Opus 5.5 Ported Microsoft's TypeScript Compiler to Rust for $24K After GPT-6 Burned $400K
Ping.gg founder Theo Browne published a working Rust port of the TypeScript compiler this week. The project, ts-rust (npm: tsc-rs), is a full port of Microsoft’s native TypeScript 7 compiler — written in Go — to Rust. Browne described his approach bluntly: “I’ve never read a line of this code.”
He didn’t write it either. Every line came from an LLM.
The $400K Warmup
The experiment began with OpenAI models. Browne ran GPT-5.6 Sol and GPT-6 Astra through multi-month /goal loops that produced over 1.3 million lines of Rust. Neither model cleared 84% compatibility with TypeScript’s own test suite. Total API spend across those attempts exceeded $400,000.
When Claude Opus 5.5 became available, Browne switched. Opus 5.5 discarded all prior Rust code and started from scratch. It reached a working v0 in under 10 hours. Two weeks later, the port passed all 181,711 tests from the upstream Go implementation, matched output on 120 open-source repositories, and produced identical type-checker diagnostics on the T3 Code suite.
Total Opus 5.5 API cost: approximately $24,047.
Benchmark Numbers
On a T3 Code full type-check (five projects, summed), tsc-rs comes in at 7.25 seconds. The Go-based tsc 7 takes 16.10 seconds — making tsc-rs 2.22x faster. The legacy JavaScript tsc 6 takes 62.63 seconds. Bun’s built-in bun check is the fastest at 4.07s, but it lacks the Effect language-service diagnostics that tsc-rs ships with natively.
| Checker | Time | vs tsc 7 |
|---|---|---|
| bun check | 4.07s | 3.95x faster |
| tsc-rs | 7.25s | 2.22x faster |
| tsc 7 (Go) | 16.10s | baseline |
| tsc 6 (JS) | 62.63s | 3.89x slower |
Geometric mean across 60 open-source projects: tsc-rs takes about half of Go’s wall time. The published binaries are unoptimized (no PGO or BOLT), so the real gap is wider.
What Was Actually Ported
The port tracks microsoft/TypeScript at commit 673a5f17d713 (September 29, 2026, TypeScript 7.1.0-dev). It includes the compiler, type checker, and language server. VS Code integration works via standard LSP. The npm package is a drop-in replacement: npx tsc-rs -p tsconfig.json runs the same options as tsc.
tsc-rs ships Effect language diagnostics (codes 377xxx) built directly into the checker rather than as a plugin. An Effect project needs no second compiler pass.
Supported platforms: Linux x64 and macOS arm64. Windows and Linux arm64 are not yet available.
What This Tells You About the Models
The capability gap here is blunt. GPT-5.6 Sol and GPT-6 Astra wrote 1.3 million lines of Rust and failed. Opus 5.5 wrote a correct implementation from scratch in a fraction of the time and cost.
Browne’s framing: he let the Claude accounts run until they burned through 925% to 983% of his $200 weekly plan limits per week. The model kept going without human intervention beyond the initial prompt. The architecture decision — start over instead of patching the existing Rust codebase — was made by the model.
The project is available at github.com/pingdotgg/ts-rust. Compatibility is described as 100% on all tested real-world projects. Known issues and gaps are documented in the repository.