diff --git a/README.md b/README.md
index b76f3da..dc23698 100644
--- a/README.md
+++ b/README.md
@@ -133,7 +133,6 @@ Supported engines:
 
 - `claude`
 - `agy` (Antigravity CLI)
-- `gemini` (deprecated — see note below)
 - `codex`
 
 Built-in defaults are applied when `engines.<name>.args` is not set.
@@ -142,9 +141,9 @@ For `claude`, defaults include:
 - `-p --model haiku`
 - `--settings "{\"attribution\":{\"commit\":\"\",\"pr\":\"\"}}"` (prevents automatic `Co-authored-by` metadata)
 
-If no engine is configured, auto-detection tries commands in this order: `claude` → `agy` → `gemini` → `codex`. The first available command is used.
+If no engine is configured, auto-detection tries commands in this order: `claude` → `agy` → `codex`. The first available command is used.
 
-> **Gemini CLI deprecation:** Google is transitioning Gemini CLI to Antigravity CLI (`agy`). After **June 18, 2026**, Gemini CLI stops serving requests for Google AI Pro/Ultra subscribers and free users. Gemini CLI continues to work for users on Gemini Code Assist Standard/Enterprise or paid API keys. If you previously used `engine = "gemini"`, switch to `engine = "agy"`.
+> **Gemini CLI removal:** Google replaced Gemini CLI with Antigravity CLI (`agy`), and Gemini CLI stopped serving requests for Google AI Pro/Ultra subscribers and free users on **June 18, 2026**. `gemini` is no longer a built-in engine: it is not auto-detected (with only Gemini CLI installed you get `no engine configured`), and `engine = "gemini"` without explicit arguments now fails with a message pointing at `agy`. Switch to `engine = "agy"`, or keep running Gemini CLI by setting `engines.gemini.args` yourself.
 
 Any other engine name is treated as a direct command and executed with the prompt on stdin.
 
diff --git a/internal/app/app.go b/internal/app/app.go
index 303ef64..b5a970d 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -122,6 +122,9 @@ func selectEngine(cfg config.Config) (engine.Engine, string, error) {
 	if args, ok := config.DefaultEngineArgs[name]; ok {
 		return engine.CLI{Command: name, Args: args}, strings.Join(append([]string{name}, args...), " "), nil
 	}
+	if name == "gemini" {
+		return nil, "", fmt.Errorf("engine %q is no longer built in: Gemini CLI was replaced by Antigravity CLI. Use engine = \"agy\", or set engines.gemini.args explicitly", name)
+	}
 	return engine.CLI{Command: name, Args: nil}, name, nil
 }
 
diff --git a/internal/app/app_test.go b/internal/app/app_test.go
index 61e4836..9516e48 100644
--- a/internal/app/app_test.go
+++ b/internal/app/app_test.go
@@ -158,16 +158,32 @@ func TestSelectEngineCursorAgentDefault(t *testing.T) {
 	}
 }
 
-func TestSelectEngineGeminiDefault(t *testing.T) {
+func TestSelectEngineGeminiWithoutArgsFails(t *testing.T) {
 	cfg := config.Default()
 	cfg.DefaultEngine = "gemini"
 	cfg.Engines = map[string]config.EngineConfig{}
 
+	_, _, err := selectEngine(cfg)
+	if err == nil {
+		t.Fatalf("selectEngine error = nil, want a migration error")
+	}
+	if !strings.Contains(err.Error(), "agy") {
+		t.Fatalf("selectEngine error = %v, want it to suggest agy", err)
+	}
+}
+
+func TestSelectEngineGeminiWithExplicitArgs(t *testing.T) {
+	cfg := config.Default()
+	cfg.DefaultEngine = "gemini"
+	cfg.Engines = map[string]config.EngineConfig{
+		"gemini": {Args: []string{"-p", "{{prompt}}"}},
+	}
+
 	_, command, err := selectEngine(cfg)
 	if err != nil {
 		t.Fatalf("selectEngine error: %v", err)
 	}
-	if command != "gemini -m gemini-2.5-flash -p {{prompt}}" {
+	if command != "gemini -p {{prompt}}" {
 		t.Fatalf("command = %q", command)
 	}
 }
diff --git a/internal/config/config.go b/internal/config/config.go
index 7f3ff44..5453b7d 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -55,7 +55,6 @@ var DefaultEngineArgs = map[string][]string{
 	"codex":        {"exec", "--model", "gpt-5.6-luna"},
 	"claude":       {"-p", "--model", "haiku", "--settings", "{\"attribution\":{\"commit\":\"\",\"pr\":\"\"}}", "--no-session-persistence"},
 	"cursor-agent": {"-p"},
-	"gemini":       {"-m", "gemini-2.5-flash", "-p", "{{prompt}}"},
 	"agy":          {"-p", "{{prompt}}"},
 }
 
@@ -354,7 +353,7 @@ func LoadPromptPreset(name string) (string, error) {
 }
 
 func autodetectEngine() string {
-	candidates := []string{"claude", "agy", "gemini", "codex"}
+	candidates := []string{"claude", "agy", "codex"}
 	for _, name := range candidates {
 		if _, err := exec.LookPath(name); err == nil {
 			return name
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index df51b19..2930754 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -65,7 +65,7 @@ func TestAutodetectEngineOrder(t *testing.T) {
 		t.Fatalf("mkdir bin: %v", err)
 	}
 	makeExecutable(t, binDir, "codex")
-	makeExecutable(t, binDir, "gemini")
+	makeExecutable(t, binDir, "agy")
 	makeExecutable(t, binDir, "claude")
 
 	t.Setenv("PATH", binDir)
@@ -82,14 +82,35 @@ func TestAutodetectEngineOrder(t *testing.T) {
 	})
 }
 
-func TestAutodetectEnginePrefersAgyOverGemini(t *testing.T) {
+func TestAutodetectEngineIgnoresGemini(t *testing.T) {
 	configHome := t.TempDir()
 	binDir := filepath.Join(configHome, "bin")
 	if err := os.MkdirAll(binDir, 0o755); err != nil {
 		t.Fatalf("mkdir bin: %v", err)
 	}
-	makeExecutable(t, binDir, "codex")
 	makeExecutable(t, binDir, "gemini")
+
+	t.Setenv("PATH", binDir)
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
+
+	withDir(t, t.TempDir(), func() {
+		cfg, err := Load()
+		if err != nil {
+			t.Fatalf("Load error: %v", err)
+		}
+		if cfg.DefaultEngine != "" {
+			t.Fatalf("DefaultEngine = %q, want empty (gemini is no longer autodetected)", cfg.DefaultEngine)
+		}
+	})
+}
+
+func TestAutodetectEnginePrefersAgyOverCodex(t *testing.T) {
+	configHome := t.TempDir()
+	binDir := filepath.Join(configHome, "bin")
+	if err := os.MkdirAll(binDir, 0o755); err != nil {
+		t.Fatalf("mkdir bin: %v", err)
+	}
+	makeExecutable(t, binDir, "codex")
 	makeExecutable(t, binDir, "agy")
 
 	t.Setenv("PATH", binDir)
@@ -106,6 +127,12 @@ func TestAutodetectEnginePrefersAgyOverGemini(t *testing.T) {
 	})
 }
 
+func TestDefaultEngineArgsHasNoGemini(t *testing.T) {
+	if _, ok := DefaultEngineArgs["gemini"]; ok {
+		t.Fatalf("DefaultEngineArgs still contains gemini")
+	}
+}
+
 func makeExecutable(t *testing.T, dir, name string) {
 	t.Helper()
 	path := filepath.Join(dir, name)
@@ -134,7 +161,7 @@ func TestLoadRepoConfigOverrides(t *testing.T) {
 		t.Fatalf("mkdir config dir: %v", err)
 	}
 	configPath := filepath.Join(configDir, "config.toml")
-	if err := os.WriteFile(configPath, []byte("engine = 'gemini'\n"), 0o644); err != nil {
+	if err := os.WriteFile(configPath, []byte("engine = 'agy'\n"), 0o644); err != nil {
 		t.Fatalf("write xdg config: %v", err)
 	}
 
@@ -576,7 +603,7 @@ func TestNonHiddenRepoConfigPrecedence(t *testing.T) {
 		t.Fatalf("write non-hidden config: %v", err)
 	}
 	hidden := filepath.Join(repo, ".git-ai-commit.toml")
-	if err := os.WriteFile(hidden, []byte("engine = 'gemini'\n"), 0o644); err != nil {
+	if err := os.WriteFile(hidden, []byte("engine = 'agy'\n"), 0o644); err != nil {
 		t.Fatalf("write hidden config: %v", err)
 	}
 
diff --git a/internal/config/gitconfig_test.go b/internal/config/gitconfig_test.go
index a39269a..164a014 100644
--- a/internal/config/gitconfig_test.go
+++ b/internal/config/gitconfig_test.go
@@ -258,9 +258,9 @@ func TestGitConfigLocalOverridesRepoToml(t *testing.T) {
 	isolateGitConfig(t)
 	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
 
-	// Repo TOML sets engine to "gemini"
+	// Repo TOML sets engine to "agy"
 	repoConfig := filepath.Join(repo, ".git-ai-commit.toml")
-	if err := os.WriteFile(repoConfig, []byte("engine = 'gemini'\n"), 0o644); err != nil {
+	if err := os.WriteFile(repoConfig, []byte("engine = 'agy'\n"), 0o644); err != nil {
 		t.Fatalf("write repo config: %v", err)
 	}
 	trustRepoConfig(t, repo, repoConfig)
@@ -285,14 +285,14 @@ func TestGitConfigLocalOverridesUserToml(t *testing.T) {
 	repo := initTestRepo(t)
 	isolateGitConfig(t)
 
-	// User TOML sets engine to "gemini"
+	// User TOML sets engine to "agy"
 	configHome := t.TempDir()
 	t.Setenv("XDG_CONFIG_HOME", configHome)
 	configDir := filepath.Join(configHome, "git-ai-commit")
 	if err := os.MkdirAll(configDir, 0o755); err != nil {
 		t.Fatalf("mkdir config dir: %v", err)
 	}
-	if err := os.WriteFile(filepath.Join(configDir, "config.toml"), []byte("engine = 'gemini'\n"), 0o644); err != nil {
+	if err := os.WriteFile(filepath.Join(configDir, "config.toml"), []byte("engine = 'agy'\n"), 0o644); err != nil {
 		t.Fatalf("write user config: %v", err)
 	}
 
@@ -316,9 +316,9 @@ func TestGitConfigGlobalOverriddenByUserToml(t *testing.T) {
 	tmp := t.TempDir()
 	t.Setenv("GIT_CONFIG_NOSYSTEM", "1")
 
-	// Global git config sets engine to "gemini"
+	// Global git config sets engine to "agy"
 	globalCfg := filepath.Join(tmp, "global.gitconfig")
-	if err := os.WriteFile(globalCfg, []byte("[ai-commit]\n\tengine = gemini\n"), 0o644); err != nil {
+	if err := os.WriteFile(globalCfg, []byte("[ai-commit]\n\tengine = agy\n"), 0o644); err != nil {
 		t.Fatalf("write global config: %v", err)
 	}
 	t.Setenv("GIT_CONFIG_GLOBAL", globalCfg)
diff --git a/scripts/release-check.sh b/scripts/release-check.sh
index 2793159..361dd03 100755
--- a/scripts/release-check.sh
+++ b/scripts/release-check.sh
@@ -8,7 +8,7 @@ TIMESTAMP=$(date +%Y%m%d-%H%M%S)
 REPORT_DIR="$REPORT_BASE/acceptance-$TIMESTAMP"
 SUMMARY="$REPORT_DIR/summary.md"
 
-ENGINES="claude gemini codex"
+ENGINES="claude agy codex"
 PRESETS="conventional default gitmoji karma"
 
 mkdir -p "$REPORT_DIR"
@@ -44,12 +44,12 @@ engine = "claude"
 args = ["-p", "--model", "haiku"]
 EOC
         ;;
-      gemini)
+      agy)
         cat > "$tmp_cfg/git-ai-commit/config.toml" <<'EOC'
-engine = "gemini"
+engine = "agy"
 
-[engines.gemini]
-args = ["-m", "gemini-2.5-flash", "-p", "{{prompt}}"]
+[engines.agy]
+args = ["-p", "{{prompt}}"]
 EOC
         ;;
       codex)