Software companies
Design docs and technical RFCs: why AI developers value them
By SourceX Editorial · Updated
Short answer
Design docs and technical RFCs matter to AI developers because they record engineering reasoning as a complete arc: the problem, the proposed approach, rejected alternatives, reviewer objections, the decision and, when linked, what happened after the change shipped. Documents with intact review threads and a traceable outcome are worth far more than templates or abandoned drafts.
Key takeaways
- A design doc is reasoning written before the code, which is rare in other engineering records.
- Review comments and the recorded decision matter as much as the proposal itself.
- Rejected and superseded RFCs show judgment and are often as useful as accepted ones.
- Links to implementation pull requests and later incidents supply the outcome that makes a document verifiable.
- Security designs, customer-specific architecture and secrets must be screened out before any document leaves the company.
What makes design docs different from other engineering records?#
Design docs differ from other engineering records because they capture reasoning before the work starts. Commits and pull requests show what changed, and tickets show what was asked. A design doc or RFC explains why an approach was chosen, which constraints mattered and what the authors expected to happen.
That reasoning is hard to find anywhere else. Developers training models to plan software changes, review architecture or explain tradeoffs need examples of experienced engineers doing exactly that, written for peers rather than for a public audience.
Design docs are also unusually well structured. Most follow a house template with context, goals, non-goals, proposal, alternatives and open questions, which makes a collection of them consistent enough to review and prepare.
The four parts that make a design doc reasoning data#
A design doc becomes reasoning data when four parts survive together: the proposal, the review discussion, the decision and the later outcome. Losing any one weakens the record, and losing the review or the outcome weakens it most.
Teams that keep RFCs as markdown files in a Git repository often have the strongest records, because review happens in pull request threads that are preserved with the history. Wiki-based processes can be just as rich, provided the comments survived. Resolved comments are often hidden from the default view, and some export formats keep only page text, so check the export method before judging the archive.
| Part | What it records | Where it usually lives |
|---|---|---|
| Proposal | Problem, constraints, chosen approach and alternatives | Confluence, Notion, Google Docs or files in a repository |
| Review | Objections, questions, suggested changes and answers | Inline comments, RFC pull request threads, review meetings |
| Decision | Accepted, rejected, deferred or superseded, with rationale | Status fields, decision records, meeting notes |
| Outcome | What was built and how it behaved afterward | Implementation pull requests, incidents, follow-up RFCs |
How do AI developers use design docs and RFCs?#
AI developers use design docs and RFCs in three main ways: as examples of how experienced engineers frame a problem, as material for teaching models to review a proposal and spot its risks, and as test cases for whether a model reaches a sound decision. Each use depends on a different part of the document surviving.
Drafting examples need the proposal and its alternatives. Review training needs the comment threads, because they show which objections experienced reviewers raised and how authors answered them. Evaluation needs the decision and, ideally, the outcome: a model can be shown the proposal without the review and asked what the reviewers would conclude, then checked against what actually happened.
That last use is why linked outcomes matter so much. A design that was accepted, built and later caused an incident is a far sharper test than a design whose fate nobody recorded.
Why rejected and superseded RFCs still count#
Rejected and superseded RFCs still count because they show judgment: why a reasonable proposal was turned down, or how a decision that once made sense was replaced. An archive of accepted documents alone tells half the story.
A rejected proposal with a review thread explaining the risks is a compact lesson in engineering tradeoffs. A superseded design linked to its replacement shows how assumptions aged as the product and its load changed. Keep both in scope when you describe your archive.
Where design docs lose their value#
Design docs lose value when the context around them disappears. The document text may survive a migration while comments, status and links do not, leaving a proposal with no record of what anyone thought or what happened next.
Most of these losses can be checked without exporting anything. A sample of documents from different years, read alongside their linked tickets, shows quickly whether the archive holds full arcs or isolated proposals.
- Comments deleted, or dropped by a migration or an export format that keeps only page text.
- Docs kept in departed engineers' personal drives rather than shared spaces.
- Status fields never updated, so accepted and abandoned docs look the same.
- Decisions made in meetings with no notes added to the document.
- No links from the doc to the Jira epics or pull requests that implemented it.
- Templates and empty drafts mixed in with real documents.
What needs screening before design docs leave the company?#
Design docs need screening for security detail, customer information, secrets and third-party material before any of them leave the company. Engineers write candidly for colleagues, and documents often contain things that were never meant for outside readers.
Secret scanning tools help with the credentials row. Gitleaks, an MIT-licensed open-source tool, detects secrets such as passwords, API keys and tokens in Git repositories and files, which covers RFCs kept in repositories. Wiki exports need the same pass, followed by human review of everything flagged.
| Content found in design docs | Typical treatment |
|---|---|
| Security architecture, threat models, known weaknesses | Exclude, or generalize after security review |
| Customer names and customer-specific deployments | Replace with role labels or exclude |
| Credentials, keys and internal hostnames | Remove, and rotate anything that was live |
| Pasted vendor documentation or partner material under NDA | Exclude |
| Pricing, contract terms and unreleased roadmap plans | Exclude or apply a date cutoff |
| Comments about named colleagues' performance | Review and remove |
Illustrative: an e-signature software company sorts its RFC archive#
Illustrative: a fictional e-signature software company keeps its recent RFCs in a GitHub repository and older design docs in Confluence. The VP of engineering wants to know which parts would interest AI developers before committing time to a fit check.
The GitHub RFCs are strong: each has a pull request thread with review comments, a status in the file and links to implementation pull requests. The Confluence docs kept their comments, but many status fields were never updated, and several decisions were made in meetings whose notes sit in a separate shared drive. Security design docs and a set of customer-specific integration designs are flagged for exclusion.
The company describes the GitHub RFCs with linked implementation history as its core package and includes rejected RFCs alongside accepted ones. Confluence docs stay in scope only where the decision can be traced to a recorded outcome, such as a delivered epic or a postmortem, and designs for features that have not shipped fall outside a date cutoff.
How SourceX treats design documents#
SourceX treats design docs as part of a linked engineering record rather than as standalone text. In the SourceX Enterprise Data Value Framework, candid peer review adds human-generated signal and domain expertise, links to implementation and later incidents add AI utility, and security or customer detail adds privacy burden and preparation cost.
Preparation and approval follow the SourceX five-step transaction. The screening decisions, exclusions and permitted uses for each package are written into a SourceX Evidence Packet, which the supplier approves before anything is released.
Frequently asked questions
Do we need a formal RFC process for our design docs to count?
No. Informal design docs, architecture notes and long proposal threads can carry the same reasoning. What matters is whether the proposal, the discussion, the decision and the outcome can be traced. A formal process simply makes those parts easier to find.
Are architecture decision records the same as design docs?
They are related but shorter. Architecture decision records usually capture one decision with its context and consequences, often stored in the repository. They are useful because they state status and consequences explicitly, and they pair well with longer design docs that hold the debate.
Does licensing design docs expose our product roadmap?
It does not have to. Scope can be limited by date, status or product area, and documents about unreleased features can be excluded. Many companies set a cutoff so that only designs for shipped and stable systems are considered.
Should postmortems be included alongside design docs?
Often, yes, when they link back to the design they tested. A postmortem that names the design decision behind an incident closes the loop between reasoning and outcome. Postmortems need the same screening as design docs, since they tend to contain customer impact details, internal hostnames and security specifics.
What about diagrams inside design documents?
Diagrams often carry key decisions but are stored as images, which lose meaning without the surrounding text. Docs that describe the diagram in words, or keep diagram source files, are easier to use. Check that exports keep embedded images and their captions.
Who owns design docs written by contractors?
Usually the company, if contractor agreements assign work product, but that needs checking. Documents written under unclear agreements, or co-authored with a partner company, should be flagged during the rights review rather than assumed to be company records.
Sources
- Gitleaks is an MIT-licensed tool for detecting secrets such as passwords, API keys and tokens in git repositories, files and stdin. Source
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