diff --git a/CHANGELOG.md b/CHANGELOG.md
index 36ed547a2aa..d8a4d6497f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Security: fix Chutes manual OAuth login state validation (thanks @aether-ai-agent). (#16058)
 - macOS: hard-limit unkeyed `openclaw://agent` deep links and ignore `deliver` / `to` / `channel` unless a valid unattended key is provided. Thanks @Cillian-Collins.
 
 ## 2026.2.14
diff --git a/src/agents/chutes-oauth.test.ts b/src/agents/chutes-oauth.test.ts
new file mode 100644
index 00000000000..8ef91281ba8
--- /dev/null
+++ b/src/agents/chutes-oauth.test.ts
@@ -0,0 +1,55 @@
+import { describe, expect, it } from "vitest";
+import { generateChutesPkce, parseOAuthCallbackInput } from "./chutes-oauth.js";
+
+describe("parseOAuthCallbackInput", () => {
+  const EXPECTED_STATE = "abc123def456";
+
+  it("returns code and state for valid URL with matching state", () => {
+    const result = parseOAuthCallbackInput(
+      `http://localhost/cb?code=authcode_xyz&state=${EXPECTED_STATE}`,
+      EXPECTED_STATE,
+    );
+    expect(result).toEqual({ code: "authcode_xyz", state: EXPECTED_STATE });
+  });
+
+  it("rejects URL with mismatched state (CSRF protection)", () => {
+    const result = parseOAuthCallbackInput(
+      "http://localhost/cb?code=authcode_xyz&state=attacker_state",
+      EXPECTED_STATE,
+    );
+    expect(result).toHaveProperty("error");
+    expect((result as { error: string }).error).toMatch(/state mismatch/i);
+  });
+
+  it("rejects bare code input without fabricating state", () => {
+    const result = parseOAuthCallbackInput("bare_auth_code", EXPECTED_STATE);
+    expect(result).toHaveProperty("error");
+    expect(result).not.toHaveProperty("code");
+  });
+
+  it("rejects empty input", () => {
+    const result = parseOAuthCallbackInput("", EXPECTED_STATE);
+    expect(result).toEqual({ error: "No input provided" });
+  });
+
+  it("rejects URL missing code parameter", () => {
+    const result = parseOAuthCallbackInput(
+      `http://localhost/cb?state=${EXPECTED_STATE}`,
+      EXPECTED_STATE,
+    );
+    expect(result).toHaveProperty("error");
+  });
+
+  it("rejects URL missing state parameter", () => {
+    const result = parseOAuthCallbackInput("http://localhost/cb?code=authcode_xyz", EXPECTED_STATE);
+    expect(result).toHaveProperty("error");
+  });
+});
+
+describe("generateChutesPkce", () => {
+  it("returns verifier and challenge strings", () => {
+    const pkce = generateChutesPkce();
+    expect(pkce.verifier).toMatch(/^[0-9a-f]{64}$/);
+    expect(pkce.challenge).toBeTruthy();
+  });
+});
diff --git a/src/agents/chutes-oauth.ts b/src/agents/chutes-oauth.ts
index 63ba4e26cb8..405c3d84143 100644
--- a/src/agents/chutes-oauth.ts
+++ b/src/agents/chutes-oauth.ts
@@ -52,12 +52,12 @@ export function parseOAuthCallbackInput(
     if (!state) {
       return { error: "Missing 'state' parameter. Paste the full URL." };
     }
+    if (state !== expectedState) {
+      return { error: "OAuth state mismatch - possible CSRF attack. Please retry login." };
+    }
     return { code, state };
   } catch {
-    if (!expectedState) {
-      return { error: "Paste the full redirect URL, not just the code." };
-    }
-    return { code: trimmed, state: expectedState };
+    return { error: "Paste the full redirect URL, not just the code." };
   }
 }
 
diff --git a/src/commands/chutes-oauth.ts b/src/commands/chutes-oauth.ts
index 1925649bb4a..161ae621db0 100644
--- a/src/commands/chutes-oauth.ts
+++ b/src/commands/chutes-oauth.ts
@@ -156,7 +156,7 @@ export async function loginChutes(params: {
     await params.onAuth({ url });
     params.onProgress?.("Waiting for redirect URL…");
     const input = await params.onPrompt({
-      message: "Paste the redirect URL (or authorization code)",
+      message: "Paste the redirect URL",
       placeholder: `${params.app.redirectUri}?code=...&state=...`,
     });
     const parsed = parseOAuthCallbackInput(String(input), state);
@@ -176,7 +176,7 @@ export async function loginChutes(params: {
     }).catch(async () => {
       params.onProgress?.("OAuth callback not detected; paste redirect URL…");
       const input = await params.onPrompt({
-        message: "Paste the redirect URL (or authorization code)",
+        message: "Paste the redirect URL",
         placeholder: `${params.app.redirectUri}?code=...&state=...`,
       });
       const parsed = parseOAuthCallbackInput(String(input), state);