diff --git a/CHANGELOG.md b/CHANGELOG.md
index 59a2224..1bc00af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ All notable changes to this project are documented here, following
 
 ### Fixed
 
+- Reject non-finite and negative numeric CLI options instead of scanning with
+  invalid thresholds or silently ignoring invalid waste gates.
 - Reject unknown `--targets` values with a clear error instead of silently
   skipping all ignore-file writes.
 
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..f51e515
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,19 @@
+{
+  "name": "ctxtrim",
+  "version": "0.1.3",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "ctxtrim",
+      "version": "0.1.3",
+      "license": "MIT",
+      "bin": {
+        "ctxtrim": "bin/ctxtrim.js"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    }
+  }
+}
diff --git a/src/cli.js b/src/cli.js
index 200b096..c357b08 100644
--- a/src/cli.js
+++ b/src/cli.js
@@ -37,26 +37,41 @@ function parse(argv) {
   for (let i = 0; i < argv.length; i++) {
     const a = argv[i];
     const val = () => (a.includes("=") ? a.split("=")[1] : argv[++i]);
+    const has = (name) => a === name || a.startsWith(`${name}=`);
     if (a === "-h" || a === "--help") o.help = true;
     else if (a === "-v" || a === "--version") o.version = true;
     else if (a === "--write") o.write = true;
-    else if (a.startsWith("--targets")) o.targets = val();
-    else if (a.startsWith("--price")) o.price = Number(val());
-    else if (a.startsWith("--max-tokens")) o.maxTokens = Number(val());
-    else if (a.startsWith("--top")) o.top = Number(val());
-    else if (a.startsWith("--format")) o.format = val();
-    else if (a.startsWith("--fail-on-waste")) o.failOnWaste = Number(val());
+    else if (has("--targets")) o.targets = val();
+    else if (has("--price")) o.price = Number(val());
+    else if (has("--max-tokens")) o.maxTokens = Number(val());
+    else if (has("--top")) o.top = Number(val());
+    else if (has("--format")) o.format = val();
+    else if (has("--fail-on-waste")) o.failOnWaste = Number(val());
     else if (!a.startsWith("-")) o.path = a;
   }
   return o;
 }
 
+function numericOptionError(o) {
+  if (!Number.isFinite(o.price) || o.price < 0)
+    return "ctxtrim: invalid --price: expected a non-negative number\n";
+  if (!Number.isFinite(o.maxTokens) || o.maxTokens < 0)
+    return "ctxtrim: invalid --max-tokens: expected a non-negative number\n";
+  if (!Number.isInteger(o.top) || o.top < 0)
+    return "ctxtrim: invalid --top: expected a non-negative integer\n";
+  if (o.failOnWaste != null && (!Number.isFinite(o.failOnWaste) || o.failOnWaste < 0 || o.failOnWaste > 100))
+    return "ctxtrim: invalid --fail-on-waste: expected a percentage from 0 to 100\n";
+  return null;
+}
+
 export function run(argv, { version }) {
   const o = parse(argv);
   if (o.help) { process.stdout.write(HELP); return 0; }
   if (o.version) { process.stdout.write(version + "\n"); return 0; }
   const target = o.path || ".";
   if (!existsSync(target)) { process.stderr.write(`ctxtrim: path not found: ${target}\n`); return 2; }
+  const numberError = numericOptionError(o);
+  if (numberError) { process.stderr.write(numberError); return 2; }
   if (!["text", "json"].includes(o.format)) { process.stderr.write(`ctxtrim: unknown --format\n`); return 2; }
   const targets = o.targets.split(",").map((s) => s.trim()).filter(Boolean);
   const unknownTargets = targets.filter((s) => !TARGETS[s]);
diff --git a/test/ctxtrim.test.js b/test/ctxtrim.test.js
index 6afc630..b03da1b 100644
--- a/test/ctxtrim.test.js
+++ b/test/ctxtrim.test.js
@@ -1,5 +1,4 @@
-import fs, { mkdtempSync, rmSync, truncateSync, writeFileSync } from "node:fs";
-import { existsSync } from "node:fs";
+import fs, { existsSync, mkdtempSync, rmSync, truncateSync, writeFileSync } from "node:fs";
 import { spawnSync } from "node:child_process";
 import { syncBuiltinESMExports } from "node:module";
 import { tmpdir } from "node:os";
@@ -137,6 +136,23 @@ test("clean repo (only source) reports nothing to trim", () => {
   assert.equal(s.totals.trimTokens, 0);
 });
 
+test("CLI rejects non-finite and negative numeric options", () => {
+  const invalid = [
+    ["--max-tokens", "abc"],
+    ["--max-tokens", "-5"],
+    ["--price", "-3"],
+    ["--top", "-1"],
+    ["--fail-on-waste", "abc"],
+    ["--fail-on-waste", "-1"],
+  ];
+
+  for (const args of invalid) {
+    const result = spawnSync(process.execPath, [cli, repo, ...args], { encoding: "utf8" });
+    assert.equal(result.status, 2, `${args.join(" ")} should fail with exit 2\n${result.stderr}`);
+    assert.match(result.stderr, /ctxtrim: invalid --/);
+  }
+});
+
 test("unknown --targets values fail before writing ignore files", (t) => {
   const root = mkdtempSync(join(tmpdir(), "ctxtrim-invalid-target-"));
   t.after(() => rmSync(root, { recursive: true, force: true }));