diff --git a/docs/feature-mapping.md b/docs/feature-mapping.md
index 1f08194..dab0364 100644
--- a/docs/feature-mapping.md
+++ b/docs/feature-mapping.md
@@ -53,7 +53,9 @@ Supported deterministic mappers today:
   groups including Hilt, Dagger, Koin, and Metro
 - Ruby project metadata, executables, source groups, RSpec/Minitest suites,
   Rails configs, routes, views, assets, and database files
-- Rust Cargo commands, libraries, workspace crates, and integration tests
+- Rust Cargo commands, libraries, workspace crates, integration tests, and
+  bounded source groups under each package `src/` (entrypoint `lib.rs` /
+  `main.rs` / bin files stay on command and library features)
 - C/C++/CUDA standalone `main()` files, CMake targets, autotools targets, and
   bounded loose source groups
 - C#/.NET projects from `.sln`, `.slnx`, `.csproj`, `.fsproj`, and `.vbproj`,
diff --git a/src/mapper.test.ts b/src/mapper.test.ts
index e321017..1be127d 100644
--- a/src/mapper.test.ts
+++ b/src/mapper.test.ts
@@ -11030,6 +11030,120 @@ let package = Package(name: "HybridApp", targets: [.target(name: "HybridApp")])
     expect(integrationTests).toHaveLength(8);
   });
 
+  it("maps Rust source groups for crate modules without re-owning entrypoints", async () => {
+    const root = await fixtureRoot("clawpatch-rust-source-groups-");
+    await writeFixture(
+      root,
+      "Cargo.toml",
+      '[workspace]\nmembers = ["crates/core", "crates/cli"]\n',
+    );
+    await writeFixture(root, "crates/core/Cargo.toml", '[package]\nname = "core"\n');
+    await writeFixture(root, "crates/core/src/lib.rs", "pub mod auth;\npub mod storage;\n");
+    await writeFixture(root, "crates/core/src/auth/mod.rs", "pub fn login() {}\n");
+    await writeFixture(root, "crates/core/src/auth/token.rs", "pub fn mint() {}\n");
+    await writeFixture(root, "crates/core/src/storage/mod.rs", "pub fn open() {}\n");
+    await writeFixture(root, "crates/core/src/storage/db.rs", "pub fn connect() {}\n");
+    await writeFixture(root, "crates/cli/Cargo.toml", '[package]\nname = "cli"\n');
+    await writeFixture(root, "crates/cli/src/main.rs", "fn main() {}\n");
+    await writeFixture(root, "crates/cli/src/commands.rs", "pub fn run() {}\n");
+    await writeFixture(root, "crates/cli/src/bin/worker.rs", "fn main() {}\n");
+    await writeFixture(root, "crates/cli/src/bin/admin/main.rs", "fn main() {}\n");
+    await writeFixture(root, "crates/cli/src/bin/admin/helpers.rs", "pub fn prep() {}\n");
+
+    const project = await detectProject(root);
+    const result = await mapFeatures(root, project, []);
+    const sourceGroups = result.features.filter(
+      (feature) => feature.source === "rust-source-group",
+    );
+    const owned = sourceGroups.flatMap((feature) => feature.ownedFiles.map((file) => file.path));
+    const titles = sourceGroups.map((feature) => feature.title);
+
+    expect(sourceGroups.length).toBeGreaterThanOrEqual(2);
+    expect(owned).toContain("crates/core/src/auth/mod.rs");
+    expect(owned).toContain("crates/core/src/auth/token.rs");
+    expect(owned).toContain("crates/core/src/storage/mod.rs");
+    expect(owned).toContain("crates/core/src/storage/db.rs");
+    expect(owned).toContain("crates/cli/src/commands.rs");
+    expect(owned).toContain("crates/cli/src/bin/admin/helpers.rs");
+    expect(owned).not.toContain("crates/core/src/lib.rs");
+    expect(owned).not.toContain("crates/cli/src/main.rs");
+    expect(owned).not.toContain("crates/cli/src/bin/worker.rs");
+    expect(owned).not.toContain("crates/cli/src/bin/admin/main.rs");
+    expect(titles.some((title) => title.includes("crates/core/src"))).toBe(true);
+    expect(
+      sourceGroups.find((feature) =>
+        feature.ownedFiles.some((file) => file.path === "crates/core/src/auth/mod.rs"),
+      ),
+    ).toMatchObject({
+      kind: "library",
+      confidence: "medium",
+      tags: expect.arrayContaining(["rust", "source-group"]),
+      contextFiles: [{ path: "crates/core/Cargo.toml", reason: "cargo package manifest" }],
+      tests: [],
+    });
+    expect(sourceGroups.every((feature) => feature.ownedFiles.length <= 12)).toBe(true);
+    expect(result.features.some((feature) => feature.title === "Rust library core")).toBe(true);
+    expect(result.features.some((feature) => feature.title === "Rust command cli")).toBe(true);
+    expect(result.features.some((feature) => feature.title === "Rust command worker")).toBe(true);
+  });
+
+  it("partitions oversized Rust source directories into bounded groups", async () => {
+    const root = await fixtureRoot("clawpatch-rust-source-chunk-");
+    await writeFixture(root, "Cargo.toml", '[package]\nname = "chunky"\n');
+    await writeFixture(root, "src/lib.rs", "pub fn root() {}\n");
+    for (let index = 1; index <= 20; index += 1) {
+      await writeFixture(root, `src/module_${index}.rs`, `pub fn f${index}() {}\n`);
+    }
+
+    const project = await detectProject(root);
+    const result = await mapFeatures(root, project, []);
+    const sourceGroups = result.features.filter(
+      (feature) => feature.source === "rust-source-group",
+    );
+    const owned = sourceGroups.flatMap((feature) => feature.ownedFiles.map((file) => file.path));
+
+    expect(sourceGroups.length).toBeGreaterThan(1);
+    expect(owned).toHaveLength(20);
+    expect(owned).not.toContain("src/lib.rs");
+    expect(sourceGroups.every((feature) => feature.ownedFiles.length <= 12)).toBe(true);
+    expect(sourceGroups.every((feature) => feature.entrypoints[0]?.path === "Cargo.toml")).toBe(
+      true,
+    );
+    expect(
+      sourceGroups.every((feature) =>
+        feature.contextFiles.some(
+          (file) => file.path === "Cargo.toml" && file.reason === "cargo package manifest",
+        ),
+      ),
+    ).toBe(true);
+  });
+
+  it("keeps Rust source group identities stable when modules are added", async () => {
+    const root = await fixtureRoot("clawpatch-rust-source-stable-");
+    await writeFixture(root, "Cargo.toml", '[package]\nname = "stable"\n');
+    await writeFixture(root, "src/lib.rs", "pub mod alpha;\n");
+    await writeFixture(root, "src/alpha.rs", "pub fn a() {}\n");
+    await writeFixture(root, "src/beta.rs", "pub fn b() {}\n");
+
+    const project = await detectProject(root);
+    const first = await mapFeatures(root, project, []);
+    const firstGroups = first.features.filter((feature) => feature.source === "rust-source-group");
+    const firstIds = firstGroups.map((feature) => feature.featureId).toSorted();
+
+    await writeFixture(root, "src/aardvark.rs", "pub fn first() {}\n");
+    const second = await mapFeatures(root, project, first.features);
+    const secondGroups = second.features.filter(
+      (feature) => feature.source === "rust-source-group",
+    );
+    const secondIds = secondGroups.map((feature) => feature.featureId).toSorted();
+
+    expect(firstIds.length).toBeGreaterThan(0);
+    for (const id of firstIds) {
+      expect(secondIds).toContain(id);
+    }
+    expect(second.stale).toBe(0);
+  });
+
   it("maps CMake C and C++ targets without duplicating main files", async () => {
     const root = await fixtureRoot("clawpatch-cmake-cpp-map-");
     const cmakeRoot = root.replaceAll("\\", "/");
diff --git a/src/mappers/rust.test.ts b/src/mappers/rust.test.ts
index e644e91..b8643ce 100644
--- a/src/mappers/rust.test.ts
+++ b/src/mappers/rust.test.ts
@@ -34,10 +34,21 @@ fn main() {}
     await writeFile(join(root, "src/utils/mod.rs"), "fn utils() {}");
 
     const seeds = await rustSeeds(root);
-    expect(seeds).toHaveLength(1);
+    expect(seeds).toHaveLength(2);
 
-    const contextPaths = seeds[0]!.contextFiles?.map((f) => f.path);
+    const command = seeds.find((seed) => seed.source === "rust-command");
+    const contextPaths = command?.contextFiles?.map((f) => f.path);
     expect(contextPaths).toEqual(["Cargo.toml", "src/api.rs", "src/utils/mod.rs"]);
+
+    const sourceGroup = seeds.find((seed) => seed.source === "rust-source-group");
+    expect(sourceGroup).toMatchObject({
+      entryPath: "Cargo.toml",
+      identityKey: "src",
+      ownedFiles: [
+        { path: "src/api.rs", reason: "source group src" },
+        { path: "src/utils/mod.rs", reason: "source group src" },
+      ],
+    });
   });
 
   it("cross-links lib.rs and main.rs", async () => {
@@ -119,18 +130,25 @@ members = ["crates/web", "crates/db"]
     await writeFile(join(root, "crates/db/src/models.rs"), "");
 
     const seeds = await rustSeeds(root);
-    expect(seeds).toHaveLength(2);
+    expect(seeds).toHaveLength(4);
 
-    const webSeed = seeds.find((s) => s.entryPath === "crates/web/src/main.rs")!;
+    const webSeed = seeds.find((seed) => seed.source === "rust-command")!;
     expect(webSeed.contextFiles?.map((f) => f.path)).toEqual([
       "crates/web/Cargo.toml",
       "crates/web/src/routes.rs",
     ]);
 
-    const dbSeed = seeds.find((s) => s.entryPath === "crates/db/src/lib.rs")!;
+    const dbSeed = seeds.find((seed) => seed.source === "rust-library")!;
     expect(dbSeed.contextFiles?.map((f) => f.path)).toEqual([
       "crates/db/Cargo.toml",
       "crates/db/src/models.rs",
     ]);
+
+    const sourceGroups = seeds.filter((seed) => seed.source === "rust-source-group");
+    expect(sourceGroups).toHaveLength(2);
+    expect(sourceGroups.map((seed) => seed.entryPath).toSorted()).toEqual([
+      "crates/db/Cargo.toml",
+      "crates/web/Cargo.toml",
+    ]);
   });
 });
diff --git a/src/mappers/rust.ts b/src/mappers/rust.ts
index 26090f6..11bf6ea 100644
--- a/src/mappers/rust.ts
+++ b/src/mappers/rust.ts
@@ -2,9 +2,11 @@ import { readFile, readdir } from "node:fs/promises";
 import { join } from "node:path";
 import { pathExists } from "../fs.js";
 import { shellQuotePath } from "../shell.js";
+import { partitionFileGroups } from "./grouping.js";
 import {
   isSafeDirectory,
   isSafeFile,
+  packageKind,
   packageTrustBoundaries,
   normalize,
   stripLineComments,
@@ -13,6 +15,7 @@ import {
 import { FeatureSeed, SeedFileRef } from "./types.js";
 
 const rustFeatureTestLimit = 5;
+const sourceGroupMaxOwnedFiles = 12;
 
 type RustTestRef = {
   path: string;
@@ -60,6 +63,14 @@ export async function rustSeeds(root: string): Promise<FeatureSeed[]> {
         ]),
       );
     }
+    seeds.push(
+      ...(await rustSourceGroupSeeds(root, {
+        sourceRoot: "src",
+        packageName,
+        manifestPath: "Cargo.toml",
+        testCommand: rustTestCommand,
+      })),
+    );
   }
   for (const member of await rustMemberDirs(root)) {
     const memberDir = member.dir;
@@ -106,10 +117,98 @@ export async function rustSeeds(root: string): Promise<FeatureSeed[]> {
         ]),
       );
     }
+    seeds.push(
+      ...(await rustSourceGroupSeeds(root, {
+        sourceRoot: `${memberDir}/src`,
+        packageName: memberName,
+        manifestPath: `${memberDir}/Cargo.toml`,
+        testCommand: member.testCommand,
+      })),
+    );
+  }
+  return seeds;
+}
+
+type RustSourceGroupOptions = {
+  sourceRoot: string;
+  packageName: string;
+  manifestPath: string;
+  testCommand: string | null;
+};
+
+async function rustSourceGroupSeeds(
+  root: string,
+  options: RustSourceGroupOptions,
+): Promise<FeatureSeed[]> {
+  const { sourceRoot, packageName, manifestPath, testCommand } = options;
+  if (!(await isSafeDirectory(root, join(root, sourceRoot)))) {
+    return [];
+  }
+  const files = (await walk(root, [sourceRoot])).filter(
+    (path) => isRustSourceFile(path) && !isRustPackageEntrypoint(path, sourceRoot),
+  );
+  if (files.length === 0) {
+    return [];
+  }
+
+  const contextFiles = await rustManifestContextFiles(root, manifestPath);
+  const seeds: FeatureSeed[] = [];
+  for (const group of partitionFileGroups(sourceRoot, files, sourceGroupMaxOwnedFiles)) {
+    seeds.push({
+      title: `Rust source ${group.label}`,
+      summary:
+        group.files.length === 1
+          ? `Rust source file ${group.files[0]}.`
+          : `Rust source group ${group.label} with ${group.files.length} files.`,
+      kind: packageKind(`${packageName} ${group.label}`),
+      source: "rust-source-group",
+      confidence: "medium",
+      entryPath: manifestPath,
+      identityKey: group.label,
+      symbol: group.label,
+      route: null,
+      command: null,
+      ownedFiles: group.files.map((path) => ({
+        path,
+        reason: `source group ${group.label}`,
+      })),
+      contextFiles,
+      tags: ["rust", "source-group"],
+      trustBoundaries: packageTrustBoundaries(`${packageName} ${group.label}`),
+      testCommand,
+      skipNearbyTests: true,
+    });
   }
   return seeds;
 }
 
+function isRustSourceFile(path: string): boolean {
+  return path.endsWith(".rs");
+}
+
+/**
+ * Package entrypoints already mapped as command/library/bin features.
+ * Remaining modules under src/ become reviewable source groups.
+ */
+function isRustPackageEntrypoint(path: string, sourceRoot: string): boolean {
+  if (path === `${sourceRoot}/lib.rs` || path === `${sourceRoot}/main.rs`) {
+    return true;
+  }
+  return new RegExp(`^${escapeRegExp(sourceRoot)}/bin/([^/]+\\.rs|[^/]+/main\\.rs)$`, "u").test(
+    path,
+  );
+}
+
+async function rustManifestContextFiles(
+  root: string,
+  manifestPath: string,
+): Promise<SeedFileRef[]> {
+  if (!(await isSafeFile(root, join(root, manifestPath)))) {
+    return [];
+  }
+  return [{ path: manifestPath, reason: "cargo package manifest" }];
+}
+
 type RustMemberDir = {
   dir: string;
   testCommand: string | null;