Prism — Anonymous Code Release

Persistent file-level memory for coding agents.

This repository is a modified snapshot of the OpenCode agent framework that implements the file-memory mechanism described in the accompanying paper.

The original OpenCode README is preserved at UPSTREAM_README.md and its license at UPSTREAM_LICENSE.

What this adds to OpenCode

Three pieces composed on top of the OpenCode source tree:

1. Persistent file-memory. A per-file (path, content-hash) → (summary, facets[]) cache, persisted on disk under <workdir>/.opencode/file-history/ (one JSONL file per source path, with one entry per content hash). Edits invalidate entries automatically through the content hash; no TTL or manual eviction is required.
2. Facet accumulation. After each reasoning chunk the agent emits between tool calls, the system distills at most one new identifier-grounded fact per recently-read file and appends it to the memory entry, with a small bounded cap per file (see history.ts).
3. read_summary tool. The agent gains one new tool that returns the cached summary-plus-facet briefing for a path, letting it skip a full re-read when accumulated knowledge already suffices.

Source changes

All modifications live inside packages/opencode/. Eleven files are added or modified relative to the upstream OpenCode dev branch.

File	Status	Role
packages/opencode/src/file/history.ts	new	Core file-memory: on-disk (path, hash) → (summary, facets[]) cache, the LLM-backed summarizer / distiller / aggregator, and the in-memory state object that gates everything on OPENCODE_FILE_HISTORY=1.
packages/opencode/src/tool/read_summary.ts	new	The read_summary(path) tool: returns the cached briefing for path.
packages/opencode/src/tool/read_summary.txt	new	Tool description shown to the agent. The only new agent-visible text.
packages/opencode/src/tool/read.ts	modified	Hooks recordRead(path, hash, content) after every successful read, scheduling background summarization and enqueueing the file for facet distillation.
packages/opencode/src/tool/read.txt	modified	One-line note pointing the agent at the cached briefing.
packages/opencode/src/tool/edit.ts	modified	(a) recordObservation hook that distills a facet from the reasoning surrounding each edit; (b) an indent-correction fix for the fallback string replacer, with regression coverage in test/tool/edit.test.ts.
packages/opencode/src/tool/registry.ts	modified	Conditionally register read_summary only when OPENCODE_FILE_HISTORY=1.
packages/opencode/src/tool/task.ts	modified	Propagate file-memory context across sub-agent task boundaries.
packages/opencode/src/session/processor.ts	modified	Wire recordRead / recordObservation into the session lifecycle.
packages/opencode/src/effect/app-runtime.ts	modified	Register the file-memory Effect layer in the application runtime.
packages/opencode/test/tool/edit.test.ts	new	Regression tests for the indent fix in edit.ts.

Building

OpenCode is a TypeScript monorepo built with Bun ≥ 1.3.11. From the repo root:

bun install
cd packages/opencode
bun run build -- --skip-embed-web-ui

The --skip-embed-web-ui flag skips the optional web frontend build — only the CLI binary is needed for evaluation. The compiled CLI binary lands at packages/opencode/dist/opencode-linux-x64/bin/opencode.

Activation

The new behavior is gated behind two environment variables, both off by default:

Variable	Effect
OPENCODE_FILE_HISTORY=1	Enables the file-memory cache and registers the read_summary tool. When unset, the binary behaves exactly like upstream OpenCode.
OPENCODE_FH_FACETS=1	Enables facet distillation. With OPENCODE_FILE_HISTORY=1 set and this one unset, the system stores only the base summary.

The auxiliary memory LLM (used internally for summarization, facet distillation, and aggregation) is configured by:

Variable	Effect
OPENCODE_FH_BASE_URL	OpenAI-compatible base URL for the memory LLM.
OPENCODE_FH_MODEL	Model id for the memory LLM.
OPENCODE_FH_API_KEY	API key (use dummy if the proxy does not check).

Two optional flags toggle alternative modes for comparison studies:

Variable	Effect
OPENCODE_FH_SUMMARY_LONG=1	Replace the facet pipeline with one larger unstructured summary per file.
OPENCODE_REPO_MAP=1	Inject an Aider-style static repository map into the system prompt.
OPENCODE_REPO_MAP_MAX_TOKENS	Token budget for the repo-map injection (default 4096).

Verifying activation

With OPENCODE_FILE_HISTORY=1 set, the read_summary tool will be registered alongside the standard tools. After the agent reads any file, a JSONL entry is appended under <workdir>/.opencode/file-history/, one file per source path with one record per content hash, each containing { hash, summary, facets[] }.

Tests

The indent-fix regression suite for the edit tool:

cd packages/opencode
bun test test/tool/edit.test.ts

License

OpenCode is distributed under the MIT License (see UPSTREAM_LICENSE). The modifications above are released under the MIT License (see LICENSE).