GPT-6.1 Sol (effort default (no reasoning-effort override) · thinking on) on Fix five behavioural bugs in an LRU cache with per-entry TTL
OGPT-6.1 Soldefault · thinking on · Codex CLI 0.163.0 (codex exec --json) · cloud · 2026-10-22 · by @bobsiopener
- Estimated cost
- $0.04
- Wall time
- 42s
- Human step-ins
- 0
- Outcome
- Pass
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Summary
Exact prompt
# Task: fix the TTL cache `ttlcache.py` is an LRU cache with per-entry TTL. Users report: recently-read keys get evicted, expired keys are still counted in `len()`/`in`, entries that expire exactly at their deadline are still returned, overwriting a key does not refresh its LRU position, and `purge()` crashes. Intended behaviour: - `get` on a live key marks it most-recently-used; when the cache exceeds `maxsize` the **least**-recently-used entry is evicted. - An entry is expired when `clock() >= expires_at` (an entry with ttl=10 set at t=0 is gone at t=10). Expired entries are removed when touched by `get`, and are never visible via `len()` or `in`. - `set` on an existing key replaces the value, resets its TTL and makes it most-recently-used. - `ttl` of 0 or negative means "do not store" (and removes any existing entry for that key). - `purge()` removes all expired entries and returns how many were removed. - `hits`/`misses` count `get` outcomes. Keep the public API (constructor signature, method names). Add your own tests if you like. No network.
Bugs are spread over eviction order, LRU refresh on get/overwrite, an exact expiry boundary, expired-entry visibility, zero TTL and a dict-mutation crash; hidden tests use an injected clock. 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. All 11 hidden unittest cases pass against the agent's ttlcache.py (60 s timeout): LRU eviction of least-recently-used, get/overwrite refresh recency, expiry at clock() >= expires_at, expired entries invisible to len/in, overwrite resets TTL, ttl<=0 not stored, purge() returns count without crashing, hits/misses counted, constructor API kept.
Setup notes: Use Case Scout batch5 case e01-ttl-cache-bugs (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 4 (1 failed, recovered). Single run.
Estimated cost List-price estimate; not actually billed.
Metrics
- Estimated cost
- $0.04
- Wall time
- 42s
- Human step-ins
- 0
- Turns
- 1
| Model | Input tok | Output tok | Cost |
|---|---|---|---|
| OGPT-6.1 Solopenai/gpt-6.1-soleffort default (no reasoning-effort override) · thinking on | 80,688 | 1,668 | $0.04 |
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. All 11 hidden unittest cases pass against the agent's ttlcache.py (60 s timeout): LRU eviction of least-recently-used, get/overwrite refresh recency, expiry at clock() >= expires_at, expired entries invisible to len/in, overwrite resets TTL, ttl<=0 not stored, purge() returns count without crashing, hits/misses counted, constructor API kept.
- 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.
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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
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{"type": "turn.started"}
{"type": "item.completed", "item": {"id": "item_0", "type": "agent_message", "text": "I\u2019ll inspect the cache, fix the reported behavior, and run local tests without using the network.\n"}}
{"type": "item.started", "item": {"id": "item_1", "type": "command_execution", "command": "/bin/bash -lc \"pwd && rg --files -g 'AGENTS.md' -g '*ttl*' -g '*test*' -g 'pyproject.toml' -g 'setup.cfg'\"", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
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{"type": "item.started", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat ttlcache.py && ls -la'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat ttlcache.py && ls -la'", "aggregated_output": "\"\"\"Small LRU cache with per-entry TTL. Used by our API layer.\"\"\"\nimport time\nfrom collections import OrderedDict\n\nclass TTLCache:\n def __init__(self, maxsize=128, ttl=60.0, clock=time.monotonic):\n if maxsize <= 0:\n raise ValueError(\"maxsize must be positive\")\n self.maxsize, self.ttl, self.clock = maxsize, ttl, clock\n self._data = OrderedDict() # key -> (value, expires_at)\n self.hits = self.misses = 0\n\n def set(self, key, value, ttl=None):\n ttl = self.ttl if ttl is None else ttl\n self._data[key] = (value, self.clock() + ttl)\n if len(self._data) > self.maxsize:\n self._data.popitem(last=True)\n\n def get(self, key, default=None):\n item = self._data.get(key)\n if item is None:\n self.misses += 1\n return default\n value, exp = item\n if self.clock() > exp:\n self.misses += 1\n return default\n self.hits += 1\n return value\n\n def __len__(self):\n return len(self._data)\n\n def __contains__(self, key):\n return key in self._data\n\n def purge(self):\n now = self.clock()\n for k, (_, exp) in self._data.items():\n if exp <= now:\n del self._data[k]\ntotal 16\ndrwxr-xr-x 6 bob bob 4096 Oct 22 11:13 .\ndrwxrwxr-x 3 bob bob 4096 Oct 22 11:13 ..\ndr-xr-xr-x 2 bob bob 40 Oct 22 11:13 .agents\ndr-xr-xr-x 2 bob bob 40 Oct 22 11:13 .aws\ndr-xr-xr-x 2 bob bob 40 Oct 22 11:13 .codex\ndr-xr-xr-x 2 bob bob 40 Oct 22 11:13 .git\n-rw-r--r-- 1 bob bob 1065 Oct 22 10:08 TASK.md\n-rw-r--r-- 1 bob bob 1267 Oct 22 10:08 ttlcache.py\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/160_e01/work/ttlcache.py", "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/160_e01/work/ttlcache.py", "kind": "update"}], "status": "completed"}}
{"type": "item.started", "item": {"id": "item_4", "type": "command_execution", "command": "/bin/bash -lc \"cat > test_ttlcache.py <<'EOF'\nimport unittest\n\nfrom ttlcache import TTLCache\n\n\nclass TTLCacheTests(unittest.TestCase):\n def setUp(self):\n self.now = 0\n self.cache = TTLCache(maxsize=2, ttl=10, clock=lambda: self.now)\n\n def test_read_refreshes_lru(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2)\n self.assertEqual(self.cache.get('a'), 1)\n self.cache.set('c', 3)\n self.assertNotIn('b', self.cache)\n self.assertIn('a', self.cache)\n self.assertIn('c', self.cache)\n\n def test_overwrite_refreshes_lru_and_ttl(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2)\n self.now = 5\n self.cache.set('a', 3)\n self.cache.set('c', 4)\n self.assertNotIn('b', self.cache)\n self.now = 10\n self.assertEqual(self.cache.get('a'), 3)\n self.now = 15\n self.assertIsNone(self.cache.get('a'))\n\n def test_expired_get_removes_entry_at_deadline(self):\n self.cache.set('a', 1)\n self.now = 10\n sentinel = object()\n self.assertIs(self.cache.get('a', sentinel), sentinel)\n self.assertNotIn('a', self.cache._data)\n\n def test_len_and_contains_hide_expired_without_counting_gets(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2, ttl=20)\n self.now = 10\n self.assertNotIn('a', self.cache)\n self.assertIn('b', self.cache)\n self.assertEqual(len(self.cache), 1)\n self.now = 20\n self.assertEqual(len(self.cache), 0)\n self.assertEqual((self.cache.hits, self.cache.misses), (0, 0))\n\n def test_nonpositive_ttl_removes_or_does_not_store(self):\n for ttl in (0, -1):\n self.cache.set('a', 1)\n self.cache.set('a', 2, ttl=ttl)\n self.cache.set('b', 3, ttl=ttl)\n self.assertEqual(len(self.cache), 0)\n cache = TTLCache(ttl=0)\n cache.set('a', 1)\n self.assertEqual(len(cache), 0)\n\n def test_purge_removes_all_expired_and_returns_count(self):\n self.cache = TTLCache(maxsize=3, clock=lambda: self.now)\n self.cache.set('a', 1, ttl=5)\n self.cache.set('b', 2, ttl=20)\n self.cache.set('c', 3, ttl=10)\n self.now = 10\n self.assertEqual(self.cache.purge(), 2)\n self.assertEqual(list(self.cache._data), ['b'])\n self.assertEqual(self.cache.purge(), 0)\n\n def test_expired_entries_do_not_displace_live_entries(self):\n self.cache.set('a', 1, ttl=20)\n self.cache.set('b', 2, ttl=5)\n self.now = 5\n self.cache.set('c', 3)\n self.assertIn('a', self.cache)\n self.assertIn('c', self.cache)\n\n def test_hits_and_misses_count_only_get_outcomes(self):\n self.cache.set('a', None)\n self.assertIsNone(self.cache.get('a', 'default'))\n self.assertEqual(self.cache.get('missing', 'default'), 'default')\n self.now = 10\n self.assertIsNone(self.cache.get('a'))\n self.assertEqual((self.cache.hits, self.cache.misses), (1, 2))\n\n\nif __name__ == '__main__':\n unittest.main()\nEOF\npython -m unittest -v\"", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_4", "type": "command_execution", "command": "/bin/bash -lc \"cat > test_ttlcache.py <<'EOF'\nimport unittest\n\nfrom ttlcache import TTLCache\n\n\nclass TTLCacheTests(unittest.TestCase):\n def setUp(self):\n self.now = 0\n self.cache = TTLCache(maxsize=2, ttl=10, clock=lambda: self.now)\n\n def test_read_refreshes_lru(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2)\n self.assertEqual(self.cache.get('a'), 1)\n self.cache.set('c', 3)\n self.assertNotIn('b', self.cache)\n self.assertIn('a', self.cache)\n self.assertIn('c', self.cache)\n\n def test_overwrite_refreshes_lru_and_ttl(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2)\n self.now = 5\n self.cache.set('a', 3)\n self.cache.set('c', 4)\n self.assertNotIn('b', self.cache)\n self.now = 10\n self.assertEqual(self.cache.get('a'), 3)\n self.now = 15\n self.assertIsNone(self.cache.get('a'))\n\n def test_expired_get_removes_entry_at_deadline(self):\n self.cache.set('a', 1)\n self.now = 10\n sentinel = object()\n self.assertIs(self.cache.get('a', sentinel), sentinel)\n self.assertNotIn('a', self.cache._data)\n\n def test_len_and_contains_hide_expired_without_counting_gets(self):\n self.cache.set('a', 1)\n self.cache.set('b', 2, ttl=20)\n self.now = 10\n self.assertNotIn('a', self.cache)\n self.assertIn('b', self.cache)\n self.assertEqual(len(self.cache), 1)\n self.now = 20\n self.assertEqual(len(self.cache), 0)\n self.assertEqual((self.cache.hits, self.cache.misses), (0, 0))\n\n def test_nonpositive_ttl_removes_or_does_not_store(self):\n for ttl in (0, -1):\n self.cache.set('a', 1)\n self.cache.set('a', 2, ttl=ttl)\n self.cache.set('b', 3, ttl=ttl)\n self.assertEqual(len(self.cache), 0)\n cache = TTLCache(ttl=0)\n cache.set('a', 1)\n self.assertEqual(len(cache), 0)\n\n def test_purge_removes_all_expired_and_returns_count(self):\n self.cache = TTLCache(maxsize=3, clock=lambda: self.now)\n self.cache.set('a', 1, ttl=5)\n self.cache.set('b', 2, ttl=20)\n self.cache.set('c', 3, ttl=10)\n self.now = 10\n self.assertEqual(self.cache.purge(), 2)\n self.assertEqual(list(self.cache._data), ['b'])\n self.assertEqual(self.cache.purge(), 0)\n\n def test_expired_entries_do_not_displace_live_entries(self):\n self.cache.set('a', 1, ttl=20)\n self.cache.set('b', 2, ttl=5)\n self.now = 5\n self.cache.set('c', 3)\n self.assertIn('a', self.cache)\n self.assertIn('c', self.cache)\n\n def test_hits_and_misses_count_only_get_outcomes(self):\n self.cache.set('a', None)\n self.assertIsNone(self.cache.get('a', 'default'))\n self.assertEqual(self.cache.get('missing', 'default'), 'default')\n self.now = 10\n self.assertIsNone(self.cache.get('a'))\n self.assertEqual((self.cache.hits, self.cache.misses), (1, 2))\n\n\nif __name__ == '__main__':\n unittest.main()\nEOF\npython -m unittest -v\"", "aggregated_output": "/bin/bash: line 91: python: command not found\n", "exit_code": 127, "status": "failed"}}
{"type": "item.started", "item": {"id": "item_5", "type": "command_execution", "command": "/bin/bash -lc 'python3 -m unittest -v'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_5", "type": "command_execution", "command": "/bin/bash -lc 'python3 -m unittest -v'", "aggregated_output": "test_expired_entries_do_not_displace_live_entries (test_ttlcache.TTLCacheTests.test_expired_entries_do_not_displace_live_entries) ... ok\ntest_expired_get_removes_entry_at_deadline (test_ttlcache.TTLCacheTests.test_expired_get_removes_entry_at_deadline) ... ok\ntest_hits_and_misses_count_only_get_outcomes (test_ttlcache.TTLCacheTests.test_hits_and_misses_count_only_get_outcomes) ... ok\ntest_len_and_contains_hide_expired_without_counting_gets (test_ttlcache.TTLCacheTests.test_len_and_contains_hide_expired_without_counting_gets) ... ok\ntest_nonpositive_ttl_removes_or_does_not_store (test_ttlcache.TTLCacheTests.test_nonpositive_ttl_removes_or_does_not_store) ... ok\ntest_overwrite_refreshes_lru_and_ttl (test_ttlcache.TTLCacheTests.test_overwrite_refreshes_lru_and_ttl) ... ok\ntest_purge_removes_all_expired_and_returns_count (test_ttlcache.TTLCacheTests.test_purge_removes_all_expired_and_returns_count) ... ok\ntest_read_refreshes_lru (test_ttlcache.TTLCacheTests.test_read_refreshes_lru) ... ok\n\n----------------------------------------------------------------------\nRan 8 tests in 0.000s\n\nOK\n", "exit_code": 0, "status": "completed"}}
{"type": "item.completed", "item": {"id": "item_6", "type": "agent_message", "text": "Fixed `ttlcache.py` while preserving the public API:\n\n- Correct LRU updates and eviction.\n- Expiration at the exact deadline, including `len()` and `in`.\n- Overwrites refresh TTL and LRU position.\n- Nonpositive TTL removes existing entries.\n- `purge()` safely removes expired entries and returns the count.\n- Hits/misses count only `get` outcomes.\n\nAdded eight regression tests. All pass with `python3 -m unittest -v`. No network used."}}
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