# Agent Note: Model-facing session query tools

Status: implemented

English | [中文](2026-07-24-model-facing-session-query-tools.zh.md)

## Problem

The unified `ctx.sessionQuery` service exposes exact reads, filters, relationship traces, and full-text search over live-preferred session logs, but models cannot use that service directly. Giving a model the provider request types would also expose unstable pagination cursors, trusted corpus scope, storage-shaped time values, and result records that are more convenient for programmatic consumers than for reasoning. Large traces and event payloads introduce a separate output-size concern, but solving that concern inside this consumer would duplicate the harness-wide spill mechanism and make session-query tools disagree with other tools.

## Decision

`@deepseek-ai/dsh-tool-session-query` is the model-facing consumer of `ctx.sessionQuery`. It registers five narrow read-only tools: `session_search`, `session_event_search`, `session_trace`, `session_event_trace`, and `session_event_read`. The package imports the interface rather than the SQLite implementation, owns model argument validation and readable text rendering, and contributes one concise prompt section that teaches the prior-history search and search-to-trace/read workflow.

The package entrypoint is only the public composition root for configuration, prompt registration, and tool registration. Its internal modules follow the execution boundary: `input.ts` owns model schemas, normalization, and filter construction; `service-boundary.ts` contains provider calls and model-safe error translation; `workspace-access.ts` owns caller identity, workspace authorization, title access, and lineage projection; `operations.ts` orchestrates the five service workflows; and `presentation.ts` renders tool results and call cards. This keeps policy in its owning layer without changing the package contract.

`session_search` groups full-text matches by session and exposes typed session and event metadata filters. `session_event_search` searches one session, defaulting to the caller's current session. `session_trace` returns the complete authorized ancestor chain and recursive descendant trees. `session_event_trace` returns every known positional replacement and direct provenance relationship for one event. `session_event_read` returns the exact target event as unabridged JSON and optionally summarizes a bounded raw-event window; omitted `before` and `after` values mean target-only.

Model-facing filters use flat snake-case fields. Timestamps are timezone-qualified ISO 8601 strings at the tool boundary, convert to inclusive epoch-millisecond ranges for the service, and render as UTC ISO 8601. List values are ORed inside one filter while separate filters are ANDed. Requested parent ids are deduplicated and authority-filtered before FTS, so only parents in the caller workspace enter the provider clause; missing and cross-workspace guesses behave identically, while the root-session marker remains independently ORed into that clause. Event type strings remain open because `SessionEventMap` is merge-extensible; availability and event surface use closed values.

## Workspace authority

Every executor derives its caller from immutable `ToolExecution.exec.agent` identity and never accepts a model-supplied workspace. A target is authorized only when its observed `cwd` exactly equals the caller session's `cwd`. Cross-session search always adds that workspace filter. Direct operations preflight the target and then validate the header returned from the same service observation as every event-search page, event trace, event read, lineage target, or folded title before rendering its payload. This prevents a live or persisted target replacement between the check and use from crossing the workspace boundary. Lineage rendering stops at an unauthorized ancestor or descendant subtree without revealing the hidden session id. A caller whose session has no `cwd` can inspect only its own session; missing agent identity fails closed.

Every trusted `ctx.sessionQuery` call crosses one model-boundary sanitizer. It checks the execution signal first, preserving caller cancellation exactly. For other failures it records the available corpus or provider diagnostic chain in the internal log on a best-effort basis, substituting a fixed placeholder when the value cannot be safely inspected. Diagnostic formatting and error classification are independently guarded, so an unprintable nested cause cannot escape or prevent a safely classified outer error, while unsafe classification or logging returns the fixed generic `SESSION_QUERY_TOOL_FAILED` code and message. Per-title failures use the same sanitizer before becoming unavailable markers. Tool-owned input-validation and authorization errors remain precise because they are created outside this service boundary.

The search tools expose prior work rather than the operation that is performing the search. `session_search` omits the caller's session. When `session_event_search` targets the caller's session, it intersects the requested sequence range with the event immediately before the current `step/start`, excluding the current assistant message and tool call as well as the query arguments indexed from that call.

## Cursor-free results and spill

Neither search tool exposes a cursor, offset, page size, or model-controlled result limit. One execution follows provider cursors while the observed generation remains valid and collects up to the configured `maxSearchResults`, which defaults to 100. A capped result tells the model to narrow its query or filters; a generation change reports that the whole search must be retried. Search execution carries a configurable `searchTimeoutMs`, defaulting to 30 seconds, through the tool deadline and the service abort signal. Because internal pages share generation-bound cursors, both search tools are exclusive in the agent-loop scheduler; the exact trace and read tools opt into parallel sibling execution because their observations tolerate intervening commits.

Trace and read tools likewise expose no lineage or character pagination. Canonical results are plain text and remain complete within the service's existing event-window and search-count resource bounds. Each exact executor passes its unchanged tool-execution signal through target authorization and the service trace or read. Within service resolution, known-live event traces, event reads, and title reads remain persistence-free while honoring pre-abort. Session lineage tracing passes the signal to whole-corpus persistence listing; persisted event tracing and reading pass it to target listing and inspection. Each started backend call is awaited for cleanup before the exact abort reason is preserved, even when that backend ignored cancellation. The generic `tools/post-execute` spill policy owns inline byte retention: when a configured deployment receives oversized text, it replaces that text with a bounded preview plus an opaque locator and retrieval hint while preserving the complete result in its spill store. The session-query consumer neither imports `ctx.spillStore` nor implements a second truncation format.

Session-level results include the latest folded title when available. Each tool execution batches its unique title ids through one live-preferred corpus observation with at most the service's configured `persistedInspectConcurrency` workers, which defaults to four, and passes the exact tool-execution signal through persisted listing and inspection. Live sources fold directly; each persisted worker folds its completed source to a detached header/title observation and releases the full log before dequeuing another id, so the batch retains only small projected values. For the search tools, the execution signal carries the configured search deadline. Cancellation starts no queued title inspections and rejects the complete tool execution after already-started inspections settle; a missing, malformed, or operationally failed title remains isolated to that id, preserves the base result, renders an unavailable marker, and logs the underlying error, while an authorization mismatch fails closed. Search results include the strongest matching event and provider excerpt, traces include complete authorized relationships, and event reads keep neighbor presentation readable while reserving exact JSON for the requested target.

## Host composition

The consumer is an opt-in plugin. The shipped ACP and TUI apps mount `ctx.sessionQuery` for non-model consumers, while the shared Web/headless composition mounts neither the query service nor the consumer. No shipped composition mounts `@deepseek-ai/dsh-tool-session-query`, so default model requests gain no query prompt or schemas. A composition that opts in also chooses whether to mount the generic timeout and spill policies; the dedicated ACP snapshot fixture mounts both and uses private local spill storage. Generic tool presentation requires no session-query-specific client plugin.

## Alternatives considered

- **Expose provider cursors to the model** — rejected because recording a tool result or starting the next model step changes the relevant session or global generation, so a cursor is usually stale before the model can reuse it.
- **Add tool-local truncation, offsets, or spill files** — rejected because the post-execute spill policy already owns complete-result retention and retrieval across tools.
- **Allow every persisted session or model-supplied workspace filters** — rejected because `ctx.sessionQuery` is a trusted service and the model-facing consumer must enforce the caller's authority boundary.
- **Combine search, tracing, and exact reads into one operation selector** — rejected because narrow names give the model clearer schemas, defaults, presentation intents, and follow-up choices.
- **Return only one lineage hop** — rejected because spill removes the inline-size motivation while one-hop output would omit relationships with no continuation path.

## Verification

Package tests pin argument validation, filter translation, timestamp normalization, exact-workspace authorization, parent-filter preauthorization and oracle resistance, changed-observation rejection, service-diagnostic redaction for ordinary and adversarial unknown values, best-effort cyclic-cause logging, logger-failure containment, missing-identity behavior, hidden-boundary pruning, current-step exclusion, internal provider paging, exclusive search and parallel exact-read classification, count caps, exact-signal forwarding, abort-reason preservation, persistence cleanup quiescence, one-scan bounded batch title enrichment, projection-before-dequeue ordering, queued-work suppression, started-worker quiescence, per-header validation, title fallbacks, representative search/trace/read rendering, generic presentation, and disposable registration. Integration coverage uses the real SQLite FTS provider over live and persisted sessions. Shipped configuration, app composition tests, and assembled ACP request-header snapshots prove that the model-facing consumer remains absent while `ctx.sessionQuery` stays available where mounted. A package-owned Loader smoke and dedicated keyless ACP snapshot explicitly mount the consumer with timeout and spill support, pinning its prompt guidance, schemas, and path-independent exact event-read retention behavior.

## Consequences

Models gain provider-independent access to prior session work without receiving storage authority or continuation state. Search has a finite per-call work bound and may require a narrower query to reach matches beyond the first 100; search calls cannot overlap siblings, while exact observations retain parallel scheduling. Complete traces and event payloads may become spill references instead of inline text. Exact string `cwd` equality favors a conservative security boundary over resolving symlink-equivalent paths. Custom compositions may mount the tool without spill, but then they explicitly accept complete inline trace and read results.
