diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3eeb679..f645cc7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,8 @@
 ## [2.1.1](https://github.com/filipo11021/nodejs-password-hashing/compare/v2.1.0...v2.1.1) (2026-01-26)
 
-
 ### Bug Fixes
 
-* **#26:** downgrade @types/node to v24 and lock in dependabot ([#37](https://github.com/filipo11021/nodejs-password-hashing/issues/37)) ([dcfd6d7](https://github.com/filipo11021/nodejs-password-hashing/commit/dcfd6d77ab1c0e72cacbee17599154108101a3cc)), closes [#26](https://github.com/filipo11021/nodejs-password-hashing/issues/26) [#26](https://github.com/filipo11021/nodejs-password-hashing/issues/26)
+- **#26:** downgrade @types/node to v24 and lock in dependabot ([#37](https://github.com/filipo11021/nodejs-password-hashing/issues/37)) ([dcfd6d7](https://github.com/filipo11021/nodejs-password-hashing/commit/dcfd6d77ab1c0e72cacbee17599154108101a3cc)), closes [#26](https://github.com/filipo11021/nodejs-password-hashing/issues/26) [#26](https://github.com/filipo11021/nodejs-password-hashing/issues/26)
 
 # [2.1.0](https://github.com/filipo11021/nodejs-password-hashing/compare/v2.0.0...v2.1.0) (2026-01-23)
 
diff --git a/src/argon2/argon2-validation.test.ts b/src/argon2/argon2-validation.test.ts
new file mode 100644
index 0000000..f7ac380
--- /dev/null
+++ b/src/argon2/argon2-validation.test.ts
@@ -0,0 +1,149 @@
+import { createArgon2Hashing } from "./argon2.ts";
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+
+void describe("Argon2 Parameter Validation - RFC 9106 Compliance", () => {
+  void describe("parallelism parameter", () => {
+    void it("should accept parallelism = 1 (minimum per RFC 9106)", () => {
+      assert.doesNotThrow(() => {
+        createArgon2Hashing({
+          parallelism: 1,
+          memory: 8,
+        });
+      }, "parallelism = 1 should be valid per RFC 9106");
+    });
+
+    void it("should reject parallelism = 0 (below minimum)", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            parallelism: 0,
+            memory: 8,
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "parallelism must be at least 1",
+      );
+    });
+  });
+
+  void describe("tagLength parameter", () => {
+    void it("should accept tagLength = 4 (minimum per RFC 9106)", () => {
+      assert.doesNotThrow(() => {
+        createArgon2Hashing({
+          tagLength: 4,
+        });
+      }, "tagLength = 4 should be valid per RFC 9106");
+    });
+
+    void it("should reject tagLength = 3 (below minimum)", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            tagLength: 3,
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "tagLength must be at least 4",
+      );
+    });
+  });
+
+  void describe("memory parameter relative to parallelism", () => {
+    void it("should accept memory = 8 * parallelism (minimum per RFC 9106)", () => {
+      assert.doesNotThrow(() => {
+        createArgon2Hashing({
+          parallelism: 2,
+          memory: 16, // Exactly 8 * 2
+        });
+      }, "memory = 8 * parallelism should be valid per RFC 9106");
+    });
+
+    void it("should reject memory < 8 * parallelism (below minimum)", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            parallelism: 2,
+            memory: 15, // Less than 8 * 2
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "memory must be at least 8 * parallelism",
+      );
+    });
+  });
+
+  void describe("passes parameter", () => {
+    void it("should accept passes = 1 (minimum per RFC 9106)", () => {
+      assert.doesNotThrow(() => {
+        createArgon2Hashing({
+          passes: 1,
+        });
+      }, "passes = 1 should be valid per RFC 9106");
+    });
+
+    void it("should reject passes = 0 (below minimum)", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            passes: 0,
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "passes must be at least 1",
+      );
+    });
+  });
+
+  void describe("edge cases - absolute minimums", () => {
+    void it("should accept absolute minimum configuration (parallelism=1, memory=8)", () => {
+      assert.doesNotThrow(() => {
+        createArgon2Hashing({
+          parallelism: 1,
+          memory: 8, // Exactly 8 * 1
+          passes: 1,
+          tagLength: 4,
+        });
+      }, "absolute minimum configuration should be valid per RFC 9106");
+    });
+
+    void it("should reject memory = 7 when parallelism = 1", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            parallelism: 1,
+            memory: 7,
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "memory = 7 should be rejected when parallelism = 1",
+      );
+    });
+  });
+
+  void describe("edge cases - invalid values", () => {
+    void it("should reject negative values", () => {
+      assert.throws(
+        () => {
+          createArgon2Hashing({
+            passes: -1,
+          });
+        },
+        {
+          name: "ZodError",
+        },
+        "passes must be positive",
+      );
+    });
+  });
+});
diff --git a/src/argon2/argon2.ts b/src/argon2/argon2.ts
index ace2336..6dd495e 100644
--- a/src/argon2/argon2.ts
+++ b/src/argon2/argon2.ts
@@ -12,7 +12,7 @@ import { MAX_UINT24, MAX_UINT32 } from "../utils/numbers.ts";
 const optionsSchema = z
   .object({
     memory: z.number().max(MAX_UINT32),
-    passes: z.number().min(2).max(MAX_UINT32),
+    passes: z.number().min(1).max(MAX_UINT32),
     parallelism: z.number().min(1).max(MAX_UINT24),
     tagLength: z.number().min(4).max(MAX_UINT32),
     saltLength: z.number().min(16).max(1024),
@@ -23,7 +23,8 @@ const optionsSchema = z
       return params.memory >= 8 * params.parallelism;
     },
     {
-      message: "memory parameter must be at least 8 * parallelism",
+      message:
+        "memory parameter must be greater than or equal to 8 * parallelism",
     },
   )
   .readonly();