Best model for Claude Code
Choose Sonnet 5 for daily coding, escalate complex work to Opus 5, use Haiku 4.5 for narrow support tasks, and reserve Fable 5 for problems the others cannot finish.
The best model for Claude Code is Claude Sonnet 5 for most daily repository work. It combines fast responses, a native 1-million-token context window, and lower token prices than Opus or Fable. Move to Claude Opus 5 when the task is ambiguous, architectural, or expensive to get wrong. Use Claude Haiku 4.5 for narrow, well-specified support work, and reserve Claude Fable 5 for the hardest long-running investigations.
That is a starting policy, not a universal leaderboard. The right answer depends on both the task and the effort level. A more capable model can know more; higher effort makes the selected model read, act, and verify more before it returns.
Fact-checked August 2, 2026. This guide uses Anthropic's current model, Claude Code configuration, cost, and subagent documentation plus OmniaKey's live catalog. We did not run a controlled four-model benchmark, so the recommendations below are a reproducible routing policy rather than a claim that one model wins every repository.
Best model for Claude Code at a glance
| Model | Best use in Claude Code | Context | Anthropic input / output | OmniaKey input / output |
|---|---|---|---|---|
| Claude Sonnet 5 | Daily coding, feature work, routine debugging, most subagents | 1M | $2 / $10 introductory; then $3 / $15 | $0.60 / $3 |
| Claude Opus 5 | Architecture, subtle bugs, broad refactors, high-cost failures | 1M | $5 / $25 | $1 / $5 |
| Claude Fable 5 | The hardest and longest autonomous work | 1M | $10 / $50 | $2 / $10 |
| Claude Haiku 4.5 | Fast searches, classification, summaries, small mechanical tasks | 200K | $1 / $5 | $0.20 / $1 |
Prices are USD per million input and output tokens, before prompt-cache or tool charges. Anthropic's Sonnet 5 introductory rate ends August 31, 2026; its standard rate begins September 1. OmniaKey rates are the listed gateway rates checked on the fact-check date, not Anthropic subscription-plan allowances. Confirm current rates on the model catalog before budgeting production work.
If you want one rule to start today, use Sonnet 5 as the default and escalate by task. The best model is the cheapest one that reliably produces an accepted change, not the one with the largest benchmark number.
Why Sonnet 5 is the best default for most users
Anthropic describes Sonnet 5 as its best combination of speed and intelligence, and Claude Code's own cost guidance says Sonnet handles most coding tasks well while costing less than Opus. It is the sensible default for work such as:
- implementing a scoped feature with clear acceptance criteria;
- tracing a familiar error through a few files;
- writing or updating tests alongside a local change;
- reviewing a focused pull request;
- translating a known design into code;
- coordinating ordinary repository research through subagents.
Sonnet 5 also has a native 1M context window, so choosing it no longer means giving up the long context available on current Opus and Fable models. Context capacity is not the same as capability, however. A million tokens can hold more evidence; it does not guarantee that the model will identify the right architecture or subtle failure mode.
Use the exact OmniaKey model ID when you want a pinned result:
/model claude-sonnet-5
Claude model aliases can change as providers update their recommended versions. Current dateless Claude 5 IDs are pinned snapshots, so an exact ID makes an evaluation reproducible.
When Claude Opus 5 is worth the higher price
Choose Claude Opus 5 when the expensive part of the task is reasoning rather than typing. Typical signals include:
- the bug crosses several services and the obvious explanation is wrong;
- the repository is unfamiliar and the request leaves important choices open;
- an architecture or migration decision will be costly to reverse;
- a broad refactor must preserve implicit behavior across many files;
- security, billing, or data-integrity mistakes have a high correction cost;
- Sonnet has all relevant context, clearly tried, and is still confidently wrong.
Opus 5 costs more per token, but per-token price is not completed-task cost. On difficult work, a stronger model may reach an accepted result in fewer failed loops and with less human correction. On a precise one-file edit, that advantage may never have a chance to appear.
Start Opus 5 explicitly with:
/model claude-opus-5
For the model's published evidence, effort behavior, migration notes, and limits, read the Claude Opus 5 review. This article keeps the narrower question of choosing a model inside Claude Code.
When Fable 5 earns its premium
Claude Fable 5 is Anthropic's most capable widely released model and the Claude Code documentation positions it for tasks larger than a single sitting. It investigates before acting, sustains long autonomous sessions, and verifies more readily than smaller models.
That makes Fable a specialist rather than the routine default. Test it when:
- a root-cause investigation remains unresolved after a careful Opus attempt;
- the work is unusually long, ambiguous, and tool-heavy;
- an outage or architecture problem rewards deeper independent investigation;
- your fixed evaluation set shows Fable completing tasks the cheaper models cannot.
Do not pay the Fable rate merely because a task has many files. Clear scope, focused context, and a good plan often matter more than model size. Fable is valuable when the problem itself stretches the other models, not when the prompt is underspecified.
/model claude-fable-5
Fable 5 requires Claude Code v2.1.170 or later. Its picker entry can also depend on provider or organization availability, while a gateway can expose a configured custom model option.
Where Haiku 4.5 fits
Claude Haiku 4.5 is the fastest current model in this comparison and has a 200K context window. It is a good fit when the task is narrow, the success condition is explicit, and a mistake is cheap to catch:
- locating files or symbols before the main agent starts;
- summarizing bounded logs or test output;
- classifying issues into a known taxonomy;
- making repetitive edits with a deterministic test;
- answering focused questions about code already in context.
Haiku is not the economical choice if a small mistake causes several expensive retries. Escalate when it misses relationships across files, misunderstands an unfamiliar domain, or needs repeated correction.
For a dedicated lightweight subagent, set the model in its frontmatter:
---
name: quick-researcher
description: Finds files and summarizes evidence for a scoped repository question
model: haiku
---
Claude Code subagents inherit the main model when model is omitted. Pinning haiku for bounded research prevents every delegated lookup from paying the main session's Opus or Fable rate. For ordinary implementation or review subagents, Sonnet is the safer starting point.
Model versus effort: change the right control
Model selection and effort solve different failures.
Change the model when the problem is too hard. If Claude has the relevant files, tools, and instructions, explores the task properly, and still reaches the wrong conclusion, move from Haiku to Sonnet, Sonnet to Opus, or Opus to Fable.
Raise effort when Claude did not try hard enough. If it skipped a relevant file, stopped halfway through a refactor, failed to run the tests, or returned before checking its work, a higher effort level may fix the behavior without changing models.
Fix the context before either. A vague request, stale CLAUDE.md, missing documentation, or unavailable tool cannot be repaired reliably by spending more tokens. First make the success condition and evidence available.
Anthropic recommends starting with each model's default effort. Claude Code's /effort control changes not only thinking time but also how many files the model reads, which tools it uses, and how thoroughly it verifies. Higher effort can therefore improve completion, but it can also increase latency and output-token cost.
A practical routing policy
Use task boundaries instead of switching models every few turns:
- Start routine feature and maintenance work on Sonnet 5 at its default effort.
- Keep Haiku 4.5 for small, isolated subagents with deterministic output.
- Escalate to Opus 5 when ambiguity, architectural scope, or failure cost rises.
- Use Fable 5 only after a hard task or your evaluation set justifies the premium.
- Drop back to Sonnet when the difficult decision is resolved and execution becomes mechanical.
Switching models inside a long conversation makes the next response re-read the full history without cached context. That turn can be slower and more expensive, so switch at a clean task boundary when possible. For unrelated work, /clear is often cheaper than carrying an old session into a new model.
Claude Code also provides opusplan, which uses Opus during plan mode and Sonnet for execution. It is a useful built-in version of this routing idea, but the exact versions behind aliases depend on the provider and any gateway mappings. Use exact model IDs when version reproducibility matters.
Compare models on accepted changes, not impressions
A fair local evaluation needs the same repository state, prompt, tools, permissions, and acceptance test for every model. Build a small set that represents your actual work:
| Task class | Example | What to measure |
|---|---|---|
| Routine edit | Add a validated field and tests | Pass rate, latency, correction time |
| Debugging | Reproduce and fix a subtle regression | Root cause, retries, tests run |
| Refactor | Change an interface across packages | Missed call sites, build result |
| Review | Inspect a known defective change | Useful recall, false positives |
| Architecture | Propose a reversible migration | Constraint coverage, decision quality |
| Subagent | Search and summarize bounded evidence | Accuracy, tokens, response time |
Run each task more than once because agent results vary. Record accepted outcome, human correction minutes, elapsed time, input tokens, cache tokens, output tokens, and tool calls. A model that costs twice as much per token can still be cheaper per accepted change; a cheap model that passes the same test is the better choice for that class.
Do not mix model and effort changes in the same first comparison. Hold effort at the default while comparing models, then sweep effort on the model you intend to deploy. Otherwise you cannot tell whether capability or thoroughness caused the result.
How to switch models on OmniaKey
The setup itself belongs in the Claude Code setup guide. Once the Anthropic-compatible endpoint is configured, use /model with an exact supported ID:
/model claude-haiku-4-5
/model claude-sonnet-5
/model claude-opus-5
/model claude-fable-5
Update Claude Code if a current model is missing: Sonnet 5 requires v2.1.197 or later, Opus 5 requires v2.1.219 or later, and Fable 5 requires v2.1.170 or later. Run claude update, then reopen the model picker.
OmniaKey routes the requested model without silently substituting, quantizing, or distilling it. Availability can still change, and an unavailable model returns an error rather than an undisclosed fallback. Check the live model catalog before relying on a model in automation.
Claude Code is designed for Claude models. If the decision is Claude versus GPT or Gemini, choose an agent that supports the required protocol rather than trying to force a non-Claude model through Claude Code. The coding-model family comparison covers that broader question, while Claude Code vs Codex compares the agent products.
Final recommendation
For most developers, Claude Sonnet 5 is the best model for Claude Code as a daily default. It is fast, capable, less expensive than Opus or Fable, and large enough in context for long repository sessions. Use Opus 5 for ambiguous reasoning and costly mistakes, Haiku 4.5 for bounded support tasks, and Fable 5 for the rare problems that remain out of reach after a serious Opus attempt.
Treat that as a routing baseline. Your own accepted-change data should decide where each threshold sits.
Frequently asked questions
What is the best model for Claude Code?
Claude Sonnet 5 is the best default for most daily coding. Claude Opus 5 is a better starting point for complex architecture, subtle debugging, and expensive failures. Fable 5 targets the hardest long-running tasks, while Haiku 4.5 is best reserved for simple, bounded work.
Is Opus better than Sonnet for Claude Code?
Opus is more capable on difficult and ambiguous work, but Sonnet is faster and cheaper for routine tasks. Evaluate cost per accepted change rather than assuming the larger model should handle every turn.
Should I use Fable 5 for every large repository?
No. Repository size alone does not justify Fable. Use focused context and Sonnet or Opus first, then test Fable when the problem is genuinely long, ambiguous, and beyond the cheaper models.
Which model should Claude Code subagents use?
Use Haiku for narrow searches, classification, or summaries with clear checks. Use Sonnet for implementation, review, and coordination. Let a subagent inherit Opus or Fable only when its own task needs that capability.
Does higher effort equal a better model?
No. The model controls the underlying capability; effort controls how thoroughly that model works on a turn. Upgrade the model when it tried and still could not solve the problem. Raise effort when it skipped investigation or verification.
Can Claude Code use GPT or Gemini models?
No. Anthropic documents Claude Code as designed for Claude models. Use Codex, Cursor, Cline, aider, or another compatible agent for GPT or Gemini.