From 4d2d9a421241f1b8b4a92456a5c885bd92ef1ec8 Mon Sep 17 00:00:00 2001
From: Charles Green <hello@charles.green>
Date: Sat, 19 Sep 2026 20:12:43 +0900
Subject: [PATCH] feat(gemini): default model to gemini-3.5-flash

Replace the gemini-2.5-pro remap (empty / gpt-5.4) with gemini-3.5-flash
for Vertex coding loops. Sync already overrides via caller model input.
---
 README.md                             | 2 +-
 cmd/aixgo-code/init_select.go         | 2 +-
 cmd/aixgo-code/main.go                | 2 +-
 cmd/aixgo-code/main_test.go           | 6 +++---
 internal/engine/gemini/gemini_test.go | 4 ++--
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index 569eba4..6a693da 100644
--- a/README.md
+++ b/README.md
@@ -249,7 +249,7 @@ export AIXGO_VERTEX_LOCATION="us-central1"   # optional
 export AIXGO_VERTEX_API_KEY="<key-or-sa-json>"
 ```
 
-In GitHub Actions, pass reusable-workflow inputs `vertex-project`, `vertex-location`, and secret `vertex-api-key` instead of Azure. The workflow installs `@google/gemini-cli` when `vertex-project` is set. Default model is `gemini-2.5-pro` (override with `--model` / workflow `model:`).
+In GitHub Actions, pass reusable-workflow inputs `vertex-project`, `vertex-location`, and secret `vertex-api-key` instead of Azure. The workflow installs `@google/gemini-cli` when `vertex-project` is set. Default model is `gemini-3.5-flash` (override with `--model` / workflow `model:`).
 
 ## Deployment model
 
diff --git a/cmd/aixgo-code/init_select.go b/cmd/aixgo-code/init_select.go
index d87d334..23c4706 100644
--- a/cmd/aixgo-code/init_select.go
+++ b/cmd/aixgo-code/init_select.go
@@ -295,7 +295,7 @@ func callerEngineBlocks(engine string) (inputs, secrets string) {
 	case "gemini":
 		inputs = "      vertex-project: ${{ vars.AIXGO_VERTEX_PROJECT }}\n" +
 			"      vertex-location: ${{ vars.AIXGO_VERTEX_LOCATION }}\n" +
-			"      # model: gemini-2.5-pro"
+			"      # model: gemini-3.5-flash"
 		secrets = "      vertex-api-key: ${{ secrets.AIXGO_VERTEX_API_KEY }}\n" +
 			"      github-app-private-key: ${{ secrets.AIXGO_GH_APP_PRIVATE_KEY }}"
 	case "claude":
diff --git a/cmd/aixgo-code/main.go b/cmd/aixgo-code/main.go
index ebc2557..d9cfff7 100644
--- a/cmd/aixgo-code/main.go
+++ b/cmd/aixgo-code/main.go
@@ -229,7 +229,7 @@ func newRunner(cfg *config.Config, codexHome, model string) engine.Runner {
 	}
 	if cfg.Engine == "gemini" {
 		if model == "" || model == "gpt-5.4" {
-			model = "gemini-2.5-pro"
+			model = "gemini-3.5-flash"
 		}
 		return &gemini.Runner{Model: model}
 	}
diff --git a/cmd/aixgo-code/main_test.go b/cmd/aixgo-code/main_test.go
index 7d6916d..93bbd23 100644
--- a/cmd/aixgo-code/main_test.go
+++ b/cmd/aixgo-code/main_test.go
@@ -1079,11 +1079,11 @@ func TestNewRunnerSelectsTheEngine(t *testing.T) {
 	if !ok {
 		t.Fatal("engine: gemini must select the Gemini adapter")
 	}
-	if g.Model != "gemini-2.5-pro" {
-		t.Fatalf("gemini default model = %q, want gemini-2.5-pro", g.Model)
+	if g.Model != "gemini-3.5-flash" {
+		t.Fatalf("gemini default model = %q, want gemini-3.5-flash", g.Model)
 	}
 	g2, _ := newRunner(&config.Config{Engine: "gemini"}, t.TempDir(), "gpt-5.4").(*gemini.Runner)
-	if g2.Model != "gemini-2.5-pro" {
+	if g2.Model != "gemini-3.5-flash" {
 		t.Fatalf("the Codex default must not be forwarded to Gemini: %q", g2.Model)
 	}
 	g3, _ := newRunner(&config.Config{Engine: "gemini"}, t.TempDir(), "gemini-2.5-flash").(*gemini.Runner)
diff --git a/internal/engine/gemini/gemini_test.go b/internal/engine/gemini/gemini_test.go
index 7512539..9e44b3d 100644
--- a/internal/engine/gemini/gemini_test.go
+++ b/internal/engine/gemini/gemini_test.go
@@ -34,12 +34,12 @@ func TestRunPassesThePromptAndModel(t *testing.T) {
 	r.Bin = writeFakeGemini(t, echoArgs)
 	res, err := r.Run(context.Background(), domain.RunRequest{
 		Role: domain.RoleImplementer, WorkDir: t.TempDir(),
-		Prompt: "do the thing", Model: "gemini-2.5-pro",
+		Prompt: "do the thing", Model: "gemini-3.5-flash",
 	})
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	for _, want := range []string{"-p", "do the thing", "-m", "gemini-2.5-pro"} {
+	for _, want := range []string{"-p", "do the thing", "-m", "gemini-3.5-flash"} {
 		if !strings.Contains(res.Summary, want) {
 			t.Fatalf("args missing %q: %s", want, res.Summary)
 		}