Codex Session Log

Codex Session Log

Use local Codex JSONL session logs as evidence for what happened in a session. Keep product-behavior claims narrow: session logs show local observed behavior, not a complete API contract.

Locate The Log

• Current-session logs live under ${CODEX_HOME:-$HOME/.codex}/sessions/YYYY/MM/DD/rollout-*.jsonl.
• Generated images live under ${CODEX_HOME:-$HOME/.codex}/generated_images/<session-id>/.
• The <session-id> in a generated image path usually matches part of the rollout filename. Use that to connect an image file back to the session log.
• Prefer exact file:line references after verifying with the JSONL file in the current session.

Read Safely

Do not print raw image-generation lines directly. They may contain multi-megabyte base64 result fields.

Use a parser that preserves line numbers and suppresses result:

python3 - <<'PY'
import json
from pathlib import Path

p = Path("/path/to/rollout.jsonl")
for line_no, line in enumerate(p.open(), 1):
    obj = json.loads(line)
    payload = obj.get("payload") or {}
    if payload.get("type") in {"image_generation_end", "image_generation_call"}:
        result = payload.get("result")
        print({
            "line": line_no,
            "top_type": obj.get("type"),
            "payload_type": payload.get("type"),
            "id": payload.get("id") or payload.get("call_id"),
            "status": payload.get("status"),
            "has_revised_prompt": payload.get("revised_prompt") is not None,
            "revised_prompt": payload.get("revised_prompt"),
            "result_length": len(result) if isinstance(result, str) else None,
            "saved_path": payload.get("saved_path"),
        })
PY

For quick text searches, use rg with a specific id or phrase. Avoid broad rg revised_prompt across all logs unless the output is capped.

Image Generation Events

Observed local Codex behavior on 2026-04-25:

• image_generation_end and image_generation_call entries can both contain id or call_id, status, revised_prompt, and base64 result.
• status may read "generating" even when result and saved_path are present and the PNG exists. Treat result/saved_path/file existence as stronger evidence that the image was produced.
• For the tested built-in image call ig_08a386783c3320180169ec847406088191a3ec4b54360831bc, revised_prompt was byte-for-byte identical to the submitted prompt recorded in the sidecar. Do not assume revised_prompt is an improved or model-expanded prompt unless you compare it to the submitted prompt for that call.
• PNG metadata may include C2PA/JUMBF provenance such as OpenAI generator data. Do not expect embedded submitted prompt, revised prompt, usage, or request id in the PNG.

Evidence Rules

• Quote the JSONL path and line number when reporting a log finding.
• If comparing a revised_prompt, state what it was compared against: raw tool-call arguments, a sidecar submitted_prompt, or another explicit source.
• If the raw tool-call arguments are not visible in the JSONL, say so. A matching sidecar is useful evidence, but it is not the same as seeing the tool invocation arguments.
• Do not paste base64 result fields into sidecars, reports, commits, or chat unless Jörn explicitly asks for raw payload recovery.
• After context compaction, older log lines may still exist even when they are no longer in model context. Prefer the JSONL file over memory.