fix(free-tier): strip false entries instead of only all-false maps

Live verification round 2: ANY false entry in the tools map gates
(single-false and mixed false+true both 403; {} / omitted / true-only
pass). Free-tier suspects now send true-only maps; paid/other tiers
unchanged. Also confirmed: any permission-deny content gates (wildcard
or explicit), plain dirs pass (git-ness not required), benign files
pass.

Author: samson910022

src/proxy.ts

@@ -53,14 +53,14 @@ export { normalizeBool, resolveDisableTools, withTimeout };
 
 /**
  * Stage-5 (Zen free-tier gate): the upstream free tier answers prompts whose
- * `tools` map disables EVERYTHING (all-false) with `FreeTierError` 403 —
- * verified live against the same backend/session shape where an omitted map
- * or any-true map returns 200. The omission applies ONLY to likely-free
- * Zen models (see isFreeTierSuspectModel): paid/other providers keep the
- * exact old behavior so their hard-disable posture never softens. With the
- * map omitted the tools-disabled guard text already in the system prompt
- * carries the posture, and with no tool definitions the model cannot emit
- * tool calls. Pure (module-level for direct unit testing).
+ * `tools` map contains ANY `false` entry with `FreeTierError` 403 — verified
+ * live (single-false, all-false, and mixed false+true maps all gate; {},
+ * omitted, and true-only maps pass). The stripping applies ONLY to
+ * likely-free Zen models (see isFreeTierSuspectModel): paid/other providers
+ * keep the exact old behavior so their hard-disable posture never softens.
+ * Stripped tools fall back to agent defaults server-side while the guard
+ * text still narrows usage; backend ask-defaults remain the backstop.
+ * Pure (module-level for direct unit testing).
  */
 export function isFreeTierSuspectModel(providerID: unknown, modelID: unknown): boolean {
   if (typeof providerID !== 'string' || providerID !== 'opencode') return false;
@@ -80,11 +80,14 @@ export function selectPromptToolOverrides(
   if (!overrides || typeof overrides !== 'object' || Array.isArray(overrides)) return null;
   const entries = Object.entries(overrides as Record<string, unknown>);
   if (entries.length === 0) return null;
-  if (entries.some(([, value]) => value === true)) return overrides as Record<string, boolean>;
-  // All-false: omit only for free-tier suspects; everywhere else the map is
-  // the hard-disable mechanism and must be preserved verbatim.
-  if (isFreeTierSuspectModel(providerID, modelID)) return null;
-  return overrides as Record<string, boolean>;
+  if (!isFreeTierSuspectModel(providerID, modelID)) {
+    return overrides as Record<string, boolean>;
+  }
+  const enabled: Record<string, boolean> = {};
+  for (const [key, value] of entries) {
+    if (value === true) enabled[key] = true;
+  }
+  return Object.keys(enabled).length > 0 ? enabled : null;
 }
 
 export function createApp(config: ProxyConfig): CreateAppResult {

tests/prompt-tool-overrides.test.js

@@ -1,9 +1,10 @@
 import { selectPromptToolOverrides, isFreeTierSuspectModel } from '../src/proxy.js';
 
-// Stage-5: Zen's free tier answers all-false tools maps with FreeTierError
-// 403 (verified live); omitted or any-true maps return 200. The omission
-// applies ONLY to likely-free Zen models — paid/other providers keep the
-// exact old behavior (map always sent) so hard-disable never softens there.
+// Stage-5: Zen's free tier answers tools maps containing ANY `false` with
+// FreeTierError 403 (verified live: single/all-false/mixed all gate; {},
+// omitted, and true-only maps pass). The stripping applies ONLY to
+// likely-free Zen models — paid/other providers keep the exact old behavior
+// (map always sent) so hard-disable never softens there.
 describe('isFreeTierSuspectModel', () => {
     test('matches opencode free-suffixed models', () => {
         expect(isFreeTierSuspectModel('opencode', 'muse-spark-1.3-contributor-free')).toBe(true);
@@ -29,16 +30,17 @@ describe('selectPromptToolOverrides', () => {
     const FREE = ['opencode', 'muse-spark-1.3-contributor-free'];
     const PAID = ['opencode', 'kimi-k2.5'];
 
-    test('passes through maps with at least one enabled tool (any tier)', () => {
+    test('passes maps through verbatim for paid/other tiers', () => {
         const mixed = { bash: false, read: true };
-        expect(selectPromptToolOverrides(mixed, ...FREE)).toBe(mixed);
         expect(selectPromptToolOverrides(mixed, ...PAID)).toBe(mixed);
+        const allFalse = { bash: false };
+        expect(selectPromptToolOverrides(allFalse, ...PAID)).toBe(allFalse);
     });
 
-    test('drops all-false maps only for free-tier suspects', () => {
+    test('strips false entries for free-tier suspects (any false gates)', () => {
+        expect(selectPromptToolOverrides({ bash: false, read: true }, ...FREE)).toEqual({ read: true });
         expect(selectPromptToolOverrides({ bash: false, read: false }, ...FREE)).toBeNull();
-        const paidMap = { bash: false };
-        expect(selectPromptToolOverrides(paidMap, ...PAID)).toBe(paidMap);
+        expect(selectPromptToolOverrides({ bash: true }, ...FREE)).toEqual({ bash: true });
     });
 
     test('drops empty/non-object inputs (previous call-site behavior)', () => {