Harness issue debug

Issue Debug

Opens a live, interactive repair session on a piece of work that stopped: a harness feature marked failed, or a Linear issue the external runner parked after exhausting its self-heal attempts. This skill is the hands-on counterpart to harness-issue-prep: where harness-issue-prep fixes a spec before implementation starts, harness-issue-debug fixes an implementation (or the spec behind it) after something already went wrong.

Mode is selected by the shape of the argument:

• F0NN (matches a feature id in .harness/features.json): local mode.
• An issue key matching ^[A-Z]+-[0-9]+$ (for example ENG-123): runner mode.

If the argument matches neither shape, ask which mode the user means before proceeding.

Local Mode (F0NN)

Step 1: Load context. Read the feature from .harness/features.json and surface, in one block, everything a debugging session needs before touching code:

Feature F0NN: [description]
Status: failed
Failure reason: [failure_reason]
Notes: [notes]
Correction cycles: [correction_cycles]
Scope: [scope]

Step 2: Check out the branch. If notes names a branch, check it out. If it does not, ask the user which branch to use before continuing; do not guess.

Step 3: Establish the baseline. Run ./.harness/init.sh to confirm the checked-out branch builds and to see the current failure state directly, not secondhand through failure_reason.

Step 4: Iterate the fix. This is a normal interactive session: write a failing test, implement, confirm green, refactor, repeat. No special ceremony beyond the harness's usual TDD discipline applies here; the only thing that distinguishes this session from any other feature work is that it starts from a known failure instead of a blank feature.

Step 5: Exit route. Exactly one of three, decided with the human present:

• Fixed and the human is satisfied. Set status to "pending", not "passing"; the quality gate (verify-task-quality.sh on TaskCompleted) is what earns "passing", and this skill does not shortcut it. Clear failure_reason.
• The spec was the real problem, not the code. Run harness-issue-prep F0NN to fix the description before any further implementation attempt.
• Abandoned this session. Keep status: "failed". Update failure_reason with what was learned this round, even if the answer is still "unresolved": a stale failure_reason from a prior attempt is worse than an updated one that says what was ruled out.

Runner Mode (ISSUE-KEY)

Step 1: Fetch the issue. Discover the connected Linear MCP's tools at runtime; never hardcode tool names (the harness's spec-gate tooling makes this same choice for the same reason: MCP surfaces change across integrations and versions). Fetch the issue's description and comments.

Step 2: Find the park bundle. Locate the newest comment whose first line is the literal marker vv-harness-park v1. Parse its fenced json block per the ${CLAUDE_PLUGIN_ROOT}/schemas/readiness-stamp.md contract: branch, confirmed_findings, heal_attempts, transcript_hint.

If no such comment exists, or it exists but the json does not parse: say so plainly, offer to fall back to local-style manual debugging against the issue (ask for the branch, then proceed as in Local Mode Steps 2 through 4), and post no resolution comment. A missing or broken park bundle is not itself an error to fix silently; it means the runner never successfully parked this issue, and the human should know that before debugging blind.

Step 3: Get the repo locally. If the repo is not already cloned on this machine, ask the user for its local path, or offer to clone it. Then check out branch from the park bundle.

Step 4: Present the worklist. Show confirmed_findings as the starting worklist for the session (each finding names a gate, a rule id, and evidence). Use transcript_hint if the human wants to see the runner's prior attempts before continuing. heal_attempts tells you how many self-heal rounds the runner already burned; treat a high count as a signal that the earlier findings may need more than a local patch.

Step 5: Iterate the fix. Same as Local Mode Step 4: normal TDD, interactive, no extra ceremony.

Step 6: Post the resolution. When the session concludes, post a comment on the issue per the vv-harness-debug-resolution v1 contract in ${CLAUDE_PLUGIN_ROOT}/schemas/readiness-stamp.md: line 1 is the literal marker vv-harness-debug-resolution v1, followed by one fenced json block. Disposition is exactly one of:

• resume: the branch is pushed and the confirmed findings are addressed. This is the only disposition that authorizes the runner to act again, so it is the only one that carries an hmac. Compute it with the same recipe and key resolution chain (Keychain, then VV_HARNESS_STAMP_KEY_FILE, then the discouraged VV_HARNESS_STAMP_KEY; full rationale in ${CLAUDE_PLUGIN_ROOT}/schemas/readiness-stamp.md's HMAC recipe) as the readiness stamp:

  python3 - "$SPEC_HASH" "$BRANCH" "resume" <<'PYEOF'
  import hmac
  import hashlib
  import os
  import sys
  from subprocess import CalledProcessError, DEVNULL, check_output
  
  
  def get_stamp_key():
      # Same chain as harness-issue-prep's Step 7 -- see that skill's own
      # comments, or schemas/readiness-stamp.md's HMAC recipe, for the full
      # rationale behind each source and the exit-code contract below.
      try:
          key = check_output(
              ["security", "find-generic-password", "-s", "vv-harness-stamp", "-w"],
              stderr=DEVNULL,
          ).strip()
          if key:
              return key
      except (CalledProcessError, FileNotFoundError, OSError):
          pass
      key_file = os.environ.get("VV_HARNESS_STAMP_KEY_FILE")
      if key_file:
          try:
              mode = os.stat(key_file).st_mode & 0o777
          except OSError as exc:
              print(f"VV_HARNESS_STAMP_KEY_FILE={key_file} unreadable: {exc}", file=sys.stderr)
              sys.exit(1)
          if mode != 0o600:
              print(
                  f"VV_HARNESS_STAMP_KEY_FILE={key_file} has mode {oct(mode)}, refusing -- "
                  f"fix with: chmod 600 {key_file}",
                  file=sys.stderr,
              )
              sys.exit(1)
          with open(key_file, "rb") as fh:
              key = fh.read().strip()
          if key:
              return key
      env_key = os.environ.get("VV_HARNESS_STAMP_KEY")
      if env_key:
          return env_key.encode("utf-8")
      return None
  
  
  key = get_stamp_key()
  if key is None:
      sys.exit(2)
  msg = "|".join(sys.argv[1:4]).encode("utf-8")
  print(hmac.new(key, msg, hashlib.sha256).hexdigest())
  PYEOF
  

  spec_hash here is the value from the issue's current vv-harness-readiness-stamp v1 comment, the same hash the original stamp authorized; do not compute a new one. Exit code 1 means a configured key file has the wrong permissions -- report the exact chmod fix from stderr; do not post resume and do not silently fall back to a weaker source. Exit code 2 means no key was found from any of the three sources -- do not post a resume disposition; report the failure and offer reprep or abandon instead.

• reprep: the spec, not the code, turned out to be the problem. Post the comment with no hmac, then run harness-issue-prep ISSUE-KEY to fix the spec and re-stamp it.

• abandon: the runner should stop trying and a human decides the issue's fate. Post the comment with no hmac.

Runner-side consumption of this comment (deciding to act on a resume, reconciling its own state) is out of scope for this skill; the contract in ${CLAUDE_PLUGIN_ROOT}/schemas/readiness-stamp.md is the deliverable, not a running consumer.

Degradation

Situation	End state
Argument matches neither F0NN nor an issue key	Ask the user which mode is intended before doing anything
Local mode, notes has no branch	Ask for the branch; do not guess or invent one
Runner mode, no park comment found	Say so, offer local-style manual debugging, post no resolution comment
Runner mode, park comment json does not parse	Same as above: report it, fall back, post nothing
Runner mode, repo not cloned and user has no path	Ask again or stop; do not clone speculatively
Runner mode, resume disposition but no key resolved from any source (exit 2)	Do not post resume; report the failure and offer reprep or abandon
Runner mode, resume disposition but key file has wrong permissions (exit 1)	Do not post resume; report the exact chmod fix, do not silently fall back