diff --git a/src/core.ts b/src/core.ts
index 7826c69..41dcf02 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -1,3 +1,4 @@
+import * as fs from "node:fs";
 import * as path from "node:path";
 import { buildProgramGraphs, startExtraction } from "./dataflow";
 import { type LinkerResolutions, mergeCallGraphs, runDefuseLinker, tscProvider } from "./semantic_analysis";
@@ -25,11 +26,33 @@ export type { AnalysisResult } from "./schema/emit";
  * Shard enumeration for an orchestrator: it must be able to find the shards before running them.
  */
 export function discoverPrograms(opts: AnalysisOptions): string[] {
+  assertInputDir(opts.input);
   const log = new Logger(opts.verbosity);
   return materialize(opts, log).programs.map((spec) => programName(spec, opts.input));
 }
 
+/** A user-facing usage error (bad input path): printed as one line, exit 1, no stack, no FATAL. */
+export class InputError extends Error {}
+
+/**
+ * #181: the input must be a readable directory BEFORE anything runs. Discovery swallows a failed
+ * `readdir` and returns no files, which used to turn a mistyped path into a schema-valid
+ * `analysis.json` describing an empty application (id minted from a directory never read) and an
+ * exit code of 0. An empty directory is still a real answer — "no analysable sources" — this only
+ * refuses a path that is not one.
+ */
+function assertInputDir(input: string): void {
+  let stat: fs.Stats;
+  try {
+    stat = fs.statSync(input);
+  } catch {
+    throw new InputError(`input path does not exist: ${input}`);
+  }
+  if (!stat.isDirectory()) throw new InputError(`input path is not a directory: ${input}`);
+}
+
 export async function analyze(opts: AnalysisOptions): Promise<AnalysisResult> {
+  assertInputDir(opts.input);
   const log = new Logger(opts.verbosity);
   log.info(`analyzing ${opts.input} (level ${opts.analysisLevel})`);
   resetCheckerFailures();
diff --git a/src/index.ts b/src/index.ts
index a135bf7..437c7e3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,5 @@
 #!/usr/bin/env node
-import { analyze, discoverPrograms } from "./core";
+import { InputError, analyze, discoverPrograms } from "./core";
 import { parseArgs } from "./cli";
 import { RulesError } from "./entrypoints";
 import { emit, emitSchema } from "./utils";
@@ -19,7 +19,7 @@ async function main(): Promise<void> {
     const result = await analyze(opts);
     await emit(result.application, opts);
   } catch (e) {
-    if (e instanceof RulesError) {
+    if (e instanceof RulesError || e instanceof InputError) {
       // A user configuration error, not an analyzer bug: no stack trace, no "FATAL".
       process.stderr.write(`[codeanalyzer-ts] ${e.message}\n`);
       process.exit(1);
diff --git a/test/input-path.test.ts b/test/input-path.test.ts
new file mode 100644
index 0000000..ffbaa74
--- /dev/null
+++ b/test/input-path.test.ts
@@ -0,0 +1,62 @@
+/**
+ * #181 — a missing or non-directory `--input` is an error, not an empty application.
+ *
+ * Discovery used to swallow the `readdir` failure and return no files, so the analyzer wrote a
+ * schema-valid `analysis.json` describing an empty application (its id derived from a path that
+ * was never read) and exited 0. A consumer running this as a subprocess has only the exit code
+ * as a cheap health signal, and "the input did not exist" must never read as "this project has
+ * no analysable sources".
+ */
+import { describe, expect, test } from "bun:test";
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { InputError, analyze, discoverPrograms } from "../src/core";
+import type { AnalysisOptions } from "../src/options";
+
+const ROOT = path.resolve(import.meta.dir, "..");
+const MISSING = path.join(os.tmpdir(), "cants-181-does-not-exist");
+const FILE = path.join(os.tmpdir(), "cants-181-a-file.ts");
+fs.writeFileSync(FILE, "export const x = 1;");
+
+function cli(args: string[]): { code: number; stderr: string } {
+  const p = Bun.spawnSync(["bun", "run", path.join(ROOT, "src/index.ts"), ...args], { cwd: ROOT, stdout: "pipe", stderr: "pipe" });
+  return { code: p.exitCode, stderr: p.stderr.toString() };
+}
+
+describe("#181 input path", () => {
+  test("analyze() refuses a nonexistent input with a usage error naming the path", async () => {
+    const opts = { input: MISSING, appName: "x", analysisLevel: 1, noBuild: true, emit: "json" } as unknown as AnalysisOptions;
+    await expect(analyze(opts)).rejects.toBeInstanceOf(InputError);
+    await expect(analyze(opts)).rejects.toThrow(MISSING);
+  });
+
+  test("a file, not a directory, is refused the same way", async () => {
+    const opts = { input: FILE, appName: "x", analysisLevel: 1, noBuild: true, emit: "json" } as unknown as AnalysisOptions;
+    await expect(analyze(opts)).rejects.toBeInstanceOf(InputError);
+  });
+
+  test("--list-programs refuses too (it walks the same root)", () => {
+    expect(() => discoverPrograms({ input: MISSING, verbosity: 0 } as unknown as AnalysisOptions)).toThrow(InputError);
+  });
+
+  test("CLI: exit 1, one-line message, no FATAL, and nothing written", () => {
+    const out = fs.mkdtempSync(path.join(os.tmpdir(), "cants-181-out-"));
+    fs.rmSync(out, { recursive: true });
+    const r = cli(["-i", MISSING, "-o", out]);
+    expect(r.code).toBe(1);
+    expect(r.stderr).toContain("[codeanalyzer-ts]");
+    expect(r.stderr).toContain(MISSING);
+    expect(r.stderr).not.toContain("FATAL");
+    expect(fs.existsSync(path.join(out, "analysis.json"))).toBe(false);
+  });
+
+  test("CLI: an empty but real directory is a real answer — exit 0, empty symbol table", () => {
+    const empty = fs.mkdtempSync(path.join(os.tmpdir(), "cants-181-empty-"));
+    const out = path.join(empty, "out");
+    const r = cli(["-i", empty, "-o", out, "-a", "1", "--no-build", "--app-name", "e"]);
+    expect(r.code).toBe(0);
+    const j = JSON.parse(fs.readFileSync(path.join(out, "analysis.json"), "utf8"));
+    expect(j.application.symbol_table).toEqual({});
+  });
+});