What Changed: April 17, 2026

For readers who already went through the site. One entry per page, only what’s new. Skip the rest.

The big shifts this round: Layer 2 got rewritten, Opus 4.7 shipped with a silent repricing, and four academic papers put numbers on claims we’d been making from experience.

The three biggest changes

Layer 2 reformulation. “Personal Intent Language” is gone. It was aspirational placeholder that read well and wasn’t real. The replacement is Intent Form Selection: pick the form (NL, AGENTS.md, SKILL.md, DO/DO NOT, rules, hooks) that matches task complexity, reliability requirement, and horizon. Not a new language to invent. A decision tree for the forms that already exist. See index → Layer 2 and principles → open questions.

Opus 4.7 silent repricing (Apr 16). Nominal pricing unchanged at $5/$25. Real cost +33–50% on the same workload: new tokenizer inflates tokens 1.25–1.35×, budget_tokens silently reroutes to task_budget without erroring, xhigh is the new default, self-verification consumes +15% output tokens. Cache stays cold for 2–4 weeks post-migration. Reliable configs remain Opus 4.5-Nov HIGH and Sonnet 4.6 HIGH; Opus 4.7 is not yet on the reliable list. New landscape → Opus 4.7 and the silent repricing section.

Four papers landed in four weeks. Empirical numbers now exist for claims that used to be experiential:

Per-page deltas

index.md

• Layer 2 rewritten from “Personal Intent Language” to “Intent Form Selection.” Intent gap quantified: 32% of production LLM failures.
• KB stat updated: 9 → 10 experiments, ~430 → ~1,000 bullets.

specification.md

• Spec Gap numbers added as empirical backbone under “Why boundaries aren’t optional.”
• Intent Gap 4-layer model (immediate / final / background / autonomy). 32% production failure rate. RLHF optimises for helpfulness → training signal points at the gap.
• Assumption propagation named as core failure mode. CodeRabbit 470 repos: 1.7× more bugs, 75% more logic errors, 8× I/O bugs in AI code.
• Context Engineering 5-role package added to “Minimum viable spec” section.
• SLUMP / ProjectGuard added under Open Questions.

pipeline.md

• New section: “Parallel decomposition has a measured tax.” 16pp coordination + 11pp info asymmetry floor on parallel workers sharing state. Scope of finding spelled out: does not apply to sequential pipelines or role-specialised agents. u/thurn2 quote: “agent teams = expensive subagents with better marketing.”
• New section: “The pipeline’s advantage shrinks as models improve.” Behavioral Drivers (NCSU, 9,374 trajectories): successful behaviour is agent-determined, framework effect narrows with each model generation. What to measure going forward.
• Parallel decomposition added to Settled Questions.

verification.md

• Expectation-Realisation Gap (arxiv 2602.20292) sharpened METR finding: +24% expected, −19% measured, 43pp calibration error.
• New section: “Four cognitive states in a stuck agent.” Cognitive Companion paper formalises perseveration detection. LLM-based detector (API-accessible, 11% overhead) vs probe-based (requires open weights). Production baselines (LangGraph recursion_limit, AutoGen termination, OpenHands StuckDetector) named as rule-based and missing semantic drift.

self-improvement.md

• New section: “Chase’s three learning layers.” Model / Harness / Context from LangChain’s continual learning framework. Orthogonal to LMP: LMP is about what form, Chase is about where in the stack. OpenClaw explicitly mapped as harness layer. Hot-path vs offline memory updates.
• New practitioner: adelaidasofia/claude-performance, measurement-driven CLAUDE.md with rule retirement (add → measure → retire). “A static rule is a wish. A measured rule is a system.”
• New practitioner: Homunculus plugin, pattern observation daemon auto-writes skills/hooks/commands.
• WebXSkill paper added: skill = parameterized action + NL guidance. +9.8 / +12.9 pts on WebArena / WebVoyager.

context-engineering.md

• New section: “The AGENTS.md cliff.” Paper (arxiv 2602.11988) quantifies context file cliff: success drops past 500 lines. Sweet spot 200–300 actionable lines. ~70% adherence even under budget. Hooks for rules that must hold every time, context files are advisory.

principles.md

• Principle #1 (Process > Context): Behavioral Drivers caveat added. Pipeline alpha shrinks as models strengthen. What to track over time.
• Principle #2 (Boundaries): Spec Gap academic experiment added as quantitative backing for the ablation.
• Open Questions rewritten: Layer 2 “intent language” → “form selection measurement problem.” New open question: does pipeline alpha shrink monotonically.

landscape.md

• New top section: “Opus 4.7 and the silent repricing.” Tokenizer tax, budget_tokens deprecation, xhigh default, +33.5% real cost.
• New section: “April 2026: the spec-driven research wave.” Spec Gap, Context Engineering, SLUMP, AGENTS.md paper, Intent Gap, all consolidated.
• New section: “Harrison Chase’s three-layer framing.” Traces as shared substrate.
• New section: “GitLab’s five autonomy levels.” L1–L5 ladder. Warning about skipping to L4/L5 without verification infrastructure; maps to Amazon’s Sev-1 pattern.
• New section: “Seven anti-patterns from production telemetry.” TechDebt.guru / GitClear / CodeRabbit numbers.
• Armin Ronacher added to “People worth following.”
• Rule-retirement loop added to self-improvement trend.

playbook.md

(Updated one day earlier, Apr 16)

• Rule 1 strengthened with 70% adherence number and hook distinction.
• Rule 4 backed with Spec Gap quantification (89→56, 58→25, full spec recovers ceiling).
• Rule 5 strengthened with Intent Gap 32% production failure stat and XY problem framing.
• Rule 8 gets four-state taxonomy reference (ON_TRACK / LOOPING / DRIFTING / STUCK).
• Rule 15 closes with rule-retirement pattern from claude-performance.

references.md

• 10 new academic papers indexed (17b–17j): Spec Gap, Context Engineering, SLUMP, Intent Gap, Behavioral Drivers, Cognitive Companion, AGENTS.md, Expectation-Realisation Gap, WebXSkill.
• 6 new community / vendor sources (30b–30f, 35b–35d): Chase, GitLab, TechDebt.guru, Cursor best practices, Opus 4.7 migration, claude-performance, Homunculus, u/thurn2.
• Experiment 10 added: Opus 4.7 release analysis.
• People section updated: Chase moved from 🟠 to 🟡, Ronacher added.

What was settled (moved out of Open Questions)

• Parallel decomposition of shared-state code: quantified and settled, don’t do it. Sequential workers sharing a spec artefact is the working pattern. (pipeline)
• Layer 2 direction: settled on form selection, not language invention. Open question moved to “which form for which task” measurement. (principles)

What’s newly open

• Does pipeline alpha shrink monotonically as models improve? Behavioral Drivers finding implies yes. No longitudinal data yet. (landscape, principles)
• Hot-path memory during a session. Our KB extraction is offline-only. Chase’s framing puts a name on the gap; we don’t have an implementation. (self-improvement)
• Spec faithfulness under emergent specification. SLUMP’s ProjectGuard pattern says enforce “every worker re-reads the spec.” We have persistent artefacts but no systematic re-check. (specification)