Merge remote-tracking branch 'origin/master' into gitea/feature/end

Resolved conflicts taking origin/master (v0.5.55) as canonical, with local
features re-applied:
- runtime log level (LOG_LEVEL env + dashboard Settings → Logging, applied
  immediately and persisted across restarts)
- free/noAuth provider enable/disable toggle via providerStrategies.enabled
- parallel model testing (Test All Models / Test Selected Keys)

open-sse/providers/shared.js

@@ -47,6 +47,26 @@ export const CLAUDE_CLI_SPOOF_HEADERS = {
   "X-Stainless-Timeout": "600"
 };
 
+const ANTHROPIC_BETA_BASE = [
+  "claude-code-20250219",
+  "oauth-2025-04-20",
+  "interleaved-thinking-2025-05-14",
+  "context-management-2025-06-27",
+  "prompt-caching-scope-2026-01-05",
+  "structured-outputs-2025-12-15",
+  "fast-mode-2026-02-01",
+  "redact-thinking-2026-02-12",
+  "token-efficient-tools-2026-03-28",
+];
+const ANTHROPIC_BETA_HEAVY_AGENT = ["advanced-tool-use-2025-11-20", "effort-2025-11-24"];
+
+// Heavy-agent beta flags are gated to opus/sonnet — cheaper models don't need them.
+export function selectAnthropicBeta(model = "") {
+  const flags = [...ANTHROPIC_BETA_BASE];
+  if (/^claude-(opus|sonnet)/.test(model)) flags.push(...ANTHROPIC_BETA_HEAVY_AGENT);
+  return flags.join(",");
+}
+
 // Shared baseUrls
 export const KIMI_CODING_BASE_URL = "https://api.kimi.com/coding/v1/messages";
 
@@ -54,6 +74,13 @@ export const KIMI_CODING_BASE_URL = "https://api.kimi.com/coding/v1/messages";
 export const OPENAI_COMPAT_BASE = "https://api.openai.com/v1";
 export const ANTHROPIC_COMPAT_BASE = "https://api.anthropic.com/v1";
 
+// Official Antigravity IDE Desktop 2.1.1 fingerprint captured from macOS arm64.
+// Keep this static even when 9router runs on Linux: the provider profile is
+// intentionally matching the IDE client, not the server host.
+export const ANTIGRAVITY_IDE_VERSION = "2.1.1";
+export const ANTIGRAVITY_IDE_BASE_URL = "https://daily-cloudcode-pa.googleapis.com";
+export const ANTIGRAVITY_IDE_USER_AGENT = `antigravity/ide/${ANTIGRAVITY_IDE_VERSION} darwin/arm64`;
+
 // Antigravity OAuth client credentials (public CLI client — duplicated in usage.js + src/lib/oauth)
 export const ANTIGRAVITY_OAUTH_CLIENT = {
   clientId: "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com",