Plexum-openai-provider/cmd/plexum-openai-provider-plugin/main.go

// plexum-openai-provider-plugin wraps the local `codex` CLI binary
// (OpenAI Codex CLI ≥ 0.135). Same CLI-driven approach as
// Plexum-gemini-provider — each Plexum turn forks one `codex exec`
// subprocess in the agent's workspace, captures JSONL output, and
// emits canonical TurnEvents.
//
// Auth: codex CLI's own ~/.codex/ state (ChatGPT login or
// OPENAI_API_KEY env). No api_key field in this plugin's config.
//
// Models: by default only "codex" (use whatever the CLI's bound
// account supports — ChatGPT login restricts model selection). If
// running on an API key, operator can add other ids via config.
package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"git.hangman-lab.top/hzhang/Plexum-sdk-go/canonical"
	"git.hangman-lab.top/hzhang/Plexum-sdk-go/mcpbridge"
	plugin "git.hangman-lab.top/hzhang/Plexum-sdk-go/plugin"

	"git.hangman-lab.top/hzhang/Plexum-openai-provider/internal/runner"
)

const pluginName = "plexum-openai-provider"

// Default model surface. "codex" → no --model flag (CLI default).
// Operator can extend via config.SupportedModels override (e.g.
// "gpt-5", "o3" — only valid on API-key accounts).
var defaultModels = []string{"codex"}

// HostConfig at <profile>/plugins/plexum-openai-provider/config.json.
// All fields optional.
//
//	{
//	  "binary":           "codex",
//	  "extra_args":       ["--enable", "some-feature"],
//	  "supported_models": ["codex","gpt-5"],   // override manifest models list
//	  "model_args": {                              // map plexum model id → --model value
//	    "gpt-5": "gpt-5"
//	  }
//	}
type HostConfig struct {
	Binary          string            `json:"binary"`
	ExtraArgs       []string          `json:"extra_args"`
	SupportedModels []string          `json:"supported_models"`
	ModelArgs       map[string]string `json:"model_args"`
}

type openaiPlugin struct {
	host plugin.HostAPI
	cfg  HostConfig
	// modelsAdvertised is the final list used for both the manifest
	// AND admission ("does the agent's model match one we serve?").
	modelsAdvertised []string
}

func (p *openaiPlugin) Manifest() plugin.Manifest {
	// Manifest is built dynamically per init so an operator's
	// supported_models override surfaces correctly.
	loaded := p.loadConfigBareForManifest()
	models := loaded.SupportedModels
	if len(models) == 0 {
		models = defaultModels
	}
	return plugin.Manifest{
		Name:       pluginName,
		Version:    "0.1.0",
		Activation: plugin.ActivationLazy,
		Executable: "plexum-openai-provider-plugin",
		Contracts: plugin.Contracts{
			Provider: &plugin.ProviderContract{Models: models},
		},
	}
}

// loadConfigBareForManifest reads the config file once during
// Manifest() (before Init runs) so the advertised model list reflects
// operator overrides without requiring a second restart cycle. Errors
// are silent — Init will surface them.
func (p *openaiPlugin) loadConfigBareForManifest() HostConfig {
	profileRoot := os.Getenv("PLEXUM_PROFILE_ROOT")
	if profileRoot == "" {
		home, _ := os.UserHomeDir()
		profileRoot = filepath.Join(home, ".plexum")
	}
	raw, _ := os.ReadFile(filepath.Join(profileRoot, "plugins", pluginName, "config.json"))
	var c HostConfig
	_ = json.Unmarshal(raw, &c)
	return c
}

func (p *openaiPlugin) Init(ctx context.Context, host plugin.HostAPI) error {
	p.host = host

	profileRoot := os.Getenv("PLEXUM_PROFILE_ROOT")
	if profileRoot == "" {
		home, _ := os.UserHomeDir()
		profileRoot = filepath.Join(home, ".plexum")
	}
	cfgPath := filepath.Join(profileRoot, "plugins", pluginName, "config.json")
	raw, err := os.ReadFile(cfgPath)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return fmt.Errorf("read %s: %w", cfgPath, err)
	}
	if len(raw) > 0 {
		if err := json.Unmarshal(raw, &p.cfg); err != nil {
			return fmt.Errorf("parse %s: %w", cfgPath, err)
		}
	}
	if p.cfg.Binary == "" {
		p.cfg.Binary = "codex"
	}
	if len(p.cfg.SupportedModels) > 0 {
		p.modelsAdvertised = p.cfg.SupportedModels
	} else {
		p.modelsAdvertised = defaultModels
	}
	host.Log("info", "openai (codex) provider initialized", map[string]any{
		"binary":     p.cfg.Binary,
		"extra_args": p.cfg.ExtraArgs,
		"models":     p.modelsAdvertised,
	})
	return nil
}

// Stream is the bare ProviderPlugin entrypoint; SDK uses
// StreamWithAgent below when AgentContext is needed.
func (p *openaiPlugin) Stream(ctx context.Context, modelID string, req canonical.TurnRequest) (<-chan canonical.TurnEvent, error) {
	return p.StreamWithAgent(ctx, modelID, plugin.AgentContext{}, req)
}

func (p *openaiPlugin) StreamWithAgent(ctx context.Context, modelID string, agent plugin.AgentContext, req canonical.TurnRequest) (<-chan canonical.TurnEvent, error) {
	cliModel := p.mapModel(modelID)
	return runner.Run(ctx, p.host, agent, cliModel, p.cfg.Binary, p.cfg.ExtraArgs, req)
}

// MutateSession is the session-mirror hook (decision #29x). codex
// rollout JSONL at ~/.codex/sessions/.../rollout-*-<thread_id>.jsonl
// is rewritten line-by-line: function_call_output entries matching
// the request's call_ids get their output replaced with the consume
// marker; heavy ops also stub function_call.arguments to "{}".
//
// Tool-call round-trip is provided by the runner package's
// ParseRolloutToolCalls + EmitCodexToolCalls (which run at end of
// each turn) — they push the codex call_X ids into Plexum's
// dynamic.jsonl, so the BlockMutations the host fires here all
// resolve.
func (p *openaiPlugin) MutateSession(ctx context.Context, req plugin.SessionMutateRequest) error {
	if len(req.Mutations) == 0 {
		return nil
	}
	mu := make([]runner.CodexMutation, 0, len(req.Mutations))
	for _, m := range req.Mutations {
		mu = append(mu, runner.CodexMutation{BlockID: m.BlockID, Op: m.Op})
	}
	touched, err := runner.MutateCodexSession(req.Workspace, mu)
	if err != nil {
		p.host.Log("warn", "codex session mutate failed", map[string]any{
			"agent": req.AgentID, "err": err.Error(),
		})
		return err
	}
	p.host.Log("info", "codex session mutate complete", map[string]any{
		"agent": req.AgentID, "touched": touched, "requested": len(req.Mutations),
	})
	return nil
}

// mapModel resolves the Plexum-advertised model id into the CLI's
// --model value. "" / "codex" → no --model flag (CLI default, only
// thing ChatGPT-account installs support).
func (p *openaiPlugin) mapModel(plexumModel string) string {
	if plexumModel == "" || plexumModel == "codex" {
		return ""
	}
	if v, ok := p.cfg.ModelArgs[plexumModel]; ok {
		return v
	}
	// Unknown id — pass through verbatim. Codex will accept or 400.
	return plexumModel
}

func main() {
	if len(os.Args) > 1 && os.Args[1] == "mcp-host" {
		if err := runMCPHost(os.Args[2:]); err != nil {
			fmt.Fprintf(os.Stderr, "mcp-host: %v\n", err)
			os.Exit(1)
		}
		return
	}
	if err := plugin.Serve(&openaiPlugin{}); err != nil {
		fmt.Fprintf(os.Stderr, "plexum-openai-provider-plugin: %v\n", err)
		os.Exit(1)
	}
}

// runMCPHost: codex registers our binary's mcp-host subcommand via
// `codex mcp add --env PLEXUM_MCP_SOCKET=...`. The mcp-host process
// reads those env vars + serves stdio MCP to codex while dialing the
// plugin-side unix socket.
func runMCPHost(argv []string) error {
	opts := mcpbridge.Opts{
		SocketPath: os.Getenv("PLEXUM_MCP_SOCKET"),
		AgentID:    os.Getenv("PLEXUM_MCP_AGENT_ID"),
	}
	for i := 0; i < len(argv); i++ {
		switch argv[i] {
		case "--socket":
			if i+1 >= len(argv) {
				return errors.New("--socket needs value")
			}
			opts.SocketPath = argv[i+1]
			i++
		case "--agent-id":
			if i+1 >= len(argv) {
				return errors.New("--agent-id needs value")
			}
			opts.AgentID = argv[i+1]
			i++
		default:
			return fmt.Errorf("unknown mcp-host flag: %s", argv[i])
		}
	}
	return mcpbridge.Run(context.Background(), opts)
}