Nightshift: consider priority labels when ordering issues

[mickume]

Feature Request

Nightshift should consider priority:high, priority:medium, and priority:low labels when determining issue processing order, so that high-priority issues are worked on before lower-priority ones.

Current Behavior

Nightshift fetches issues with the af:fix label and orders them by:

1. Issue number (ascending — oldest first)
2. Explicit text dependencies (depends on #N, blocked by #N)
3. GitHub cross-reference metadata
4. AI triage recommendations (for batches of 3+)
5. Topological sort with tie-breaking by issue number

Priority labels on issues are completely ignored. A priority:high issue created after a priority:low issue will always be processed second.

Desired Behavior

After dependency ordering is resolved, issues at the same dependency depth should be sorted by priority label:

1. priority:high — processed first
2. priority:medium (or no priority label) — default
3. priority:low — processed last

Suggested Implementation

The change would be in the topological sort tie-breaking logic in packages/agentfox/agentfox/nightshift/dep_graph.py (lines 70-83). Currently ties are broken by ascending issue number. Instead, ties should be broken by:

1. Priority label (high > medium/none > low)
2. Issue number (ascending, as current fallback)

The priority label would need to be extracted from the issue's labels list during the ordering phase in packages/agentfox/agentfox/nightshift/engine.py.

Affected Files

• packages/agentfox/agentfox/nightshift/dep_graph.py — tie-breaking in topological sort
• packages/agentfox/agentfox/nightshift/engine.py — pass label info into the ordering pipeline
• packages/agentfox/agentfox/platform/labels.py — define priority label constants

[mickume]

Change to the above suggested implementation:

• First order sorting should happen as described in "Desired Behavior", replace the current implementation's step 1) sorting by Issue number (ascending — oldest first).

The other steps of the current implementation can remain "as-is". no other changes are needed IMO

[mickume]

Starting fix session on branch fix/632-nightshift-consider-priority-labels-when-ordering-issues... (run: 20260626_143018_9f511b)

[mickume]

Triage Report

Summary: The topological sort tie-breaking logic in dep_graph._kahn_sort only sorts the ready queue by ascending issue number (via sorted() on initialisation and bisect.insort on subsequent insertions). It has no awareness of the labels field on IssueResult objects. Because the full IssueResult list (which does carry labels) is already passed to build_graph, the label information is available but never threaded into _kahn_sort. The fix requires: (1) defining priority label constants in labels.py, (2) computing a priority-rank map from the issue list inside build_graph, and (3) replacing the plain numeric sort key in _kahn_sort with a composite (priority_rank, issue_number) key.

Affected files:

• packages/agentfox/agentfox/platform/labels.py
• packages/agentfox/agentfox/nightshift/dep_graph.py

Acceptance Criteria

AC-1: Priority label name constants are defined in labels.py.

• Preconditions: The file packages/agentfox/agentfox/platform/labels.py exists and contains the existing LABEL_FIX, LABEL_FIXED, etc. constants.
• Expected: Module exports three new string constants: LABEL_PRIORITY_HIGH = "priority:high", LABEL_PRIORITY_MEDIUM = "priority:medium", and LABEL_PRIORITY_LOW = "priority:low".
• Assertion: Run grep -n 'LABEL_PRIORITY' packages/agentfox/agentfox/platform/labels.py and confirm all three constants are present with the exact string values priority:high, priority:medium, and priority:low.

AC-2: Independent issues (no dependency edges) are ordered high > medium/none > low by priority label.

• Preconditions: build_graph receives three IssueResult objects with labels ("priority:low",), (), and ("priority:high",) respectively, and an empty edges list.
• Expected: build_graph returns the high-priority issue number first, the unlabelled (medium) issue second, and the low-priority issue last, regardless of their issue numbers.
• Assertion: Unit test: issues = [IssueResult(30, ..., labels=("priority:low",)), IssueResult(10, ..., labels=()), IssueResult(20, ..., labels=("priority:high",))]; order = build_graph(issues, []); assert order.index(20) < order.index(10) < order.index(30).

AC-3: Dependency edges take precedence over priority ordering.

• Preconditions: A priority:low issue A is a declared prerequisite of a priority:high issue B (edge A→B). build_graph receives both issues and that edge.
• Expected: Issue A appears before issue B in the output even though B has higher priority, because A must be resolved first.
• Assertion: Unit test: issues = [IssueResult(1, ..., labels=("priority:low",)), IssueResult(2, ..., labels=("priority:high",))]; edges = [DependencyEdge(1, 2, "explicit", "")]; order = build_graph(issues, edges); assert order.index(1) < order.index(2).

AC-4: Issue number is the secondary tie-breaker within the same priority tier.

• Preconditions: Two issues both carry priority:high and have no dependency edges between them.
• Expected: The lower-numbered issue appears first (existing tie-breaking rule preserved).
• Assertion: Unit test: issues = [IssueResult(50, ..., labels=("priority:high",)), IssueResult(10, ..., labels=("priority:high",))]; order = build_graph(issues, []); assert order == [10, 50].

AC-5: Issues without any priority label are treated as medium priority.

• Preconditions: build_graph receives one issue labelled priority:high (number 20), one issue with no priority label (number 10), and one labelled priority:low (number 30). No edges.
• Expected: Order is [20, 10, 30] — high first, unlabelled second (medium default), low last.
• Assertion: Unit test asserting build_graph([IssueResult(20,...,labels=("priority:high",)), IssueResult(10,...,labels=()), IssueResult(30,...,labels=("priority:low",))], []) == [20, 10, 30].

(run: 20260626_143018_9f511b)

[mickume]

Fix Review Report

Overall verdict: PASS

Summary: All five acceptance criteria are satisfied. The implementation adds three priority label constants to labels.py (NS-REQ-1), modifies build_graph in dep_graph.py to build a priority rank map (high=0, medium/none=1, low=2) and passes it to _kahn_sort which uses (priority_rank, issue_number) as the composite sort key (NS-REQ-2, NS-REQ-4, NS-REQ-5). Dependency edges still take precedence over priority ordering via Kahn's in-degree constraints (NS-REQ-3). All 37 tests in test_fix_ordering.py pass including 5 new priority-specific tests. Lint passes on all changed files. The single test failure in the full unit suite (test_full_test_suite_passes) is a pre-existing subprocess timeout in an unrelated meta-test, not a regression from this change. All 32 pre-existing tests continue to pass.

Per-criterion verdicts

• ✅ AC-1: PASS
  • Evidence: grep confirms LABEL_PRIORITY_HIGH = "priority:high", LABEL_PRIORITY_MEDIUM = "priority:medium", and LABEL_PRIORITY_LOW = "priority:low" at lines 32-34 of packages/agentfox/agentfox/platform/labels.py. Test test_ts_ns_1_priority_label_constants_exported imports all three and asserts their exact string values — PASSED.
• ✅ AC-2: PASS
  • Evidence: Test test_ts_ns_2_independent_issues_ordered_high_medium_low constructs three IssueResult objects (issue 30 with priority:low, issue 10 unlabelled, issue 20 with priority:high) with empty edges and asserts order.index(20) < order.index(10) < order.index(30) — PASSED. The implementation in build_graph builds a priority_map (high=0, medium/none=1, low=2) and passes it to _kahn_sort, which uses (priority_rank, issue_number) as the sort key.
• ✅ AC-3: PASS
  • Evidence: Test test_ts_ns_3_dependency_edges_take_precedence_over_priority creates issue 1 (priority:low) as a prerequisite of issue 2 (priority:high) via DependencyEdge(1, 2, ...) and asserts order.index(1) < order.index(2) — PASSED. Kahn's algorithm respects in-degree constraints (dependency edges) before tie-breaking by priority.
• ✅ AC-4: PASS
  • Evidence: Test test_ts_ns_4_issue_number_is_secondary_tiebreaker creates two issues (50 and 10) both with priority:high and no edges, then asserts order == [10, 50] — PASSED. The sort key (priority_rank, issue_number) ensures lower-numbered issue comes first within the same priority tier.
• ✅ AC-5: PASS
  • Evidence: Test test_ts_ns_5_unlabelled_treated_as_medium creates issue 20 (priority:high), issue 10 (no priority label), and issue 30 (priority:low) with no edges, and asserts order == [20, 10, 30] — PASSED. The priority_map assigns rank 1 (medium) to issues without a priority label via the else branch.

(run: 20260626_143018_9f511b)

[mickume]

Fix complete on branch fix/632-nightshift-consider-priority-labels-when-ordering-issues. Changes have been merged into main. (run: 20260626_143018_9f511b)