Which model actually writes better TypeScript, and does it matter enough to change what you reach for? I ran Claude Fable 5 and GPT-4o through the same set of TypeScript generation tasks to find out, and the answer is more useful than a leaderboard number: each model has a different failure mode, and which one bites you depends on what you are building.
I do a fair amount of AI systems architecture work, and picking the right model for codegen inside a pipeline is a decision that compounds. Get it wrong and you are paying for review time on every generated PR. Here is what actually held up under test.
How I set up the test (apples to apples methodology)
I kept the test as fair as I could make it. Both models got the same prompts, the same grading rubric, and no retries. The rubric had three gates:
Does the generated code compile with no edits.
