Managing Bazel

Bazel Build System Management Skill

Manage and analyze Bazel workspaces, build targets, dependencies, and caching.

MANDATORY: Discovery-First Pattern

Always check current Bazel workspace and build configuration before modifying targets.

Phase 1: Discovery

#!/bin/bash

echo "=== Workspace Configuration ==="
cat WORKSPACE 2>/dev/null | head -20 || cat WORKSPACE.bazel 2>/dev/null | head -20
cat MODULE.bazel 2>/dev/null | head -20

echo ""
echo "=== .bazelrc Configuration ==="
cat .bazelrc 2>/dev/null | head -15

echo ""
echo "=== Bazel Version ==="
bazel version 2>/dev/null | head -3

echo ""
echo "=== Top-Level Packages ==="
ls */BUILD */BUILD.bazel 2>/dev/null | head -15

Phase 2: Analysis

#!/bin/bash

echo "=== All Build Targets ==="
bazel query '//...' 2>/dev/null | head -20

echo ""
echo "=== Target Types Summary ==="
bazel query '//...' --output=label_kind 2>/dev/null | awk '{print $1}' | sort | uniq -c | sort -rn | head -10

echo ""
echo "=== External Dependencies ==="
bazel query 'deps(//...)' --output=label 2>/dev/null | grep '@' | sed 's|//.*||' | sort -u | head -10

Output Rules

• TOKEN EFFICIENCY: Target <=50 lines per output
• Summarize target counts by rule type
• List external dependencies concisely
• Report build timing from profiles

Common Operations

Dependency Graph Query

#!/bin/bash
TARGET="${1:?Target required (e.g., //src:main)}"
echo "=== Dependencies for $TARGET ==="
bazel query "deps($TARGET)" --output=label 2>/dev/null | head -20
echo ""
echo "=== Reverse Dependencies ==="
bazel query "rdeps(//..., $TARGET)" --output=label 2>/dev/null | head -10

Build Performance Profile

#!/bin/bash
echo "=== Build Profile ==="
bazel build //... --profile=/tmp/bazel_profile.json 2>/dev/null
cat /tmp/bazel_profile.json 2>/dev/null | jq '{
  total_duration: .traceEvents[-1].ts,
  critical_path: [.traceEvents[] | select(.cat == "critical path") | .name] | .[0:5]
}' 2>/dev/null

Safety Rules

• Never run bazel clean --expunge without understanding the full rebuild cost
• Test BUILD file changes with bazel build --check_visibility before committing
• Remote execution credentials must be stored in CI secrets, not in .bazelrc
• Review external dependency updates carefully -- Bazel pins exact versions for reproducibility

Output Format

Present results as a structured report:

Managing Bazel Report
═════════════════════
Resources discovered: [count]

Resource       Status    Key Metric    Issues
──────────────────────────────────────────────
[name]         [ok/warn] [value]       [findings]

Summary: [total] resources | [ok] healthy | [warn] warnings | [crit] critical
Action Items: [list of prioritized findings]

Target ≤50 lines of output. Use tables for multi-resource comparisons.

Anti-Hallucination Rules

1. NEVER assume resource names — always discover via CLI/API in Phase 1 before referencing in Phase 2.
2. NEVER fabricate metric names or dimensions — verify against the service documentation or --help output.
3. NEVER mix CLI commands between service versions — confirm which version/API you are targeting.
4. ALWAYS use the discovery → verify → analyze chain — every resource referenced must have been discovered first.
5. ALWAYS handle empty results gracefully — an empty response is valid data, not an error to retry.

Counter-Rationalizations