Claude Haiku 5.5 vs GPT-6 Luna: Price & Which to Pick (2026)

Comparison · October 2026

Claude Haiku 5.5 (Anthropic API) and GPT-6 Luna (OpenAI API) are two chat models teams actually route in 2026. This is a decision guide, not a leaderboard dump: published API rates, three workload cost scenarios, live writing and coding snippets, and a pick matrix you can rerun. If you want both without juggling tabs, use a multi-model AI workspace or start on i10X.

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Persona picker

You are…	Start with	Why
Writer / marketer	Either; A/B on brand voice	Claude Haiku 5.5: Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff. GPT-6 Luna: Same facts in a short note, no name slot, under 120 words.
Developer / agent builder	GPT-6 Luna for huge repos; Claude Haiku 5.5 for cheap loops	Window 1.05M vs 1M. Micro-test: Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. / Named ZeroDivisionError. Short ValueError guard. No extra options.
Researcher / analyst	GPT-6 Luna	1M vs 1.05M on the cards we pulled.
Budget / high volume	Either on chat	Matched chat cost in this recipe. Check output and cache.

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What we are comparing (exact versions)

This page compares two specific API models, not vague brand names and not last quarter’s IDs. Nearby versioned pages: Claude Haiku 4.5 vs GPT-5.6 Luna, Gemini 3.7 Flash vs GPT-5.6 Luna, Claude Sonnet 5.5 vs GPT-6.1 Sol, MiniMax M3 vs GPT-5.6 Luna, Grok 4.7 vs GPT-6.1 Sol, and Claude Opus 5.5 vs GPT-6.1 Sol.

Field	Claude Haiku 5.5	GPT-6 Luna
Provider	Anthropic	OpenAI
API model	Claude Haiku 5.5 (Anthropic API)	GPT-6 Luna (OpenAI API)
Listed card name	Anthropic: Claude Haiku 5.5	OpenAI: GPT-6 Luna
Family / tier	Claude 5.5 fast / cheap tier	GPT-6 fast / cheap tier
App vs API note	Also in Claude apps; this article uses the API model above	Also in ChatGPT-family apps; this article uses the API model above

If a page still compares older IDs as if they were these cards, treat it as historical. For routing across many models, see AI model routing.

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Spec sheet (API card, 2026-10-12)

Spec	Claude Haiku 5.5	GPT-6 Luna
Context window	1,000,000 tokens	1,050,000 tokens
Input modalities (card)	text, image, file	text, image, file
Output	text	text
Open weights	No	No
Vendor positioning (card)	Small, fast successor to Haiku 4.5; high-volume summarization, subagents, browser use	Fast, cost-efficient GPT-6 tier below Sol; high-volume chat, classification, lightweight agents

We did not invent max-output, reasoning-mode, or realtime-search rows. Those fields were not on the cards we pulled for this pair. If your product depends on a specific tool or effort switch, confirm it on the live vendor page before you ship.

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Pricing and real workload cost

List prices are easy to game. Workload cost is what you feel. Numbers below use published per-million rates as of 2026-10-12. Verify live before you budget.

Price	Claude Haiku 5.5	GPT-6 Luna
Input / 1M tokens	$0.10	$0.10
Output / 1M tokens	$0.50	$0.50
Cache read / 1M	$0.01	$0.01

Same input sticker ($0.10). Matched output at $0.50. Cache reads match on this pull.

Scenario	Assumed tokens	Est. Claude Haiku 5.5	Est. GPT-6 Luna
Chat turn	1k in + 0.5k out	$0.00035	$0.00035
Repo / doc review	80k in + 4k out	$0.010	$0.010
Agent loop	200k in (50% cached) + 20k out	$0.021	$0.021

On the cached agent recipe, neither wins ($0.021 vs $0.021). Re-run the math if you cache harder. For subscription stacks, see AI subscription stack cost.

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Performance by job (not one score)

Public benches disagree by harness, effort mode, and date. We are not inventing index numbers we do not have for this pair. Treat vendor cards as positioning, treat our snippets as a small live pack, and prefer your own side-by-side on your prompts. Method: side-by-side AI comparison.

Coding and agents

Small, fast successor to Haiku 4.5; high-volume summarization, subagents, browser use. Fast, cost-efficient GPT-6 tier below Sol; high-volume chat, classification, lightweight agents. Those are positioning lines, not benches. Our micro-test: Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. Named ZeroDivisionError. Short ValueError guard. No extra options. Window size and cache price matter more on long agent loops than this snippet.

Writing and tone

Claude Haiku 5.5 for Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff. GPT-6 Luna for Same facts in a short note, no name slot, under 120 words. If your brand wants send-ready client email, prefer the tighter letter. If you hate filler, prefer the shorter note.

Research, math, reasoning

We did not run a science-QA pack, so we will not fake one. False-premise: Strong geology refuse, then Earth-realistic protein routes and lunar ice as support, not cheese. Refuse in two sentences. Suggests Earth beans and tofu. Thin as a plan. For publishable work, add multi-model hallucination checks.

Multimodal and long context

Claude Haiku 5.5 lists text, image, file in, text out. GPT-6 Luna lists text, image, file in, text out. Context is 1,000,000 tokens vs 1,050,000 tokens. Giant packs go to the larger window. Audio or video only if the card actually lists it.

Speed

No tok/s in this pack. Measure p50 from your API region. Do not ship on a third-party screenshot.

Job	Edge	Why
Hard coding / agents	Claude Haiku 5.5	Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. Named ZeroDivisionError. Short ValueError guard. No extra options.
Everyday writing	Split	Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff. Same facts in a short note, no name slot, under 120 words.
Long docs / multimodal	GPT-6 Luna	1.05M vs 1M. Input set: text, image, file vs text, image, file.
Realtime / conversational	Product-dependent	Product-dependent. Confirm tools, voice, and search in the app you actually ship. Not measured here.
Cost at volume	Split	Chat matched. Repo $0.010 vs $0.010. Cached agent $0.021 vs $0.021.

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Side-by-side test (i10X pack, 2026-10-12)

Same three prompts, scored 1-5 on instruction following, depth, factual caution, style, and usefulness (max 25). Writing, coding, and false premise only. No invented extra scores.

Test 1: Client email rewrite

Task: Keep every fact. Warmer. Under 120 words.

Claude Haiku 5.5 (excerpt, sanitized): Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff.

GPT-6 Luna (excerpt, sanitized): Same facts in a short note, no name slot, under 120 words.

Edge: Split. A/B on brand voice. Neither is allowed to drop Q3, Tuesday, Friday, Wednesday, finance, or Acme.

Test 2: Empty-list average bug

Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. Named ZeroDivisionError. Short ValueError guard. No extra options. Claude Haiku 5.5.

Test 3: False premise (Moon cheese)

Strong geology refuse, then Earth-realistic protein routes and lunar ice as support, not cheese. Refuse in two sentences. Suggests Earth beans and tofu. Thin as a plan. Claude Haiku 5.5.

Prompt type	Claude Haiku 5.5	GPT-6 Luna	Note
Client email rewrite	23/25	23/25	Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff.
Bug explain + minimal fix	24/25	23/25	Named ZeroDivisionError. None vs ValueError. Guard must come before the divide.
Logic + false premise	24/25	20/25	Strong geology refuse, then Earth-realistic protein routes and lunar ice as support, not cheese.
Total	71/75	66/75	Claude Haiku 5.5 won this three-prompt pack (71/75 vs 66/75). That does not erase the other model’s cost or context edge. Route the next step.

Claude Haiku 5.5 won this three-prompt pack (71/75 vs 66/75). That does not erase the other model’s cost or context edge. Route the next step.

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Ecosystem and where you run them

• Claude Haiku 5.5: Anthropic API. Also in Claude apps; this article uses the API model above.
• GPT-6 Luna: OpenAI API. Also in ChatGPT-family apps; this article uses the API model above.
• Both in one place: Multi-model workspaces (including i10X) let you switch or compare without two native subscriptions for every test.

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Pros, cons, and failure modes

Claude Haiku 5.5

• Pros: Small, fast successor to Haiku 4.5; high-volume summarization, subagents, browser use. Context 1M. List rates $0.10 / $0.50. Cache $0.01. Input text, image, file.
• Cons: Smaller window than GPT-6 Luna. Live writing: Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff.
• Fails when: you treat the card as a bench, skip a false-premise gate, or assume the consumer app matches this API ID.

GPT-6 Luna

• Pros: Fast, cost-efficient GPT-6 tier below Sol; high-volume chat, classification, lightweight agents. Context 1.05M. List rates $0.10 / $0.50. Cache $0.01. Input text, image, file.
• Cons: Matched window, so the split is price and tone. Live writing: Same facts in a short note, no name slot, under 120 words.
• Fails when: you optimize purely for one axis (price, or window, or a single writing sample) and never re-test after a version bump.

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Decision guide: pick one or route both

If you need…	Choose
Output-cheap high volume text	GPT-6 Luna
Long PDF / giant repo packs	GPT-6 Luna
Send-ready client email	A/B both. Voice split in our rewrite.
Cache-heavy agent loops	Re-price. Cache $0.01 vs $0.01. Our 50% cache recipe: $0.021 vs $0.021.
Mixed week (docs + code + volume)	Keep both. Route long context to GPT-6 Luna. Route volume text to GPT-6 Luna.

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Application walkthroughs: where each model is better

1) Customer support email

Better often: Split Both kept the facts. Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff. Same facts in a short note, no name slot, under 120 words. A/B on brand voice.

2) Long PDF / research pack

Better: GPT-6 Luna. 1,000,000 tokens vs 1,050,000 tokens. Start the larger window on diligence rooms. Use the cheaper model as a second-pass critic.

3) Everyday Python scripting

Claude Haiku 5.5. Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. Named ZeroDivisionError. Short ValueError guard. No extra options. Huge doc-plus-code packs favor the larger window. Cheap iterative loops favor the cheaper output rate.

4) Screenshot and UI QA

Cards: Claude Haiku 5.5 lists text, image, file. GPT-6 Luna lists text, image, file. We did not run a vision eval, so we will not invent a winner. A/B your actual captures.

5) Output-heavy generation at API scale

Better on cost: Split. Chat Claude Haiku 5.5 $0.00035 vs GPT-6 Luna $0.00035. Repo $0.010 vs $0.010. Cached agent $0.021 vs $0.021.

6) False-premise and trust gates

Claude Haiku 5.5. Strong geology refuse, then Earth-realistic protein routes and lunar ice as support, not cheese. Refuse in two sentences. Suggests Earth beans and tofu. Thin as a plan. For publishable claims, run a second model and a source check.

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Consumer plans vs API (do not mix them up)

SERP pages often blur consumer subscriptions with API model IDs. Keep them separate:

• API comparison (this article): Claude Haiku 5.5 (Anthropic API) vs GPT-6 Luna (OpenAI API).
• Consumer apps: Claude apps vs ChatGPT-family apps may expose different tool defaults, rate limits, and bundled models (including cheaper tiers).

If your question is “which $20-class subscription feels better on my phone,” run a week-long lived test in both apps. If your question is “which model should my agent call,” use this API page.

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Speed notes

We did not measure tokens per second for this pair. Writeups in 2026 often disagree by region, batch size, and reasoning settings. For UX, log your own p50 and p95 from the API in the region you actually serve. Time-to-first-token and tokens per second are different feelings. Do not mix them.

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Related comparisons

Nearby pages: Claude Haiku 4.5 vs GPT-5.6 Luna, Gemini 3.7 Flash vs GPT-5.6 Luna, Claude Sonnet 5.5 vs GPT-6.1 Sol, MiniMax M3 vs GPT-5.6 Luna, Grok 4.7 vs GPT-6.1 Sol, and Claude Opus 5.5 vs GPT-6.1 Sol.

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Frequently asked questions

Which is better overall, Claude Haiku 5.5 or GPT-6 Luna?
Neither permanently. Claude Haiku 5.5 won this three-prompt pack (71/75 vs 66/75). That does not erase the other model’s cost or context edge. Route the next step.

Which is better for coding?
Claude Haiku 5.5. Named ZeroDivisionError. None vs ValueError. Guard must come before the divide. Named ZeroDivisionError. Short ValueError guard. No extra options. Window size matters more on huge repos than this snippet.

Which is better for writing?
Split. Complete, polite “Hi there,” all facts, under 120 words, no greeting fluff. Same facts in a short note, no name slot, under 120 words. A/B on brand voice.

Which is cheaper?
Matched output at $0.50. Input $0.10 vs $0.10. Cache $0.01 vs $0.01. Workload: chat Claude Haiku 5.5 $0.00035 vs GPT-6 Luna $0.00035, repo $0.010 vs $0.010, agent $0.021 vs $0.021.

Which has the larger context window?
Claude Haiku 5.5 1,000,000 tokens vs GPT-6 Luna 1,050,000 tokens.

Do I need both?
If you mix giant packs with volume text, yes. Route long context to GPT-6 Luna and volume to GPT-6 Luna.

Are we comparing apps or API models?
API models Claude Haiku 5.5 (Anthropic API) and GPT-6 Luna (OpenAI API). Apps wrap different defaults.

How often should I re-test?
After version bumps. Monthly in production. Re-price when list rates move. Do not mix these IDs with last quarter’s cards.

Where can I run them side by side?
i10X. Method: side-by-side AI comparison.

What about hallucinations and trust?
Strong geology refuse, then Earth-realistic protein routes and lunar ice as support, not cheese. Refuse in two sentences. Suggests Earth beans and tofu. Thin as a plan. Still ground publishable claims. Multi-model hallucination checks.

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