fix(client): harden nested Tool call projection

packages/client/runtime/src/client/sessions/tool-call-tree.ts

@@ -10,9 +10,9 @@ interface ProjectedBlock {
   value: ToolCallBlock
 }
 
-function sameBlocks(
-  left: readonly ToolCallBlock[],
-  right: readonly ToolCallBlock[],
+function sameReferences<T>(
+  left: readonly T[],
+  right: readonly T[],
 ): boolean {
   return left.length === right.length
     && left.every((block, index) => block === right[index])
@@ -68,6 +68,7 @@ export class ToolCallTree {
         subCalls: [],
       }
       const siblings = this.childrenByParent.get(data.parentCallId) ?? []
+      if (this.wouldCreateCycle(data.parentCallId, data.subCallId)) return true
       this.childrenByParent.set(data.parentCallId, [...siblings, running])
       this.revision++
       return true
@@ -83,6 +84,7 @@ export class ToolCallTree {
     }
     const siblings = this.childrenByParent.get(data.parentCallId) ?? []
     const at = siblings.findIndex(sub => sub.callId === data.subCallId)
+    if (at === -1 && this.wouldCreateCycle(data.parentCallId, data.subCallId)) return true
     const started = at === -1 ? undefined : siblings[at]
     const settled: ToolResultNode = {
       kind: 'tool-result',
@@ -116,14 +118,11 @@ export class ToolCallTree {
     if (this.nodesCache?.source === nodes && this.nodesCache.revision === this.revision) {
       return this.nodesCache.value
     }
-    let changed = false
     const projected = nodes.map((node): ConversationNode => {
       if (node.kind !== 'tool-result') return node
-      const value = this.projectBlock(node) as ToolResultNode
-      changed ||= value !== node
-      return value
+      return this.projectBlock(node) as ToolResultNode
     })
-    const value = changed ? projected : nodes
+    const value = sameReferences(nodes, projected) ? nodes : projected
     this.nodesCache = { source: nodes, revision: this.revision, value }
     return value
   }
@@ -137,13 +136,8 @@ export class ToolCallTree {
     if (this.runningCache?.source === calls && this.runningCache.revision === this.revision) {
       return this.runningCache.value
     }
-    let changed = false
-    const projected = calls.map((call): RunningToolCall => {
-      const value = this.projectBlock(call) as RunningToolCall
-      changed ||= value !== call
-      return value
-    })
-    const value = changed ? projected : calls
+    const projected = calls.map(call => this.projectBlock(call) as RunningToolCall)
+    const value = sameReferences(calls, projected) ? calls : projected
     this.runningCache = { source: calls, revision: this.revision, value }
     return value
   }
@@ -151,11 +145,11 @@ export class ToolCallTree {
   private projectBlock(block: ToolCallBlock): ToolCallBlock {
     const children = this.childrenByParent.get(block.callId) ?? block.subCalls
     const projectedChildren = children.map(child => this.projectBlock(child))
-    const childValue = sameBlocks(children, projectedChildren)
+    const childValue = sameReferences(children, projectedChildren)
       ? children
       : projectedChildren
     const cached = this.projectedByCall.get(block.callId)
-    if (cached?.source === block && sameBlocks(cached.children, childValue)) {
+    if (cached?.source === block && sameReferences(cached.children, childValue)) {
       return cached.value
     }
     const value: ToolCallBlock = block.subCalls === childValue
@@ -168,4 +162,19 @@ export class ToolCallTree {
     })
     return value
   }
+
+  private wouldCreateCycle(parentCallId: string, subCallId: string): boolean {
+    if (parentCallId === subCallId) return true
+    const pending = [subCallId]
+    const visited = new Set(pending)
+    for (const callId of pending) {
+      for (const child of this.childrenByParent.get(callId) ?? []) {
+        if (child.callId === parentCallId) return true
+        if (visited.has(child.callId)) continue
+        visited.add(child.callId)
+        pending.push(child.callId)
+      }
+    }
+    return false
+  }
 }

packages/client/runtime/tests/history-fold.spec.ts

@@ -168,6 +168,37 @@ describe('projectConversationHistory', () => {
     })
   })
 
+  it('projects nested dispatches onto settled and interrupted history calls', () => {
+    const projection = projectConversationHistory([
+      ev.turnStart(0, 1),
+      ev.toolCall(1, 1, 'settled', 'run_code', '{}'),
+      ev.codeDispatchStart(2, 'settled', 1, 'run_code', { code: 'nested' }),
+      ev.codeDispatchStart(3, 'settled:code:1', 1, 'read', { path: 'a.txt' }),
+      ev.codeDispatch(4, 'settled:code:1', 1, 'read', { path: 'a.txt' }, 'alpha'),
+      ev.codeDispatch(5, 'settled', 1, 'run_code', { code: 'nested' }, 'alpha'),
+      ev.toolResult(6, 1, 'settled', 'done'),
+      ev.turnEnd(7, 1),
+      ev.turnStart(8, 2),
+      ev.toolCall(9, 2, 'interrupted', 'run_code', '{}'),
+      ev.codeDispatchStart(10, 'interrupted', 1, 'bash', { command: 'sleep 1' }),
+      ev.turnEnd(11, 2, 'aborted'),
+    ].map(event => ({ event })))
+
+    const settled = {
+      callId: 'settled',
+      subCalls: [{
+        callId: 'settled:code:1',
+        subCalls: [{ callId: 'settled:code:1:code:1', call: { name: 'read' } }],
+      }],
+    }
+    expect(projection.eventNodes).toMatchObject([settled])
+    expect(projection.contexts[0]?.nodes).toMatchObject([settled])
+    expect(projection.interruptedNodes).toMatchObject([{
+      callId: 'interrupted',
+      subCalls: [{ callId: 'interrupted:code:1', name: 'bash' }],
+    }])
+  })
+
   it('drops completed token payloads without changing inspection projections', () => {
     const events = [
       ev.user(0, 'before'),

packages/client/runtime/tests/tool-call-tree.spec.ts

@@ -0,0 +1,65 @@
+import type { SessionEvent } from '@deepseek-ai/dsh-session/types'
+import { describe, expect, it } from 'vitest'
+import type { RunningToolCall } from '../src/client/sessions/conversation.ts'
+import { ToolCallTree } from '../src/client/sessions/tool-call-tree.ts'
+
+const at = (seq: number, type: string, data: Record<string, unknown>): SessionEvent =>
+  ({ seq, time: 1_700_000_000_000 + seq, type, data }) as unknown as SessionEvent
+
+const start = (seq: number, parentCallId: string, subCallId: string): SessionEvent =>
+  at(seq, 'tool/code-dispatch-start', {
+    parentCallId, subCallId, name: 'run_code', arguments: {},
+  })
+
+const settle = (seq: number, parentCallId: string, subCallId: string): SessionEvent =>
+  at(seq, 'tool/code-dispatch', {
+    parentCallId, subCallId, name: 'run_code', arguments: {},
+    isError: false, content: [],
+  })
+
+const root = (callId: string): RunningToolCall => ({
+  callId, name: 'run_code', argsRaw: '{}', turn: 1, step: 1,
+  time: 1_700_000_000_000, callView: null, subCalls: [],
+})
+
+describe('ToolCallTree', () => {
+  it('rejects a self-parenting dispatch edge', () => {
+    const tree = new ToolCallTree()
+    const roots = [root('root')]
+
+    expect(tree.apply(start(0, 'root', 'root'))).toBe(true)
+    expect(tree.projectRunningCalls(roots)).toBe(roots)
+  })
+
+  it('rejects a settling edge that would close a multi-call cycle', () => {
+    const tree = new ToolCallTree()
+    tree.apply(start(0, 'a', 'b'))
+    tree.apply(start(1, 'b', 'c'))
+
+    expect(tree.apply(settle(2, 'c', 'a'))).toBe(true)
+    expect(tree.projectRunningCalls([root('a')])).toMatchObject([{
+      callId: 'a',
+      subCalls: [{
+        callId: 'b',
+        subCalls: [{ callId: 'c', subCalls: [] }],
+      }],
+    }])
+  })
+
+  it('accepts an acyclic graph with a shared descendant', () => {
+    const tree = new ToolCallTree()
+    tree.apply(start(0, 'a', 'b'))
+    tree.apply(start(1, 'a', 'c'))
+    tree.apply(start(2, 'b', 'd'))
+    tree.apply(start(3, 'c', 'd'))
+
+    expect(tree.apply(start(4, 'root', 'a'))).toBe(true)
+    expect(tree.projectRunningCalls([root('root')])).toMatchObject([{
+      callId: 'root',
+      subCalls: [{
+        callId: 'a',
+        subCalls: [{ callId: 'b' }, { callId: 'c' }],
+      }],
+    }])
+  })
+})