Codeac Diff Highlight Not Showing Changes in a Pull Request: Diagnostic Guide

When Diff Highlight stays empty on an open pull request

If Codeac’s Diff Highlight panel shows nothing while GitHub clearly lists changed files, do not treat the pull request as unchanged. The useful takeaway is to separate three possibilities first: Codeac cannot compute a clean diff, Codeac is configured not to render it, or Codeac is showing a stale or truncated result. Start with merge-conflict state and the exact panel message, because those two checks explain most cases without changing production state.

Assume a current Codeac deployment with access to the repository and, for cache or log checks, the admin console. Exact menu names, configuration keys, and size limits vary by Codeac version, so confirm key names against your deployment’s configuration reference before editing production settings.

Recognizable condition and likely causes

Diff Highlight is the Codeac view that renders changed lines, usually grouped into hunks. A hunk is one contiguous block of added, removed, or context lines. When this panel is empty, partial, or outdated, the cause is usually one of the following.

Recognizable condition	Likely cause	Fast diagnostic
Panel is empty, but GitHub shows changed files	Pull request is in a merge-conflict state, so Codeac cannot compute a clean diff	Check GitHub mergeability; look for CONFLICTING or DIRTY state
Panel says ‘Diff too large’ or renders only the first files	Pull request exceeds Codeac’s diff size or file-count limit	Compare Codeac’s rendered file count with GitHub’s Files changed count
Panel shows an old snapshot after new commits	Diff cache is stale or corrupted	Hard refresh does not help; admin logs mention cache errors
Diff works on other branches but not this one	Configuration disables diff rendering globally or for the branch	Repository config contains diff.enabled: false or a branch override
Some files never appear in the diff	Large binary blobs are skipped by Codeac’s diff engine	PR file list contains large or binary files; GitHub shows them, Codeac omits them

Ordered checks before changing anything

1. Confirm the symptom is Codeac-specific. Open the same pull request on GitHub and select Files changed. If GitHub also shows no changes, the branch may have no commits or the base branch may be wrong. If GitHub shows changes and Codeac does not, continue.
2. Check merge-conflict status before touching Codeac settings. Run this where GitHub CLI is installed and authenticated. Replace 123, OWNER, and REPO with your values.

# Run on a workstation with GitHub CLI authenticated to the repository
gh pr view 123 --repo OWNER/REPO --json mergeable,mergeStateStatus

Expected check: mergeable is MERGEABLE and mergeStateStatus is not CONFLICTING or DIRTY. If mergeable is UNKNOWN, GitHub is still computing mergeability; retry after a short wait. Risk: the command is read-only, but it requires repository read access.

1. Capture the exact Codeac message. Distinguish ‘No differences’, ‘Diff too large’, a partial file list, or an old snapshot. Record the message, PR URL, and timestamp; this is the minimum evidence needed for escalation.
2. Search the repository configuration for disabled diff rendering. Run this in the repository root. Replace .codeac/ with your actual configuration path.

# Read-only search in the repository root
rg -n 'diff\.enabled|diff\.render' .codeac/ 2>/dev/null || grep -R -n -E 'diff\.(enabled|render)' .codeac/

Expected check: a line such as diff.enabled: false, or a branch-specific override targeting the PR branch. Risk: none beyond reading files, but the configuration directory may differ in your deployment.

1. Measure PR size and binary content. In GitHub, open Files changed and note the total file count and any large or binary files. If Codeac stops after a fixed number of files, the PR is probably over the limit.
2. Check Codeac admin logs last. Look for entries referencing cache corruption, stale snapshots, or diff size limits. This often requires admin console permissions and should be done before any cache invalidation.

Fixes tied to the finding

Merge conflict blocks diff computation

If GitHub reports the PR as conflicting, resolve the conflicts on the PR branch, push the resolution, and confirm GitHub reports the PR as mergeable. Codeac generally needs a clean merge base before it can render a reliable diff. Rollback: if the conflict resolution was wrong, revert the resolution commit rather than force-pushing a shared branch without coordination.

Diff rendering disabled in configuration

If the search finds rendering disabled, change the flag to true. The exact key may vary, but the pattern is the same.

# Illustrative only: confirm the exact key in your Codeac version
diff:
  enabled: false

Change it to enabled: true, commit the configuration change, and reload or restart Codeac if your deployment requires it. If your version supports branch overrides, inspect the same file for entries that target the PR branch. Rollback: restore the previous value and redeploy, but understand that disabling diff rendering can hide real changes from reviewers.

Stale or corrupted diff cache

If the panel shows an old snapshot and logs mention cache problems, invalidate the diff cache from the Codeac admin console. Cache invalidation removes derived diff data so Codeac recomputes it. Treat this as a state-changing operation: ensure network connectivity, avoid peak review windows, and warn reviewers that diffs may be temporarily unavailable. Rollback: if your platform exposes cache snapshots, keep the previous snapshot until the recomputed diff is verified; if it does not, there may be no safe rollback, so use a maintenance window.

Pull request exceeds the diff size limit

If the panel says the diff is too large, split the pull request into smaller stacked PRs, move generated artifacts out of the review path, or ask a Codeac administrator whether the limit can be raised for the repository. Do not disable diff rendering just to make the panel render; that hides the review problem instead of fixing it.

Large binary files are skipped by design

If only binary or very large files are missing, Codeac may be omitting them intentionally. Confirm the behavior with the repository owner or Codeac administrator before treating it as a bug. For large binaries, consider Git LFS, which stores a pointer in Git and the file content elsewhere, or attach the binary to the PR and describe the change in the PR body.

Escalate when these conditions appear

• The PR is under the documented size limit but Codeac still reports ‘Diff too large’.
• Binary omission contradicts your team’s documented review policy.
• Admin logs show repeated cache corruption, or cache invalidation would affect production reviewers.
• Multiple users see the same empty or stale diff on the same PR.
• The fix requires an admin-only configuration change and you have no tested rollback plan.

When escalating, include the PR URL, Codeac version, exact panel message, GitHub mergeability result, redacted configuration snippet, relevant log timestamps, and the checks you already performed.

Limitations and a practical result check

Codeac versions differ in configuration keys, admin console layout, cache behavior, and diff limits. Binary skipping and size limits may be intentional rather than defects. The checks above are diagnostic, not a guarantee that every empty panel has a user-fixable cause.

Practical check: after each fix, open the same PR in a fresh private browser window and confirm the Diff Highlight panel lists changed files and hunks. Compare the rendered file count with GitHub’s Files changed count. If GitHub shows 12 changed files and Codeac renders 12 with no ‘too large’ or ‘No differences’ message, the immediate failure is resolved. If the counts still differ, capture both counts and escalate with that specific mismatch.