Feature: richer Codex metrics and request inspection commands #6

Summary

Extend the plugin's diagnostics with Codex-style metrics and request inspection commands (e.g. /codex-metrics, /codex-inspect) that expose structured information similar to ResponsesRequest in openai/codex.

Background

In openai/codex:

• codex-rs/core/tests/common/responses.rs and core/tests/suite/tool_harness.rs use a ResponsesRequest helper to inspect:
  • body_json, input, function_call_output, custom_tool_call_output, call_output, header, path, query_param.
• Tests assert fine-grained behaviors around tool calls, request paths, and payload structure.

In this plugin:

• We already have a /codex-metrics command and logging controlled by ENABLE_PLUGIN_REQUEST_LOGGING.
• We also track basic cache and instruction metrics.

There is still room to provide more structured, Codex-CLI-like diagnostics that make it easier to debug tool calls, prompt caching, and request transformation.

Proposed Features

1. Enhanced /codex-metrics output

   • Include per-session counters for:
     • Number of Codex requests made.
     • Cache hits vs misses vs "no cache key" cases.
     • Number of tool calls, broken down by tool type (shell, apply_patch, custom tools, MCP tools).
     • Number of compaction events (once plugin-level compaction is implemented).
   • Surface the current normalized model and reasoning config (effort/summary/verbosity) as seen by the plugin.

2. New /codex-inspect command

   • Provide a command that prints the last N Codex requests in a structured way (similar to ResponsesRequest):
     • HTTP method, path, and key headers (e.g. chatgpt-account-id, beta headers).
     • The transformed request body:
       • model, prompt_cache_key, store, stream, include.
       • tools and tool_choice / parallel_tool_calls after normalization.
       • input after filtering (stripped IDs, filtered system prompts, injected bridge/tool-remap message).
   • Provide safe redaction for sensitive values (e.g. tokens, account IDs) so inspection is safe to use in logs or bug reports.

3. Optional JSON output for automation

   • Allow /codex-inspect to return a JSON-encoded structure when a flag is present (e.g. /codex-inspect --json) so that advanced users can pipe it into other tools.

4. Testing and observability

   • Add tests that:
     • Verify /codex-metrics and /codex-inspect work without making additional network calls.
     • Ensure redaction logic is applied correctly (no secrets leaked in snapshots).
     • Exercise edge cases like empty history, no tools, and multiple requests per session.

Rationale

• Brings the plugin's debugging experience closer to Codex CLI's ResponsesRequest-driven tests and tooling.
• Makes it much easier to debug complex tool flows and caching behavior from within opencode.
• Provides a natural place to hang future diagnostics (e.g. model upgrades, parallel tool-call behavior, compaction metrics).

Acceptance Criteria

• /codex-metrics exposes richer per-session stats without regressing existing output.
• /codex-inspect can show at least the last request in a structured, partially redacted way.
• JSON output option is available and documented.
• Tests cover the major paths and redaction behavior.