diff --git a/docs/config-catalog.md b/docs/config-catalog.md
index 1a1e8df228..9099f99b85 100644
--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -108,7 +108,7 @@ export interface Config {
 
 Depends on: [`AgentOptions`](core-data-structures/core.md) · [`SessionId`](core-data-structures/core.md)
 
-Source: [`packages/core/agent-loop/src/index.ts:235`](../packages/core/agent-loop/src/index.ts)
+Source: [`packages/core/agent-loop/src/index.ts:236`](../packages/core/agent-loop/src/index.ts)
 
 ## `@deepseek-ai/dsh-agent-spine-demo`
 
diff --git a/packages/session-persistence/session-persistence/src/coordinator.ts b/packages/session-persistence/session-persistence/src/coordinator.ts
index ee6eeb6b8c..40412776b1 100644
--- a/packages/session-persistence/session-persistence/src/coordinator.ts
+++ b/packages/session-persistence/session-persistence/src/coordinator.ts
@@ -16,7 +16,7 @@ import {
 } from '@deepseek-ai/dsh-session'
 import type { Session, SessionEvent, SessionId, SessionHeader } from '@deepseek-ai/dsh-session'
 import type { SessionInspection } from './index.ts'
-import { SessionPreparations } from './preparations.ts'
+import { observeQueuedAbort, SessionPreparations } from './preparations.ts'
 import type { SessionPreparationReservation } from './preparations.ts'
 
 /** Default number of detached session preparations retained by a coordinator. */
@@ -1191,50 +1191,3 @@ export class PersistenceCoordinator<TornMarker = unknown> {
     live.pending.splice(0, batch.length)
   }
 }
-
-/**
- * Give an observation caller a prompt cancellation view of queued work.
- *
- * The serialized `operation` remains in the same-id chain and checks the signal
- * before invoking backend work. Observing its settlement here therefore cannot
- * detach a storage read or let a later operation overtake its predecessor.
- */
-function observeQueuedAbort<T>(
-  operation: Promise<T>,
-  signal: AbortSignal,
-  started: () => boolean,
-): Promise<T> {
-  return new Promise<T>((resolve, reject) => {
-    let settled = false
-    const finish = (callback: () => void): void => {
-      if (settled) return
-      settled = true
-      signal.removeEventListener('abort', onAbort)
-      callback()
-    }
-    const onAbort = (): void => {
-      if (started()) return
-      finish(() => {
-        try {
-          signal.throwIfAborted()
-        } catch (reason: unknown) {
-          rejectObservation(reject, reason)
-          return
-        }
-        /* v8 ignore next -- a native AbortSignal emits abort only after becoming aborted */
-        reject(new Error('persistence observation abort event lacked an aborted signal'))
-      })
-    }
-    signal.addEventListener('abort', onAbort, { once: true })
-    operation.then(
-      (value) => { finish(() => { resolve(value) }) },
-      (reason: unknown) => { finish(() => { rejectObservation(reject, reason) }) },
-    )
-    if (signal.aborted) onAbort()
-  })
-}
-
-/** Preserve an exact provider or AbortSignal reason, including legacy non-Error values. */
-function rejectObservation(reject: (reason?: unknown) => void, reason: unknown): void {
-  reject(reason)
-}
diff --git a/packages/session-persistence/session-persistence/src/preparations.ts b/packages/session-persistence/session-persistence/src/preparations.ts
index 1df7c7d79b..5eb1593321 100644
--- a/packages/session-persistence/session-persistence/src/preparations.ts
+++ b/packages/session-persistence/session-persistence/src/preparations.ts
@@ -79,9 +79,9 @@ export class SessionPreparations<Source extends PreparedSource, CommitState> {
     signal?: AbortSignal,
   ): Promise<SessionPreparationReservation<Source, CommitState> | undefined> {
     const { entry, created } = this.entryFor(id, load)
-    const loaded = signal === undefined || created
-      ? await entry.result
-      : await observeQueuedAbort(entry.result, signal)
+    await (signal === undefined || created
+      ? entry.result
+      : observeQueuedAbort(entry.result, signal))
     while (this.entries.get(id) === entry && entry.phase !== 'ready') {
       const settled = entry.reservationSettled
       /* v8 ignore next -- committing/reserved transitions install this waiter synchronously. */
@@ -90,7 +90,7 @@ export class SessionPreparations<Source extends PreparedSource, CommitState> {
       else await observeQueuedAbort(settled, signal)
     }
     if (this.entries.get(id) !== entry) return undefined
-    const source = entry.source ?? loaded
+    const source = entry.source as Source
     const reservationSettled = Promise.withResolvers<void>()
     entry.phase = 'committing'
     entry.reservationSettled = reservationSettled.promise
@@ -252,7 +252,6 @@ export class SessionPreparations<Source extends PreparedSource, CommitState> {
   }
 
   private touch(entry: PreparationEntry<Source, CommitState>): void {
-    if (this.entries.get(entry.id) !== entry || entry.phase !== 'ready') return
     this.entries.delete(entry.id)
     this.entries.set(entry.id, entry)
     let readyCount = 0
@@ -263,14 +262,23 @@ export class SessionPreparations<Source extends PreparedSource, CommitState> {
     for (const [id, candidate] of this.entries) {
       if (candidate.phase !== 'ready') continue
       this.entries.delete(id)
-      readyCount -= 1
-      if (readyCount <= this.capacity) break
+      return
     }
   }
 }
 
-/** Give a queued observer a prompt cancellation view without cancelling shared work. */
-function observeQueuedAbort<T>(operation: Promise<T>, signal: AbortSignal): Promise<T> {
+/**
+ * Give a queued observer a prompt cancellation view without cancelling shared work.
+ * @param operation - shared operation whose settlement remains authoritative.
+ * @param signal - observer-local cancellation signal.
+ * @param started - whether the operation has crossed its cancellation cutoff.
+ * @returns the operation result or the observer's prompt cancellation.
+ */
+export function observeQueuedAbort<T>(
+  operation: Promise<T>,
+  signal: AbortSignal,
+  started: () => boolean = () => false,
+): Promise<T> {
   return new Promise<T>((resolve, reject) => {
     let settled = false
     const finish = (callback: () => void): void => {
@@ -280,22 +288,23 @@ function observeQueuedAbort<T>(operation: Promise<T>, signal: AbortSignal): Prom
       callback()
     }
     const onAbort = (): void => {
+      if (started()) return
       finish(() => {
         try {
           signal.throwIfAborted()
         } catch (reason: unknown) {
-          rejectPreparationObservation(reject, reason)
+          rejectObservation(reject, reason)
           return
         }
         /* v8 ignore next -- a native AbortSignal emits abort only after becoming aborted. */
-        reject(new Error('preparation observation abort event lacked an aborted signal'))
+        reject(new Error('queued observation abort event lacked an aborted signal'))
       })
     }
     signal.addEventListener('abort', onAbort, { once: true })
     operation.then(
       (value) => { finish(() => { resolve(value) }) },
       (reason: unknown) => {
-        finish(() => { rejectPreparationObservation(reject, reason) })
+        finish(() => { rejectObservation(reject, reason) })
       },
     )
     if (signal.aborted) onAbort()
@@ -303,6 +312,6 @@ function observeQueuedAbort<T>(operation: Promise<T>, signal: AbortSignal): Prom
 }
 
 /** Preserve an exact loader or AbortSignal reason, including legacy non-Error values. */
-function rejectPreparationObservation(reject: (reason?: unknown) => void, reason: unknown): void {
+function rejectObservation(reject: (reason?: unknown) => void, reason: unknown): void {
   reject(reason)
 }
diff --git a/packages/session-persistence/session-persistence/tests/preparations.spec.ts b/packages/session-persistence/session-persistence/tests/preparations.spec.ts
new file mode 100644
index 0000000000..dee919c798
--- /dev/null
+++ b/packages/session-persistence/session-persistence/tests/preparations.spec.ts
@@ -0,0 +1,267 @@
+/** Unit coverage for unpublished Session preparation ownership and sharing. */
+
+import { describe, expect, it, vi } from 'vitest'
+import { Session, SessionId } from '@deepseek-ai/dsh-session'
+import { observeQueuedAbort, SessionPreparations } from '../src/preparations.ts'
+
+interface PreparedSource {
+  readonly session: Session
+  readonly label: string
+}
+
+function prepared(label: string): PreparedSource {
+  return { session: Session.create(SessionId(label)), label }
+}
+
+function committed(source: PreparedSource): Promise<{ source: PreparedSource; state: string }> {
+  return Promise.resolve({ source, state: source.label })
+}
+
+describe('SessionPreparations inspection', () => {
+  it('shares in-flight and ready sources, then invalidates them', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(2)
+    const id = SessionId('shared-inspection')
+    const gate = Promise.withResolvers<PreparedSource>()
+    const load = vi.fn(() => gate.promise)
+    const first = preparations.inspect(id, load)
+    const second = preparations.inspect(id, load, new AbortController().signal)
+    const source = prepared(id)
+
+    expect(preparations.has(id)).toBe(true)
+    gate.resolve(source)
+    await expect(first).resolves.toBe(source)
+    await expect(second).resolves.toBe(source)
+    await expect(preparations.inspect(id, load)).resolves.toBe(source)
+    expect(load).toHaveBeenCalledOnce()
+
+    preparations.invalidate(id)
+    preparations.invalidate(id)
+    expect(preparations.has(id)).toBe(false)
+  })
+
+  it('removes failed and invalidated in-flight loads without changing their observers', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const failedId = SessionId('failed-inspection')
+    const failure = new Error('load failed')
+    await expect(preparations.inspect(failedId, () => Promise.reject(failure))).rejects.toBe(failure)
+    expect(preparations.has(failedId)).toBe(false)
+
+    const invalidatedId = SessionId('invalidated-inspection')
+    const gate = Promise.withResolvers<PreparedSource>()
+    const inspection = preparations.inspect(invalidatedId, () => gate.promise)
+    preparations.invalidate(invalidatedId)
+    const source = prepared(invalidatedId)
+    gate.resolve(source)
+    await expect(inspection).resolves.toBe(source)
+    expect(preparations.has(invalidatedId)).toBe(false)
+
+    const rejectedId = SessionId('invalidated-rejection')
+    const rejectedGate = Promise.withResolvers<PreparedSource>()
+    const rejected = preparations.inspect(rejectedId, () => rejectedGate.promise)
+    preparations.invalidate(rejectedId)
+    rejectedGate.reject(failure)
+    await expect(rejected).rejects.toBe(failure)
+  })
+
+  it('evicts ready entries while leaving reserved entries alone', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const reservedA = await preparations.reserve(
+      SessionId('reserved-a'),
+      () => Promise.resolve(prepared('reserved-a')),
+      committed,
+    )
+    const reservedB = await preparations.reserve(
+      SessionId('reserved-b'),
+      () => Promise.resolve(prepared('reserved-b')),
+      committed,
+    )
+    expect(reservedA).toBeDefined()
+    expect(reservedB).toBeDefined()
+
+    await preparations.inspect(SessionId('ready-c'), () => Promise.resolve(prepared('ready-c')))
+    preparations.release(reservedA!, true)
+    expect(preparations.has(SessionId('reserved-b'))).toBe(true)
+    expect(preparations.has(SessionId('ready-c'))).toBe(false)
+    expect(preparations.has(SessionId('reserved-a'))).toBe(true)
+
+    preparations.discard(reservedB!)
+    preparations.invalidate(SessionId('reserved-a'))
+  })
+})
+
+describe('SessionPreparations reservation', () => {
+  it('waits for an existing reservation, republishes the exact Session, and attaches once', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(2)
+    const id = SessionId('reservation-wait')
+    const source = prepared(id)
+    const first = await preparations.reserve(id, () => Promise.resolve(source), committed)
+    expect(first).toBeDefined()
+    expect(preparations.reservationFor(source.session)).toBe(first)
+    expect(() => preparations.reservationFor(Session.create(id))).toThrow(/cannot publish/)
+    expect(() => preparations.assertWritable(id)).toThrow(/is reserved/)
+
+    let secondSettled = false
+    const secondPromise = preparations.reserve(id, () => Promise.resolve(prepared('unused')), committed)
+      .then((reservation) => {
+        secondSettled = true
+        return reservation
+      })
+    await Promise.resolve()
+    await Promise.resolve()
+    await Promise.resolve()
+    expect(secondSettled).toBe(false)
+
+    preparations.release(first!, true)
+    const second = await secondPromise
+    expect(second?.source).toBe(source)
+    preparations.attach(second!)
+    expect(preparations.reservationFor(source.session)).toBeUndefined()
+    expect(() => preparations.attach(second!)).toThrow(/no longer reserved/)
+    preparations.discard(second!)
+    preparations.release(second!, true)
+    expect(() => preparations.assertWritable(id)).not.toThrow()
+  })
+
+  it('supports abortable reservation waits without cancelling the held reservation', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('abortable-reservation-wait')
+    const first = await preparations.reserve(id, () => Promise.resolve(prepared(id)), committed)
+    const controller = new AbortController()
+    const reason = { kind: 'cancelled' }
+    const waiting = preparations.reserve(id, () => Promise.resolve(prepared('unused')), committed, controller.signal)
+
+    await Promise.resolve()
+    await Promise.resolve()
+    await Promise.resolve()
+    controller.abort(reason)
+    await expect(waiting).rejects.toBe(reason)
+    expect(preparations.reservationFor(first!.source.session)).toBe(first)
+    preparations.release(first!, false)
+    expect(preparations.has(id)).toBe(false)
+  })
+
+  it('removes a failed commit and wakes another waiter as invalidated', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('failed-commit')
+    const commitStarted = Promise.withResolvers<undefined>()
+    const commitGate = Promise.withResolvers<{ source: PreparedSource; state: string }>()
+    const source = prepared(id)
+    const failure = new Error('commit failed')
+    const first = preparations.reserve(id, () => Promise.resolve(source), () => {
+      commitStarted.resolve(undefined)
+      return commitGate.promise
+    })
+    await commitStarted.promise
+    expect(() => preparations.assertWritable(id)).toThrow(/is reserved/)
+    const second = preparations.reserve(id, () => Promise.resolve(prepared('unused')), committed)
+
+    commitGate.reject(failure)
+    await expect(first).rejects.toBe(failure)
+    await expect(second).resolves.toBeUndefined()
+    expect(preparations.has(id)).toBe(false)
+  })
+
+  it('returns a post-commit cancellation to the ready pool', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('post-commit-cancel')
+    const source = prepared(id)
+    const controller = new AbortController()
+    const reason = new Error('cancel after commit')
+
+    await expect(preparations.reserve(id, () => Promise.resolve(source), async value => {
+      controller.abort(reason)
+      return { source: value, state: value.label }
+    }, controller.signal)).rejects.toBe(reason)
+
+    expect(preparations.takeReady(id)).toBe(source)
+    expect(preparations.takeReady(id)).toBeUndefined()
+  })
+
+  it('does not revive an invalidated commit after post-commit cancellation', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('invalidated-commit-cancel')
+    const source = prepared(id)
+    const commitStarted = Promise.withResolvers<undefined>()
+    const commitGate = Promise.withResolvers<undefined>()
+    const controller = new AbortController()
+    const reason = new Error('cancel invalidated commit')
+    const reservation = preparations.reserve(id, () => Promise.resolve(source), async value => {
+      commitStarted.resolve(undefined)
+      await commitGate.promise
+      return { source: value, state: value.label }
+    }, controller.signal)
+
+    await commitStarted.promise
+    preparations.invalidate(id)
+    controller.abort(reason)
+    commitGate.resolve(undefined)
+    await expect(reservation).rejects.toBe(reason)
+    expect(preparations.has(id)).toBe(false)
+  })
+
+  it('returns undefined when a load is invalidated before reservation', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('invalidated-reservation')
+    const gate = Promise.withResolvers<PreparedSource>()
+    const reservation = preparations.reserve(id, () => gate.promise, committed)
+    preparations.invalidate(id)
+    gate.resolve(prepared(id))
+    await expect(reservation).resolves.toBeUndefined()
+  })
+
+  it('rejects pending adoption and accepts a ready source exactly once', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const id = SessionId('take-ready')
+    const gate = Promise.withResolvers<PreparedSource>()
+    const inspection = preparations.inspect(id, () => gate.promise)
+    expect(() => preparations.takeReady(id)).toThrow(/preparation is pending/)
+    const source = prepared(id)
+    gate.resolve(source)
+    await inspection
+    expect(preparations.takeReady(id)).toBe(source)
+    expect(preparations.takeReady(id)).toBeUndefined()
+  })
+
+  it('rejects publication while only an inspection exists', async () => {
+    const preparations = new SessionPreparations<PreparedSource, string>(1)
+    const source = prepared('inspection-publication')
+    await preparations.inspect(source.session.id, () => Promise.resolve(source))
+    expect(() => preparations.reservationFor(source.session)).toThrow(/cannot publish/)
+  })
+})
+
+describe('observeQueuedAbort', () => {
+  it('relays fulfillment and rejection exactly', async () => {
+    const signal = new AbortController().signal
+    await expect(observeQueuedAbort(Promise.resolve('value'), signal)).resolves.toBe('value')
+    const failure = { kind: 'failed' }
+    await expect(observeQueuedAbort(Promise.reject(failure), signal)).rejects.toBe(failure)
+  })
+
+  it('rejects promptly with an exact abort reason and ignores later settlement', async () => {
+    const operation = Promise.withResolvers<string>()
+    const controller = new AbortController()
+    const reason = { kind: 'aborted' }
+    const observed = observeQueuedAbort(operation.promise, controller.signal)
+    controller.abort(reason)
+    await expect(observed).rejects.toBe(reason)
+    operation.resolve('late')
+    await Promise.resolve()
+  })
+
+  it('observes a pre-aborted signal through the default start predicate', async () => {
+    const controller = new AbortController()
+    controller.abort('pre-aborted')
+    await expect(observeQueuedAbort(new Promise<never>(() => {}), controller.signal))
+      .rejects.toBe('pre-aborted')
+  })
+
+  it('lets an operation that already started own cancellation settlement', async () => {
+    const operation = Promise.withResolvers<string>()
+    const controller = new AbortController()
+    const observed = observeQueuedAbort(operation.promise, controller.signal, () => true)
+    controller.abort(new Error('too late'))
+    operation.resolve('owned')
+    await expect(observed).resolves.toBe('owned')
+  })
+})