Google has open-sourced the Elephant-Goldfish Model plugin, a set of skills and subagent personas that makes a coding agent write and defend a design document before it writes code. The Google Open Source Blog announced it on 22 October under the Apache 2.0 licence. Google says the plugin started as an internal tool and that “Thousands of Googlers use this plugin every day to ship production Google code.”
This brief covers what the plugin does and how to install it. We have not run it.
Two kinds of agent session
The name is a metaphor. The Elephant is a long-context session that holds the whole design and the project’s history. No code is written there: the agent interviews you, you argue over trade-offs, and the result is a Markdown design document.
The Goldfish are stateless sessions with no memory of that conversation. They read only the draft spec (and, per the README, the live source code), so they do not share the designer’s blind spots. Their job is to find what the spec leaves out.
The blog post states the aim plainly: the agent should “correctly produce the code you wanted the first time after you press Enter.” Co-author Dave Rensin’s shorter version is “Design is the new code.”
The three phases
egm-brainstorm: load the system context and co-design under a “No Code” rule.egm-draft: write the design document section by section, including alternatives considered and a plan that lists the files to change. The README puts these underdocs/designs/<feature>.md.egm-review: the Goldfish protocol, in three steps:- a comprehension check, where a fresh Goldfish must explain the design back; if it cannot, the document is ambiguous
- an antagonistic review, where several Goldfish act as skeptical reviewers hunting for edge cases and hidden dependencies, and their findings go back to the Elephant
- an implementation readiness check, a final go/no-go on whether file paths, data structures and function signatures are all spelled out
The README lists more skills: egm-review-loop for dispatching reviewers in parallel, egm-resolve for triaging findings and applying patches, egm-drift-report, which scans for places where checked-in specs and live code have diverged, and egm-bootstrap for documenting an existing codebase. The reviewer personas in agents/ include Design Critic, Naive Reader, Tech Lead, Codebase Auditor and Zoom Out Architect.
Where it installs
The blog post says the plugin’s “core goal” is Google’s Antigravity, “with other development environments upcoming”. The README already lists install commands for more harnesses:
| Harness | Install route in the README |
|---|---|
| Antigravity | agy plugin install https://github.com/google/elephant-goldfish-model |
| Claude Code | claude plugin marketplace add google/elephant-goldfish-model, then claude plugin install egm@egm (commands use the /egm: prefix) |
| Codex | codex plugin marketplace add google/elephant-goldfish-model, then codex plugin add egm@egm |
| Other agents | ask the agent to install the repo URL; a harness guide covers Claude Cowork and ChatGPT |
The repository was created in September and had about 1,100 stars when we checked on 26 October. Its README ends with a line worth noting before you roll it out to a team: “This is not an officially supported Google product.”
Who should try it
Teams already using agents for multi-file changes, where review is the bottleneck, get the most from this. The Goldfish idea also works without the plugin: hand a fresh session only the spec and ask it to explain the plan back. If it cannot, neither will the agent that has to implement it.
The Campfire
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