Pi Session Analyzer

Pi session JSONL is the source of truth for agent execution details; tasks.jsonl is the source of truth for final task state; attempts/<task_id>.json is the source of truth for the retry lifecycle. Route metrics through ego_bench/session_parser.py; use the skill scripts only for filtering, locating evidence, and presentation.

Core constraints

1. For a specific run, read the raw JSON/JSONL first. Do not infer from memory or HTML prose.
2. Read duration, think/LLM/env, turn, token, cost, and tool distributions only from SessionStats. Do not duplicate the metric convention inside the skill.
3. Treat the actual toolResult as the source of truth for tool calls and error details. Assistant narration can explain intent only.
4. Tool errors include not only toolResult.isError=true, but also code-0 shell/ego-browser wrapped failures recognized by the project parser. Assistant stopReason=error events, such as provider_transport_failure, are separate session-level abnormal stops.
5. Cite evidence with the task_id and the session line number or turn number.
6. Inspect the attempt artifact when attempt_count>1. When an old run lacks that artifact, explicitly state that "historical attempts have no reliable linkage"; do not infer a definite association from timing or prompts alone. attempt_count==1 does not mean the task ran only once: force-rerun overwrites the result and attempt file in place, leaving its only trace in the reruns array in run_metadata.json. Inspect it before discussing success rates.
7. Stream raw evidence line by line through the session. Do not load an entire large session with json.load.
8. Do not modify original run artifacts unless the user explicitly requests it.

Runtime environment

.claude/skills/pi-session-analyzer is the source directory; the user-level .codex skill should symlink to it. Resolve the harness from each script's real path. Do not hard-code a checkout path or use a silent parser fallback. Use the project environment consistently:

ROOT=$(git rev-parse --show-toplevel)
PY="$ROOT/.venv/bin/python"
SCRIPTS="$ROOT/.claude/skills/pi-session-analyzer/scripts"

If the project environment lacks a dependency, fail loudly and identify the correct interpreter. Do not install dependencies during the analysis.

Data model

runs/<run_id>/tasks.jsonl

Each line is one final task instance. Key fields:

Field	Meaning
task_id	Composite task ID, such as rwb-x__iter2
base_task_id / iteration_index	Base ID and iteration number
session_file / session_id	Session locator for the final attempt
attempt_count	Total attempts in this task lifecycle
started_at / ended_at	Outer task timestamps for the final attempt
error / verdict / score	Runtime and judge results
failure_reason / judge_reasoning	Judge explanation

runs/<run_id>/attempts/<task_id>.json

A new run updates this atomically after each completed provider lifecycle:

{
  "schema_version": 1,
  "task_id": "rwb-x__iter2",
  "attempts": [
    {
      "attempt_index": 1,
      "session_file": "/abs/path/first.jsonl",
      "provider_error": null,
      "failure_reason": "provider_transport_failure: WebSocket error",
      "step_limit_hit": false
    }
  ]
}

This stores only control-flow provenance, without duplicating derived metrics such as token, cost, or duration. Force-rerun overwrites the task's old attempt file. It is normal for legacy runs to lack this directory.

Other run-level artifacts

Path	Purpose
judges/<task_id>_judge.json	Per-rubric decisions (metadata.rubric_scores/rubric_results), the judge session for each rubric, judge cost/turns/image count. For scoring disputes, inspect this before relying only on judge_reasoning in tasks.jsonl
browser_state/<task_id>.json	Task spaces left open by the task at teardown
close_done/<task_id>.json	Whether harness teardown actually closed successfully (ok/return_code/stdout_tail)
screenshots/ + screenshot_trees_dir	Frames and structure trees seen by the judge. Frames are webp; frame and tree numbers are not synchronized in manifest.jsonl, so use the field mapping
pi_stderr/<task_id>.log	Provider process stderr for startup/transport errors absent from the session

judges/_job.json is the scoring job's progress file, not an artifact for a specific task. Odysseys task_id values are hashes, so judge filenames may not be readable. Index them by the task_id field inside the file.

Pi session JSONL

• Top-level entry.timestamp: timing coordinate for the report and parser.
• message.timestamp: provider-internal message time; display it as-is, but do not use it for timing attribution.
• assistant.content[].toolCall: call ID, name, and arguments.
• toolResult.toolCallId: pairs with the call; isError=true indicates a tool failure.
• assistant.usage: per-turn input/output/cache/reasoning/cost.
• customType=ego-bench-think: thinking wall time for that assistant turn.
• assistant.stopReason=error: session-level abnormal stop, not a tool failure.

ego-browser runtime semantics (how to interpret errors)

The ego-lite API and failure semantics are evolving. Confirm these rules before interpreting tool_failures:

• Wait failures are silent: waitForURL / waitForSelector / locator.waitFor / waitForFunction return a false value on timeout instead of throwing (waitForRequest/waitForResponse still throw). Therefore, a lower tool-error count across versions does not necessarily mean greater stability; a failure may simply have changed from an exception to a false value. Check whether subsequent actions became ineffective.
• Bare locators use strict matching: matching multiple elements throws matched N elements, which is the opposite problem from matched 0 elements (selector too broad vs no match). These belong to the locator_ambiguous and locator_miss buckets, respectively.
• Agent assertions: failures triggered by throw new Error('...') in a heredoc belong to script_assertion. They show that the agent's self-check worked, not that the tool broke. Report them separately when calculating a tool defect rate.
• User takeover is a hard stop: user has taken control / user is controlling belong to user_control_stop. By contract, the agent should stop and ask rather than retry.
• Attachments/local sites: ego_bench/task_resources.py stages task resources in task-files/ under the agent working directory. Errors caused by the agent using the wrong path belong to task_resource_missing (observed in both old and new runs).

Error buckets are defined in ERR_BUCKETS in scripts/_pi_session_lib.py; order is priority (first match wins). When adding a bucket, ensure an earlier broad pattern does not consume it. A high share in the fallback nonzero_exit/other buckets signals that the taxonomy needs updating.

Standard analysis path

A. Inspect one run first

$PY "$SCRIPTS/analyze_run.py" runs/<run_id> --top 5
$PY "$SCRIPTS/analyze_run.py" runs/<run_id> --task-id <task_id> --json

The entry point:

1. Reads final task state with latest_by_task_id.
2. Recalculates full-sample metrics with session_parser.
3. Prioritizes runtime errors, false verdicts, retried tasks, tool failures, and slow tasks.
4. Attaches attempt data, error line numbers, and similar retry segments to selected entries.
5. Emits an explicit warning when a legacy run lacks attempt artifacts.

B. Summarize one session and inspect errors

$PY "$SCRIPTS/session_summary.py" "$SESSION" | jq
$PY "$SCRIPTS/session_quickscan.py" "$SESSION"
$PY "$SCRIPTS/extract_errors.py" "$SESSION" --table

session_summary and quickscan must show:

• duration_s / think_time_s / llm_time_s / env_time_s;
• stop_reason_error / parse_error / warnings;
• turns, tools, tool failures, tokens, reasoning, and cost;
• error buckets and whether final output exists.

C. Inspect tool calls and retries

$PY "$SCRIPTS/extract_tool_calls.py" "$SESSION" --table
$PY "$SCRIPTS/extract_tool_calls.py" "$SESSION" --errors-only --full
$PY "$SCRIPTS/extract_tool_calls.py" "$SESSION" --missing-only
$PY "$SCRIPTS/retry_clusters.py" "$SESSION" --threshold 0.82

For each call, output the call/result line numbers and a 12-character argument fingerprint. A call without a toolResult has missing status and must not be treated as successful. A retry cluster is only a statistical clue about consecutive similar calls; inspect every actual result when reporting. Do not automatically equate similarity with the same root cause.

D. Calculate per-turn timing correctly

$PY "$SCRIPTS/turn_timings.py" "$SESSION" --top 5

Use the same field conventions as the single-run report:

• think_s: ego-bench-think; None when not measurable in an old session.
• llm_s: interval between top-level assistant entries minus think time.
• env_s: top-level entry interval for toolResults in that turn.
• turn_s: think + LLM + env (when think is not measurable, it is already included in LLM).

Do not restore the old message.timestamp → tool_s algorithm; it attributes model-generation errors to tool waiting.

E. Inspect input, process, and final answer

$PY "$SCRIPTS/extract_io.py" "$SESSION"
$PY "$SCRIPTS/extract_outputs.py" "$SESSION" --mode final
$PY "$SCRIPTS/extract_outputs.py" "$SESSION" --mode thinking --turn 7

Include the final answer's source line and turn so it can be verified against the raw JSONL.

F. Compare two runs

$PY "$SCRIPTS/runs_pair_diff.py" runs/<baseline> runs/<test> --top 10

Pair the intersection by (base_task_id, iteration_index). Read metrics directly from the project parser; exit if the parser cannot be imported rather than silently using a reduced fallback. After full-sample statistics, investigate the 2–3 tasks with the largest differences. Do not generalize from individual cases.

Script responsibilities

Script	Responsibility
analyze_run.py	Run-level filtering and attempt/error/retry evidence summary
session_summary.py	One-line JSON projection of SessionStats
session_quickscan.py	Human-readable overview and error samples
extract_errors.py	Tool errors and assistant stop errors with line numbers
extract_tool_calls.py	ToolCall/result pairing, status, and argument fingerprints
retry_clusters.py	Clustering of consecutive similar calls
turn_timings.py	Per-turn think/LLM/env timing consistent with the report
extract_outputs.py	Thinking/text/final output with turn/line
extract_io.py	First user prompt and final assistant text
runs_pair_diff.py	Paired differences between two runs

Reporting rules

1. Use the first three sentences to answer what happened, what the root cause was, and how broad the impact was.
2. Separate full-sample conclusions from individual evidence; label individual cases as n=1.
3. Use tables for data. Error samples must include the task ID and line or turn.
4. Distinguish tool failure, assistant stop error, runtime error, and judge failure.
5. Keep duration/think/LLM/env consistent with the single-run HTML parser convention.
6. For legacy attempts, report only that reliable linkage is unavailable; label time-window or prompt matching as inference.

Forensic trap: skill text contaminates string searches

The agent reads the entire SKILL.md into every session (persisted as a toolResult), and that text describes every runtime error marker. Grepping those markers directly produces a perfectly regular set of false positives. In two recent runs, [ego-browser:skill-stale], [ego-browser:notice], user is controlling, and w: 0 each appeared 40 times—exactly once per session—all from the skill text, with zero real runtime errors.

Search runtime signals through is_error results from iter_tool_pairs, or explicitly exclude the turn that loaded the skill. When every session has exactly the same hit count, first suspect that the search matched documentation rather than failures.

Anti-patterns

• ❌ Do not duplicate the token/cost/duration parser inside the skill.
• ❌ Do not use message.timestamp to calculate tool duration.
• ❌ Do not inspect only toolResult.isError and miss code-0 wrapped failures or stopReason=error.
• ❌ Do not mark a call without a toolResult as successful.
• ❌ Do not silently skip parser import or schema errors.
• ❌ Do not describe the agent execution path from tasks.jsonl alone.
• ❌ Do not modify a historical run to "fill in" nonexistent attempt linkage.
• ❌ Do not grep runtime error markers without excluding the turn that loaded the skill text.
• ❌ Do not compare absolute tool_failures across ego-lite versions without explaining that wait failures changed to silent returns.
• ❌ Do not treat attempt_count==1 as "this task ran only once" (force-rerun leaves no trace there).