Overview
EGM is a coding agent plugin Google open-sourced on 22 October 2026, short for Elephant-Goldfish Model and licensed Apache 2.0. It trains no model and ships no weights. What it provides is a workflow: make the agent write a specification before it writes code, then send a batch of subagents with no conversation history to attack that spec.
The name comes from its two roles. The elephant is a long session holding project context, interviewing requirements, arguing trade-offs and drafting the design section by section, writing no code along the way. The goldfish is a fresh session spawned for each review that reads only the draft and the files it references, carrying none of the main session's history or assumptions. Because the goldfish does not know what the earlier conversation quietly settled, it asks the questions the main session forgot to ask.
Three commands carry the loop. egm-brainstorm runs six parallel lenses covering YAGNI, token cost, UX, migration, observability and tech debt, producing a concepts brief. egm-draft turns the brief into a design document under docs/designs. egm-review launches the goldfish review. A fourth command, egm-drift-report, compares code against the spec over time. The plugin ships 7 skills, 9 reviewer personas and 6 brainstorm lenses, and runs on hosts that can spawn subagents, including Antigravity, Claude Code 2.1.271 and later, Claude Cowork, Codex and ChatGPT.
Key Features
- The elephant drafts the spec: The main session holds project context and, under a no-code rule, interviews requirements, argues trade-offs and produces a design document under docs/designs naming the files to change.
- Stateless goldfish review: Each review spawns fresh subagents that read only the draft and the files it references, keeping the designer's blind spots out of the review.
- Five-stage review: Initial zoom out, a comprehension test, critic review, a second architecture check after fixes, and an implementation readiness pass, each allowing at most one re-audit with findings ranked as blocker, major or nit.
- Six brainstorm lenses: The brainstorm stage runs six lenses in parallel on YAGNI, token cost, UX, migration, observability and tech debt, so a plan is not thought through in one direction only.
- Comprehension test: A goldfish paraphrases the design in its own words; a wrong paraphrase means the document is ambiguous, which surfaces wording problems faster than rereading it.
- Drift reports: egm-drift-report compares code against the spec to find places where the implementation has moved away from the design, and the docs recommend running it weekly.
- Runs across hosts: Supports Antigravity, Claude Code, Claude Cowork, Codex and ChatGPT among hosts that can spawn subagents; in Claude Code reviewers get only read, grep and glob tools for a cleaner context.
Use Cases
- Making a coding agent produce a design document before touching code.
- Catching wrong assumptions before a pull request exists, so rework happens at the design stage.
- Getting an independent, dispassionate review once a spec is written.
- Keeping a long-running project from drifting away from its original design.
Pros
- Reviewers have no context, so they ask questions the main session would not think to ask.
- The five-stage flow has defined outputs and at most one re-audit per stage, making the process traceable.
- The plugin is free; it spends model quota the host agent already has.
- Works with several hosts, so no IDE or CLI switch is required.
- Thousands of Google engineers use it daily, so it is not a lab artifact.
Pricing
The plugin is free and open source under Apache 2.0. It ships no model weights; drafting and reviewing spend the host agent's model quota, billed at that host's subscription or API rates.
Summary
EGM suits teams already using Claude Code, Codex or another subagent-capable coding agent who have paid the price of rework. Its value lies not in generating code but in surfacing wrong assumptions while they are still in a Markdown file. The cost is token usage, since a full review runs many subagent rounds, so it fits medium and large changes best.
Version History
- Google open-sources the EGM plugin for spec-first coding agents (2026-10-22): Google open-sourced the Elephant-Goldfish Model plugin under Apache 2.0. The plugin makes a coding agent write a specification before code, then has Goldfish subagents with no conversation history review that spec across five stages, shipping 7 skills, 9 reviewer personas and 6 brainstorm lenses. Google says thousands of its engineers use it.