GLM-5.1

GLM-5.1 is Z.AI's flagship coding model, built for long-horizon software tasks that require autonomous planning, bug fixing, and iterative refinement.

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input · usd / 1m tok

$1.40

output · usd / 1m tok

$4.40

context window

200ktokens

modalities · in → out

pricing

base api ratesusd per 1m tokens

input: $1.40
output: $4.40
cache read: $0.26

providers

Z.AI hosts GLM-5.1. Impossibl routes your request intelligently and handles failover automatically when a provider is down.

Z.AI

specifications

takes text in, gives text outzai/glm-5.1

creatorZ.AI
model typeText generation
context window200,000 tokens
maximum outputnot published
input
takes text in, gives text out
outputtext
tool callingnot verified
releasedapr 7, 2026
endpoint/v1/chat/completions

unknown means the public catalog does not establish that fact. a model's documented capabilities can differ from what a particular api supports. see the model documentation for integration details.

try it · your prompt, this model, live

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="zai/glm-5.1",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="zai/glm-5.1",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

benchmarks

intelligence index

26.4#40 of 90 models on the gateway

coding index55.8#39 of 60
agentic index25.2#32 of 49
omniscience0.8#35 of 86
gpqa86.8%#45 of 88
humanity’s last exam30.1%#43 of 89
terminal-bench v2.161.8%#36 of 57

Tau297.7%
GPQA86.8%
IFBench76.3%
AA-LCR73.7%
Terminal-Bench v2.161.8%
SciCode44.8%
Terminal-Bench Hard43.2%
ITBench40.3%
Humanity’s Last Exam30.1%
AutomationBench Partial20.3%
Tau Banking13.6%
GDP.pdf All-pass8.4%
CritPt4.6%
Terminal-Bench v4.02.0%

Intelligence Index26.45
Omniscience Index0.85
GDPval Elo1180.01
coding index (API)55.8
agentic index (API)25.2
intelligence index (API)26.4

view source ↗all source data and breakdowns (json) ↗

each configuration is listed separately; these evaluations describe the tested model configuration, and performance and costs can differ on impossibl. unmeasured scores are omitted and api values keep their source units. last checked 2026-09-11.

compare GLM-5.1 with other models

frontier labs and open weights, best-ranked firstusd / 1m tok · in / out

anthropic/claude-fable-5-1$10.00 / $50.00compare →
openai/gpt-6-astra$10.00 / $50.00compare →
meta/muse-spark-1.3$1.25 / $4.25compare →
moonshotai/kimi-k3$3.00 / $15.00compare →

impossibl models --all →

frequently asked questions

What is GLM-5.1?

GLM-5.1 is Z.AI's flagship coding model, built for long-horizon software tasks that require autonomous planning, bug fixing, and iterative refinement. Where earlier GLM models were designed around minute-level interactions, GLM-5.1 can work independently and continuously for hours in a single run.

How much does GLM-5.1 cost?

GLM-5.1 costs $1.40 per million input tokens and $4.40 per million output tokens through the Impossibl API. Cache reads cost $0.26 per million tokens. All rates are in USD.

view the pricing table ↑

What is the context length of GLM-5.1?

GLM-5.1 has a 200,000-token context window through the Impossibl API.

What inputs and outputs does GLM-5.1 support?

GLM-5.1 accepts text as input. GLM-5.1 returns text.

How do I use GLM-5.1 through an API?

GLM-5.1 is available through the Impossibl API. Use zai/glm-5.1 as the model identifier with /v1/chat/completions. The quickstart explains how to create an API key and send your first request.

follow the api quickstart →

When was GLM-5.1 released?

Z.AI released GLM-5.1 on April 7, 2026.

Creator release announcement ↗

this page describes GLM-5.1 as listed by the impossibl public api. prices and availability come from that catalog, refreshed here every five minutes. this is an impossibl offering, not a comparison of independent hosting-provider quotes. model descriptions and release dates, where available, use the creator sources linked under the answers above.

view the source catalog ↗model as markdown ↗report a correction →