What We Did

The setup.

prompt-as-code is an RFC-style syntax standard for treating LLM prompts as code. Published in December 2025, we had iterated it to v0.3.0.

In August 2026, alongside a positioning update toward context engineering, we decided to ship a major update to v0.4.0. But auditing an 1,100-line document solo is not realistic.

So we took a different approach: have different AI models independently review the same document, then cross-reference the results.

Method

Verification design.

We ran the validation in two phases.

Phase 1 Pattern effectiveness We ran the same test prompts for SCoT (Structured Chain of Thought), Few-shot, and CoVe (Chain of Verification) on both Opus 5 and GPT-5.6 Sol to confirm whether these patterns still work on 2026-era models.
Phase 2 Full document audit We fed the entire STANDARDS.md to both models and asked each to independently flag factual errors, missing topics, unnecessary content, and technically incorrect claims. Neither model saw the other's output.

The key: the two models were blind to each other's output. When independent reviewers agree, confidence is high; when they diverge, further investigation is needed — the same principle as human code review.

Phase 1 Results

Do the patterns still work?

Short answer: all three patterns were confirmed effective on both models.

SCoT XML tags separating reasoning from conclusions Both models conformed to <thinking> / <answer> tags. Without the instruction, both said they would default to Markdown headings or freeform text — meaning they do not adopt this structure by default. The pattern has value.
Few-shot Output format control via examples Both models accurately followed the demonstrated format and explicitly stated they would not use the same format without examples. Even on 2026 models, examples remain effective for output format control.
CoVe Self-verification loop Both models followed the C1–C4 loop structure and self-corrected roughly 40% of factual claims in their own drafts. Interestingly, the corrected items differed between models.

The CoVe results are particularly telling. On the same question, Opus 5 corrected "Micronaut 4 release date" and "Blazor United naming," while GPT-5.6 Sol corrected "React library/framework classification" and "ambiguity in GitHub ranking methodology." The same pattern caught different blind spots on different models — strong evidence for the pattern's generality.

Phase 2 Results

What we found.

The full-document audit produced findings the models agreed on and findings unique to each.

Both models agreed (high confidence)

CO-STAR "gold standard" Calling it an "industry standard" was an overclaim. "A widely adopted framework" is more accurate. On attribution, Opus 5 claimed "Sheila Teo introduced CO-STAR, not GovTech." Fact-checking revealed that GovTech Singapore's team developed it and Sheila Teo popularized it through their GPT-4 Prompt Engineering Competition — a lesson that AI review results themselves need fact-checking.
CoVe / CoD language "Becoming standard" and "reference standard" were overclaims for research techniques. Changed to "a recommended technique" and "an effective method."
Extended thinking conflation The in-prompt <thinking> tag (an output structuring technique) and API-level extended thinking from Claude or OpenAI o-series (a model feature) were not distinguished.
Security gaps Only direct prompt injection was covered; no mention of indirect injection via RAG or tool outputs.

Only one model found it (needs investigation)

Opus 5 focused on structural issues (incomplete table of contents, section ordering, model list inconsistencies). GPT-5.6 Sol dug into technical accuracy — triple-backtick Markdown nesting, a RAG code example bug, imprecise SemVer 0.y.z documentation.

What stood out: GPT-5.6 Sol questioned whether "State everything explicitly" is excessive in an era of agentic models. If agents act autonomously, perhaps prompts should only specify goals and constraints — a challenge to the document's underlying philosophy, not a simple right-or-wrong call.

Human Judgment

What humans decided.

We did not accept every AI finding. Both models listed many "missing topics," but most were outside the document's scope.

prompt-as-code is "a syntax specification for text written as prompts." What you can express in Markdown is the boundary.

AI said "this is missing" Human judgment
Structured Output / JSON mode API parameter. Out of scope.
Tool definitions / Function calling API feature. Out of scope.
Multimodal prompting Beyond a text syntax spec. Out of scope.
Prompt caching Infrastructure layer. Out of scope.
Persistent context files Separate topic.

AI casts a wide net: "you're missing this, and this, and this." But scoping the document is a human job. What we discovered was that what was actually missing was not topics, but a scope declaration — "what this document covers and what it does not."

Result

What we changed.

Based on the validation, v0.4.0 includes these changes:

  • 5 factual error corrections (CO-STAR attribution, 3 overclaims, translation template version)
  • 6 technical accuracy improvements (extended thinking distinction, indirect injection, code example bug fixes, etc.)
  • [Step N] notation rationale rewrite ("models fail to parse numbered lists" replaced with "task decomposition, HITL, and output cross-referencing")
  • Structural improvements (completed table of contents, removed stale "NEW" markers)
  • README.md and CONTRIBUTING.md synchronized

All changes are visible in the GitHub repository. Raw validation data is included as test-results-v040-*.md.

Takeaway

What this approach teaches.

Three lessons from this approach.

First, independent model agreement is more trustworthy than a single model's confidence. If only Opus 5 had flagged the CO-STAR attribution, it might have ended with "maybe, maybe not." Two models independently raising the same issue gave us the confidence to act.

Second, models have different perspectives. Opus 5 excelled at structural, bird's-eye review. GPT-5.6 Sol was stronger on code-level bugs and technical definition precision. Using only one would leave blind spots.

Third, scope decisions can only be made by humans. AI is good at casting a wide net, but deciding "what to leave out" is the job of someone who understands the document's purpose and audience.

This is also a practical example of the "design-time context engineering" discussed in the previous article. What to have AI review, and how to judge the results — that itself is context design.