[123XieC]

Description

A corrupt record near the start of one Codex rollout can cause the entire source discovery pass to fail, including unrelated sessions. A malformed JSON line can also hide the native session ID and provider even when a valid session_meta record follows.

Human Involvement

• A human participated in the implementation or review loop
• This PR was generated entirely by AI agents without human participation in the loop

Related Issue

Fixes #7655

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Changes Made

• Skip malformed JSON and records of the wrong shape while looking for the first object-shaped session_meta payload. This matches the incremental reader's per-record recovery.
• Keep the existing fallback when there is no readable metadata. A test exercises discovery of two files and reads the first file's assistant message with the recovered provider.

Testing

• Regression tests added. The incomplete JSON, JSON array, and scalar metadata payload cases all fail on the base. Existing clean and forked rollouts pass on the base.
• python -m pytest -o addopts='' -q tests/ingest — 40 passed on macOS with Python 3.12.16. No live model or server calls.
• ruff check, ruff format --check, and git diff --check pass for the changes.

Checklist

• Code style and diff reviewed.