diff --git a/src/git.test.ts b/src/git.test.ts
index a95a14a..b9e8083 100644
--- a/src/git.test.ts
+++ b/src/git.test.ts
@@ -4,6 +4,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { afterAll, beforeAll, describe, expect, it } from "vitest";
 import {
+  assertGitAvailable,
   buildPathspecArgs,
   ensureCommitAvailable,
   extractBranchName,
@@ -745,3 +746,35 @@ describe("merge commit handling", () => {
     });
   });
 });
+
+describe("assertGitAvailable", () => {
+  it("succeeds inside a git repository with git on PATH", () => {
+    const repo = createTempRepo();
+    try {
+      expect(() => assertGitAvailable(repo.cwd)).not.toThrow();
+    } finally {
+      rmSync(repo.cwd, { recursive: true, force: true });
+    }
+  });
+
+  it("throws when not inside a git repository", () => {
+    const cwd = mkdtempSync(join(tmpdir(), "linear-release-no-repo-"));
+    try {
+      expect(() => assertGitAvailable(cwd)).toThrow(/git repository/);
+    } finally {
+      rmSync(cwd, { recursive: true, force: true });
+    }
+  });
+
+  it("throws with a PATH hint when the git binary is missing", () => {
+    const repo = createTempRepo();
+    const originalPath = process.env.PATH;
+    process.env.PATH = "/nonexistent-linear-release-test-dir";
+    try {
+      expect(() => assertGitAvailable(repo.cwd)).toThrow(/git.*on PATH/);
+    } finally {
+      process.env.PATH = originalPath;
+      rmSync(repo.cwd, { recursive: true, force: true });
+    }
+  });
+});
diff --git a/src/git.ts b/src/git.ts
index 87d927c..aab13ec 100644
--- a/src/git.ts
+++ b/src/git.ts
@@ -30,6 +30,37 @@ export function buildPathspecArgs(includePaths: string[] | null): string {
   return `-- ${patterns.join(" ")}`;
 }
 
+/**
+ * Verifies the runtime environment can satisfy the CLI's git requirements:
+ *   1. The `git` binary is on PATH.
+ *   2. The current working directory is inside a git repository.
+ *
+ * Call once at startup, before any other git operations, so cryptic
+ * downstream failures (ENOENT, "not a git repository") become useful
+ * diagnostics for CI users.
+ */
+export function assertGitAvailable(cwd: string = process.cwd()): void {
+  try {
+    execSync("git --version", {
+      cwd,
+      stdio: ["ignore", "ignore", "pipe"],
+    });
+  } catch {
+    throw new Error(
+      "linear-release requires `git` on PATH, but `git --version` failed. Please make sure that git is installed and available.",
+    );
+  }
+
+  try {
+    execSync("git rev-parse --is-inside-work-tree", {
+      cwd,
+      stdio: ["ignore", "ignore", "pipe"],
+    });
+  } catch {
+    throw new Error("linear-release must run inside a git repository, but no `.git` directory was found.");
+  }
+}
+
 export function getCurrentGitInfo(cwd: string = process.cwd()): GitInfo {
   try {
     const branch = execSync("git rev-parse --abbrev-ref HEAD", {
diff --git a/src/index.ts b/src/index.ts
index a73b294..7d23b73 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,11 @@
 import { LinearClient, LinearClientOptions } from "@linear/sdk";
-import { ensureCommitAvailable, getCommitContextsBetweenShas, getCurrentGitInfo, getRepoInfo } from "./git";
+import {
+  assertGitAvailable,
+  ensureCommitAvailable,
+  getCommitContextsBetweenShas,
+  getCurrentGitInfo,
+  getRepoInfo,
+} from "./git";
 import { scanCommits } from "./scan";
 import {
   Release,
@@ -524,6 +530,8 @@ async function updateReleaseByPipeline(options: {
 }
 
 async function main() {
+  assertGitAvailable();
+
   let result: {
     release: { id: string; name: string; version?: string; url?: string };
   } | null = null;