LLM Reference

GPT-5.5 vs Kimi K2.5

GPT-5.5 (2026) and Kimi K2.5 (2026) compare a standalone API model against a coding-specialized model. GPT-5.5 ships a 1.05m-token context window, while Kimi K2.5 ships a 256k-token context window. On MMLU PRO, GPT-5.5 leads by 1 pts. On pricing, GPT-5.5 ranges from $5 to $8/1M input tokens by tier; Kimi K2.5 costs $0.44/1M input tokens. This page treats the result as workflow and deployment fit, not a universal model winner.

Treat this as a product-type comparison: GPT-5.5 is standalone API model, while Kimi K2.5 is coding-specialized model. Choose based on workflow fit before reading any benchmark or price row as decisive.

Decision scorecard

Local evidence first
SignalGPT-5.5Kimi K2.5
Product typeStandalone API modelCoding-specialized model
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentscustom coding agents, code generation, and tool loops
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1.05m256k
Cheapest output$30/1M tokens$2/1M tokens
Provider routes4 tracked10 tracked
Shared benchmarksMMLU PRO leader14 shared

Decision tradeoffs

Choose GPT-5.5 when...
  • GPT-5.5 holds a shared-benchmark lead on MMLU PRO, ahead by 1 points.
  • GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • GPT-5.5 uniquely exposes Reasoning and Code execution in local model data.
  • Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
Choose Kimi K2.5 when...
  • Kimi K2.5 holds a shared-benchmark lead on AIME 2025, ahead by 14.9 points.
  • Kimi K2.5 has the lower cheapest tracked output price at $2/1M tokens.
  • Kimi K2.5 has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags Kimi K2.5 for Coding, RAG, and Agents.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate Kimi K2.5

GPT-5.5

$11,500

Cheapest tracked route/tier: OpenAI API 0-272K input tokens

Kimi K2.5

$852

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $10,648. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

GPT-5.5 -> Kimi K2.5
  • Provider overlap exists on OpenRouter, AWS Bedrock, and Vercel AI Gateway; start route-level A/B tests there.
  • Kimi K2.5 is $28/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning and Code execution before moving production traffic.
Kimi K2.5 -> GPT-5.5
  • Provider overlap exists on OpenRouter, Vercel AI Gateway, and AWS Bedrock; start route-level A/B tests there.
  • GPT-5.5 is $28/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • GPT-5.5 adds Reasoning and Code execution in local capability data.

Specs

Specification
Released2026-04-232026-03-15
Context window1.05m256k
Parameters—1T (MoE, 384 experts)
ArchitectureDecoder OnlyMixture of Experts
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-12-

Pricing and availability

Pricing attributeGPT-5.5Kimi K2.5
Input price
0-272K input tokens
$5/1M tokens
Standard GPT-5.5 token pricing before the long-context surcharge threshold.
272K+ input tokens
$8/1M tokens
Long-context surcharge applies above 272K input tokens for the full session.
$0.44/1M tokens
Output price
0-272K input tokens
$30/1M tokens
Standard GPT-5.5 token pricing before the long-context surcharge threshold.
272K+ input tokens
$36/1M tokens
Long-context surcharge applies above 272K input tokens for the full session.
$2/1M tokens
Providers
OpenAI APIOpenRouterVercel AI GatewayAWS Bedrock
Cloudflare Workers AIFireworks AIOpenRouterTogether AINVIDIA NIMAWS Bedrock

Capabilities

CapabilityGPT-5.5Kimi K2.5
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesNo
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkGPT-5.5Kimi K2.5
MMLU PRO88.187.1
SWE-bench Verified82.676.8
Google-Proof Q&A93.687.9
AIME 202581.296.1
Humanity's Last Exam41.450.2
MCP-Atlas75.329.5
CursorBench64.331.9
Terminal-Bench 2.082.750.8
CursorBench58.431.9
CursorBench58.431.9
BrowseComp84.460.6
CursorBench53.831.9
CursorBench46.631.9
MMMU Pro88.378.5

Continue comparing

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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.