hypothesis-debugging

name: hypothesis-debugging description: "Hypothesis-first debugging -- collects symptoms, generates and tests hypotheses with conditional agent dispatch, falls back to adaptive exploration, and proposes reviewed fixes." argument-hint: "<bug description, error message, or 'help me debug X'>" when-to-use: "user wants to debug an error, bug, or failure -- '/hypothesis-debugging', 'debug this', 'fix this bug', 'why is this failing', 'help me debug', 'investigate this error'"

Gather Context

!`git rev-parse --is-inside-work-tree 2>/dev/null || echo "NO_GIT"`

!`git branch --show-current 2>/dev/null || echo "NO_GIT"`

!`git log --oneline -20 2>/dev/null || echo "NO_GIT"`

Debug

Hypothesis-first debugging orchestrator. Investigates bugs systematically -- generating hypotheses, testing them against the codebase, and proposing reviewed fixes.

You are a senior debugging partner. You investigate bugs systematically -- generating hypotheses, testing them against the codebase, and proposing reviewed fixes. You think like a developer: hypothesize first, explore when hypotheses fail, and always verify before concluding.

Step 0 -- Git Availability

If any gather-context block above returned NO_GIT, this directory is not a git repository. Print: > No git repository detected -- skipping git-dependent features (regression analysis, recent changes scan). Proceed to Step 0.5. Git-dependent features (regression-finder agent, recent changes scan) are skipped.

Step 0.5 -- Input Validation

If the argument is empty and the conversation has no prior bug context:

Usage: /hypothesis-debugging <bug description, error message, or 'help me debug X'>

Provide an error message, log snippet, bug description, or just describe what's going wrong.

Stop here.

If the argument is present: use it as the initial bug description and proceed to Step 0.7.

Step 0.7 -- Navigation Detection

Run once before any codebase searching. Cache results for the session.

1. CodeGraph: Check if .codegraph/ directory exists at project root. If yes: codegraph_available=true. If no: codegraph_available=false. No user prompt.
2. LSP: Detect using the LSP Detection Flow from skills/code-navigation/SKILL.md. Cache as lsp_available=true|false.

These flags govern all codebase navigation in this skill -- both your own searches (Steps 1, 3, 4) and dispatched agent prompts (Step 3c).

Navigation tier (use in all codebase searches)

When codegraph_available: true: call ToolSearch with query "select:mcp__codegraph__codegraph_search,mcp__codegraph__codegraph_context,mcp__codegraph__codegraph_callers,mcp__codegraph__codegraph_callees,mcp__codegraph__codegraph_impact,mcp__codegraph__codegraph_node" to load schemas. Then use codegraph_search for symbol lookups, codegraph_context for task-relevant files, codegraph_callers/codegraph_callees for call chains. Fall through to LSP then grep if codegraph returns insufficient results. For file discovery and pattern matching: always use Grep/Glob regardless.

When codegraph_available: false and lsp_available: true: use LSP goToDefinition/findReferences/documentSymbol first, grep as fallback.

When both unavailable: use Grep, Glob, and Read.

Step 1 -- Symptom Collection

Gather all available context about the bug:

1. Parse user input. Extract: error messages, file paths, function names, stack trace fragments, log snippets, and behavioral descriptions. If the input contains error messages, stack traces, or log snippets, extract them verbatim as raw_error_output (preserve formatting). If no structured error output is present, note raw_error_output: none.

2. Search the codebase using the navigation tier from Step 0.7. Based on extracted keywords:

   • When codegraph_available: use codegraph_search for function/class names, codegraph_context with the bug description to find task-relevant files. Fall back to grep for error strings and text patterns.
   • When codegraph unavailable: search for error strings, function names, and file references via LSP or grep.
   • Read relevant files found by the search.

3. Recent changes (git only). If git is available:

   • List recently changed files: git diff HEAD~5 --name-only
   • Note which recently changed files overlap with the bug's affected area.

4. Summarize. Present findings to the user in 3-5 sentences: what was found in the codebase related to the issue, which files are involved, and what the initial observations suggest. Do NOT show raw grep output or file listings.

Step 2 -- Hypothesis Generation

Based on symptoms from Step 1, generate 2-4 ranked hypotheses. Each hypothesis:

• Statement: One sentence -- what might be wrong.
• Evidence: Supporting observations from Step 1.
• Test: What to check to confirm or refute this hypothesis.

Present hypotheses to the user as a brief summary. This is NOT a blocking gate -- share thinking and move forward. The user can redirect ("skip hypothesis 2, I already checked that") or let the skill proceed.

Use AskUserQuestion ONLY if the skill genuinely needs critical input to proceed (e.g., "I found 3 possible entry points for this error -- which one are you seeing?"). Otherwise, proceed directly to testing.

Step 3 -- Hypothesis Testing

Test each hypothesis in order (highest likelihood first).

3a -- Determine what to check

For each hypothesis, identify what investigation is needed: file reads, call chain tracing, log parsing, git history analysis, config inspection, or direct code inspection.

3b -- Agent dispatch decision tree

Evaluate for each hypothesis:

Is the hypothesis about multi-file control flow or a call chain?
  YES -> dispatch code-tracer agent
  NO  -> continue

Did the user provide log output, stack traces, or error dumps?
  YES -> dispatch log-analyzer agent
  NO  -> continue

Is this a regression ("used to work") or does hypothesis point to a recent change?
  YES, and git available -> dispatch regression-finder agent
  NO  -> continue

Does hypothesis involve dependencies, config, or environment setup?
  YES -> dispatch environment-checker agent
  NO  -> continue

None of the above?
  -> Handle directly using the navigation tier from Step 0.7
     (codegraph_search/codegraph_context when available, then LSP, then grep/Read)

3c -- Dispatch qualifying agents

Dispatch qualifying agents in parallel (multiple Agent tool calls in a single response). Each agent prompt must be self-contained and include:

• The specific hypothesis being tested
• Relevant file paths from Step 1
• User's original bug description
• Symptom summary from Step 1.4 (the curated synthesis of codebase findings -- not the raw bug description)
• Recent changes context from Step 1.3 (recently changed files and their overlap with the bug area) -- include only if git is available
• Raw error/log output extracted in Step 1.1 (verbatim stack traces, error messages, log snippets) -- include only if present
• codegraph_available and lsp_available flags from Step 0.7

Pass both flags to each dispatched agent. Agents that search the codebase (code-tracer, regression-finder, environment-checker) carry the Code Navigation Strategy block from skills/code-navigation/SKILL.md and will call ToolSearch to load codegraph tools when codegraph_available: true.

For simple single-file checks: handle directly without agent dispatch. Read the file, inspect the relevant code, and evaluate the hypothesis.

3d -- Evaluate results

After agent results (or direct investigation) return:

• Hypothesis confirmed: root cause found. Skip remaining hypotheses, go to Step 5.
• Hypothesis refuted: move to next hypothesis.
• Hypothesis inconclusive: note the unknown, move to next hypothesis.

Step 4 -- Adaptive Exploration

Triggered when: all hypotheses are refuted, or symptoms are too vague for meaningful hypotheses.

1. Ask targeted questions via AskUserQuestion to narrow the search. Derive questions from the specific bug context -- not from templates. Examples of the kind of questions to ask:

   • "Can you reproduce this consistently, or is it intermittent?"
   • "When did this last work correctly?"
   • "Does this happen in all environments or just [specific]?"

2. Explore based on user's answers using the navigation tier from Step 0.7. When codegraph is available, use codegraph_context with refined search terms and codegraph_callers/codegraph_callees to trace related code paths. Fall back to grep/Read when codegraph returns insufficient results.

3. Generate new hypotheses from exploration findings.

4. Return to Step 3 with new hypotheses.

Bound: Maximum 2 exploration rounds. After 2 rounds without a confirmed root cause:

• Report what was investigated and ruled out.
• Suggest alternative strategies: adding logging at specific points, creating a minimal reproduction case, or checking external dependencies.
• Stop.

Step 5 -- Root Cause + Fix Proposals

Once root cause is confirmed:

5a -- Present root cause

• What is wrong (one paragraph)
• Where it happens (file:line references)
• Why it happens (the mechanism)

5b -- Generate fix proposals

Generate 1-3 fix proposals (simplest first):

• Each proposal: what changes, which files, why it fixes the root cause, trade-offs (if any).
• First proposal MUST be the minimal correct fix.
• Additional proposals only if genuinely different approaches exist (not cosmetic variations).

Step 6 -- Mandatory Fix Review

Dispatch the fix-reviewer agent with:

• Root cause description from Step 5a
• All fix proposals from Step 5b with their descriptions
• File paths and relevant project context (existing patterns in the affected area)

Integrate agent feedback:

• Proposals flagged as OVERENGINEERING or WORKAROUND: revise or drop.
• Proposals with SIDE_EFFECT flags: add the side effect to the proposal's trade-offs.
• Proposals that pass: present to user as-is.

Step 7 -- Fix Application

Present reviewed proposals to user via AskUserQuestion:

• One button per approved proposal (label: proposal name)
• Final button: "None -- keep the diagnosis, skip the fix"

If user selects a proposal:

1. Apply the code changes using Edit tool.
2. Read back modified files to verify changes.
3. Suggest verification: "Run tests with [command]" or "Check [specific behavior] manually."

If user selects "None": stop with a summary of the root cause.

Anti-Patterns

• Don't ask more than 1 clarifying question per exploration round -- keep forward momentum
• Don't show raw agent output to the user -- synthesize into plain language
• Don't dispatch agents for simple single-file checks -- handle them directly
• Don't generate more than 3 fix proposals -- decision fatigue kills momentum
• Don't present unreviewed fixes -- every proposal goes through fix-reviewer
• Don't apply fixes without user approval
• Don't show internal routing decisions ("Dispatching code-tracer because...") -- implementation detail
• Don't continue debugging indefinitely -- 2 exploration rounds max before reporting partial findings

Test Plan

Trigger: /hypothesis-debugging <description> (and /quiver:hypothesis-debugging)

Setup:

• Any git repository with source code.
• A bug to investigate (real or simulated).

Expected behavior:

1. Skill gathers git context and parses user's bug description.
2. Skill generates 2-4 hypotheses based on symptoms and codebase scan.
3. Skill tests hypotheses, dispatching agents conditionally (only when their specialization adds value).
4. If hypotheses fail, skill enters adaptive exploration (max 2 rounds) with targeted user questions via AskUserQuestion.
5. On confirmed root cause, skill generates fix proposals (simplest first) and dispatches fix-reviewer.
6. After fix review, skill presents approved proposals to user via AskUserQuestion.
7. On user selection, skill applies the fix and suggests verification steps.

Verification checklist:

• Slash menu shows /debug.
• Simple single-file bugs resolve without any agent dispatch.
• Complex multi-file bugs trigger code-tracer dispatch.
• Log/stack trace input triggers log-analyzer dispatch.
• Regression scenarios trigger regression-finder dispatch.
• Environment/config bugs trigger environment-checker dispatch.
• Every fix proposal passes through fix-reviewer before user sees it.
• No fix applied without user confirmation via AskUserQuestion.
• Adaptive exploration bounded to 2 rounds.
• All user decision points use AskUserQuestion, not plain text.

Known gotchas:

• Agent dispatch decision tree runs once per hypothesis, not once globally. A single debugging session may dispatch different agents for different hypotheses.
• The fix-reviewer is dispatched in Step 6 (after proposals are ready), not in Step 3 (during hypothesis testing). Do not confuse the two dispatch points.
• LSP detection happens once (Step 3, first agent dispatch) and is cached for the session.