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Source-tracked model comparison

Claude Fable 5 vs Claude Opus 4.8: which costs less for a practical API workload?

Compare verified pricing and model limits for migration and fallback planning across Anthropic premium tiers. The cost example uses a long-context research workload and does not assume equal model quality.

Direct cost answer: Claude Fable 5 is estimated at $3,230.00 per month and Claude Opus 4.8 at $1,615.00 for 150,000 input tokens, 5,000 output tokens, and 2,000 monthly requests. Claude Opus 4.8 is $1,615.00 lower under these assumptions. This does not identify a quality winner.
Same-provider comparisonLong-context researchSources checked 2026-09-08 / 2026-09-08
Pair-specific guidance

Fable 5 rollout with Opus 4.8 fallback

Anthropic documents Opus 4.8 as the permitted fallback target at launch for eligible Claude Fable 5 refusals. Treat this pair as a primary-and-fallback architecture decision as well as a price comparison.

Decision factorClaude Fable 5Claude Opus 4.8
Standard token price$10 input and $50 output per million tokens$5 input and $25 output per million tokens
Tracked limits1M context and 128k maximum output1M context and 128k maximum output
Fallback roleMay return an HTTP 200 response with stop_reason set to refusalDocumented launch fallback target for eligible Fable 5 refusals
StackLens assessment

Rollout checks for this pair

  • Instrument refusal and fallback-served events separately from HTTP error monitoring.
  • Replay representative long-running tasks on both models before changing the primary route.
  • Measure cost per completed task, including fallback attempts and generated output, rather than comparing list price alone.
Tracked facts

Pricing and model limits

Prices are USD per 1M tokens under each model's verified default profile.

FieldClaude Fable 5Claude Opus 4.8
API access providerAnthropicAnthropic
API model IDclaude-fable-5claude-opus-4-8
Input / 1M$10.00$5.00
Cached input / 1M$1.00$0.50
Output / 1M$50.00$25.00
Context window1,000,000 tokens1,000,000 tokens
Maximum output128,000 tokens128,000 tokens
Accepted inputtext, imagetext, image
Example workload

Long-context research cost scenario

150,000 input and 5,000 output tokens per request, 2,000 monthly requests, and 10% cached input.

Anthropic

Claude Fable 5

$3,230.00 / month
Input cost
$2,730.00
Output cost
$500.00
Per 1,000 calls
$1,615.00
Pricing profile
standard
View model details
Anthropic

Claude Opus 4.8

$1,615.00 / month
Input cost
$1,365.00
Output cost
$250.00
Per 1,000 calls
$807.50
Pricing profile
standard
View model details

Cost result: Claude Opus 4.8 is $1,615.00 lower per month for these assumptions. This is a price comparison, not a model-quality ranking.

Adjust this comparisonOpen workload calculator
StackLens assessment

Questions to answer before choosing

  • Which production tasks justify making Fable 5 the primary model instead of Opus 4.8?
  • Does every Fable 5 request path detect stop_reason refusal and invoke the intended fallback?
  • How do fallback frequency, cache credits, and output length change successful-task cost?
Workload caveat

What this estimate leaves out

Models whose tracked context window is below the scenario input are excluded from the compatible-model table.

Latency, reliability, output quality, retries, regional processing, and provider-specific tool charges can change the practical decision.

Continue comparing

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