Recall — Session & History Archaeology

Search three evidence layers, cheapest first, to answer "have we solved this before?". Stop at the first layer that answers the question.

Usage

phx-recall how did we fix the LiveView form that saved silently?
phx-recall what did we decide about the billing context boundaries?
phx-recall which library did we pick for rate limiting and why?

Iron Laws

1. Cheapest layer first — solution docs (local grep) → git history → session transcripts. Don't fetch sessions when a solution doc answers
2. ONE ccrider fetch = ONE subagent — get_session_messages responses are 3–15KB each. Spawn a subagent per session that writes a summary file and exits; NEVER batch multiple session fetches into one context
3. Cite the evidence — every claim names its source (solution doc path, commit hash, or session date + match snippet). No vague "we did this once"
4. Graceful degradation, stated plainly — if ccrider MCP is absent, say so once and use the fallback layers; never error out

Workflow

Layer 1: Compound Solution Docs (always)

Run Grep with keywords from the question over .claude/solutions/. Treat a hit here as the best answer — it was written for exactly this purpose. Present it and stop unless the user wants more.

Layer 2: Git Archaeology (always available)

git log --oneline --grep="{keyword}" -i -20      # commit messages
git log -S "{code-symbol}" --oneline -10          # when a symbol changed
git log --follow --oneline -10 -- {file}          # one file's history
git show {hash} --stat                            # inspect a candidate

Use -S (pickaxe) when the question names code; --grep when it names intent. Show matching commits with one-line context each.

Layer 3: Session Transcripts (ccrider MCP, gated)

Check for mcp__ccrider__* tools (load via ToolSearch if deferred).

If absent: report "ccrider MCP not connected — answered from solution docs + git history" and stop after Layers 1–2.

If present:

1. mcp__ccrider__search_sessions with the question's key phrases — returns ranked hits with session IDs and snippets
2. Present the top 3–5 hits (date, snippet) and pick the most relevant (or ask, if genuinely ambiguous)
3. Per selected session, spawn ONE subagent: "Fetch session {id} via mcp__ccrider__get_session_messages, extract only what answers '{question}', write ≤30 lines to .claude/recall/{id}.md" (Iron Law 2)
4. Read the summary files, synthesize the answer with citations

Step 4: Answer + Compound

Present the answer with its evidence trail. If the recalled knowledge was NOT already in .claude/solutions/, offer phx-compound so the next recall stops at Layer 1.

Integration

"have we done this before?" → phx-recall
   Layer 1 .claude/solutions/ ──hit──► answer + cite
   Layer 2 git log --grep/-S  ──hit──► answer + cite
   Layer 3 ccrider sessions (gated) ─► answer + cite → offer phx-compound

References

• references/archaeology-patterns.md — git pickaxe recipes, ccrider query patterns, subagent prompt template