Changelog

Covers the full stack: what OpenCode is, installation, agent system (Build/Plan/subagents), configuration (9-layer merge pipeline), 20+ builtin tools, session lifecycle, permission system (ask/reply/evaluate), skills & plugins (SKILL.md, custom tools), MCP integration (local/remote/OAuth), and CLI workflows — all with source-code citations.

Each lesson starts from the core abstraction — the Permission Interface, the Agent Info schema, the Tool.Def type — and builds up from there, showing actual TypeScript from opencode's source.

Every significant function, interface, and type is linked to its source file and line range on the dev branch (commit b10d617c8), making it easy to navigate the actual codebase.

A comprehensive journey from single-agent fundamentals to multi-agent production systems: agent evolution, architecture (harness, two-axis map), perception & memory, reasoning & planning, action & tools, reflection, single-agent patterns, multi-agent overview, orchestration patterns, coordination, governance (HITL/HOTL/AFK), and production engineering (evaluation, observability, benchmarks).

Four advanced lessons added to the Context Engineering domain: the context engineering stack (core + harness), six-level context sources taxonomy, context management & orchestration (selection, writing, compression, isolation), and context evaluation, observability, governance & operations.

Three questions per lesson (warmup, mid-lesson, end-of-lesson) covering all 16 new lessons, with scenario, tradeoff-analysis, architecture-review, and multiple-select question types.

Every concept is explained through concrete examples from real agent tools and frameworks so you can apply what you learn directly to your own projects.

The Token Management lesson now embeds a calculator directly under "What Is a Token?", type or paste text and watch it split into colored token chunks live, illustrating how subword tokenization works.

Choose between the legacy tokenizer (Sonnet 4.6, Haiku 4.5, Opus 4.6) and the current one (Opus 4.7, Opus 4.8, Fable 5, Mythos 5) to see Anthropic's documented ~1.0-1.35x token-count difference applied to your text.

There's no public client-side Claude tokenizer, token_counts are only available via the real /v1/messages/count_tokens API. The calculator says so directly rather than implying production-accurate counts.

LessonViewer can now mount a React component at an exact marker inside raw lesson HTML, instead of only before/after the whole lesson body like the existing quiz embeds, reusable for future interactive widgets.

81 of 83 multiple-choice questions in the core bank had their correct answer at position A, with throwaway distractors, gameable by always picking the first option. All 81 are now shuffled to a random position with matching, rewritten explanations.

The Udemy-sourced question bank (1,184 questions) had only 543 unique IDs, 641 questions silently became unreachable whenever a same-ID sibling was already chosen for an exam. Every ID is now unique.

The default single-answer-only filter only allowed presentational type 'multiple-choice', excluding nearly all 'scenario' questions even though they're also single-answer. The filter now checks actual answer count, not presentation style.

Found and rewrote 14 Udemy-bank questions with blank explanation fields (and one with a flatly wrong correct answer) surfaced once they entered the wider exam pool.

The Exit button during an exam now offers a direct "End Exam Now & See Score" option, instead of a confusing two-step Exit → Review → Exit-again flow to finish before answering every question.

On a lesson page, the sidebar now shows only that domain's chapter list (with the current lesson highlighted) instead of the full Exam Domains / Courses / Navigation / Quick Links tree every time.

Reopening the sidebar on a lesson page was immediately undone by the auto-close effect, which re-fired every time the sidebar's internal setOpen identity changed (i.e. on every toggle). It now only auto-closes once per lesson visit.

The floating edge toggle shown when the sidebar is closed is now larger with a subtle shadow, so it's easier to spot on lesson pages.

Agent Loops' "200K context limit" callout now correctly notes the limit varies by model (Haiku 4.5: 200K, Opus 4.8 / Sonnet 4.6: 1M), found during a content-accuracy audit.

Increased the diagram's viewBox and spacing so the FAN-OUT, PIPELINE, and ROUTER sections no longer crowd each other.

The ROUTER section title sat almost on top of the Billing node; rows were shifted down with proper clearance so the title is fully clear of every box.

Reduced stroke widths to 1px, dropped bold font-weights to 400-500, and switched accent colors to muted rgba tones for a calmer, native-feeling diagram.

Every diagram in the course now uses the new .lesson-diagram system: ray.so-style squircle cards with themeable grid backgrounds, OOAD-shaped nodes with proper colors, and smooth bezier-curve arrows instead of straight lines. The token-management lesson also has a new cylindrical context-window gauge (range-element look) explaining token allocation.

The Claude Code agent loop SVG was shrunk from 640×250 to 520×200 with compact nodes and legible text, fixing the oversized-diagram complaint on mobile.

The permission-request block in core-capabilities now renders as a dark terminal-styled pre block with green additions, red deletions, highlighted keys, and a Claude Code-like header, replacing the old ASCII box-art.

New 5-step numbered journey section (diagnose → path → practice → mock → ready) with time estimates and a connecting spine. Trust band contrasts proctored conditions, real captured data, and evidence-backed recommendations against generic Q&A sites.

The top navigation bar now only appears on the landing page. Inside the app (lessons, dashboard, exams), all actions are in the sidebar. Mobile shows a minimal fixed header with logo and sidebar toggle only.

Theme toggle and font-size controls now live in the sidebar footer so they are always reachable even without a top header.

Both FAQPage schema.org blocks updated from stale '12 domains / 72 lessons / 715 questions / 65Q-130min-75%pass' to the verified '5 domains / 116 lessons / 800+ questions / 60Q-120min-720pass' facts. Removed the incorrect 'multiple select' question-type claim, the real exam is single-answer MC only.

Original, exam-grade scenarios covering the patterns the real exam leans on: application-layer policy enforcement vs. prompts, per-segment confidence validation, filtering stale tool_results on resume, schema redundancy for math consistency, resilient catch-all enums, the limits of retry loops, tool_choice for execution order, shared vector stores vs. daisy-chained logs, goal-oriented delegation, and structured escalation handoffs.

Distilled the Anthropic Cookbook recipes and production-architecture material into an internal reference so our scenarios mirror the constraint tradeoffs (latency, accuracy, cost, compliance) the exam tests.

Added genuine, exam-aligned warmups so all 86 exam lessons now have four or more, closing 24 lessons that previously had none and ~50 that had only two. Each question is written to the verified CCA-F facts, not filler.

Warmups are shuffled on each visit and lessons with four or more surface a fresh subset (3 of N) each time, so revisiting a lesson no longer shows the same static set.

Added a model deprecation timeline with verified end-of-life dates (claude-3-haiku, Sonnet/Opus 4.0, Opus 4.1) and context on legacy generations including Claude Instant, so older-model exam questions are unambiguous.

Warmups about the system prompt now match what the page actually teaches, message roles, the top-level system parameter, alternation, caching, and the security boundary.

Every release now records its immutable deployment URL here, so you can always open the exact version that shipped with a given update.

Our own client-side tracking SDK now records your entire learning session, reading depth, scroll, time-on-task, active/idle, page views, and every warmup, quiz, practice, diagnostic and exam answer. Stored locally (private) with optional cloud sync.

Evidence-backed recommendations rank what to study next using recency-weighted mastery, repeated-miss and overconfidence detection, and scenario-vs-recall gaps, each with a 'master this topic → open the lesson → try again' action, weighted to the official 27/20/20/18/15 exam split.

Real-exam proctoring: detects tab-switching, copy/paste, right-click, developer tools, fullscreen exit and blocked shortcuts; logs violations, shows an integrity score, and auto-submits on repeated serious violations. Scores scale to the CCA-F 1000-point range (720 = pass).

Dashboard, progress and readiness now reflect your actual captured activity, real study time, streaks, per-domain mastery and reading progress. No placeholder numbers.

The in-app EPUB reader now initializes reliably and resizes in place (no more blank viewer), with a corrected page-position readout.

Resolved the blank-PDF-in-production issue and shrank the file via self-hosted fonts; the in-app reader defaults to a fast HTML view with PDF/EPUB downloads.

Refreshed model IDs (Opus 4.8 / Sonnet 4.6 / Haiku 4.5 / Fable 5), migrated structured-output examples to the current API, and reconciled the lesson count to 116 across the site and book.

Comprehensive deep-dive lesson covering the new Mythos-class models, architecture, safety guardrails, SWE-Bench Pro 80.8%, Project Glasswing, and the June 12 US government suspension. Added to 'Latest Updates' domain with 10 practice questions and integrated across flashcards and mock exams.

Added 'Beyond the Main Tiers: Mythos-Class Models' section with comparison table, safety architecture explanation, and link to the dedicated lesson.

Named @page rules for chapter-start/part-start sections, opening pages of chapters and parts now have zero top margin for cleaner layout.

Fixed production build pipeline, old 21.9 MB PDF was stale. Replaced with fresh 16.4 MB version containing all 104+ lessons.

Fable/Mythos lesson added as Part V (Appendix) in the HTML/EPUB/PDF book generation, shows as chapter 116 in the compiled book.

This very page! A dedicated timeline of every feature, fix, and content update, ordered newest first.

Mock exams now strictly follow official CCA-F domain weights (27/20/20/18/15). Each exam draws exactly the right number of questions per domain, matching the real exam proportions.

New comprehensive strategy guide page with time management tactics, question elimination techniques, and domain-specific tips.

Exam results now show performance broken down by each of the 5 official domains, pinpoint exactly which areas need more study.

If you consistently score above 85%, mocks automatically sample harder questions (including pro-level ones) to keep challenging you.

Every question now includes a wrong-answer explanation for each incorrect option, not just why the right answer is right, but why each wrong answer is wrong.

Questions that were tagged at the wrong difficulty level or domain have been redistributed. The question bank is now more representative of actual exam difficulty.

Ambiguous, misleading, or duplicate questions replaced with clearer alternatives. Each rewrite was verified against Anthropic's official documentation.

New 'Common Traps' page cataloging the most frequently missed question patterns, with strategies to avoid each one.

Full audit and fix: skip-to-content link, aria labels on all interactive elements, proper landmark regions, focus indicators, reduced-motion support, and color contrast improvements.

Comprehensive test suite covering auth flows, lesson navigation, exam functionality, accessibility (axe-core), and Supabase progress sync.

Vercel-style near-black dark theme applied site-wide. Better contrast ratios, consistent card surfaces, and improved code block readability in dark mode.

Quiz card height clipping fixed, sidebar collapse behavior improved on mobile, table overflow scrolling on narrow viewports.

Entry exam covering all 5 domains that maps your strengths and weaknesses before you even start studying. Generates a personalized study plan with estimated score prediction.

Based on diagnostic results, the study plan reorders lessons to prioritize your weakest areas while respecting prerequisite chains. Updates as you progress.

New composite score (0-100) that combines mock exam performance, flashcard retention, and lesson completion rates into a single readiness metric.

Exam results now highlight specific lessons that are dragging down each domain score, with direct links to the relevant material.

Flashcards now use the full SM-2 algorithm, scheduling reviews based on your performance history. Cards you consistently recall appear less frequently; cards you struggle with appear more often.

Advanced pro-level questions added to the pool, harder, multi-step scenarios that test deep understanding rather than recall. Filterable in practice mode.

Interactive graph view now shows prerequisite chains, concept dependencies, and domain cross-links. Hover a node to see its connections highlighted.

Replaced analogy-driven explanations with mechanism-first writing across 49 lessons, focusing on how and why things work, not just what they're like.

Every lesson now includes a CCA-F Exam Tips section with likely scenario questions, key concepts to memorize, and common pitfalls tested on the real exam.

Full test coverage for the adaptive study plan algorithm, validates prerequisite ordering, weak-area prioritization, and plan recalculation after progress updates.

Fixed a bug where quiz options used position-based ID mapping instead of content-based mapping, causing incorrect shuffling behavior across quiz attempts.

Corrected scoring edge case where partially-completed mocks showed inflated scores due to NaN handling in unfinished sections.