diff --git a/news/changelog-1.10.md b/news/changelog-1.10.md
index 9d45621a811..49e46868dc5 100644
--- a/news/changelog-1.10.md
+++ b/news/changelog-1.10.md
@@ -1,3 +1,7 @@
 All changes included in 1.10:
 
+## Commands
 
+### `quarto create`
+
+- ([#14250](https://github.com/quarto-dev/quarto-cli/issues/14250)): Fix `quarto create` producing read-only files when Quarto is installed via system packages (e.g., `.deb`). Files copied from installed resources now have user-write permission ensured.
diff --git a/src/command/create/artifacts/artifact-shared.ts b/src/command/create/artifacts/artifact-shared.ts
index 68fadb83295..27900fdd1f2 100644
--- a/src/command/create/artifacts/artifact-shared.ts
+++ b/src/command/create/artifacts/artifact-shared.ts
@@ -12,7 +12,11 @@ import { gfmAutoIdentifier } from "../../../core/pandoc/pandoc-id.ts";
 import { coerce } from "semver/mod.ts";
 import { info } from "../../../deno_ral/log.ts";
 import { basename, dirname, join, relative } from "../../../deno_ral/path.ts";
-import { ensureDirSync, walkSync } from "../../../deno_ral/fs.ts";
+import {
+  ensureDirSync,
+  ensureUserWritable,
+  walkSync,
+} from "../../../deno_ral/fs.ts";
 import { renderEjs } from "../../../core/ejs.ts";
 import { safeExistsSync } from "../../../core/path.ts";
 import { CreateDirective, CreateDirectiveData } from "../cmd-types.ts";
@@ -116,6 +120,7 @@ const renderArtifact = (
     }
     ensureDirSync(dirname(target));
     Deno.copyFileSync(src, target);
+    ensureUserWritable(target);
     return target;
   }
 };
diff --git a/src/deno_ral/fs.ts b/src/deno_ral/fs.ts
index 5a7dab5ec60..e6031954280 100644
--- a/src/deno_ral/fs.ts
+++ b/src/deno_ral/fs.ts
@@ -191,3 +191,15 @@ export function safeChmodSync(path: string, mode: number): void {
     }
   }
 }
+
+/**
+ * Ensure a file has user write permission. Files copied from installed
+ * resources (e.g. system packages) may be read-only, but users expect
+ * to edit files created by `quarto create`. No-op on Windows.
+ */
+export function ensureUserWritable(path: string): void {
+  const mode = safeModeFromFile(path);
+  if (mode !== undefined && !(mode & 0o200)) {
+    safeChmodSync(path, mode | 0o200);
+  }
+}
diff --git a/src/project/project-create.ts b/src/project/project-create.ts
index defec75d5e5..0b0edb4ee75 100644
--- a/src/project/project-create.ts
+++ b/src/project/project-create.ts
@@ -5,7 +5,11 @@
  */
 
 import * as ld from "../core/lodash.ts";
-import { ensureDirSync, existsSync } from "../deno_ral/fs.ts";
+import {
+  ensureDirSync,
+  ensureUserWritable,
+  existsSync,
+} from "../deno_ral/fs.ts";
 import { basename, dirname, join } from "../deno_ral/path.ts";
 import { info } from "../deno_ral/log.ts";
 
@@ -139,6 +143,7 @@ export async function projectCreate(options: ProjectCreateOptions) {
       if (!existsSync(dest)) {
         ensureDirSync(dirname(dest));
         copyTo(src, dest);
+        ensureUserWritable(dest);
         if (!options.quiet) {
           info("- Created " + displayName, { indent: 2 });
         }
@@ -256,6 +261,7 @@ function projectMarkdownFile(
       const name = basename(from);
       const target = join(dirname(path), name);
       copyTo(from, target);
+      ensureUserWritable(target);
     });
 
     return subdirectory ? join(subdirectory, name) : name;
diff --git a/tests/smoke/create/create.test.ts b/tests/smoke/create/create.test.ts
index 56f644871d2..dc685b9d492 100644
--- a/tests/smoke/create/create.test.ts
+++ b/tests/smoke/create/create.test.ts
@@ -7,6 +7,7 @@
 
 import { execProcess } from "../../../src/core/process.ts";
 import { join } from "../../../src/deno_ral/path.ts";
+import { walkSync } from "../../../src/deno_ral/fs.ts";
 import { CreateResult } from "../../../src/command/create/cmd-types.ts";
 import { assert } from "testing/asserts";
 import { quartoDevCmd } from "../../utils.ts";
@@ -61,6 +62,27 @@ for (const type of Object.keys(kCreateTypes)) {
         assert(process.success, process.stderr);
       });
 
+      // Verify all created files are user-writable.
+      // NOTE: In dev environments, resource files are already writable (0o644),
+      // so this test passes even without ensureUserWritable. It guards against
+      // regressions; the unit test in file-permissions.test.ts covers the
+      // read-only → writable transition directly.
+      await t.step({
+        name: `> check writable ${type} ${template}`,
+        ignore: Deno.build.os === "windows",
+        fn: () => {
+          for (const entry of walkSync(artifactPath)) {
+            if (entry.isFile) {
+              const stat = Deno.statSync(entry.path);
+              assert(
+                stat.mode !== null && (stat.mode! & 0o200) !== 0,
+                `File ${entry.path} is not user-writable (mode: ${stat.mode?.toString(8)})`,
+              );
+            }
+          }
+        },
+      });
+
       // Render the artifact
       await t.step(`> render ${type} ${template}`, async () => {
         const path = result!.path;
diff --git a/tests/unit/file-permissions.test.ts b/tests/unit/file-permissions.test.ts
new file mode 100644
index 00000000000..6742996455b
--- /dev/null
+++ b/tests/unit/file-permissions.test.ts
@@ -0,0 +1,81 @@
+/*
+ * file-permissions.test.ts
+ *
+ * Copyright (C) 2020-2026 Posit Software, PBC
+ */
+
+import { unitTest } from "../test.ts";
+import { withTempDir } from "../utils.ts";
+import { assert, assertEquals } from "testing/asserts";
+import { join } from "../../src/deno_ral/path.ts";
+import { isWindows } from "../../src/deno_ral/platform.ts";
+import {
+  ensureUserWritable,
+  safeModeFromFile,
+} from "../../src/deno_ral/fs.ts";
+
+function writeFile(dir: string, name: string, content: string, mode: number): string {
+  const path = join(dir, name);
+  Deno.writeTextFileSync(path, content);
+  Deno.chmodSync(path, mode);
+  return path;
+}
+
+unitTest(
+  "file-permissions - ensureUserWritable fixes read-only files",
+  async () => withTempDir((dir) => {
+    const file = writeFile(dir, "readonly.txt", "test content", 0o444);
+
+    const modeBefore = safeModeFromFile(file);
+    assert(modeBefore !== undefined);
+    assert((modeBefore! & 0o200) === 0, "File should be read-only before fix");
+
+    ensureUserWritable(file);
+
+    assertEquals(safeModeFromFile(file)! & 0o777, 0o644,
+      "Permission bits should be 0o644 (0o444 | 0o200) — only user write bit added");
+  }),
+  { ignore: isWindows },
+);
+
+unitTest(
+  "file-permissions - ensureUserWritable leaves writable files unchanged",
+  async () => withTempDir((dir) => {
+    const file = writeFile(dir, "writable.txt", "test content", 0o644);
+    const modeBefore = safeModeFromFile(file);
+    assert(modeBefore !== undefined, "Mode should be readable");
+
+    ensureUserWritable(file);
+
+    assertEquals(safeModeFromFile(file), modeBefore,
+      "Mode should be unchanged for already-writable file");
+  }),
+  { ignore: isWindows },
+);
+
+// Simulates the Nix/deb scenario: Deno.copyFileSync from a read-only source
+// preserves the read-only mode on the copy. ensureUserWritable must fix it.
+unitTest(
+  "file-permissions - copyFileSync from read-only source then ensureUserWritable",
+  async () => withTempDir((dir) => {
+    const src = writeFile(dir, "source.lua", "-- filter code", 0o444);
+
+    // Copy it (this is what quarto create does internally)
+    const dest = join(dir, "dest.lua");
+    Deno.copyFileSync(src, dest);
+
+    // Without the fix, dest inherits 0o444 from src
+    const modeBefore = safeModeFromFile(dest);
+    assert(modeBefore !== undefined);
+    assert((modeBefore! & 0o200) === 0, "Copied file should inherit read-only mode from source");
+
+    // Make source writable so cleanup succeeds
+    Deno.chmodSync(src, 0o644);
+
+    ensureUserWritable(dest);
+
+    assertEquals(safeModeFromFile(dest)! & 0o777, 0o644,
+      "Copied file should be user-writable after ensureUserWritable");
+  }),
+  { ignore: isWindows },
+);
diff --git a/tests/utils.ts b/tests/utils.ts
index 8ba0bf54ee5..eabd8344be7 100644
--- a/tests/utils.ts
+++ b/tests/utils.ts
@@ -20,6 +20,18 @@ export function inTempDirectory(fn: (dir: string) => unknown): unknown {
   return fn(dir);
 }
 
+export async function withTempDir<T>(
+  fn: (dir: string) => T | Promise<T>,
+  prefix = "quarto-test",
+): Promise<T> {
+  const dir = Deno.makeTempDirSync({ prefix });
+  try {
+    return await fn(dir);
+  } finally {
+    Deno.removeSync(dir, { recursive: true });
+  }
+}
+
 // Find a _quarto.yaml file in the directory hierarchy of the input file
 export function findProjectDir(input: string, until?: RegExp | undefined): string | undefined {
   let dir = dirname(input);