Traceplain
FREE CODEX EXEC JSONL VIEWER · NO ACCOUNT

Turn a Codex event stream into a human review.

Capture codex exec --json, import the JSONL locally, and see recorded commands, file changes, failures, agent reports, and the decision that still needs you.

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Imported Codex activity never leaves your browser.

1. Capture a Codex exec event stream.

Use Codex’s documented JSON mode and redirect standard output to a file:

codex exec --json "run the relevant tests and explain any failures" > codex-run.jsonl

This keeps the original event order. The file may contain thread and turn state, commands, file changes, tool calls, errors, and agent messages. Review it before sharing: coding-agent logs can contain commands, paths, outputs, prompts, or other sensitive project context.

2. Import the JSONL locally.

Open the free Traceplain reviewer and choose codex-run.jsonl, or paste its contents. The browser reads the file on your device; the imported activity is not transmitted to Traceplain.

WHAT TRACEPLAIN DOES WITH CODEX EVENTS
  • uses terminal item.completed records so start/update noise does not count one action repeatedly;
  • shows command status and exit codes as recorded evidence;
  • extracts paths and change kinds from file-change items;
  • keeps MCP calls, web searches, runtime failures, and agent messages distinct;
  • does not project reasoning or todo items as activity facts.

3. Read the handback conservatively.

A completed command is evidence about that command, not proof of the intended outcome. A file-change event identifies recorded changes, not whether they were correct. A final Codex message is still a report unless the supplied events support its claims.

OBSERVED       npm test exited 0
OBSERVED       src/app.ts was updated
REPORTED       “The release is ready”
UNKNOWN        no deployment event is present
NEEDS HUMAN    inspect the diff before publishing

Supported Codex exec items.

  • command_execution — command, status, output summary, and exit code;
  • file_change — added, updated, or deleted paths;
  • mcp_tool_call — server, tool, arguments, status, and recorded error;
  • web_search — recorded query;
  • agent_message — visibly labelled as reported;
  • turn and stream errors — surfaced as failures.

Traceplain can assess only the events supplied. It cannot establish that a log is complete or that omitted activity did not occur.

QUICK ANSWERS

Codex JSONL viewer FAQ

What does codex exec --json produce?

Newline-delimited JSON events: one JSON object per state change. Traceplain focuses on terminal activity records rather than counting every update.

Does Traceplain upload my Codex log?

No. The public reviewer parses it in your browser. Aggregate counters do not contain imported activity, file names, prompts, or user identifiers.

Can a completed event prove the whole task succeeded?

No. It supports a narrower claim about that recorded event. The intended outcome may need an independent check.

Is this an official OpenAI product?

No. Traceplain is an independent local-first review tool. Codex is an OpenAI product; Traceplain consumes the documented JSONL output format.