# Principal Systems Engineer — Round 1 Review

**Branch:** `colonyos/when_you_output_followups_in_the_thread_on_slack_a938599349`
**PRD:** `cOS_prds/20260331_190640_prd_you_are_a_code_assistant_working_on_behalf_of_the_engineering_team_the_following.md`
**Commits:** 10 (+1,371 / -24 lines)
**Tests:** 137 pass (test_slack_formatting: 137, test_sanitize: included)

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## Checklist

### Completeness
- [x] FR-1: Task completion messages include description (truncated, sanitized)
- [x] FR-2: Task outline uses bullet formatting (`•` bullets, `+N more` overflow)
- [x] FR-3: Task result summary includes descriptions with cost/duration
- [x] FR-4: Review round messages include finding summaries (3-tier fallback)
- [x] FR-5: Sanitization at all 7 ingress points (`sanitize_untrusted_content` + `sanitize_for_slack`)
- [x] Zero additional LLM calls
- [x] All tasks complete, no TODO/placeholder code

### Quality
- [x] 137 tests pass
- [x] Code follows existing project conventions
- [x] No unnecessary dependencies added
- [x] No unrelated changes included
- [x] Named constants replace magic numbers (`_SLACK_MAX_CHARS`, `_SLACK_TASK_DESC_MAX`, etc.)

### Safety
- [x] No secrets or credentials in committed code
- [x] Sanitization chain: XML stripping → mrkdwn escape → mention neutralization → blockquote neutralization
- [x] Truncation cap at 3,000 chars (well under Slack's 40k limit)
- [x] Error handling for malformed cost/duration with debug logging
- [x] Audit logging when content is neutralized

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## Findings

### Non-blocking

1. **[src/colonyos/orchestrator.py — `_truncate_slack_message`]**: The newline-boundary truncation is good for readability. One edge: if a message is a single extremely long line with no newlines, `rfind("\n")` returns -1 and the fallback does a hard cut at `max_chars - len(indicator)`. This is correct behavior but the hard cut could land mid-emoji or mid-UTF-8 surrogate pair. Practically irrelevant since all formatted messages contain newlines, but worth noting.

2. **[src/colonyos/orchestrator.py — `_extract_review_findings_summary`]**: The state machine's blank-line tolerance logic (`len(findings_lines) < max_findings`) is slightly asymmetric — a blank line *before* any findings have been collected causes a `continue` (tolerated), but after `max_findings` findings are collected, *any* line including a blank breaks out. This is the tighter behavior added in the latest commit and is correct; I just want to note that if the FINDINGS section had interleaved blank lines with >2 findings, only the first 2 would be collected (which is the intended cap anyway). No action needed.

3. **[src/colonyos/orchestrator.py — `_format_review_round_note`]**: The `requested_changes` list changed from `list[str]` to `list[tuple[str, str]]` holding `(reviewer_ref, result_text)`. `result_text` can be large (1000+ words). For a review round with many reviewers requesting changes, you're holding N copies of full review texts in memory simultaneously. At the scale ColonyOS operates (≤7 reviewers), this is negligible — but if reviewer count ever scaled, consider extracting findings eagerly inside the loop rather than carrying full texts.

4. **[src/colonyos/sanitize.py — `sanitize_for_slack`]**: The ordering of sanitization passes matters and is correct: link injection is neutralized *before* mrkdwn escaping, so the URL text doesn't get escaped while still inside `<url|text>` syntax. Good. One minor note: the `_SLACK_MRKDWN_CHARS_RE` escapes backticks, which means task IDs formatted as `` `1.0` `` in the *trusted* template would also be escaped if they accidentally passed through this function. The current code correctly only calls `sanitize_for_slack` on untrusted content (descriptions, findings), not on the template strings — this invariant should be maintained.

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## Operational Assessment

**Debuggability**: Good. The `logger.debug` on sanitization and malformed cost/duration means that if a Slack message looks wrong at 3am, you can crank up log level and see exactly what was neutralized. The three-tier fallback in `_extract_review_findings_summary` (FINDINGS → SYNTHESIS → first line) means you'll always get *something* in the message even if the review output deviates from template.

**Blast radius**: Minimal. Changes are confined to formatting functions that produce display strings. A bug here shows a garbled Slack message — it cannot affect pipeline execution, branch creation, or code generation. The sanitization layer is additive (new function, new call sites) and doesn't modify existing sanitization behavior.

**Race conditions**: None introduced. Formatting functions are pure (no shared mutable state, no I/O beyond logging).

**Failure modes**: The `_truncate_slack_message` function provides a hard upper bound on message size, which prevents the pathological case of a review round with verbose reviewers producing a message that hits Slack's API limit. The `+N more` overflow prevents unbounded growth from large task counts.

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VERDICT: approve

FINDINGS:
- [src/colonyos/orchestrator.py]: `_truncate_slack_message` hard-cut fallback could split mid-character on a single long line with no newlines. Practically irrelevant since all formatted messages contain newlines.
- [src/colonyos/orchestrator.py]: `_format_review_round_note` carries full review texts in memory for all requesting-changes reviewers; negligible at current scale (≤7 reviewers) but consider eager extraction if scale changes.
- [src/colonyos/sanitize.py]: `sanitize_for_slack` escapes backticks — invariant that it's only called on untrusted content (not template strings) must be maintained to avoid breaking `` `task_id` `` formatting.

SYNTHESIS:
This is a well-executed, narrowly-scoped formatting improvement. The architecture is sound: pure formatting functions with no side effects, sanitization applied at content boundaries (not output boundaries), deterministic post-processing of semi-structured LLM output with graceful degradation. The 137-test suite is comprehensive and covers edge cases (overflow, truncation, injection vectors, fallback paths). Named constants replace magic numbers. The blast radius of any bug is limited to display quality — pipeline execution is unaffected. All five functional requirements are implemented with zero new LLM calls. The implementation is production-ready. Ship it.
