Which is cheaper, Claude Opus 5.5 and GLM-5.3?

GLM-5.3 has the lowest input price. Per 1M input tokens: Claude Opus 5.5 from $4.00 and GLM-5.3 from $0.56.

Which has the larger context window, Claude Opus 5.5 and GLM-5.3?

GLM-5.3 has the largest context window: Claude Opus 5.5 1,000,000 tokens and GLM-5.3 1,048,576 tokens.

Can I switch between Claude Opus 5.5 and GLM-5.3 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (anthropic/claude-opus-5.5, z-ai/glm-5.3).

Claude Opus 5.5 vs GLM-5.3

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

Claude Opus 5.5 Anthropicanthropic/claude-opus-5.5

GLM-5.3 Z.aiz-ai/glm-5.3

Creator

Anthropic

Z.ai

Released

Sep 22, 2026

Aug 18, 2026

Context window

1.05M

Max output

128K

131K

Input / 1MLowest provider price

$4.00

$0.56$0.56–$1.40 across 5

Output / 1MLowest provider price

$20.00

$2.50$2.50–$4.40 across 5

Providers

IntelligenceArtificial Analysis index

57.6

44.8

CodingArtificial Analysis index

—

74.8

Accepts

Text, Image, Files

Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Opus 5.5 vs GLM-5.3: summary

Claude Opus 5.5 and GLM-5.3 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Opus 5.5, from Anthropic, has a 1,000,000-token context window, costs $4.00/1M input and $20.00/1M output tokens and scores 57.6 on the Artificial Analysis Intelligence Index.

GLM-5.3, from Z.ai, has a 1,048,576-token context window, costs from $0.56/1M input and $2.50/1M output tokens across 5 providers and scores 44.8 on the Artificial Analysis Intelligence Index.

GLM-5.3 is the cheapest on input, 7.1× cheaper than the next model, GLM-5.3 has the largest context window and Claude Opus 5.5 scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="anthropic/claude-opus-5.5", messages=[...]) # or client.chat.completions.create(model="z-ai/glm-5.3", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis