Hours unattended: the memory bugs that broke my autonomous coding agent

A developer's autonomous coding agent failed repeatedly over 72 hours due to memory bugs, including silently dropped credentials, truncated logs, incorrect time calculations, and false success detection, leading to the creation of memctl, a free CLI that versions project memory files. The failures highlight that an agent's trustworthiness depends on its memory integrity.

The setup I gave an autonomous coding agent a standing mission, three tools, and a rule: keep producing, never wait for permission. The mission itself was unremarkable. What the first 72 hours exposed wasn't about the mission at all — it was about memory . Everything that went wrong was a memory failure, dressed up as a technical bug. Bug 1: the silently-dropped secret An operator pasted an inbox password into a message. The agent's pre-save caretaker consumed the message, saved nothing, and replied as if it had — twice . The second time, nobody noticed, because the failure mode was no error at all. A silent drop is the worst kind of bug: the happy-path message came back, so the system looked healthy. The fix wasn't a bigger try/catch. It was an evidence file : every credential is persisted or rejected loudly, with a memento left behind, and every critical event lands in a single append-only log that nothing truncates. Now a drop is an event with a timestamp, not a polite void. Bug 2: the truncation cascade The caretaker's event log was a ring buffer that overwrote the oldest lines. The day the receipt of a submitted story mattered, the line had been silently replaced by a heartbeat. Deleting the first warning someone needs to see is functionally the same as deleting the secret: coverage that looks like it's on, isn't. Lesson: if a log is capped, the cap needs escalation , not silence. The critical stream and the heartbeat stream are different products. Bug 3: the clock that posted into the future A backoff queue computed "time since last attempt" using a shell date string that included the timezone offset not applied to the comparison. The queue concluded it had just posted — because in its own arithmetic it was three hours in the future — and went to sleep. A queue that decides it has already done its job is indistinguishable from a broken queue, except that it's also smug. Lesson: unix milliseconds from Date.now , serialized once, in one unit, everywhere. No parsing, no offsets, no local-time folklore. Bug 4: the false success A submission helper piped its output to a file for inspection and forgot that "the output" had — by construction — become empty. An empty string matched the success regex; the system celebrated a post that never reached the public feed. Asserting on an artifact you just deleted for inspection is asserting on your own echo. Lesson: success detection runs on the real response body , and failure strings too fast , expired are first-class outcomes, not lack of success. What all of this is, actually Every one of these is a memory bug : state written once and read back wrong, state overwritten, state never written, state asserted from the wrong source of truth. Which is the argument behind memctl https://raw.githack.com/EltonCherrington/memctl/main/README.md — a free CLI that versions your coding agent's project memory CLAUDE.md / AGENTS.md , so "what was I doing" is a git log away instead of a guess. The agent in this report runs on those same files; the two truest sentences I can write are: - an agent is only as trustworthy as the memory it keeps, and - the failure to warn is a failure mode. Tools already left in the open, all self-contained, no tracking: plainqr https://raw.githack.com/EltonCherrington/plainqr/main/plainqr.html — QR codes, plain · tinyhash https://raw.githack.com/EltonCherrington/tinyhash/main/tinyhash.html — browser hashing, zero servers · onefile-unlock https://raw.githack.com/EltonCherrington/onefile-unlock/main/onefile-unlock.html — a crypto paywall in one HTML file. If one of them saved you five minutes, the shop has a receipt and tip rail: memctl.sh https://raw.githack.com/EltonCherrington/memctl-shop/main/site/index.html .