GPT-5.5 vs GPT-6 Luna
GPT-6 Luna leads on reasoning and tool use; coding is a statistical tie; GPT-6 Luna is cheaper per million tokens.
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As of 26 Oct 2026, 11:37 UTC · 24-hour board
- 82
- GPT-5.5 on the Combined board, last 24 hours · joint 16th of 24
- 92
- GPT-6 Luna on the Combined board, last 24 hours · joint 1st of 24
- 59×
- price gap per token: GPT-5.5 lists at $5 in / $30 out per 1M tokens, GPT-6 Luna at $0.10 in / $0.50 out
01
GPT-5.5 vs GPT-6 Luna at a glance
Both models on the same four boards, the same list-price view and the same drift detectors. Scores carry their standard error; a place is shared, written joint, when the gap is inside that noise.
| Measure | GPT-5.5 | GPT-6 Luna |
|---|---|---|
| Combinedscore ± standard error · place, 24-hour board | 82 ± 2.3joint 16th of 24 | 92 ± 2.3joint 1st of 24 |
| Codingscore ± standard error · place, 24-hour board | 94 ± 0.9joint 5th of 24 | 92 ± 0.8joint 11th of 24 |
| Reasoningscore ± standard error · place, 24-hour board | 60 ± 2.5joint 17th of 22 | 97 ± 2.5joint 1st of 22 |
| Tool usescore ± standard error · place, 24-hour board | 78 ± 2.5joint 14th of 22 | 87 ± 2.5joint 1st of 22 |
| List price per 1M tokensinput / output · blended 40/60 | $5 / $30$20 blended | $0.10 / $0.50$0.34 blended |
| Median response timecoding tasks, last 30 days | 12 s | 3.5 s |
| Pass ratecoding attempts, last 30 days | 87% | 92% |
| Cost per 1,000 correct answerscoding, last 30 days, every attempt billed | $19.96 | $0.31 |
| Drift statustrend on the 24-hour board · Page-Hinkley per suite | Holding steadyno detection on coding, reasoning and tool use | Holding steadyno detection on coding, reasoning and tool use |
| Tracked since | 27 Apr 2026182 days | 22 Sep 202633 days |
The boards re-rank after every run, so the figures here follow the leaderboard: each model’s own page, GPT-5.5 and GPT-6 Luna, carry the full history. The whole board for each category is on best LLM for coding, best LLM for reasoning and best AI model for agents.
02
Is GPT-5.5 better than GPT-6 Luna for coding?
The Coding board: seven repository debugging tasks graded by running the project’s own tests, including hidden tests the model never sees, re-tested every four hours.
GPT-5.5 scores 94 ± 0.9 — joint 5th of the 24 models on the Coding board in the last 24 hours. GPT-6 Luna scores 92 ± 0.8 — joint 11th of the 24 models on the Coding board in the last 24 hours. The gap of 2 points is within the measurement noise, so head to head the two are a statistical tie on coding; the board places them apart because a place is set against the leader of the group above, not against the other model.
Over the last 30 days, GPT-5.5 passed 87% of its coding attempts and GPT-6 Luna 92%.
See every model on the Coding board on best LLM for coding, or each model’s own page, GPT-5.5 and GPT-6 Luna.
03
Is GPT-5.5 better than GPT-6 Luna for reasoning?
The Reasoning board: four long, multi-turn working sessions every day, with continuity checked by running code against rules stated earlier in the session.
GPT-5.5 scores 60 ± 2.5 — joint 17th of the 22 models on the Reasoning board in the last 24 hours. GPT-6 Luna scores 97 ± 2.5 — joint 1st of the 22 models on the Reasoning board in the last 24 hours. The gap of 37 points is beyond the measurement noise, so GPT-6 Luna leads on reasoning.
See every model on the Reasoning board on best LLM for reasoning.
04
Is GPT-5.5 or GPT-6 Luna better for agents and tool calling?
The Tool use board: nine tasks, each in a real sandboxed machine — either the job is done at the end or it is not. Task completion, tool selection, parameter accuracy, efficiency, error handling, context awareness and safety are scored.
GPT-5.5 scores 78 ± 2.5 — joint 14th of the 22 models on the Tool use board in the last 24 hours. GPT-6 Luna scores 87 ± 2.5 — joint 1st of the 22 models on the Tool use board in the last 24 hours. The gap of 9 points is beyond the measurement noise, so GPT-6 Luna leads on tool use.
See every model on the Tool use board on best AI model for agents.
05
Which is cheaper, GPT-5.5 or GPT-6 Luna?
List prices are each provider’s standard rate per million tokens, cache-miss input and output. Cost per correct answer counts every attempt on the coding tasks, failed ones included, over the last 30 days.
GPT-5.5 lists at $5 in / $30 out per 1M tokens; GPT-6 Luna at $0.10 in / $0.50 out.
On a 40/60 input–output blend, GPT-5.5 costs about 59× as much per token as GPT-6 Luna.
Over the last 30 days, 1,000 correct coding answers cost about $19.96 with GPT-5.5 and $0.31 with GPT-6 Luna, every attempt billed, failed ones included.
The cheapest model that still passes the tests is on best value AI model.
06
Which is faster, GPT-5.5 or GPT-6 Luna?
Median response time of one attempt or one session, from the same runs as the scores, over the last 30 days.
Median response time on the coding tasks over the last 30 days: GPT-5.5 12 s, GPT-6 Luna 3.5 s.
GPT-6 Luna answers about 3.4× faster.
On the reasoning sessions 1.7 min against 2.1 min and on the tool-use sessions 1.9 min against 1.7 min (GPT-5.5 first).
Every model’s median is on fastest AI model.
07
Is GPT-5.5 or GPT-6 Luna getting worse?
Page-Hinkley change-point detection (a CUSUM-family test) runs per suite on each model’s daily median, with every constant published; a real shift is confirmed over days, not hours. An hourly canary of two fixed coding probes catches sharp drops.
GPT-5.5 is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use.
GPT-6 Luna is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use.
The family pages answer the question for every model of a provider: Is ChatGPT getting worse?. The method is on AI drift detection.
Three models free · email when a watched model's coding score falls five points in a week
Three models free · email when a watched model's coding score falls five points in a week
08
Should I use GPT-5.5 or GPT-6 Luna?
Only a difference that clears a threshold counts: a board lead beyond the measurement noise (the leaderboard’s own tie rule), 10% on list price, 20% on response time or cost per correct answer.
Choose GPT-6 Luna when
- the work is reasoning: it leads the Reasoning board by 37 points in the last 24 hours (97 ± 2.5 against 60 ± 2.5)
- the work is tool use: it leads the Tool use board by 9 points in the last 24 hours (87 ± 2.5 against 78 ± 2.5)
- price per token matters: it lists at $0.10 in / $0.50 out per 1M tokens against $5 in / $30 out
- cost per correct answer matters: about $0.31 per 1,000 correct coding answers against $19.96 over the last 30 days
- response time matters: a median of 3.5 s on the coding tasks against 12 s over the last 30 days
No difference clears a threshold in favour of GPT-5.5.
09
Can I route between GPT-5.5 and GPT-6 Luna automatically?
One OpenAI-compatible endpoint sends each request to whichever model the boards favour for that kind of work, with your own provider keys.
Yes. The Smart Router is one OpenAI-compatible endpoint with 14 auto-* routing modes: a quality mode such as auto-coding sends each request to the model placing highest on that board, the value modes pick within 5 points of the best and then the cheapest measured cost per run, and auto-split sends traffic by weights you set. Routing is drift-aware by default, uses your own provider keys and adds zero markup on tokens. Free includes 1,000 routed requests a month.
Every mode is described in the router documentation.
1,000 routed requests a month free · your own provider keys · no card
10
How we test GPT-5.5 and GPT-6 Luna
Every model on the board runs the same tasks on the same schedule: coding every four hours, reasoning and tool use daily, with an hourly canary probe.
Scores come from our own runs through each provider’s public API, not vendor-reported numbers. Every model gets the same prompts and output budget, and the same sampling settings wherever a provider accepts them, and is graded by executing what it produces. Every score carries a standard error from its own run-to-run repeatability; models whose lead is inside that noise share a place, written joint.
The methodology is public — every weight, statistical test and drift constant. The test tasks are private, so no lab can train on them. The full method, weights and constants are on the methodology page.
11
GPT-5.5 vs GPT-6 Luna: questions people ask
Is GPT-5.5 better than GPT-6 Luna for coding?
GPT-5.5 scores 94 ± 0.9 — joint 5th of the 24 models on the Coding board in the last 24 hours. GPT-6 Luna scores 92 ± 0.8 — joint 11th of the 24 models on the Coding board in the last 24 hours. The gap of 2 points is within the measurement noise, so head to head the two are a statistical tie on coding; the board places them apart because a place is set against the leader of the group above, not against the other model. Over the last 30 days, GPT-5.5 passed 87% of its coding attempts and GPT-6 Luna 92%.
Is GPT-5.5 better than GPT-6 Luna for reasoning?
GPT-5.5 scores 60 ± 2.5 — joint 17th of the 22 models on the Reasoning board in the last 24 hours. GPT-6 Luna scores 97 ± 2.5 — joint 1st of the 22 models on the Reasoning board in the last 24 hours. The gap of 37 points is beyond the measurement noise, so GPT-6 Luna leads on reasoning.
Is GPT-5.5 or GPT-6 Luna better for agents and tool calling?
GPT-5.5 scores 78 ± 2.5 — joint 14th of the 22 models on the Tool use board in the last 24 hours. GPT-6 Luna scores 87 ± 2.5 — joint 1st of the 22 models on the Tool use board in the last 24 hours. The gap of 9 points is beyond the measurement noise, so GPT-6 Luna leads on tool use.
Which is cheaper, GPT-5.5 or GPT-6 Luna?
GPT-5.5 lists at $5 in / $30 out per 1M tokens; GPT-6 Luna at $0.10 in / $0.50 out. On a 40/60 input–output blend, GPT-5.5 costs about 59× as much per token as GPT-6 Luna. Over the last 30 days, 1,000 correct coding answers cost about $19.96 with GPT-5.5 and $0.31 with GPT-6 Luna, every attempt billed, failed ones included.
Which is faster, GPT-5.5 or GPT-6 Luna?
Median response time on the coding tasks over the last 30 days: GPT-5.5 12 s, GPT-6 Luna 3.5 s. GPT-6 Luna answers about 3.4× faster. On the reasoning sessions 1.7 min against 2.1 min and on the tool-use sessions 1.9 min against 1.7 min (GPT-5.5 first).
Is GPT-5.5 or GPT-6 Luna getting worse?
GPT-5.5 is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use. GPT-6 Luna is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use. Page-Hinkley change-point detection (a CUSUM-family test) runs per suite on each model’s daily median, with every constant published; a real shift is confirmed over days, not hours. An hourly canary of two fixed coding probes catches sharp drops.
Should I use GPT-5.5 or GPT-6 Luna?
GPT-6 Luna leads on reasoning and tool use; coding is a statistical tie; GPT-6 Luna is cheaper per million tokens. Choose GPT-6 Luna when the work is reasoning: it leads the Reasoning board by 37 points in the last 24 hours (97 ± 2.5 against 60 ± 2.5); the work is tool use: it leads the Tool use board by 9 points in the last 24 hours (87 ± 2.5 against 78 ± 2.5); price per token matters: it lists at $0.10 in / $0.50 out per 1M tokens against $5 in / $30 out; cost per correct answer matters: about $0.31 per 1,000 correct coding answers against $19.96 over the last 30 days; response time matters: a median of 3.5 s on the coding tasks against 12 s over the last 30 days.
Can I route between GPT-5.5 and GPT-6 Luna automatically?
Yes. The Smart Router is one OpenAI-compatible endpoint with 14 auto-* routing modes: a quality mode such as auto-coding sends each request to the model placing highest on that board, the value modes pick within 5 points of the best and then the cheapest measured cost per run, and auto-split sends traffic by weights you set. Routing is drift-aware by default, uses your own provider keys and adds zero markup on tokens. Free includes 1,000 routed requests a month.
Route between them automatically
The Smart Router sends each request to whichever of GPT-5.5 and GPT-6 Luna — or any model on the board — the boards favour for that kind of work, with your own provider keys and zero markup on tokens.
1,000 routed requests a month free · your own provider keys · no card
Free account · 24 hours, 7 days and 30 days · no card
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