diff --git a/.github/workflows/apply-den-1462-export-boundaries.yml b/.github/workflows/apply-den-1462-export-boundaries.yml
new file mode 100644
index 00000000..bee30616
--- /dev/null
+++ b/.github/workflows/apply-den-1462-export-boundaries.yml
@@ -0,0 +1,56 @@
+name: apply DEN-1462 export boundaries
+
+on:
+  push:
+    branches:
+      - fix/den-1462-mise-export-boundaries
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+permissions:
+  contents: write
+
+concurrency:
+  group: den-1462-export-boundaries-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  apply:
+    if: github.actor != 'github-actions[bot]'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 35
+    steps:
+      - name: Check out stacked hardening branch
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: fix/den-1462-mise-export-boundaries
+          fetch-depth: 0
+          persist-credentials: true
+          show-progress: false
+
+      - name: Install validation toolchain
+        run: |
+          set -euo pipefail
+          rustup toolchain install stable --profile minimal --component rustfmt,clippy
+          rustup default stable
+
+      - name: Apply and validate ownership/security boundaries
+        run: |
+          set -euo pipefail
+          python3 scripts/harden_den1462_export_boundaries.py
+          cargo fmt --all
+          cargo fmt --all --check
+          git diff --check
+          cargo test --locked mise_export
+          cargo test --locked --test mise_export_cli
+          cargo clippy --locked --all-targets -- -D warnings
+
+          git config user.name 'github-actions[bot]'
+          git config user.email '41898282+github-actions[bot]@users.noreply.github.com'
+          git add src/mise_export.rs tests/mise_export_cli.rs docs/mise-export.md
+          git commit -m 'fix(DEN-1462): harden mise export ownership boundaries'
+          git push origin HEAD:fix/den-1462-mise-export-boundaries
diff --git a/scripts/harden_den1462_export_boundaries.py b/scripts/harden_den1462_export_boundaries.py
new file mode 100644
index 00000000..8aab9736
--- /dev/null
+++ b/scripts/harden_den1462_export_boundaries.py
@@ -0,0 +1,301 @@
+#!/usr/bin/env python3
+"""Temporary residual hardener applied after the base DEN-1462 materializer."""
+
+from pathlib import Path
+
+
+def replace_once(text: str, old: str, new: str, label: str) -> str:
+    count = text.count(old)
+    if count != 1:
+        raise SystemExit(f"{label}: expected one anchor, found {count}")
+    return text.replace(old, new, 1)
+
+
+source = Path("src/mise_export.rs")
+text = source.read_text(encoding="utf-8")
+
+# The base PR rejects exact aliases and transaction staging. Strengthen that
+# contract for portable case-insensitive filesystems and reserve the state path
+# for both input and output.
+old_relationships = '''fn validate_export_path_relationships(
+    plan_path: &Path,
+    plan_relative: &str,
+    output_path: &Path,
+    output_relative: &str,
+) -> Result<()> {
+    ensure!(
+        output_relative != plan_relative,
+        "mise output `{output_relative}` cannot overwrite its source environment plan"
+    );
+    ensure!(
+        output_relative != EXPORT_STATE_PATH,
+        "mise output cannot target reserved export state `{EXPORT_STATE_PATH}`"
+    );
+    let staging_prefix = format!("{STAGING_DIR}/");
+    for (kind, relative) in [
+        ("environment plan", plan_relative),
+        ("mise output", output_relative),
+    ] {
+        ensure!(
+            relative != STAGING_DIR && !relative.starts_with(&staging_prefix),
+            "{kind} cannot target reserved transaction staging `{STAGING_DIR}`: `{relative}`"
+        );
+    }
+'''
+new_relationships = '''fn validate_export_path_relationships(
+    plan_path: &Path,
+    plan_relative: &str,
+    output_path: &Path,
+    output_relative: &str,
+) -> Result<()> {
+    ensure!(
+        !portable_path_eq(output_relative, plan_relative),
+        "mise output `{output_relative}` cannot overwrite its source environment plan"
+    );
+    for (kind, relative) in [
+        ("environment plan", plan_relative),
+        ("mise output", output_relative),
+    ] {
+        ensure!(
+            !portable_path_eq(relative, EXPORT_STATE_PATH),
+            "{kind} cannot target reserved export state `{EXPORT_STATE_PATH}`"
+        );
+        ensure!(
+            !reserved_path_or_child(relative, STAGING_DIR),
+            "{kind} cannot target reserved transaction staging `{STAGING_DIR}`: `{relative}`"
+        );
+    }
+'''
+if "!portable_path_eq(output_relative, plan_relative)" not in text:
+    text = replace_once(text, old_relationships, new_relationships, "portable path relationships")
+
+if "fn portable_path_eq(" not in text:
+    anchor = "fn read_plan(path: &Path) -> Result<EnvironmentPlanV2> {\n"
+    helpers = '''fn portable_path_eq(left: &str, right: &str) -> bool {
+    left.eq_ignore_ascii_case(right)
+}
+
+fn reserved_path_or_child(path: &str, reserved: &str) -> bool {
+    portable_path_eq(path, reserved)
+        || path
+            .get(..reserved.len())
+            .is_some_and(|prefix| prefix.eq_ignore_ascii_case(reserved))
+            && path.as_bytes().get(reserved.len()) == Some(&b'/')
+}
+
+'''
+    text = replace_once(text, anchor, helpers + anchor, "portable path helpers")
+
+# Protect every existing prefix of generated files, while allowing a missing
+# safe suffix to be created within the project transaction.
+if "fn ensure_no_symlink_existing_prefix(" not in text:
+    anchor = "fn ensure_no_symlink_components(\n"
+    helper = '''fn ensure_no_symlink_existing_prefix(
+    root: &Path,
+    relative: &Path,
+    kind: &str,
+) -> Result<()> {
+    let mut current = root.to_path_buf();
+    let components = relative.components().collect::<Vec<_>>();
+    let mut suffix_missing = false;
+    for (index, component) in components.iter().enumerate() {
+        let Component::Normal(value) = component else {
+            bail!("{kind} must be normalized and project-relative");
+        };
+        current.push(value);
+        if suffix_missing {
+            continue;
+        }
+        let leaf = index + 1 == components.len();
+        match fs::symlink_metadata(&current) {
+            Ok(metadata) => {
+                ensure!(
+                    !metadata.file_type().is_symlink(),
+                    "{kind} crosses a symlink at {}",
+                    current.display()
+                );
+                if !leaf {
+                    ensure!(
+                        metadata.is_dir(),
+                        "{kind} parent is not a directory: {}",
+                        current.display()
+                    );
+                }
+            }
+            Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
+                suffix_missing = true;
+            }
+            Err(error) => {
+                return Err(error)
+                    .with_context(|| format!("failed to inspect {kind} {}", current.display()));
+            }
+        }
+    }
+    Ok(())
+}
+
+'''
+    text = replace_once(text, anchor, helper + anchor, "existing-prefix symlink helper")
+
+old_resolve = '''    let relative = validate_relative_argument(requested, kind)?;
+    ensure_no_symlink_components(root, &relative, kind, must_exist)?;
+    let path = root.join(&relative);
+'''
+new_resolve = '''    let relative = validate_relative_argument(requested, kind)?;
+    if must_exist {
+        ensure_no_symlink_components(root, &relative, kind, true)?;
+    } else {
+        ensure_no_symlink_existing_prefix(root, &relative, kind)?;
+    }
+    let path = root.join(&relative);
+'''
+if old_resolve in text:
+    text = replace_once(text, old_resolve, new_resolve, "generated path prefix validation")
+
+state_anchor = '''    let state_path = root.join(EXPORT_STATE_PATH);
+    let mut state = load_state(&state_path)?;
+'''
+state_replacement = '''    let state_path = root.join(EXPORT_STATE_PATH);
+    ensure_no_symlink_existing_prefix(
+        root,
+        Path::new(EXPORT_STATE_PATH),
+        "mise export state",
+    )?;
+    let mut state = load_state(&state_path)?;
+'''
+if "Path::new(EXPORT_STATE_PATH),\n        \"mise export state\"" not in text:
+    text = replace_once(text, state_anchor, state_replacement, "state prefix validation")
+
+# Add residual regressions not present in the base hardening.
+if "fn nested_tool_option_secrets_fail_closed()" not in text:
+    anchor = '''    #[test]
+    fn task_invocations_and_shell_argument_vectors_fail_closed() {
+'''
+    tests = '''    #[test]
+    fn nested_tool_option_secrets_fail_closed() {
+        let mut plan = simple_plan();
+        plan.tools.get_mut("node").unwrap().versions_mut()[0]
+            .options
+            .insert(
+                "config".to_string(),
+                EnvironmentValue::Table(BTreeMap::from([(
+                    "password".to_string(),
+                    EnvironmentValue::String("plaintext".to_string()),
+                )])),
+            );
+        let error = render_mise_config(&plan).unwrap_err();
+        assert!(error
+            .to_string()
+            .contains("tools.node.versions[0].options.config.password"));
+    }
+
+    #[test]
+    fn write_can_create_missing_safe_parent_directories() {
+        let temp = tempfile::tempdir().unwrap();
+        let plan_path = write_plan(temp.path(), &simple_plan());
+        let report = export_mise(
+            temp.path(),
+            &plan_path,
+            Path::new("generated/.mise.toml"),
+            MiseExportMode::Write,
+        )
+        .unwrap();
+        assert_eq!(report.action, MiseExportAction::Written);
+        assert!(temp.path().join("generated/.mise.toml").is_file());
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn export_state_rejects_symlinked_zed_directory() {
+        use std::os::unix::fs::symlink;
+
+        let temp = tempfile::tempdir().unwrap();
+        let outside = tempfile::tempdir().unwrap();
+        let plan_path = write_plan(temp.path(), &simple_plan());
+        symlink(outside.path(), temp.path().join(".zed")).unwrap();
+
+        let error = export_mise(
+            temp.path(),
+            &plan_path,
+            Path::new(".mise.toml"),
+            MiseExportMode::Write,
+        )
+        .unwrap_err();
+        assert!(error.to_string().contains("mise export state crosses a symlink"));
+        assert!(!temp.path().join(".mise.toml").exists());
+        assert!(!outside.path().join("mise-export-state.json").exists());
+    }
+
+'''
+    text = replace_once(text, anchor, tests + anchor, "residual security unit tests")
+
+source.write_text(text, encoding="utf-8")
+
+integration = Path("tests/mise_export_cli.rs")
+text = integration.read_text(encoding="utf-8")
+if "fn case_only_reserved_paths_fail_before_mutation()" not in text:
+    addition = r'''
+
+#[test]
+fn case_only_reserved_paths_fail_before_mutation() {
+    let temp = tempfile::tempdir().unwrap();
+    let home = temp.path().join("home");
+    let project = temp.path().join("project");
+    fs::create_dir_all(&home).unwrap();
+    write_plan(&project);
+    let original_plan = fs::read(project.join("zed-env.json")).unwrap();
+
+    let alias = run_zed(
+        &project,
+        &home,
+        &[
+            "env",
+            "export",
+            "mise",
+            "--plan",
+            "zed-env.json",
+            "--output",
+            "ZED-ENV.JSON",
+            "--write",
+        ],
+    );
+    assert!(!alias.status.success());
+    assert!(String::from_utf8_lossy(&alias.stderr).contains("cannot overwrite"));
+    assert_eq!(fs::read(project.join("zed-env.json")).unwrap(), original_plan);
+
+    let reserved = run_zed(
+        &project,
+        &home,
+        &[
+            "env",
+            "export",
+            "mise",
+            "--plan",
+            "zed-env.json",
+            "--output",
+            ".ZED/MISE-EXPORT-STATE.JSON",
+            "--write",
+        ],
+    );
+    assert!(!reserved.status.success());
+    assert!(String::from_utf8_lossy(&reserved.stderr).contains("reserved export state"));
+    assert!(!project.join(".zed/mise-export-state.json").exists());
+    assert!(!project.join(".ZED/MISE-EXPORT-STATE.JSON").exists());
+}
+'''
+    text += addition
+integration.write_text(text, encoding="utf-8")
+
+docs = Path("docs/mise-export.md")
+text = docs.read_text(encoding="utf-8")
+if "case-only aliases" not in text:
+    anchor = "## Fail-closed boundary\n"
+    section = '''## Portable ownership boundaries
+
+Plan, output, export-state, and transaction-staging paths are compared case-insensitively so a candidate that is safe on Linux cannot collide when checked out on a typical Windows filesystem. Generated output and export-state paths reject symlinks in every existing parent component; safe missing parent directories may still be created inside the project transaction.
+
+Sensitive-key validation remains recursive through nested vars and tool-option tables. Exact diagnostics identify the rejected nested field instead of committing plaintext.
+
+'''
+    text = replace_once(text, anchor, section + anchor, "portable ownership documentation")
+docs.write_text(text, encoding="utf-8")