# Session Analysis: rollout-2026-01-30T16-43-54-019c0fca-2e0c-79c2-97c6-b28f29740c4b.jsonl

**Date**: 2026-01-30 | **Duration**: 177s | **Turns**: 5 | **Model**: gpt-5.2-codex
**Type**: bug-fix | **Outcome**: abandoned | **Specificity**: 5/5 | **Struggle**: 4/10

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## Journey

The developer was debugging a NumPy `KeyError` in a cold-ranker ML training pipeline. The error originated in `col/src/model/training.py` at line 198, where `ints_data[:,0]` was being called on an `NpzFile` object (a zip archive) instead of a raw ndarray. The developer pasted the full stack trace into Codex running in read-only sandbox mode.

Codex began investigating: it read `training.py`, `dataset.py`, searched for all `ints.npz`/`floats.npz` references across the codebase, inspected `utils.py` and `recommend.py`, and searched for all `np.load` usages. However, the sandbox initially blocked file reads (landlock error), requiring escalation on each subsequent command. While Codex was still in its investigation phase (7 tool calls completed, no response delivered yet), the developer aborted the session.

## Prompting Assessment (5/5)

**What worked:**
The developer provided an excellent bug report: the full stack trace with file paths, line numbers, and the exact error message. The active file and open tabs gave Codex immediate context about the codebase structure.

> "python driver.py \nDevice: cuda\nData loaded from ../../data/hi/cat_columns_to_mapper.pkl\nTraceback (most recent call last):\n  File \"/home/ubuntu/nikhil/cold-ranker/col/src/driver.py\", line 34, in <module>\n    main()\n  File \"/home/ubuntu/nikhil/cold-ranker/col/src/driver.py\", line 28, in main\n    training.driver()\n  File \"/home/ubuntu/nikhil/cold-ranker/col/src/model/training.py\", line 219, in driver\n    pos_series_arr = get_pos_series(train_shard_dir, test_shard_dir, MODE)\n  File \"/home/ubuntu/nikhil/cold-ranker/col/src/model/training.py\", line 198, in get_pos_series\n    pos_series_arr_shard = ints_data[:,0]\n  File \"/home/ubuntu/nikhil/pyG/nik_gpu/lib/python3.10/site-packages/numpy/lib/npyio.py\", line 263, in __getitem__\n    raise KeyError(f\"{key} is not a file in the archive\")\nKeyError: '(slice(None, None, None), 0) is not a file in the archive'"

**What was vague or could improve:**
Nothing was vague in the prompt itself. The session was abandoned before completion, not due to a prompting issue. The developer did not include an explicit question or request -- just pasted the traceback. Adding "what is the reason of this error" (as done in the follow-up session) would have been slightly clearer intent.

> "(No explicit question was included in this session -- the developer pasted only the stack trace without a request like 'fix this' or 'explain this error')"

## Outcome: abandoned

**Evidence:**
> "The user interrupted the previous turn on purpose. If any tools/commands were aborted, they may have partially executed; verify current state before retrying."

The developer aborted after ~3 minutes while Codex was still reading files (7 tool calls completed, no assistant response yet). The sandbox was in read-only mode, which may have contributed to perceived slowness as each command required escalation.

## Struggle Points

The primary struggle was the read-only sandbox mode. The very first tool call failed with a landlock sandbox panic, and every subsequent call required `sandbox_permissions: "require_escalated"`. This approval overhead likely slowed the investigation, leading the developer to abort and restart in a new session (session 2 started ~20 seconds later with the same traceback).

> "Exit code: 101\nWall time: 0 seconds\nOutput:\n\nthread 'main' (17432) panicked at linux-sandbox/src/linux_run_main.rs:30:9:\nerror running landlock: Sandbox(LandlockRestrict)"

## Aha Insight

This session and its immediate successor (started 20 seconds later at 16:47:16) form a pair. The developer abandoned session 1 after 177 seconds of watching tool calls without getting an answer, then restarted with the identical traceback plus the explicit question "what is the reason of this error". The second session succeeded in 506 seconds. The total wall-clock time across both sessions was ~11 minutes for a bug that Codex diagnosed correctly on the first try -- the `np.load` on `.npz` returns an archive, not an array.

**Evidence:**
> "sed -n '1,260p' /home/ubuntu/nikhil/cold-ranker/col/src/model/training.py" (first tool call, failed due to sandbox; then re-issued with escalation -- this pattern repeated for every subsequent command)

## Coach Tip

When using Codex in read-only sandbox mode, be aware that the first tool call will fail and trigger escalation for every subsequent command. If you see this pattern, switch the sandbox mode to `workspace-write` before starting your investigation (as happened automatically in session 2's second turn). This avoids the abort-and-restart cycle that doubled the total debugging time here.
