fix(proxy): preserve opencode CLI client identity to upstream

opencode CLI sends Originator: opencode and a non-codex User-Agent. The
previous logic at executor.go:514 only honored codex_* prefixes, so
opencode's identity was rewritten to codex_cli_rs. The Codex upstream then
silently downgraded reasoning_effort=xhigh, which is the symptom reported
in issue #65 (xhigh shown in admin panel but no thinking output).

Add "opencode" to the official originator/UA prefix lists so opencode's
real identity flows through unchanged, matching CLIProxyAPI's behavior.

Closes #65

Author: james-6-23

proxy/executor_test.go

@@ -290,7 +290,7 @@ func TestApplyCodexRequestHeadersFallsBackForNonOfficialClient(t *testing.T) {
 	acc := &auth.Account{DBID: 42}
 	downstreamHeaders := http.Header{
 		"User-Agent": []string{"curl/8.0"},
-		"Originator": []string{"opencode"},
+		"Originator": []string{"random-client"},
 	}
 
 	applyCodexRequestHeaders(req, acc, "token-123", "", "api-key-1", nil, downstreamHeaders)
@@ -306,6 +306,31 @@ func TestApplyCodexRequestHeadersFallsBackForNonOfficialClient(t *testing.T) {
 	}
 }
 
+func TestApplyCodexRequestHeadersPreservesOpenCodeClient(t *testing.T) {
+	prev := CurrentRuntimeSettings()
+	ApplyRuntimeSettings(RuntimeSettings{ClientCompatMode: ClientCompatModePreserve})
+	t.Cleanup(func() { ApplyRuntimeSettings(prev) })
+
+	req, err := http.NewRequest(http.MethodPost, "https://example.com/v1/responses", nil)
+	if err != nil {
+		t.Fatalf("http.NewRequest() error = %v", err)
+	}
+	acc := &auth.Account{DBID: 42, AccountID: "acct-42"}
+	downstreamHeaders := http.Header{
+		"User-Agent": []string{"opencode/0.5.0"},
+		"Originator": []string{"opencode"},
+	}
+
+	applyCodexRequestHeaders(req, acc, "token-123", "", "api-key-1", nil, downstreamHeaders)
+
+	if got := req.Header.Get("User-Agent"); got != "opencode/0.5.0" {
+		t.Fatalf("User-Agent = %q, want %q", got, "opencode/0.5.0")
+	}
+	if got := req.Header.Get("Originator"); got != "opencode" {
+		t.Fatalf("Originator = %q, want %q", got, "opencode")
+	}
+}
+
 func TestCodexTransportModeDefaultsToStandard(t *testing.T) {
 	t.Setenv("CODEX_TRANSPORT_MODE", "")
 	if _, ok := newCodexTransport("").(*http.Transport); !ok {

proxy/useragent.go

@@ -36,11 +36,16 @@ var codexOfficialClientUserAgentPrefixes = []string{
 	"codex_exec/",
 	"codex_sdk_ts/",
 	"codex ",
+	"opencode/",
 }
 
+// Third-party CLIs that ChatGPT-backend Codex accepts as first-party originators.
+// opencode advertises itself via Originator: "opencode" and reaching upstream with
+// that identity is required for features like reasoning_effort=xhigh to take effect.
 var codexOfficialClientOriginatorPrefixes = []string{
 	"codex_",
 	"codex ",
+	"opencode",
 }
 
 func IsCodexOfficialClientByHeaders(userAgent, originator string) bool {

proxy/useragent_test.go

@@ -38,7 +38,9 @@ func TestIsCodexOfficialClientByHeaders(t *testing.T) {
 		{name: "cli ua", userAgent: "codex_cli_rs/0.128.0", want: true},
 		{name: "vscode ua", userAgent: "codex_vscode/1.2.3", want: true},
 		{name: "desktop originator", originator: "codex_chatgpt_desktop", want: true},
-		{name: "non official", userAgent: "curl/8.0", originator: "opencode", want: false},
+		{name: "opencode ua", userAgent: "opencode/0.5.0", want: true},
+		{name: "opencode originator", originator: "opencode", want: true},
+		{name: "non official", userAgent: "curl/8.0", originator: "random-client", want: false},
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {