---
name: backfill
description: >-
  Reconstruct an OKF bundle by event-sourcing a repository's history (git log
  and Claude session transcripts). Use when creating an `.okf/` bundle for an
  existing repository that predates this skill, or when resuming an interrupted
  backfill session. Triggers on: "reconstruct the OKF bundle", "backfill the
  knowledge bundle", "event-source the history".
user-invocable: true
argument-hint: "[repo-dir] [--no-sessions] [--sessions-dir DIR]"
allowed-tools: Bash Read Write Edit
---

# Reconstruct an OKF bundle from history

This skill replays a repository's decision-making history (git commits and
Claude session transcripts) to rebuild its OKF knowledge bundle as if the
[okf](/okf) skill's Stop hook had been active from the start.

The extraction layer is **deterministic** (same repo → byte-identical events);
the replay layer is an LLM loop, **replayable and auditable but not
byte-identical** (timestamps, summaries change per run). See the event schema
(§1) and skip rules (§3).

## 1. Event schema

Git commits and session turns become events (JSONL, one per line, sorted by
timestamp then source):

```json
{"id":"git:<sha>","source":"git","ts":"<ISO8601 Z>","sha":"...","author":"...","subject":"...","body":"...","files":[{"path":"...","add":N,"del":N}]}
{"id":"session:<file>:<lineno>","source":"session","ts":"<ISO8601 Z>","user":"...","outcome":"...","title":"...","branch":"...","skip":"..."}
```

- **Git events** come from `git log --first-parent --numstat`.
- **Session events** pair each user message with the **last** assistant text
  block of that turn (the wrap-up), extracted from
  `~/.claude/projects/<repo-slug>/*.jsonl` and worktree subdirs.
- **Timestamps** are normalized to UTC ISO 8601 strings ending in `Z`.
- **Skip field** (optional, added by extraction): marks low-signal events —
  see §3, never overridden by replay.

## 2. Protocol: Preflight → Extract → Bootstrap → Replay (Map+Reduce) → Finalize

### Preflight: check if bundle can be rebuilt

```bash
if [ -d <repo>/.okf ] && ! [ -f <repo>/.okf/.backfill-state.json ]; then
  echo "ERROR: .okf/ exists but is incomplete. Delete it to rebuild from scratch, or pass --resume to continue from the last checkpoint."
  exit 1
fi
```

If `.backfill-state.json` exists, resume from the cursor; otherwise, fresh bootstrap.

### Extract: generate event stream

```bash
uv run "${CLAUDE_SKILL_DIR}/scripts/okf_backfill_events.py" <repo-dir> \
  --out events.jsonl \
  [--no-sessions] [--sessions-dir ~/.claude/projects] \
  [--max-text 2000] [--skip-globs "vendor/**"]
```

Write `events.jsonl` to the scratchpad (never committed). Report:
- Total events extracted, per-source counts, and per-rule skip counts.

### Bootstrap: initialize bundle (fresh only)

Create `.okf/` with:

```bash
mkdir -p <repo>/.okf
echo 'okf_version: "0.2"' > <repo>/.okf/index.md
echo '# Update Log' > <repo>/.okf/log.md
```

Cursor (`.okf/.backfill-state.json`):

```json
{"last_id": null, "done": 0}
```

### Replay: two-phase map/reduce protocol

The replay is now structured in two phases to enforce semantic depth and anti-degeneration rules:

#### Phase 1: Map (parallel analysis, per-event)

Launch `okf:event-analyzer` agents for the live events (those without `skip` field), in waves of
4 to 10 (see the cost note in §5), via Claude Code's Workflow `agentType` parameter. Each analyzer
receives its event ids, the `events.jsonl` path, the repo path, the output directory and the
emitter path, and:
- Fetches its own event JSON with `jq` (the orchestrator dispatches ids, never content)
- Reads git evidence only through the capped diff emitter (§6); session events need no other call
- Writes `analyses/<event-id>.md` (event id with `:` sanitized to `-`) to scratchpad, with a
  `truncated` flag copied from the emitter's last line
- Replies with one line of counts per event; the analysis never travels back in the reply
- Never touches `.okf/`
- Is resumable: skip events already in `analyses/`

**Dispatch rule** (deterministic, from `events.jsonl`, no content read): a live event is
*small* when it is a session turn or a commit whose numstat totals at most 60 changed lines.
Small events are grouped chronologically, eight per analyzer call; large commits go one per
call. Measured on this repository (`benchmark/map-tier/RESULTS.md`): 57 calls instead of 147,
a third off the map phase at the same tier, no loss on any per-event metric and no
cross-event contamination.

```bash
jq -c 'select(.skip==null) | {id, small: (.source=="session" or (([.files[]?|.add+.del]|add)//0) <= 60)}' events.jsonl
```

**Host-agnostic fallback** (if no Workflow support): spawn generic subagents with the same
system prompt as `agents/event-analyzer.md`, one per event, collecting analyses to scratchpad.

#### Phase 2: Reduce (sequential folding, one agent)

Run a single `okf:bundle-weaver` agent that:
- Reads all analyses in chronological order
- Folds them into `.okf/`, updating or creating concepts
- Enforces anti-degeneration rules (§4)
- Updates `log.md` with dated bullets (the "why" from each analysis)
- Manages cursor (`.okf/.backfill-state.json`) for resume capability
- Is the only actor that writes `.okf/`
- Replies with one line of counts (folded, created, updated, bullets, conflicts, superseded,
  truncated inputs); the bundle never travels back in the reply

**Resume behavior:** both phases support resumption. Phase 1 skips already-analyzed event ids;
Phase 2 restarts from `last_id` in the cursor.

### Domain priming (advisory)

Before starting the map phase, read the repository's README and directory structure to sketch
a candidate taxonomy of concepts (skills, integrations, decisions, etc.). This priming is
*advisory only* — it helps the analyzer emit better candidate names. The *guarantee* that
no events are lost comes from the deterministic coverage check in Finalize (§5), not from
priming; analyses without candidate names still flow to the weaver.

### Context hygiene (orchestrator)

The orchestrator handles ids and counts, never content. Events, analyses and diffs are read by
the agents; the orchestrator reads:

```bash
wc -l events.jsonl                                   # total events
jq -r 'select(.skip==null) | .id' events.jsonl       # live ids to dispatch
ls analyses | wc -l                                  # analyses written
```

Never `cat events.jsonl` or open an analysis from the orchestrator: whatever enters its context
is billed at the frontier rate on every following turn, and the routing exists to prevent that.

### Finalize: validate and clean up

1. **Write `index.md` per directory by hand** (do NOT run `okf_init.py` — it
   would scaffold placeholder files): one `# Section` per directory, one
   bullet per concept, `* [Title](file.md) - description` taken from each
   concept's frontmatter (SPEC §8). The root `index.md` keeps its
   `okf_version: "0.2"` frontmatter and links every subdirectory.

2. **Add final log entry** (today's date, appended to existing dated section if present):
   ```
   ## 2026-09-01

   - **Backfill**: reconstructed from N events by okf-backfill/0.9.5
   ```

3. **Delete cursor:**
   ```bash
   rm -f .okf/.backfill-state.json
   ```

4. **Run self-checks for anti-degeneration rules:**
   ```bash
   # No concept filenames derived from change type
   ! find .okf -name "*.md" | grep -E "merge-pull-request|(^|/)(feat|fix|chore|docs)[:-]"
   
   # No non-kebab-case characters in filenames
   ! find .okf -name "*.md" | grep -E "[^a-z0-9/.-]"
   
   # No identical consecutive log bullets
   awk 'p==$0 && /^- / {exit 1} {p=$0}' .okf/log.md

   # Every concept declares its lifecycle (absent status reads as `stable`, SPEC §5.4)
   [ -z "$(grep -rL '^status:' --include='*.md' .okf | grep -v '/index.md$\|/log.md$')" ]
   ```
   These are lexical guards; they do not catch a bundle that asserts a superseded state. That
   check is semantic and belongs to the weaver, at fold time, when it has both the analysis and
   the earlier concepts on disk (§4 rule 5).

5. **Run coverage check to guarantee every event is mapped:**
   ```bash
   uv run "${CLAUDE_SKILL_DIR}/scripts/okf_backfill_events.py" \
     --check-coverage events.jsonl .okf
   ```
   Exit code 0 means all live events (non-skipped) appear in the bundle's `sources` or log.
   Exit code 1 with a list of unmapped ids means the weaver skipped some events; fix and re-run.

6. **Validate bundle schema:**
   ```bash
   uv run "${CLAUDE_SKILL_DIR}/../validate/scripts/okf_validate.py" .okf --strict
   ```
   Fix every error before finishing.

7. **Report** the resulting bundle:
   - Concept count per directory
   - Log entry samples (first and last)
   - Coverage check result (all events mapped)
   - Validation result (pass/fail, warnings)
   - Superseded resolutions (the weaver's `superseded` count) and deprecated concepts:
     `grep -rl '^status: deprecated' --include='*.md' .okf | wc -l`
   - Agents spawned per phase (analyzers, weaver invocations) and, when the host reports it,
     tokens per phase
   - Truncated analyses: `grep -l '^truncated: true' analyses/*.md | wc -l`, next to the
     deterministic estimate of git events whose full diff exceeds the default cap:
     `jq -r 'select(.skip==null and .source=="git") | [.files[]|.add+.del] | add' events.jsonl | awk '$1>300' | wc -l`

## 3. Skip rules

Events matching a rule below are marked `skip: <rule-id>` and skipped during
replay (cursor advances, no log entry):

| Rule | Condition | Rationale |
|------|-----------|-----------|
| `paths-only-generated` | Git commit touches ONLY lockfiles or generated code (vendor/, node_modules/, dist/, *.min.*, *.lock, etc.) | Noise: build byproducts, no knowledge content |
| `merge-no-files` | Git merge commit with no file changes (first-parent only) | Housekeeping |
| `session-command-noise` | Session user message is a slash command or <20 chars and has no useful outcome | Ephemeral UI/chatter |

Extend the first rule with `--skip-globs "extra/**"` for repo-specific patterns.

## 4. Anti-degeneration rules

The analyzer and weaver enforce these rules to prevent the bundle from devolving into
a mechanical listing of commits or a taxonomy-by-accident:

1. **Concept names describe domain entities, not changes.** Forbidden:
   - Filenames derived from git subject: `merge-pull-request-#2-....md`, `feat:-add-docs-skill.md`, `fix:-handle-edge-case.md`
   - Bare action words: `update.md`, `fix.md`, `add-feature.md`
   - Non-kebab-case: spaces, underscores, capitals, special characters (allowed: `[a-z0-9-]` only)

   Example: a commit with subject "feat: add presales pipeline" touches a domain concept.
   The *concept* is named `presales-pipeline.md` (the entity), not `feat:-add-presales-pipeline.md`
   (the change). The change history lives in frontmatter `sources` and log bullets.

2. **Prefer update over create.** Every event is analyzed for which concepts it touches; if
   a concept already exists and the analysis fits, update its `sources` and body. Only create
   a new concept if the analysis reveals a distinct domain entity not yet captured.

3. **Log bullets explain intent, not restate subjects.** A bullet should answer "why did this
   change happen?" from the commit body or session outcome, never just re-read the subject:
   - Bad: `- Added presales-pipeline.md feature`
   - Good: `- **Presales pipeline**: formalized the sales workflow to clarify handoff points`

4. **No identical consecutive bullets.** Group same-date updates by concept to avoid:
   ```
   - Feature X update
   - Feature X update
   - Feature X update
   ```
   Instead: one bullet per concept, or combine into "Feature X: multiple updates".

5. **A reversal is not growth.** A replay walks the history forward, so a later event routinely
   overturns an earlier one (a phase dropped, a limit changed, a target downgraded). "Prefer
   update over create" is a merge rule and says nothing about this: applied alone it leaves the
   bundle asserting both states in the present tense, in one concept or in two. The weaver greps
   the whole bundle before writing and, on contradiction, replaces rather than appends: the body
   states what holds today, the previous position drops to a dated line under `## History`, and
   an outdated concept that a newer one supersedes gets `status: deprecated` plus a link to its
   successor. A deprecated concept keeps its `sources`, so coverage stays green. None of the
   guards in Finalize can catch this — they are lexical, and a superseded claim is well-formed.

6. **Reconstructed concepts are `draft`, never `stable`.** SPEC §5.4 reads an absent `status` as
   `stable` ("ready for consumption"); a bundle nobody has reread is `draft` ("not yet reviewed;
   possibly incomplete"). The weaver writes `status:` on every concept.

## 5. Implementation notes

- **Determinism**: extraction is byte-identical; replay is not (time, LLM variance).
  Both are auditable: events.jsonl is deterministic, map analyses are stored and resumable,
  reduce loop is human-readable and cursor-backed.
- **Privacy**: events.jsonl goes to scratchpad, never committed. Session turn text is
  truncated (head+tail) before extraction.
- **Cost note**: deep replay reads one capped diff per git commit (§6) to extract
  rationale. For histories >500 events, consider splitting into sub-ranges and
  replaying sequentially, or use `--skip-globs` to exclude low-signal paths (e.g.,
  vendored dependencies, generated code). Map phase is parallel in waves of 4 to 10: the
  gate benchmark lost 260 of 299 runs to a high-concurrency mass failure and finished at
  concurrency 4 (`benchmark/gate/RESULTS.md`). Reduce is sequential but much cheaper
  (concepts already analyzed).
- **Future sources** (not implemented): GitHub PR/issue text, release notes, CI/deploy logs
  — all optional post-MVP. **Lore protocol** (arXiv 2603.15566): on repos that adopt git
  trailers (structured decision metadata), the extracted event's `body` already contains
  trailers in a machine-readable format. The analyzer and weaver should use trailers as
  the primary source of "why" (overriding generic inference from diff content).
- **Trust metadata**: `generated.by` is the backfill agent (`okf-backfill/0.9.5`), not
  claimed as human-reviewed (`human:...`); concepts are correctly `unverified` (SPEC §5.3) and
  `status: draft` (§5.4) — the two axes are independent: trust is who says it, lifecycle is
  whether it has been reread. Writing `status` is not optional here: absent, §5.4 reads it as
  `stable`, so a bundle nobody has reread would declare itself ready for consumption.
  Map-phase analyses are working artifacts (stored for auditability during reduce); the
  weaver's output is the canonical bundle.

## 6. Capped diff emitter

Analyzers never read a raw `git show`: the harness cuts long tool output blindly (mid-hunk,
character-based, host-dependent) and a cheap worker may not notice the cut. The extractor reads
the whole diff instead and emits a deterministic sample:

```bash
uv run "${CLAUDE_SKILL_DIR}/scripts/okf_backfill_events.py" <repo-dir> --show <sha> \
  [--only <path>] [--max-diff-lines 300] [--per-file-lines 120] [--max-line-chars 400] \
  [--skip-globs "vendor/**"]
```

- Diff against the first parent, so merge commits agree with the extracted numstat.
- The stat is always complete: entities survive any cap.
- Patches are capped per file (breadth over depth) and cut at hunk or file boundaries, with a
  bracketed marker at every cut; lines longer than `--max-line-chars` are shortened with a
  marker (a generated one-line file is "1 line" but can be hundreds of KB).
- Patches of generated files (lockfiles, `vendor/**`, `--skip-globs`) are omitted even inside
  mixed commits; their stat line stays.
- The last line is fixed-form: `[diff: shown=X total=Y files_shown=A files_total=B truncated=true|false]`.
  The analyzer copies `truncated` into its frontmatter; finalize reports the count.
- `--only <path>` is the one permitted follow-up when a truncated diff hides the rationale:
  same cap logic, one file.

Defaults keep one call under the harness limits with margin; tune per repo with the flags.

The analyzer's tier is configuration, not infrastructure: `agents/event-analyzer.md` carries
`model` and `effort` in its frontmatter. Fork the file to retier the map phase; the skill
resolves the agent by name and nothing else changes. The default is `haiku` since the
map-tier benchmark (`benchmark/map-tier/RESULTS.md`): parity with `sonnet` on commits at
under half the map cost, on the condition that the two explicit instructions in the agent
file stay (which summary line the flag copies; claims report intent as intent).