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Claude Sonnet 5.5 vs GLM 5.3 Flash

Updated October 21, 2026. 79 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace Claude Sonnet 5.5 Replace GLM 5.3 Flash
Claude Sonnet 5.5Anthropic
Coding
88.9
Overall
56.0
Output $/M
$10.00
64
GLM 5.3 FlashZ.ai
Coding
71.0
Overall
41.8
Output $/M
$0.50
13
vs boards won of 79 shared, 2 tied

Decision reading

Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.0 for GLM 5.3 Flash.

Pick GLM 5.3 Flash when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.

Model AClaude Sonnet 5.5Anthropic88.9/1002 independent benchmarksNo cost per solved taskModel BGLM 5.3 FlashZ.ai71.0/1002 independent benchmarks$0.02 per solved task
Shared results
79
Claude Sonnet 5.5 only
16
GLM 5.3 Flash only
23
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
Claude Sonnet 5.5 88.9 from 2 benchmarks, GLM 5.3 Flash 71.0 from 2 benchmarks.
Widest category
Math, 30.8 points apart on average over 6 shared benchmarks.
Widest single gap
ProofBench: Claude Sonnet 5.5 100.0% against GLM 5.3 Flash 21.0%, 79.0 points apart on a 0 to 100 scale.
Output price
Claude Sonnet 5.5 $10.00 against GLM 5.3 Flash $0.50 per million output tokens, 20.0x apart.
Context window
Claude Sonnet 5.5 takes 1M tokens, GLM 5.3 Flash 1.05M.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryClaude Sonnet 5.5BarsGLM 5.3 FlashTies
Coding171
Intelligence20
Agentic work902 ties
Reasoning100
Math51
Knowledge22
Web design70
General129
All shared boards64132 ties
CodingLike-for-likeFour of these boards feed the Vibe Coding Index171
Coding benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
LiveBench coding94.7%80.6%Claude Sonnet 5.5
LMArena WebDev17681607Claude Sonnet 5.5
AA Coding IndexNot measured71.5Only GLM 5.3 Flash measured
LiveCodeBench (Vals AI)Not measured80.5%Only GLM 5.3 Flash measured
SWE-bench Verified (Vals AI)Not measured92.0%Only GLM 5.3 Flash measured
Terminal-Bench 4 (Vals AI)64.1%37.4%Claude Sonnet 5.5
Vibe Code Bench (Vals AI)92.4%30.8%Claude Sonnet 5.5
Code migration (Vals AI)69.8%20.5%Claude Sonnet 5.5
ProgramBench (Vals AI)6.5%0.0%Claude Sonnet 5.5
IOI (Vals AI)83.1%52.5%Claude Sonnet 5.5
Terminal-Bench 2.1 (Vals AI)83.2%62.9%Claude Sonnet 5.5
SWE-bench Multimodal (Vals AI)58.3%Not measuredOnly Claude Sonnet 5.5 measured
Vibe Code Bench 1-100 (Vals AI)Not measured16.0%Only GLM 5.3 Flash measured
SkillsBench (Vals AI)Not measured40.2%Only GLM 5.3 Flash measured
CyberBench (Vals AI)59.6%67.9%GLM 5.3 Flash
SciCode61.0%51.6%Claude Sonnet 5.5
FrontierCode52.1%31.8%Claude Sonnet 5.5
FrontierSWE61.9%18.1%Claude Sonnet 5.5
ALE-Bench1819.1303.6Claude Sonnet 5.5
LMArena Text: coding15131507Claude Sonnet 5.5
LMArena Text: software and IT15041500Claude Sonnet 5.5
LMArena WebDev: React18171624Claude Sonnet 5.5
LMArena WebDev: HTML17411577Claude Sonnet 5.5
LMArena WebDev: from an image17371578Claude Sonnet 5.5
Neither model has a result on the other 14 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
AA Intelligence Index56.041.8Claude Sonnet 5.5
Epoch Capabilities Index166.2153.1Claude Sonnet 5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index90
Agentic work benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
AA Agentic IndexNot measured50.9Only GLM 5.3 Flash measured
Design Arena: agents building web apps1303Not measuredOnly Claude Sonnet 5.5 measured
Design Arena: agents building mobile apps1265Not measuredOnly Claude Sonnet 5.5 measured
Design Arena: spreadsheets1245Not measuredOnly Claude Sonnet 5.5 measured
LiveBench research83.6%70.1%Claude Sonnet 5.5
LiveBench browser84.0%84.0%Tie
LiveBench long agentic78.8%28.4%Claude Sonnet 5.5
SREBench (Vals AI)30.1%0.8%Claude Sonnet 5.5
Finance Agent (Vals AI)58.1%57.9%Claude Sonnet 5.5
Tax Agent Bench (Vals AI)42.0%31.6%Claude Sonnet 5.5
Legal Research Bench (Vals AI)48.1%45.2%Claude Sonnet 5.5
Harvey's Legal Agent Benchmark (Vals AI)10.4%10.4%Tie
Excel Modeling Benchmark (Vals AI)75.7%55.9%Claude Sonnet 5.5
BioMysteryBench (Vals AI)81.1%Not measuredOnly Claude Sonnet 5.5 measured
Terminal-Bench-Science (Vals AI)47.1%2.9%Claude Sonnet 5.5
Vals Science Index59.1%Not measuredOnly Claude Sonnet 5.5 measured
APEX-Agents75.5%52.8%Claude Sonnet 5.5
SpireClimb1.3%Not measuredOnly Claude Sonnet 5.5 measured
Vending-Bench 2$11,165Not measuredOnly Claude Sonnet 5.5 measured
Neither model has a result on the other 20 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index100
Reasoning benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
GPQA DiamondNot measured86.4%Only GLM 5.3 Flash measured
LiveBench reasoning91.6%77.6%Claude Sonnet 5.5
MysteryMechanism (Vals AI)49.1%Not measuredOnly Claude Sonnet 5.5 measured
MMMU Pro (Vals AI)Not measured86.0%Only GLM 5.3 Flash measured
GPQA Diamond (Artificial Analysis run)Not measured91.2%Only GLM 5.3 Flash measured
Humanity's Last Exam (Artificial Analysis run)55.0%39.9%Claude Sonnet 5.5
GPQA Diamond (Epoch AI run)95.6%90.2%Claude Sonnet 5.5
ARC-AGINot measured91.0%Only GLM 5.3 Flash measured
ARC-AGI-2Not measured65.8%Only GLM 5.3 Flash measured
Chess puzzles59.0%21.0%Claude Sonnet 5.5
Mystery game puzzles65.0%8.0%Claude Sonnet 5.5
LMArena Text: hard prompts14941490Claude Sonnet 5.5
LMArena Text: expert15311511Claude Sonnet 5.5
LMArena Text: hard prompts in English15021488Claude Sonnet 5.5
LMArena Vision: diagrams13291317Claude Sonnet 5.5
LMArena Vision: homework13311318Claude Sonnet 5.5
Neither model has a result on the other 5 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index51
Math benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
OTIS Mock AIME100.0%93.9%Claude Sonnet 5.5
FrontierMath, tiers 1 to 388.8%55.8%Claude Sonnet 5.5
FrontierMath, tier 480.5%17.1%Claude Sonnet 5.5
ProofBench100.0%21.0%Claude Sonnet 5.5
LMArena Text: math14971503GLM 5.3 Flash
LMArena Text: mathematical work15101497Claude Sonnet 5.5
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index22
Knowledge benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
MMLU ProNot measured86.1%Only GLM 5.3 Flash measured
LegalBench (Vals AI)Not measured83.9%Only GLM 5.3 Flash measured
TaxEval (Vals AI)Not measured75.6%Only GLM 5.3 Flash measured
MedCode (Vals AI)52.9%Not measuredOnly Claude Sonnet 5.5 measured
SimpleQA Verified46.5%Not measuredOnly Claude Sonnet 5.5 measured
LMArena Text: science14831484GLM 5.3 Flash
LMArena Text: medicine and healthcare14641475GLM 5.3 Flash
LMArena Text: legal and government14831473Claude Sonnet 5.5
LMArena Text: business and finance14681460Claude Sonnet 5.5
Neither model has a result on the other 8 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index70
Web design benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
Design Arena: websites13261272Claude Sonnet 5.5
Design Arena: UI components13671316Claude Sonnet 5.5
Design Arena: game dev14691279Claude Sonnet 5.5
Design Arena: data viz13891262Claude Sonnet 5.5
Design Arena: 3D14581316Claude Sonnet 5.5
Design Arena: all code categories13641282Claude Sonnet 5.5
Design Arena: SVGNot measured1284Only GLM 5.3 Flash measured
Design Arena: ASCII artNot measured1269Only GLM 5.3 Flash measured
LiveBench design85.0%77.2%Claude Sonnet 5.5
GeneralLike-for-likePublic boards, shown as published, kept out of the index129
General benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
Vals Index70.8%50.9%Claude Sonnet 5.5
LiveBench data analysis59.5%76.4%GLM 5.3 Flash
Public Benefits Bench (Vals AI)67.2%Not measuredOnly Claude Sonnet 5.5 measured
SAGE (Vals AI)51.8%Not measuredOnly Claude Sonnet 5.5 measured
MedScribe (Vals AI)91.1%88.9%Claude Sonnet 5.5
Long context reasoning (AA-LCR)82.7%80.0%Claude Sonnet 5.5
DTBench97.3%Not measuredOnly Claude Sonnet 5.5 measured
LMCA68.3%Not measuredOnly Claude Sonnet 5.5 measured
Surface Evolver BenchNot measured52.5%Only GLM 5.3 Flash measured
Furniture assembly75.0%Not measuredOnly Claude Sonnet 5.5 measured
LMArena Text14731471Claude Sonnet 5.5
LMArena Text: instruction following14921478Claude Sonnet 5.5
LMArena Text: creative writing14671441Claude Sonnet 5.5
LMArena Vision12871294GLM 5.3 Flash
LMArena Text: English14841474Claude Sonnet 5.5
LMArena Text: non-English14561462GLM 5.3 Flash
LMArena Text: Chinese15351531Claude Sonnet 5.5
LMArena Text: GermanNot measured1462Only GLM 5.3 Flash measured
LMArena Text: JapaneseNot measured1444Only GLM 5.3 Flash measured
LMArena Text: KoreanNot measured1436Only GLM 5.3 Flash measured
LMArena Text: French14991491Claude Sonnet 5.5
LMArena Text: Spanish14511475GLM 5.3 Flash
LMArena Text: Russian14541465GLM 5.3 Flash
LMArena Text: PolishNot measured1450Only GLM 5.3 Flash measured
LMArena Text: multi-turn14651469GLM 5.3 Flash
LMArena Text: longer queries14951481Claude Sonnet 5.5
LMArena Text: writing and language14741455Claude Sonnet 5.5
LMArena Text: entertainment and media14611440Claude Sonnet 5.5
LMArena Vision: English12891295GLM 5.3 Flash
LMArena Vision: ChineseNot measured1363Only GLM 5.3 Flash measured
LMArena Vision: reading text12971299GLM 5.3 Flash
LMArena Vision: humorNot measured1279Only GLM 5.3 Flash measured
LMArena Vision: creative writing12421270GLM 5.3 Flash
Neither model has a result on the other 13 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Claude Sonnet 5.5 and GLM 5.3 Flash
BenchmarkClaude Sonnet 5.5GLM 5.3 FlashLeader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Claude Sonnet 5.5$0.0070Fits in one request
GLM 5.3 Flash$0.0004Fits in one request

GLM 5.3 Flash costs less

Repository review

50K input + 3K output tokens

Claude Sonnet 5.5$0.130Fits in one request
GLM 5.3 Flash$0.0090Fits in one request

GLM 5.3 Flash costs less

Agent loop

200K input + 10K output tokens

Claude Sonnet 5.5$0.500Fits in one request
GLM 5.3 Flash$0.035Fits in one request

GLM 5.3 Flash costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Claude Sonnet 5.5 and GLM 5.3 Flash
SpecificationAnthropic Claude Sonnet 5.5Z.ai GLM 5.3 Flash
MakerAnthropicZ.ai
WeightsNo public weights listedOpen weights
ReleasedSeptember 28, 2026August 26, 2026
Context window1M1.05M
Input $/Mtok$2.00$0.15
Output $/Mtok$10.00$0.50
Coding index88.971.0
Independent measurements behind it22
Cost per solved taskNot computable$0.02
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Sonnet 5.5 better than GLM 5.3 Flash for coding?

Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.0 for GLM 5.3 Flash. Pick GLM 5.3 Flash when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.

Which is cheaper, Claude Sonnet 5.5 or GLM 5.3 Flash?

Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; GLM 5.3 Flash costs $0.15 and $0.50. Cost per solved task is known for GLM 5.3 Flash only.

Which has the bigger context window, Claude Sonnet 5.5 or GLM 5.3 Flash?

GLM 5.3 Flash, with 1.05M tokens against 1M.

How many benchmarks is the Claude Sonnet 5.5 vs GLM 5.3 Flash comparison based on?

79 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5's coding index rests on 2 independent benchmarks and GLM 5.3 Flash's on 2. Where only one model has a result, the page says so instead of naming a winner.

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