[FEATURE] Allow combined Sonnet/Haiku usage similarly to opusplan

[mgelei]

Preflight Checklist

• I have searched existing requests and this feature hasn't been requested yet
• This is a single feature request (not multiple features)

Problem Statement

With the introduction of Haiku 4.5 it would be viable to use that for doing code changes based on planning executed by Sonnet. This currently requires manually switching between models, which is an extra step, can be forgotten, etc.

Proposed Solution

Introduce a new mode similar to what we had with opusplan, e.g. claude --model sonnetplan which would dynamically use Sonnet for planning and Haiku for editing

Alternative Solutions

A seemingly feasible workaround would be to override the default models via the env variables and switch to opusmode, but that's not available on the pro plan.

myUser@myMachine myFolder % export ANTHROPIC_DEFAULT_OPUS_MODEL=claude-sonnet-4-5
myUser@myMachine myFolder % export ANTHROPIC_DEFAULT_SONNET_MODEL=claude-haiku-4-5
myUser@myMachine myFolder % claude --model opusplan
Claude Pro users are not currently able to use Opus in Claude Code. The current model is now Sonnet.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

No response

Additional Context

No response

[github-actions]

Found 2 possible duplicate issues:

1. Bring back "opusplan", why did you remove it in v2.0.0? #8358
2. [Bug] Plan mode doesn't auto-switch between Sonnet 4.5 and Haiku 4.5 #9695

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[mgelei]

I'm not sure. The first mentioned ticket is not a duplicate, the second one seems related but that's a closed bug report, asking for a behavior that AFAIK doesn't exist. (And this ticket is about adding that behavior)

[acidtech]

2.0.22: Set /model to Haiku. Then switch to plan mode and model will change from Haiku to Sonnet. So it appears they already implemented what you wanted.

[mgelei]

That seems to contradict #9695 but I'll check tomorrow

[mgelei]

Yeah, that's not working.

[cassus]

Status: Feature is NOT implemented - only shows up in statusline JSON

The Haiku→Sonnet plan mode switching described in this feature request is not actually working. When Haiku 4.5 is set as default and plan mode is entered:

• The model responding is still Haiku 4.5 (verified via self-identification)
• Only the statusline JSON shows "Sonnet 4.5" -- but this is not true

This is a bug in the JSON, not a proper feature implementation. This feature seems to remain unimplemented as of this test of v2.0.32

[huyhandes]

Bump for this features. New sonnetplan mode should be added.

[km-anthropic]

Hi! Sometimes the model gets confused when it sees a different model string above. Instead I recommend clicking ctrl+O to deterministically find out what model was called. Here's a screenshot:

Although the model says it's haiku, you can see the sampled model is sonnet (this is in Plan Mode, where it's automatically set as a default). We're working to better improve the model's identification of itself though!

[cassus]

Wow, I didn't know about this, and I can confirm that it works as you described.

[km-anthropic]

No worries! It definitely is a bit confusing.

[huyhandes]

Hi! Sometimes the model gets confused when it sees a different model string above. Instead I recommend clicking ctrl+O to deterministically find out what model was called. Here's a screenshot:

Although the model says it's haiku, you can see the sampled model is sonnet (this is in Plan Mode, where it's automatically set as a default). We're working to better improve the model's identification of itself though!

So the workflow now is

claude --model haiku -> shift-tab to cycle to plan mode -> Let's go