# Opus 4.8 vs Sonnet 5 vs Haiku 4.5: Which Claude Model to Use (2026)
> A practical guide to choosing between Claude Opus 4.8, Sonnet 5, and Haiku 4.5 for professional work in 2026 — plus where Fable 5 fits. With profession-specific recommendations for the most common workflows.
**Author:** [Alex Lowe](https://theaicareerlab.com/about) — Founder, The AI Career Lab
**Published:** 2026-05-20
**Updated:** 2026-07-03
**Last reviewed:** 2026-07-03
**Canonical URL:** https://theaicareerlab.com/blog/which-claude-model-should-you-use
**Category:** guide
**Tags:** Claude, Claude Opus 4.8, Claude Sonnet 5, Claude Haiku 4.5, Claude Fable 5, model selection, 2026
---> **TL;DR.** Sonnet 5 (launched June 30, 2026) is now the default Claude model and the right choice for most professional work — it matches Opus 4.8 on most knowledge-work tasks at lower cost. Pick Opus 4.8 for the hardest code and long agentic chains, Haiku 4.5 for speed and scale, and Fable 5 (restored July 1) when you want the most capable generally available model and your plan's Fable usage covers it.

Anthropic's current generally-available lineup as of July 2026: **Sonnet 5** (the new default), **Opus 4.8**, **Haiku 4.5**, and — restored on July 1 after a 19-day government-ordered suspension — **Fable 5**, a Mythos-class model that sits above the Opus tier (see our [Claude Fable 5 explainer](/blog/claude-fable-5-for-professionals) for the restoration story and its credits-based billing). The three workhorse tiers share a common feature surface (text + image input, vision, tool use, Skills, Projects) but differ meaningfully on capability, speed, cost, and context window. Picking the right one for the right task is still the highest-leverage tooling decision most professionals make in 2026 — but Sonnet 5 just made the default answer much better.

This guide does the translation. Specs cited come from [Anthropic's model documentation](https://platform.claude.com/docs/en/about-claude/models/overview) as of July 2026.

## The three workhorse models at a glance

| | **Opus 4.8** | **Sonnet 5** | **Haiku 4.5** |
|---|---|---|---|
| **Position** | Strongest on hard code + agentic chains | The default; matches Opus on most knowledge work | Fastest; near-frontier intelligence |
| **API ID** | `claude-opus-4-8` | `claude-sonnet-5` | `claude-haiku-4-5-20251001` |
| **Context window** | 1M tokens | 1M tokens | 200K tokens |
| **Max output** | 128K tokens | 128K tokens | 64K tokens |
| **Pricing (API)** | $5/M input, $25/M output | $2/$10 intro through Aug 31, 2026 — then $3/$15 | $1/M input, $5/M output |
| **Latency** | Moderate | Fast | Fastest |
| **Thinking** | Adaptive, effort-controlled | Adaptive, effort-controlled (no manual extended-thinking mode) | Extended thinking (manual) |
| **Reliable knowledge cutoff** | Jan 2026 | Jan 2026 | Feb 2025 |

The big structural change with Sonnet 5: it adopts the same **effort-controlled adaptive thinking** as Opus 4.8 (`low` / `medium` / `high` / `xhigh` / `max`, defaulting to `high`). The old Sonnet 4.6-era "Extended vs Adaptive thinking" distinction is gone — manual extended thinking isn't supported on Sonnet 5 at all.

## The single most important question: are you on claude.ai or the API?

**If you're on claude.ai** (the consumer/team chat product), Sonnet 5 has been the default for Free and Pro users since July 1, 2026 — and for the first time, the default is genuinely the right model for most professional work. Pro ($17/mo annual or $20/mo monthly) and above get the full picker. Switch freely as the task changes — there's no per-token cost to you, just usage limits per plan.

**If you're using the API** (or Claude Code, which uses the API tier you're on), each request costs by token. Sonnet 5's introductory pricing ($2/$10 through August 31, 2026) makes it the obvious default there too — with one caveat: its updated tokenizer produces 1.0–1.35x more tokens for the same content than Sonnet 4.6 did, so real-world costs run slightly higher than the headline rate suggests.

If you just want one default: **leave it on Sonnet 5**. The rest of this guide is about the exceptions.

## Pick Sonnet 5 for: almost everything (it's the default for a reason)

Sonnet 5 collapsed most of the old "when to pay for Opus" calculus. On real-world knowledge-work benchmarks it now edges out Opus 4.8 (GDPval-AA v2: 1,618 vs 1,615), and it leads on computer-use tasks (OSWorld-Verified: 81.2%). In practice that means:

- **Client / borrower / customer communication** — the daily back-and-forth, at speed
- **Long-form structured documents** — memos, disclosure drafts, PRDs, case analyses. This used to be Opus territory; Sonnet 5 handles most of it at or above Opus quality
- **Long-document analysis** — full case files, medical histories, board packages, policy documents. 1M context, same as Opus
- **Multi-step workflows** — Sonnet 5's agentic improvements are the headline of the release; most chained workflows no longer need Opus
- **Iteration and polishing** — fast enough to think alongside you

### Profession-specific Sonnet 5 wins

- **Loan officers** running the four-audience pipeline update workflow daily across 8+ active loans
- **Real estate agents** generating listing descriptions, client emails, CMAs, market updates
- **Attorneys and paralegals** drafting memos and summaries from full source documents — verify the hardest analyses on Opus if the stakes demand it
- **Copywriters** and **community managers** doing iteration-heavy, voice-sensitive work
- **Most healthcare clinicians** drafting SOAP notes, treatment plans, patient education
- **Management consultants** synthesizing meeting notes into strategy memos
- **AI product managers** structuring specs and rollout plans

## Pick Opus 4.8 for: the hardest code and the longest agentic chains

Opus 4.8 is no longer the automatic "quality matters" choice — Sonnet 5 took most of that ground. Where Opus still clearly earns its 2.5x price:

- **Complex software engineering** — Opus 4.8 leads Sonnet 5 meaningfully on SWE-bench Pro (69.2% vs 63.2%). For hard multi-file work in Claude Code, Opus is still the model
- **The longest multi-step agentic workflows** — compliance automation, data-extraction pipelines, anything that chains dozens of steps where a single early error compounds
- **Second opinions on high-stakes deliverables** — when the document goes to a regulator, court, or board and you want the strongest classic-tier model to draft or check it

Two practical notes. First, **Fast mode** costs $10/M input and $50/M output — much cheaper than it was on Opus 4.6/4.7 — so Opus depth with low latency carries a smaller premium. Second, the `effort` parameter **defaults to `high`**; set it lower for faster, cheaper responses on simpler work.

### Profession-specific Opus 4.8 wins

- **Data scientists and technical operators** running hard multi-step pipelines in Claude Code
- **Healthcare compliance officers** running QSR gap audits across full DHF documents where miss-cost is extreme
- **AI compliance officers** producing pre-legal regulatory screens across EU AI Act tiers + Annex III + US state overlays
- **ESG sustainability analysts** mapping KPIs to multiple frameworks from a 200-page sustainability report

## Pick Haiku 4.5 for: speed and scale

Haiku 4.5 is the fastest current Claude model and the cheapest. It's also more capable than people expect — "near-frontier intelligence" per Anthropic's framing. The places it earns its place:

- **High-volume classification or extraction tasks** — running over thousands of inputs per day
- **Real-time chat surfaces** — when the response needs to feel instantaneous (in-product chatbots, customer support assistants)
- **Background AI features inside production applications** — the AI that runs invisibly behind a feature, where latency directly affects user experience
- **Cost-sensitive workflows where Sonnet's depth isn't worth the price** — at $1/$5, Haiku is the cheapest current model even against Sonnet 5's intro pricing

Haiku's constraints to know:
- **200K context window**, not 1M. Long documents need chunking
- **Manual extended thinking only** — no effort-controlled adaptive thinking
- **Reliable knowledge cutoff is Feb 2025** — older than Sonnet 5 and Opus (both Jan 2026). For questions about events in 2025 or 2026, Haiku may have stale knowledge

### Profession-specific Haiku 4.5 wins

- **Customer support functions** building in-product AI chat where latency matters
- **Recruiters / HR** running high-volume resume classification or initial screening (with appropriate human-in-the-loop and EEOC-aware guardrails — see our [recruiter audit guide](/blog/ai-for-recruiters-guide))
- **Sales teams** generating high-volume personalized outreach where the template is the value-add and depth matters less
- **Internal tooling** — Slack bots, internal knowledge search, the AI behind ops dashboards
- **Real-time content moderation** in community management workflows

## Where does Fable 5 fit?

Fable 5 — restored globally on July 1, 2026 after a 19-day suspension — is a **Mythos-class** model that sits above the Opus tier entirely (SWE-bench Pro: 80.3% vs Opus 4.8's 69.2%). It is the most capable Claude model generally available. The catch is billing: through July 7 it's included for up to 50% of weekly usage limits on Pro, Max, Team, and select Enterprise plans; after that it moves to credits-based billing, and API use requires accepting a 30-day data-retention term for safety monitoring.

Practical rule: treat Fable 5 as the escalation above Opus 4.8 — the model for the sessions where capability is worth paying for separately. For the full restoration story, billing tiers, and the data-retention caveat, see our [Claude Fable 5 explainer](/blog/claude-fable-5-for-professionals).

## The decision tree

If you only remember one decision rule, use this:

1. **Is it everyday professional work — drafting, analysis, client comms, documents, most workflows?** → **Sonnet 5**. The default is now the right answer
2. **Is it genuinely hard code, or a long agentic chain where early errors compound?** → **Opus 4.8**
3. **Is latency the user-facing experience, or is this running at thousands-per-day volume?** → **Haiku 4.5**
4. **Is this the rare session where you want the most capable model available and your plan's Fable usage (or credits) covers it?** → **Fable 5**

## When to switch mid-conversation

On claude.ai you can switch models mid-conversation. The pattern that works for serious work in the Sonnet 5 era:

- **Stay in Sonnet 5** for thinking, drafting, iterating — and, unlike the Sonnet 4.6 days, for most final deliverables too
- **Switch to Opus 4.8** when you hit genuinely hard code or a long multi-step agentic task
- **Switch to Fable 5** for the occasional session where maximum capability is worth it and your plan allows

The old discipline — "draft in Sonnet, finish in Opus" — is mostly obsolete. Sonnet 5's knowledge-work quality means the finish-in-Opus step now only pays for itself on the hardest technical work.

## Effort levels: how Opus 4.8 and Sonnet 5 tune depth

Both Opus 4.8 and Sonnet 5 take an `effort` parameter that controls how much the model deliberates before answering — `low`, `medium`, `high` (the default), `xhigh`, and `max`. Lowering it trades depth for speed and cost; `xhigh` suits long-running agentic and coding sessions.

The question that used to come up constantly — "Opus on low effort vs Sonnet on high?" — has a cleaner answer now:

- **For knowledge work**, Sonnet 5 at default effort is simply the right tool. It benchmarks at Opus level and costs less.
- **For hard code and long agentic chains**, Opus 4.8 wins on base capability — use it at `high` (or drop to `medium` when you want most of the quality at lower latency).
- **Rule of thumb:** pick the model by the task's *type* (knowledge work → Sonnet 5; hard technical work → Opus 4.8), then use `effort` to tune speed and cost within that model.

(Haiku 4.5 is the exception: it exposes manual Extended Thinking, which you invoke explicitly, rather than effort-controlled adaptive thinking.)

## What about the legacy models?

Anthropic still publishes documentation for Sonnet 4.6, Opus 4.7, Opus 4.6, Sonnet 4.5, Opus 4.5, Opus 4.1, and the original Claude 4 models. **Claude Sonnet 4 (`claude-sonnet-4-20250514`) and Claude Opus 4 (`claude-opus-4-20250514`) are deprecated and retired as of June 15, 2026.**

**Sonnet 4.6 is now a legacy model.** If your integration pins `claude-sonnet-4-6`, update it to `claude-sonnet-5` — you get a better model at (through August 31) a lower rate, with the tokenizer caveat above. The other legacy models remain available but are not recommended for new integrations. If you're on Opus 4.7, moving to Opus 4.8 is a same-price upgrade ($5/M input, $25/M output).

## How API model versioning works

One subtle change starting with Claude 4.6: model IDs are pinned snapshots, not evergreen pointers. `claude-sonnet-5` won't auto-upgrade when Anthropic ships the next Sonnet — it stays on this snapshot, exactly as `claude-sonnet-4-6` stayed put when Sonnet 5 launched. This is a real change from earlier versioning patterns where some aliases moved.

For production integrations, this is the right behavior: you don't want your model silently changing under you. For staying current, it means actively migrating model strings when new versions ship — as everyone pinned to `claude-sonnet-4-6` should be doing right now.

## Pricing context

Per-token pricing as of July 2026 from [Anthropic's documentation](https://platform.claude.com/docs/en/about-claude/pricing):

- **Opus 4.8:** $5/M input, $25/M output (Fast mode: $10/$50)
- **Sonnet 5:** introductory $2/M input, $10/M output through August 31, 2026; standard $3/$15 from September 1. Updated tokenizer produces 1.0–1.35x more tokens for the same content vs Sonnet 4.6
- **Haiku 4.5:** $1/M input, $5/M output

For most professionals working through claude.ai rather than the API, per-token pricing is academic — usage limits are per-plan, not per-token. But if you're using Claude Code (which uses your API tier), or you're integrating Claude into your own product, the per-token pricing is where the per-model cost calculus lives.

[Anthropic's pricing page](https://claude.com/pricing) has the current consumer plan details. Verify before committing to a plan.

## Bottom line

Leave claude.ai on Sonnet 5 — the default is finally the right answer for most professional work. Reach for Opus 4.8 when the task is genuinely hard code or a long agentic chain, Haiku 4.5 when speed or volume is the point, and Fable 5 for the rare session where maximum capability justifies its separate billing.

The era of "just use Opus for everything" is over — Sonnet 5 matches it on most knowledge work at a fraction of the cost. Pick the model for the task, not the task for the model.

For the deeper dive on the top of the lineup, see our [Claude Fable 5 explainer](/blog/claude-fable-5-for-professionals) and the [Claude Sonnet 5 launch write-up](/blog/claude-sonnet-5-for-professionals-2026). For Claude vs ChatGPT, see our [profession-specific comparison hub](/compare).

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*This article cites model specifications as published in [Anthropic's model documentation](https://platform.claude.com/docs/en/about-claude/models/overview) and pricing as published at [claude.com/pricing](https://claude.com/pricing) as of July 2026. Anthropic updates model availability, capabilities, and pricing frequently. Verify current state before procurement or integration decisions.*
## Frequently asked questions

### Is Opus 4.8 better than Sonnet 5?

It depends on the task — and as of Sonnet 5 (June 30, 2026), the honest answer is "less often than you'd think." Sonnet 5 matches or beats Opus 4.8 on real-world knowledge-work benchmarks (GDPval-AA v2: 1,618 vs 1,615) while costing less per token. Opus 4.8 still leads on complex software engineering (SWE-bench Pro: 69.2% vs 63.2%) and the hardest multi-step agentic work. Default to Sonnet 5; reach for Opus 4.8 when the task is genuinely hard code or a long agentic chain.

### What is the difference between Opus 4.8, Sonnet 5, and Haiku 4.5?

Opus 4.8 is the most capable of the classic line (1M-token context, best for the hardest code and agentic work). Sonnet 5 is the new default workhorse (1M context, 128K output, matches Opus on most knowledge work, cheaper). Haiku 4.5 is the fastest and cheapest (200K context, best for high-volume and real-time tasks). API pricing per million input/output tokens: Opus $5/$25, Sonnet 5 $2/$10 intro through Aug 31 2026 (then $3/$15), Haiku $1/$5.

### Do I still need to switch models on claude.ai?

Much less than before. Since July 1, 2026, Sonnet 5 is the default for Free and Pro users, and it handles most professional work — including a lot of what used to need Opus. Switch to Opus 4.8 for the hardest coding and long agentic sessions, or to Fable 5 (restored July 1) when you want the most capable generally available model and your plan's Fable usage allows it.

### Which Claude model should I use on claude.ai?

Leave the model on Sonnet 5 — it's the default for a reason. Switch to Opus 4.8 for genuinely hard code or long multi-step agentic work. Pro ($20/month, or $17/month billed annually) and above unlock the full picker, and there is no per-token cost on claude.ai — just per-plan usage limits — so switching costs you nothing when the task warrants it.

### How much does each Claude model cost?

API pricing as of July 2026: Opus 4.8 — $5/M input, $25/M output (Fast mode $10/$50); Sonnet 5 — introductory $2/M input, $10/M output through August 31, 2026, then $3/$15 (note: Sonnet 5's updated tokenizer produces 1.0–1.35x more tokens for the same content); Haiku 4.5 — $1/M input, $5/M output. On claude.ai you pay per plan, not per token: Free (Sonnet 5 plus limited Haiku), Pro $20/month ($17 annual), Max $100–$200/month, Team $25–$125/seat, Enterprise custom.

### What happened to Claude Fable 5 — can I use it now?

Yes. Fable 5 launched June 9, 2026, was suspended June 12 under a US government export-control directive, and was restored globally on July 1. Through July 7 it's included for up to 50% of weekly usage limits on Pro, Max, Team, and select Enterprise plans; after July 7 it moves to credits-based billing. It's Anthropic's most capable generally available model — a Mythos-class tier above Opus. See our Fable 5 explainer for the full story and billing details.

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