GLM-5.3 vs Claude Fable 5.1
GLM-5.3 and Claude Fable 5.1 are within three points on the Models at Work leaderboard, which we treat as a tie (78 vs 76). GLM-5.3 is about 9.3× cheaper per blended million tokens ($2.15 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Fable 5.1 leads 49 to 32.
| GLM-5.3 · Z.ai | Claude Fable 5.1 · Anthropic | |
|---|---|---|
| Leaderboard rank | #6 | #7 |
| Score (0–100) | 78 | 76 |
| Tier | Open weights | Frontier |
| Price per 1M tokens | $1.40 in · $4.40 out | $10 in · $50 out |
| Context window | 1M | 1M |
| Open weights | Yes | No |
| Artificial Analysis Intelligence Index | 32 | 49 |
| Arena Text score | 1478 (rank 27) | — |
| Scale SWE-Bench Pro V2 (mini-swe-agent) | 84.30% | — |
| Scale MCP Atlas | 84.20 | — |
| Arena WebDev score | 1622 (rank 22) | — |
| Arena text score | — | 1501 |
| Humanity's Last Exam, Diamond (Scale) | — | 51.3 |
| Best for | Agentic coding in Claude Code / Pi-style harnesses, Security research and code auditing, Self-hosted frontier-ish reasoning | Long-horizon agents, Problems Opus fails on, Demanding reasoning |
Compare source-qualified API rates and a monthly workload example before estimating your bill.
Choose GLM-5.3 if…
- you need agentic coding in claude code / pi-style harnesses
- you need security research and code auditing
- you need self-hosted frontier-ish reasoning
The open model people actually ship coding agents on. Same 744B base as GLM-5.2 with heavy agentic post-training; drops into Claude Code harnesses and holds its own on SWE-Bench Pro V2 and MCP Atlas at a third of frontier prices.
Caveats: License is muddled: AA lists a custom 'GLM-5.3 License' with commercial restrictions while Arena lists MIT. Read it before you self-host. Permissive on offensive-security tasks; that is a feature for red teams and a governance problem for everyone else. Open weights shipped ~2 weeks after the API; HN worried the public weights were safety-tuned differently.
Choose Claude Fable 5.1 if…
- you need long-horizon agents
- you need problems opus fails on
- you need demanding reasoning
The specialist: Anthropic's own docs say to reach for it when Opus 5.5 at high effort still falls short, and the price says the same.
Caveats: Ten dollars per million input is the highest in this table alongside Astra.
What practitioners say
GLM-5.3: One of the biggest HN launches of the year (1,171 points, 584 comments). Practitioners report it 'fits Claude Code as its own, zero issues', that '$5 in tokens' of Claude work costs '$0.50' on GLM via Pi, and that it 'routinely finds bugs missed by Fable and Sol' in audits. The cyber angle was the controversy: users bragged about adapting kernel exploits that 'Claude and Opus outright refused', and others flagged the risk of nerfed public weights.
Questions people ask
Which is better, GLM-5.3 or Claude Fable 5.1?
GLM-5.3 and Claude Fable 5.1 are within three points on the Models at Work leaderboard, which we treat as a tie (78 vs 76). GLM-5.3 is about 9.3× cheaper per blended million tokens ($2.15 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Fable 5.1 leads 49 to 32.
When should I choose GLM-5.3 over Claude Fable 5.1?
Choose GLM-5.3 for agentic coding in claude code / pi-style harnesses, security research and code auditing, self-hosted frontier-ish reasoning. The open model people actually ship coding agents on. Same 744B base as GLM-5.2 with heavy agentic post-training; drops into Claude Code harnesses and holds its own on SWE-Bench Pro V2 and MCP Atlas at a third of frontier prices.
When should I choose Claude Fable 5.1 over GLM-5.3?
Choose Claude Fable 5.1 for long-horizon agents, problems opus fails on, demanding reasoning. The specialist: Anthropic's own docs say to reach for it when Opus 5.5 at high effort still falls short, and the price says the same.
Which is cheaper, GLM-5.3 or Claude Fable 5.1?
GLM-5.3 costs $1.40 per million input tokens and $4.40 per million output tokens on Z.ai's list price (Z.ai Pricing, read Nov 2, 2026). Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens on Anthropic's list price (Claude pricing, read Nov 2, 2026).
Scores come from the Models at Work leaderboard: Score is 0 to 100 and computed, not typed: 55% independent evals (Artificial Analysis, Arena, Scale SEAL, Epoch, each scaled against its natural floor and the best score in this table, then averaged), 15% blended price on a fixed log scale ($0.05 per million is 100, $60 is 0), 15% practitioner sentiment from Signals and community threads, 15% operational fit (context window, open weights). A missing component drops out and the rest are reweighted. A model with no independent eval yet is provisional and ranks below every measured one. Within three points is a tie. Vendor-published figures are labelled and never counted. Prices are vendor list prices where published; blended figures assume three input tokens per output token.