diff --git a/internal/librariangen/go.mod b/internal/librariangen/go.mod
index 52d7daf52b..87e854c400 100644
--- a/internal/librariangen/go.mod
+++ b/internal/librariangen/go.mod
@@ -1,3 +1,5 @@
 module cloud.google.com/java/internal/librariangen
 
 go 1.24.4
+
+require github.com/google/go-cmp v0.7.0 // indirect
diff --git a/internal/librariangen/go.sum b/internal/librariangen/go.sum
new file mode 100644
index 0000000000..40e761ae7c
--- /dev/null
+++ b/internal/librariangen/go.sum
@@ -0,0 +1,2 @@
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
diff --git a/internal/librariangen/request/request.go b/internal/librariangen/request/request.go
new file mode 100644
index 0000000000..72734e1edc
--- /dev/null
+++ b/internal/librariangen/request/request.go
@@ -0,0 +1,78 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package request
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+// Library is the combination of all the fields used by CLI requests and responses.
+// Each CLI command has its own request/response type, but they all use Library.
+type Library struct {
+	ID      string `json:"id,omitempty"`
+	Version string `json:"version,omitempty"`
+	APIs    []API  `json:"apis,omitempty"`
+	// SourcePaths are the directories to which librarian contributes code.
+	// For Go, this is typically the Go module directory.
+	SourcePaths []string `json:"source_roots,omitempty"`
+	// PreserveRegex are files/directories to leave untouched during generation.
+	// This is useful for preserving handwritten helper files or customizations.
+	PreserveRegex []string `json:"preserve_regex,omitempty"`
+	// RemoveRegex are files/directories to remove during generation.
+	RemoveRegex []string `json:"remove_regex,omitempty"`
+	// Changes are the changes being released (in a release request)
+	Changes []*Change `json:"changes,omitempty"`
+	// Specifying a tag format allows librarian to honor this format when creating
+	// a tag for the release of the library. The replacement values of {id} and {version}
+	// permitted to reference the values configured in the library. If not specified
+	// the assumed format is {id}-{version}. e.g., {id}/v{version}.
+	TagFormat string `yaml:"tag_format,omitempty" json:"tag_format,omitempty"`
+	// ReleaseTriggered indicates whether this library is being released (in a release request)
+	ReleaseTriggered bool `json:"release_triggered,omitempty"`
+}
+
+// API corresponds to a single API definition within a librarian request/response.
+type API struct {
+	Path          string `json:"path,omitempty"`
+	ServiceConfig string `json:"service_config,omitempty"`
+}
+
+// Change represents a single commit change for a library.
+type Change struct {
+	Type             string `json:"type"`
+	Subject          string `json:"subject"`
+	Body             string `json:"body"`
+	PiperCLNumber    string `json:"piper_cl_number"`
+	SourceCommitHash string `json:"source_commit_hash"`
+}
+
+// ParseLibrary reads a file from the given path and unmarshals
+// it into a Library struct. This is used for build and generate, where the requests
+// are simply the library, with no wrapping.
+func ParseLibrary(path string) (*Library, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("librariangen: failed to read request file from %s: %w", path, err)
+	}
+
+	var req Library
+	if err := json.Unmarshal(data, &req); err != nil {
+		return nil, fmt.Errorf("librariangen: failed to unmarshal request file %s: %w", path, err)
+	}
+
+	return &req, nil
+}
\ No newline at end of file
diff --git a/internal/librariangen/request/request_test.go b/internal/librariangen/request/request_test.go
new file mode 100644
index 0000000000..03f05b2b23
--- /dev/null
+++ b/internal/librariangen/request/request_test.go
@@ -0,0 +1,98 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package request
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestParseLibrary(t *testing.T) {
+	testCases := []struct {
+		name    string
+		content string
+		want    *Library
+		wantErr bool
+	}{
+		{
+			name: "valid request",
+			content: `{
+				"id": "asset",
+				"version": "1.15.0",
+				"apis": [
+					{
+						"path": "google/cloud/asset/v1",
+						"service_config": "cloudasset_v1.yaml"
+					}
+				],
+				"source_roots": ["asset/apiv1"],
+				"preserve_regex": ["asset/apiv1/foo.go"],
+				"remove_regex": ["asset/apiv1/bar.go"]
+			}`,
+			want: &Library{
+				ID:      "asset",
+				Version: "1.15.0",
+				APIs: []API{
+					{
+						Path:          "google/cloud/asset/v1",
+						ServiceConfig: "cloudasset_v1.yaml",
+					},
+				},
+				SourcePaths:   []string{"asset/apiv1"},
+				PreserveRegex: []string{"asset/apiv1/foo.go"},
+				RemoveRegex:   []string{"asset/apiv1/bar.go"},
+			},
+			wantErr: false,
+		},
+		{
+			name:    "malformed json",
+			content: `{"id": "foo",`,
+			wantErr: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			tmpDir := t.TempDir()
+			reqPath := filepath.Join(tmpDir, "generate-request.json")
+			if err := os.WriteFile(reqPath, []byte(tc.content), 0644); err != nil {
+				t.Fatalf("failed to write test file: %v", err)
+			}
+
+			got, err := ParseLibrary(reqPath)
+
+			if (err != nil) != tc.wantErr {
+				t.Errorf("Parse() error = %v, wantErr %v", err, tc.wantErr)
+				return
+			}
+
+			if !tc.wantErr {
+				if diff := cmp.Diff(tc.want, got); diff != "" {
+					t.Errorf("Parse() mismatch (-want +got):\n%s", diff)
+				}
+			}
+		})
+	}
+}
+
+func TestParseLibrary_FileNotFound(t *testing.T) {
+	_, err := ParseLibrary("non-existent-file.json")
+	if err == nil {
+		t.Error("Parse() expected error for non-existent file, got nil")
+	}
+}
\ No newline at end of file