fix: read governance debug log tail in binary mode

[thepastaclaw]

Summary

• fix feature_governance_cl.py log tail polling to seek debug.log
  in binary mode
• decode the tailed bytes after reading so the seek offset stays valid
  for the stream mode
• preserve the existing behavior of scanning only the last 100 KiB for
  the expected governance tip message

Context

This is a follow-up for a valid review finding from merged PR #7258:
#7258 (comment)

Upstream develop currently opens debug.log in text mode but computes
the seek position with a binary offset. The final fix here uses a fully
binary tail read and decodes afterward, which avoids both mixed-mode seek
problems and text-stream offset arithmetic.

Validation

• python3 -m py_compile test/functional/feature_governance_cl.py
• pre-PR code review gate verdict: ship

I did not run feature_governance_cl.py end-to-end because this worktree
does not have built dashd/test binaries available, and building Dash
Core would be disproportionate for this narrowly scoped Python
functional-test fix.

[thepastaclaw]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[github-actions]

✅ No Merge Conflicts Detected

This PR currently has no conflicts with other open PRs.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 8e51eb01-5841-4f07-b375-926cd6f514c5

📥 Commits

Reviewing files that changed from the base of the PR and between 45d3b21 and 0293c6d.

📒 Files selected for processing (1)

• test/functional/feature_governance_cl.py

🚧 Files skipped from review as they are similar to previous changes (1)

• test/functional/feature_governance_cl.py

---

Walkthrough

The governance test's log-verification helper now opens the debug log in binary mode, seeks to the last 100 KiB, reads raw bytes, decodes them with UTF-8 using replacement for invalid sequences, and then searches the decoded string for the existing CGovernanceManager::UpdatedBlockTip -- nCachedBlockHeight: {tip_height} substring. The change adjusts how encoding/decoding errors are handled when scanning the log without altering the substring check or overall control flow.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title clearly and concisely summarizes the main change: fixing the governance debug log tail reading to use binary mode instead of mixed text/binary mode.
Description check	✅ Passed	The pull request description is fully related to the changeset, explaining the problem (mixed-mode seek issues), the solution (binary read with post-decode), and the context (follow-up to PR #7258).
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

Review ran into problems

🔥 Problems

Timed out fetching pipeline failures after 30000ms

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Review rate limit: 7/8 reviews remaining, refill in 7 minutes and 30 seconds.}

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[thepastaclaw]

✅ Review complete (commit 0293c6d)

[thepastaclaw]

Code Review

I re-checked the diff directly and did not find a correctness issue to block this PR. The patch fixes the original mixed-mode seek bug by computing the tail offset and performing the seek in the same stream mode that is later read, and the helper rename to debug_log_size() makes the adjacent test-framework call sites explicit about that contract.

Reviewed commit: 0293c6d

[knst]

LGTM 0293c6d

p.s. CI succeed, I have no objections