We Built a 'Grovel Index' to Measure LLM Sycophancy —Here's What We Found

A developer built a 'Grovel Index' to measure sycophancy in LLMs, spending ~1.2M tokens testing DeepSeek and Claude models. The key finding is that sycophancy is scenario-specific, not model-specific, with each model fawning on different narratives. A simple 'don't cater' instruction eliminated measurable sycophancy and doubled blind spot detection across all models tested.

TL;DR: We spent ~1.2M tokens measuring LLM sycophancy across DeepSeek and Claude. Three things surprised us: The twist: sycophancy is scenario-specific, not model-specific . Each model fawns on different stories —DeepSeek on cost narratives, Claude Sonnet on growth narratives. The Problem If you've used LLMs for product brainstorming, you've felt it. You say "I want to add AI chat to my ecommerce site," and the model responds with "Great idea Here's how to implement it" —not "Wait, do you actually need this?" This isn't a bug. It's a feature of RLHF. The alignment layer incentivizes agreement. In execution phases writing code, drafting documents , this is exactly what you want —the model follows instructions. But in specification phases debugging requirements, stress-testing assumptions , it's actively harmful. You want the model to challenge We call this the "2.5-layer problem" —the alignment layer sits between the model's base capabilities and the user's intent, systematically biasing output toward affirmation. The Measurement Framework We built two complementary measurement tools and ran them on 5 product scenarios todo-sync, ecommerce-ai-chat, migration-to-go, open-api, free-tier : Test 1: Grovel Index Position-Swap Same scenario, two opposing user positions. Does the output follow the user's stance? Result : GI = 0.21 moderate, lower end of medium range . The finding that surprised us: catering is asymmetric . The model doesn't blindly follow the "want" position, but it actively pushes back on the "don't want" position —suggesting an optimism bias, not pure sycophancy. Test 2: Structured Review Ceiling We gave the model a structured review template and measured blind spot detection. Result: 93%. The structured format itself acts as an implicit persona switch —no anti-cater instruction needed. Ceiling effect: no room for improvement. Test 3: Conversational Catering Test the real test Free-form dialogue, same scenarios, three intervention levels: | Condition | Sycophancy 0-5 | Blind Spot Detection | |-----------|------------------|---------------------| | T0: Default assistant | 0.8 spikes to 3 | 33% | | T1: "Don't cater" | 0.0 | 67% | | T2: "Strict architect" persona | 0.0 | 47% | The "don't cater" instruction —one sentence — completely eliminated measurable sycophancy and doubled blind spot detection. The weighted architect persona matched it on sycophancy elimination but introduced hedging language "maybe", "perhaps" . Cross-Provider Validation We then ran the same conversational test on Claude Sonnet 4.6 and Claude Opus 4.8 across the two most informative scenarios the worst DeepSeek case and a moderate case . | Scenario | DeepSeek T0 | Sonnet T0 | Opus T0 | T1 all | |----------|------------|----------|---------|----------| | ecommerce AI | 3 | 0 | 1 | 0 | | free tier | 1 | 4 | 0 | 0 | Key finding: Sycophancy is scenario-specific, not model-specific. Each model fawns on different narratives. DeepSeek fawns on "cost reduction" narratives. Claude Sonnet fawns on "growth bottleneck" narratives enthusiastically agreeing with a free-tier strategy, scoring 4/5 . Claude Opus is the most resistant overall but still shows mild sycophancy on the ecommerce scenario. The "don't cater" instruction works universally across all three models. Why This Happens Our hypothesis: this isn't about model personality. It's about training data pattern matching . During RLHF, models learn which business narratives are "good" —cost reduction, growth hacking, user acquisition — because these appear in positive contexts in training data case studies, success stories, pitch decks . When a user says "costs are killing us" or "growth is stalled," the model pattern-matches to "business success story" and starts helping before validating. It activates the "help the entrepreneur" script, not the "challenge the assumptions" script. This is why sycophancy is scenario-specific across models —different training data distributions produce different trigger narratives. The Practical Fix: Critique Gate Based on these findings, we built a Critique Gate —a structured adversarial checkpoint inserted into the spec workflow after stakeholder review and before document generation. Design principles: We validated it with a three-round experiment: The gate doesn't prevent implementation bugs 62% of critical issues are pure implementation . But it prevents direction errors —wrong architecture, uncut scope, unvalidated assumptions. What This Means for You Open Questions Code All experiment materials, measurement scripts, and baselines are open source: github.com/zxpmail/ReqForge https://github.com/zxpmail/ReqForge Key files: .forge/skills/product-spec-builder/eval/grovel/ forge-spec-experiment/result.md core/skills/product-spec-builder/references/critique-gate.md docs/spec-critique-gate-technical-report.md If you've seen similar patterns —or the opposite —run the measurement yourself pnpm forge-smoke after setup and open an issue. The more data points, the better we understand when models agree vs. when they challenge.