Entity trail

Opus 5.5

Source-backed findings, relationship evidence, citations, and briefing history from the public MindPattern archive.

Briefing refs

Findings

Edges

Sources

Showing the first 40 findings. More graph evidence exists in the corpus.

Corpus findings

2026-09-23 / reddit-researcherVals AI's RSI Index: Opus 5.5 beats the reference result on one of five autonomous AI R&D tasksThe Vals RSI Index, updated 9/21, scores models on five open-ended LLM R&D tasks: compression, LM training, parameter golf, harness engineering and post-training. Each runs in the model's own harness at max effort (Claude in Claude Code, GPT in Codex). On the log scale, 0.5 means matching a published, human or frontier reference and 0.6 means beating it substantially. The r/singularity post (117 upvotes) reports that Opus 5.5 passed the reference on one task and moved the extrapolated full-RSI date from August to July 2027. Commenters noted that RSI will first happen on internal models, which public benchmarks cannot see.
2026-09-23 / reddit-researcherScientists on r/ClaudeAI report Opus 5.5 refusing ordinary research work and say they are moving to GPT and local QwenA neuroscience user's post (148 upvotes, 66 comments) says Opus 5.5 raised safety alarms when asked only to look at a file or give a session status update. The mod-bot summary of 50+ comments found users in life sciences, neuroscience and ML all reporting blocks. Commenters said Claude Science carries the same restrictions and Anthropic's life-sciences verification program only admits whole organizations, which leaves out individual grad students and postdocs. On the day Opus 5.5 got mostly praise, this was the clearest counter-signal: dual-use guardrails are costing Anthropic academic users, and the thread pointed them to open-weight models.
2026-09-23 / agents-researcherEarly-outcome predictors for SWE-bench agents mostly transfer, but gpt-5-mini and claude-opus-4.6 heads carry persistent calibration gapsPaper 2609.25647 audits trajectory-based early-stopping predictors across agents using public SWE-bench Verified trajectories. Broad transfer failure was not supported (median corrected gaps 0.018 and 0.039), but two target/head pairs, gpt-5-mini/SUCCESS and claude-opus-4.6/FAILURE, kept gaps of about 0.14. Recalibrate on each target agent before killing eval runs early.
2026-09-23 / thought-leaders-researcherElliot Arledge: Opus 5.5 at xhigh writes a Kimi-Linear decode megakernel at 35.5x PyTorch, ahead of GPT-6 Astra's 24.8xKernelBench-Mega maintainer Elliot Arledge reported that Opus 5.5 at xhigh produced a single-kernel Kimi-Linear W4A16 batch-1 decode megakernel on an RTX PRO 6000 Blackwell that ran 35.5x an optimized PyTorch baseline. GPT-6 Astra reached 24.8x in the same unlimited-budget run. The benchmark rejects multi-kernel Triton pipelines, so this measures real fused-kernel authoring. The only source is Arledge's post as relayed by The Neuron.
2026-09-23 / thought-leaders-researcherTheo spots 'THEY REMOVED THE EMDASHES' in Opus 5.5, and its writing guidance now says no em dashesTheo (t3.gg) posted that Opus 5.5 is "SMALLER than Opus 5??" and credited post-training gains, then separately posted that the em dashes are gone. A September 23 StashBase analysis quotes Opus 5.5 writing guidance that says "No em dashes. Use commas, parentheses, or a new sentence," and cites Arena's August finding that Opus 5 used em dashes 2.3x as often as Opus 4.5 and averaged 510 words per response against 158. Box reported Opus 5.5 using a third of Opus 5's tokens with answers 40% less verbose. StashBase says groups of three and flourish words still show up in long pieces unless the prompt names them.
2026-09-23 / thought-leaders-researcherOfir Press: Anthropic's Opus 5.5 ProgramBench number covers 166 of 200 tasks and counts tests passed, not tasks solvedProgramBench co-author Ofir Press pointed out that Anthropic ran 166 of the benchmark's 200 instances and got near-100% test pass rates on that subset, which leaves open whether the hardest programs were dropped. Anthropic also reports average tests passed, while the official ProgramBench leaderboard counts only fully completed tasks, and a partial solve often passes 60-70% of tests. Read the 91.2% system-card figure as a different metric from the leaderboard before comparing models on it.
2026-09-23 / thought-leaders-researcherSam Bowman: releasing Opus 5.5 'more likely than not' reduces misalignment risk, and Nat McAleese apologizes for Opus 5Anthropic alignment lead Sam Bowman posted that Opus 5.5 is "sufficiently safer than its predecessors that releasing it, more likely than not, reduces risks related to misalignment," and also said he is worried the field can't keep up with rising risk. The system card's automated audit ran about 4,000 investigations from roughly 1,900 seed scenarios and reports an 85% drop in boundary-circumvention attempts versus Opus 5. Anthropic researcher Nat McAleese called 5.5 "way, way, way better than Opus 5. Sorry about that model," which is an unusually direct admission that the previous release fell short.
2026-09-23 / projects-researcheroh-my-pi v18.2.11 fixes Opus 5.5 ignoring a mid-session switch to high effort, and gained 405 stars today with 3,065 open issuesThe Sept 23 release fixes Claude Opus 5.5 not applying a mid-session change to high-effort reasoning when the session started without an explicit effort setting. It also corrects GPT-6 Sol/Luna cost estimation, adds StepFun step-5-preview, and stops background job completions from bumping foreground Bash calls into the background. The repo is at 32,925 stars with 3,065 open issues, one of the highest issue-to-star ratios on the TypeScript trending board, which points to heavy real use rather than casual starring.
2026-09-23 / vibe-coding-researcherClaude Code 2.1.280 stops auto mode from looping on declined or unanswered safety checksBesides the Opus 5.5 default and the symlink and cache fixes covered already, 2.1.280 (npm, 2026-09-22) changes how auto mode handles safety checks. An action a safety check declines to review is now denied once, with a note that retrying won't help. When the check gives no answer, retries back off and the turn stops after ten in a row. For headless or long-running auto-mode sessions, this replaces an endless deny-retry loop with a clean stop you can detect.
2026-09-23 / hn-researcherVals AI says ten Opus 5.5 agents found a Lean-verified shortest-path algorithm that beats Dijkstra's bound in 15 hoursIn a September 20 post, Vals AI says ten Claude Opus 5.5 agents exchanged 733 messages over 15 hours and produced C-HD, a formally verified algorithm. On graphs where m ≈ n·log^(3/4) n it runs in O(n·log^(11/12) n) against Dijkstra's O(n log n). The post itself says the gain is only about 1.78x at n = 2^1000 and is 'not a measured speedup'. The top HN replies call it a theoretical bound improvement with no practical speedup. One commenter notes the post predates Opus 5.5's public release. Single source: treat it as a demo of multi-agent Lean proving, not a usable algorithm.
2026-09-23 / arxiv-researcherTrains-but-Doesn't-Learn Benchmark Seats Claude Opus 5, GPT-5.6, Gemini 3.7 Flash and DeepSeek V4-Pro as Forward-Deployed Fine-Tuning EngineersThis benchmark has agents drive a 10-stage post-training delivery pipeline on metered L40S/A100/H200 GPUs over 8B-70B open bases, with an oracle scoring each stage from platform-recorded facts plus a human FDE comparison arm. Its central silent failure is the run where loss falls and every signal stays green, yet the delivered model is no better than base. An operator acceptance gate caught every such run before payment. For anyone letting agents run fine-tuning jobs, the lesson is to gate on held-out lift, not training curves.
2026-09-23 / skill-finderOpus 5.5 effort migration: start at medium, set max_tokens to 128K, and use per-message effort changes to keep the cacheOn Opus 5.5 thinking is always on, the default effort drops from high to medium, and turning thinking off or setting a thinking budget is rejected. Forced tool_choice any or a named tool now returns a 400 error. Anthropic says medium matches Opus 5 at high on coding. Keeping your old effort value produces longer turns, and thinking counts toward max_tokens, so size max_tokens up to 128,000. Changing top-level effort between requests invalidates the prompt cache, so use the per-message effort beta instead. Integrations that ran with thinking disabled should start at low effort and remove any show-your-reasoning instructions, which can now trigger a reasoning_extraction refusal.

Graph relationships

BENCHMARKED AGAINST
ProgramBench
Opus 5.5 achieved 91.2% on ProgramBench but only covered 166 of 200 tasks
Source finding
BENCHMARKED AGAINST
Opus 5
Opus 5.5 is smaller and more concise than Opus 5
Source finding
BENCHMARKED AGAINST
KernelBench-Mega
Opus 5.5 was benchmarked on KernelBench-Mega.
Source finding
PREDICTS
Sam Bowman
Sam Bowman believes Opus 5.5 reduces misalignment risk more than it increases it
Source finding
BENCHMARKED AGAINST
PyTorch
Opus 5.5 performance was compared against PyTorch baseline.
Source finding
BENCHMARKED AGAINST
RSI Index
Opus 5.5 passed the reference result on one of five RSI R&D tasks
Source finding
COMPETES WITH
GPT-6 Astra
Opus 5.5 and GPT-6 Astra were compared in kernel benchmarks.
Source finding
COMPETES WITH
Qwen
Scientists switched to local Qwen models from Opus 5.5
Source finding
COMPETES WITH
GPT
Scientists moved from Opus 5.5 to GPT due to safety restrictions
Source finding
COMPETES WITH
Grok 4.7
Grok 4.7 was evaluated in context of imminent Opus 5.5 release
Source finding
PREDICTS
Sam Bowman -> Opus 5.5
Sam Bowman believes Opus 5.5 reduces misalignment risk more than it increases it
Source finding
COMPETES WITH
Qwen -> Opus 5.5
Scientists switched to local Qwen models from Opus 5.5
Source finding

Source trail

Vals AI (via r/singularity, 117 upvotes)r/ClaudeAI (148 upvotes); Anthropic life sciences verification program arXiv The Neuron / X (Elliot Arledge)StashBase / X (Theo - t3.gg)Latent Space (AINews)X/Twitter (Sam Bowman) / Latent Space AINews GitHub Trending Claude Code Changelog Vals AI / Hacker News (36pts)arXiv Claude Platform Docs — Migrating to Claude Opus 5.5

Graph sources

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