diff --git a/open-sse/config/agyModels.ts b/open-sse/config/agyModels.ts
index 8ba930782a..d836888b7f 100644
--- a/open-sse/config/agyModels.ts
+++ b/open-sse/config/agyModels.ts
@@ -1,10 +1,10 @@
 // Antigravity CLI (`agy`) model catalog.
 //
-// These IDs were pinned directly from the live `:fetchAvailableModels` endpoint
+// These models are pinned from the live `:fetchAvailableModels` endpoint
 // (https://daily-cloudcode-pa.googleapis.com/v1internal:fetchAvailableModels) using a
-// real `agy` consumer-OAuth token on 2026-05-29. They are the exact upstream model IDs
-// the Antigravity backend accepts — no alias remapping is required (unlike the
-// `antigravity` provider, whose catalog used display IDs that needed remapping).
+// real `agy` consumer-OAuth token. The public catalog exposes the same clean Gemini
+// 3.5 Flash tier names as the Antigravity IDE provider; the shared Antigravity executor
+// maps those names to the legacy upstream IDs immediately before dispatch.
 //
 // The `agy` provider reuses the `antigravity` executor/translator (identical backend),
 // but ships its OWN catalog so it can expose models the `antigravity` provider's static
@@ -62,24 +62,6 @@ export const AGY_PUBLIC_MODELS = Object.freeze([
     supportsVision: true,
     toolCalling: true,
   },
-  {
-    id: "gemini-3-flash-agent",
-    name: "Gemini 3.5 Flash (Agent)",
-    contextLength: 1048576,
-    maxOutputTokens: 65536,
-    supportsReasoning: true,
-    supportsVision: true,
-    toolCalling: true,
-  },
-  {
-    id: "gemini-3-flash",
-    name: "Gemini 3 Flash",
-    contextLength: 1048576,
-    maxOutputTokens: 65536,
-    supportsReasoning: true,
-    supportsVision: true,
-    toolCalling: true,
-  },
   {
     id: "gemini-3.5-flash-low",
     name: "Gemini 3.5 Flash (Low)",
@@ -89,10 +71,20 @@ export const AGY_PUBLIC_MODELS = Object.freeze([
     toolCalling: true,
   },
   {
-    id: "gemini-3.5-flash-extra-low",
-    name: "Gemini 3.5 Flash (Extra Low)",
+    id: "gemini-3.5-flash-medium",
+    name: "Gemini 3.5 Flash (Medium)",
     contextLength: 1048576,
     maxOutputTokens: 65536,
+    supportsReasoning: true,
+    supportsVision: true,
+    toolCalling: true,
+  },
+  {
+    id: "gemini-3.5-flash-high",
+    name: "Gemini 3.5 Flash (High)",
+    contextLength: 1048576,
+    maxOutputTokens: 65536,
+    supportsReasoning: true,
     supportsVision: true,
     toolCalling: true,
   },
diff --git a/open-sse/config/antigravityModelAliases.ts b/open-sse/config/antigravityModelAliases.ts
index 970fd44ac2..2685962069 100644
--- a/open-sse/config/antigravityModelAliases.ts
+++ b/open-sse/config/antigravityModelAliases.ts
@@ -22,10 +22,16 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
     supportsVision: true,
     toolCalling: true,
   },
-  // Gemini 3.5 Flash — flagship model in Antigravity 2.0 (May 2026)
+  // Gemini 3.5 Flash tiers exposed by Antigravity 2.0.4's model selector.
+  // The user-facing names are Low / Medium / High, but fetchAvailableModels reports
+  // legacy upstream IDs for two of them:
+  //   Low    -> gemini-3.5-flash-extra-low (displayName: Gemini 3.5 Flash (Low))
+  //   Medium -> gemini-3.5-flash-low       (displayName: Gemini 3.5 Flash (Medium))
+  //   High   -> gemini-3-flash-agent       (displayName: Gemini 3.5 Flash (High))
+  // Keep the clean public IDs here and map them below for routing/quota.
   {
-    id: "gemini-3.5-flash-preview",
-    name: "Gemini 3.5 Flash",
+    id: "gemini-3.5-flash-low",
+    name: "Gemini 3.5 Flash (Low)",
     contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
@@ -33,8 +39,17 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
     toolCalling: true,
   },
   {
-    id: "gemini-3-flash-agent",
-    name: "Gemini 3.5 Flash Agent",
+    id: "gemini-3.5-flash-medium",
+    name: "Gemini 3.5 Flash (Medium)",
+    contextLength: 1048576,
+    maxOutputTokens: 65536,
+    supportsReasoning: true,
+    supportsVision: true,
+    toolCalling: true,
+  },
+  {
+    id: "gemini-3.5-flash-high",
+    name: "Gemini 3.5 Flash (High)",
     contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
@@ -71,33 +86,6 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
     supportsVision: true,
     toolCalling: true,
   },
-  {
-    id: "gemini-3-flash-preview",
-    name: "Gemini 3 Flash",
-    contextLength: 1048576,
-    maxOutputTokens: 65536,
-    supportsReasoning: true,
-    supportsVision: true,
-    toolCalling: true,
-  },
-  // Gemini 3.5 Flash budget tiers — agy ships these as exact upstream ids; #3184 verified
-  // they work via the antigravity OAuth provider (no alias remapping required).
-  {
-    id: "gemini-3.5-flash-low",
-    name: "Gemini 3.5 Flash (Low)",
-    contextLength: 1048576,
-    maxOutputTokens: 65536,
-    supportsVision: true,
-    toolCalling: true,
-  },
-  {
-    id: "gemini-3.5-flash-extra-low",
-    name: "Gemini 3.5 Flash (Extra Low)",
-    contextLength: 1048576,
-    maxOutputTokens: 65536,
-    supportsVision: true,
-    toolCalling: true,
-  },
   {
     id: "gemini-3.1-flash-lite",
     name: "Gemini 3.1 Flash Lite",
@@ -160,17 +148,20 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
   },
 ]);
 
-// The Antigravity upstream API uses plain model IDs (no -high/-low suffix).
-// The -high/-low suffix convention was speculative and caused 404 for all
-// gemini-3.x models. Only plain IDs like "gemini-2.5-flash" are proven working.
 export const ANTIGRAVITY_MODEL_ALIASES = Object.freeze({
+  "gemini-3.5-flash-low": "gemini-3.5-flash-extra-low",
+  "gemini-3.5-flash-medium": "gemini-3.5-flash-low",
+  "gemini-3.5-flash-high": "gemini-3-flash-agent",
+  // Backward-compat: the retired flagship public id `gemini-3.5-flash-preview`
+  // (Antigravity 2.0's "Gemini 3.5 Flash") is kept as a HIDDEN alias so saved
+  // combos/configs keep routing — it maps to the reasoning-capable High tier
+  // (upstream `gemini-3-flash-agent`). It is NOT re-added to the public catalog.
+  "gemini-3.5-flash-preview": "gemini-3-flash-agent",
   "gemini-3-pro-preview": "gemini-3.1-pro",
   // agy catalog exposes -high/-low budget tiers, but the upstream rejects the suffix
   // for gemini-3.x (#3229) — map them to the plain proven id.
   "gemini-3.1-pro-high": "gemini-3.1-pro",
   "gemini-3.1-pro-low": "gemini-3.1-pro",
-  "gemini-3.5-flash-preview": "gemini-3.5-flash",
-  "gemini-3-flash-preview": "gemini-3-flash",
   "gemini-3-pro-image-preview": "gemini-3-pro-image",
   "gemini-2.5-computer-use-preview-10-2025": "rev19-uic3-1p",
   // Legacy Claude display ids → current upstream ids. NOTE: an earlier comment here
@@ -186,10 +177,9 @@ export const ANTIGRAVITY_MODEL_ALIASES = Object.freeze({
 type AntigravityModelAliasMap = Record<string, string>;
 
 export const ANTIGRAVITY_REVERSE_MODEL_ALIASES: AntigravityModelAliasMap = Object.freeze({
+  "gemini-3.5-flash-extra-low": "gemini-3.5-flash-low",
+  "gemini-3-flash-agent": "gemini-3.5-flash-high",
   "gemini-3.1-pro": "gemini-3-pro-preview",
-  "gemini-3.5-flash": "gemini-3.5-flash-preview",
-  "gemini-3-flash-agent": "gemini-3.5-flash-preview",
-  "gemini-3-flash": "gemini-3-flash-preview",
   "gemini-3-pro-image": "gemini-3-pro-image-preview",
   "rev19-uic3-1p": "gemini-2.5-computer-use-preview-10-2025",
 });
diff --git a/open-sse/executors/antigravity.ts b/open-sse/executors/antigravity.ts
index d9267e0a7e..13969a4313 100644
--- a/open-sse/executors/antigravity.ts
+++ b/open-sse/executors/antigravity.ts
@@ -194,7 +194,7 @@ function addAntigravityTextualToolCall(
 
 type AntigravityRequestEnvelope = Record<string, unknown> & {
   project: string;
-  model: string;
+  model?: string;
   userAgent: "antigravity" | "jetski";
   requestType: "agent" | "image_gen";
   requestId: string;
@@ -336,6 +336,15 @@ function processAntigravitySSEPayload(
   if (!payload || payload === "[DONE]") return;
   try {
     const parsed = JSON.parse(payload);
+    const markdown =
+      typeof parsed?.markdown === "string"
+        ? parsed.markdown
+        : typeof parsed?.response?.markdown === "string"
+          ? parsed.response.markdown
+          : null;
+    if (markdown) {
+      collected.textContent += markdown;
+    }
     const candidate = parsed?.response?.candidates?.[0];
     if (candidate?.content?.parts) {
       for (const part of candidate.content.parts) {
@@ -661,9 +670,14 @@ export class AntigravityExecutor extends BaseExecutor {
             if (typeof p.text === "string" && p.text === "") return false;
             if (p.functionCall && !p.functionCall.name) return false;
 
-            // Only strip if it's NOT our bypass sentinel. 
+            // Only strip if it's NOT our bypass sentinel.
             // Antigravity models (like Gemini) need this sentinel to bypass 400 errors.
-            return !p.thought && (hasFunctionCall || !p.thoughtSignature || p.thoughtSignature === "skip_thought_signature_validator");
+            return (
+              !p.thought &&
+              (hasFunctionCall ||
+                !p.thoughtSignature ||
+                p.thoughtSignature === "skip_thought_signature_validator")
+            );
           }) || [];
         return { ...c, role, parts };
       }) || [];
diff --git a/open-sse/services/model.ts b/open-sse/services/model.ts
index e870f708f3..ec0f0844ff 100644
--- a/open-sse/services/model.ts
+++ b/open-sse/services/model.ts
@@ -1,5 +1,4 @@
 import { PROVIDER_ID_TO_ALIAS, PROVIDER_MODELS } from "../config/providerModels.ts";
-import { ANTIGRAVITY_MODEL_ALIASES } from "../config/antigravityModelAliases.ts";
 import { resolveWildcardAlias } from "./wildcardRouter.ts";
 
 type ProviderModelAliasMap = Record<string, Record<string, string>>;
@@ -76,7 +75,12 @@ const PROVIDER_MODEL_ALIASES: ProviderModelAliasMap = {
     "gpt-oss-20b": "openai/gpt-oss-20b",
     "nvidia/gpt-oss-20b": "openai/gpt-oss-20b",
   },
-  antigravity: { ...ANTIGRAVITY_MODEL_ALIASES },
+  // Antigravity model aliases must be applied by the Antigravity executor, not by
+  // the global model resolver. Applying them here rewrites the client-visible model
+  // before credential/account routing and before UI/logging, causing clean IDs like
+  // gemini-3.5-flash-high to be exposed and retried as upstream-only legacy ids such
+  // as gemini-3-flash-agent. The executor owns provider-wire normalization.
+  antigravity: {},
   kiro: {
     "claude-opus-4-7": "claude-opus-4.7",
     "claude-opus-4-6": "claude-opus-4.6",
diff --git a/tests/unit/account-fallback-service.test.ts b/tests/unit/account-fallback-service.test.ts
index f47d9d0a02..3b52caa560 100644
--- a/tests/unit/account-fallback-service.test.ts
+++ b/tests/unit/account-fallback-service.test.ts
@@ -108,7 +108,7 @@ test("checkFallbackError locks Antigravity quota-reached 429 for the full reset
     429,
     message,
     0,
-    "gemini-3-flash-agent",
+    "gemini-3.5-flash-high",
     "antigravity",
     null,
     makeProfile()
@@ -124,7 +124,7 @@ test("checkFallbackError locks Antigravity quota-reached 429 for the full reset
 test("recordModelLockoutFailure honors a multi-day exactCooldownMs (under 30-day cap)", () => {
   const provider = "antigravity";
   const connectionId = "conn-quota-window";
-  const model = "gemini-3-flash-agent";
+  const model = "gemini-3.5-flash-high";
   const exactCooldownMs = (164 * 3600 + 27 * 60 + 24) * 1000;
 
   clearModelLock(provider, connectionId, model);
diff --git a/tests/unit/agy-provider.test.ts b/tests/unit/agy-provider.test.ts
index b7c922e4f5..13ed8097c1 100644
--- a/tests/unit/agy-provider.test.ts
+++ b/tests/unit/agy-provider.test.ts
@@ -4,7 +4,10 @@ import assert from "node:assert/strict";
 import { AI_PROVIDERS, USAGE_SUPPORTED_PROVIDERS } from "../../src/shared/constants/providers.ts";
 import { REGISTRY } from "../../open-sse/config/providerRegistry.ts";
 import { PROVIDERS as LEGACY_PROVIDERS } from "../../open-sse/config/constants.ts";
-import { PROVIDERS as OAUTH_PROVIDER_IDS, AGY_CONFIG } from "../../src/lib/oauth/constants/oauth.ts";
+import {
+  PROVIDERS as OAUTH_PROVIDER_IDS,
+  AGY_CONFIG,
+} from "../../src/lib/oauth/constants/oauth.ts";
 import { supportsTokenRefresh, REFRESH_LEAD_MS } from "../../open-sse/services/tokenRefresh.ts";
 import {
   AGY_PUBLIC_MODELS,
@@ -47,6 +50,12 @@ test("agy ships its own catalog including the Claude models antigravity omits",
   const ids = REGISTRY.agy.models.map((m) => m.id);
   assert.ok(ids.includes("claude-opus-4-6-thinking"), "must expose Claude Opus 4.6 Thinking");
   assert.ok(ids.includes("claude-sonnet-4-6"), "must expose Claude Sonnet 4.6");
+  assert.ok(ids.includes("gemini-3.5-flash-low"), "must expose clean Flash Low tier");
+  assert.ok(ids.includes("gemini-3.5-flash-medium"), "must expose clean Flash Medium tier");
+  assert.ok(ids.includes("gemini-3.5-flash-high"), "must expose clean Flash High tier");
+  assert.ok(!ids.includes("gemini-3-flash-agent"));
+  assert.ok(!ids.includes("gemini-3-flash"));
+  assert.ok(!ids.includes("gemini-3.5-flash-extra-low"));
   // Tab-completion models are not chat-callable and must be excluded.
   assert.ok(!ids.includes("tab_flash_lite_preview"));
   assert.ok(!ids.includes("tab_jump_flash_lite_preview"));
diff --git a/tests/unit/antigravity-model-aliases.test.ts b/tests/unit/antigravity-model-aliases.test.ts
index 511ac5dc9c..06b238a703 100644
--- a/tests/unit/antigravity-model-aliases.test.ts
+++ b/tests/unit/antigravity-model-aliases.test.ts
@@ -17,13 +17,16 @@ function getPublicModel(id: string) {
 
 test("resolveAntigravityModelId maps the documented Antigravity aliases to upstream IDs", () => {
   assert.equal(resolveAntigravityModelId("gemini-3-pro-preview"), "gemini-3.1-pro");
-  assert.equal(resolveAntigravityModelId("gemini-3.5-flash-preview"), "gemini-3.5-flash");
-  assert.equal(resolveAntigravityModelId("gemini-3-flash-preview"), "gemini-3-flash");
   assert.equal(resolveAntigravityModelId("gemini-3-pro-image-preview"), "gemini-3-pro-image");
   assert.equal(
     resolveAntigravityModelId("gemini-2.5-computer-use-preview-10-2025"),
     "rev19-uic3-1p"
   );
+  assert.equal(resolveAntigravityModelId("gemini-3.5-flash-low"), "gemini-3.5-flash-extra-low");
+  assert.equal(resolveAntigravityModelId("gemini-3.5-flash-medium"), "gemini-3.5-flash-low");
+  assert.equal(resolveAntigravityModelId("gemini-3.5-flash-high"), "gemini-3-flash-agent");
+  // Backward-compat: retired flagship public id routes to the High tier upstream.
+  assert.equal(resolveAntigravityModelId("gemini-3.5-flash-preview"), "gemini-3-flash-agent");
   assert.equal(resolveAntigravityModelId("gemini-claude-sonnet-4-5"), "claude-sonnet-4-6");
   assert.equal(resolveAntigravityModelId("gemini-claude-sonnet-4-5-thinking"), "claude-sonnet-4-6");
   assert.equal(
@@ -35,8 +38,8 @@ test("resolveAntigravityModelId maps the documented Antigravity aliases to upstr
 
 test("toClientAntigravityModelId exposes client-visible aliases for known upstream IDs", () => {
   assert.equal(toClientAntigravityModelId("gemini-3.1-pro"), "gemini-3-pro-preview");
-  assert.equal(toClientAntigravityModelId("gemini-3-flash-agent"), "gemini-3.5-flash-preview");
-  assert.equal(toClientAntigravityModelId("gemini-3-flash"), "gemini-3-flash-preview");
+  assert.equal(toClientAntigravityModelId("gemini-3.5-flash-extra-low"), "gemini-3.5-flash-low");
+  assert.equal(toClientAntigravityModelId("gemini-3-flash-agent"), "gemini-3.5-flash-high");
   assert.equal(toClientAntigravityModelId("gpt-oss-120b-medium"), "gpt-oss-120b-medium");
   assert.equal(toClientAntigravityModelId("claude-sonnet-4-6"), "claude-sonnet-4-6");
   assert.equal(toClientAntigravityModelId("claude-opus-4-6-thinking"), "claude-opus-4-6-thinking");
@@ -45,6 +48,8 @@ test("toClientAntigravityModelId exposes client-visible aliases for known upstre
 test("isUserCallableAntigravityModelId only allows public chat-capable model IDs", () => {
   assert.equal(isUserCallableAntigravityModelId("gemini-3-pro-preview"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3.1-pro"), true);
+  // Retired flagship id stays callable as a hidden backward-compat alias (routes to High),
+  // even though it is no longer exposed in the public catalog.
   assert.equal(isUserCallableAntigravityModelId("gemini-3.5-flash-preview"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3-flash-agent"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3.1-flash-lite"), true);
@@ -58,10 +63,12 @@ test("isUserCallableAntigravityModelId only allows public chat-capable model IDs
   // 2.0 was wrong.
   assert.equal(isUserCallableAntigravityModelId("claude-opus-4-6-thinking"), true);
   assert.equal(isUserCallableAntigravityModelId("claude-sonnet-4-6"), true);
-  // #3184: Gemini budget tiers now exposed (agy parity).
+  // Antigravity 2.0.4 exposes Gemini 3.5 Flash as separate UI tiers.
   assert.equal(isUserCallableAntigravityModelId("gemini-3.1-pro-high"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3.1-pro-low"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3.5-flash-low"), true);
+  assert.equal(isUserCallableAntigravityModelId("gemini-3.5-flash-medium"), true);
+  assert.equal(isUserCallableAntigravityModelId("gemini-3.5-flash-high"), true);
   assert.equal(isUserCallableAntigravityModelId("gemini-3.5-flash-extra-low"), true);
   assert.equal(isUserCallableAntigravityModelId("tab_flash_lite_preview"), false);
   assert.equal(isUserCallableAntigravityModelId("unknown-model"), false);
@@ -79,9 +86,9 @@ test("ANTIGRAVITY_PUBLIC_MODELS exposes captured Antigravity 2.0.1 names and cap
     toolCalling: true,
   });
   assert.equal(getPublicModel("claude-sonnet-4-6").name, "Claude Sonnet 4.6 (Thinking)");
-  assert.deepEqual(getPublicModel("gemini-3.5-flash-preview"), {
-    id: "gemini-3.5-flash-preview",
-    name: "Gemini 3.5 Flash",
+  assert.deepEqual(getPublicModel("gemini-3.5-flash-high"), {
+    id: "gemini-3.5-flash-high",
+    name: "Gemini 3.5 Flash (High)",
     contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
@@ -89,8 +96,8 @@ test("ANTIGRAVITY_PUBLIC_MODELS exposes captured Antigravity 2.0.1 names and cap
     toolCalling: true,
   });
   assert.equal(
-    getClientVisibleAntigravityModelName("gemini-3.5-flash-preview"),
-    "Gemini 3.5 Flash"
+    getClientVisibleAntigravityModelName("gemini-3.5-flash-medium"),
+    "Gemini 3.5 Flash (Medium)"
   );
   assert.equal(getClientVisibleAntigravityModelName("gemini-2.5-flash"), "Gemini 2.5 Flash");
   assert.equal(
@@ -127,15 +134,6 @@ test("ANTIGRAVITY_PUBLIC_MODELS has no duplicate model IDs", () => {
   assert.deepEqual(duplicates, [], `duplicate model IDs found: ${duplicates.join(", ")}`);
 });
 
-test("gemini-3-flash-agent keeps its Agent display name (not the Flash High duplicate)", () => {
-  // A duplicate entry previously overwrote this name with "Gemini 3.5 Flash (High)"
-  // because the id-keyed name map kept the last occurrence.
-  assert.equal(
-    getClientVisibleAntigravityModelName("gemini-3-flash-agent"),
-    "Gemini 3.5 Flash Agent"
-  );
-});
-
 test("AntigravityExecutor.transformRequest resolves alias models before dispatching upstream", async () => {
   const executor = new AntigravityExecutor();
   const result = await executor.transformRequest(
@@ -153,10 +151,10 @@ test("AntigravityExecutor.transformRequest resolves alias models before dispatch
   assert.equal(result.model, "gemini-3.1-pro");
 });
 
-test("AntigravityExecutor.transformRequest resolves Gemini 3.5 Flash alias upstream", async () => {
+test("AntigravityExecutor.transformRequest maps Gemini 3.5 Flash tiers to live upstream IDs", async () => {
   const executor = new AntigravityExecutor();
   const result = await executor.transformRequest(
-    "antigravity/gemini-3.5-flash-preview",
+    "antigravity/gemini-3.5-flash-high",
     {
       request: {
         contents: [{ role: "user", parts: [{ text: "Hello" }] }],
@@ -167,7 +165,11 @@ test("AntigravityExecutor.transformRequest resolves Gemini 3.5 Flash alias upstr
   );
 
   if (result instanceof Response) throw new Error("Unexpected Response from transformRequest");
-  assert.equal(result.model, "gemini-3.5-flash");
+  assert.equal(result.model, "gemini-3-flash-agent");
+  assert.equal(result.modelConfigId, undefined);
+  assert.equal(result.model_config_id, undefined);
+  assert.equal(result.request.modelConfigId, undefined);
+  assert.equal(result.request.model_config_id, undefined);
 });
 
 test("AntigravityExecutor.transformRequest sends Claude through Gemini-compatible Cloud Code schema", async () => {
diff --git a/tests/unit/executor-agy.test.ts b/tests/unit/executor-agy.test.ts
index 07975cb18d..96f35ba844 100644
--- a/tests/unit/executor-agy.test.ts
+++ b/tests/unit/executor-agy.test.ts
@@ -10,12 +10,15 @@ test("getExecutor('agy') returns AntigravityExecutor (not DefaultExecutor)", ()
 
 test("getExecutor('antigravity') returns AntigravityExecutor", () => {
   const executor = getExecutor("antigravity");
-  assert.ok(executor instanceof AntigravityExecutor, "antigravity provider should use AntigravityExecutor");
+  assert.ok(
+    executor instanceof AntigravityExecutor,
+    "antigravity provider should use AntigravityExecutor"
+  );
 });
 
 test("getExecutor('agy') builds valid streaming URL", () => {
   const executor = getExecutor("agy");
-  const url = executor.buildUrl("gemini-3-flash", true);
+  const url = executor.buildUrl("gemini-3.5-flash-high", true);
   assert.ok(
     url.includes("streamGenerateContent?alt=sse"),
     `expected streaming endpoint URL, got: ${url}`
@@ -24,7 +27,7 @@ test("getExecutor('agy') builds valid streaming URL", () => {
 
 test("getExecutor('agy') builds valid non-streaming URL", () => {
   const executor = getExecutor("agy");
-  const url = executor.buildUrl("gemini-3-flash", false);
+  const url = executor.buildUrl("gemini-3.5-flash-high", false);
   // Antigravity executor always uses streaming endpoint (buildUrl ignores stream flag)
   assert.ok(
     url.includes("streamGenerateContent?alt=sse"),
diff --git a/tests/unit/managed-model-import.test.ts b/tests/unit/managed-model-import.test.ts
index a0e9ea5c22..5df2d935a3 100644
--- a/tests/unit/managed-model-import.test.ts
+++ b/tests/unit/managed-model-import.test.ts
@@ -91,7 +91,7 @@ test("pruning stale connection available models during import", async () => {
   db.prepare(
     "INSERT INTO provider_connections (id, provider, auth_type, name, is_active, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?, ?)"
   ).run("conn-active", "openrouter", "apikey", "Active Connection", 1, "2026-05-29", "2026-05-29");
-  
+
   db.prepare(
     "INSERT INTO provider_connections (id, provider, auth_type, name, is_active, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?, ?)"
   ).run("conn-stale", "openrouter", "apikey", "Stale Connection", 0, "2026-05-29", "2026-05-29");
@@ -114,7 +114,7 @@ test("pruning stale connection available models during import", async () => {
 
   // Check models for "openrouter"
   const allSyncedModels = await modelsDb.getSyncedAvailableModels("openrouter");
-  
+
   // Stale connection should be pruned. Active connection and the new syncing connection should be kept.
   const ids = allSyncedModels.map((m) => m.id);
   assert.ok(ids.includes("shared/model-active"));
@@ -149,11 +149,7 @@ test("antigravity sync dynamically builds and saves mitmAlias mappings", async (
   assert.equal(mitmMappings["gemini-3.5-flash"], "antigravity/gemini-3.5-flash");
   assert.equal(mitmMappings["custom-antigravity-model"], "antigravity/custom-antigravity-model");
 
-  // Should contain reverse alias mappings (gemini-3.5-flash-preview maps to gemini-3.5-flash)
-  assert.equal(mitmMappings["gemini-3.5-flash-preview"], "antigravity/gemini-3.5-flash");
-  assert.equal(mitmMappings["gemini-3-flash-agent"], "antigravity/gemini-3.5-flash");
-
-  // Should contain forward alias mappings (gemini-3.5-flash-preview maps to gemini-3.5-flash)
-  assert.equal(mitmMappings["gemini-3.5-flash-preview"], "antigravity/gemini-3.5-flash");
+  // Removed Antigravity 2.0 preview/agent aliases must not be reintroduced.
+  assert.equal(mitmMappings["gemini-3.5-flash-preview"], undefined);
+  assert.equal(mitmMappings["gemini-3-flash-agent"], undefined);
 });
-
diff --git a/tests/unit/models-catalog-route.test.ts b/tests/unit/models-catalog-route.test.ts
index 14d88393ca..34ee03ce00 100644
--- a/tests/unit/models-catalog-route.test.ts
+++ b/tests/unit/models-catalog-route.test.ts
@@ -690,11 +690,13 @@ test("v1 models catalog exposes Antigravity client-visible preview aliases inste
 
   assert.equal(response.status, 200);
   assert.ok(ids.has("antigravity/gemini-3-pro-preview"));
-  assert.ok(ids.has("antigravity/gemini-3-flash-preview"));
-  // #3184/#3303: the Gemini budget tiers (`-high`/`-low`) are user-callable
-  // client-visible aliases on the Antigravity OAuth backend (agy parity), so
-  // they ARE now exposed in the catalog. (They alias to the plain
-  // `gemini-3.1-pro` upstream id — see ANTIGRAVITY_MODEL_ALIASES.)
+  assert.ok(ids.has("antigravity/gemini-3.5-flash-low"));
+  assert.ok(ids.has("antigravity/gemini-3.5-flash-medium"));
+  assert.ok(ids.has("antigravity/gemini-3.5-flash-high"));
+  assert.equal(ids.has("antigravity/gemini-3-flash-preview"), false);
+  assert.equal(ids.has("antigravity/gemini-3-flash-agent"), false);
+  // Gemini 3.1 Pro budget tiers remain client-visible aliases for the plain
+  // `gemini-3.1-pro` upstream id — see ANTIGRAVITY_MODEL_ALIASES.
   assert.ok(ids.has("antigravity/gemini-3.1-pro-high"));
   // The legacy `gemini-claude-*` ids are alias KEYS (remapped to live upstream
   // ids), not public catalog entries, so they stay unexposed.
diff --git a/tests/unit/t28-model-catalog-updates.test.ts b/tests/unit/t28-model-catalog-updates.test.ts
index de6d68655a..2dfa9d4089 100644
--- a/tests/unit/t28-model-catalog-updates.test.ts
+++ b/tests/unit/t28-model-catalog-updates.test.ts
@@ -24,18 +24,19 @@ test("T28: gemini AI Studio catalog includes current preview models", () => {
   assert.ok(geminiCliIds.includes("gemini-3-flash-preview"));
 });
 
-test("T28: antigravity static catalog exposes client-visible Gemini preview IDs", () => {
+test("T28: antigravity static catalog exposes client-visible Gemini tier IDs", () => {
   const staticIds = (getStaticModelsForProvider("antigravity") || []).map((m) => m.id);
 
   assert.ok(staticIds.includes("gemini-3-pro-preview"));
-  assert.ok(staticIds.includes("gemini-3-flash-preview"));
-  // #3303 (agy parity, discussion #3184): the Gemini budget tiers ARE
-  // client-visible on the Antigravity OAuth backend — restoring tiers an
-  // earlier assumption had wrongly hidden.
+  assert.ok(staticIds.includes("gemini-3.5-flash-low"));
+  assert.ok(staticIds.includes("gemini-3.5-flash-medium"));
+  assert.ok(staticIds.includes("gemini-3.5-flash-high"));
   assert.ok(staticIds.includes("gemini-3.1-pro-low"));
   assert.ok(staticIds.includes("gemini-3.1-pro-high"));
   // Legacy aliases that were never client-visible stay absent.
   assert.ok(!staticIds.includes("gemini-3-pro-high"));
+  assert.ok(!staticIds.includes("gemini-3-flash-preview"));
+  assert.ok(!staticIds.includes("gemini-3-flash-agent"));
   assert.ok(!staticIds.includes("gemini-claude-sonnet-4-5"));
   assert.ok(!staticIds.includes("gemini-claude-sonnet-4-5-thinking"));
   assert.ok(!staticIds.includes("gemini-claude-opus-4-5-thinking"));