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pelikhan merged 3 commits into from
Oct 4, 2026
Merged

Prevent Codex exec tool rejection with Copilot inference #65654

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10b887d
Initial plan
Copilot Oct 4, 2026
040d22a
Disable unsupported Codex exec for Copilot
Copilot Oct 4, 2026
a94dbe9
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Copilot Oct 4, 2026
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Disable unsupported Codex exec for Copilot 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
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@pelikhan
Copilot and pelikhan authored Oct 4, 2026
commit 040d22a042168656558f5d07cde7ba03a304aa7d
17 changes: 14 additions & 3 deletions pkg/workflow/codex_config.go
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,11 @@ func (e *CodexEngine) buildNativeConfig(workflowData *WorkflowData, mcpTools []s
Overrides: make(map[string]any),
DisablePlugins: workflowData == nil || len(workflowData.Plugins) == 0,
}
config.Defaults["features"] = map[string]any{"plugins": !config.DisablePlugins}
features := map[string]any{"plugins": !config.DisablePlugins}
if e.ResolveLLMProvider(workflowData) == LLMProviderGitHub {
features["shell_tool"] = false
}
config.Defaults["features"] = features
if isFirewallEnabled(workflowData) {
config.Defaults["model_provider"] = codexOpenAIProxyProviderID
config.Defaults["model_providers"] = map[string]any{
Expand Down Expand Up @@ -118,7 +122,7 @@ func (e *CodexEngine) buildNativeConfig(workflowData *WorkflowData, mcpTools []s
delete(config.Overrides, "mcp_servers")
}
}
if err := validateCodexManagedConfig(config, isFirewallEnabled(workflowData)); err != nil {
if err := validateCodexManagedConfig(config, isFirewallEnabled(workflowData), e.ResolveLLMProvider(workflowData) == LLMProviderGitHub); err != nil {
return nil, err
}
}
Expand Down Expand Up @@ -165,7 +169,14 @@ func codexNativeServerDefaults(workflowData *WorkflowData, mcpTools []string) ma
return servers
}

func validateCodexManagedConfig(config *codexNativeConfig, firewallEnabled bool) error {
func validateCodexManagedConfig(config *codexNativeConfig, firewallEnabled, githubProvider bool) error {
if githubProvider {
if features, ok := config.Overrides["features"].(map[string]any); ok {
if shellTool, exists := features["shell_tool"]; exists && shellTool != false {
return errors.New("engine.config: features.shell_tool is disabled for GitHub inference because the Copilot compatibility adapter does not support the Codex exec custom tool")
Comment on lines +173 to +176

@github-actions github-actions Bot Oct 4, 2026

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[/diagnosing-bugs] Root cause only partially addressed: validateCodexManagedConfig only blocks engine.config TOML overrides. But buildCodexCommand appends workflowData.EngineConfig.Args (customArgsParam) as the last segment of the generated codex exec ... command, after shellToolParam ( -c features.shell_tool=false). Since later -c flags win in Codex CLI arg parsing, a workflow with engine: {id: codex, args: ["-c", "features.shell_tool=true"]} silently re-enables the exec tool for GitHub inference, bypassing the new guard entirely.

💡 Suggested fix

Add a check (alongside/near validateCodexManagedConfig, or in buildCodexCommand) that scans workflowData.EngineConfig.Args for a features.shell_tool override when ResolveLLMProvider(workflowData) == LLMProviderGitHub, and rejects it the same way the TOML override is rejected. Add a regression test mirroring TestCodexGitHubInferenceRejectsExecToolOverride but using Args instead of Config.

@copilot please address this.

}
}
}
if rawServers, exists := config.Overrides["mcp_servers"]; exists {
servers, ok := rawServers.(map[string]any)
if !ok {
Expand Down
40 changes: 40 additions & 0 deletions pkg/workflow/codex_config_test.go
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Expand Up @@ -98,6 +98,46 @@ process.stdout.write(serializeConfig(buildConfig({github: {headers: {Authorizati
assert.Equal(t, "Bearer \"quoted\"\\token", headers["Authorization"])
}

func TestCodexGitHubInferenceDisablesUnsupportedExecTool(t *testing.T) {
for _, test := range []struct {
name string
model string
disableShell bool
}{
{name: "Copilot provider", model: "copilot/gpt-5.3-codex", disableShell: true},
{name: "OpenAI provider", model: "gpt-5.3-codex"},
} {
t.Run(test.name, func(t *testing.T) {
data := &WorkflowData{
Name: "provider-tool-config",
Model: test.model,
EngineConfig: &EngineConfig{ID: "codex"},
}
var output strings.Builder
require.NoError(t, renderCodexMCPConfigForTest(t, NewCodexEngine(), &output, map[string]any{}, nil, data))

config := decodeCodexBootstrap(t, output.String())
features := config["features"].(map[string]any)
if test.disableShell {
assert.Equal(t, false, features["shell_tool"])
} else {
assert.NotContains(t, features, "shell_tool")
}
})
}
}

func TestCodexGitHubInferenceRejectsExecToolOverride(t *testing.T) {
_, err := NewCodexEngine().buildNativeConfig(&WorkflowData{
Model: "copilot/gpt-5.3-codex",
EngineConfig: &EngineConfig{
ID: "codex",
Config: "[features]\nshell_tool = true",
},
}, nil)
require.ErrorContains(t, err, "does not support the Codex exec custom tool")
}

func TestCodexNativeConfigShellEnvironment(t *testing.T) {
data := &WorkflowData{
EngineConfig: &EngineConfig{Env: map[string]string{
Expand Down
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