feat: Gemini 4 Argon + per-account Antigravity lineup (CLI UA for Argon, 4.6/5.5 by account roster)

docs-site/src/content/docs/guides/providers.md

@@ -146,6 +146,25 @@ login-only too: `ocx login google-antigravity` signs in with your Google account
 Assist wire, and the `google` preset beside it is the AI Studio Gemini API — a different product
 reached with its own key, not a key mode for the same login.
 
+Gemini 4 Argon (`gemini-4-argon`) is listed on the `google` preset with low, medium (the
+default), and high thinking levels. Google offers it on the paid Gemini API tier only, not the free
+tier. On `google-antigravity`, Argon is listed with the same three levels, which map to the
+`gemini-4-argon-low`, `-medium`, and `-high` wire models. Google limits it there to AI Ultra and
+eligible Enterprise accounts. Cloud Code Assist serves Argon only to the Antigravity CLI client, so
+OpenCodex sends Argon requests and model discovery with the CLI User-Agent
+(`antigravity/cli/1.3.4`) and keeps the IDE User-Agent for every other model.
+
+The built-in `google-antigravity` model list is Gemini 3.8 Flash (`gemini-3.8-flash`), Gemini 4 Argon
+(`gemini-4-argon`), Claude Opus 5.5 (`claude-opus-5-5`), and Claude Sonnet 5.5
+(`claude-sonnet-5-5`), each with low, medium, and high efforts. What you actually see is your
+account's own model discovery, because Google enables models per account: some accounts list
+Claude Sonnet 4.6 and Claude Opus 4.6 (Thinking), others only Claude Opus and Sonnet 5.5 (directly
+billed, non-trial Pro or Ultra plans), and Gemini 4 Argon only on Ultra and Enterprise. Both Claude
+generations map: 4.6 takes its effort as a thinking level, 5.5 as its `-low`, `-medium`, or
+`-high` model. With several Antigravity accounts and `oauthAccountFailover.enabled`, a request
+prefers an account whose discovery lists the requested model. Saved selections of models that left
+the list keep routing as before.
+
 To check which mode a provider is actually using, open it on the Providers page: the **Connection**
 block's **Authentication** row reads `OAuth`, `API key`, `ChatGPT passthrough`, `Local`, or
 `No key needed`. It is a provider-level setting, so the account rows below it do not repeat it.

scripts/model-metadata.source.json

@@ -13059,6 +13059,25 @@
 				"maxLevel": "high"
 			}
 		},
+		"gemini-4-argon": {
+			"id": "gemini-4-argon",
+			"name": "Gemini 4 Argon",
+			"api": "google-generative-ai",
+			"provider": "google",
+			"baseUrl": "https://generativelanguage.googleapis.com/v1beta",
+			"reasoning": true,
+			"input": [
+				"text",
+				"image"
+			],
+			"contextWindow": 1048576,
+			"maxTokens": 65536,
+			"thinking": {
+				"mode": "google-level",
+				"minLevel": "low",
+				"maxLevel": "high"
+			}
+		},
 		"gemini-flash-latest": {
 			"id": "gemini-flash-latest",
 			"name": "Gemini Flash Latest",

scripts/test-layout/layout.json

@@ -957,6 +957,8 @@
     "gather-routed-models-single-flight.test.ts": "codex-integration",
     "gcp-adc.test.ts": "adapters/google",
     "gemini-37-flash-migration.test.ts": "adapters/google",
+    "gemini-4-argon-antigravity.test.ts": "adapters/google",
+    "antigravity-account-roster.test.ts": "adapters/google",
     "gemini-inline.test.ts": "images",
     "gemini-web-search.test.ts": "adapters/google",
     "generic-oauth-failover.test.ts": "oauth",

src/adapters/client-fingerprint.ts

@@ -55,6 +55,8 @@ const ANTIGRAVITY_IDE_PLATFORM = "windows/amd64";
  * Must be the IDE client family (`antigravity/ide/...`): Cloud Code Assist backend gates
  * newer agent models (e.g. `gemini-3.7-flash`) by User-Agent and answers 404 NOT_FOUND to
  * CLI-shaped UAs even with a valid OAuth token. Only `antigravity/ide/<ver>` unlocks them.
+ * The one exception is Gemini 4 Argon, which CCA serves ONLY to the CLI family; see
+ * `antigravityCliUserAgent`.
  * A `GOOGLE_ANTIGRAVITY_USER_AGENT` override (set by the caller) takes precedence upstream.
  */
 export function antigravityUserAgent(version = ANTIGRAVITY_IDE_VERSION, authMethod = "oauth"): string {
@@ -63,3 +65,25 @@ export function antigravityUserAgent(version = ANTIGRAVITY_IDE_VERSION, authMeth
   const [osType, arch] = ANTIGRAVITY_IDE_PLATFORM.split("/");
   return `antigravity/ide/${version} (os_type=${osType}; arch=${arch}; ${ANTIGRAVITY_IDE_CLIENT_NAME}; auth_method=${authMethod})`;
 }
+
+// ── Antigravity CLI ──
+/** Antigravity CLI version whose User-Agent CCA was verified to serve Gemini 4 Argon to. */
+export const ANTIGRAVITY_CLI_VERSION = "1.3.4";
+const ANTIGRAVITY_CLI_PLATFORM = "darwin/arm64";
+
+/**
+ * Antigravity CLI User-Agent:
+ * `antigravity/cli/${version} (os_type=${osType}; arch=${arch}; aidev_client; auth_method=oauth)`.
+ *
+ * Verified 2026-10-14 against live CCA: `gemini-4-argon-{low,medium,high}` answer only to this
+ * family and return 404 "Requested entity was not found" to the IDE UA above, while
+ * `gemini-3.7-flash-tiered` and `gemini-3.1-pro-low` 404 under this one. So it is used ONLY for
+ * Argon requests and for model discovery, never as a general replacement for the IDE UA.
+ *
+ * `GOOGLE_ANTIGRAVITY_USER_AGENT` deliberately does not apply here: that override names the IDE
+ * header, and letting it replace this one would re-lock Argon for anyone who set it.
+ */
+export function antigravityCliUserAgent(version = ANTIGRAVITY_CLI_VERSION, authMethod = "oauth"): string {
+  const [osType, arch] = ANTIGRAVITY_CLI_PLATFORM.split("/");
+  return `antigravity/cli/${version} (os_type=${osType}; arch=${arch}; ${ANTIGRAVITY_IDE_CLIENT_NAME}; auth_method=${authMethod})`;
+}

src/adapters/cursor/catalog.ts

@@ -244,6 +244,14 @@ export const CURSOR_CAPABILITIES: Record<string, CursorCapability> = {
     defaultVariant: "regular",
     variants: { regular: { levels: ["low", "medium", "high"] } },
   },
+  // 261014 preemptive, like gemini-3.8-flash: Cursor's models page lists Gemini 4 Argon, but the
+  // live GetUsableModels id is unverified. Inert until the live roster lists this id.
+  "gemini-4-argon": {
+    displayName: "Gemini 4 Argon",
+    window: CONTEXT_GEMINI,
+    defaultVariant: "regular",
+    variants: { regular: { levels: ["low", "medium", "high"] } },
+  },
   // Seeded from the live GetUsableModels roster attached to #4820, which advertises six
   // muse-spark-1.3 effort variants. The ladder stops at xhigh on purpose: see the matching
   // effort-map entry for why Cursor advertising `-max` is not evidence that it runs.

src/adapters/cursor/effort-map.ts

@@ -56,6 +56,9 @@ const CURSOR_MODEL_EFFORT_TIERS: Record<string, readonly string[]> = {
   // glm-5.3 was. Google documents low/medium/high with no `minimal` for this generation,
   // unlike 3.6. The seed is inert until Cursor's live roster lists the id.
   "gemini-3.8-flash": ["low", "medium", "high"],
+  // 261014 preemptive: Gemini 4 Argon, low/medium/high with no `minimal` (a documented 400).
+  // Inert until Cursor's live roster lists the id.
+  "gemini-4-argon": ["low", "medium", "high"],
   // Explicit-thinking variants (260825 live roster). Tiers are the rungs the wire actually
   // lists for each family, which is not always the same set the non-thinking id carries:
   // 4.6-opus thinks only at high/max, 4.5-opus only at high, 4.6-sonnet only at medium.

src/adapters/google-antigravity-wire.ts

@@ -1,6 +1,6 @@
 import { createHash } from "node:crypto";
 import type { OcxContentPart, OcxParsedRequest } from "../types";
-import { antigravityUserAgent } from "./client-fingerprint";
+import { antigravityCliUserAgent, antigravityUserAgent } from "./client-fingerprint";
 
 /**
  * Antigravity request User-Agent. Mirrors the real Antigravity IDE UA
@@ -11,6 +11,27 @@ import { antigravityUserAgent } from "./client-fingerprint";
  */
 export const ANTIGRAVITY_REQUEST_UA = antigravityUserAgent();
 
+/**
+ * Antigravity CLI User-Agent. CCA serves Gemini 4 Argon only to the CLI client family, and it
+ * 404s other agent models (`gemini-3.7-flash-tiered`, `gemini-3.1-pro-low`) under it, so the
+ * choice is per wire model: see `antigravityUserAgentForWireModel`.
+ */
+export const ANTIGRAVITY_CLI_REQUEST_UA = antigravityCliUserAgent();
+
+/**
+ * Model discovery (`:fetchAvailableModels`) uses the CLI UA so Argon's wire ids are listed;
+ * under the IDE UA they are absent.
+ */
+export const ANTIGRAVITY_DISCOVERY_UA = ANTIGRAVITY_CLI_REQUEST_UA;
+
+/** Wire ids CCA serves only to the CLI client family (verified 2026-10-14). */
+const ANTIGRAVITY_CLI_ONLY_WIRE_MODEL = /^gemini-4-argon(?:-(?:low|medium|high))?$/;
+
+/** The User-Agent an Antigravity inference request for `wireModelId` must carry. */
+export function antigravityUserAgentForWireModel(wireModelId: string): string {
+  return ANTIGRAVITY_CLI_ONLY_WIRE_MODEL.test(wireModelId) ? ANTIGRAVITY_CLI_REQUEST_UA : ANTIGRAVITY_REQUEST_UA;
+}
+
 /**
  * Whether a stored `OcxToolCall.thoughtSignature` is a REAL upstream Gemini signature versus a
  * foreign id that must not be forwarded to Gemini/Antigravity.

src/adapters/google.ts

@@ -21,7 +21,7 @@ import { getVertexAccessToken } from "../lib/gcp-adc";
 import { fetchAntigravityWithRetry, fetchVertexWithRetry } from "./google-http";
 import { safeAntigravityHttpErrorMessage, safeVertexHttpErrorMessage } from "./google-errors";
 import { isVertexTruncatedTurn, vertexTruncationErrorEvent } from "./google-truncation";
-import { ANTIGRAVITY_REQUEST_UA, antigravitySessionAnchor, antigravitySessionId, isLikelyRealThoughtSignature, sanitizeAntigravityClaudeSignatures } from "./google-antigravity-wire";
+import { antigravitySessionAnchor, antigravityUserAgentForWireModel, antigravitySessionId, isLikelyRealThoughtSignature, sanitizeAntigravityClaudeSignatures } from "./google-antigravity-wire";
 import { summarizeGoogleWireShape } from "./google-wire-shape";
 import { compileGoogleWireBody } from "./google-wire-compiler";
 import type { GoogleToolSchemaLossReport, GoogleToolSchemaProfile } from "./google-tool-schema";
@@ -1155,7 +1155,7 @@ export function createGoogleAdapter(provider: OcxProviderConfig): ProviderAdapte
           requestId: `agent-${crypto.randomUUID()}`,
           request,
         };
-        headers["User-Agent"] = ANTIGRAVITY_REQUEST_UA;
+        headers["User-Agent"] = antigravityUserAgentForWireModel(wireModelId);
         headers["Authorization"] = `Bearer ${token}`;
         return { url, method: "POST", headers, body: JSON.stringify(envelope) };
       }

src/codex/catalog/model-hints.ts

@@ -431,7 +431,9 @@ export function suppressedSyntheticMaxCatalogSlugs(
   }
   return slugs;
 }
-export const QUIET_AUTHORITATIVE_CATALOG_PROVIDERS = new Set(["kimi", "xai"]);
+// google-antigravity: the static lineup is an entitlement superset (Claude 5.5 and Gemini 4 Argon
+// are per-account), so a live roster that omits some of it is the expected case, not drift.
+export const QUIET_AUTHORITATIVE_CATALOG_PROVIDERS = new Set(["kimi", "xai", "google-antigravity"]);
 
 export const CALLABLE_CONFIGURED_COMPATIBILITY_MODELS: Readonly<Record<string, ReadonlySet<string>>> = {
   // CodeBuddy's vendor defaults are real callable selectors — both the bundled manifests

src/codex/catalog/provider-models.ts

@@ -53,6 +53,7 @@ import {
 import type { FastPolicyAuthority } from "../../providers/fastwire";
 import { effectiveGoogleMode, getProviderRegistryEntry, providerMatchesRegistryTransport, registryEntryForProviderDestination } from "../../providers/registry";
 import { parseAntigravityAvailableModels, registerAntigravityDiscoveredWireModels } from "../../providers/antigravity-models";
+import { recordAntigravityAccountRoster } from "../../providers/antigravity-account-roster";
 import { applyProviderContextCap, providerContextCap, resolveUnknownRoutedContextWindow } from "../../providers/context-cap";
 import { clampAutoCompactTokenLimit } from "../../providers/auto-compact-budget";
 import { effectiveModelAliases } from "../../providers/default-aliases";
@@ -807,6 +808,9 @@ export async function fetchProviderModelsWithAuth(
         provider: name,
         cacheGeneration,
       });
+      // Entitlement is per account (Claude 4.6 vs 5.5, Argon): remember what THIS account
+      // lists so account selection can prefer one that serves the requested model.
+      if (auth.oauthAccountId) recordAntigravityAccountRoster(name, auth.oauthAccountId, antigravity);
       if (!setCached(name, forCache, Date.now(), cacheGeneration)) {
         return observed(withConfiguredRetention(configured), "degraded");
       }