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obelisk/references/pitfalls.md
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tommy0103 0128881d04 docs: add learned-facet detail pass and session-window pitfall
Teach the agent to derive second-pass filters from first-pass evidence
  instead of pulling large message windows. Add the pattern and a pitfall
  warning against defaulting to LIMIT 25 transcript browsing.
2026-06-07 18:35:08 +08:00

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# Obelisk Pitfalls
Use this when a query may over-fetch, when a scoped query returns few or zero
rows, or when helper fields are unclear.
## Scope Is A Contract
If the user gives a project, session, file, or time range, keep every query
inside that scope. Do not broaden because a scoped result is small.
There are three different project-like scopes:
- `sessions.project`: stored Claude Code project slug.
- `sessions.project_path`: reconstructed absolute project path.
- `messages.cwd`: working directory for a specific message.
`project` filters in helpers are SQL `LIKE` patterns over `sessions.project`.
`%quiet-zero%` can match benchmark or generated workspaces that merely contain
that string. Prefer exact `sql()` filters when the user asks for exact project
membership:
```js
sql(`
SELECT id, title, project, project_path, ended_at
FROM sessions
WHERE project_path = ?
ORDER BY ended_at DESC
LIMIT 20
`, '/Users/tomiya/Code/quiet-zero')
```
Use fuzzy project search only when the task is discovery or the user explicitly
asked to search broadly. If you broaden, make the broadening visible in the
returned evidence.
Self-noise examples to filter when the user asks for real historical sessions:
- `SkillOpt-outputs`
- `obelisk_train`
- `obelisk-eval`
## FTS5 Hyphens And Syntax
`search(text)` passes text to FTS5 `MATCH`. Hyphenated terms can be parsed as
operators or separate tokens, and special characters can raise FTS syntax
errors.
For `workflow-script`, use a quoted tokenized phrase:
```js
search('"workflow script"', { limit: 10 })
```
Use exact phrases for phrase semantics, separate terms for token semantics, and
SQL `LIKE` for literal punctuation. Do not silently fallback from a scoped FTS
query to all sessions.
For exact hyphen matching, use SQL `LIKE` on `messages.text` under a scope:
```js
sql(`
SELECT m.uuid, s.id AS session_id, s.title, substr(m.text,1,240) AS snippet
FROM messages m
JOIN sessions s ON s.id = m.session_id
WHERE s.project LIKE ?
AND m.text LIKE ?
ORDER BY m.timestamp DESC
LIMIT 10
`, '%quiet-zero%', '%workflow-script%')
```
`rank` is already applied by `ORDER BY rank`; lower rank sorts earlier in this
runtime. Prefer returned order over comparing "closer to zero" manually.
## Context Is Not Always Causal
`search().context` returns temporal neighbors: nearby messages by timestamp in
the same session. It is useful for quick orientation, but it is not the parent
chain and may cross side branches, subagents, or workflow boundaries.
Use:
- `context(uuid)` for message, parent chain, session, subagent, and workflow.
- `trace(uuid)` for just the parent chain.
- SQL timestamp neighbors for horizontal expansion inside one session.
## Ordering Defaults Matter
Some helpers return newest first; others do not.
- `sessions()` returns newest sessions first.
- `summaries()` returns newest summaries first.
- `workflows()` returns newest workflows first.
- `failures()` returns newest failures first, but should still be treated as an evidence helper rather than a precise count helper.
- `fileHistory()` orders by message timestamp ascending. If the user asks for recent changes, use SQL explicitly:
```js
sql(`
SELECT tc.id, tc.name, tc.file_path, m.timestamp, s.id AS session_id, s.title
FROM tool_calls tc
JOIN messages m ON m.uuid = tc.message_uuid
JOIN sessions s ON s.id = tc.session_id
WHERE tc.file_path = ?
AND tc.name IN ('Edit', 'Write', 'NotebookEdit')
ORDER BY m.timestamp DESC
LIMIT 20
`, '/absolute/path/to/file')
```
## Conversation Turns Are Expensive
SQLite queries are cheap; repeated conversation turns are not. Every turn can
write intermediate query output into conversation context and make later turns
read it again.
For conclusion, broad history, failure investigation, or file evolution tasks,
prefer one bounded query script that does the mechanical retrieval work inside
the script:
1. locate candidates with `search()`, `summaries()`, or SQL;
2. expand only selected hits with `context()`, `trace()`, or neighbor SQL;
3. dedupe and group by `session_id`, facet, file, or tool;
4. return compact evidence rows plus counts/limits.
Do not show every intermediate result to the conversation. Return the final
compact evidence view, then use the model for the conclusion.
## Session Windows Are Not Evidence Plans
After finding a relevant session, avoid defaulting to `LIMIT 25` or `LIMIT 40`
message windows. That is transcript browsing in miniature: it often brings back
thinking, transitions, and repeated context instead of the evidence needed for
the question.
Preferred detail pass:
1. extract candidate terms, files, tools, or decisions from the first pass;
2. query by learned facets inside the candidate sessions;
3. return 2-4 rows per facet, 8-12 rows total, with 160-220 char snippets.
If the vocabulary is still unclear, use a small session window as fallback:
5-8 rows per session, filtered by timestamp, role, or discovered terms when
possible, and explain the fallback in `query_plan`.
## Compact Vs Raw
Default to compact evidence. Raw/full access is a conscious escalation.
- `workflowTree()` may include `script`, `result_json`, parsed `result`, and all agents. Project only the fields needed for the answer.
- `thread(sessionId)` dumps a whole session; use it only as a last resort.
- `raw(uuid)` can recover long original JSONL lines; use small windows and cite `totalLength`/`hasMore`.
- Tool results and tool inputs can be large. Return short snippets.
## Field Names To Avoid Guessing
Common wrong guesses:
- Summaries: use `source` and `content`; do not use `summary_type` or `text`.
- Tool call name: use `tool_calls.name`. `tool_name` is only a safe alias in `SELECT tc.name AS tool_name`; `tc.tool_name` is not a table column.
- Tool result timestamps: `tool_results` has no timestamp. Join `messages`.
- Tool call timestamps: `tool_calls` has no timestamp. Join `messages`.
- Workflow agent message counts: `workflowTree()` returns `messageCount` for agents.
When uncertain:
```js
const rows = summaries({ limit: 1 });
return rows.length ? Object.keys(rows[0]) : [];
```
## Counting Must Be Structural
If the user asks "how many", "counts", "top N", or "group by", compute it in SQL
or in the query script and return the computed data. Do not infer counts from
visible snippets in prose.
Good:
```js
sql(`
SELECT tc.name, COUNT(*) AS n
FROM tool_results tr
JOIN tool_calls tc ON tc.id = tr.tool_use_id
WHERE tr.is_error = 1
GROUP BY tc.name
ORDER BY n DESC
LIMIT 10
`)
```
Bad:
```js
const rows = failures({ limit: 20 });
return rows; // then count by eye in the final answer
```
## Empty Results
An empty array is often the correct answer.
When the user asks for a scoped project/file/session or an exact sentinel:
1. Run the scoped query.
2. Return `[]` or compact counts.
3. Say no matching prior result was found.
4. Do not call `recent()`, all-project `summaries()`, or `thread()` as fallback unless the user asks.