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GLM-5.3 vs Claude Fable 5
Claude Fable 5 scores higher than GLM-5.3 on all 3 public leaderboards that rate both. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, GLM-5.3 is at 48.1 and Claude Fable 5 at 67.5 (out of 100). On each maker's API, GLM-5.3 costs $1.40 / $4.40 per 1M tokens (input / output) and Claude Fable 5 $10 / $50.
Scores as published by each board; table composed November 12, 2026.
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Leaderboard by leaderboard
| Board | GLM-5.3 | Claude Fable 5 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,622.3 | 1,625.3 | Claude Fable 5 |
| SimpleBench AVG@5 % (private set) | 66.2 | 81.9 | Claude Fable 5 |
| Epoch AI Epoch Capabilities Index (ECI) · many benchmarks on one scale | 157.1 | 164.1 | Claude Fable 5 |
Raw scores are each board's own scale, so compare within a row, not across rows. Full table: the bench index.
For coding
On the ArtificialWatch coding index, GLM-5.3 is at 51.5 (#20 of 47) and Claude Fable 5 at 88.8 (#4). Claude Fable 5 scores higher on both coding boards that rate them.
| Coding board | GLM-5.3 | Claude Fable 5 |
|---|---|---|
| LMArena · Coding | 1,499 | 1,518.6 |
| Vals Vibe Code Bench | 78.1 | 90.4 |
GLM-5.3 at a glance
- Developer
- Zhipu AI
- Status
- Live since August 14, 2026
- API price
- $1.40 input / $4.40 output per 1M tokens · Z.AI, glm-5.3
- Context window
- 1M tokens
Live - same 743B base as 5.2, every gain from post-training · tops CyberGym · open weights on Hugging Face (zai-org/GLM-5.3, 141 safetensors files, public when we read it Sep 25; repo created Aug 25) · Anthropic research (Sep 29): builds end-to-end exploits near Claude Mythos Preview's rate (ExploitBench 50 of 410 vs 56 of 410), and its safeguards fell to simple bypasses 64-100% of the time · Epoch AI report (Oct 29): built one-click file-reading exploits for all six Firefox releases Sep 17-Oct 26 from published-but-unshipped fixes, about $1,000 each, with no refusals at any provider.
Epoch AI: open-weight GLM 5.3 built working Firefox exploits from security fixes that had not shipped yet, for about $1,000 each
2026-10-30 · An open-weight model can now turn browser security fixes that are public but not yet shipped into working exploits on its own, according to a report Epoch AI published October 29.
Anthropic: open-weights GLM-5.3 nearly matches Claude Mythos Preview at building exploits, and its safeguards are easy to strip
2026-09-29 · Anthropic published research on September 29 testing Z.ai's GLM-5.3, an open-weights model anyone can download, on offensive cyber tasks. Its finding: GLM-5.3 can build working end-to-end exploits at close to the rate of Claude Mythos Preview, the model Anthropic released only to vetted defenders.
Claude Fable 5 at a glance
- Developer
- Anthropic
- Status
- Live since July 1, 2026
- API price
- $10 input / $50 output per 1M tokens · Anthropic, claude-fable-5
- Context window
- 1M tokens
Returned Jul 1.
GLM-5.3 vs Claude Fable 5: quick answers
Which is better, GLM-5.3 or Claude Fable 5?
It depends on what you measure. Claude Fable 5 scores higher than GLM-5.3 on all 3 public leaderboards that rate both. Claude Fable 5's widest lead is on SimpleBench. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, GLM-5.3 is at 48.1 and Claude Fable 5 at 67.5 (out of 100).
Which is newer, GLM-5.3 or Claude Fable 5?
GLM-5.3. It went live on August 14, 2026, 44 days after Claude Fable 5 (July 1, 2026).
Which is cheaper, GLM-5.3 or Claude Fable 5?
GLM-5.3 is cheaper on both input and output. On each vendor's own API, GLM-5.3 is $1.40 input / $4.40 output per million tokens and Claude Fable 5 is $10 input / $50 output per million tokens. Prices as published in the models.dev catalog, as of 2026-11-12.
Which has the bigger context window, GLM-5.3 or Claude Fable 5?
Neither. Both take 1M tokens.
How do GLM-5.3 and Claude Fable 5 compare for coding?
On the ArtificialWatch coding index, GLM-5.3 is at 51.5 (#20 of 47) and Claude Fable 5 at 88.8 (#4). Claude Fable 5 scores higher on both coding boards that rate them.
Who makes GLM-5.3 and Claude Fable 5?
GLM-5.3 is from Zhipu AI; Claude Fable 5 is from Anthropic.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed November 12, 2026). Boards measure different things, so raw scores are only comparable within a row.
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