Documenting Claude Architectures and Writing Implementation Guidance

1.Start the document with the build-path decision

Discovery and stakeholder conversations produce a decision. The architecture document is where that decision gets written down in a form an engineering team can build from. For a Claude solution, the first decision to record is usually the build path. It matters more than anything else in the document because it decides what the team has to own. If you write your own agent loop, the team owns retries, tool execution, hosting and state. If Anthropic hosts the loop, the team owns configuration and integration instead. So an architecture document that names the components but leaves out the build path leaves the most important question unanswered: who runs what.

Record the reason for the choice next to the choice. Anthropic's own guidance on agentic systems is to find the simplest solution that works and add complexity only when it is needed. That gives you a useful test for the document itself: does it explain why a simpler design was not enough? A reviewer who reads 'multi-agent orchestration on a hosted runtime' should be able to find the sentence that explains why a single well-prompted call, or a fixed workflow, would not have done the job. Without that sentence, the next team to touch the system cannot tell whether the complexity is load-bearing or accidental.

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2.Document boundaries and hard constraints explicitly

Once the build path is fixed, the next thing the document must make clear is where the trust boundaries sit. Protocol specifications show what this looks like when it is written down properly. The Model Context Protocol architecture states plainly that servers are isolated from each other and from the full conversation, and that the host process enforces those boundaries. That kind of statement is worth copying into your own documents. Every integration should come with a line saying what data it receives, what it can never see, and which component enforces that.

Hard constraints come from the platform too, not only from the customer's policies. Compliance properties of the chosen build path are a common example. The Managed Agents documentation says the product is stateful by design and, because of that, is not currently eligible for certain retention and healthcare agreements. A document that recommends a hosted, stateful runtime for a regulated workload without saying so hands the engineering team a problem they will only find in a security review. Put constraints like this in a named section, and link each one to the requirement it came from in discovery.

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3.Write implementation guidance that can be followed and checked

Implementation guidance fails in a predictable way: it tells people to do vaguely good things. 'Test your changes' and 'keep files organized' feel responsible, but nobody can check whether they were followed. Anthropic's guidance on writing instructions for Claude Code makes the same point, and it applies just as well to guidance for human engineers. Give the exact command, the exact directory and the exact rule. Specific guidance can be verified in review. Vague guidance only gets discussed.

Copy `.env.example` to `.env` before running anything. Tests and the dev server fail without it.
Write database queries with the Knex query builder. Never put raw SQL strings in route handlers.
Never edit a migration after it has merged. Add a new migration instead.

Notice what each line does. It either says what goes wrong if you skip it, or it pairs the prohibition with the thing to do instead. The same source lists what belongs in guidance (commands, conventions, a short architecture summary, hard constraints, known gotchas). It also lists what does not: full API documentation the reader can get from the code, changelogs, and aspirational rules the team does not actually follow. That last one matters most for an architect. Guidance that describes an ideal nobody practises teaches engineers that the whole document is optional.

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4.Treat the documents as part of the system's lifecycle

An architecture document is written at design time but read during the pilot, in production, and when the solution is eventually retired. It only stays accurate if updating it is part of the normal change process. The practical rule from Anthropic's large-codebase guidance is to review documentation edits in pull requests like any other change, so that the conventions change when the code does. A design change that ships without a matching documentation change should look incomplete to a reviewer.

AI systems add a second reason for documents to go stale: the model underneath improves. Guidance often includes workarounds, such as 'split this task into single-file steps' or 'always add this extra validation pass', that exist only because an earlier model struggled. After a major model release, those instructions can become overhead with no benefit. So a mature architecture document marks which guidance is a workaround for a model limitation and which is a real business or security constraint. Then it is clear which lines to test and possibly delete after an upgrade, and which ones must never be touched.

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Exam traps

Each one states something that sounds right. Open it to see what is actually true.

1. 1.Choosing a hosted, stateful agent runtime makes the architecture suitable for any regulated workload, because Anthropic operates the infrastructure.Why is that wrong?

   Who operates the runtime says nothing about its compliance eligibility. Managed Agents stores session state server-side, and its documentation states it is not currently eligible for these agreements. That constraint has to appear in the architecture document.

   Covered in Document boundaries and hard constraints explicitly

2. 2.The most complete implementation guide is the best one, so it should reproduce full API documentation and the change history.Why is that wrong?

   Guidance should hold what the reader cannot get elsewhere: commands, conventions, constraints and gotchas. Full API reference and changelogs are explicitly listed as not worth including, because they add bulk without adding direction.

   Covered in Write implementation guidance that can be followed and checked

3. 3.Once implementation guidance has been validated in production, its instructions are permanent and should not be revisited.Why is that wrong?

   Instructions that work around a model's weaknesses have a shelf life. After a model upgrade they should be re-tested and removed if the newer model no longer needs them.

   Covered in Treat the documents as part of the system's lifecycle