diff --git a/CHANGELOG.md b/CHANGELOG.md
index b19cea2..d6b2e5d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,15 @@
 # @focus-mcp/cli
 
+## 2.4.1
+
+### Patch Changes
+
+- 5131bb7: feat(source): implement readPackageVersion() on FilesystemBrickSource
+
+  Adds the optional BrickSource.readPackageVersion() hook (introduced in @focus-mcp/core) so the brick loader can inject the package.json version into the manifest when mcp-brick.json doesn't carry a "version" field. Without this, every brick load throws INVALID_VERSION because the disk manifest and the JS module's exported manifest both lack a SemVer version field.
+
+  Resolution mirrors readManifest(): prefer require.resolve('@focus-mcp/brick-<name>/package.json'), fall back to walking up from the package main entry if /package.json isn't in the exports field, and return undefined when no version can be found (loader keeps its existing INVALID_VERSION behaviour as a last resort).
+
 ## 2.4.0
 
 ### Minor Changes
diff --git a/package.json b/package.json
index 8dedf65..ab25d1a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@focus-mcp/cli",
-    "version": "2.4.0",
+    "version": "2.4.1",
     "private": false,
     "description": "Focus your AI agents on what matters. 68+ bricks, 1 MCP server, modular context — from 200k to 2k tokens. Works with Claude Code, Cursor, Codex.",
     "license": "MIT",
diff --git a/src/source/filesystem-source.test.ts b/src/source/filesystem-source.test.ts
index 25fcb1b..535efdc 100644
--- a/src/source/filesystem-source.test.ts
+++ b/src/source/filesystem-source.test.ts
@@ -369,4 +369,125 @@ describe('FilesystemBrickSource', () => {
         const result = await source.readManifest('x');
         expect(result).toEqual(manifest);
     });
+
+    // ---------- readPackageVersion ----------
+
+    it('readPackageVersion() returns the version from package.json (direct resolve)', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        mockResolve.mockReturnValue('/fake/bricks/brick-a/package.json');
+        mockReadFile.mockResolvedValue(
+            JSON.stringify({ name: '@focus-mcp/brick-a', version: '1.2.3' }),
+        );
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        const result = await source.readPackageVersion('brick-a');
+
+        expect(mockResolve).toHaveBeenCalledWith('@focus-mcp/brick-brick-a/package.json');
+        expect(result).toBe('1.2.3');
+    });
+
+    it('readPackageVersion() falls back to walking up from main when /package.json is not exported', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        // 1st call (/package.json): throws ERR_PACKAGE_PATH_NOT_EXPORTED.
+        // 2nd call (the package main): returns dist entry path.
+        const notExported = Object.assign(new Error('not exported'), {
+            code: 'ERR_PACKAGE_PATH_NOT_EXPORTED',
+        });
+        mockResolve
+            .mockImplementationOnce(() => {
+                throw notExported;
+            })
+            .mockReturnValueOnce('/fake/bricks/brick-a/dist/index.js');
+        mockReadFile.mockResolvedValue(JSON.stringify({ version: '2.0.0' }));
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        const result = await source.readPackageVersion('brick-a');
+
+        expect(result).toBe('2.0.0');
+    });
+
+    it('readPackageVersion() returns undefined when package.json has no version field', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        mockResolve.mockReturnValue('/fake/bricks/brick-a/package.json');
+        mockReadFile.mockResolvedValue(JSON.stringify({ name: '@focus-mcp/brick-a' }));
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        const result = await source.readPackageVersion('brick-a');
+        expect(result).toBeUndefined();
+    });
+
+    it('readPackageVersion() returns undefined when neither direct resolve nor walk-up find a package.json', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        const notFound = Object.assign(new Error('module not found'), { code: 'MODULE_NOT_FOUND' });
+        // 1st call throws, 2nd call returns a path so we enter the walk-up loop.
+        mockResolve
+            .mockImplementationOnce(() => {
+                throw notFound;
+            })
+            .mockReturnValueOnce('/fake/bricks/x/y/z/index.js');
+        // Every readFile during walk-up throws (no package.json found).
+        mockReadFile.mockRejectedValue(new Error('ENOENT'));
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        const result = await source.readPackageVersion('brick-a');
+        expect(result).toBeUndefined();
+    });
+
+    it('readPackageVersion() returns undefined when the package itself is not installed', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        // Both the /package.json resolve AND the main-entry resolve throw
+        // MODULE_NOT_FOUND — the package is genuinely absent. JSDoc says
+        // we should return undefined rather than propagating.
+        const notFound = Object.assign(new Error('module not found'), { code: 'MODULE_NOT_FOUND' });
+        mockResolve.mockImplementation(() => {
+            throw notFound;
+        });
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        const result = await source.readPackageVersion('brick-a');
+        expect(result).toBeUndefined();
+    });
+
+    it('readPackageVersion() throws if resolved path escapes bricksDir (symlink attack)', async () => {
+        const { FilesystemBrickSource } = await import('./filesystem-source.ts');
+
+        // Resolver returns a path outside bricksDir — assertWithinBricksDir
+        // must throw to prevent symlink/alias escapes (same protection as
+        // readManifest / loadModule).
+        mockResolve.mockReturnValue('/etc/passwd/package.json');
+        mockRealpathSync.mockImplementation((p: string) => p);
+        mockReadFile.mockResolvedValue(JSON.stringify({ version: '1.0.0' }));
+
+        const source = new FilesystemBrickSource({
+            centerJson: { bricks: {} },
+            bricksDir: '/fake/bricks',
+        });
+
+        await expect(source.readPackageVersion('brick-a')).rejects.toThrow(/escapes bricksDir/);
+    });
 });
diff --git a/src/source/filesystem-source.ts b/src/source/filesystem-source.ts
index 03d612e..a5fbc79 100644
--- a/src/source/filesystem-source.ts
+++ b/src/source/filesystem-source.ts
@@ -113,4 +113,85 @@ export class FilesystemBrickSource implements BrickSource {
         const cacheBuster = `?t=${Date.now()}`;
         return import(`${pathToFileURL(entry).href}${cacheBuster}`);
     }
+
+    /**
+     * Read the brick's package.json `version` field so the core loader can
+     * inject it into the manifest when `mcp-brick.json` itself doesn't carry
+     * a `version` (the current shape of all `@focus-mcp/brick-*` manifests).
+     *
+     * Returns `undefined` if the package.json can't be found or is missing
+     * a string `version` field — the loader is free to fall back to its
+     * existing INVALID_VERSION behaviour in that case.
+     */
+    async readPackageVersion(name: string): Promise<string | undefined> {
+        const brickName = safeBrickName(name);
+        const require = createRequire(pathToFileURL(`${this.#bricksDir}/`).href);
+        const pkgPath = await resolvePackageJsonPath(require, brickName);
+        if (pkgPath === undefined) return undefined;
+        assertWithinBricksDir(pkgPath, this.#bricksDir);
+        const raw = await readFile(pkgPath, 'utf-8');
+        return extractVersion(raw);
+    }
+}
+
+/**
+ * Resolve the path to `@focus-mcp/brick-<name>/package.json`, with a fallback
+ * walk-up from the package main entry. Returns `undefined` only when the
+ * package is genuinely absent or has no package.json reachable from its main.
+ */
+async function resolvePackageJsonPath(
+    require: NodeJS.Require,
+    brickName: string,
+): Promise<string | undefined> {
+    try {
+        // Preferred: `./package.json` is unconditionally resolvable since
+        // Node 14, even when an `exports` field restricts other paths.
+        return require.resolve(`@focus-mcp/brick-${brickName}/package.json`);
+    } catch (err: unknown) {
+        const code = (err as NodeJS.ErrnoException).code;
+        if (code !== 'ERR_PACKAGE_PATH_NOT_EXPORTED' && code !== 'MODULE_NOT_FOUND') {
+            throw err;
+        }
+    }
+    // Fallback: walk up from the package main entry.
+    const pkgMain = resolvePackageMain(require, brickName);
+    if (pkgMain === undefined) return undefined;
+    return await walkUpForPackageJson(dirname(pkgMain));
+}
+
+function resolvePackageMain(require: NodeJS.Require, brickName: string): string | undefined {
+    try {
+        return require.resolve(`@focus-mcp/brick-${brickName}`);
+    } catch (err: unknown) {
+        if ((err as NodeJS.ErrnoException).code === 'MODULE_NOT_FOUND') return undefined;
+        throw err;
+    }
+}
+
+async function walkUpForPackageJson(startDir: string): Promise<string | undefined> {
+    let dir = startDir;
+    while (true) {
+        const candidate = join(dir, 'package.json');
+        try {
+            await readFile(candidate, 'utf-8');
+            return candidate;
+        } catch {
+            const parent = dirname(dir);
+            if (parent === dir) return undefined;
+            dir = parent;
+        }
+    }
+}
+
+function extractVersion(raw: string): string | undefined {
+    const parsed: unknown = JSON.parse(raw);
+    if (
+        parsed !== null &&
+        typeof parsed === 'object' &&
+        'version' in parsed &&
+        typeof (parsed as { version: unknown }).version === 'string'
+    ) {
+        return (parsed as { version: string }).version;
+    }
+    return undefined;
 }