diff --git a/CHANGELOG.md b/CHANGELOG.md
index dfac6064f..216663d80 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- `apm install --target claude` now preserves self-defined stdio MCP `env` values from `apm.yml` and writes non-string values such as `PORT: 3000` and `DEBUG: false` as MCP-compatible strings. (#1222)
 - Non-skill integrators (agent, instruction, prompt, command, hook script-copy) silently adopt byte-identical pre-existing files so a degraded `deployed_files=[]` lockfile no longer permanently blocks installs gated by `required-packages-deployed`. (#1313)
 - `apm audit` drift check now returns skip-with-info (`passed=True`) when the install cache is cold, instead of failing the audit; bare `apm audit` surfaces the skip reason on stderr so CI pipelines that have not yet run `apm install` are not incorrectly red-marked. (#1289)
 - `extends: org` now correctly layers `dependencies.require` and `dependencies.deny` from the parent policy when the child omits the `dependencies:` block entirely; `None` signals "no opinion" (transparent) while `[]` signals explicit override. (#1290)
diff --git a/src/apm_cli/adapters/client/copilot.py b/src/apm_cli/adapters/client/copilot.py
index 2751a30fe..ae527f7b5 100644
--- a/src/apm_cli/adapters/client/copilot.py
+++ b/src/apm_cli/adapters/client/copilot.py
@@ -93,6 +93,13 @@ def _has_env_placeholder(value):
     return bool(_COPILOT_ENV_RE.search(value))
 
 
+def _stringify_env_literal(value):
+    """Return MCP env literal values in the manifest ``map<string, string>`` shape."""
+    if isinstance(value, bool):
+        return str(value).lower()
+    return str(value)
+
+
 class CopilotClientAdapter(MCPClientAdapter):
     """Copilot CLI implementation of MCP client adapter.
 
@@ -745,8 +752,10 @@ def _resolve_environment_variables(self, env_vars, env_overrides=None):
             for name, raw_value in env_vars.items():
                 if not name:
                     continue
+                if raw_value is None:
+                    continue
                 if not isinstance(raw_value, str):
-                    translated[name] = raw_value
+                    translated[name] = _stringify_env_literal(raw_value)
                     continue
                 if _has_env_placeholder(raw_value):
                     self._last_legacy_angle_vars.update(_extract_legacy_angle_vars(raw_value))
@@ -788,6 +797,19 @@ def _resolve_environment_variables(self, env_vars, env_overrides=None):
             self._last_env_placeholder_keys = set(placeholder_keys)
             return resolved
 
+        if isinstance(env_vars, dict):
+            resolved = {}
+            for name, value in env_vars.items():
+                if not name:
+                    continue
+                if isinstance(value, str):
+                    resolved[name] = self._resolve_env_variable(
+                        name, value, env_overrides=env_overrides
+                    )
+                elif value is not None:
+                    resolved[name] = _stringify_env_literal(value)
+            return resolved
+
         import os
         import sys
 
diff --git a/tests/unit/test_claude_mcp.py b/tests/unit/test_claude_mcp.py
index 86522e7f1..a9bc4ffcf 100644
--- a/tests/unit/test_claude_mcp.py
+++ b/tests/unit/test_claude_mcp.py
@@ -119,6 +119,36 @@ def test_update_config_tolerates_malformed_project_mcp_json(self):
         data = json.loads(self.mcp_path.read_text(encoding="utf-8"))
         self.assertIn("srv", data["mcpServers"])
 
+    def test_configure_self_defined_stdio_preserves_env(self):
+        with patch.object(self.adapter, "registry_client") as mock_registry:
+            mock_registry.find_server_by_reference.return_value = {
+                "name": "env-demo",
+                "_raw_stdio": {
+                    "command": "npx",
+                    "args": ["-y", "example-mcp"],
+                    "env": {
+                        "DEMO_ENV": "demo-value",
+                        "PORT": 3000,
+                        "DEBUG": False,
+                        "RATE": 0.5,
+                    },
+                },
+            }
+
+            ok = self.adapter.configure_mcp_server("env-demo")
+
+        self.assertTrue(ok)
+        data = json.loads(self.mcp_path.read_text(encoding="utf-8"))
+        self.assertEqual(
+            data["mcpServers"]["env-demo"]["env"],
+            {
+                "DEMO_ENV": "demo-value",
+                "PORT": "3000",
+                "DEBUG": "false",
+                "RATE": "0.5",
+            },
+        )
+
 
 class TestClaudeClientAdapterUser(unittest.TestCase):
     """User scope: ``~/.claude.json`` top-level ``mcpServers``."""
diff --git a/tests/unit/test_copilot_adapter.py b/tests/unit/test_copilot_adapter.py
index df087efe6..83f2c1e32 100644
--- a/tests/unit/test_copilot_adapter.py
+++ b/tests/unit/test_copilot_adapter.py
@@ -557,6 +557,18 @@ def test_dict_shaped_env_block_does_not_silently_drop(self):
         )
         self.assertEqual(set(result.keys()), {"FOO", "BAR"})
 
+    def test_dict_shaped_env_block_stringifies_literals_and_omits_none(self):
+        adapter = CopilotClientAdapter()
+        result = adapter._resolve_environment_variables(
+            {"PORT": 3000, "DEBUG": False, "RATE": 0.5, "OPTIONAL": None},
+            env_overrides=None,
+        )
+
+        self.assertEqual(
+            result,
+            {"PORT": "3000", "DEBUG": "false", "RATE": "0.5"},
+        )
+
 
 class TestCopilotInstallRunSummary(unittest.TestCase):
     """Issue #1152: aggregated post-install diagnostics.