Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Fable 5
96
GPT-5.5 Pro
100
Verified leaderboard positions: Claude Fable 5 #2 · GPT-5.5 Pro unranked
Pick GPT-5.5 Pro if you want the stronger benchmark profile. Claude Fable 5 only becomes the better choice if knowledge is the priority or you want the cheaper token bill.
Agentic
+4.9 difference
Knowledge
+17.6 difference
Claude Fable 5
GPT-5.5 Pro
$10 / $50
$30 / $180
N/A
N/A
N/A
N/A
1M+
1M
Pick GPT-5.5 Pro if you want the stronger benchmark profile. Claude Fable 5 only becomes the better choice if knowledge is the priority or you want the cheaper token bill.
GPT-5.5 Pro is clearly ahead on the provisional aggregate, 100 to 96. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5 Pro's sharpest advantage is in agentic, where it averages 90.1 against 85.2. The single biggest benchmark swing on the page is HLE, 64.5% to 57.2%. Claude Fable 5 does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $10.00 input / $50.00 output per 1M tokens for Claude Fable 5. That is roughly 3.6x on output cost alone. Claude Fable 5 gives you the larger context window at 1M+, compared with 1M for GPT-5.5 Pro.
GPT-5.5 Pro is ahead on BenchLM's provisional leaderboard, 100 to 96. The biggest single separator in this matchup is HLE, where the scores are 64.5% and 57.2%.
Claude Fable 5 has the edge for knowledge tasks in this comparison, averaging 74.8 versus 57.2. Inside this category, HLE w/o tools is the benchmark that creates the most daylight between them.
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 85.2. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
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