OpenCode Memory Internals

I started this investigation after finding a local OpenCode project that appeared to remember guidance across sessions. The guidance lived in Markdown files outside the repository, yet every new session followed it. The operational question was simple: had OpenCode decided to preserve those facts, or had someone explicitly written them? The session record answered it. An agent had created the files through an ordinary file tool after an explicit user request. A project-local instructions configuration then loaded them on every provider turn. What looked like autonomous memory was user-triggered file authoring plus deterministic prompt injection. That result sent me looking for the actual memory subsystem. There is no general runtime-managed service that decides what to save, updates facts when they change, and semantically retrieves useful knowledge in later sessions. What users experience as "memory" is produced by three different mechanisms with different owners and failure modes: instruction files are loaded into the system prompt, durable session events and projected messages are persisted in SQLite, and old model-visible context is replaced by a generated compaction checkpoint when the request grows too large. These mechanisms work together, but they do not form an autonomous long-term memory manager. That distinction matters. If a coding agent remembers a project rule because AGENTS.md is injected on every turn, that is not learned memory. If it can reopen an old transcript from SQLite, that does not mean a new session can retrieve facts from it. If a long session survives by summarizing its history, that does not mean the runtime selected the most important information. This article follows the current OpenCode source tree, which contains both the desktop-compatible session path under packages/opencode and the newer V2 runtime under packages/core . Where the two paths differ, I call out the difference rather than treating them as one implementation. Primary c