diff --git a/.bumpy/package-source-paths.md b/.bumpy/package-source-paths.md
new file mode 100644
index 0000000..a80fc27
--- /dev/null
+++ b/.bumpy/package-source-paths.md
@@ -0,0 +1,5 @@
+---
+'@varlock/bumpy': minor
+---
+
+New per-package `sourcePaths` option: globs (relative to the package dir like other per-package globs, `../` to reach out, `!` to exclude) for sources outside a package's directory. A changed file matching one marks the package as changed, so `bumpy check` requires a bump file for it and `bumpy generate` attributes the commit to it — e.g. a native-binary package built from a separate source package.
diff --git a/docs/configuration.md b/docs/configuration.md
index 6543fd0..91e0984 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -38,7 +38,7 @@ These are two different things, and bumpy treats them differently:
 
 ### Change detection and `package.json` fields
 
-A package is "changed" (and so needs a bump file) when a changed file inside it matches `changedFilePatterns`. `package.json` is a special case: editing it shouldn't always demand a release — a `devDependencies` bump from Dependabot, for example, doesn't affect what consumers install.
+A package is "changed" (and so needs a bump file) when a changed file inside it matches `changedFilePatterns`, or a changed file anywhere in the repo matches its [`sourcePaths`](#sourcepaths--sources-outside-the-package-directory). `package.json` is a special case: editing it shouldn't always demand a release — a `devDependencies` bump from Dependabot, for example, doesn't affect what consumers install.
 
 So when `package.json` is the **only** changed file in a package, bumpy diffs it against the base branch and only flags the package if a field **outside** `ignoredPackageJsonFields` changed. The default ignore list is `["devDependencies"]`, meaning dev-only dependency updates don't require a bump file. Every other field — `dependencies`, `exports`, `bin`, `files`, `description`, `scripts`, etc. — still counts.
 
@@ -176,6 +176,8 @@ Per-package settings can be defined in two places:
 
 `package.json` settings take precedence over global config.
 
+Globs in per-package options (`changedFilePatterns`, `sourcePaths`) are always relative to the package's directory, wherever they're declared.
+
 | Option                     | Type                       | Description                                                                              |
 | -------------------------- | -------------------------- | ---------------------------------------------------------------------------------------- |
 | `managed`                  | `boolean`                  | Opt this package in or out of versioning                                                 |
@@ -187,11 +189,32 @@ Per-package settings can be defined in two places:
 | `skipNpmPublish`           | `boolean`                  | Don't publish to npm (still creates git tags)                                            |
 | `checkPublished`           | `string`                   | Custom command that outputs the currently published version                              |
 | `changedFilePatterns`      | `string[]`                 | Glob patterns for changed-file detection (replaces root setting, not merged)             |
+| `sourcePaths`              | `string[]`                 | Globs for sources outside the package dir (see below)                                    |
 | `dependencyBumpRules`      | `object`                   | Per-package override for dependency propagation rules                                    |
 | `cascadeTo`                | `object`                   | Explicit cascade targets — glob pattern mapped to `{ trigger, bumpAs }`                  |
 | `cascadeFrom`              | `object`                   | Explicit cascade sources — glob pattern mapped to `{ trigger, bumpAs }`                  |
 | `releaseTriggeringDevDeps` | `string[]`                 | devDependencies that affect published output — a change requires a release (see below)   |
 
+### `sourcePaths` — sources outside the package directory
+
+Change detection normally only looks at files inside a package's directory. When a package is built from sources that live elsewhere — e.g. a published native-binary package whose binary is compiled from a separate (private) package — list those sources in `sourcePaths`. A changed file matching one marks the package as changed exactly as if it lived inside it, so `bumpy check` (and the CI check / PR comment) requires a bump file for it and `bumpy generate` attributes the commit to it.
+
+```jsonc
+{
+  "packages": {
+    "@mycli/native-darwin": {
+      // @mycli/native-darwin lives in packages/native/darwin
+      "sourcePaths": ["../../native-src-swift/**", "!../../native-src-swift/**/*.md"],
+    },
+  },
+}
+```
+
+- Globs are relative to the **package's directory**, like every per-package glob (`changedFilePatterns` too), whether declared in the root `packages` map (by name or glob) or in the package's `package.json` `"bumpy"` field. Use `../` to reach sources outside it.
+- Patterns prefixed with `!` exclude — a file counts when it matches any positive pattern and no negated one. Exclusions are package-relative too, so `"!**/*.md"` would only exclude markdown inside the package itself; anchor them to the source dir as above.
+- `sourcePaths` is additive: `changedFilePatterns` still filters only the files inside the package's own directory and does not apply to `sourcePaths` matches.
+- A file can mark several packages as changed (the source package itself, if versioned, and every package listing it).
+
 ### `directBump: false` — packages that only follow
 
 Some packages are derived artifacts of another package and should never be bumped on their own — the typical case is platform-specific binary packages published alongside a core package (the esbuild/napi-rs pattern, where the core references each binary via exact-version `optionalDependencies`).
diff --git a/packages/bumpy/config-schema.json b/packages/bumpy/config-schema.json
index 9c1ac7f..03af2af 100644
--- a/packages/bumpy/config-schema.json
+++ b/packages/bumpy/config-schema.json
@@ -358,6 +358,11 @@
           "description": "Glob patterns to filter which changed files count toward marking this package as changed (overrides root setting)",
           "items": { "type": "string" }
         },
+        "sourcePaths": {
+          "type": "array",
+          "description": "Extra change-detection globs for sources outside this package's directory, relative to the package dir like every per-package glob (use ../ to reach out). A changed file matching one marks this package as changed. Additive to changedFilePatterns (which only applies inside the package). Prefix with ! to exclude.",
+          "items": { "type": "string" }
+        },
         "dependencyBumpRules": {
           "type": "object",
           "description": "Per-package override for dependency propagation rules",
diff --git a/packages/bumpy/src/commands/check.ts b/packages/bumpy/src/commands/check.ts
index c65d2c5..974b23a 100644
--- a/packages/bumpy/src/commands/check.ts
+++ b/packages/bumpy/src/commands/check.ts
@@ -1,7 +1,14 @@
 import { relative, resolve } from 'node:path';
 import picomatch from 'picomatch';
 import { log, colorize } from '../utils/logger.ts';
-import { loadConfig, loadPackageConfig, getBumpyDir, matchGlob, resolveFixedGroups } from '../core/config.ts';
+import {
+  loadConfig,
+  loadPackageConfig,
+  getBumpyDir,
+  matchGlob,
+  makeSourcePathsMatcher,
+  resolveFixedGroups,
+} from '../core/config.ts';
 import { discoverWorkspace } from '../core/workspace.ts';
 import { readBumpFiles, filterBranchBumpFiles } from '../core/bump-file.ts';
 import { getChangedFiles, getFileStatuses, getBaseCompareRef, readFileAtRef } from '../core/git.ts';
@@ -215,7 +222,9 @@ export async function checkCommand(rootDir: string, opts: CheckOptions = {}): Pr
   } else {
     log.dim('Run `bumpy add` to create a bump file, or `bumpy add --empty` if no release is needed.');
   }
-  log.dim('To adjust which files trigger change detection, set `changedFilePatterns` in .bumpy/_config.json.');
+  log.dim(
+    'To adjust which files trigger change detection, set `changedFilePatterns` (or per-package `sourcePaths`) in .bumpy/_config.json.',
+  );
   if (willFail) process.exit(1);
 }
 
@@ -289,10 +298,14 @@ export async function findChangedPackages(
 
   // Build per-package matchers (per-package patterns override root patterns)
   const matchers = new Map<string, picomatch.Matcher>();
+  // `sourcePaths` matchers — repo-root-relative globs for sources outside the package dir
+  const sourceMatchers = new Map<string, (file: string) => boolean>();
   for (const [name, pkg] of packages) {
-    const pkgConfig = await loadPackageConfig(pkg.dir, config, name);
+    const pkgConfig = await loadPackageConfig(pkg.dir, config, name, rootDir);
     const patterns = pkgConfig.changedFilePatterns ?? config.changedFilePatterns;
     matchers.set(name, picomatch(patterns));
+    const sourceMatcher = makeSourcePathsMatcher(pkgConfig.sourcePaths);
+    if (sourceMatcher) sourceMatchers.set(name, sourceMatcher);
   }
 
   const ignoredFields = config.ignoredPackageJsonFields ?? ['devDependencies'];
@@ -306,9 +319,14 @@ export async function findChangedPackages(
     const isRoot = pkgRelDir === '';
     const prefix = `${pkgRelDir}/`;
     const matcher = matchers.get(name)!;
+    const sourceMatcher = sourceMatchers.get(name);
 
     let pkgJsonOnlyTrigger = false;
     for (const file of changedFiles) {
+      if (sourceMatcher?.(file)) {
+        changed.add(name);
+        break;
+      }
       let relToPackage: string;
       if (isRoot) {
         relToPackage = file;
diff --git a/packages/bumpy/src/commands/generate.ts b/packages/bumpy/src/commands/generate.ts
index a509832..993c6bd 100644
--- a/packages/bumpy/src/commands/generate.ts
+++ b/packages/bumpy/src/commands/generate.ts
@@ -4,7 +4,7 @@ import { tryRunArgs } from '../utils/shell.ts';
 import { loadConfig } from '../core/config.ts';
 import { discoverPackages } from '../core/workspace.ts';
 import { writeBumpFile } from '../core/bump-file.ts';
-import { getBumpyDir } from '../core/config.ts';
+import { getBumpyDir, makeSourcePathsMatcher } from '../core/config.ts';
 import { ensureDir } from '../utils/fs.ts';
 import { slugify, randomName } from '../utils/names.ts';
 import { getBaseCompareRef, getBranchCommits, getCurrentBranch, getFilesChangedInCommit } from '../core/git.ts';
@@ -264,19 +264,24 @@ export async function mapCommitToPackages(
   return [...matched];
 }
 
-/** Map file paths to package names based on directory containment */
+/** Map file paths to package names based on directory containment (plus each package's `sourcePaths`) */
 export function mapFilesToPackages(
   files: string[],
   packages: Map<string, WorkspacePackage>,
   rootDir: string,
 ): string[] {
   const matched = new Set<string>();
+  // `pkg.bumpy.sourcePaths` was resolved to repo-root-relative globs by loadPackageConfig
+  const sourceMatchers = new Map(
+    [...packages].map(([name, pkg]) => [name, makeSourcePathsMatcher(pkg.bumpy?.sourcePaths)]),
+  );
   for (const file of files) {
     for (const [name, pkg] of packages) {
       const pkgRelDir = relative(rootDir, pkg.dir);
       // Root package (single-package repo) has an empty relative dir, so every
-      // file belongs to it. Otherwise the file must live under the package dir.
-      if (pkgRelDir === '' || file.startsWith(pkgRelDir + '/')) {
+      // file belongs to it. Otherwise the file must live under the package dir
+      // or match one of its `sourcePaths`.
+      if (pkgRelDir === '' || file.startsWith(pkgRelDir + '/') || sourceMatchers.get(name)?.(file)) {
         matched.add(name);
       }
     }
diff --git a/packages/bumpy/src/core/config.ts b/packages/bumpy/src/core/config.ts
index b09107d..458bc47 100644
--- a/packages/bumpy/src/core/config.ts
+++ b/packages/bumpy/src/core/config.ts
@@ -1,4 +1,5 @@
-import { resolve } from 'node:path';
+import { relative, resolve, sep } from 'node:path';
+import picomatch from 'picomatch';
 import { readJson, readJsonc, exists } from '../utils/fs.ts';
 import { type BumpyConfig, type PackageConfig, DEFAULT_CONFIG, normalizeCascadeConfig } from '../types.ts';
 
@@ -42,6 +43,7 @@ export async function loadPackageConfig(
   pkgDir: string,
   rootConfig: BumpyConfig,
   pkgName: string,
+  rootDir: string,
 ): Promise<PackageConfig> {
   // Start with what's in the root config's packages map
   const rootPkgConfig = findPackageConfig(rootConfig, pkgName);
@@ -74,7 +76,23 @@ export async function loadPackageConfig(
   }
 
   // Merge: root packages map → package.json["bumpy"] (later wins)
-  return mergePackageConfig(rootPkgConfig, pkgJsonConfig);
+  return withRootRelativeSourcePaths(mergePackageConfig(rootPkgConfig, pkgJsonConfig), pkgDir, rootDir);
+}
+
+/**
+ * `sourcePaths` are written relative to the package dir (like every per-package glob,
+ * wherever it's declared) — resolve them to repo-root-relative globs once, so they can be
+ * matched directly against changed files. A leading `!` is preserved.
+ */
+function withRootRelativeSourcePaths(cfg: PackageConfig, pkgDir: string, rootDir: string): PackageConfig {
+  if (!cfg.sourcePaths) return cfg;
+  const sourcePaths = cfg.sourcePaths.map((pattern) => {
+    const negated = pattern.startsWith('!');
+    const body = negated ? pattern.slice(1) : pattern;
+    const rootRelative = relative(rootDir, resolve(pkgDir, body)).split(sep).join('/');
+    return (negated ? '!' : '') + rootRelative;
+  });
+  return { ...cfg, sourcePaths };
 }
 
 /** Find a package config from the root config, supporting glob patterns */
@@ -97,6 +115,21 @@ export function resolveFixedGroups(config: BumpyConfig, packageNames: Iterable<s
   return config.fixed.map((group) => names.filter((name) => group.some((pattern) => matchGlob(name, pattern))));
 }
 
+/**
+ * Build a matcher for a package's resolved `sourcePaths` (repo-root-relative globs, see
+ * `loadPackageConfig`). Patterns
+ * starting with `!` exclude — a file counts when it matches any positive pattern and no
+ * negated one. Returns null when there are no positive patterns.
+ */
+export function makeSourcePathsMatcher(sourcePaths: string[] | undefined): ((file: string) => boolean) | null {
+  const include = (sourcePaths ?? []).filter((p) => !p.startsWith('!'));
+  if (include.length === 0) return null;
+  const exclude = (sourcePaths ?? []).filter((p) => p.startsWith('!')).map((p) => p.slice(1));
+  const isIncluded = picomatch(include);
+  const isExcluded = exclude.length > 0 ? picomatch(exclude) : () => false;
+  return (file) => isIncluded(file) && !isExcluded(file);
+}
+
 /** Simple glob matching for package names (supports * and **) */
 export function matchGlob(name: string, pattern: string): boolean {
   // Exact match
diff --git a/packages/bumpy/src/core/workspace.ts b/packages/bumpy/src/core/workspace.ts
index 623fe88..662bdd4 100644
--- a/packages/bumpy/src/core/workspace.ts
+++ b/packages/bumpy/src/core/workspace.ts
@@ -132,7 +132,7 @@ async function loadWorkspacePackage(
   const name = pkg.name as string;
   if (!name) return null;
 
-  const bumpy = await loadPackageConfig(dir, config, name);
+  const bumpy = await loadPackageConfig(dir, config, name, rootDir);
 
   return {
     name,
diff --git a/packages/bumpy/src/types.ts b/packages/bumpy/src/types.ts
index 09834f8..5b7eb83 100644
--- a/packages/bumpy/src/types.ts
+++ b/packages/bumpy/src/types.ts
@@ -219,6 +219,15 @@ export interface PackageConfig {
   checkPublished?: string;
   /** Glob patterns to filter which changed files count toward marking this package as changed */
   changedFilePatterns?: string[];
+  /**
+   * Extra change-detection globs for sources that live outside this package's directory
+   * (e.g. a binary built from a sibling package). Like every per-package glob, they are
+   * relative to the **package dir** wherever they're declared — use `../` to reach out
+   * (e.g. `"../encryption-binary-swift/**"`). A changed file matching one marks this
+   * package as changed, exactly as if it were inside it. Additive — `changedFilePatterns`
+   * still applies only to files inside the package. Prefix with `!` to exclude.
+   */
+  sourcePaths?: string[];
   dependencyBumpRules?: Partial<Record<DepType, DependencyBumpRule | false>>;
   cascadeTo?: CascadeConfig;
   cascadeFrom?: CascadeConfig;
diff --git a/packages/bumpy/test/core/check.test.ts b/packages/bumpy/test/core/check.test.ts
index 6472f1c..708b03a 100644
--- a/packages/bumpy/test/core/check.test.ts
+++ b/packages/bumpy/test/core/check.test.ts
@@ -132,6 +132,68 @@ describe('findChangedPackages', () => {
     const result = await findChangedPackages(changed, packages, rootDir, makeConfig());
     expect(result).toEqual(['pkg-a']);
   });
+
+  describe('sourcePaths', () => {
+    // sourcePaths are package-relative, so loadPackageConfig reads package.json from disk
+    const tmpRoot = resolve(import.meta.dir, '../../.test-tmp-source-paths');
+    const helperDir = resolve(tmpRoot, 'packages/helpers/darwin');
+    const packages = new Map([
+      ['@x/helper-darwin', makePkg('@x/helper-darwin', '1.0.0', { dir: helperDir })],
+      ['@x/helper-linux', makePkg('@x/helper-linux', '1.0.0', { dir: resolve(tmpRoot, 'packages/helpers/linux') })],
+      ['swift-src', makePkg('swift-src', '1.0.0', { dir: resolve(tmpRoot, 'packages/swift-src') })],
+    ]);
+    const check = (files: string[], config = makeConfig()) =>
+      findChangedPackages(files, packages, tmpRoot, config).then((r) => r.sort());
+
+    afterEach(async () => {
+      await rm(tmpRoot, { recursive: true, force: true });
+    });
+
+    test('a file outside the package matching sourcePaths marks it changed', async () => {
+      const config = makeConfig({ packages: { '@x/helper-darwin': { sourcePaths: ['../../swift-src/**'] } } });
+      expect(await check(['packages/swift-src/Sources/main.swift'], config)).toEqual(['@x/helper-darwin', 'swift-src']);
+    });
+
+    test('a non-matching file does not mark it changed', async () => {
+      const config = makeConfig({ packages: { '@x/helper-darwin': { sourcePaths: ['../../swift-src/**'] } } });
+      expect(await check(['packages/other/index.ts'], config)).toEqual([]);
+    });
+
+    test('globs are package-relative, not repo-root-relative', async () => {
+      const config = makeConfig({ packages: { '@x/helper-darwin': { sourcePaths: ['packages/swift-src/**'] } } });
+      expect(await check(['packages/swift-src/main.swift'], config)).toEqual(['swift-src']);
+    });
+
+    test('negated patterns exclude matches', async () => {
+      const config = makeConfig({
+        packages: { '@x/helper-darwin': { sourcePaths: ['../../swift-src/**', '!../../swift-src/**/*.md'] } },
+      });
+      expect(await check(['packages/swift-src/README.md'], config)).toEqual(['swift-src']);
+      expect(await check(['packages/swift-src/main.swift'], config)).toEqual(['@x/helper-darwin', 'swift-src']);
+    });
+
+    test('works with glob package keys (resolved per package)', async () => {
+      const config = makeConfig({ packages: { '@x/helper-*': { sourcePaths: ['../shared/**'] } } });
+      expect(await check(['packages/helpers/shared/x.c'], config)).toEqual(['@x/helper-darwin', '@x/helper-linux']);
+    });
+
+    test('works when declared in package.json', async () => {
+      await mkdir(helperDir, { recursive: true });
+      await writeFile(
+        resolve(helperDir, 'package.json'),
+        JSON.stringify({ name: '@x/helper-darwin', bumpy: { sourcePaths: ['../../swift-src/**'] } }),
+      );
+      expect(await check(['packages/swift-src/main.swift'])).toEqual(['@x/helper-darwin', 'swift-src']);
+    });
+
+    test('changedFilePatterns does not filter sourcePaths matches', async () => {
+      const config = makeConfig({
+        changedFilePatterns: ['src/**'],
+        packages: { '@x/helper-darwin': { sourcePaths: ['../../swift-src/**'] } },
+      });
+      expect(await check(['packages/swift-src/Package.swift'], config)).toEqual(['@x/helper-darwin']);
+    });
+  });
 });
 
 describe('resolveDirectBumpCoverage', () => {
diff --git a/packages/bumpy/test/core/generate.test.ts b/packages/bumpy/test/core/generate.test.ts
index 251a4a3..31437a0 100644
--- a/packages/bumpy/test/core/generate.test.ts
+++ b/packages/bumpy/test/core/generate.test.ts
@@ -23,6 +23,25 @@ describe('mapFilesToPackages', () => {
     const result = mapFilesToPackages(['packages/pkg-b/src/index.ts'], packages, rootDir);
     expect(result).toEqual(['pkg-b']);
   });
+
+  test('attributes files matching sourcePaths to the package', () => {
+    // pkg.bumpy holds sourcePaths already resolved to repo-root-relative by loadPackageConfig
+    const packages = new Map([
+      [
+        'helper',
+        makePkg('helper', '1.0.0', {
+          dir: `${rootDir}/packages/helper`,
+          bumpy: { sourcePaths: ['packages/swift-src/**', '!**/*.md'] },
+        }),
+      ],
+      ['swift-src', makePkg('swift-src', '1.0.0', { dir: `${rootDir}/packages/swift-src` })],
+    ]);
+    expect(mapFilesToPackages(['packages/swift-src/main.swift'], packages, rootDir).sort()).toEqual([
+      'helper',
+      'swift-src',
+    ]);
+    expect(mapFilesToPackages(['packages/swift-src/README.md'], packages, rootDir)).toEqual(['swift-src']);
+  });
 });
 
 describe('mapCommitToPackages — catalog changes', () => {