Model error diagnosis

Anthropic: Claude Opus 4.6 (Fast) | model capability unsupported

Anthropic: Claude Opus 4.6 (Fast) returning 400 / model capability unsupported means you should first confirm whether model ID anthropic/claude-opus-4.6-fast is visible for this Anthropic key, then separate permission, context, capability, rate limit, or route issues.

Model

anthropic/claude-opus-4.6-fast

Anthropic: Claude Opus 4.6 (Fast)

Provider

Anthropic

13 models in catalog

Error type

model capability unsupported

capability-unsupported

Status code

400

global model route

Model error summary

Model

anthropic/claude-opus-4.6-fast

Error type

capability-unsupported

Status code

400

Read-only check. Detection data burns after 5 minutes.

What this model error usually means

Anthropic: Claude Opus 4.6 (Fast) returning 400 / model capability unsupported means you should first confirm whether model ID anthropic/claude-opus-4.6-fast is visible for this Anthropic key, then separate permission, context, capability, rate limit, or route issues.

Model: anthropic/claude-opus-4.6-fast
Provider: Anthropic
Status code: 400

How to prove it during checking

Read-only check. Detection data burns after 5 minutes.

List models: confirm whether anthropic/claude-opus-4.6-fast is actually visible instead of guessing from the display name.
Light probe: use minimal input to verify whether Anthropic returns the same 400, then record the error body.
Compare model facts: context 1,000,000, input $30, output $150.
supports include_reasoning
supports max_tokens
supports reasoning
supports response_format

Next action

Anthropic: Claude Opus 4.6 (Fast) model capability unsupported should not end at failed. Return the next move: change model ID, add permission, reduce context, disable unsupported capability, change route, monitor, or hold listing.

Context: 1,000,000
Price: $30 / $150
Read-only check. Detection data burns after 5 minutes.

Open key checker

Read-only check. Detection data burns after 5 minutes.

Open models

Anthropic: Claude Opus 4.6 (Fast)

Open providers

Anthropic