GLM-5.3 scores 88.2 on Terminal-Bench v2.1. Beam scores 80.1. On a leaderboard that settles it. On an invoice it does not, which is the whole reason this comparison is worth eight points of your attention.
Head to head
| | Reflection Beam | GLM-5.3 |
|---|
| Terminal-Bench v2.1 | 80.1 | 88.2 |
| SWE-Bench Verified | 80.9 | Not directly comparable |
| Active parameters | 23B of 501B | Larger active set |
| Licence | Apache 2.0 | Open weights |
The efficiency argument, stated carefully
Reflection's comparison is against GLM-5.2, not 5.3: comparable reasoning quality at three to four times less inference compute, roughly 25,000 tokens per attempt against 80,000. Beam's own score sits one point below GLM-5.2 and eight below 5.3. So the honest framing is that Beam trades a small quality gap against 5.2 for a large cost gap, and a larger quality gap against 5.3 for a cost gap nobody has measured.
The figures are Reflection's, computed as 2 x active parameters x mean generated tokens, excluding prefill, attention and serving overhead. Nobody has independently reproduced them.
Decision framework
- Hard tasks, low volume → GLM-5.3. Eight points on agent benchmarks is real, and at low volume you will not feel the tokens.
- High-volume agent loops → Beam. Retries multiply token spend, and a cheaper attempt changes the shape of what you can afford to run.
- Strict licence review → Beam. Apache 2.0 is the cleanest answer to a legal team.
- Undecided → measure your tokens per completed task for a week first. Without that number this comparison has no answer.
FAQ
Which is better, Beam or GLM-5.3?
GLM-5.3 on measured capability — 88.2 against 80.1 on Terminal-Bench v2.1. Beam's case is cost per attempt, which depends on your workload rather than on the model.
Are Beam's efficiency numbers verified?
No. They are Reflection's own estimates using a formula that excludes prefill, attention and serving overhead. Treat them as a direction, not a measurement.
Is either one usable commercially?
Beam is Apache 2.0, which permits commercial use, modification and redistribution with attribution. Check GLM's current licence terms directly before deploying.
Related: Reflection opens Beam