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

GLM-5.3-Flash has the lowest input price. Per 1M input tokens: Claude Opus 5.5 from $4.00 and GLM-5.3-Flash from $0.07.

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

GLM-5.3-Flash has the largest context window: Claude Opus 5.5 1,000,000 tokens and GLM-5.3-Flash 1,310,720 tokens.

Which is smarter, Claude Opus 5.5 and GLM-5.3-Flash?

Claude Opus 5.5 scores highest on the Artificial Analysis Intelligence Index: Claude Opus 5.5 57.6 and GLM-5.3-Flash 41.8.

Can I switch between Claude Opus 5.5 and GLM-5.3-Flash 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-flash).

Claude Opus 5.5 vs GLM-5.3-Flash

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-Flash Z.aiz-ai/glm-5.3-flash

Creator

Anthropic

Z.ai

Released

Sep 22, 2026

Aug 26, 2026

Context window

1.31M

Max output

128K

131K

Input / 1MLowest provider price

$4.00

$0.07$0.07–$0.15 across 5

Output / 1MLowest provider price

$20.00

$0.25$0.25–$0.50 across 5

Providers

IntelligenceArtificial Analysis index

57.6

41.8

CodingArtificial Analysis index

—

71.5

Accepts

Text, Image, Files

Text, Image, Video

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Opus 5.5 vs GLM-5.3-Flash: summary

Claude Opus 5.5 and GLM-5.3-Flash 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-Flash, from Z.ai, has a 1,310,720-token context window, costs from $0.07/1M input and $0.25/1M output tokens across 5 providers and scores 41.8 on the Artificial Analysis Intelligence Index.

GLM-5.3-Flash is the cheapest on input, 57× cheaper than the next model, GLM-5.3-Flash 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-flash", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis