diff --git a/src/apm_cli/install/helpers/security_scan.py b/src/apm_cli/install/helpers/security_scan.py
index 9cd8c6b24..76dfa1b67 100644
--- a/src/apm_cli/install/helpers/security_scan.py
+++ b/src/apm_cli/install/helpers/security_scan.py
@@ -11,6 +11,44 @@
 from apm_cli.utils.diagnostics import DiagnosticCollector
 
 
+_DEPLOYABLE_DIRS = frozenset(
+    {
+        ".apm",
+        ".github",
+        ".claude-plugin",
+        "agents",
+        "commands",
+        "context",
+        "contexts",
+        "hooks",
+        "instructions",
+        "memory",
+        "prompts",
+        "skills",
+    }
+)
+_DEPLOYABLE_NAMES = frozenset(
+    {"SKILL.md", "plugin.json", "hooks.json", ".mcp.json", "lsp.json"}
+)
+_DEPLOYABLE_SUFFIXES = (
+    ".agent.md",
+    ".instructions.md",
+    ".context.md",
+    ".memory.md",
+    ".prompt.md",
+)
+
+
+def _is_deployable_source_path(relative_path: str) -> bool:
+    """Return whether a fetched source file belongs to deployable package content."""
+    parts = tuple(part for part in relative_path.replace("\\", "/").split("/") if part)
+    if not parts:
+        return False
+    if parts[-1] in _DEPLOYABLE_NAMES or parts[-1].endswith(_DEPLOYABLE_SUFFIXES):
+        return True
+    return any(part in _DEPLOYABLE_DIRS for part in parts[:-1])
+
+
 def _pre_deploy_security_scan(
     install_path: Path,
     diagnostics: DiagnosticCollector,
@@ -29,7 +67,12 @@ def _pre_deploy_security_scan(
     """
     from apm_cli.security.gate import BLOCK_POLICY, SecurityGate
 
-    verdict = SecurityGate.scan_files(install_path, policy=BLOCK_POLICY, force=force)
+    verdict = SecurityGate.scan_files(
+        install_path,
+        policy=BLOCK_POLICY,
+        force=force,
+        path_filter=_is_deployable_source_path,
+    )
     if not verdict.has_findings:
         return True
 
@@ -41,7 +84,10 @@ def _pre_deploy_security_scan(
             logger.error(
                 f"  Blocked: {package_name or 'package'} contains critical hidden character(s)"
             )
-            logger.tree_item(f"  |-- Inspect source: {install_path}")
+            logger.tree_item(f"  |-- Source checkout: {install_path}")
+            logger.tree_item(
+                "  |-- Note: a failed install may remove this checkout during transaction cleanup"
+            )
             logger.tree_item("  |-- Use --force to deploy anyway")
         return False
 
diff --git a/src/apm_cli/security/gate.py b/src/apm_cli/security/gate.py
index c4343fa36..c304f69f4 100644
--- a/src/apm_cli/security/gate.py
+++ b/src/apm_cli/security/gate.py
@@ -81,6 +81,7 @@ def scan_files(
         *,
         policy: ScanPolicy = BLOCK_POLICY,
         force: bool = False,
+        path_filter=None,
     ) -> ScanVerdict:
         """Walk *root*, scan every regular file, return a verdict.
 
@@ -96,6 +97,8 @@ def scan_files(
                 if fpath.is_symlink():
                     continue
                 rel = portable_relpath(fpath, root)
+                if path_filter is not None and not path_filter(rel):
+                    continue
                 scanned_files.add(rel)
                 try:
                     file_findings = ContentScanner.scan_file(fpath)
diff --git a/tests/unit/install/test_security_scan_scope.py b/tests/unit/install/test_security_scan_scope.py
new file mode 100644
index 000000000..2b4955b37
--- /dev/null
+++ b/tests/unit/install/test_security_scan_scope.py
@@ -0,0 +1,29 @@
+from apm_cli.install.helpers.security_scan import _is_deployable_source_path
+
+
+def test_deployable_primitives_are_scanned():
+    deployable = [
+        "SKILL.md",
+        "plugin.json",
+        ".apm/agents/reviewer.agent.md",
+        ".github/instructions/security.instructions.md",
+        "skills/review/SKILL.md",
+        "hooks/hooks.json",
+    ]
+
+    assert all(_is_deployable_source_path(path) for path in deployable)
+
+
+def test_source_only_files_are_not_scanned_by_install_gate():
+    source_only = [
+        "src/DotnetInspector.HostileNameFixtures/HostileLiterals.cs",
+        "tests/fixtures/hostile-name.txt",
+        "docs/hostile-metadata.md",
+        "src/Program.cs",
+    ]
+
+    assert not any(_is_deployable_source_path(path) for path in source_only)
+
+
+def test_windows_paths_are_normalized():
+    assert _is_deployable_source_path(r".github\agents\reviewer.agent.md")