diff --git a/src/main/skill-github.ts b/src/main/skill-github.ts
index f267b88c..64db9683 100644
--- a/src/main/skill-github.ts
+++ b/src/main/skill-github.ts
@@ -1,4 +1,10 @@
-import { readResponseWithLimit } from "./skills/read-response-with-limit.js";
+import { readResponseBytesWithLimit, readResponseWithLimit } from "./skills/read-response-with-limit.js";
+
+export interface GitHubSkillFileData {
+  path: string;
+  content: Uint8Array;
+  mode: string | null;
+}
 
 /**
  * Data returned for each skill found in a GitHub repository.
@@ -6,7 +12,7 @@ import { readResponseWithLimit } from "./skills/read-response-with-limit.js";
 export interface GitHubSkillData {
   skillMdPath: string;
   markdown: string;
-  inventory: string[];
+  files: GitHubSkillFileData[];
   owner: string;
   repo: string;
 }
@@ -20,12 +26,44 @@ interface Logger {
 /** 2 MB — generous upper bound for a single SKILL.md (markdown) file. */
 export const MAX_SKILL_BYTES = 2 * 1024 * 1024;
 
-/** 32 MB — aggregate upper bound for all SKILL.md content from a single skill pack. */
+/** 8 MB — upper bound for a single non-SKILL.md package file. */
+export const MAX_SKILL_FILE_BYTES = 8 * 1024 * 1024;
+
+/** 32 MB — aggregate upper bound for all materialized files from a skill pack. */
 export const MAX_TOTAL_BYTES = 32 * 1024 * 1024;
 
 /** 10 MB — upper bound for the recursive git tree JSON response. */
 const MAX_TREE_BYTES = 10 * 1024 * 1024;
 
+interface GitHubTreeEntry {
+  path: string;
+  type: string;
+  mode?: string;
+}
+
+function encodeGitHubBlobPath(filePath: string): string {
+  if (filePath.includes("\0") || filePath.includes("\\") || filePath.startsWith("/") || /^[A-Za-z]:/.test(filePath)) {
+    throw new Error(`Invalid GitHub skill file path: ${filePath}`);
+  }
+  const parts = filePath.split("/");
+  if (parts.some((part) => part.length === 0 || part === "." || part === "..")) {
+    throw new Error(`Invalid GitHub skill file path: ${filePath}`);
+  }
+  return parts.map((part) => encodeURIComponent(part)).join("/");
+}
+
+function rawGitHubUrl(owner: string, repo: string, ref: string, filePath: string): string {
+  return `https://raw.githubusercontent.com/${owner}/${repo}/${ref}/${encodeGitHubBlobPath(filePath)}`;
+}
+
+function assertTotalSkillBytes(totalBytes: number): void {
+  if (totalBytes > MAX_TOTAL_BYTES) {
+    throw new Error(
+      `Skill pack exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
+    );
+  }
+}
+
 /**
  * Resolve the latest commit SHA for a given ref (branch, tag, or HEAD).
  * Returns the 40-character hex SHA on success, null on error.
@@ -87,7 +125,7 @@ export async function fetchGitHubSkills(
       return { skills: [], commitSha: ref };
     }
     const treeData = JSON.parse(await readResponseWithLimit(treeResponse, MAX_TREE_BYTES)) as {
-      tree?: Array<{ path: string; type: string }>;
+      tree?: GitHubTreeEntry[];
       sha?: string;
     };
     const treeSha = typeof treeData.sha === "string" ? treeData.sha : ref;
@@ -120,14 +158,15 @@ export async function fetchGitHubSkills(
 
     for (const skillMdPath of skillMdPaths) {
       try {
+        let skillBytes = 0;
         // Download content via raw.githubusercontent.com (no API rate limit)
-        const rawUrl = `https://raw.githubusercontent.com/${owner}/${repo}/${ref}/${skillMdPath}`;
+        const rawUrl = rawGitHubUrl(owner, repo, ref, skillMdPath);
         const contentResponse = await fetch(rawUrl);
         if (!contentResponse.ok) {
           logger?.warn(`Failed to download ${rawUrl}: ${contentResponse.status}`);
           continue;
         }
-        const remainingBudget = MAX_TOTAL_BYTES - totalBytes;
+        const remainingBudget = MAX_TOTAL_BYTES - totalBytes - skillBytes;
         const perFileCap = Math.min(MAX_SKILL_BYTES, Math.max(0, remainingBudget));
         if (perFileCap === 0) {
           throw new Error(
@@ -135,12 +174,8 @@ export async function fetchGitHubSkills(
           );
         }
         const markdown = await readResponseWithLimit(contentResponse, perFileCap);
-        totalBytes += Buffer.byteLength(markdown, "utf-8");
-        if (totalBytes > MAX_TOTAL_BYTES) {
-          throw new Error(
-            `Skill pack exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
-          );
-        }
+        skillBytes += Buffer.byteLength(markdown, "utf-8");
+        assertTotalSkillBytes(totalBytes + skillBytes);
 
         // Collect sibling files in the same directory (or subdirectories)
         const skillDir =
@@ -148,17 +183,42 @@ export async function fetchGitHubSkills(
             ? ""
             : skillMdPath.slice(0, skillMdPath.lastIndexOf("/"));
         const prefix = skillDir ? `${skillDir}/` : "";
-        const inventory = allPaths.filter(
-          (p) => p !== skillMdPath && (prefix ? p.startsWith(prefix) : !p.includes("/")),
+        const inventoryEntries = allEntries.filter(
+          (entry) => entry.path !== skillMdPath && (prefix ? entry.path.startsWith(prefix) : !entry.path.includes("/")),
         );
+        const files: GitHubSkillFileData[] = [];
+
+        for (const entry of inventoryEntries) {
+          const fileRemainingBudget = MAX_TOTAL_BYTES - totalBytes - skillBytes;
+          const fileCap = Math.min(MAX_SKILL_FILE_BYTES, Math.max(0, fileRemainingBudget));
+          if (fileCap === 0) {
+            throw new Error(
+              `Skill pack exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
+            );
+          }
+          const fileUrl = rawGitHubUrl(owner, repo, ref, entry.path);
+          const fileResponse = await fetch(fileUrl);
+          if (!fileResponse.ok) {
+            throw new Error(`Failed to download ${fileUrl}: ${fileResponse.status}`);
+          }
+          const content = await readResponseBytesWithLimit(fileResponse, fileCap);
+          skillBytes += content.byteLength;
+          assertTotalSkillBytes(totalBytes + skillBytes);
+          files.push({
+            path: entry.path,
+            content,
+            mode: entry.mode ?? null,
+          });
+        }
 
         skills.push({
           skillMdPath,
           markdown,
-          inventory,
+          files,
           owner,
-          repo,
+            repo,
         });
+        totalBytes += skillBytes;
       } catch (err) {
         logger?.error(`Error downloading skill ${skillMdPath}:`, err);
         continue;
diff --git a/src/main/skills/discovery.ts b/src/main/skills/discovery.ts
index 7c382c94..650c9ad6 100644
--- a/src/main/skills/discovery.ts
+++ b/src/main/skills/discovery.ts
@@ -1,4 +1,4 @@
-import { readdirSync, realpathSync, type Dirent } from "node:fs";
+import { readdirSync, realpathSync, statSync, type Dirent } from "node:fs";
 import { join, resolve, relative } from "node:path";
 import type { FileInventoryEntry } from "../skill-types.js";
 import { classifyInventoryKind } from "../skill-format.js";
@@ -133,10 +133,18 @@ export function buildLocalInventory(
       if (!entry.isFile()) continue;
       const resolvedPath = resolve(fullPath);
       if (resolvedPath === skillMdPath) continue;
+      let fileStat;
+      try {
+        fileStat = statSync(resolvedPath);
+      } catch (err) {
+        logger.warn(`[skill-import] statSync failed for ${resolvedPath}:`, err instanceof Error ? err.message : String(err));
+        continue;
+      }
+      if (!fileStat.isFile()) continue;
       const relativePath = relative(skillDir, resolvedPath).replace(/\\/g, "/");
       inventory.push({
         path: relativePath,
-        kind: classifyInventoryKind(relativePath),
+        kind: (fileStat.mode & 0o111) !== 0 ? "script" : classifyInventoryKind(relativePath),
       });
     }
   }
diff --git a/src/main/skills/import-github.ts b/src/main/skills/import-github.ts
index 9810c2b4..cd8c3117 100644
--- a/src/main/skills/import-github.ts
+++ b/src/main/skills/import-github.ts
@@ -1,6 +1,5 @@
 import { randomUUID } from "node:crypto";
-import { mkdir, writeFile } from "node:fs/promises";
-import { join, basename, dirname } from "node:path";
+import { basename, dirname } from "node:path";
 import type { AppDatabase } from "../database";
 import type { FileInventoryEntry, SkillImportResult, SkillSourceType } from "../skill-types.js";
 import {
@@ -15,9 +14,8 @@ import {
 import {
   resolveGitHubCommitSha,
   fetchGitHubSkills,
-  MAX_SKILL_BYTES,
-  MAX_TOTAL_BYTES,
 } from "../skill-github.js";
+import { materializeSkillFiles, type MaterializedSkillFile } from "./materialize";
 
 interface GitHubImportDeps {
   db: AppDatabase;
@@ -45,23 +43,6 @@ export function createGitHubImporter({ db, logger, skillFilesDir }: GitHubImport
     }
   }
 
-  async function materializeSkillFiles(
-    companyId: string,
-    slug: string,
-    markdown: string,
-    _inventory: FileInventoryEntry[],
-  ): Promise<string> {
-    if (markdown.length * 2 > MAX_SKILL_BYTES) {
-      throw new Error(
-        `SKILL.md exceeds ${MAX_SKILL_BYTES}-byte limit`,
-      );
-    }
-    const dir = skillFilesDir(companyId, slug);
-    await mkdir(dir, { recursive: true });
-    await writeFile(join(dir, "SKILL.md"), markdown, "utf-8");
-    return dir;
-  }
-
   async function importFromGitHub(
     companyId: string,
     url: string,
@@ -90,16 +71,8 @@ export function createGitHubImporter({ db, logger, skillFilesDir }: GitHubImport
     const results: SkillImportResult[] = [];
     const sourceType: SkillSourceType = originalSkillsShUrl ? "skills_sh" : "github";
     const nowTs = new Date().toISOString();
-    let totalMaterializedBytes = 0;
 
     for (const ghSkill of githubSkills) {
-      const skillBytes = Buffer.byteLength(ghSkill.markdown, "utf-8");
-      totalMaterializedBytes += skillBytes;
-      if (totalMaterializedBytes > MAX_TOTAL_BYTES) {
-        throw new Error(
-          `Skill pack exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
-        );
-      }
       const parsed = parseFrontmatterMarkdown(ghSkill.markdown);
       const rawSlug =
         normalizeSkillSlug(parsed.frontmatter.slug as string | undefined) ??
@@ -115,16 +88,18 @@ export function createGitHubImporter({ db, logger, skillFilesDir }: GitHubImport
           ? ""
           : ghSkill.skillMdPath.slice(0, ghSkill.skillMdPath.lastIndexOf("/"));
       const prefix = skillDir ? `${skillDir}/` : "";
-      const inventory: FileInventoryEntry[] = [
-        { path: "SKILL.md", kind: "skill" as const },
-        ...ghSkill.inventory.map((filePath) => {
-          const relativePath = prefix ? filePath.slice(prefix.length) : filePath;
+      const materializedFiles: MaterializedSkillFile[] = [
+        { path: "SKILL.md", kind: "skill", content: ghSkill.markdown },
+        ...ghSkill.files.map((file) => {
+          const relativePath = prefix ? file.path.slice(prefix.length) : file.path;
           return {
             path: relativePath,
-            kind: classifyInventoryKind(relativePath),
+            kind: file.mode === "100755" ? "script" as const : classifyInventoryKind(relativePath),
+            content: file.content,
           };
         }),
       ];
+      const inventory: FileInventoryEntry[] = materializedFiles.map(({ path, kind }) => ({ path, kind }));
 
       const metadata: Record<string, unknown> = {
         sourceKind: "github",
@@ -153,7 +128,7 @@ export function createGitHubImporter({ db, logger, skillFilesDir }: GitHubImport
 
       const skillId = randomUUID();
 
-      await materializeSkillFiles(companyId, rawSlug, ghSkill.markdown, inventory);
+      await materializeSkillFiles(skillFilesDir(companyId, rawSlug), materializedFiles);
 
       const { isUpdate } = db.core.skills.upsertCompanySkill({
         id: skillId,
diff --git a/src/main/skills/import-local.ts b/src/main/skills/import-local.ts
index 9963b179..cfde352d 100644
--- a/src/main/skills/import-local.ts
+++ b/src/main/skills/import-local.ts
@@ -1,6 +1,6 @@
 import { randomUUID } from "node:crypto";
 import { existsSync, readFileSync, realpathSync, statSync } from "node:fs";
-import { resolve, basename, dirname } from "node:path";
+import { resolve, basename, dirname, isAbsolute, relative } from "node:path";
 import type { AppDatabase } from "../database";
 import type { FileInventoryEntry, SkillImportResult } from "../skill-types.js";
 import { parseFrontmatterMarkdown, deriveTrustLevel } from "../skill-format.js";
@@ -14,7 +14,8 @@ import {
   findSkillMdFiles,
   buildLocalInventory,
 } from "./discovery";
-import { materializeSkillFiles } from "./materialize";
+import { materializeSkillFiles, normalizeMaterializedRelativePath, type MaterializedSkillFile } from "./materialize";
+import { MAX_SKILL_BYTES, MAX_SKILL_FILE_BYTES, MAX_TOTAL_BYTES } from "../skill-github.js";
 
 export interface LocalImportContext {
   db: AppDatabase;
@@ -26,6 +27,70 @@ export interface LocalImportContext {
   skillFilesDir: (companyId: string, slug: string) => string;
 }
 
+function assertLocalFileSize(filePath: string, size: number, maxBytes: number): void {
+  if (size > maxBytes) {
+    throw new Error(`${filePath} exceeds ${maxBytes}-byte limit`);
+  }
+}
+
+function assertLocalPackageSize(totalBytes: number): void {
+  if (totalBytes > MAX_TOTAL_BYTES) {
+    throw new Error(`Skill package exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`);
+  }
+}
+
+function readLocalSkillMarkdown(skillMdPath: string): string {
+  const stat = statSync(skillMdPath);
+  if (!stat.isFile()) {
+    throw new Error(`Local skill path is not a file: ${skillMdPath}`);
+  }
+  assertLocalFileSize(skillMdPath, stat.size, MAX_SKILL_BYTES);
+  return readFileSync(skillMdPath, "utf-8");
+}
+
+function assertPathInsideRoot(rootDir: string, targetPath: string, relativePath: string): void {
+  const relativePathFromRoot = relative(rootDir, targetPath);
+  if (relativePathFromRoot.length === 0 || relativePathFromRoot.startsWith("..") || isAbsolute(relativePathFromRoot)) {
+    throw new Error(`Skill inventory path escapes source directory: ${relativePath}`);
+  }
+}
+
+function buildLocalMaterializedFiles(
+  skillDir: string,
+  markdown: string,
+  markdownBytes: number,
+  inventory: FileInventoryEntry[],
+): MaterializedSkillFile[] {
+  const realSkillDir = realpathSync(skillDir);
+  const files: MaterializedSkillFile[] = [
+    { path: "SKILL.md", kind: "skill", content: markdown },
+  ];
+  let totalBytes = markdownBytes;
+  assertLocalPackageSize(totalBytes);
+
+  for (const entry of inventory) {
+    if (entry.path === "SKILL.md") continue;
+    const relativePath = normalizeMaterializedRelativePath(entry.path);
+    const sourcePath = resolve(realSkillDir, ...relativePath.split("/"));
+    const realSourcePath = realpathSync(sourcePath);
+    assertPathInsideRoot(realSkillDir, realSourcePath, relativePath);
+    const stat = statSync(realSourcePath);
+    if (!stat.isFile()) {
+      throw new Error(`Skill inventory path is not a file: ${relativePath}`);
+    }
+    assertLocalFileSize(relativePath, stat.size, MAX_SKILL_FILE_BYTES);
+    totalBytes += stat.size;
+    assertLocalPackageSize(totalBytes);
+    files.push({
+      path: relativePath,
+      kind: entry.kind,
+      content: readFileSync(realSourcePath),
+    });
+  }
+
+  return files;
+}
+
 export async function importFromLocal(
   ctx: LocalImportContext,
   companyId: string,
@@ -47,7 +112,8 @@ export async function importFromLocal(
   const nowTs = new Date().toISOString();
 
   if (stat.isFile()) {
-    const markdown = readFileSync(resolvedPath, "utf-8");
+    const markdown = readLocalSkillMarkdown(resolvedPath);
+    assertLocalPackageSize(Buffer.byteLength(markdown, "utf-8"));
     const parsed = parseFrontmatterMarkdown(markdown);
     const rawSlug =
       normalizeSkillSlug(parsed.frontmatter.slug as string | undefined) ??
@@ -67,7 +133,9 @@ export async function importFromLocal(
     });
 
     const skillId = randomUUID();
-    await materializeSkillFiles(skillFilesDir(companyId, rawSlug), markdown, inventory);
+    await materializeSkillFiles(skillFilesDir(companyId, rawSlug), [
+      { path: "SKILL.md", kind: "skill", content: markdown },
+    ]);
 
     const { isUpdate } = db.core.skills.upsertCompanySkill({
       id: skillId,
@@ -100,7 +168,8 @@ export async function importFromLocal(
 
   for (const skillMdPath of skillMdFiles) {
     const skillDir = dirname(skillMdPath);
-    const markdown = readFileSync(skillMdPath, "utf-8");
+    const markdown = readLocalSkillMarkdown(skillMdPath);
+    const markdownBytes = Buffer.byteLength(markdown, "utf-8");
     const parsed = parseFrontmatterMarkdown(markdown);
     const rawSlug =
       normalizeSkillSlug(parsed.frontmatter.slug as string | undefined) ??
@@ -119,7 +188,10 @@ export async function importFromLocal(
     });
 
     const skillId = randomUUID();
-    await materializeSkillFiles(skillFilesDir(companyId, rawSlug), markdown, inventory);
+    await materializeSkillFiles(
+      skillFilesDir(companyId, rawSlug),
+      buildLocalMaterializedFiles(skillDir, markdown, markdownBytes, inventory),
+    );
 
     const { isUpdate } = db.core.skills.upsertCompanySkill({
       id: skillId,
diff --git a/src/main/skills/import-url.ts b/src/main/skills/import-url.ts
index d90e03aa..bd0d9479 100644
--- a/src/main/skills/import-url.ts
+++ b/src/main/skills/import-url.ts
@@ -59,7 +59,9 @@ export async function importFromUrl(
   });
 
   const skillId = randomUUID();
-  await materializeSkillFiles(skillFilesDir(companyId, rawSlug), markdown, inventory);
+  await materializeSkillFiles(skillFilesDir(companyId, rawSlug), [
+    { path: "SKILL.md", kind: "skill", content: markdown },
+  ]);
 
   const { isUpdate } = db.core.skills.upsertCompanySkill({
     id: skillId,
diff --git a/src/main/skills/materialize.ts b/src/main/skills/materialize.ts
index 5ee2caf0..9f8b1f90 100644
--- a/src/main/skills/materialize.ts
+++ b/src/main/skills/materialize.ts
@@ -1,19 +1,142 @@
 import { existsSync } from "node:fs";
-import { mkdir, writeFile, rm } from "node:fs/promises";
-import { join } from "node:path";
+import { mkdir, rename, writeFile, rm } from "node:fs/promises";
+import { randomUUID } from "node:crypto";
+import { basename, dirname, isAbsolute, join, relative, resolve } from "node:path";
 import type { FileInventoryEntry } from "../skill-types.js";
-import { MAX_SKILL_BYTES } from "../skill-github.js";
+import { MAX_SKILL_BYTES, MAX_SKILL_FILE_BYTES, MAX_TOTAL_BYTES } from "../skill-github.js";
+
+export interface MaterializedSkillFile extends FileInventoryEntry {
+  content: string | Uint8Array;
+}
+
+interface PreparedSkillFile extends FileInventoryEntry {
+  content: Uint8Array;
+}
+
+const MATERIALIZED_FILE_MODE = 0o600;
+const MATERIALIZED_SCRIPT_MODE = 0o700;
+const MATERIALIZED_DIR_MODE = 0o700;
+
+export function normalizeMaterializedRelativePath(filePath: string): string {
+  if (filePath.includes("\0")) {
+    throw new Error("Skill file path contains a null byte");
+  }
+  const normalized = filePath.replace(/\\/g, "/");
+  if (normalized !== filePath) {
+    throw new Error(`Skill file path must use POSIX separators: ${filePath}`);
+  }
+  if (normalized.length === 0 || normalized.startsWith("/") || /^[A-Za-z]:/.test(normalized)) {
+    throw new Error(`Skill file path must be relative: ${filePath}`);
+  }
+  const parts = normalized.split("/");
+  if (parts.some((part) => part.length === 0 || part === "." || part === "..")) {
+    throw new Error(`Skill file path contains traversal segments: ${filePath}`);
+  }
+  return parts.join("/");
+}
+
+function encodeContent(content: string | Uint8Array): Uint8Array {
+  if (typeof content === "string") {
+    return Buffer.from(content, "utf-8");
+  }
+  return content;
+}
+
+function ensureTargetInsideRoot(rootDir: string, targetPath: string, relativePath: string): void {
+  const root = resolve(rootDir);
+  const targetRelative = relative(root, targetPath);
+  if (targetRelative.length === 0 || targetRelative.startsWith("..") || isAbsolute(targetRelative)) {
+    throw new Error(`Skill file path escapes materialization root: ${relativePath}`);
+  }
+}
+
+function prepareMaterializedFiles(files: MaterializedSkillFile[]): PreparedSkillFile[] {
+  const seen = new Set<string>();
+  const prepared: PreparedSkillFile[] = [];
+  let totalBytes = 0;
+  let hasRootSkill = false;
+
+  for (const file of files) {
+    const path = normalizeMaterializedRelativePath(file.path);
+    const duplicateKey = process.platform === "win32" ? path.toLowerCase() : path;
+    if (seen.has(duplicateKey)) {
+      throw new Error(`Duplicate skill file path: ${path}`);
+    }
+    seen.add(duplicateKey);
+
+    const content = encodeContent(file.content);
+    const maxBytes = path === "SKILL.md" ? MAX_SKILL_BYTES : MAX_SKILL_FILE_BYTES;
+    if (content.byteLength > maxBytes) {
+      throw new Error(`${path} exceeds ${maxBytes}-byte limit`);
+    }
+    totalBytes += content.byteLength;
+    if (totalBytes > MAX_TOTAL_BYTES) {
+      throw new Error(`Skill package exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`);
+    }
+    if (path === "SKILL.md") {
+      hasRootSkill = true;
+    }
+    prepared.push({ path, kind: file.kind, content });
+  }
+
+  if (!hasRootSkill) {
+    throw new Error("Skill package is missing SKILL.md");
+  }
+  return prepared;
+}
+
+async function replaceDirectoryWithFiles(dir: string, files: PreparedSkillFile[]): Promise<void> {
+  const parentDir = dirname(dir);
+  const dirName = basename(dir);
+  const stagingDir = join(parentDir, `.${dirName}.${randomUUID()}.tmp`);
+  let backupDir: string | null = null;
+
+  await mkdir(parentDir, { recursive: true, mode: MATERIALIZED_DIR_MODE });
+  await mkdir(stagingDir, { recursive: true, mode: MATERIALIZED_DIR_MODE });
+
+  try {
+    for (const file of files) {
+      const target = resolve(stagingDir, ...file.path.split("/"));
+      ensureTargetInsideRoot(stagingDir, target, file.path);
+      await mkdir(dirname(target), { recursive: true, mode: MATERIALIZED_DIR_MODE });
+      await writeFile(target, file.content, {
+        mode: file.kind === "script" ? MATERIALIZED_SCRIPT_MODE : MATERIALIZED_FILE_MODE,
+      });
+    }
+
+    if (existsSync(dir)) {
+      backupDir = join(parentDir, `.${dirName}.${randomUUID()}.old`);
+      await rename(dir, backupDir);
+    }
+
+    try {
+      await rename(stagingDir, dir);
+    } catch (error) {
+      if (backupDir && existsSync(backupDir)) {
+        await rename(backupDir, dir);
+        backupDir = null;
+      }
+      throw error;
+    }
+
+    if (backupDir) {
+      await rm(backupDir, { recursive: true, force: true });
+      backupDir = null;
+    }
+  } finally {
+    await rm(stagingDir, { recursive: true, force: true });
+    if (backupDir) {
+      await rm(backupDir, { recursive: true, force: true });
+    }
+  }
+}
 
 export async function materializeSkillFiles(
   dir: string,
-  markdown: string,
-  _inventory: FileInventoryEntry[],
+  files: MaterializedSkillFile[],
 ): Promise<string> {
-  if (markdown.length * 2 > MAX_SKILL_BYTES) {
-    throw new Error(`SKILL.md exceeds ${MAX_SKILL_BYTES}-byte limit`);
-  }
-  await mkdir(dir, { recursive: true });
-  await writeFile(join(dir, "SKILL.md"), markdown, "utf-8");
+  const prepared = prepareMaterializedFiles(files);
+  await replaceDirectoryWithFiles(dir, prepared);
   return dir;
 }
 
diff --git a/src/main/skills/read-response-with-limit.ts b/src/main/skills/read-response-with-limit.ts
index 9233b680..bee93ffb 100644
--- a/src/main/skills/read-response-with-limit.ts
+++ b/src/main/skills/read-response-with-limit.ts
@@ -1,8 +1,13 @@
-export async function readResponseWithLimit(response: Response, maxBytes: number): Promise<string> {
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+function assertValidByteLimit(maxBytes: number): void {
   if (!Number.isSafeInteger(maxBytes) || maxBytes < 0) {
     throw new Error(`Invalid response byte limit: ${maxBytes}`);
   }
+}
 
+function validateContentLength(response: Response, maxBytes: number): void {
   const contentLengthHeader = response.headers.get("Content-Length");
   if (contentLengthHeader !== null) {
     const contentLength = Number(contentLengthHeader);
@@ -13,15 +18,29 @@ export async function readResponseWithLimit(response: Response, maxBytes: number
       throw new Error(`Response too large: ${contentLength} bytes (max ${maxBytes})`);
     }
   }
+}
+
+function assertWithinLimit(byteLength: number, maxBytes: number): void {
+  if (byteLength > maxBytes) {
+    throw new Error(`Response body exceeded ${maxBytes} bytes`);
+  }
+}
+
+export async function readResponseBytesWithLimit(response: Response, maxBytes: number): Promise<Uint8Array> {
+  assertValidByteLimit(maxBytes);
+  validateContentLength(response, maxBytes);
 
   const reader = response.body?.getReader();
   if (!reader) {
-    const text = await response.text();
-    const byteLength = new TextEncoder().encode(text).byteLength;
-    if (byteLength > maxBytes) {
-      throw new Error(`Response body exceeded ${maxBytes} bytes`);
+    if (typeof response.arrayBuffer === "function") {
+      const bytes = new Uint8Array(await response.arrayBuffer());
+      assertWithinLimit(bytes.byteLength, maxBytes);
+      return bytes;
     }
-    return text;
+    const text = await response.text();
+    const bytes = encoder.encode(text);
+    assertWithinLimit(bytes.byteLength, maxBytes);
+    return bytes;
   }
 
   const chunks: Uint8Array[] = [];
@@ -33,7 +52,7 @@ export async function readResponseWithLimit(response: Response, maxBytes: number
     totalBytes += value.byteLength;
     if (totalBytes > maxBytes) {
       await reader.cancel();
-      throw new Error(`Response body exceeded ${maxBytes} bytes`);
+      assertWithinLimit(totalBytes, maxBytes);
     }
     chunks.push(value);
   }
@@ -45,5 +64,9 @@ export async function readResponseWithLimit(response: Response, maxBytes: number
     offset += chunk.byteLength;
   }
 
-  return new TextDecoder().decode(body);
+  return body;
+}
+
+export async function readResponseWithLimit(response: Response, maxBytes: number): Promise<string> {
+  return decoder.decode(await readResponseBytesWithLimit(response, maxBytes));
 }
diff --git a/tests/unit/skill-github-import-materialize.test.ts b/tests/unit/skill-github-import-materialize.test.ts
new file mode 100644
index 00000000..d5e1180f
--- /dev/null
+++ b/tests/unit/skill-github-import-materialize.test.ts
@@ -0,0 +1,92 @@
+import { mkdtemp, readFile, rm } from "node:fs/promises";
+import { statSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { AppDatabase } from "@main/database";
+import { createGitHubImporter } from "@main/skills/import-github";
+
+const commitSha = "a".repeat(40);
+
+describe("GitHub skill import materialization", () => {
+  let tempDir: string;
+  let db: AppDatabase;
+  let companyId: string;
+
+  beforeEach(async () => {
+    tempDir = await mkdtemp(join(tmpdir(), "agentcompany-skill-github-import-"));
+    db = new AppDatabase(tempDir);
+    db.init();
+    companyId = db.core.company.saveCompany({
+      name: "GitHub Skill Import Test",
+      description: "Materializes complete GitHub skill packages",
+      status: "active",
+    });
+  });
+
+  afterEach(async () => {
+    vi.unstubAllGlobals();
+    db.close();
+    await rm(tempDir, { recursive: true, force: true });
+  });
+
+  it("downloads and materializes GitHub inventory files", async () => {
+    const fetchMock = vi.fn(async (input: string | URL | Request) => {
+      const url = String(input);
+      if (url === "https://api.github.com/repos/acme/skills/commits/HEAD") {
+        return new Response(commitSha);
+      }
+      if (url === `https://api.github.com/repos/acme/skills/git/trees/${commitSha}?recursive=1`) {
+        return new Response(JSON.stringify({
+          sha: commitSha,
+          tree: [
+            { path: "review/SKILL.md", type: "blob", mode: "100644" },
+            { path: "review/references/api.md", type: "blob", mode: "100644" },
+            { path: "review/scripts/run.sh", type: "blob", mode: "100755" },
+          ],
+        }));
+      }
+      if (url === `https://raw.githubusercontent.com/acme/skills/${commitSha}/review/SKILL.md`) {
+        return new Response("---\nname: Review\nslug: review\n---\n# Review\n");
+      }
+      if (url === `https://raw.githubusercontent.com/acme/skills/${commitSha}/review/references/api.md`) {
+        return new Response("API notes");
+      }
+      if (url === `https://raw.githubusercontent.com/acme/skills/${commitSha}/review/scripts/run.sh`) {
+        return new Response("echo review\n");
+      }
+      return new Response("missing", { status: 404 });
+    });
+    vi.stubGlobal("fetch", fetchMock);
+
+    const importer = createGitHubImporter({
+      db,
+      logger: {
+        info: vi.fn(),
+        warn: vi.fn(),
+        error: vi.fn(),
+      },
+      skillFilesDir: (ownerCompanyId, slug) => join(tempDir, "skills", ownerCompanyId, slug),
+    });
+
+    const results = await importer.importFromGitHub(companyId, "https://github.com/acme/skills", null, null);
+
+    expect(results).toHaveLength(1);
+    const materializedDir = join(tempDir, "skills", companyId, "review");
+    await expect(readFile(join(materializedDir, "SKILL.md"), "utf-8")).resolves.toContain("# Review");
+    await expect(readFile(join(materializedDir, "references", "api.md"), "utf-8")).resolves.toBe("API notes");
+    await expect(readFile(join(materializedDir, "scripts", "run.sh"), "utf-8")).resolves.toBe("echo review\n");
+    expect(statSync(join(materializedDir, "scripts", "run.sh")).mode & 0o100).toBe(0o100);
+    expect(statSync(join(materializedDir, "scripts", "run.sh")).mode & 0o011).toBe(0);
+
+    const [skill] = db.core.skills.listCompanySkills(companyId);
+    expect(skill?.trustLevel).toBe("scripts_executables");
+    expect(skill?.fileInventory).toEqual([
+      { path: "SKILL.md", kind: "skill" },
+      { path: "references/api.md", kind: "reference" },
+      { path: "scripts/run.sh", kind: "script" },
+    ]);
+    expect(fetchMock).toHaveBeenCalledWith(`https://raw.githubusercontent.com/acme/skills/${commitSha}/review/references/api.md`);
+    expect(fetchMock).toHaveBeenCalledWith(`https://raw.githubusercontent.com/acme/skills/${commitSha}/review/scripts/run.sh`);
+  });
+});
diff --git a/tests/unit/skill-local-import-materialize.test.ts b/tests/unit/skill-local-import-materialize.test.ts
new file mode 100644
index 00000000..f608e89b
--- /dev/null
+++ b/tests/unit/skill-local-import-materialize.test.ts
@@ -0,0 +1,98 @@
+import { existsSync, statSync } from "node:fs";
+import { chmod, mkdir, mkdtemp, readFile, rm, truncate, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { AppDatabase } from "@main/database";
+import { MAX_SKILL_FILE_BYTES, MAX_TOTAL_BYTES } from "@main/skill-github";
+import { importFromLocal } from "@main/skills/import-local";
+
+describe("local skill import materialization", () => {
+  let tempDir: string;
+  let db: AppDatabase;
+  let companyId: string;
+
+  beforeEach(async () => {
+    tempDir = await mkdtemp(join(tmpdir(), "agentcompany-skill-local-import-"));
+    db = new AppDatabase(tempDir);
+    db.init();
+    companyId = db.core.company.saveCompany({
+      name: "Local Skill Import Test",
+      description: "Materializes complete local skill packages",
+      status: "active",
+    });
+  });
+
+  afterEach(async () => {
+    db.close();
+    await rm(tempDir, { recursive: true, force: true });
+  });
+
+  it("copies local inventory files and records executable sources as scripts", async () => {
+    const sourceDir = join(tempDir, "source", "review");
+    await mkdir(join(sourceDir, "references"), { recursive: true });
+    await mkdir(join(sourceDir, "scripts"), { recursive: true });
+    await mkdir(join(sourceDir, "assets"), { recursive: true });
+    await writeFile(join(sourceDir, "SKILL.md"), "---\nname: Review\nslug: review\n---\n# Review\n", "utf-8");
+    await writeFile(join(sourceDir, "references", "api.md"), "API notes", "utf-8");
+    await writeFile(join(sourceDir, "scripts", "run.sh"), "echo review\n", "utf-8");
+    await chmod(join(sourceDir, "scripts", "run.sh"), 0o755);
+    await writeFile(join(sourceDir, "assets", "logo.bin"), new Uint8Array([7, 8, 9]));
+
+    const results = await importFromLocal({
+      db,
+      logger: {
+        info: vi.fn(),
+        warn: vi.fn(),
+        error: vi.fn(),
+      },
+      skillFilesDir: (ownerCompanyId, slug) => join(tempDir, "skills", ownerCompanyId, slug),
+    }, companyId, sourceDir);
+
+    expect(results).toHaveLength(1);
+    const materializedDir = join(tempDir, "skills", companyId, "review");
+    await expect(readFile(join(materializedDir, "SKILL.md"), "utf-8")).resolves.toContain("# Review");
+    await expect(readFile(join(materializedDir, "references", "api.md"), "utf-8")).resolves.toBe("API notes");
+    await expect(readFile(join(materializedDir, "scripts", "run.sh"), "utf-8")).resolves.toBe("echo review\n");
+    await expect(readFile(join(materializedDir, "assets", "logo.bin"))).resolves.toEqual(Buffer.from([7, 8, 9]));
+    expect(statSync(join(materializedDir, "scripts", "run.sh")).mode & 0o100).toBe(0o100);
+    expect(statSync(join(materializedDir, "scripts", "run.sh")).mode & 0o011).toBe(0);
+
+    const [skill] = db.core.skills.listCompanySkills(companyId);
+    expect(skill?.trustLevel).toBe("scripts_executables");
+    expect(skill?.fileInventory).toEqual([
+      { path: "SKILL.md", kind: "skill" },
+      { path: "assets/logo.bin", kind: "asset" },
+      { path: "references/api.md", kind: "reference" },
+      { path: "scripts/run.sh", kind: "script" },
+    ]);
+    expect(existsSync(materializedDir)).toBe(true);
+  });
+
+  it("rejects local packages whose aggregate size exceeds the limit before reading oversized inventory", async () => {
+    const sourceDir = join(tempDir, "source", "large");
+    await mkdir(join(sourceDir, "assets"), { recursive: true });
+    await writeFile(join(sourceDir, "SKILL.md"), "---\nname: Large\nslug: large\n---\n", "utf-8");
+
+    const fileCount = Math.ceil(MAX_TOTAL_BYTES / MAX_SKILL_FILE_BYTES) + 1;
+    for (let index = 0; index < fileCount; index += 1) {
+      await writeFile(join(sourceDir, "assets", `chunk-${index}.bin`), "");
+      await truncate(join(sourceDir, "assets", `chunk-${index}.bin`), MAX_SKILL_FILE_BYTES);
+    }
+
+    await expect(importFromLocal({
+      db,
+      logger: {
+        info: vi.fn(),
+        warn: vi.fn(),
+        error: vi.fn(),
+      },
+      skillFilesDir: (ownerCompanyId, slug) => join(tempDir, "skills", ownerCompanyId, slug),
+    }, companyId, sourceDir)).rejects.toThrow(
+      `Skill package exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
+    );
+
+    expect(existsSync(join(tempDir, "skills", companyId, "large"))).toBe(false);
+    expect(db.core.skills.listCompanySkills(companyId)).toEqual([]);
+  });
+});
diff --git a/tests/unit/skill-materialize.test.ts b/tests/unit/skill-materialize.test.ts
new file mode 100644
index 00000000..1b08937b
--- /dev/null
+++ b/tests/unit/skill-materialize.test.ts
@@ -0,0 +1,84 @@
+import { existsSync, statSync } from "node:fs";
+import { mkdtemp, readFile, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { MAX_SKILL_FILE_BYTES, MAX_TOTAL_BYTES } from "@main/skill-github";
+import { materializeSkillFiles } from "@main/skills/materialize";
+
+describe("skill materialization", () => {
+  let tempDir: string;
+
+  beforeEach(async () => {
+    tempDir = await mkdtemp(join(tmpdir(), "agentcompany-skill-materialize-"));
+  });
+
+  afterEach(async () => {
+    await rm(tempDir, { recursive: true, force: true });
+  });
+
+  it("materializes every inventory file and preserves script executability", async () => {
+    const dir = join(tempDir, "skills", "company", "review");
+
+    await materializeSkillFiles(dir, [
+      { path: "SKILL.md", kind: "skill", content: "---\nname: Review\n---\n" },
+      { path: "references/api.md", kind: "reference", content: "API notes" },
+      { path: "assets/logo.bin", kind: "asset", content: new Uint8Array([1, 2, 3]) },
+      { path: "scripts/run.sh", kind: "script", content: "echo review\n" },
+    ]);
+
+    await expect(readFile(join(dir, "SKILL.md"), "utf-8")).resolves.toContain("Review");
+    await expect(readFile(join(dir, "references", "api.md"), "utf-8")).resolves.toBe("API notes");
+    await expect(readFile(join(dir, "assets", "logo.bin"))).resolves.toEqual(Buffer.from([1, 2, 3]));
+    await expect(readFile(join(dir, "scripts", "run.sh"), "utf-8")).resolves.toBe("echo review\n");
+    expect(statSync(join(dir, "scripts", "run.sh")).mode & 0o100).toBe(0o100);
+    expect(statSync(join(dir, "scripts", "run.sh")).mode & 0o011).toBe(0);
+    expect(statSync(join(dir, "references", "api.md")).mode & 0o111).toBe(0);
+  });
+
+  it("replaces stale files when a skill is re-materialized", async () => {
+    const dir = join(tempDir, "skills", "company", "review");
+    await materializeSkillFiles(dir, [
+      { path: "SKILL.md", kind: "skill", content: "old" },
+      { path: "references/stale.md", kind: "reference", content: "stale" },
+    ]);
+
+    await materializeSkillFiles(dir, [
+      { path: "SKILL.md", kind: "skill", content: "new" },
+    ]);
+
+    await expect(readFile(join(dir, "SKILL.md"), "utf-8")).resolves.toBe("new");
+    expect(existsSync(join(dir, "references", "stale.md"))).toBe(false);
+  });
+
+  it("rejects traversal paths before writing the package", async () => {
+    const dir = join(tempDir, "skills", "company", "bad");
+
+    await expect(materializeSkillFiles(dir, [
+      { path: "SKILL.md", kind: "skill", content: "ok" },
+      { path: "../escape.md", kind: "markdown", content: "bad" },
+    ])).rejects.toThrow("Skill file path contains traversal segments: ../escape.md");
+    expect(existsSync(dir)).toBe(false);
+  });
+
+  it("enforces single-file and aggregate package byte limits", async () => {
+    const dir = join(tempDir, "skills", "company", "large");
+
+    await expect(materializeSkillFiles(dir, [
+      { path: "SKILL.md", kind: "skill", content: "ok" },
+      { path: "assets/too-large.bin", kind: "asset", content: new Uint8Array(MAX_SKILL_FILE_BYTES + 1) },
+    ])).rejects.toThrow(`assets/too-large.bin exceeds ${MAX_SKILL_FILE_BYTES}-byte limit`);
+
+    const packageFiles = [
+      { path: "SKILL.md", kind: "skill" as const, content: "ok" },
+      ...Array.from({ length: Math.ceil(MAX_TOTAL_BYTES / MAX_SKILL_FILE_BYTES) }, (_, index) => ({
+        path: `assets/chunk-${index}.bin`,
+        kind: "asset" as const,
+        content: new Uint8Array(MAX_SKILL_FILE_BYTES),
+      })),
+    ];
+    await expect(materializeSkillFiles(dir, packageFiles)).rejects.toThrow(
+      `Skill package exceeded aggregate limit of ${MAX_TOTAL_BYTES} bytes`,
+    );
+  });
+});