/debug

name: debug
description: 'Investigation-first debugging — gather evidence, form confirmed root-cause hypothesis, hand off to fix mode with diagnosis file. TRIGGER when: user reports a symptom or failing test with Python traceback, or asks to investigate a runtime/CI failure with reproducible evidence; phrases: "debug this failure", "why is X broken", "find the root cause of <error>", "investigate this CI failure". SKIP when: pure config quality issues (use `/foundry:audit`); broad system-wide diagnosis without traceback (use `/foundry:investigate`); user already knows the fix (use `/develop:fix`); non-Python project.'
argument-hint: '<symptom or issue # (plain 123 or #123)> [--issue <N>] [--repo <owner/repo>] [--no-challenge] [--challenge] [--team] [--worktree] [--ci-run <run-id-or-url>] [--codemap] [--no-codemap] [--keep "<items>"]'
effort: high
allowed-tools: Read, Write, Bash, Grep, Agent, TaskList, TaskCreate, TaskUpdate, AskUserQuestion, EnterWorktree, ExitWorktree
disable-model-invocation: true

<objective>

Investigation-first debugging. Gather evidence, trace data flow, form confirmed root-cause hypothesis, hand off to fix mode.

NOT for: production incidents without any CI run ID or local traceback (use `/foundry:investigate` (requires foundry plugin) for triage); `.claude/` config issues (use `/foundry:audit` (requires foundry plugin)); non-Python projects (JS/TS/Go/Rust) — toolchain assumes pytest; use language-native toolchain instead. CI-only failures ARE supported — pass `--ci-run <run-id or URL>` to use GitHub Actions logs as evidence source.

**Issue ID routing note**: issue mode selected when `--issue` flag present, or when argument (after other flags stripped) is a pure run of digits with an optional `#` prefix (e.g. `123` or `#123`). No numeric threshold. Pass `--issue <N>` to force issue mode for any argument.

</objective>

<compaction>

• Key boundary: after Steps 1+2 — evidence gathered and pattern analysis complete, before hypothesis gate (Step 3).
• Preserve: debug mode, CI run ID if set, evidence signals (issue body, test path), tried-hypotheses ledger (candidate causes + verdicts — refuted/ruled-out/open), --keep items.
• Refresh also after any Step 3 probe that rules out a hypothesis — so post-compact gate does not re-test refuted causes (loop guard).

</compaction>

<workflow>

<!-- Agent resolution: see _DEV_SHARED/agent-resolution.md (mounted by develop plugin init) -->

Agent Resolution

export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
_DEV_SHARED=$(python "${CLAUDE_PLUGIN_ROOT:-plugins/cc_develop}/bin/dev_shared_resolve.py" 2>/dev/null)  # timeout: 5000
[ -z "$_DEV_SHARED" ] && _DEV_SHARED="plugins/cc_develop/skills/_shared"
echo "$_DEV_SHARED" > "${TMPDIR:-/tmp}/dev-shared-${CSID}"  # cold resolve — every later block warm-reads this
# loads: compaction-contract.md
cat "$_DEV_SHARED/agent-resolution.md"

Contains: foundry check + fallback table. If foundry not installed: substitute each `foundry:X` with `general-purpose` per table. Agents this skill uses: `foundry:sw-engineer`, `foundry:challenger`.

export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
IFS= read -r _DEV_SHARED < "${TMPDIR:-/tmp}/dev-shared-${CSID}" 2>/dev/null || _DEV_SHARED=""  # timeout: 5000
[ -z "$_DEV_SHARED" ] && _DEV_SHARED="plugins/cc_develop/skills/_shared"
cat "$_DEV_SHARED/task-hygiene.md"

Project Detection

export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
IFS= read -r _DEV_SHARED < "${TMPDIR:-/tmp}/dev-shared-${CSID}" 2>/dev/null || _DEV_SHARED=""  # timeout: 5000
[ -z "$_DEV_SHARED" ] && _DEV_SHARED="plugins/cc_develop/skills/_shared"
cat "$_DEV_SHARED/runner-detection.md"

Sets `$TEST_CMD` (full suite) and `$PYTEST_CMD` (pytest flags). Run at skill start.

**Language preflight gate**: detect project language; adjust test runner accordingly.

# timeout: 5000
LANG_HINT="python"
if [ ! -f "pyproject.toml" ] && [ ! -f "setup.py" ] && [ ! -f "setup.cfg" ] && [ ! -f "Pipfile" ]; then
    if [ -f "package.json" ]; then LANG_HINT="node"
    elif [ -f "go.mod" ]; then LANG_HINT="go"
    elif [ -f "Cargo.toml" ]; then LANG_HINT="rust"
    fi
fi

If `LANG_HINT` not `python`: invoke `AskUserQuestion` — "Non-Python project detected (`$LANG_HINT`). Toolchain assumes pytest. How to proceed?" · (a) **Abort** — use language-native runner · (b) **Continue** — repo also has Python sources. On Abort: stop.

**Checkpoint**: debug = investigation only — no code changes. `.plans/active/debug_<slug>.md` (written in Step 4) serves as implicit session state. No `.developments/` checkpoint needed.

Flag parsing

Parse flags into actual shell variables (not prose) so downstream blocks see correct values:

export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
python "${CLAUDE_PLUGIN_ROOT:-plugins/cc_develop}/bin/extract-keep-flag.py" dev-debug "$ARGUMENTS"  # timeout: 5000 — parses --keep, clears stale contract
rm -f "${TMPDIR:-/tmp}/dev-debug-hypotheses-${CSID}"  # timeout: 3000

# timeout: 10000
python "${CLAUDE_PLUGIN_ROOT:-plugins/cc_develop}/bin/dev_parse_args.py" \
    --skill debug --write-files "$ARGUMENTS"
# URL normalization + log fetching: §URL Normalization in ci-log-extract.md

Worktree isolation

> loads: worktree-isolation.md

When `--worktree` set, run the investigation in an isolated git worktree so reproduction attempts (repro scripts, temp edits) can never mutate the main sources — **before** codemap detection or Step 1.

# timeout: 5000
export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
IFS= read -r WORKTREE_ENABLED < "${TMPDIR:-/tmp}/dev-debug-worktree-${CSID}" 2>/dev/null; [ "$WORKTREE_ENABLED" = "true" ] || WORKTREE_ENABLED=false

export CSID="${CLAUDE_CODE_SESSION_ID:-$PPID}"
IFS= read -r _DEV_SHARED < "${TMPDIR:-/tmp}/dev-shared-${CSID}" 2>/dev/null || _DEV_SHARED=""  # timeout: 5000
[ -z "$_DEV_SHARED" ] && _DEV_SHARED="plugins/cc_develop/skills/_shared"
cat "$_DEV_SHARED/worktree-isolat