diff --git a/quickstart.ps1 b/quickstart.ps1
index b8bbd9a254..ded9543f15 100644
--- a/quickstart.ps1
+++ b/quickstart.ps1
@@ -1022,6 +1022,10 @@ $hiveKey = [System.Environment]::GetEnvironmentVariable("HIVE_API_KEY", "User")
 if (-not $hiveKey) { $hiveKey = $env:HIVE_API_KEY }
 if ($hiveKey) { $HiveCredDetected = $true }
 
+$AntigravityCredDetected = $false
+$antigravityAuthPath = Join-Path $env:USERPROFILE ".hive\antigravity-accounts.json"
+if (Test-Path $antigravityAuthPath) { $AntigravityCredDetected = $true }
+
 # Detect API key providers
 $ProviderMenuEnvVars  = @("ANTHROPIC_API_KEY", "OPENAI_API_KEY", "GEMINI_API_KEY", "GROQ_API_KEY", "CEREBRAS_API_KEY", "OPENROUTER_API_KEY")
 $ProviderMenuNames    = @("Anthropic (Claude) - Recommended", "OpenAI (GPT)", "Google Gemini - Free tier available", "Groq - Fast, free tier", "Cerebras - Fast, free tier", "OpenRouter - Bring any OpenRouter model")
@@ -1057,6 +1061,7 @@ if (Test-Path $HiveConfigFile) {
             if ($prevLlm.use_claude_code_subscription) { $PrevSubMode = "claude_code" }
             elseif ($prevLlm.use_codex_subscription) { $PrevSubMode = "codex" }
             elseif ($prevLlm.use_kimi_code_subscription) { $PrevSubMode = "kimi_code" }
+            elseif ($prevLlm.use_antigravity_subscription) { $PrevSubMode = "antigravity" }
             elseif ($prevLlm.api_base -and $prevLlm.api_base -like "*api.z.ai*") { $PrevSubMode = "zai_code" }
             elseif ($prevLlm.provider -eq "minimax" -or ($prevLlm.api_base -and $prevLlm.api_base -like "*api.minimax.io*")) { $PrevSubMode = "minimax_code" }
             elseif ($prevLlm.api_base -and $prevLlm.api_base -like "*api.kimi.com*") { $PrevSubMode = "kimi_code" }
@@ -1076,6 +1081,7 @@ if ($PrevSubMode -or $PrevProvider) {
         "minimax_code" { if ($MinimaxCredDetected) { $prevCredValid = $true } }
         "kimi_code"   { if ($KimiCredDetected)   { $prevCredValid = $true } }
         "hive_llm"    { if ($HiveCredDetected)   { $prevCredValid = $true } }
+        "antigravity" { if ($AntigravityCredDetected) { $prevCredValid = $true } }
         default {
             if ($PrevProvider -eq "ollama") {
                 $prevCredValid = $true
@@ -1094,18 +1100,20 @@ if ($PrevSubMode -or $PrevProvider) {
             "minimax_code" { $DefaultChoice = "4" }
             "kimi_code"   { $DefaultChoice = "5" }
             "hive_llm"    { $DefaultChoice = "6" }
+            "antigravity" { $DefaultChoice = "7" }
         }
         if (-not $DefaultChoice) {
             switch ($PrevProvider) {
-                "anthropic" { $DefaultChoice = "7" }
-                "openai"    { $DefaultChoice = "8" }
-                "gemini"    { $DefaultChoice = "9" }
-                "groq"      { $DefaultChoice = "10" }
-                "cerebras"  { $DefaultChoice = "11" }
-                "openrouter" { $DefaultChoice = "12" }
-                "ollama"     { $DefaultChoice = "13" }
+                "anthropic" { $DefaultChoice = "8" }
+                "openai"    { $DefaultChoice = "9" }
+                "gemini"    { $DefaultChoice = "10" }
+                "groq"      { $DefaultChoice = "11" }
+                "cerebras"  { $DefaultChoice = "12" }
+                "openrouter" { $DefaultChoice = "13" }
+                "ollama"     { $DefaultChoice = "14" }
                 "minimax"   { $DefaultChoice = "4" }
                 "kimi"      { $DefaultChoice = "5" }
+                "hive"      { $DefaultChoice = "6" }
             }
         }
     }
@@ -1158,12 +1166,19 @@ Write-Host ") Hive LLM                   " -NoNewline
 Write-Color -Text "(use your Hive API key)" -Color DarkGray -NoNewline
 if ($HiveCredDetected) { Write-Color -Text "  (credential detected)" -Color Green } else { Write-Host "" }
 
+# 7) Antigravity
+Write-Host "  " -NoNewline
+Write-Color -Text "7" -Color Cyan -NoNewline
+Write-Host ") Antigravity Subscription  " -NoNewline
+Write-Color -Text "(use your Google/Gemini plan)" -Color DarkGray -NoNewline
+if ($AntigravityCredDetected) { Write-Color -Text "  (credential detected)" -Color Green } else { Write-Host "" }
+
 Write-Host ""
 Write-Color -Text "  API key providers:" -Color Cyan
 
-# 7-12) API key providers
+# 8-13) API key providers
 for ($idx = 0; $idx -lt $ProviderMenuEnvVars.Count; $idx++) {
-    $num = $idx + 7
+    $num = $idx + 8
     $envVal = [System.Environment]::GetEnvironmentVariable($ProviderMenuEnvVars[$idx], "Process")
     if (-not $envVal) { $envVal = [System.Environment]::GetEnvironmentVariable($ProviderMenuEnvVars[$idx], "User") }
     Write-Host "  " -NoNewline
@@ -1172,9 +1187,9 @@ for ($idx = 0; $idx -lt $ProviderMenuEnvVars.Count; $idx++) {
     if ($envVal) { Write-Color -Text "  (credential detected)" -Color Green } else { Write-Host "" }
 }
 
-# 13) Local (Ollama) — no API key needed
+# 14) Local (Ollama) - no API key needed
 Write-Host "  " -NoNewline
-Write-Color -Text "13" -Color Cyan -NoNewline
+Write-Color -Text "14" -Color Cyan -NoNewline
 if ($OllamaDetected) {
     Write-Host ") Local (Ollama) - No API key needed  " -NoNewline
     Write-Color -Text "(ollama detected)" -Color Green
@@ -1182,7 +1197,7 @@ if ($OllamaDetected) {
     Write-Host ") Local (Ollama) - No API key needed"
 }
 
-$SkipChoice = 7 + $ProviderMenuEnvVars.Count + 1
+$SkipChoice = 8 + $ProviderMenuEnvVars.Count + 1
 Write-Host "  " -NoNewline
 Write-Color -Text "$SkipChoice" -Color Cyan -NoNewline
 Write-Host ") Skip for now"
@@ -1320,9 +1335,48 @@ switch ($num) {
         }
         Write-Color -Text "  Model: $SelectedModel | API: $HiveLlmEndpoint" -Color DarkGray
     }
-    { $_ -ge 7 -and $_ -le 12 } {
+    7 {
+        # Antigravity Subscription
+        if (-not $AntigravityCredDetected) {
+            Write-Host ""
+            Write-Color -Text "  Setting up Antigravity authentication..." -Color Cyan
+            Write-Host ""
+            Write-Warn "A browser window will open for Google OAuth."
+            Write-Host "  Sign in with your Google account that has Antigravity access."
+            Write-Host ""
+            try {
+                $null = & $UvCmd run python (Join-Path $ScriptDir "core\antigravity_auth.py") auth account add 2>&1
+                if ($LASTEXITCODE -eq 0 -and (Test-Path $antigravityAuthPath)) {
+                    $AntigravityCredDetected = $true
+                }
+            } catch {
+                $AntigravityCredDetected = $false
+            }
+
+            if (-not $AntigravityCredDetected) {
+                Write-Host ""
+                Write-Fail "Authentication failed or was cancelled."
+                Write-Host ""
+                $SelectedProviderId = ""
+            }
+        }
+
+        if ($AntigravityCredDetected) {
+            $SubscriptionMode        = "antigravity"
+            $SelectedProviderId      = "openai"
+            $SelectedModel           = "gemini-3-flash"
+            $SelectedMaxTokens       = 32768
+            $SelectedMaxContextTokens = 1000000
+            Write-Host ""
+            Write-Warn "Using Antigravity can technically cause your account suspension. Please use at your own risk."
+            Write-Host ""
+            Write-Ok "Using Antigravity subscription"
+            Write-Color -Text "  Model: gemini-3-flash | Direct OAuth (no proxy required)" -Color DarkGray
+        }
+    }
+    { $_ -ge 8 -and $_ -le 13 } {
         # API key providers
-        $provIdx = $num - 7
+        $provIdx = $num - 8
         $SelectedEnvVar     = $ProviderMenuEnvVars[$provIdx]
         $SelectedProviderId = $ProviderMenuIds[$provIdx]
         $providerName       = $ProviderMenuNames[$provIdx] -replace ' - .*', ''  # strip description
@@ -1402,7 +1456,7 @@ switch ($num) {
             }
         }
     }
-    13 {
+    14 {
         # Local (Ollama)
         if (-not $OllamaDetected) {
             Write-Host ""
@@ -1774,6 +1828,8 @@ if ($SelectedProviderId) {
         $config.llm["use_claude_code_subscription"] = $true
     } elseif ($SubscriptionMode -eq "codex") {
         $config.llm["use_codex_subscription"] = $true
+    } elseif ($SubscriptionMode -eq "antigravity") {
+        $config.llm["use_antigravity_subscription"] = $true
     } elseif ($SubscriptionMode -eq "zai_code") {
         $config.llm["api_base"] = "https://api.z.ai/api/coding/paas/v4"
         $config.llm["api_key_env_var"] = $SelectedEnvVar
@@ -2096,6 +2152,9 @@ if ($SelectedProviderId) {
         Write-Color -Text "  API: api.minimax.io/v1 (OpenAI-compatible)" -Color DarkGray
     } elseif ($SubscriptionMode -eq "codex") {
         Write-Ok "OpenAI Codex Subscription -> $SelectedModel"
+    } elseif ($SubscriptionMode -eq "antigravity") {
+        Write-Ok "Antigravity Subscription -> $SelectedModel"
+        Write-Color -Text "  Direct OAuth (no proxy required)" -Color DarkGray
     } elseif ($SelectedProviderId -eq "openrouter") {
         Write-Ok "OpenRouter API Key -> $SelectedModel"
         Write-Color -Text "  API: openrouter.ai/api/v1 (OpenAI-compatible)" -Color DarkGray
diff --git a/quickstart.sh b/quickstart.sh
index c4669eb54e..0edb2d8c88 100755
--- a/quickstart.sh
+++ b/quickstart.sh
@@ -673,7 +673,18 @@ detect_shell_rc() {
             fi
             ;;
         bash)
-            if [ -f "$HOME/.bashrc" ]; then
+            # Git Bash on Windows commonly starts as a login shell, so prefer
+            # .bash_profile there when it already exists. On Unix-like shells,
+            # keep the traditional .bashrc-first behavior.
+            if [ -n "$MSYSTEM" ] || [ -n "$MINGW_PREFIX" ]; then
+                if [ -f "$HOME/.bash_profile" ]; then
+                    echo "$HOME/.bash_profile"
+                elif [ -f "$HOME/.bashrc" ]; then
+                    echo "$HOME/.bashrc"
+                else
+                    echo "$HOME/.profile"
+                fi
+            elif [ -f "$HOME/.bashrc" ]; then
                 echo "$HOME/.bashrc"
             elif [ -f "$HOME/.bash_profile" ]; then
                 echo "$HOME/.bash_profile"
diff --git a/tools/src/aden_tools/credentials/shell_config.py b/tools/src/aden_tools/credentials/shell_config.py
index f1e33aa294..c30fc1a787 100644
--- a/tools/src/aden_tools/credentials/shell_config.py
+++ b/tools/src/aden_tools/credentials/shell_config.py
@@ -1,13 +1,15 @@
 """
 Shell configuration utilities for persisting environment variables.
 
-Supports both bash and zsh, detecting the user's default shell.
+Supports bash and zsh with platform-aware fallbacks for login-shell config
+files such as ``.bash_profile``, ``.zshenv``, and ``.profile``.
 Used primarily for persisting ADEN_API_KEY across sessions.
 """
 
 from __future__ import annotations
 
 import os
+import platform
 import re
 from pathlib import Path
 from typing import Literal
@@ -34,9 +36,9 @@ def detect_shell() -> ShellType:
     else:
         # Try to detect from config file existence
         home = Path.home()
-        if (home / ".zshrc").exists():
+        if (home / ".zshrc").exists() or (home / ".zshenv").exists():
             return "zsh"
-        elif (home / ".bashrc").exists():
+        elif (home / ".bashrc").exists() or (home / ".bash_profile").exists():
             return "bash"
         return "unknown"
 
@@ -55,14 +57,12 @@ def get_shell_config_path(shell_type: ShellType | None = None) -> Path:
         shell_type = detect_shell()
 
     home = Path.home()
+    candidates = _get_shell_config_candidates(home, shell_type)
 
-    if shell_type == "zsh":
-        return home / ".zshrc"
-    elif shell_type == "bash":
-        return home / ".bashrc"
-    else:
-        # Default to .bashrc for unknown shells
-        return home / ".bashrc"
+    for candidate in candidates:
+        if candidate.exists():
+            return candidate
+    return candidates[0]
 
 
 def check_env_var_in_shell_config(
@@ -79,29 +79,47 @@ def check_env_var_in_shell_config(
     Returns:
         Tuple of (exists, current_value or None)
     """
-    config_path = get_shell_config_path(shell_type)
+    if shell_type is None:
+        shell_type = detect_shell()
 
-    if not config_path.exists():
-        return False, None
+    for config_path in _get_shell_config_candidates(Path.home(), shell_type):
+        if not config_path.exists():
+            continue
 
-    content = config_path.read_text(encoding="utf-8")
+        content = config_path.read_text(encoding="utf-8")
 
-    # Look for export ENV_VAR=value or export ENV_VAR="value"
-    pattern = rf"^export\s+{re.escape(env_var)}=(.+)$"
-    match = re.search(pattern, content, re.MULTILINE)
+        # Look for export ENV_VAR=value or export ENV_VAR="value"
+        pattern = rf"^export\s+{re.escape(env_var)}=(.+)$"
+        match = re.search(pattern, content, re.MULTILINE)
 
-    if match:
-        value = match.group(1).strip()
-        # Remove surrounding quotes if present
-        if (value.startswith('"') and value.endswith('"')) or (
-            value.startswith("'") and value.endswith("'")
-        ):
-            value = value[1:-1]
-        return True, value
+        if match:
+            value = match.group(1).strip()
+            # Remove surrounding quotes if present
+            if (value.startswith('"') and value.endswith('"')) or (
+                value.startswith("'") and value.endswith("'")
+            ):
+                value = value[1:-1]
+            return True, value
 
     return False, None
 
 
+def _get_shell_config_candidates(home: Path, shell_type: ShellType) -> list[Path]:
+    """Return candidate config files in lookup order for the detected shell."""
+    if shell_type == "zsh":
+        return [home / ".zshrc", home / ".zshenv"]
+
+    if shell_type == "bash":
+        # Git Bash commonly launches login shells on Windows, so prefer
+        # ``.bash_profile`` there for writes, but keep ``.bashrc`` in the
+        # lookup list so older setups continue to work.
+        if platform.system() == "Windows":
+            return [home / ".bash_profile", home / ".bashrc", home / ".profile"]
+        return [home / ".bashrc", home / ".bash_profile", home / ".profile"]
+
+    return [home / ".profile", home / ".bashrc"]
+
+
 def add_env_var_to_shell_config(
     env_var: str,
     value: str,
diff --git a/tools/tests/test_shell_config.py b/tools/tests/test_shell_config.py
new file mode 100644
index 0000000000..3c276ec6ab
--- /dev/null
+++ b/tools/tests/test_shell_config.py
@@ -0,0 +1,90 @@
+"""Tests for shell config path selection and env-var lookups."""
+
+from pathlib import Path
+
+from aden_tools.credentials import shell_config
+
+
+def _mock_home(monkeypatch, tmp_path: Path) -> None:
+    monkeypatch.setattr(shell_config.Path, "home", staticmethod(lambda: tmp_path))
+
+
+def test_get_shell_config_path_prefers_existing_bash_profile(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/usr/bin/bash")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Windows")
+
+    (tmp_path / ".bashrc").write_text("# bashrc\n", encoding="utf-8")
+    (tmp_path / ".bash_profile").write_text("# bash profile\n", encoding="utf-8")
+
+    assert shell_config.get_shell_config_path() == tmp_path / ".bash_profile"
+
+
+def test_get_shell_config_path_prefers_bashrc_for_non_windows_bash(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/usr/bin/bash")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Linux")
+
+    (tmp_path / ".bashrc").write_text("# bashrc\n", encoding="utf-8")
+    (tmp_path / ".bash_profile").write_text("# bash profile\n", encoding="utf-8")
+
+    assert shell_config.get_shell_config_path() == tmp_path / ".bashrc"
+
+
+def test_check_env_var_in_shell_config_reads_bash_profile(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/usr/bin/bash")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Windows")
+
+    (tmp_path / ".bash_profile").write_text(
+        'export HIVE_API_KEY="hive-key-123"\n',
+        encoding="utf-8",
+    )
+
+    assert shell_config.check_env_var_in_shell_config("HIVE_API_KEY") == (
+        True,
+        "hive-key-123",
+    )
+
+
+def test_check_env_var_in_shell_config_falls_back_to_bashrc_on_windows(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/usr/bin/bash")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Windows")
+
+    (tmp_path / ".bash_profile").write_text("# no key here\n", encoding="utf-8")
+    (tmp_path / ".bashrc").write_text(
+        'export HIVE_API_KEY="hive-key-from-bashrc"\n',
+        encoding="utf-8",
+    )
+
+    assert shell_config.check_env_var_in_shell_config("HIVE_API_KEY") == (
+        True,
+        "hive-key-from-bashrc",
+    )
+
+
+def test_check_env_var_in_shell_config_reads_zshenv_when_zshrc_missing(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/bin/zsh")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Darwin")
+
+    (tmp_path / ".zshenv").write_text(
+        "export OPENROUTER_API_KEY='or-key-123'\n",
+        encoding="utf-8",
+    )
+
+    assert shell_config.check_env_var_in_shell_config("OPENROUTER_API_KEY") == (
+        True,
+        "or-key-123",
+    )
+
+
+def test_get_shell_config_path_falls_back_to_profile_for_unknown_shell(monkeypatch, tmp_path):
+    _mock_home(monkeypatch, tmp_path)
+    monkeypatch.setenv("SHELL", "/usr/bin/fish")
+    monkeypatch.setattr(shell_config.platform, "system", lambda: "Linux")
+
+    (tmp_path / ".profile").write_text("# profile\n", encoding="utf-8")
+
+    assert shell_config.get_shell_config_path() == tmp_path / ".profile"