diff --git a/agent/agentcontainers/dcspec/dcspec_gen.go b/agent/agentcontainers/dcspec/dcspec_gen.go
index 1f0291063d..87dc3ac9f9 100644
--- a/agent/agentcontainers/dcspec/dcspec_gen.go
+++ b/agent/agentcontainers/dcspec/dcspec_gen.go
@@ -1,6 +1,30 @@
 // Code generated by dcspec/gen.sh. DO NOT EDIT.
+//
+// This file was generated from JSON Schema using quicktype, do not modify it directly.
+// To parse and unparse this JSON data, add this code to your project and do:
+//
+//    devContainer, err := UnmarshalDevContainer(bytes)
+//    bytes, err = devContainer.Marshal()
+
 package dcspec
 
+import (
+	"bytes"
+	"errors"
+)
+
+import "encoding/json"
+
+func UnmarshalDevContainer(data []byte) (DevContainer, error) {
+	var r DevContainer
+	err := json.Unmarshal(data, &r)
+	return r, err
+}
+
+func (r *DevContainer) Marshal() ([]byte, error) {
+	return json.Marshal(r)
+}
+
 // Defines a dev container
 type DevContainer struct {
 	// Docker build-related options.
@@ -284,6 +308,21 @@ type DevContainerAppPort struct {
 	UnionArray []AppPortElement
 }
 
+func (x *DevContainerAppPort) UnmarshalJSON(data []byte) error {
+	x.UnionArray = nil
+	object, err := unmarshalUnion(data, &x.Integer, nil, nil, &x.String, true, &x.UnionArray, false, nil, false, nil, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+	}
+	return nil
+}
+
+func (x *DevContainerAppPort) MarshalJSON() ([]byte, error) {
+	return marshalUnion(x.Integer, nil, nil, x.String, x.UnionArray != nil, x.UnionArray, false, nil, false, nil, false, nil, false)
+}
+
 // Application ports that are exposed by the container. This can be a single port or an
 // array of ports. Each port can be a number or a string. A number is mapped to the same
 // port on the host. A string is passed to Docker unchanged and can be used to map ports
@@ -293,6 +332,20 @@ type AppPortElement struct {
 	String  *string
 }
 
+func (x *AppPortElement) UnmarshalJSON(data []byte) error {
+	object, err := unmarshalUnion(data, &x.Integer, nil, nil, &x.String, false, nil, false, nil, false, nil, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+	}
+	return nil
+}
+
+func (x *AppPortElement) MarshalJSON() ([]byte, error) {
+	return marshalUnion(x.Integer, nil, nil, x.String, false, nil, false, nil, false, nil, false, nil, false)
+}
+
 // The image to consider as a cache. Use an array to specify multiple images.
 //
 // The name of the docker-compose file(s) used to start the services.
@@ -301,17 +354,64 @@ type CacheFrom struct {
 	StringArray []string
 }
 
+func (x *CacheFrom) UnmarshalJSON(data []byte) error {
+	x.StringArray = nil
+	object, err := unmarshalUnion(data, nil, nil, nil, &x.String, true, &x.StringArray, false, nil, false, nil, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+	}
+	return nil
+}
+
+func (x *CacheFrom) MarshalJSON() ([]byte, error) {
+	return marshalUnion(nil, nil, nil, x.String, x.StringArray != nil, x.StringArray, false, nil, false, nil, false, nil, false)
+}
+
 type ForwardPort struct {
 	Integer *int64
 	String  *string
 }
 
+func (x *ForwardPort) UnmarshalJSON(data []byte) error {
+	object, err := unmarshalUnion(data, &x.Integer, nil, nil, &x.String, false, nil, false, nil, false, nil, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+	}
+	return nil
+}
+
+func (x *ForwardPort) MarshalJSON() ([]byte, error) {
+	return marshalUnion(x.Integer, nil, nil, x.String, false, nil, false, nil, false, nil, false, nil, false)
+}
+
 type GPUUnion struct {
 	Bool     *bool
 	Enum     *GPUEnum
 	GPUClass *GPUClass
 }
 
+func (x *GPUUnion) UnmarshalJSON(data []byte) error {
+	x.GPUClass = nil
+	x.Enum = nil
+	var c GPUClass
+	object, err := unmarshalUnion(data, nil, nil, &x.Bool, nil, false, nil, true, &c, false, nil, true, &x.Enum, false)
+	if err != nil {
+		return err
+	}
+	if object {
+		x.GPUClass = &c
+	}
+	return nil
+}
+
+func (x *GPUUnion) MarshalJSON() ([]byte, error) {
+	return marshalUnion(nil, nil, x.Bool, nil, false, nil, x.GPUClass != nil, x.GPUClass, false, nil, x.Enum != nil, x.Enum, false)
+}
+
 // A command to run locally (i.e Your host machine, cloud VM) before anything else. This
 // command is run before "onCreateCommand". If this is a single string, it will be run in a
 // shell. If this is an array of strings, it will be run as a single command without shell.
@@ -349,7 +449,153 @@ type Command struct {
 	UnionMap    map[string]*CacheFrom
 }
 
+func (x *Command) UnmarshalJSON(data []byte) error {
+	x.StringArray = nil
+	x.UnionMap = nil
+	object, err := unmarshalUnion(data, nil, nil, nil, &x.String, true, &x.StringArray, false, nil, true, &x.UnionMap, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+	}
+	return nil
+}
+
+func (x *Command) MarshalJSON() ([]byte, error) {
+	return marshalUnion(nil, nil, nil, x.String, x.StringArray != nil, x.StringArray, false, nil, x.UnionMap != nil, x.UnionMap, false, nil, false)
+}
+
 type MountElement struct {
 	Mount  *Mount
 	String *string
 }
+
+func (x *MountElement) UnmarshalJSON(data []byte) error {
+	x.Mount = nil
+	var c Mount
+	object, err := unmarshalUnion(data, nil, nil, nil, &x.String, false, nil, true, &c, false, nil, false, nil, false)
+	if err != nil {
+		return err
+	}
+	if object {
+		x.Mount = &c
+	}
+	return nil
+}
+
+func (x *MountElement) MarshalJSON() ([]byte, error) {
+	return marshalUnion(nil, nil, nil, x.String, false, nil, x.Mount != nil, x.Mount, false, nil, false, nil, false)
+}
+
+func unmarshalUnion(data []byte, pi **int64, pf **float64, pb **bool, ps **string, haveArray bool, pa interface{}, haveObject bool, pc interface{}, haveMap bool, pm interface{}, haveEnum bool, pe interface{}, nullable bool) (bool, error) {
+	if pi != nil {
+		*pi = nil
+	}
+	if pf != nil {
+		*pf = nil
+	}
+	if pb != nil {
+		*pb = nil
+	}
+	if ps != nil {
+		*ps = nil
+	}
+
+	dec := json.NewDecoder(bytes.NewReader(data))
+	dec.UseNumber()
+	tok, err := dec.Token()
+	if err != nil {
+		return false, err
+	}
+
+	switch v := tok.(type) {
+	case json.Number:
+		if pi != nil {
+			i, err := v.Int64()
+			if err == nil {
+				*pi = &i
+				return false, nil
+			}
+		}
+		if pf != nil {
+			f, err := v.Float64()
+			if err == nil {
+				*pf = &f
+				return false, nil
+			}
+			return false, errors.New("Unparsable number")
+		}
+		return false, errors.New("Union does not contain number")
+	case float64:
+		return false, errors.New("Decoder should not return float64")
+	case bool:
+		if pb != nil {
+			*pb = &v
+			return false, nil
+		}
+		return false, errors.New("Union does not contain bool")
+	case string:
+		if haveEnum {
+			return false, json.Unmarshal(data, pe)
+		}
+		if ps != nil {
+			*ps = &v
+			return false, nil
+		}
+		return false, errors.New("Union does not contain string")
+	case nil:
+		if nullable {
+			return false, nil
+		}
+		return false, errors.New("Union does not contain null")
+	case json.Delim:
+		if v == '{' {
+			if haveObject {
+				return true, json.Unmarshal(data, pc)
+			}
+			if haveMap {
+				return false, json.Unmarshal(data, pm)
+			}
+			return false, errors.New("Union does not contain object")
+		}
+		if v == '[' {
+			if haveArray {
+				return false, json.Unmarshal(data, pa)
+			}
+			return false, errors.New("Union does not contain array")
+		}
+		return false, errors.New("Cannot handle delimiter")
+	}
+	return false, errors.New("Cannot unmarshal union")
+}
+
+func marshalUnion(pi *int64, pf *float64, pb *bool, ps *string, haveArray bool, pa interface{}, haveObject bool, pc interface{}, haveMap bool, pm interface{}, haveEnum bool, pe interface{}, nullable bool) ([]byte, error) {
+	if pi != nil {
+		return json.Marshal(*pi)
+	}
+	if pf != nil {
+		return json.Marshal(*pf)
+	}
+	if pb != nil {
+		return json.Marshal(*pb)
+	}
+	if ps != nil {
+		return json.Marshal(*ps)
+	}
+	if haveArray {
+		return json.Marshal(pa)
+	}
+	if haveObject {
+		return json.Marshal(pc)
+	}
+	if haveMap {
+		return json.Marshal(pm)
+	}
+	if haveEnum {
+		return json.Marshal(pe)
+	}
+	if nullable {
+		return json.Marshal(nil)
+	}
+	return nil, errors.New("Union must not be null")
+}
diff --git a/agent/agentcontainers/dcspec/dcspec_test.go b/agent/agentcontainers/dcspec/dcspec_test.go
new file mode 100644
index 0000000000..c3dae04203
--- /dev/null
+++ b/agent/agentcontainers/dcspec/dcspec_test.go
@@ -0,0 +1,148 @@
+package dcspec_test
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"slices"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/agent/agentcontainers/dcspec"
+	"github.com/coder/coder/v2/coderd/util/ptr"
+)
+
+func TestUnmarshalDevContainer(t *testing.T) {
+	t.Parallel()
+
+	type testCase struct {
+		name    string
+		file    string
+		wantErr bool
+		want    dcspec.DevContainer
+	}
+	tests := []testCase{
+		{
+			name: "minimal",
+			file: filepath.Join("testdata", "minimal.json"),
+			want: dcspec.DevContainer{
+				Image: ptr.Ref("test-image"),
+			},
+		},
+		{
+			name: "arrays",
+			file: filepath.Join("testdata", "arrays.json"),
+			want: dcspec.DevContainer{
+				Image:   ptr.Ref("test-image"),
+				RunArgs: []string{"--network=host", "--privileged"},
+				ForwardPorts: []dcspec.ForwardPort{
+					{
+						Integer: ptr.Ref[int64](8080),
+					},
+					{
+						String: ptr.Ref("3000:3000"),
+					},
+				},
+			},
+		},
+		{
+			name:    "devcontainers/template-starter",
+			file:    filepath.Join("testdata", "devcontainers-template-starter.json"),
+			wantErr: false,
+			want: dcspec.DevContainer{
+				Image:    ptr.Ref("mcr.microsoft.com/devcontainers/javascript-node:1-18-bullseye"),
+				Features: &dcspec.Features{},
+				Customizations: map[string]interface{}{
+					"vscode": map[string]interface{}{
+						"extensions": []interface{}{
+							"mads-hartmann.bash-ide-vscode",
+							"dbaeumer.vscode-eslint",
+						},
+					},
+				},
+				PostCreateCommand: &dcspec.Command{
+					String: ptr.Ref("npm install -g @devcontainers/cli"),
+				},
+			},
+		},
+	}
+
+	var missingTests []string
+	files, err := filepath.Glob("testdata/*.json")
+	require.NoError(t, err, "glob test files failed")
+	for _, file := range files {
+		if !slices.ContainsFunc(tests, func(tt testCase) bool {
+			return tt.file == file
+		}) {
+			missingTests = append(missingTests, file)
+		}
+	}
+	require.Empty(t, missingTests, "missing tests case for files: %v", missingTests)
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			data, err := os.ReadFile(tt.file)
+			require.NoError(t, err, "read test file failed")
+
+			got, err := dcspec.UnmarshalDevContainer(data)
+			if tt.wantErr {
+				require.Error(t, err, "want error but got nil")
+				return
+			}
+			require.NoError(t, err, "unmarshal DevContainer failed")
+
+			// Compare the unmarshaled data with the expected data.
+			if diff := cmp.Diff(tt.want, got); diff != "" {
+				require.Empty(t, diff, "UnmarshalDevContainer() mismatch (-want +got):\n%s", diff)
+			}
+
+			// Test that marshaling works (without comparing to original).
+			marshaled, err := got.Marshal()
+			require.NoError(t, err, "marshal DevContainer back to JSON failed")
+			require.NotEmpty(t, marshaled, "marshaled JSON should not be empty")
+
+			// Verify the marshaled JSON can be unmarshaled back.
+			var unmarshaled interface{}
+			err = json.Unmarshal(marshaled, &unmarshaled)
+			require.NoError(t, err, "unmarshal marshaled JSON failed")
+		})
+	}
+}
+
+func TestUnmarshalDevContainer_EdgeCases(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		json    string
+		wantErr bool
+	}{
+		{
+			name:    "empty JSON",
+			json:    "{}",
+			wantErr: false,
+		},
+		{
+			name:    "invalid JSON",
+			json:    "{not valid json",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := dcspec.UnmarshalDevContainer([]byte(tt.json))
+			if tt.wantErr {
+				require.Error(t, err, "want error but got nil")
+				return
+			}
+			require.NoError(t, err, "unmarshal DevContainer failed")
+		})
+	}
+}
diff --git a/agent/agentcontainers/dcspec/gen.sh b/agent/agentcontainers/dcspec/gen.sh
index c74efe2efb..276cb24cb4 100755
--- a/agent/agentcontainers/dcspec/gen.sh
+++ b/agent/agentcontainers/dcspec/gen.sh
@@ -43,7 +43,6 @@ fi
 if ! pnpm exec quicktype \
 	--src-lang schema \
 	--lang go \
-	--just-types-and-package \
 	--top-level "DevContainer" \
 	--out "${TMPDIR}/${DEST_FILENAME}" \
 	--package "dcspec" \
@@ -67,9 +66,9 @@ go run mvdan.cc/gofumpt@v0.4.0 -w -l "${TMPDIR}/${DEST_FILENAME}"
 # Add a header so that Go recognizes this as a generated file.
 if grep -q -- "\[-i extension\]" < <(sed -h 2>&1); then
 	# darwin sed
-	sed -i '' '1s/^/\/\/ Code generated by dcspec\/gen.sh. DO NOT EDIT.\n/' "${TMPDIR}/${DEST_FILENAME}"
+	sed -i '' '1s/^/\/\/ Code generated by dcspec\/gen.sh. DO NOT EDIT.\n\/\/\n/' "${TMPDIR}/${DEST_FILENAME}"
 else
-	sed -i'' '1s/^/\/\/ Code generated by dcspec\/gen.sh. DO NOT EDIT.\n/' "${TMPDIR}/${DEST_FILENAME}"
+	sed -i'' '1s/^/\/\/ Code generated by dcspec\/gen.sh. DO NOT EDIT.\n\/\/\n/' "${TMPDIR}/${DEST_FILENAME}"
 fi
 
 mv -v "${TMPDIR}/${DEST_FILENAME}" "${DEST_PATH}"
diff --git a/agent/agentcontainers/dcspec/testdata/arrays.json b/agent/agentcontainers/dcspec/testdata/arrays.json
new file mode 100644
index 0000000000..70dbda4893
--- /dev/null
+++ b/agent/agentcontainers/dcspec/testdata/arrays.json
@@ -0,0 +1,5 @@
+{
+	"image": "test-image",
+	"runArgs": ["--network=host", "--privileged"],
+	"forwardPorts": [8080, "3000:3000"]
+}
diff --git a/agent/agentcontainers/dcspec/testdata/devcontainers-template-starter.json b/agent/agentcontainers/dcspec/testdata/devcontainers-template-starter.json
new file mode 100644
index 0000000000..5400151b1d
--- /dev/null
+++ b/agent/agentcontainers/dcspec/testdata/devcontainers-template-starter.json
@@ -0,0 +1,12 @@
+{
+	"image": "mcr.microsoft.com/devcontainers/javascript-node:1-18-bullseye",
+	"features": {
+		"ghcr.io/devcontainers/features/docker-in-docker:2": {}
+	},
+	"customizations": {
+		"vscode": {
+			"extensions": ["mads-hartmann.bash-ide-vscode", "dbaeumer.vscode-eslint"]
+		}
+	},
+	"postCreateCommand": "npm install -g @devcontainers/cli"
+}
diff --git a/agent/agentcontainers/dcspec/testdata/minimal.json b/agent/agentcontainers/dcspec/testdata/minimal.json
new file mode 100644
index 0000000000..1e409346c6
--- /dev/null
+++ b/agent/agentcontainers/dcspec/testdata/minimal.json
@@ -0,0 +1 @@
+{ "image": "test-image" }