refactor(session): centralize surface provenance validation

docs/config-catalog.md

@@ -359,7 +359,7 @@ export interface Config {
 }
 ```
 
-Source: [`packages/support/invariants/src/index.ts:45`](../packages/support/invariants/src/index.ts)
+Source: [`packages/support/invariants/src/index.ts:52`](../packages/support/invariants/src/index.ts)
 
 ## `@deepseek-ai/dsh-llm-deepseek`
 

docs/rfc/implemented/feature/2026-07-13-session-query-tracing.md

@@ -16,7 +16,7 @@ Session relationships are encoded across immutable headers, positional surface o
 
 ## Validation boundary
 
-Event tracing checks target existence before surface analysis. Before returning a trace it validates the whole loaded log: only surface event types carry provenance, present arrays are nonempty and duplicate-free, every source is a known earlier seq, and every positional replacement names all surface nodes it removed. Provenance failures use `SESSION_QUERY_INVALID_PROVENANCE`; positional fold failures keep `SESSION_QUERY_INVALID_SURFACE`. `listEvents()` remains a surface-classification operation and does not acquire trace-specific provenance rejection.
+Event tracing checks target existence before surface analysis. Before returning a trace it validates the whole loaded log through `dsh-session`'s shared provenance checker: only surface event types carry provenance, present arrays are nonempty and duplicate-free, every source is a known earlier seq, and every positional replacement names all surface nodes it removed. Provenance failures use `SESSION_QUERY_INVALID_PROVENANCE`; positional fold failures keep `SESSION_QUERY_INVALID_SURFACE`. `listEvents()` remains a surface-classification operation and does not acquire trace-specific provenance rejection.
 
 All returned records and arrays are detached. A known live event trace never consults persistence; persisted event traces preserve the exact-read list/load consistency check. Session lineage is necessarily a cross-corpus operation and therefore preserves cross-corpus persistence failure semantics.
 

packages/core/session/README.md

@@ -48,6 +48,7 @@ Plain class (not a Cordis Service). Create via `ctx.sessions.create()`.
 - `SurfaceIntent` — `{ surfaceOp: SurfaceOp; sourceEventSeqs?: number[] }`, the required third parameter to `session.append()` for surface-eligible types.
 - `SurfaceNode` — `{ seq: number; prev: number | null; next: number | null }`, one node in the surface linked list.
 - `foldSurface(events)` — replay the canonical surface transitions into detached current nodes and actual replacement ranges, rejecting surface-eligible events that lack their mandatory marker. `SurfaceManager` shares the same transitions while retaining its incremental cache.
+- `validateSurfaceProvenance(event, knownSeqs, shadowedSeqs?)` — pure provenance-contract check shared by incremental invariant listeners and exact readers. It returns the first violation instead of choosing a caller's error taxonomy.
 - `isSurfaceEvent(event)` / `isSurfaceEligibleType(type)` — the first narrows a `SessionEvent` to a fully-formed surface node (type is surface-eligible AND `surfaceOp` present); the second is the type-only check (is this one of the five `SurfaceEventType` values?), used to detect a surface-eligible event MISSING its marker — e.g. when validating a seed/load log.
 
 ### Request-header reconstruction (`request-header.ts`)

packages/core/session/src/index.ts

@@ -21,7 +21,7 @@ export { isJsonValue } from './json.ts'
 export type { JsonValue } from './json.ts'
 export { interruptedTurnClosers } from './repair.ts'
 export type { SurfaceFoldReplacement, SurfaceFoldResult, SurfaceNode } from './surface.ts'
-export { foldSurface, isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
+export { foldSurface, isSurfaceEvent, isSurfaceEligibleType, validateSurfaceProvenance } from './surface.ts'
 export { isToolPairingBalanced } from './tool-pairing.ts'
 export { applyHeaderDelta, canonicalHeader, diffHeader, foldRequestHeader, headerEquals } from './request-header.ts'
 

packages/core/session/src/surface.ts

@@ -81,6 +81,51 @@ export interface SurfaceFoldResult {
   replacements: SurfaceFoldReplacement[]
 }
 
+/**
+ * Validate one event's logged provenance against the preceding log and the
+ * surface nodes it actually shadows.
+ * @param event - event whose optional `sourceEventSeqs` is being checked.
+ * @param knownSeqs - seqs preceding `event` in the same log.
+ * @param shadowedSeqs - surface nodes directly removed by this event.
+ * @returns the first contract violation, or `undefined` when provenance is valid.
+ */
+export function validateSurfaceProvenance(
+  event: SessionEvent,
+  knownSeqs: ReadonlySet<number>,
+  shadowedSeqs: readonly number[] = [],
+): string | undefined {
+  const sources = (event as SessionEvent & { sourceEventSeqs?: unknown }).sourceEventSeqs
+  if (sources !== undefined && !isSurfaceEligibleType(event.type)) {
+    return `${event.type} cannot carry sourceEventSeqs (non-surface event)`
+  }
+  if (sources !== undefined && !Array.isArray(sources)) {
+    return `sourceEventSeqs on event at seq ${event.seq} must be an array when present`
+  }
+  if (Array.isArray(sources) && sources.length === 0) {
+    return 'sourceEventSeqs must not be empty when present'
+  }
+
+  const unique = new Set<unknown>()
+  for (const source of sources ?? []) {
+    if (unique.has(source)) return 'sourceEventSeqs must not contain duplicates'
+    unique.add(source)
+    if (typeof source !== 'number' || !Number.isInteger(source) || source < 0) {
+      return `sourceEventSeqs contains invalid seq ${String(source)}`
+    }
+    if (source >= event.seq) {
+      return `sourceEventSeqs must reference earlier events: ${source} >= current seq ${event.seq}`
+    }
+    if (!knownSeqs.has(source)) return `sourceEventSeqs references unknown seq ${source}`
+  }
+
+  const sourceSet = new Set(sources ?? [])
+  const missing = shadowedSeqs.filter(seq => !sourceSet.has(seq))
+  if (missing.length > 0) {
+    return `surface replace: sourceEventSeqs must include every shadowed surface node; missing ${missing.join(', ')}`
+  }
+  return undefined
+}
+
 /** Mutable state shared by the incremental manager and the full-log fold. */
 interface SurfaceFoldState {
   nodes: SurfaceNode[]

packages/core/session/tests/surface.spec.ts

@@ -1,6 +1,13 @@
 import { describe, expect, it } from 'vitest'
 import type { SessionEvent, SurfaceEvent, SurfaceEventType } from '@deepseek-ai/dsh-session'
-import { Session, SessionId, foldSurface, isSurfaceEligibleType, isSurfaceEvent } from '@deepseek-ai/dsh-session'
+import {
+  Session,
+  SessionId,
+  foldSurface,
+  isSurfaceEligibleType,
+  isSurfaceEvent,
+  validateSurfaceProvenance,
+} from '@deepseek-ai/dsh-session'
 import { CallId } from '@deepseek-ai/dsh-llm'
 
 /** Build a minimal session with turn boundaries and a single user message. */
@@ -13,6 +20,59 @@ function surfaceSession(): Session {
   return s
 }
 
+function provenanceEvent(seq: number, sourceEventSeqs: unknown): SessionEvent {
+  return {
+    type: 'user/message',
+    seq,
+    time: seq,
+    data: { content: [], source: { kind: 'user' } },
+    surfaceOp: 'append',
+    sourceEventSeqs,
+  } as unknown as SessionEvent
+}
+
+describe('validateSurfaceProvenance', () => {
+  it('accepts absent or valid provenance and complete replacement coverage', () => {
+    expect(validateSurfaceProvenance(provenanceEvent(0, undefined), new Set()))
+      .toBeUndefined()
+    expect(validateSurfaceProvenance(provenanceEvent(2, [0, 1]), new Set([0, 1]), [1]))
+      .toBeUndefined()
+  })
+
+  it('rejects provenance on a non-surface event', () => {
+    const event = {
+      type: 'turn/start',
+      seq: 1,
+      time: 1,
+      data: { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } },
+      sourceEventSeqs: [0],
+    } as unknown as SessionEvent
+    expect(validateSurfaceProvenance(event, new Set([0])))
+      .toMatch(/cannot carry sourceEventSeqs/)
+  })
+
+  it.each([
+    ['a non-array', 1, 'invalid', new Set([0]), [], /must be an array/],
+    ['an empty array', 1, [], new Set([0]), [], /must not be empty/],
+    ['duplicates', 1, [0, 0], new Set([0]), [], /must not contain duplicates/],
+    ['a non-number', 1, ['0'], new Set([0]), [], /invalid seq 0/],
+    ['a fractional number', 1, [0.5], new Set([0]), [], /invalid seq 0\.5/],
+    ['a negative number', 1, [-1], new Set([0]), [], /invalid seq -1/],
+    ['a self reference', 1, [1], new Set([0]), [], /must reference earlier events/],
+    ['an unknown earlier seq', 2, [1], new Set([0]), [], /references unknown seq 1/],
+    ['incomplete replacement coverage', 2, [0], new Set([0, 1]), [0, 1], /missing 1/],
+  ] as const)(
+    'returns the first violation for %s',
+    (_name, seq, sources, knownSeqs, shadowedSeqs, expected) => {
+      expect(validateSurfaceProvenance(
+        provenanceEvent(seq, sources),
+        knownSeqs,
+        shadowedSeqs,
+      )).toMatch(expected)
+    },
+  )
+})
+
 describe('SurfaceManager', () => {
   it('shares exact nodes and nested replacement ranges with foldSurface', () => {
     const s = new Session(SessionId('shared-fold'))

packages/session-query/session-query/README.md

@@ -14,7 +14,7 @@ This is trusted context-wide infrastructure. It performs no caller authorization
 
 Persistence is optional and may mount or unmount dynamically. Cross-corpus listing and lineage tracing fail with `SESSION_QUERY_PERSISTENCE_FAILED` while mounted persistence is unreadable. An event read or trace targeting a known live session does not consult persistence, so durable backend health cannot make current in-memory history unreadable. Persisted event operations list before loading and reject a metadata mismatch rather than combining inconsistent observations.
 
-`traceEvent()` validates the whole loaded log before returning relationships: provenance arrays are nonempty and duplicate-free, references name known earlier events, only surface event types carry sources, and each positional replacement names every surface node it removed. Provenance violations fail with `SESSION_QUERY_INVALID_PROVENANCE`; positional fold failures remain `SESSION_QUERY_INVALID_SURFACE`. `listEvents()` only needs surface classification and deliberately does not enforce the trace-specific provenance contract.
+`traceEvent()` validates the whole loaded log with `dsh-session`'s shared provenance checker before returning relationships: provenance arrays are nonempty and duplicate-free, references name known earlier events, only surface event types carry sources, and each positional replacement names every surface node it removed. Provenance violations fail with `SESSION_QUERY_INVALID_PROVENANCE`; positional fold failures remain `SESSION_QUERY_INVALID_SURFACE`. `listEvents()` only needs surface classification and deliberately does not enforce the trace-specific provenance contract.
 
 `SessionQueryError.code` is a closed union: `SESSION_QUERY_EVENT_NOT_FOUND`, `SESSION_QUERY_INVALID_CONFIG`, `SESSION_QUERY_INVALID_LINEAGE`, `SESSION_QUERY_INVALID_PROVENANCE`, `SESSION_QUERY_INVALID_SURFACE`, `SESSION_QUERY_INVALID_WINDOW`, `SESSION_QUERY_PERSISTENCE_FAILED`, `SESSION_QUERY_SESSION_NOT_FOUND`, and `SESSION_QUERY_SOURCE_CONFLICT`.
 

packages/session-query/session-query/src/tracing.ts

@@ -1,6 +1,6 @@
 /** One-shot session-lineage and event-relationship tracing helpers. */
 
-import { foldSurface, isSurfaceEligibleType } from '@deepseek-ai/dsh-session'
+import { foldSurface, validateSurfaceProvenance } from '@deepseek-ai/dsh-session'
 import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session'
 import { SessionQueryError } from './config.ts'
 import type {
@@ -51,7 +51,21 @@ export function traceEventLog(
   }
 
   const analysis = analyzeEventLog(sessionId, events)
-  validateProvenance(events, analysis.replacedEventSeqs)
+  const knownSeqs = new Set<number>()
+  for (const event of events) {
+    const violation = validateSurfaceProvenance(
+      event,
+      knownSeqs,
+      analysis.replacedEventSeqs.get(event.seq),
+    )
+    if (violation !== undefined) {
+      throw new SessionQueryError(
+        `invalid session provenance: ${violation}`,
+        'SESSION_QUERY_INVALID_PROVENANCE',
+      )
+    }
+    knownSeqs.add(event.seq)
+  }
 
   const replacementChain: number[] = []
   let replacement = analysis.replacedBy.get(seq)
@@ -189,73 +203,6 @@ function analyzeEventLog(
   }
 }
 
-function validateProvenance(
-  events: readonly SessionEvent[],
-  replacedEventSeqs: ReadonlyMap<number, readonly number[]>,
-): void {
-  for (const event of events) {
-    const sources = rawEventSources(event)
-    if (sources === undefined) continue
-    if (!isSurfaceEligibleType(event.type)) {
-      throw new SessionQueryError(
-        `invalid session provenance: non-surface event at seq ${event.seq} carries sourceEventSeqs`,
-        'SESSION_QUERY_INVALID_PROVENANCE',
-      )
-    }
-    if (!Array.isArray(sources) || sources.length === 0) {
-      throw new SessionQueryError(
-        `invalid session provenance: event at seq ${event.seq} has an empty or invalid sourceEventSeqs`,
-        'SESSION_QUERY_INVALID_PROVENANCE',
-      )
-    }
-    const unique = new Set<unknown>()
-    for (const source of sources as unknown[]) {
-      if (unique.has(source)) {
-        throw new SessionQueryError(
-          `invalid session provenance: event at seq ${event.seq} repeats source seq ${String(source)}`,
-          'SESSION_QUERY_INVALID_PROVENANCE',
-        )
-      }
-      unique.add(source)
-      if (
-        typeof source !== 'number'
-        || !Number.isInteger(source)
-        || source < 0
-        || source >= event.seq
-        || events[source]?.seq !== source
-      ) {
-        throw new SessionQueryError(
-          `invalid session provenance: event at seq ${event.seq} references unknown or non-earlier source seq ${String(source)}`,
-          'SESSION_QUERY_INVALID_PROVENANCE',
-        )
-      }
-    }
-  }
-
-  for (const [replacementSeq, removedSeqs] of replacedEventSeqs) {
-    // Canonical logs guarantee events[i].seq === i, and the fold reports only
-    // replacement events from this input log.
-    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-    const replacement = events[replacementSeq]!
-    const sources = rawEventSources(replacement)
-    if (!Array.isArray(sources)) {
-      throw new SessionQueryError(
-        `invalid session provenance: replacement at seq ${replacementSeq} omits its shadowed surface sources`,
-        'SESSION_QUERY_INVALID_PROVENANCE',
-      )
-    }
-    const sourceSet = new Set(sources as unknown[])
-    for (const removedSeq of removedSeqs) {
-      if (!sourceSet.has(removedSeq)) {
-        throw new SessionQueryError(
-          `invalid session provenance: replacement at seq ${replacementSeq} omits shadowed surface seq ${removedSeq}`,
-          'SESSION_QUERY_INVALID_PROVENANCE',
-        )
-      }
-    }
-  }
-}
-
 function rawEventSources(event: SessionEvent): unknown {
   return (event as SessionEvent & { sourceEventSeqs?: unknown }).sourceEventSeqs
 }

packages/support/invariants/README.md

@@ -31,6 +31,7 @@ await ctx.plugin(Invariants, { freeze: false })  // assert contract, don't freez
 Session log (per session):
 
 - **`seq` strictly increases** — the spine of replay equivalence.
+- **surface provenance is valid** — `sourceEventSeqs` uses the shared `dsh-session` checker for type eligibility, nonempty unique earlier references, and complete replacement coverage.
 - **turns pair and nest** — `turn/start` opens a turn, `turn/end` closes the matching one; no overlapping turns.
 - **steps nest in turns** — `step/start` opens a step in the open turn; `step/end` closes the matching step.
 - **chunks belong to an open step** — `step/start` precedes its `assistant/chunk`s.

packages/support/invariants/src/index.ts

@@ -7,7 +7,8 @@
  * `session/event`, and `agent/status`. It is **off in production**: enable it
  * in tests and the demos, where a contract violation should be a loud failure,
  * not a subtle one. It doubles as executable documentation of the event
- * taxonomy: the assertions below ARE the contract.
+ * taxonomy: these assertions and the shared session validators they invoke
+ * are the contract.
  *
  * Why runtime assertions instead of compile-time deep-readonly types? See
  * the dev-invariants RFC. Briefly: a `DeepReadonly<SessionEvent>` is high type-noise across
@@ -23,7 +24,13 @@ import type { Context } from 'cordis'
 import { HarnessError } from '@deepseek-ai/dsh-llm'
 import type { CallId, GenerateOptions } from '@deepseek-ai/dsh-llm'
 import type { Agent, AgentStatus } from '@deepseek-ai/dsh-agent'
-import { Session, SessionId, foldRequestHeader } from '@deepseek-ai/dsh-session'
+import {
+  Session,
+  SessionId,
+  foldRequestHeader,
+  isSurfaceEligibleType,
+  validateSurfaceProvenance,
+} from '@deepseek-ai/dsh-session'
 import type { SessionEvent, SurfaceEventType } from '@deepseek-ai/dsh-session'
 
 export const name = 'invariants'
@@ -121,71 +128,50 @@ function checkEvent(trace: SessionTrace, event: SessionEvent): void {
   trace.lastSeq = event.seq
 
   // --- Surface invariants ---
-  // Surface metadata (sourceEventSeqs, surfaceOp) is only valid on
-  // surface-eligible event types. The compiler enforces this at append()
-  // call sites; this runtime check catches casts and persisted data.
-  const SURFACE_TYPES = new Set<string>(['user/message', 'assistant/message', 'tool/result', 'context/message', 'steering/message'])
   // Cast to surface-eligible event type so we can access surfaceOp and
   // sourceEventSeqs (optional on SessionEvent, mandatory on SurfaceEvent).
   // SurfaceEvent's mandatory surfaceOp is too strict here — we need to
   // CHECK whether surface metadata is present, not assume it.
   const se = event as SessionEvent<SurfaceEventType>
-  if (!SURFACE_TYPES.has(event.type)) {
-    if (se.sourceEventSeqs !== undefined) {
-      throw new InvariantError(`${event.type} cannot carry sourceEventSeqs (non-surface event)`)
-    }
-    if (se.surfaceOp !== undefined) {
-      throw new InvariantError(`${event.type} cannot carry surfaceOp (non-surface event)`)
-    }
-  }
-  if (se.sourceEventSeqs !== undefined) {
-    if (se.sourceEventSeqs.length === 0) {
-      throw new InvariantError('sourceEventSeqs must not be empty when present')
-    }
-    const unique = new Set(se.sourceEventSeqs)
-    if (unique.size !== se.sourceEventSeqs.length) {
-      throw new InvariantError('sourceEventSeqs must not contain duplicates')
-    }
-    for (const ref of se.sourceEventSeqs) {
-      if (ref >= event.seq) {
-        throw new InvariantError(`sourceEventSeqs must reference earlier events: ${ref} >= current seq ${event.seq}`)
-      }
-      if (!trace.knownSeqs.has(ref)) {
-        throw new InvariantError(`sourceEventSeqs references unknown seq ${ref}`)
-      }
-    }
+  if (!isSurfaceEligibleType(event.type) && se.surfaceOp !== undefined) {
+    throw new InvariantError(`${event.type} cannot carry surfaceOp (non-surface event)`)
   }
+
   // Fold this event into the tracked surface linked list, validating the
   // replace contract as we go. `append` adds a tail node; `replace` shadows a
   // positional range — every shadowed node must appear in sourceEventSeqs.
-  if (se.surfaceOp !== undefined) {
-    if (se.surfaceOp === 'append') {
-      trace.surface.push(event.seq)
-    } else {
-      const { start, end } = se.surfaceOp
-      const startIdx = trace.surface.indexOf(start)
-      if (startIdx === -1) {
-        throw new InvariantError(`surface replace: start seq ${start} is not on the surface`)
-      }
-      const endIdx = trace.surface.indexOf(end)
-      if (endIdx === -1) {
-        throw new InvariantError(`surface replace: end seq ${end} is not on the surface`)
-      }
-      if (startIdx > endIdx) {
-        throw new InvariantError(`surface replace: start seq ${start} (pos ${startIdx}) is after end seq ${end} (pos ${endIdx}) on the surface`)
-      }
-      // Every node the replace shadows (surface positions [startIdx, endIdx]
-      // inclusive) must appear in sourceEventSeqs — the provenance contract.
-      const shadowed = trace.surface.slice(startIdx, endIdx + 1)
-      const recorded = new Set(se.sourceEventSeqs ?? [])
-      const missing = shadowed.filter(seq => !recorded.has(seq))
-      if (missing.length > 0) {
-        throw new InvariantError(`surface replace: sourceEventSeqs must include every shadowed surface node; missing ${missing.join(', ')}`)
-      }
-      // Apply the replace to the tracked surface: the new node takes the
-      // range's position so order stays in sync for later replaces.
-      trace.surface.splice(startIdx, shadowed.length, event.seq)
+  let replacement: { startIdx: number; shadowed: number[] } | undefined
+  if (se.surfaceOp !== undefined && se.surfaceOp !== 'append') {
+    const { start, end } = se.surfaceOp
+    const startIdx = trace.surface.indexOf(start)
+    if (startIdx === -1) {
+      throw new InvariantError(`surface replace: start seq ${start} is not on the surface`)
     }
+    const endIdx = trace.surface.indexOf(end)
+    if (endIdx === -1) {
+      throw new InvariantError(`surface replace: end seq ${end} is not on the surface`)
+    }
+    if (startIdx > endIdx) {
+      throw new InvariantError(`surface replace: start seq ${start} (pos ${startIdx}) is after end seq ${end} (pos ${endIdx}) on the surface`)
+    }
+    replacement = { startIdx, shadowed: trace.surface.slice(startIdx, endIdx + 1) }
+  }
+
+  const provenanceViolation = validateSurfaceProvenance(
+    event,
+    trace.knownSeqs,
+    replacement?.shadowed,
+  )
+  if (provenanceViolation !== undefined) {
+    throw new InvariantError(provenanceViolation)
+  }
+
+  if (se.surfaceOp === 'append') {
+    trace.surface.push(event.seq)
+  } else if (replacement !== undefined) {
+    // The new node takes the replaced range's position so order stays in sync
+    // for later replacements.
+    trace.surface.splice(replacement.startIdx, replacement.shadowed.length, event.seq)
   }
 
   // Boundary/step-scoped events have explicit cases; every OTHER event type —