diff --git a/packages/cli/src/commands/adopt.js b/packages/cli/src/commands/adopt.js
index ddde44a584..3503c342e3 100644
--- a/packages/cli/src/commands/adopt.js
+++ b/packages/cli/src/commands/adopt.js
@@ -3,6 +3,7 @@ import os from 'os';
 import { E } from '@endo/far';
 import { withEndoAgent } from '../context.js';
 import { parsePetNamePath } from '../pet-name.js';
+import { parseNumber } from '../number-parse.js';
 
 export const adoptCommand = async ({
   messageNumberText,
@@ -11,7 +12,9 @@ export const adoptCommand = async ({
   agentNames,
 }) =>
   withEndoAgent(agentNames, { os, process }, async ({ agent }) => {
-    // TODO less bad number parsing.
-    const messageNumber = Number(messageNumberText);
-    await E(agent).adopt(messageNumber, edgeName, parsePetNamePath(name));
+    await E(agent).adopt(
+      parseNumber(messageNumberText),
+      edgeName,
+      parsePetNamePath(name),
+    );
   });
diff --git a/packages/cli/src/commands/reject.js b/packages/cli/src/commands/reject.js
index c8e952d15a..2e8ef2d885 100644
--- a/packages/cli/src/commands/reject.js
+++ b/packages/cli/src/commands/reject.js
@@ -2,6 +2,7 @@
 import os from 'os';
 import { E } from '@endo/far';
 import { withEndoAgent } from '../context.js';
+import { parseNumber } from '../number-parse.js';
 
 export const rejectCommand = async ({
   requestNumberText,
@@ -9,7 +10,5 @@ export const rejectCommand = async ({
   agentNames,
 }) =>
   withEndoAgent(agentNames, { os, process }, async ({ agent }) => {
-    // TODO less bad number parsing.
-    const requestNumber = Number(requestNumberText);
-    await E(agent).reject(requestNumber, message);
+    await E(agent).reject(parseNumber(requestNumberText), message);
   });
diff --git a/packages/cli/src/commands/resolve.js b/packages/cli/src/commands/resolve.js
index 7704e59612..941b1a23bf 100644
--- a/packages/cli/src/commands/resolve.js
+++ b/packages/cli/src/commands/resolve.js
@@ -2,6 +2,7 @@
 import os from 'os';
 import { E } from '@endo/far';
 import { withEndoAgent } from '../context.js';
+import { parseNumber } from '../number-parse.js';
 
 export const resolveCommand = async ({
   requestNumberText,
@@ -9,7 +10,5 @@ export const resolveCommand = async ({
   agentNames,
 }) =>
   withEndoAgent(agentNames, { os, process }, async ({ agent }) => {
-    // TODO less bad number parsing.
-    const requestNumber = Number(requestNumberText);
-    await E(agent).resolve(requestNumber, resolutionName);
+    await E(agent).resolve(parseNumber(requestNumberText), resolutionName);
   });
diff --git a/packages/cli/src/number-parse.js b/packages/cli/src/number-parse.js
new file mode 100644
index 0000000000..37f5cedb2d
--- /dev/null
+++ b/packages/cli/src/number-parse.js
@@ -0,0 +1,15 @@
+/**
+ * Parses the input and returns it as a number if it's valid, otherwise throws error.
+ *
+ * @param {string | number} input
+ * @returns {number | undefined}
+ */
+export const parseNumber = (input = '') => {
+  const result = /[0-9]/.test(input) ? Number(input) : NaN;
+
+  if (Number.isNaN(result)) {
+    throw new Error(`Invalid number: ${input}`);
+  }
+
+  return result;
+};
diff --git a/packages/cli/test/number-parse.test.js b/packages/cli/test/number-parse.test.js
new file mode 100644
index 0000000000..2013c78cf7
--- /dev/null
+++ b/packages/cli/test/number-parse.test.js
@@ -0,0 +1,67 @@
+import test from 'ava';
+import { parseNumber } from '../src/number-parse.js';
+
+// Test for valid number input
+test('returns the number itself if input is a valid number', t => {
+  t.is(parseNumber(42), 42);
+  t.is(parseNumber(-42), -42);
+  t.is(parseNumber(0), 0);
+  t.is(parseNumber(3.14), 3.14);
+  t.is(parseNumber(-3.14), -3.14);
+});
+
+// Test for valid string input (includes binary, octal and hexadecimal)
+test('returns the number when input is a valid numeric string', t => {
+  t.is(parseNumber('42'), 42);
+  t.is(parseNumber('-40.0'), -40.0);
+  t.is(parseNumber('.5'), 0.5);
+  t.is(parseNumber('1.337e3'), 1337);
+  t.is(parseNumber(' +1 '), 1);
+  t.is(parseNumber('0B111'), 7);
+  t.is(parseNumber('0o040'), 32);
+  t.is(parseNumber('0xf00'), 3840);
+  t.is(parseNumber('   -40.0   '), -40.0);
+  // Test for binary, octal and hexadecimal
+  t.is(parseNumber('0B111'), 7);
+  t.is(parseNumber('0o040'), 32);
+  t.is(parseNumber('0xf00'), 3840);
+});
+
+// Test for invalid string input
+test('throws an error when input is not a valid numeric string', t => {
+  const error = t.throws(() => parseNumber('f00'));
+  t.is(error.message, 'Invalid number: f00');
+
+  const error2 = t.throws(() => parseNumber('NaN'));
+  t.is(error2.message, 'Invalid number: NaN');
+
+  const error3 = t.throws(() => parseNumber('Infinity'));
+  t.is(error3.message, 'Invalid number: Infinity');
+
+  const error4 = t.throws(() => parseNumber('7up'));
+  t.is(error4.message, 'Invalid number: 7up');
+
+  const error5 = t.throws(() => parseNumber(' ')); // Unicode character
+  t.is(error5.message, 'Invalid number:  ');
+
+  const error6 = t.throws(() => parseNumber(''));
+  t.is(error6.message, 'Invalid number: ');
+
+  const error7 = t.throws(() => parseNumber('   '));
+  t.is(error7.message, 'Invalid number:    ');
+});
+
+// Test for invalid input
+test('throws an error when input is not a valid number', t => {
+  const error1 = t.throws(() => parseNumber(null));
+  t.is(error1.message, 'Invalid number: null');
+
+  const error2 = t.throws(() => parseNumber(undefined));
+  t.is(error2.message, 'Invalid number: ');
+
+  const error3 = t.throws(() => parseNumber({}));
+  t.is(error3.message, 'Invalid number: [object Object]');
+
+  const error4 = t.throws(() => parseNumber([]));
+  t.is(error4.message, 'Invalid number: ');
+});