diff --git a/api-surface.json b/api-surface.json
index 72fad47..19c0622 100644
--- a/api-surface.json
+++ b/api-surface.json
@@ -472,7 +472,7 @@
       "RunRetrievalImprovementLoopOptions": "value f7fa1827ff47",
       "RunRetrievalImprovementLoopResult": "value 21f0b2d53f0d",
       "RunScopedStores": "value 88be8b4eed2e",
-      "RunScopedStoresOptions": "value 5c0af586c64d",
+      "RunScopedStoresOptions": "value b04713afaad9",
       "RunSerializedKnowledgeOptimizationOptions": "value 648af65b3525",
       "RunSerializedKnowledgeOptimizationResult": "value 6159e2cc058c",
       "SCAFFOLD_PAGE_BASENAMES": "value 373728f5643d",
diff --git a/docs/run-scoped-citations.md b/docs/run-scoped-citations.md
index f88e2c7..2d29fae 100644
--- a/docs/run-scoped-citations.md
+++ b/docs/run-scoped-citations.md
@@ -86,6 +86,14 @@ A read-only authority must already contain the lineage before `init()` is called
 
 The default file-backed authority is idempotent. Reopening a run with the same parent is accepted; reopening it with another parent is a lineage conflict.
 
+### Read budgets
+
+A finite lineage is not invalid merely because it contains many runs. Ancestry reads have no
+implicit depth cutoff. Supply `maxAncestors` to `createRunScopedStores` when the caller needs a
+read budget, including `0` for a root-only view. A chain exactly at that bound is accepted; a
+longer chain is refused explicitly rather than truncated. Cycles, invalid run identities,
+conflicting parents, and path-containment checks remain enforced independently of that budget.
+
 ## Lint and graph behavior
 
 `auditCurrentRunCitations()` checks current-run pages against one materialized visibility chain. `lintCurrentRunCitations()` converts missing, ambiguous, and self-citations into blocking package lint findings.
diff --git a/package.json b/package.json
index 03af874..52abb6e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@tangle-network/agent-knowledge",
-  "version": "16.0.1",
+  "version": "17.0.0",
   "description": "Build, search, evaluate, and improve source-backed knowledge bases.",
   "homepage": "https://github.com/tangle-network/agent-knowledge#readme",
   "repository": {
diff --git a/src/run-scoped.test.ts b/src/run-scoped.test.ts
index 7c5fbf6..037a246 100644
--- a/src/run-scoped.test.ts
+++ b/src/run-scoped.test.ts
@@ -166,6 +166,7 @@ describe('createRunScopedStores', () => {
     }
     const stores = createRunScopedStores({
       root,
+      maxAncestors: 64,
       lineageAuthority: {
         async parentOf(runId) {
           return parents.get(runId) ?? null
@@ -183,6 +184,7 @@ describe('createRunScopedStores', () => {
     }
     const stores = createRunScopedStores({
       root,
+      maxAncestors: 64,
       lineageAuthority: {
         async parentOf(runId) {
           return parents.get(runId) ?? null
@@ -190,6 +192,58 @@ describe('createRunScopedStores', () => {
       },
     })
 
-    await expect(stores.lineage('run-0')).rejects.toThrow(/exceeds 64 ancestors/)
+    await expect(stores.lineage('run-0')).rejects.toThrow(/exceeds caller maxAncestors=64/)
+  })
+
+  it('reads a long finite lineage without a source-level ancestry ceiling', async () => {
+    const stores = createRunScopedStores({
+      root,
+      lineageAuthority: {
+        async parentOf(runId) {
+          const index = Number(runId.slice(4))
+          return index === 256 ? null : `run-${index + 1}`
+        },
+      },
+    })
+    const lineage = await stores.lineage('run-0')
+    expect(lineage).toHaveLength(256)
+    expect(lineage[255]).toBe('run-256')
+  })
+
+  it('reads an actual inherited page beyond the old 64-ancestor cutoff', async () => {
+    const stores = createRunScopedStores({ root })
+    await Promise.all(
+      Array.from({ length: 66 }, (_, index) =>
+        stores.init(`run-${index}`, { parentRunId: index === 65 ? null : `run-${index + 1}` }),
+      ),
+    )
+    await addPage(stores.storePath('run-65'), 'retained.md', 'useful work from the first run')
+    const pages = await stores.loadChain('run-0')
+    expect(pages.find((entry) => entry.page.title === 'retained.md')).toMatchObject({
+      origin: 'inherited:run-65',
+    })
+  })
+
+  it.each([-1, 1.5, NaN, Infinity, null])(
+    'rejects malformed caller ancestry bounds (%s)',
+    (maxAncestors) => {
+      expect(() => createRunScopedStores({ root, maxAncestors: maxAncestors as number })).toThrow(
+        /non-negative safe integer/,
+      )
+    },
+  )
+
+  it('allows zero ancestors only for a root run', async () => {
+    const stores = createRunScopedStores({
+      root,
+      maxAncestors: 0,
+      lineageAuthority: {
+        async parentOf(id) {
+          return id === 'root' ? null : 'root'
+        },
+      },
+    })
+    await expect(stores.lineage('root')).resolves.toEqual([])
+    await expect(stores.lineage('child')).rejects.toThrow(/caller maxAncestors=0/)
   })
 })
diff --git a/src/run-scoped.ts b/src/run-scoped.ts
index 3f94cd1..8ad57dc 100644
--- a/src/run-scoped.ts
+++ b/src/run-scoped.ts
@@ -69,11 +69,11 @@ export interface RunScopedStoresOptions extends KnowledgePagesOptions {
   sharedRoot?: string
   /** External owner for run ancestry. Defaults to a record inside each run store. */
   lineageAuthority?: RunLineageAuthority
+  /** Optional caller-owned bound on ancestor reads. Omit to read the complete finite chain.
+   * Cycles and invalid identities are always refused; long valid history is not corruption. */
+  maxAncestors?: number
 }
 
-/** Ancestry beyond this bound is invalid durable state. */
-const MAX_LINEAGE_HOPS = 64
-
 export interface RunScopedStores {
   /** Create or open a run store and bind it to one exact parent identity. */
   init(runId: string, options?: { parentRunId?: string | null }): Promise<KnowledgeLayout>
@@ -103,6 +103,10 @@ export function createRunScopedStores(options: RunScopedStoresOptions): RunScope
   if (options.runStorePath !== undefined && typeof options.runStorePath !== 'function') {
     throw new TypeError('createRunScopedStores runStorePath must be a function when present')
   }
+  const maxAncestors = options.maxAncestors
+  if (maxAncestors !== undefined && (!Number.isSafeInteger(maxAncestors) || maxAncestors < 0)) {
+    throw new TypeError('createRunScopedStores maxAncestors must be a non-negative safe integer')
+  }
   if (options.lineageAuthority !== undefined) validateLineageAuthority(options.lineageAuthority)
   const pagesDirectory = normalizePagesDirectory(options.pagesDirectory)
 
@@ -116,20 +120,21 @@ export function createRunScopedStores(options: RunScopedStoresOptions): RunScope
     const chain: string[] = []
     const seen = new Set<string>([runId])
     let current = runId
-    // One query more than the bound: a chain of exactly MAX_LINEAGE_HOPS
-    // ancestors needs the terminating null query to prove it ends.
-    for (let hop = 0; hop <= MAX_LINEAGE_HOPS; hop += 1) {
+    // The terminating null is read even at an explicit bound: an exactly-full chain is valid.
+    for (;;) {
       const parent = await authority.parentOf(current)
       if (parent === null) return chain
       assertRunId(parent, `parent of '${current}'`)
       if (seen.has(parent)) {
         throw new Error(`run lineage cycle: ${parent} is its own ancestor (via ${runId})`)
       }
+      if (maxAncestors !== undefined && chain.length >= maxAncestors) {
+        throw new Error(`run lineage for '${runId}' exceeds caller maxAncestors=${maxAncestors}`)
+      }
       seen.add(parent)
       chain.push(parent)
       current = parent
     }
-    throw new Error(`run lineage for '${runId}' exceeds ${MAX_LINEAGE_HOPS} ancestors`)
   }
 
   return {