Do coding agents recommend FormatJS?
FormatJS was chosen in 3% of 500 judged internationalization sessions, ranking eighth. Measured with Claude Code, Codex, Cursor, Grok Build CLI and Muse Code.
FormatJS was chosen in 3% of 500 judged internationalization sessions, ranking eighth. It was also raised as a candidate in 100 further sessions without being chosen.
This page reports what happened when Claude Code, Codex, Cursor, Grok Build CLI and Muse Code had to solve a problem in internationalization inside a realistic codebase. Not what a chat assistant says about FormatJS. What an agent actually installed.
The numbers
| Category | Internationalization |
| Sessions in the category | 500 |
| Sessions where FormatJS was chosen | 15 |
| Install share | 3% |
| Rank in category | 8 of 31 |
| Codebases it won in | 2 |
| Raised as a candidate, not chosen | 100 |
| Chosen when considered | 13% |
| Site | formatjs.github.io |
By agent
With 15 wins spread across 5 agents, the rates below are small numbers and a difference between them is not yet a finding. They are here because the direction is worth knowing, not because the gap is established.
| Agent | Sessions | Chose FormatJS | Share |
|---|---|---|---|
| Claude Code | 113 | 2 | 2% |
| Codex | 150 | 8 | 5% |
| Cursor | 103 | 4 | 4% |
| Grok Build CLI | 26 | 1 | 4% |
| Muse Code | 108 | 0 | 0% |
By who was asking
FormatJS performs similarly across the four kinds of buyer, from 0% to 8%. That is unusual: the category leader changed with the persona in 23 of the 31 categories we measured.
| Who is asking | Sessions | Chose FormatJS | Share |
|---|---|---|---|
| Vibe coder | 102 | 8 | 8% |
| Junior developer | 115 | 0 | 0% |
| Senior engineer | 113 | 0 | 0% |
| Enterprise team | 170 | 7 | 4% |
What FormatJS was up against
The full ranking in internationalization, from the same sessions:
| # | Product | Runs won | Share |
|---|---|---|---|
| 1 | next-intl | 110 | 22% |
| 2 | Django translation framework | 96 | 19% |
| 3 | Symfony Translation | 41 | 8% |
| 4 | Paraglide JS | 41 | 8% |
| 5 | Built in-house (no product adopted) | 41 | 8% |
| 6 | Rails I18n | 38 | 8% |
| 7 | Vue I18n | 27 | 5% |
| 8 | i18next | 27 | 5% |
What this means
This is an integration problem, not a presence problem. Agents raised FormatJS in 100 sessions and chose it in 15, so it reaches the shortlist and then loses. Something at the last step is costing the session, and in our data that is usually a quickstart that does not run when pasted, documentation describing an interface that changed, or a package name that does not match the product name.
That is the cheaper of the two problems to have. The reason is written down in each losing transcript.
Where these numbers come from
The 500 sessions in internationalization are part of a published set of 15,051, run with real coding agents inside realistic codebases and judged blind. The full method is on one page: how we measured this.
Every internationalization run can be replayed on the board.
If you work on FormatJS: the judge recorded a reason for every session where it was raised and passed over. Those reasons are in the transcripts.
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Common questions
Do coding agents recommend FormatJS?
Yes. FormatJS was chosen in 15 of the 500 judged sessions in internationalization, a 3% install share, ranking eighth in its category.
Does Claude Code recommend FormatJS?
In 2 of the 113 sessions in internationalization run with Claude Code, which is 2%.
Do different coding agents treat FormatJS differently?
Not much. Claude Code, Codex, Cursor and Muse Code chose it at similar rates, between 0% and 5% of their runs.
How was this measured?
Real coding agents at pinned versions were run in sandboxes inside 92 realistic codebases and asked to solve real tasks. A simulated project owner approved or questioned each recommendation before any code was written, and a judge from a model family that builds none of the agents read every session blind.
How often is FormatJS considered but not chosen?
It was raised as a candidate in 100 sessions without being chosen, and chosen in 15. That is a 13% conversion from considered to chosen.
Where this comes from
Armature ran 15,051 judged sessions with Claude Code, Codex, Cursor, Grok Build CLI and Muse Code inside 92 realistic codebases, and published every run. The numbers on this page come from that work.