diff --git a/internal/provider/opencode_client.go b/internal/provider/opencode_client.go
index 73d3405e..19068a18 100644
--- a/internal/provider/opencode_client.go
+++ b/internal/provider/opencode_client.go
@@ -15,6 +15,10 @@ import (
 // "OpenCode 1.18.0 or newer is required to use the free tier").
 const OpenCodeVersion = "1.18.34"
 
+// OpenCodeAnonymousKey is the key OpenCode asks Zen with when no one is
+// signed in to it, which Zen's free models answer.
+const OpenCodeAnonymousKey = "public"
+
 // OpenCodeClient makes a request to OpenCode's gateway (Zen or Go) carry
 // what OpenCode itself sends there (packages/opencode/src/session/llm/
 // request.ts, for a provider whose id starts with "opencode"): its
diff --git a/internal/provider/opencode_zen_test.go b/internal/provider/opencode_zen_test.go
index 028b7751..5d0c9b36 100644
--- a/internal/provider/opencode_zen_test.go
+++ b/internal/provider/opencode_zen_test.go
@@ -2,6 +2,7 @@ package provider
 
 import (
 	"encoding/json"
+	"path/filepath"
 	"testing"
 
 	"github.com/yetone/magpie/internal/catalog"
@@ -43,3 +44,42 @@ func TestZenFreeProbe(t *testing.T) {
 		}
 	}
 }
+
+// #572: an OpenCode Zen provider added with no key asks with the one
+// OpenCode sends signed out, which Zen's free models answer; a key of the
+// user's own is kept.
+func TestOpenCodeZenNeedsNoKey(t *testing.T) {
+	isolate(t)
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+	t.Setenv("XDG_CONFIG_HOME", filepath.Join(home, ".config"))
+	t.Setenv("XDG_CACHE_HOME", filepath.Join(home, ".cache"))
+	p, err := FromPreset("opencode-zen")
+	if err != nil {
+		t.Fatal(err)
+	}
+	p.Models = []string{"mimo-v2.6-flash-free"}
+	id, err := Add(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := Find(id)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Key != OpenCodeAnonymousKey {
+		t.Fatalf("key %q", got.Key)
+	}
+	p.Name, p.Key = "Zen paid", "sk-own"
+	if id, err = Add(p); err != nil {
+		t.Fatal(err)
+	}
+	if got, _ = Find(id); got.Key != "sk-own" {
+		t.Fatalf("own key %q", got.Key)
+	}
+	// another provider still needs one
+	if _, err := Add(Provider{Name: "Relay", Chat: "https://api.relay.example/v1", Models: []string{"m"}}); err == nil {
+		t.Fatal("a relay with no key")
+	}
+}
diff --git a/internal/provider/presets.go b/internal/provider/presets.go
index 4d4038db..a9fa6531 100644
--- a/internal/provider/presets.go
+++ b/internal/provider/presets.go
@@ -312,8 +312,9 @@ var presets = []PresetDef{
 		Models: []string{"cline-pass/glm-5.3", "cline-pass/glm-5.3-flash", "cline-pass/kimi-k3", "cline-pass/deepseek-v4-pro",
 			"cline-pass/deepseek-v4.1-flash", "cline-pass/mimo-v2.5", "cline-pass/mimo-v2.5-pro", "cline-pass/minimax-m3",
 			"cline-pass/muse-spark-1.3-contributor", "cline-pass/qwen3.8-max", "cline-pass/qwen3.7-max", "cline-pass/qwen3.7-plus"}},
-	{ID: "opencode-zen", Name: "OpenCode Zen", Icon: "opencode", Kind: KindRelay, Catalog: "opencode",
-		Chat: "https://opencode.ai/zen/v1", Responses: "https://opencode.ai/zen/v1", Anthropic: "https://opencode.ai/zen",
+	{ID: "opencode-zen", Name: "OpenCode Zen", Icon: "opencode", Kind: KindRelay, Catalog: "opencode", NoKey: true,
+		KeyHint: "optional: free models need no key",
+		Chat:    "https://opencode.ai/zen/v1", Responses: "https://opencode.ai/zen/v1", Anthropic: "https://opencode.ai/zen",
 		// its free models (-free) are served to OpenCode alone, which
 		// magpie asks them as (OpenCodeFree)
 		Website: "https://opencode.ai/docs/zen", KeysURL: "https://opencode.ai/auth"},
diff --git a/internal/provider/provider.go b/internal/provider/provider.go
index f47744fb..c648777e 100644
--- a/internal/provider/provider.go
+++ b/internal/provider/provider.go
@@ -694,6 +694,12 @@ func normalize(p Provider) Provider {
 	if p.Preset == "qianfan-token-plan" {
 		p.Preset = "baidu-qianfan"
 	}
+	// OpenCode Zen serves its free models (-free) signed out, to the key
+	// OpenCode itself sends then: a Zen provider saved with no key of its
+	// own asks with that one
+	if p.Preset == "opencode-zen" && p.Key == "" {
+		p.Key = OpenCodeAnonymousKey
+	}
 	if p.Routing != Ordered && p.Routing != Rotate && p.Routing != LeastUsed && p.Routing != Pace {
 		p.Routing = ""
 	}