Model comparison
GLM 5.3 vs GPT-5.5
Z.ai against OpenAI, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
Z.ai
GLM 5.3
Frontier · Open weights
OpenAI
GPT-5.5
Frontier
| Specification | GLM 5.3 | GPT-5.5 |
|---|---|---|
| Provider | Z.ai | OpenAI |
| Tier | Frontier | Frontier |
| Context window | 1M | Winner: 1.05M |
| Max output | 128K | 128K |
| Input / 1M tokens | Winner: $1.40 | $5 |
| Output / 1M tokens | Winner: $4.40 | $30 |
| Weights | Open | Closed |
| Parameters | 753B total (MoE; active count unpublished) | Not disclosedUnverified |
| Reasoning levels | low, high, max | none, low, medium, high, xhigh, max |
| Modalities | text | text, image |
| License | glm-5.3 (custom) | Not disclosedUnverified |
| API model id | glm-5.3 | gpt-5.5 |
| Released | August 14, 2026 | April 23, 2026 |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | 60 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [xhigh] (2026-08-14) | Not verifiedUnverified | 58 |
| Terminal-Bench 2.1 (2026-08-14) | Winner: 88.2 | 83.4 |
| DeepSWE 1.1 (2026-08-14) | 66.9 | Not verifiedUnverified |
| Humanity's Last Exam (2026-08-14) | Winner: 62.5 | 52.2 |
| SWE-bench Verified (2026-09-01) | Winner: 95.4 | 82.6 |
| GPQA Diamond (2026-07-27) | Not verifiedUnverified | 93.5 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-09-01: vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only); official SWE-bench not publishedReal GitHub issue resolution: does the model's patch pass the hidden tests. Comparability: comparable with caveat — Post-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
- 2026-08-14: Z.ai GLM-5.3 blog + HF model card (vendor, with tools, full set)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
- 2026-07-27: Kimi K3 model card (vendor-reported, xhigh); announcement charts show 93.6 — minor conflict preservedAgentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-04-23: OpenAI — Introducing GPT-5.5 (vendor, with tools; 41.4 no tools)Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise. Comparability: comparable with caveat — Subset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.
Pricing tiers: GLM 5.3: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished). · GPT-5.5: Standard $5/$30 per MTok; >272K input billed 2x in / 1.5x out. Cached input $0.50/MTok; batch $2.50/$15.
GLM 5.3
GLM 5.3 is Zhipu's flagship (~753B MoE), near the top of the leaderboards, and the current GLM Coding Plan default.
Best for
- Coding Plan subscribers
- Long-horizon coding
- Chinese + English
Watch out
Open weights dropped 2026-08-28 under Z.ai's custom glm-5.3 licence (not a standard open-source licence — review before commercial use; secondary coverage says >$10B-revenue providers need a security review). 5.2/5.1 Coding Plan requests route to 5.3.
GPT-5.5
GPT-5.5 is OpenAI's previous flagship — strong on Terminal-Bench 2.0 (82.7%) and 1M-token context.
Best for
- Reasoning
- Agentic coding
- Long-context work
Watch out
Superseded by GPT-5.6 Sol on quality; still a capable, widely integrated model.
When the cheaper one wins
GLM 5.3 is cheaper on output at $4.40 per million tokens against $30 for GPT-5.5 — about 6.8×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 4 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Terminal-Bench 2.1, Humanity's Last Exam, SWE-bench Verified.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- GLM 5.3: Z.ai GLM-5.3 announcement (accessed 2026-08-29)
- GLM 5.3: Hugging Face — zai-org/GLM-5.3 (weights, 2026-08-28) (accessed 2026-08-30)
- GPT-5.5: OpenAI — Introducing GPT-5.5 (accessed 2026-08-29)
- GPT-5.5: OpenAI API pricing (gpt-5.5 $5/$30) (accessed 2026-08-29)
Related comparisons
Common questions
GLM 5.3 vs GPT-5.5
Answered from the verified figures on this page rather than general guidance.
Is GLM 5.3 or GPT-5.5 cheaper for input?
GLM 5.3 is cheaper at $1.40 per million input tokens, against $5 for GPT-5.5 — roughly 3.6× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GLM 5.3 has tiered pricing: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished). GPT-5.5 has tiered pricing: Standard $5/$30 per MTok; >272K input billed 2x in / 1.5x out. Cached input $0.50/MTok; batch $2.50/$15.
Is GLM 5.3 or GPT-5.5 cheaper for output?
GLM 5.3 is cheaper at $4.40 per million output tokens, against $30 for GPT-5.5 — roughly 6.8× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GLM 5.3 has tiered pricing: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished). GPT-5.5 has tiered pricing: Standard $5/$30 per MTok; >272K input billed 2x in / 1.5x out. Cached input $0.50/MTok; batch $2.50/$15.
Which has the larger context window, GLM 5.3 or GPT-5.5?
GPT-5.5 accepts 1.05M tokens against 1M for GLM 5.3. This only matters if you routinely send very long documents or large codebases.
Do GLM 5.3 and GPT-5.5 support the same reasoning levels?
GLM 5.3 exposes low, high, max, while GPT-5.5 exposes none, low, medium, high, xhigh, max.
Should I use GLM 5.3 or GPT-5.5?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GLM 5.3 suits coding plan subscribers; GPT-5.5 suits reasoning.
Can I self-host GLM 5.3 or GPT-5.5?
GLM 5.3 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. GPT-5.5 is a closed model whose supported access paths are controlled by its provider.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: GLM 5.3 costs $1.40 per 1M tokens versus $5 for GPT-5.5 — a 3.6x difference at the headline tier.
- Context: GPT-5.5 takes 1.05M against 1M for GLM 5.3 — only decisive if your prompts approach the smaller window.
- Measured capability: GLM 5.3 leads Artificial Analysis Intelligence Index 60 to 58 (measured 2026-08-14).
- Deployment: GLM 5.3 publishes weights you can self-host; the other is API-only.
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.