diff --git a/README.md b/README.md
index c5b0f19..a6d2df4 100644
--- a/README.md
+++ b/README.md
@@ -76,6 +76,7 @@ navigation.
 | `--compare <ref>` | Compare ref to diff against `--base` |
 | `--ref <mode>` | Diff scope: `work` (staged + unstaged + untracked), `staged`, or `unstaged` (default: auto-detect) |
 | `--pr <number-or-url>` | Review a GitHub pull request by number or URL (requires `gh`) |
+| `--validate` | Validate chapters without starting the server or opening the browser |
 | `--instructions <text>` | One-off instructions for chapter generation (up to 1000 characters; `prep` command) |
 
 Examples:
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index af65cd3..e26ae66 100644
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -8,7 +8,7 @@ import {
 	toDiffScopeOptions,
 } from "./diff-scope-options.js";
 import { runPrep } from "./prep.js";
-import { show } from "./show.js";
+import { show, validate } from "./show.js";
 
 const require = createRequire(import.meta.url);
 const { version } = require("../package.json") as { version: string };
@@ -45,10 +45,17 @@ addDiffScopeOptions(
 	program
 		.command("show")
 		.description("Load a chapters.json file and open it in a local browser")
-		.argument("<path>", "Path to a chapters.json file"),
-).action(async (jsonPath: string, refs: string[], opts: DiffCommandOptions) => {
-	await show(jsonPath, toDiffScopeOptions(refs, opts));
-});
+		.argument("<path>", "Path to a chapters.json file")
+		.option("--validate", "Validate chapters without starting the server or opening the browser"),
+).action(
+	async (jsonPath: string, refs: string[], opts: DiffCommandOptions & { validate?: boolean }) => {
+		if (opts.validate) {
+			await validate(jsonPath, toDiffScopeOptions(refs, opts));
+		} else {
+			await show(jsonPath, toDiffScopeOptions(refs, opts));
+		}
+	},
+);
 
 program.addCommand(commentsCommand());
 
diff --git a/packages/cli/src/show.ts b/packages/cli/src/show.ts
index f713fd2..33d12b0 100644
--- a/packages/cli/src/show.ts
+++ b/packages/cli/src/show.ts
@@ -79,6 +79,10 @@ export async function show(jsonPath: string, options: DiffScopeOptions): Promise
 	closeDb();
 }
 
+export async function validate(jsonPath: string, options: DiffScopeOptions): Promise<void> {
+	await buildChaptersFile(jsonPath, options);
+}
+
 interface BuiltChaptersFile {
 	chaptersFile: ChaptersFile;
 	/** The reviewed PR's number when `--pr` was used, else null. */