Pi Session Search

Why inject memory into every Pi session when you can search history on demand?

Memory-first extensions solve a real but different problem. They preserve selected facts, preferences, summaries, or instructions for future work. That is useful when the retained material should influence every relevant session. It is a poor default when you only want to answer questions such as "What did we decide about the migration?" or "Where did we fix this before?"

Your agent should not carry unrelated history into every new task.

Persistent memory has to decide what deserves to survive, keep that material current, and decide when to place it back into the prompt. A bad decision at any of those steps can spend context on unrelated facts, carry stale conclusions into new work, or make old conversation text look like a current instruction. Larger memory stores also consume prompt space before the agent has established that the current task needs them.

Session Search takes the narrower approach. It creates no durable memories, context banks, generated skills, or automatic context injection. It builds a private, rebuildable SQLite FTS5 index from visible prose in local Pi JSONL transcripts. The transcripts remain read-only and authoritative.

An index is not context. Historical text reaches the model only when the agent calls session_search, and every result is bounded and labeled as untrusted historical evidence.

Two ways to reuse history

flowchart TB
  subgraph MEMORY["Memory-first extension"]
    direction TB
    M1["Past conversations"] --> M2["Select and rewrite facts"]
    M2 --> M3[("Durable memory")]
    M3 --> M4["Inject retained context<br/>into later prompts"]
  end

  subgraph SEARCH["Session Search"]
    direction TB
    S1["Read-only Pi transcripts"] --> S2[("Private FTS5 index")]
    S3["Current question"] --> S4["session_search<br/>on demand"]
    S2 --> S4
    S4 --> S5["Bounded, untrusted<br/>excerpts"]
  end

Memory-first tools can make retained material part of future prompts before the current task proves it is relevant. Session Search keeps transcripts and the index outside the prompt until the agent asks for specific evidence.

	Memory-first extensions	Session Search
Main job	Carry selected knowledge into future work	Retrieve evidence from past conversations when requested
Prompt behavior	May add retained material proactively	Adds nothing until session_search runs
Stored representation	Durable facts, summaries, preferences, or instructions	Rebuildable lexical index of transcript prose
Source of truth	A curated memory layer that must stay current	Original read-only Pi transcripts
Recall scope	What the memory process chose to retain	Indexed user, assistant, and system prose
Result control	Depends on the memory injection policy	Project, role, date, result-count, snippet, and output limits

This makes Session Search the better default for conversation recall. You get the useful part, finding what happened before, without turning every past conversation into standing context for the next one.

From transcript to bounded evidence

flowchart TB
  J["Pi JSONL transcripts"] --> P["Parse visible prose"]
  P -. drops .-> X["Thinking, images,<br/>tool I/O, extension entries"]
  P --> D[("Private SQLite FTS5")]
  Q["Question plus optional<br/>query variants"] --> R{"Search route"}
  D --> R
  R -->|"Exact: newest first"| O["Dedupe, filter, and bound"]
  R -->|"Broad: BM25 relevance"| O
  O --> U["Untrusted historical evidence"]

The extension writes only its rebuildable index. It does not rewrite source transcripts, create memories, call a translation service, or add search results to the prompt without a session_search call.

The boundary is enforced in code. Thinking blocks, images, tool arguments, tool results, and extension entries stay out of the index. A call returns at most 20 results, limits each excerpt to between 100 and 4,000 characters, and caps total output at 50 KiB. Exact matches keep newest-first ordering. Broader lexical fallback uses FTS5 BM25 relevance. The agent may also supply up to three source-language translations or keyword paraphrases, but Session Search makes no translation, network, or additional model call.

On a frozen private corpus of 528 valid sessions and 9,023 visible messages, Session Search reached 92.5% Rank@1 and 100% Recall@10 across 40 deterministic known-item queries. Persistent-engine p95 latency was 1.16 ms. See docs/benchmark.md for the methodology and limitations.

Runtime contract

• session_search searches bounded historical snippets.
• queryVariants accepts up to three agent-supplied source-language translations or keyword paraphrases. Variants are searched first and results are interleaved and deduplicated by session.
• /session-index reconciles and incrementally updates the local index.
• Startup performs a bounded incremental backfill.
• Live indexing follows finalized messages.
• Shutdown flushes pending indexing and closes SQLite.
• Transcript results are marked as untrusted historical evidence.

Indexed by default:

• user prose
• visible assistant prose
• system prose
• project, cwd, timestamp, role, and tool names as metadata

Excluded by default:

• thinking blocks
• images and base64
• tool arguments and tool results
• extension custom entries

Install

Install Pi Session Search from npm:

pi install npm:@felores/pi-session-search

Restart Pi or run /reload, then build the initial index:

/session-index

Ask Pi about earlier conversations normally. The agent can call session_search with optional source-language queryVariants when the current question and the historical conversation may use different languages.

The extension reads Pi JSONL transcripts without modifying them. Generated state stays in ~/.pi/agent/session-search/ with private filesystem modes.

Local development

npm install
npm run hooks:install # optional contributor hook
npm run quality
pi -e ./src/index.ts

Generated state defaults to ~/.pi/agent/session-search/index.sqlite. Override the storage directory with PI_SESSION_SEARCH_DIR and the transcript root with PI_CODING_AGENT_SESSION_DIR.

Do not enable Session Search globally alongside another extension that already registers session_search; Pi will suffix duplicate tool and command names. During migration, validate this checkout with pi -e ./src/index.ts and switch the global package only after the replacement index passes its gates.

Status

The first release supports Pi JSONL sessions. The normalized source boundary is reserved for a later read-only OpenCode SQLite adapter.

License and origin

MIT. Parts of the parser and search behavior are derived from pi-hermes-memory. See ATTRIBUTION.md.