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Changelog

Newest first, and every change carries its date. Only changes you would notice are here: a chapter going live, a stage being renamed, a page being added, a fix you can see. Small work behind the scenes is left out. The book is written and maintained by one person, Afnan Zahed, and this page is updated whenever something ships.

How to read this page

Every change sits under one of four words. New is something that did not exist before. Changed is something that works differently now. Fixed is something that was wrong and is right now. Removed is something that is gone.

2026-09-29​

New​

  • A new page, the Thesis, makes the book's full argument. It sits straight after the Welcome. It shows what AI can now do, the four things it can never do for you, the three steps the whole book is built on, the three skills it teaches and how deep each topic goes, and how you will work with AI through Spec-Driven Engineering. It is written for readers who already know a little about software, and it sends anyone who finds it hard to Stage 0, which starts from the very basics.
  • Six new glossary entries: Agentic AI, AI-native, Software architecture, Spec-driven development (SDD), Technical debt and Vibe decisioning.

Changed​

  • The Welcome page was rewritten, simpler and shorter. It opens on the three skills the book teaches as one: software engineering, building agentic AI, and using AI at an expert level. It names the two ways to get AI wrong, and gives the book's idea in one line: do what AI can't, and ask it to do what it can. Its one call to action now sends you to the Thesis.
  • Code Literacy has a fuller definition in the glossary: reading the decisions and the evidence behind code, and the actual lines when needed.
  • Stage 0 is now described the way it is being written, on its own page, on the homepage, in the FAQ and in the site footer: from zero, with your first tools, your first Python and your first app built by asking an AI, then the ideas that turn all of that into engineering.

2026-09-27​

New​

  • A Catalog page, linked from the top menu, previews the four kinds of Claude Code tools coming beside the free book. Agent Skills, subagents, MCP servers and plugins are each explained in one sentence. Nothing is for sale yet, so the page shows no prices and no dates.

2026-09-26​

Removed​

  • Stage 0's chapters are off the site while the stage is rewritten. The earlier Stage 0 pages, and the draft replacement that had begun to appear beside them, are both gone — out of the menu, out of search, and off the site. Nothing is lost or cancelled: the stage is being written from scratch, and every page you could have opened would have been replaced under you. Until the new chapters arrive, the stage is described in full on the Welcome page, and every link that used to open a Stage 0 chapter now opens that description instead.

2026-09-24​

New​

  • The Welcome page was rebuilt for the book's Alpha launch, and it now says more than it did. It names the two failing habits the book was written to replace, explains how the three stages work and how the learning inside them runs in parallel rather than one subject after another, states plainly that the book is in Alpha and what that means today, lists what is coming and calls it planned, and keeps its one call to action to the very end: follow the changelog and come back for Beta. It points you at no Stage 0 chapter, because that text is being written from scratch.
  • Two new glossary entries. MCP server and Agent Skill are now defined in plain English, because the Welcome page names both when it describes what is coming.

Fixed​

  • Stage 0 stopped showing as "Live" on the homepage. The bar chart and the donut both listed Stage 0 as live and text-ready. Both now say "In development", and Stage 0's bar is a short stub like the other two. The caption under the bar chart promised full bars marked live stages, so it now explains what a full bar means.
  • The headline sentence no longer calls the curriculum "complete". It is a three-stage curriculum, and two of the three stages are still being written.
  • The Stage 0 card on the homepage opens the Welcome page's stages section. It used to open a Stage 0 chapter that is being replaced.

2026-09-23​

New​

  • The book's core skill has its public name: Code Literacy: reading and judging code. It is the ability to read code, whoever or whatever wrote it, and judge it well enough to verify it and own it. Every page that names it introduces it that way the first time, then says just Code Literacy.

Changed​

  • Every button on the homepage now opens the Welcome page. The two buttons under the headline and the one at the foot of the page used to open a Stage 1 page with nothing on it. All three now open the Welcome page, the book's front door, and the buttons whose words no longer matched where they went were renamed: Start reading and See the three stages.
  • Three homepage lines stopped saying things that were not true. "Built for working developers" is gone, because the reader this book is written for starts at zero and finishes as an expert. So is the "Est. Hours 48h" figure: this book never commits to a total, and the card in its place describes how a chapter reads, one file from start to finish. "Every chapter ships twice" now says what actually happens: the written text comes first, and a video lecture from the project owner follows each part of it.
  • Stage 1 and Stage 2 open by saying what they will teach. Stage 1 used to describe itself as a merge of two older stages, one of which no longer exists, and to call its chapters placeholders; Stage 2 ended with a note about a video series that does not exist yet. Each page now carries two plain sentences on what the stage covers, and one saying its chapters are being written now.

Fixed​

  • Search no longer offers pages that are empty or missing. Searching "Binary" returned a result that opened a 404, and other results opened chapters still waiting for their text. The index is now built from the pages that exist and hold real text, so a result you click opens.

Removed​

  • The Harvard certificates are off the site while the course decides. Whether CS50, or any other certificate, belongs in the curriculum is being researched first, as a business decision and a technical one.

2026-09-22​

Changed​

  • The course now has three stages. Stage 0 is Introduction to SDE, Stage 1 is SDE Mastery (AI-Driven), and Stage 2 is SDE Mastery (AI-Native). Agentic AI, meaning AI software that works on its own to get something done, is no longer a stage of its own: it is taught inside software engineering, so directing AI coding agents is learned alongside the engineering rather than in a later part of the course. Every stage list on the site, the Welcome page, the menu, the footer, the homepage cards and the FAQ, now says the same three things in the same order.
  • The CS50 pages are off the site while Credentials is redesigned. Credentials is no longer a stage. It is a separate track that runs alongside the three stages, and it is switched off for now. The two Harvard certificates, CS50P and CS50W, are unchanged: both courses are free to complete, and the verified certificate that makes one printable and checkable is optional and paid. What they are and what they cost is still answered in the FAQ.
  • This changelog page has a new layout. Every entry is grouped under New, Changed, Fixed or Removed, and every claim was checked against the record.

2026-09-21​

Changed​

  • The Welcome page names the stages, and it carries the safety floor. The stage names on the page matched the book but not the menu or the footer, "Foundations" in one place and "Spec-Aware Vibe Engineering Foundations" in another, and all of them agreed after this change. The plain-words safety-floor box now sits on the Welcome page too: whatever the AI writes for you is not finished until you have checked it yourself. One note under "How to read this book" was rewritten in plain words, and the closing section is now titled "Start reading" instead of "Ready?".

2026-09-20​

Changed​

  • The four "why this book" cards on the homepage are cards now. They had no styling at all, so the four headings and the four paragraphs under them ran together as one long column of text with nothing to separate one pillar from the next. Each is now a raised panel with a lit top edge, its number set large and faint in the corner, and its icon in a small raised chip of its own. The four top edges step from light grey to black in order, the same descent down the site's grey ramp that the stages use, so the row reads as one set. Moving the pointer over a panel brings a soft light with it.
  • Both new Stage 0 chapters have been rewritten. How a Machine Holds a Number and How People Told a Machine What to Do now open by welcoming you, saying what the chapter covers and why it matters, and then move into the teaching gradually instead of dropping you into it. Each one is carried by one everyday thing you can picture the whole way through: a torch signalled across a dark street in the first, and a tireless helper with no judgment at all in the second. Hard words the ideas did not need are gone, so a transistor is "a tiny piece of specially treated crystal" now, not "a sliver of treated germanium". The history, the loom, the three kinds of switch, the rewiring of ENIAC and the arrival of FORTRAN are all still there.
  • Chapter and section titles now say what they are about. "Yes, No, and Nothing In Between" is now "Why a Computer Only Says Yes or No". In the menu, "1. Foundations" is now "1. How a Machine Holds a Number" and "2. Programming Is Born" is now "2. How People Told a Machine What to Do". A title should tell you what is inside before you open it.
  • Stage 0 was given a clearer name. It had been "Orientation Through Computing History". It became Introduction to Computing: From Switches to AI Agents, the same stage, named so you could tell what it covered without reading it first.
  • The bold-every-first-sentence style is gone. From 16 September, the opening sentence of almost every paragraph in the book was set in bold. The intention was to make a page easier to scan. The effect was that nothing stood out, because everything did. Bold now marks what actually matters, wherever in a paragraph it falls, and pages are made easier to scan with bullets, tables and shorter sections instead.
  • The glossary stops talking to itself. Entries used to carry notes written for the book's own authors, "Beginner · Summary" and "Advanced · Detailed" among them. Those are gone; each entry now simply says where in the book you first meet the term.

2026-09-17​

New​

  • A new stage introduction opens Stage 0, and heads its menu list. The Introduction to Stage 0 page is the stage's welcome page: what Stage 0 covers, grouped into the five stretches it is built from, what you will be able to do at the end of it, what it costs (nothing to install, nothing to buy, no account), why checking an AI's work cannot be handed to the machine, and an honest note that there is no quiz and no certificate here. The real credentials this book leads to are CS50P and CS50W, both free to complete. It closes by handing the reader into How a Machine Holds a Number, naming the traffic light and the telegraph key that chapter then opened on. The book's original five chapters stay exactly where they were.

Changed​

  • The new stage introduction was given a full pass the same day. It names itself the first stage of the book, explains that the stage runs in the order computing developed, each idea after the problem that produced it, links Spec-Driven Engineering where the book's four-step workflow is named, points at the stage's last chapter for the practice in full, and asks readers to take the chapters in order.
  • The two new chapters are linked from the menu. They sit at the end of Stage 0's list. The book's original five chapters stay where they were, and nothing was removed or reordered, so both sequences are reachable while the rest of the new line of chapters is written.
  • Stage 1's six chapters are back to "content to be added". They had shown full text from 11 September, and from this day the six chapter pages are empty again. The stage's own page carries the note the rest of the stage carries: detailed chapter content is to be added when the video series is recorded. If you read any of that earlier text, treat it as withdrawn rather than current.
  • Both new chapters now open with an orientation. How a Machine Holds a Number and How People Told a Machine What to Do each say why their subject arrives now, list the steps they move through, and name what you will be able to do at the end of it. Both were also thinned out: the dates and full names that had piled up in the prose are gone wherever the story carries the point without them, and the run of paragraphs that each opened on a bolded sentence now reads as ordinary prose. The teaching is unchanged: the traffic light, the loom, the three switch bodies, the rewiring of ENIAC and FORTRAN are all still there. (Both chapters were rewritten again on 20 September.)

2026-09-16​

New​

  • The first two chapters of a rebuilt Stage 0 have shipped. They are How a Machine Holds a Number and How People Told a Machine What to Do. They open a new, single line of chapters, in the order computing developed, with nothing taught before the thing it depends on, running from a two-state switch through the first working compiler in 1957. The book's original five chapters stay live while the rest of the new line is written. These two chapters were not linked from the menu until the next day.

Changed​

  • A chapter's prose is set to a readable line length. The reading column used to spread to whatever width the screen allowed, which at a desktop size put about 98 characters on a line, well past the 45 to 75 that reading comfortably holds, and that was the main reason a dense page read as a wall. It was capped so a line carried about 70 characters at a wide size, and the column sat centred with an even margin either side instead of pressed against the left of the leftover space. Nothing moved on a phone or a small laptop, where the line was already inside the band.
  • Chapter titles and section headings are heavier, larger and underlined. Every heading level in use steps up 10%, reads at bold weight, and carries a hairline rule under it that runs the width of the text block, so a title that wraps to three lines gets one rule under the block, not one rule per line. The title's old short accent bar is gone, because two rules under one title is one rule too many.
  • About one sentence in five is set in bold, on one rule. The rule is the opening sentence of a paragraph, which is the sentence that says what the paragraph is about. Emphasis the text already carried is left exactly where it was, and a paragraph whose first sentence is a link or already emphasised takes the next sentence instead. This style was retired on 20 September.
  • A glossary term is marked quietly now instead of loudly. It used to carry four signals at once, the display serif, an accent colour, a full-strength underline and a tinted background, which made a defined word read as a foreign object inside its own sentence. It stays in the reading ink and is marked by one thing: a fine dotted accent underline that turns to the accent colour when you hover it. Ordinary links are unchanged, so a term and a link no longer look alike at a glance.
  • Italics are emphasis again, not a change of typeface. The display serif is kept for the one surface that wants it: a pull-quote inside a chapter, which now sets larger in that serif with a short accent rule above it, and no left border. List bullets take the same small accent diamond the headings use, and the space between paragraphs, headings, tables, quotes and code now steps by a single scale instead of eight unrelated numbers.
  • The reading column's side margins are about 30% smaller. The column used to be a fixed width, which had two consequences: the empty margin was 119px per side at a desktop size, and folding the left sidebar made that margin wider, 216px, while the text stayed exactly where it was. The column now holds a constant margin and lets the text fill everything else, so it grows into whatever the panels free up and stops there. The line lands around 80 characters at a desktop size, against 71 before; a narrower margin would have reached 85, which is why it stops short of a 50% cut.
  • The On this page panel folds away now. A handle at its head names the action, and folded it leaves the same 44px rail carrying the same mark aimed the other way, so either edge of the page can be cleared for full-width reading. It moves on the same 200ms clock as the sidebar rail, holds its own contrast in both light and dark mode, and remembers being folded as you move between chapters. The text widens to meet the space and narrows again when the panel returns.

2026-09-15​

New​

  • A Welcome page opens the book, ahead of Stage 0. It states the founding claim, what "balance" actually means and why checking an AI agent's work cannot move to the machine, then what you need to start (nothing), how the stages fit together, how a chapter is meant to be read, an honest list of what the site does not have yet (no community, no help chatbot, no certificate), and who actually writes and maintains the book.

Changed​

  • The Welcome page's key terms link to the Glossary at their first use. Coding agent and Spec-Driven Engineering are the two. Its "why can't the checking move to the machine" section now names the gap between what the word "agent" implies, something that decides on its own, and what actually runs, software whose independence is a setting you control rather than a trait it has.
  • The reading page's type was rebalanced so headings lead it again. Body prose, code, tables, callouts, the menu and the On this page list all stepped down together, and the line length stepped down with them so a line still held the same number of characters.
  • The sidebar's collapse control is a labelled handle now, and the space it leaves behind is a designed rail. Collapsing used to leave a blank 30px strip with a grey arrow floating at its centre, while the control that did the collapsing was a full-width bar with square corners and a chevron pointing at nothing. Closing the panel is now a capsule at the panel's foot that names what it does, and the collapsed rail is 44px wide with the panel's own mark at its head, the same 44px target the rest of the site's controls use. The same mark, aimed the other way, brings the panel back.
  • The Welcome page was substantially revised. Spec-Driven Engineering is now introduced as software engineering plus AI, using an AI coding agent today and building one later, with the problem it solves, why checking stays with a person, and the stage table folded into one section instead of three. New sections cover what background you do not need, a what-you-need and what-you-do-not table, how the book's stage, chapter and lesson structure works and why it is ordered that way, and a roadmap-toned account of what is still being built. The call to start reading now sits at the very end of the page, after it has actually said what the book is.
  • Every table now reads as a raised card. Rounded corners, a soft shadow, a header styled as a small-caps label instead of bold text on flat grey, and a hover highlight on each row. This is a sitewide style change, not a per-page one, so it also reaches the comparison tables already shipped in the chapters on the terminal and on spec-driven engineering, and in Stage 1's Core Programming and Backend chapters, not only the two new tables on the Welcome page.
  • Every table's header row is a dark, top-lit rail now, in the site's own metal finish. The flat mid-grey fill it replaced carried grey labels that measured below the readable-contrast floor in both light and dark mode; the labels now clear it with room to spare. Nothing else about a table changed.
  • In dark mode the two side panels sit on the same ground. The left sidebar and the On this page panel now share one tone, between two steps of the site's grey ramp rather than either step itself. The sidebar came down to it and the panel came up to meet it, so the tonal step that used to separate the two panels is gone. The sidebar's own labels got easier to read as a result, not harder. Light mode was untouched.
  • Light mode's page is no longer pure white. The reading column now sits on a very light paper tone and the two document panels half a step deeper, so the ground reads as paper rather than glare and pure white is left to the surfaces meant to catch light. That moved light mode, which the note above deliberately left alone. The panels' small labels stepped one half-step darker to stay above the readable-contrast floor on their new ground. Dark mode was untouched here; its page stays pure black.

2026-09-14​

New​

  • Stage 0 became an official stage of the curriculum. It sits before Stage 1 and covers computing history from binary through today's AI-coding-agent era, plus the Spec-Driven Engineering approach the rest of the book depends on. The curriculum was five stages (0 through 4) at that point, not four.
  • Chapters can now be labelled Theory or Practice. A label is built into the site so you can tell at a glance whether a page teaches a concept or walks you through doing something. No chapter carries one yet; the labels go on as chapters are written.
  • Two new reference pages shipped: a Code of Conduct and an Accessibility Statement. The accessibility statement names the real WCAG 2.2 AA baseline the site aims at, and the automated checks that keep it honest.
  • A FAQ page shipped, independently checked against the rest of the site before publishing.

Changed​

  • The homepage dashboard shows the stages, not a chapter count. It was rebuilt to show each stage as it stood, and it dropped the old fixed chapter count. This book does not commit to a total chapter number in advance, because the curriculum keeps growing.
  • The homepage's two curriculum charts were rebuilt. The bar chart shows each stage's real authoring status instead of a chapter count, and the donut shows the stages as equal parts of one whole instead of an hours breakdown. Both had been dropping Stage 0 and stating numbers this book does not commit to.
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