Changes

Checks that are due

Scheduled, not aspirational. If one of these dates passes and nothing appears in the log below, the site has broken its own promise and you should discount it accordingly.

• End of August 2026 — introductory pricing. Done early, 11 August 2026, and it found a correction. See the log entry below. The promotion that was scheduled to expire has instead been made permanent, so there is nothing to re-check at the end of the month.
• Monthly — Model facts. Prices, model IDs and limits. The fastest-rotting page on the site by a wide margin.
• Quarterly — the concept pages. They're written to avoid hard numbers precisely so they age slowly, so this is a lighter pass: does the explanation still describe how these systems actually work?
• Quarterly — the resource lists on Start here. Courses get retired, reorganised, and quietly moved behind a payment page. Every link gets opened, not just pinged.

The log

11 August 2026 — correction: the Sonnet 5 price warning was wrong

What this page used to say. Model facts carried an asterisk on Claude Sonnet 5's $2 / $10 rate, describing it as introductory, giving $3 / $15 as the standard rate, and telling readers to check whether the promotion had ended before budgeting off it. It was presented as the site's worked example of why undated pricing pages are dangerous.

What is actually true. Anthropic's pricing documentation now states that the $2 / $10 pricing, "announced at launch as introductory pricing through August 31, 2026, is now the standard price," and that "the previously scheduled increase to $3 / $15 per million input/output tokens on September 1, 2026 will not occur." The warning and the asterisks have been removed, and the correction is stated on the page rather than quietly swept up.

This check was scheduled for the end of August. Running it early cost nothing and caught a page that had been wrong since the vendor's decision changed. Worth being blunt about the lesson: the error was not in the number, which was right the whole time, but in the story attached to it. A stale caveat is as misleading as a stale figure, and it is far easier to miss, because nothing about it looks like a number that needs re-checking.

The rest of the Anthropic table was re-verified at the same time. Context windows, output limits, prices and both cutoff dates for all four models match the vendor documentation as of today, unchanged.

11 August 2026 — two reference pages: the limits, and the vocabulary

What AI is actually bad at covers the weaknesses that follow from how these systems are built rather than from this year's models being immature: no reliable sense of its own ignorance, no clock or continuity, unreliable self-report, trouble with exactness and character-level work, whole-corpus questions that fail quietly, reliability decaying over long tasks, inconsistency between identical requests, and thin coverage delivered in the same confident register as thorough coverage. It deliberately lists no tasks, because task lists are what make this genre of writing stale within months. It also says what these systems are genuinely good at, since a limits page that only lists failures gives a false picture.

Glossary defines the vocabulary in a sentence or two per term, linking onward where a full explainer exists. Terms only, no product names: products change faster than definitions, and this page is meant to stay useful.

Small correction while adding them: the not-found page claimed to list "everything on the site, in full," which stopped being true several pages ago. It now says "the main sections" and points at the new pages too.

11 August 2026 — the blank vendor rows on Model facts are filled

Model facts carried empty OpenAI, Google and Meta rows from launch, flagged as unverified rather than guessed. Those are now checked against each vendor's own documentation, with every source linked and dated on the page.

Two things came out of the check that were worth more than the numbers:

• Meta doesn't fit the table, and that is the finding. Llama models are downloaded and run wherever you choose, so Meta publishes no per-token price for them; cost depends entirely on the host. Meta's paid API sells different models, and its pricing page states rates without publishing context or output limits, so those cells now read "not published" rather than borrowing a figure from a third party.
• Cross-vendor price comparison is weaker than it looks. Identical per-token rates don't mean identical cost for the same job, because tokenisers differ and the same text is a different number of tokens for each vendor. The table now says so, rather than inviting the comparison it can't support.

Also recorded: OpenAI publishes a knowledge cutoff for its current family, while the Google model page checked does not, which is why that table has no cutoff column. Google's tiered, batch, flex and priority rates and Meta's contributor tier are noted but not reproduced, with a pointer to read the vendor page before budgeting.

11 August 2026 — Thinking and reasoning, and the roadmap closes

Thinking and reasoning is live. It explains the mechanism without the mystique (the model writes out working, then answers with that working in front of it), separates the problems where it genuinely helps from the ones where it only produces a longer route to a guess, and covers a cost trap worth knowing: changing your thinking settings mid-conversation invalidates prompt caching.

It also carries the finding most articles on this subject leave out. Anthropic tested whether stated reasoning reflects actual reasoning by slipping models hints, and found they often used the hint without mentioning it. Visible reasoning is working shown, not a confession, and it should not be treated as a way to verify an answer.

That completes the ten concept pages planned at launch. The concepts hub no longer lists a queue, for the reason given there: a list of pages that don't exist yet isn't worth much, and keeping the existing ones correct is the harder and more useful half of the job.

11 August 2026 — two more concept pages: Fine-tuning and Prompt caching

Fine-tuning argues the distinction the previous two pages kept deferring: it changes how a model behaves, not what it knows. Facts trained in this way cannot be cited, cannot be corrected without retraining, and carry a standing upgrade cost, since a tuned model is frozen against a base model that will be superseded. Use cases and the "prompt engineering may be all you need" line are quoted from OpenAI's own documentation, along with the observation that knowledge acquisition is absent from its list of benefits.

Prompt caching covers the cost lever that rarely makes it into tutorials, and the accident that quietly ruins it: putting something that changes every request inside the section you meant to reuse, so the system writes a cache entry every time and never reads one. That failure produces no error and no visible defect, only a bill. Mechanics quoted and cited from Anthropic's documentation; the rates, lifetimes and minimum sizes deliberately left out, because they are model-specific and change.

That closes the original concept roadmap except for Thinking and reasoning. Nine live.

11 August 2026 — new concept page: RAG and retrieval

RAG and retrieval is live, the seventh concept page. Its argument: retrieval is mostly a search problem, which is why most of it fails at the search rather than at the model, and the single most useful habit is to test the retrieval step separately from the answer. Also covers the case for skipping the machinery entirely and simply pasting your documents in, which is now the right first move for small collections. Chunk-context and hybrid-search points are quoted and cited from Anthropic's engineering write-up.

No recommended chunk size, no vector database comparison, no embedding rankings, no accuracy figures. Same reasoning as every other concept page: those rot fastest and read as authoritative while doing it.

11 August 2026 — new concept page: Agents

Agents is live, the sixth concept page and the first written after launch. It takes the position that an agent is a model in a loop with tools, that the loop is where every hard problem lives, and that the workflow/agent distinction is the useful one to hold onto. Definitions are quoted from Anthropic's own engineering guidance and cited on the page.

Deliberately contains no benchmark scores, no framework comparison and no reliability percentages, for the reason given on the page: those are exactly the figures that would make it wrong within a season while still sounding authoritative.

11 August 2026 — three pages added, including this one

Added the same evening as launch, and all three are about making the site's claims checkable rather than adding more surface to maintain:

• This log. The reasoning is in the box at the top of the page: a date stamp says when something was checked, and says nothing about whether anything happens when a fact rots.
• Is what you're reading out of date? The verification method used here, written up so it works on anything else you read. Contains no figures at all, on purpose.
• About. Who writes this, who maintains it, how it's funded, and the one commercial connection, disclosed rather than tucked away. For a site whose product is trust, having no named human anywhere was a real gap.

11 August 2026 — the site went live

Published at plainlyai.org with nine pages: a home page, a placement guide, five concept explainers and the model facts table. Everything dated on the day it was written.

Three corrections came out of verifying the Start here resource lists, and they're recorded here rather than quietly patched, because a site about trusting sources doesn't get to hide its own edits:

• A course was wrongly tagged "free." One recommended catalogue publishes no pricing on its index and mixes free short courses with paid certificates. Retagged "mixed, verify per course."
• The beginner track pointed at developer documentation. That documentation says, on its own front page, that it's written for developers. Beginners now get a beginner-facing course, and the API docs moved to the builder track where they belong.
• "Free" was softened to "price not stated" on two entries. Both are openly accessible, but neither publishes pricing on the page checked, and openly accessible today is not the same as documented as free.

One finding from writing the Tokens page is worth repeating here, because it's the clearest example of the rot this site exists to counter: the near-universal rule of thumb for converting words to tokens is now materially wrong, and dividing out a vendor's own published figures shows it. It has been repeated unchanged across the web for years, including by models that learned it from the web. The arithmetic is on the page.

Same day — the plumbing

Not content, but it affects what you get served: clean URLs throughout, a real not-found page instead of a blank one, and a strict content security policy. The site ships no JavaScript at all, so the tightest possible policy costs nothing. Nothing here tracks you, because there is nothing here to track you with.

What counts as a change

Three kinds of entry appear in this log, and they're not equally important.

Corrections are the ones that matter. Something here was wrong, someone noticed, it's fixed, and the log says what it used to say. A site that only ever adds and never corrects is either perfect or not checking.

Re-checks are the invisible work: a figure confirmed still accurate, a link opened and found alive. Nothing on the page changes except its date. This is most of the actual maintenance, and it's the part that content farms cannot fake, because it costs exactly as much as being wrong costs nothing.

Additions are new pages. Least interesting from a trust standpoint. Anyone can add.

Learn the method → Is what you're reading out of date? · The numbers → Model facts