[Unhandled Error] Cannot read properties of undefined (reading 'getRequests')

[vs-code-engineering]

Error Message

Cannot read properties of undefined (reading 'getRequests')

Stack Trace

    at PV._runFn (./src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:176:0)
    at PV._run (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:110:10)
    at PV.endUpdate (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:167:11)
    at xO.finish (./src/vs/base/common/observableInternal/transaction.ts:102:12)
    at Ni (./src/vs/base/common/observableInternal/transaction.ts:21:5)
    at transaction (./src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:245:0)
    at async a6._acceptEdits (./src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingSession.ts:1032:0)
    at async (./src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingSession.ts:569:0)
    at async (./src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingSession.ts:106:0)

Raw Stack Trace (minified)

TypeError: Cannot read properties of undefined (reading 'getRequests')     at PV._runFn (out/vs/sessions/sessions.desktop.main.js:2928:150556)     at PV._run (out/vs/sessions/sessions.desktop.main.js:407:6694)     at PV.endUpdate (out/vs/sessions/sessions.desktop.main.js:407:7325)     at xO.finish (out/vs/sessions/sessions.desktop.main.js:406:109976)     at Ni (out/vs/sessions/sessions.desktop.main.js:406:109176)     at gne.acceptAgentEdits (out/vs/sessions/sessions.desktop.main.js:2928:152777)     at async a6._acceptEdits (out/vs/sessions/sessions.desktop.main.js:2929:35536)     at async out/vs/sessions/sessions.desktop.main.js:2929:29116     at async Promise.all (index 0)     at async out/vs/sessions/sessions.desktop.main.js:2929:21124

Details

Property	Value
Bucket ID	f84bb2a1-2eb8-e678-164d-6f7e0a4da293
Version	1.116.0-insider
Commit	1ec46de1
Last Seen	Thu Apr 09 2026 23:51:54 GMT+0000 (Coordinated Universal Time)
Platforms	Windows, Mac
Product	Agents

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This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

Regression Details

• Product: Agents
• Regression type: New error
• Last release without this error: 1.116.0-insider (fc6d18c3)
• First release with this error: 1.116.0-insider (e4f6e114)
• Commit range: fc6d18c3...e4f6e114

Deminified Stack (top frames)

1. (anonymous) — src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:176
2. (anonymous) — src/vs/base/common/observableInternal/reactions/autorunImpl.ts:110
3. (anonymous) — src/vs/base/common/observableInternal/reactions/autorunImpl.ts:167
4. (anonymous) — src/vs/base/common/observableInternal/transaction.ts:102
5. acceptAgentEdits — src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:245
6. _acceptEdits — src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingSession.ts:1032

The error occurs during agent edit acceptance in chatEditingModifiedDocumentEntry.ts when getRequests is called on an undefined object. 16 users affected across Windows and Mac.

Related Bucket

Bucket 5e789596 (11 users) has the same getRequests error but through a different code path (chatEditingModifiedFileEntry.ts → _notifyAction → acceptStreamingEditsEnd), suggesting a shared root cause where the chat model is disposed before edits complete.

Generated by errors-agents-regression-scan · ● 5.9M · ◷

[vs-code-engineering]

🔍 Error Investigation

Summary

The error Cannot read properties of undefined (reading 'getRequests') occurs when a ChatResponseModel is disposed (nullifying its _session back-reference) while the chatEditingModifiedDocumentEntry autorun still holds a reference to it. When the autorun fires (triggered by a transaction in acceptAgentEdits), it accesses res.session.getRequests() on the disposed response model where session is now undefined. This affects agent edit streaming scenarios where the chat session is torn down while edits are still in-flight.

Culprit Commit

Field	Value
Commit	7c7259ff
Author	@roblourens
PR	#308638
Message	pref: Break references at disposal to limit the impact of leaks
Why	This commit introduced this._session = undefined! in ChatResponseModel.dispose() to break retention cycles for GC. However, the observable autorun in chatEditingModifiedDocumentEntry.ts and _createUndoRedoElement both access res.session.getRequests() without null-guarding session, which was never undefined before this change.

Code Flow

sequenceDiagram
    participant Agent as Agent Edit Stream
    participant Session as ChatEditingSession
    participant Entry as ModifiedDocumentEntry
    participant Response as ChatResponseModel
    participant ChatModel as ChatModel

    Agent->>Session: _acceptEdits(resource, edits, isLastEdits)
    Session->>Entry: acceptAgentEdits()
    Entry->>Entry: transaction: _waitsForLastEdits.set(true)
    Note over ChatModel: ⚠️ Session disposed concurrently
    ChatModel->>Response: dispose()
    Note over Response: _session = undefined!
    Entry->>Entry: autorun fires (transaction commit)
    Entry->>Response: _lastModifyingResponseObs.read(r)
    Response-->>Entry: res (disposed, session=undefined)
    Entry->>Response: res.session.getRequests()
    Note over Entry: 💥 Cannot read properties<br/>of undefined (reading 'getRequests')

Loading

Affected Files

File	Role
src/vs/workbench/contrib/chat/common/model/chatModel.ts	Root cause — ChatResponseModel.dispose() nullifies _session
src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:176	Crash site — autorun reads res.session.getRequests() without null guard
src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts:236	Secondary crash site — _createUndoRedoElement also reads response.session.getRequests() unguarded (related bucket 5e789596)
src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedFileEntry.ts	Owns _lastModifyingResponseObs observable that retains the stale response reference
src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingSession.ts	Calls acceptAgentEdits which triggers the transaction/autorun

Repro Steps

1. Open VS Code Insiders (1.116.0+, commit e4f6e114 or later)
2. Start a chat editing session with an agent (Copilot) that produces file edits
3. While the agent is actively streaming edits to a file, close the chat panel or dispose the chat session (e.g., by starting a new session, navigating away)
4. The race between the session disposal (nullifying _session) and the edit acceptance transaction committing (triggering the autorun) produces the error
5. The error is non-deterministic — it depends on the timing of session disposal relative to edit streaming

Fix Proposal

Fix location: src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingModifiedDocumentEntry.ts → autorun at line 172 and _createUndoRedoElement at line 236

Approach: Add optional chaining when accessing session on the response model, since it can now be undefined after disposal:

• Line 176: Change res.session.getRequests() → res.session?.getRequests() (with appropriate fallback when session is undefined — skip the resourceFilter installation)
• Line 236: Change response.session.getRequests() → response.session?.getRequests() (use the fallback label when request can't be found)

Additionally, consider checking this._isDisposed or the response model's disposed state in the autorun before accessing the session, to avoid any other potential null reference issues from the dispose-time cleanup.

Recommended Owner

@roblourens — culprit commit author (PR #308638) who introduced the _session = undefined! disposal pattern. The followup PR #308653 also by Rob extended the same pattern, confirming familiarity with this area.

Generated by errors-investigate · ● 3.2M · ◷

[roblourens]

Already fixed in #309093