GPT-6.1 Sol (effort default (no reasoning-effort override) · thinking on) on Fix 8 semantic bugs in a hand-rolled Node.js event emitter (re-entrancy, once/off, error events, leak warning)

OGPT-6.1 Soldefault · thinking on · Codex CLI 0.163.0 (codex exec --json) · cloud · 2026-10-22 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.06
Wall time: 1m
Human step-ins: 0
Outcome: Pass

Compare with other models on this task →

Exact prompt

# Task: fix the plugin host's event emitter `emitter.js` (Node 20, CommonJS, no dependencies) has several bugs reported by plugin authors. Fix them so it behaves as follows: 1. `emit` calls the listeners registered at the moment `emit` starts, in registration order, even if listeners add or remove listeners during the emit (removals/additions affect only later emits). 2. `once(ev, fn)` listeners run at most once even if the event is emitted again from inside the listener (re-entrant emit), and `off(ev, fn)` with the original `fn` removes a pending `once` listener. 3. `emit` returns `true` if there was at least one listener, else `false` (also when the listener list exists but is empty). 4. Emitting `'error'` with no `'error'` listener throws the error argument (or `new Error('Unhandled error')` if none was given); with a listener it is just delivered. 5. A listener that throws stops the emit and the error propagates to the `emit` caller, but `once` listeners that threw are still removed. 6. The leak warning is printed at most once per event name, when the count first exceeds the max; `setMaxListeners(0)` disables it. 7. `off` removes only the most recently added matching registration when the same function was added twice. 8. `on`, `once`, `off`, `setMaxListeners` return `this`; `listenerCount` counts pending once listeners. Keep the export shape. Add your own tests under `test/` if you want (`node --test test/`). No network, no npm installs.

Mirrors real node:events semantics: snapshot iteration, re-entrant once, removing a once wrapper by its original function, throw-on-unhandled 'error', removing the last duplicate registration; each is a separate hidden test. Original benchmark task written for usecaserank.com. Headless, offline run on a reproducible fixture. Cost shown is a list-price API-equivalent estimate (run on a ChatGPT subscription, not billed).

Success criteria: 1. hidden_tests_pass: all 11 hidden node:test tests pass (node 20, 60 s cap). 2. own_tests_pass_or_absent: if the agent added tests under test/, `node --test test/` exits 0.

Setup notes: Use Case Scout batch5 case e10-js-event-emitter (offline fixture). Prepared with batch5/prepare.sh on the shared box; only TASK.md + starting files were copied to the agent machine, hidden key/tests stayed on the box. Prompt = TASK.md verbatim on stdin. Flags: --json -s workspace-write --skip-git-repo-check --ephemeral --ignore-user-config --ignore-rules -C <workdir>. Scored on the box with the scout's scorer: `python score.py WORKDIR KEYDIR`. Single run, no retries. User-level AGENTS.md (846 bytes, sha256 83ec4fe50da8) may have been in context; --ignore-user-config does not document excluding it. Serving model not confirmed: requested via -m; the event log does not echo the serving model id. Price source is secondary (pricing.json verification='secondary', https://www.actuia.com/en/news/ai-api-pricing-in-october-2026-050-to-50-for-output/), not an official OpenAI price page. Score: 11/11. Cost is an ESTIMATE: measured tokens x pricing.json list price (ChatGPT plan, nothing billed); input_tokens include cached reads; output_tokens include reasoning tokens. Tool calls 6 (1 failed, recovered). Single run.

Estimated cost List-price estimate; not actually billed.

Metrics

Estimated cost: $0.06
Wall time: 1m
Human step-ins: 0
Turns: 1

Model usage
Model	Input tok	Output tok	Cost
OGPT-6.1 Solopenai/gpt-6.1-soleffort default (no reasoning-effort override) · thinking on	99,620	2,558	$0.06

Reproduce this run

Use the use case prompt on the use case page.
Same setup: GPT-6.1 Sol (openai/gpt-6.1-sol, effort default (no reasoning-effort override) · thinking on) via Codex CLI 0.163.0 (codex exec --json), cloud.
It counts as a success only if it meets every success criterion: 1. hidden_tests_pass: all 11 hidden node:test tests pass (node 20, 60 s cap). 2. own_tests_pass_or_absent: if the agent added tests under test/, `node --test test/` exits 0.
Log model, tokens, wall time, human step-ins and the evidence log, then submit it as a reproduction. A different model? Submit a head-to-head rerun.

How runs are scored: Methodology.

Was this useful?

⇄ Rerun on another model

Automated checks

Trust 80% comes from these checks (how Trust % works).

Run date is not in the future : passed
Model is in the dated pricing table : passed
Cost recomputed from tokens matches : passed
Cached tokens are consistent : passed
Output throughput is plausible : passed
Autonomy matches step-ins : passed
Step-ins do not exceed turns : passed
Retries agree with first-try result : passed
Evidence log SHA-256 matches : passed
Evidence log is substantial : passed

Evidence log

{"type": "thread.started", "thread_id": "01a16434-8d5f-76c2-8692-349b956ebd8b"}
{"type": "turn.started"}
{"type": "item.completed", "item": {"id": "item_0", "type": "agent_message", "text": "I\u2019ll inspect `emitter.js`, fix the listener behavior, and run focused tests for mutation, re-entrant emits, and errors.\n"}}
{"type": "item.started", "item": {"id": "item_1", "type": "command_execution", "command": "/bin/bash -lc \"pwd; rg --files -g 'AGENTS.md' -g 'emitter.js' -g 'package.json' -g 'test/**'\"", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_1", "type": "command_execution", "command": "/bin/bash -lc \"pwd; rg --files -g 'AGENTS.md' -g 'emitter.js' -g 'package.json' -g 'test/**'\"", "aggregated_output": "/home/bob/usecase-runs/batch/out/gpt-6.1-sol/168_e10/work\nemitter.js\n", "exit_code": 0, "status": "completed"}}
{"type": "item.started", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat emitter.js'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat emitter.js'", "aggregated_output": "'use strict';\n// Minimal event emitter used by our plugin host (no dependency on node:events).\nclass Emitter {\n  constructor() { this._l = {}; this._max = 10; }\n  on(ev, fn) {\n    (this._l[ev] = this._l[ev] || []).push(fn);\n    if (this._l[ev].length > this._max) console.warn(`possible leak: ${this._l[ev].length} ${ev} listeners`);\n    return this;\n  }\n  once(ev, fn) {\n    const w = (...a) => { fn.apply(this, a); this.off(ev, w); };\n    return this.on(ev, w);\n  }\n  off(ev, fn) {\n    const l = this._l[ev];\n    if (!l) return this;\n    const i = l.indexOf(fn);\n    if (i >= 0) l.splice(i, 1);\n    return this;\n  }\n  emit(ev, ...args) {\n    const l = this._l[ev];\n    if (!l) return false;\n    for (let i = 0; i < l.length; i++) l[i].apply(this, args);\n    return true;\n  }\n  listenerCount(ev) { return (this._l[ev] || []).length; }\n  setMaxListeners(n) { this._max = n; return this; }\n}\nmodule.exports = { Emitter };\n", "exit_code": 0, "status": "completed"}}
{"type": "item.started", "item": {"id": "item_3", "type": "file_change", "changes": [{"path": "/home/bob/usecase-runs/batch/out/gpt-6.1-sol/168_e10/work/emitter.js", "kind": "update"}], "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_3", "type": "file_change", "changes": [{"path": "/home/bob/usecase-runs/batch/out/gpt-6.1-sol/168_e10/work/emitter.js", "kind": "update"}], "status": "completed"}}
{"type": "item.started", "item": {"id": "item_4", "type": "command_execution", "command": "/bin/bash -lc 'mkdir -p test'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_4", "type": "command_execution", "command": "/bin/bash -lc 'mkdir -p test'", "aggregated_output": "", "exit_code": 0, "status": "completed"}}
{"type": "item.started", "item": {"id": "item_5", "type": "file_change", "changes": [{"path": "/home/bob/usecase-runs/batch/out/gpt-6.1-sol/168_e10/work/test/emitter.test.js", "kind": "add"}], "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_5", "type": "file_change", "changes": [{"path": "/home/bob/usecase-runs/batch/out/gpt-6.1-sol/168_e10/work/test/emitter.test.js", "kind": "add"}], "status": "completed"}}
{"type": "item.started", "item": {"id": "item_6", "type": "command_execution", "command": "/bin/bash -lc 'node --test test/'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_6", "type": "command_execution", "command": "/bin/bash -lc 'node --test test/'", "aggregated_output": "\u2714 test/emitter.test.js (60.961582ms)\n\u2139 tests 1\n\u2139 suites 0\n\u2139 pass 1\n\u2139 fail 0\n\u2139 cancelled 0\n\u2139 skipped 0\n\u2139 todo 0\n\u2139 duration_ms 77.637585\n", "exit_code": 0, "status": "completed"}}
{"type": "item.started", "item": {"id": "item_7", "type": "command_execution", "command": "/bin/bash -lc 'node --test test/emitter.test.js'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_7", "type": "command_execution", "command": "/bin/bash -lc 'node --test test/emitter.test.js'", "aggregated_output": "\u2714 test/emitter.test.js (59.766466ms)\n\u2139 tests 1\n\u2139 suites 0\n\u2139 pass 1\n\u2139 fail 0\n\u2139 cancelled 0\n\u2139 skipped 0\n\u2139 todo 0\n\u2139 duration_ms 68.251989\n", "exit_code": 0, "status": "completed"}}
{"type": "item.started", "item": {"id": "item_8", "type": "command_execution", "command": "/bin/bash -lc 'git diff --check'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_8", "type": "command_execution", "command": "/bin/bash -lc 'git diff --check'", "aggregated_output": "warning: Not a git repository. Use --no-index to compare two paths outside a working tree\nusage: git diff --no-index [<options>] <path> <path> [<pathspec>...]\n\nDiff output format options\n    -p, --patch           generate patch\n    -s, --no-patch        suppress diff output\n    -u                    generate patch\n    -U, --unified[=<n>]   generate diffs with <n> lines context\n    -W, --[no-]function-context\n                          generate diffs with <n> lines context\n    --raw                 generate the diff in raw format\n    --patch-with-raw      synonym for '-p --raw'\n    --patch-with-stat     synonym for '-p --stat'\n    --numstat             machine friendly --stat\n    --shortstat           output only the last line of --stat\n    -X, --dirstat[=<param1>,<param2>...]\n                          output the distribution of relative amount of changes for each sub-directory\n    --cumulative          synonym for --dirstat=cumulative\n    --dirstat-by-file[=<param1>,<param2>...]\n                          synonym for --dirstat=files,<param1>,<param2>...\n    --check               warn if changes introduce conflict markers or whitespace errors\n    --summary             condensed summary such as creations, renames and mode changes\n    --name-only           show only names of changed files\n    --name-status         show only names and status of changed files\n    --stat[=<width>[,<name-width>[,<count>]]]\n                          generate diffstat\n    --stat-width <width>  generate diffstat with a given width\n    --stat-name-width <width>\n                          generate diffstat with a given name width\n    --stat-graph-width <width>\n                          generate diffstat with a given graph width\n    --stat-count <count>  generate diffstat with limited lines\n    --[no-]compact-summary\n                          generate compact summary in diffstat\n    --binary              output a binary diff that can be applied\n    --[no-]full-index     show full pre- and post-image object names on the \"index\" lines\n    --[no-]color[=<when>] show colored diff\n    --ws-error-highlight <kind>\n                          highlight whitespace errors in the 'context', 'old' or 'new' lines in the diff\n    -z                    do not munge pathnames and use NULs as output field terminators in --raw or --numstat\n    --[no-]abbrev[=<n>]   use <n> digits to display object names\n    --src-prefix <prefix> show the given source prefix instead of \"a/\"\n    --dst-prefix <prefix> show the given destination prefix instead of \"b/\"\n    --line-prefix <prefix>\n                          prepend an additional prefix to every line of output\n    --no-prefix           do not show any source or destination prefix\n    --default-prefix      use default prefixes a/ and b/\n    --inter-hunk-context <n>\n                          show context between diff hunks up to the specified number of lines\n    --output-indicator-new <char>\n                          specify the character to indicate a new line instead of '+'\n    --output-indicator-old <char>\n                          specify the character to indicate an old line instead of '-'\n    --output-indicator-context <char>\n                          specify the character to indicate a context instead of ' '\n\nDiff rename options\n    -B, --break-rewrites[=<n>[/<m>]]\n                          break complete rewrite changes into pairs of delete and create\n    -M, --find-renames[=<n>]\n                          detect renames\n    -D, --irreversible-delete\n                          omit the preimage for deletes\n    -C, --find-copies[=<n>]\n                          detect copies\n    --[no-]find-copies-harder\n                          use unmodified files as source to find copies\n    --no-renames          disable rename detection\n    --[no-]rename-empty   use empty blobs as rename source\n    --[no-]follow         continue listing the history of a file beyond renames\n    -l <n>                prevent rename/copy detection if the number of rename/copy targets exceeds given limit\n\nDiff algorithm options\n    --minimal             produce the smallest possible diff\n    -w, --ignore-all-space\n                          ignore whitespace when comparing lines\n    -b, --ignore-space-change\n                          ignore changes in amount of whitespace\n    --ignore-space-at-eol ignore changes in whitespace at EOL\n    --ignore-cr-at-eol    ignore carrier-return at the end of line\n    --ignore-blank-lines  ignore changes whose lines are all blank\n    -I, --[no-]ignore-matching-lines <regex>\n                          ignore changes whose all lines match <regex>\n    --[no-]indent-heuristic\n                          heuristic to shift diff hunk boundaries for easy reading\n    --patience            generate diff using the \"patience diff\" algorithm\n    --histogram           generate diff using the \"histogram diff\" algorithm\n    --diff-algorithm <algorithm>\n                          choose a diff algorithm\n    --anchored <text>     generate diff using the \"anchored diff\" algorithm\n    --word-diff[=<mode>]  show word diff, using <mode> to delimit changed words\n    --word-diff-regex <regex>\n                          use <regex> to decide what a word is\n    --color-words[=<regex>]\n                          equivalent to --word-diff=color --word-diff-regex=<regex>\n    --[no-]color-moved[=<mode>]\n                          moved lines of code are colored differently\n    --[no-]color-moved-ws <mode>\n                          how white spaces are ignored in --color-moved\n\nOther diff options\n    --[no-]relative[=<prefix>]\n                          when run from subdir, exclude changes outside and show relative paths\n    -a, --[no-]text       treat all files as text\n    -R                    swap two inputs, reverse the diff\n    --[no-]exit-code      exit with 1 if there were differences, 0 otherwise\n    --[no-]quiet          disable all output of the program\n    --[no-]ext-diff       allow an external diff helper to be executed\n    --[no-]textconv       run external text conversion filters when comparing binary files\n    --ignore-submodules[=<when>]\n                          ignore changes to submodules in the diff generation\n    --submodule[=<format>]\n                          specify how differences in submodules are shown\n    --ita-invisible-in-index\n                          hide 'git add -N' entries from the index\n    --ita-visible-in-index\n                          treat 'git add -N' entries as real in the index\n    -S <string>           look for differences that change the number of occurrences of the specified string\n    -G <regex>            look for differences that change the number of occurrences of the specified regex\n    --pickaxe-all         show all changes in the changeset with -S or -G\n    --pickaxe-regex       treat <string> in -S as extended POSIX regular expression\n    -O <file>             control the order in which files appear in the output\n    --rotate-to <path>    show the change in the specified path first\n    --skip-to <path>      skip the output to the specified path\n    --find-object <object-id>\n                          look for differences that change the number of occurrences of the specified object\n    --diff-filter [(A|C|D|M|R|T|U|X|B)...[*]]\n                          select files by diff type\n    --output <file>       output to a specific file\n\n", "exit_code": 129, "status": "failed"}}
{"type": "item.completed", "item": {"id": "item_9", "type": "agent_message", "text": "Fixed `emitter.js` while preserving `{ Emitter }` exports. It now handles listener snapshots, re-entrant `once`, newest-match removal, error propagation, return values, and warning limits.\n\nAdded regression tests in `test/emitter.test.js`. `node --test test/` passes."}}
{"type": "turn.completed", "usage": {"input_tokens": 99620, "cached_input_tokens": 88832, "cache_write_input_tokens": 0, "output_tokens": 2558, "reasoning_output_tokens": 87}}