reportPath,
+        sourcePath,
+        workspaceRoot: fixtureRoot,
+    };
+}
+
+function coverageEntry(filePath, hits = [0]) {
+    const statementMap = Object.fromEntries(
+        hits.map((_, index) => [
+            index,
+            {
+                start: { line: index + 1, column: 0 },
+                end: { line: index + 1, column: 28 },
+            },
+        ])
+    );
+    const statementHits = Object.fromEntries(
+        hits.map((hit, index) => [index, hit])
+    );
+
+    return {
+        path: filePath,
+        statementMap,
+        fnMap: {},
+        branchMap: {},
+        s: statementHits,
+        f: {},
+        b: {},
+    };
+}
+
+function functionOnlyCoverageEntry(filePath) {
+    return {
+        path: filePath,
+        statementMap: {},
+        fnMap: {
+            0: {
+                name: 'runtime',
+                decl: {
+                    start: { line: 1, column: 7 },
+                    end: { line: 1, column: 15 },
+                },
+                loc: {
+                    start: { line: 1, column: 7 },
+                    end: { line: 1, column: 28 },
+                },
+                line: 1,
+            },
+        },
+        branchMap: {},
+        s: {},
+        f: { 0: 1 },
+        b: {},
+    };
+}
+
+function writeCompleteReport(fixture, reportKey = fixture.sourcePath) {
+    writeFileSync(
+        fixture.reportPath,
+        JSON.stringify({
+            [reportKey]: coverageEntry(fixture.sourcePath),
+        })
+    );
+}
+
+function fullyCoveredSummary() {
+    return {
+        statements: { covered: 1, total: 1, pct: 100 },
+        branches: { covered: 0, total: 0, pct: 100 },
+        functions: { covered: 0, total: 0, pct: 100 },
+        lines: { covered: 1, total: 1, pct: 100 },
+    };
+}
+
+function ratchetWithCriticalFiles(criticalFiles) {
+    return {
+        merged: {
+            statements: 0,
+            branches: 0,
+            functions: 0,
+            lines: 0,
+        },
+        criticalFiles,
+    };
+}
+
+describe('hasRuntimeOwnedStatement', () => {
+    it('excludes type-only, import-only, and pure re-export source', () => {
+        assert.equal(
+            hasRuntimeOwnedStatement(
+                'import type { Settings } from "./settings";'
+            ),
+            false
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement(
+                'import settings = require("./settings");'
+            ),
+            false
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement('interface Settings { enabled: boolean }'),
+            false
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement('export type Mode = "live" | "vod";'),
+            false
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement('export { value } from "./value";'),
+            false
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement('declare const injected: string;'),
+            false
+        );
+    });
+
+    it('includes emitted declarations and executable statements', () => {
+        assert.equal(
+            hasRuntimeOwnedStatement('export const enabled = true;'),
+            true
+        );
+        assert.equal(
+            hasRuntimeOwnedStatement(
+                'export class RuntimeBoundary { start() {} }'
+            ),
+            true
+        );
+        assert.equal(hasRuntimeOwnedStatement('console.log("runtime");'), true);
+    });
+});
+
+describe('createCoverageOutputScanner', () => {
+    it('detects an ANSI-colored marker split across chunks', () => {
+        const scanner = createCoverageOutputScanner(128);
+
+        scanner.push('\u001b[31mFailed to collect');
+        scanner.push(' coverage from /workspace/effects.ts\u001b[39m');
+
+        assert.equal(scanner.collectionFailed, true);
+    });
+
+    it('detects a marker across a split ANSI escape sequence', () => {
+        const scanner = createCoverageOutputScanner(128);
+
+        scanner.push('Failed to \u001b[3');
+        scanner.push('1mcollect coverage from /workspace/effects.ts');
+
+        assert.equal(scanner.collectionFailed, true);
+        assert.equal(scanner.tail.includes('\u001b'), false);
+    });
+
+    it('keeps only a bounded rolling tail', () => {
+        const scanner = createCoverageOutputScanner(32);
+
+        scanner.push('x'.repeat(256));
+
+        assert.equal(scanner.tail.length, 32);
+        assert.equal(scanner.collectionFailed, false);
+    });
+
+    it('detects the marker before trimming a long chunk', () => {
+        const scanner = createCoverageOutputScanner(32);
+
+        scanner.push(`Failed to collect coverage${'x'.repeat(256)}`);
+
+        assert.equal(scanner.tail.length, 32);
+        assert.equal(scanner.collectionFailed, true);
+    });
+});
+
+describe('validateProjectCoverage', () => {
+    it('accepts a report containing every runtime-owning file', () => {
+        const fixture = makeProjectFixture();
+        const relativeReportKey = path.relative(
+            fixture.workspaceRoot,
+            fixture.sourcePath
+        );
+        writeCompleteReport(fixture, relativeReportKey);
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.deepEqual(result.errors, []);
+        assert.equal(result.report?.project.name, 'example');
+        assert.equal(result.report?.path, fixture.reportPath);
+    });
+
+    it('reports a runtime-owning source omitted from a valid report', () => {
+        const fixture = makeProjectFixture();
+        writeFileSync(fixture.reportPath, '{}');
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.equal(result.errors.length, 1);
+        assert.match(result.errors[0], /example/);
+        assert.match(result.errors[0], /libs\/example\/src\/runtime\.ts/);
+    });
+
+    it('rejects a malformed Istanbul coverage entry', () => {
+        const fixture = makeProjectFixture();
+        writeFileSync(
+            fixture.reportPath,
+            JSON.stringify({ [fixture.sourcePath]: {} })
+        );
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.equal(result.report, undefined);
+        assert.match(
+            result.errors[0],
+            /example.*coverage\/libs\/example\/coverage-final\.json.*valid Istanbul/
+        );
+    });
+
+    it('rejects duplicate report paths after normalization', () => {
+        const fixture = makeProjectFixture();
+        const relativePath = path.relative(
+            fixture.workspaceRoot,
+            fixture.sourcePath
+        );
+        writeFileSync(
+            fixture.reportPath,
+            JSON.stringify({
+                [relativePath]: coverageEntry(relativePath),
+                [fixture.sourcePath]: coverageEntry(fixture.sourcePath),
+            })
+        );
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.equal(result.report, undefined);
+        assert.equal(result.errors.length, 1);
+        assert.match(
+            result.errors[0],
+            /example.*coverage\/libs\/example\/coverage-final\.json.*duplicate.*libs\/example\/src\/runtime\.ts.*normalization/
+        );
+    });
+
+    it('rejects a runtime source without usable instrumentation', () => {
+        const fixture = makeProjectFixture();
+        writeFileSync(
+            fixture.reportPath,
+            JSON.stringify({
+                [fixture.sourcePath]: coverageEntry(fixture.sourcePath, []),
+            })
+        );
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.equal(result.errors.length, 1);
+        assert.match(result.errors[0], /example/);
+        assert.match(result.errors[0], /libs\/example\/src\/runtime\.ts/);
+        assert.match(result.errors[0], /usable instrumentation/);
+    });
+
+    it('accepts function-only instrumentation for a runtime source', () => {
+        const fixture = makeProjectFixture();
+        writeFileSync(
+            fixture.sourcePath,
+            'export function runtime() {}\n'
+        );
+        writeFileSync(
+            fixture.reportPath,
+            JSON.stringify({
+                [fixture.sourcePath]: functionOnlyCoverageEntry(
+                    fixture.sourcePath
+                ),
+            })
+        );
+
+        const result = validateProjectCoverage(fixture);
+
+        assert.deepEqual(result.errors, []);
+        assert.equal(result.report?.project.name, 'example');
+    });
+
+    it('does not require excluded or type-only TypeScript sources', () => {
+        const fixture = makeProjectFixture();
+        const excludedSources = [
+            'feature.spec.ts',
+            'feature.test.ts',
+            'ambient.d.ts',
+            'test-setup.ts',
+            'test-stubs/runtime.ts',
+            'feature.generated.ts',
+            'environments/environment.ts',
+            'index.ts',
+        ];
+        for (const relativePath of excludedSources) {
+            const filePath = path.join(
+                fixture.workspaceRoot,
+                fixture.project.sourceRoot,
+                relativePath
+            );
+            mkdirSync(path.dirname(filePath), { recursive: true });
+            writeFileSync(filePath, 'export const omitted = true;\n');
+        }
+        writeFileSync(
+            path.join(
+                fixture.workspaceRoot,
+                fixture.project.sourceRoot,
+                'contract.ts'
+            ),
+            'export interface Contract { enabled: boolean }\n'
+        );
+        writeCompleteReport(fixture);
+
+        assert.deepEqual(validateProjectCoverage(fixture).errors, []);
+    });
+
+    it('reports missing, malformed, and non-object project reports', () => {
+        const missing = makeProjectFixture();
+        const malformed = makeProjectFixture();
+        const array = makeProjectFixture();
+        const nullValue = makeProjectFixture();
+        writeFileSync(malformed.reportPath, '{ invalid json');
+        writeFileSync(array.reportPath, '[]');
+        writeFileSync(nullValue.reportPath, 'null');
+
+        assert.match(
+            validateProjectCoverage(missing).errors[0],
+            /example.*did not produce.*coverage\/libs\/example\/coverage-final\.json/
+        );
+        assert.match(
+            validateProjectCoverage(malformed).errors[0],
+            /example.*invalid JSON/
+        );
+        assert.match(
+            validateProjectCoverage(array).errors[0],
+            /example.*JSON object/
+        );
+        assert.match(
+            validateProjectCoverage(nullValue).errors[0],
+            /example.*JSON object/
+        );
+    });
+
+    it('requires every configured report and preserves policy order', () => {
+        const first = makeProjectFixture({
+            name: 'first',
+            projectRoot: 'libs/first',
+        });
+        const missing = makeProjectFixture({
+            name: 'missing',
+            projectRoot: 'libs/missing',
+            workspaceRoot: first.workspaceRoot,
+        });
+        const last = makeProjectFixture({
+            name: 'last',
+            projectRoot: 'libs/last',
+            workspaceRoot: first.workspaceRoot,
+        });
+        writeCompleteReport(first);
+        writeCompleteReport(last);
+
+        const result = validateRequiredProjectReports({
+            projects: [last.project, missing.project, first.project],
+            workspaceRoot: first.workspaceRoot,
+        });
+
+        assert.deepEqual(
+            result.reports.map((report) => report.project.name),
+            ['last', 'first']
+        );
+        assert.equal(result.errors.length, 1);
+        assert.match(result.errors[0], /missing/);
+    });
+});
+
+describe('evaluateCoverageRatchets', () => {
+    it('reports all aggregate percentage regressions', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: {
+                statements: { covered: 68, total: 100, pct: 68 },
+                branches: { covered: 57, total: 100, pct: 57 },
+                functions: { covered: 67, total: 100, pct: 67 },
+                lines: { covered: 69, total: 100, pct: 69 },
+            },
+            ratchet: {
+                merged: {
+                    statements: 68.86,
+                    branches: 58.66,
+                    functions: 67.19,
+                    lines: 69.2,
+                },
+                criticalFiles: [],
+            },
+            workspaceRoot: '/workspace',
+        });
+
+        assert.deepEqual(errors, [
+            'Merged statements coverage regressed: observed 68%, required at least 68.86%.',
+            'Merged branches coverage regressed: observed 57%, required at least 58.66%.',
+            'Merged functions coverage regressed: observed 67%, required at least 67.19%.',
+            'Merged lines coverage regressed: observed 69%, required at least 69.2%.',
+        ]);
+    });
+
+    it('rejects missing, non-numeric, and out-of-range aggregate minima', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    branches: '58.66',
+                    functions: -1,
+                    lines: 101,
+                },
+                criticalFiles: [],
+            },
+            workspaceRoot: '/workspace',
+        });
+
+        assert.equal(errors.length, 4);
+        assert.match(errors[0], /merged\.statements.*undefined/);
+        assert.match(errors[1], /merged\.branches.*"58\.66"/);
+        assert.match(errors[2], /merged\.functions.*-1/);
+        assert.match(errors[3], /merged\.lines.*101/);
+    });
+
+    it('accepts an explicitly empty criticalFiles array', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: ratchetWithCriticalFiles([]),
+            workspaceRoot: '/workspace',
+        });
+
+        assert.deepEqual(errors, []);
+    });
+
+    it('requires an explicit criticalFiles array', () => {
+        const merged = ratchetWithCriticalFiles([]).merged;
+        const ratchets = [
+            { merged },
+            { merged, criticalFiles: null },
+        ];
+
+        for (const ratchet of ratchets) {
+            const errors = evaluateCoverageRatchets({
+                coverageData: {},
+                mergedSummary: fullyCoveredSummary(),
+                ratchet,
+                workspaceRoot: '/workspace',
+            });
+
+            assert.equal(errors.length, 1);
+            assert.match(errors[0], /criticalFiles.*array/);
+        }
+    });
+
+    it('rejects a non-array criticalFiles container without throwing', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: ratchetWithCriticalFiles({}),
+            workspaceRoot: '/workspace',
+        });
+
+        assert.equal(errors.length, 1);
+        assert.match(errors[0], /criticalFiles.*array.*object/);
+    });
+
+    it('requires a non-empty string path for every critical file', () => {
+        for (const invalidPath of [undefined, null, 42, '', '   ']) {
+            const errors = evaluateCoverageRatchets({
+                coverageData: {},
+                mergedSummary: fullyCoveredSummary(),
+                ratchet: ratchetWithCriticalFiles([
+                    {
+                        path: invalidPath,
+                        statements: {
+                            minimumCovered: 0,
+                            minimumPercent: 0,
+                        },
+                    },
+                ]),
+                workspaceRoot: '/workspace',
+            });
+
+            assert.equal(errors.length, 1);
+            assert.match(errors[0], /criticalFiles\[0\]\.path/);
+        }
+    });
+
+    it('rejects invalid critical-file statement minima', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    statements: 0,
+                    branches: 0,
+                    functions: 0,
+                    lines: 0,
+                },
+                criticalFiles: [
+                    {
+                        path: 'apps/missing-values.ts',
+                        statements: {},
+                    },
+                    {
+                        path: 'apps/string-values.ts',
+                        statements: {
+                            minimumCovered: '2',
+                            minimumPercent: '75',
+                        },
+                    },
+                    {
+                        path: 'apps/out-of-range.ts',
+                        statements: {
+                            minimumCovered: -1,
+                            minimumPercent: 101,
+                        },
+                    },
+                    {
+                        path: 'apps/fractional.ts',
+                        statements: {
+                            minimumCovered: 1.5,
+                            minimumPercent: 75,
+                        },
+                    },
+                ],
+            },
+            workspaceRoot: '/workspace',
+        });
+
+        assert.equal(errors.length, 7);
+        assert.match(
+            errors[0],
+            /apps\/missing-values\.ts.*minimumCovered.*undefined/
+        );
+        assert.match(
+            errors[1],
+            /apps\/missing-values\.ts.*minimumPercent.*undefined/
+        );
+        assert.match(
+            errors[2],
+            /apps\/string-values\.ts.*minimumCovered.*"2"/
+        );
+        assert.match(
+            errors[3],
+            /apps\/string-values\.ts.*minimumPercent.*"75"/
+        );
+        assert.match(
+            errors[4],
+            /apps\/out-of-range\.ts.*minimumCovered.*-1/
+        );
+        assert.match(
+            errors[5],
+            /apps\/out-of-range\.ts.*minimumPercent.*101/
+        );
+        assert.match(
+            errors[6],
+            /apps\/fractional\.ts.*minimumCovered.*1\.5/
+        );
+    });
+
+    it('requires both covered statements and percentage for a critical file', () => {
+        const workspaceRoot = '/workspace';
+        const filePath = path.join(workspaceRoot, 'apps/runtime.ts');
+        const errors = evaluateCoverageRatchets({
+            coverageData: {
+                [filePath]: coverageEntry(filePath, [1, 0]),
+            },
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    statements: 0,
+                    branches: 0,
+                    functions: 0,
+                    lines: 0,
+                },
+                criticalFiles: [
+                    {
+                        path: 'apps/runtime.ts',
+                        statements: {
+                            minimumCovered: 2,
+                            minimumPercent: 75,
+                        },
+                    },
+                ],
+            },
+            workspaceRoot,
+        });
+
+        assert.deepEqual(errors, [
+            'Critical coverage apps/runtime.ts statements covered regressed: observed 1, required at least 2.',
+            'Critical coverage apps/runtime.ts statements percent regressed: observed 50%, required at least 75%.',
+        ]);
+    });
+
+    it('looks up a relative Istanbul key by its normalized critical path', () => {
+        const workspaceRoot = process.cwd();
+        const relativePath = 'apps/runtime.ts';
+        const errors = evaluateCoverageRatchets({
+            coverageData: {
+                [relativePath]: coverageEntry(relativePath, [1, 1]),
+            },
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    statements: 0,
+                    branches: 0,
+                    functions: 0,
+                    lines: 0,
+                },
+                criticalFiles: [
+                    {
+                        path: relativePath,
+                        statements: {
+                            minimumCovered: 2,
+                            minimumPercent: 100,
+                        },
+                    },
+                ],
+            },
+            workspaceRoot,
+        });
+
+        assert.deepEqual(errors, []);
+    });
+
+    it('rejects duplicate Istanbul keys after path normalization', () => {
+        const workspaceRoot = process.cwd();
+        const relativePath = 'apps/runtime.ts';
+        const absolutePath = path.join(workspaceRoot, relativePath);
+        const errors = evaluateCoverageRatchets({
+            coverageData: {
+                [relativePath]: coverageEntry(relativePath, [1]),
+                [absolutePath]: coverageEntry(absolutePath, [1]),
+            },
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    statements: 0,
+                    branches: 0,
+                    functions: 0,
+                    lines: 0,
+                },
+                criticalFiles: [],
+            },
+            workspaceRoot,
+        });
+
+        assert.equal(errors.length, 1);
+        assert.match(
+            errors[0],
+            /duplicate.*apps\/runtime\.ts.*normalization/
+        );
+    });
+
+    it('reports a critical file missing from merged coverage', () => {
+        const errors = evaluateCoverageRatchets({
+            coverageData: {},
+            mergedSummary: fullyCoveredSummary(),
+            ratchet: {
+                merged: {
+                    statements: 0,
+                    branches: 0,
+                    functions: 0,
+                    lines: 0,
+                },
+                criticalFiles: [
+                    {
+                        path: 'apps/missing.ts',
+                        statements: {
+                            minimumCovered: 1,
+                            minimumPercent: 0,
+                        },
+                    },
+                ],
+            },
+            workspaceRoot: '/workspace',
+        });
+
+        assert.deepEqual(errors, [
+            'Critical coverage apps/missing.ts is missing from merged coverage.',
+        ]);
+    });
+});