# Automating cross-repo documentation with GitHub Agentic Workflows

[Github](https://yomu.fyi/company/github) · David Pine · Jul 8, 2026

**Type:** Problem & solution

## Summary

Maintaining documentation across separate repositories often leads to severe lag because technical writers must reverse-engineer shipped features weeks after release. To address this in the Aspire project, the team implemented an automated pipeline using GitHub Agentic Workflows to bridge the product and documentation repositories. When product pull requests merge, a bash step maps milestones to docs release branches before an LLM agent evaluates the diff, drafts documentation updates, and emits structured pull request intents. A dedicated safe-outputs handler materializes these drafts via a scoped GitHub App and assigns the original code reviewers to verify accuracy. Across 396 product pull requests, the system generated 82 documentation pull requests that all merged with a median turnaround time of 44.8 hours.

## Context

The Aspire product and its documentation site reside in separate repositories with distinct review chains and security boundaries, which created a documentation lag where writers had to reverse-engineer past code changes without broad cross-repo write tokens.

## Approach / What changed

The team adopted GitHub Agentic Workflows to run on merged product pull requests, resolving target release branches deterministically, using an agent with read-only access to draft documentation changes, and passing structured intents to a safe-outputs handler backed by a tightly scoped GitHub App.

## Takeaways

- Security is preserved by isolating model execution to read operations and delegating pull request creation to a safe-outputs handler restricted by explicit branch, file, and repository allow-lists.
- Deterministic branch resolution using pull request and issue milestones prevents the model from guessing or misrouting documentation target branches.
- Pre-extracting pull request metadata and issue details in bash steps avoids exceeding model prompt token budgets on large diffs.

**Tags:** [CI/CD](https://yomu.fyi/topic/ci-cd), [Developer Experience](https://yomu.fyi/topic/developer-experience), [LLMs](https://yomu.fyi/topic/llm)

[Read original post](https://github.blog/ai-and-ml/github-copilot/automating-cross-repo-documentation-with-github-agentic-workflows)