Your coding agent forgets on purpose. A PreCompact hook is where you save it

An open-source MIT-licensed tool called myc provides a local task-and-memory layer for coding agents, hooking into Claude Code's PreCompact event to capture engineering decisions right before the context window is compacted. Built on Bun and TypeScript, myc stores decisions lifted from transcripts as pending candidates that require human confirmation before they surface in search or recall, and enforces p99 latency budgets on its hot paths — measured at 0.608 ms for prime and 8.215 ms for hybrid search on 100,000 nodes. The project also reports ranking gains, with boosts raising MRR@10 from 0.520 to 0.867.

Your coding agent doesn't have amnesia. It has a budget. When the context window fills up, the host compacts it into a summary — and summaries keep the what while losing the why . For engineering decisions, the why is everything. This is a write-up of a tool I came across that is built around exactly that moment — the one where a decision can still be saved: myc , an open-source MIT local task-and-memory layer for coding agents, built on Bun and TypeScript. Its author describes three days of an agent re-doing the same work before writing it; the design follows from that. The cycle, as the README tells it, looked like this. Early in a session you'd decide something: "we're doing X, not Y, because Z." Hours later the context got compacted, the reason drowned, and the agent — honestly, politely, with no memory of ever thinking otherwise — proposed Y again. Notice the failure mode: it's not that the agent forgot. It's that it had no way to know there was something to remember . Any memory layer you query after the fact is useless if nothing was written into it at the moment the context died. So the saving moment is exactly one: right before compaction . Claude Code exposes that moment as the PreCompact hook event. That's where myc lives. myc wire installs the hook. When compaction is about to happen, two things run, in order: password= , api key= , and friends are matched on word boundaries so prose stays prose . The write happens before anything else: if the hook exceeds its timeout, you lose the summary, not the record. bash $ myc absorb-session --reason manual --transcript … --agent claude myc: context is being compacted — here is what must not be lost episode sess-5jh8je4g050m saved 265 B NEXT myc show sess-5jh8je4g050m · myc ready --claim Distillation of what was saved is queued, never done on the write path. Here's the design decision that makes myc deliberately a bit inconvenient: decisions the hook lifts from the transcript "we decided / because" lines are stored as candidates in pending review state. They do not come back from search, recall , prime , or the MCP tools until a human confirms them. prime says so in its footer: N pending review hidden — myc review . bash $ myc review PENDING REVIEW 2 · 1 in this session's prime · 1 from other sessions · session 3f9c21aa $ myc review confirm memory-6k2x… The reasoning: a memory that hallucinates is worse than no memory, because it gets believed. Confirming a candidate turns it into knowledge exactly the way a normal note is born; rejecting it retracts the note, and retracted notes are out of every retrieval path. A memory tool lives in the agent's hot path — it gets called dozens of times per session. If it's slow, the agent starts economizing on it, and economizing on memory is forgetting. So every hot path in myc has a latency budget enforced by tests. Measured on 100,000 nodes 2026-09-11, darwin-arm64, myc 0.3.6, p99 : | operation | p99 | budget | |---|---|---| | prime session context packet | 0.608 ms | 30 ms | | search hybrid | 8.215 ms | 25 ms | | write | 0.327 ms | 5 ms | | cold start | 21.337 ms | 60 ms | Reproduce it yourself: bun install -g @aistastudio/myc bun run scripts/bench-latency.ts from a source checkout Honest footnote: those absolute numbers are calibrated on one machine, and CI doesn't enforce them on other hardware. CI does enforce structural claims query plans, prefiltering and relative ones the healthy path measured against a deliberately degraded one, interleaved so hardware cancels out . Ranking is measured too: boosts take MRR@10 from 0.520 to 0.867, two-hop graph expansion from 0.193 to 0.422 — on corpora that contain a control group which gets worse when the feature works, so you can't fake a win by shaping the corpus. Since 0.3.10 a note can be anchored to a span of code, and the anchor follows the code as it moves — across a refactor, even into another file verified on TypeScript and Python . When the code is no longer where the anchor put it, the knowledge is not deleted: it ranks lower and says why. recall marks the row code moved ×0.64 , code unverified ×0.5 or code gone ×0.2 ; knowledge whose every anchor is lost stays out of prime , and the footer counts it: N with code gone hidden . That is the answer to the question every memory tool eventually faces — "will it start lying to me in a month?" — and it is the part I have not seen elsewhere. myc models fetch ; until then search is lexical and myc run -- bun test puts heavy commands through one machine-wide queue, so parallel agents stop strangling each other. myc import-beads brought over a live project — 796 tasks, 972 dependencies, 265 notes — in 889 ms; re-running it syncs instead of duplicating. The first release silently dropped the export's comments; found the next day on a real project, fixed in 0.2.0, and described by the author in the README. bun:sqlite — SQLite and sqlite-vec ship inside Bun with no native Node bindings. It will not start on plain Node.js or Deno. That's the deal: one runtime, one binary, zero native build steps. bun install -g @aistastudio/myc 3.42 MB, pulls nothing myc init && myc wire hooks + MCP for Claude Code, Codex, opencode, Kimi The project is about a week old and ships a release close to every day, which is another way of saying: now is the cheapest time to tell the author what's wrong. If you run agents daily, the question worth answering in the issues is whether decisions survive your sessions today — and if not, whether a compaction hook feels like the right place to save them. Repo: https://github.com/aistastudio/myc https://github.com/aistastudio/myc Site every number printed next to the command that reproduces it : https://aistastudio.github.io/myc/ https://aistastudio.github.io/myc/