[Error] [GitHub.copilot-chat] unhandlederror-Response stream has been closed

[vs-code-engineering]

Error Message

unhandlederror-Response stream has been closed

Stack Trace

Error: Response stream has been closed 	at t._push (<REDACTED: user-file-path>/.vscode\extensions\github.copilot-chat-0.45.1\dist\extension.js:1726:24933) 	at t.push (<REDACTED: user-file-path>/.vscode\extensions\github.copilot-chat-0.45.1\dist\extension.js:1726:26055) 	at t._push (<REDACTED: user-file-path>/.vscode\extensions\github.copilot-chat-0.45.1\dist\extension.js:1726:24694) 	at t.progress (<REDACTED: user-file-path>/.vscode\extensions\github.copilot-chat-0.45.1\dist\extension.js:1726:25869) 	at <REDACTED: user-file-path>/.vscode\extensions\github.copilot-chat-0.45.1\dist\extension.js:6879:30682

Details

Property	Value
Bucket ID	60c003f2-03fc-c1f8-dd72-d6e6c0660070
Extension Version	0.45.1
Last Seen	Sun Apr 26 2026 23:55:04 GMT+0000 (Coordinated Universal Time)
Platforms	win32, darwin, linux
Product	VSCode

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This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

Stable Release Anomaly Details

• Anomaly type: new (not present in 0.45.0)
• Previous stable: 0.45.0
• Current stable: 0.45.1

Bucket Details (v0.45.1)

Bucket	Users	Error Message
60c003f2	1,918	Response stream has been closed

Deminified callstack (from 60c003f2):

(anonymous) (../src/util/common/chatResponseStreamImpl.ts:56:11)
(anonymous) (../src/util/common/chatResponseStreamImpl.ts:173:7)
(anonymous) (../src/util/common/chatResponseStreamImpl.ts:31:11)
(anonymous) (../src/util/common/chatResponseStreamImpl.ts:154:8)
(anonymous) (../src/extension/inlineChat/node/inlineChatIntent.ts:226:10)

The error occurs in chatResponseStreamImpl.ts when content is pushed to a response stream that has already been closed. The call originates from inlineChatIntent.ts:226, suggesting a race condition where inline chat intent processing continues after the response stream is closed (e.g., user cancellation or timeout).

Generated by errors-stable-scan · ● 10.1M · ◷

[vs-code-engineering]

🔍 Error Investigation

Summary

The GitHub.copilot-chat extension encounters "Response stream has been closed" when it attempts to push data (via progress(), push(), or other stream methods) to a ChatAgentResponseStream that has already been closed. This is a race condition between the extension's asynchronous response generation and the stream lifecycle managed by VS Code's extension host. The error has been present across many extension versions (0.38.x through 0.45.1) with 56,900 total hits affecting 23,368 users, and is flagged as a stable-channel anomaly indicating a recent spike.

Culprit Commit

No commit range was provided in the issue or comments (the issue was just created with no regression scan follow-up yet). The error is a long-standing race condition present across many extension versions — it is not attributable to a single commit. The hit count has been growing steadily:

Extension Version	Hits	Users
0.39.x	~4,500	~2,600
0.42.x	~13,900	~4,900
0.43.0	10,563	4,161
0.44.x	~18,400	~10,100
0.45.1	3,360 (still accumulating)	1,928

Code Flow

sequenceDiagram
    participant Ext as Copilot Chat Extension
    participant API as ChatAgentResponseStream (extHostChatAgents2.ts)
    participant Host as $invokeAgent

    Host->>Ext: agent.invoke(request, context, stream, token)
    Ext->>API: stream.progress(value) / stream.push(part)
    Note over API: ✅ Stream open, data forwarded

    Note over Host: ⚠️ CancellationToken fires<br/>(user stops, navigates away, etc.)
    Host->>Host: raceCancellationWithTimeout(1000ms)
    Note over Host: Wait 1000ms grace period...
    Host->>API: finally { stream.close() }
    Note over API: _isClosed = true

    Ext->>API: stream.progress(value) [async continuation]
    Note over API: 💥 throwIfDone() →<br/>"Response stream has been closed"

Loading

Affected Files

File	Role
src/vs/workbench/api/common/extHostChatAgents2.ts:85	Crash site — throwIfDone() throws "Response stream has been closed"
src/vs/workbench/api/common/extHostChatAgents2.ts:998	Race origin — raceCancellationWithTimeout(1000, ...) races task against cancellation
src/vs/workbench/api/common/extHostChatAgents2.ts:1046	Stream close — finally { stream?.close() } sets _isClosed = true
github.copilot-chat/dist/extension.js	Extension code — async handler continues writing after close

Repro Steps

1. Open VS Code with Copilot Chat extension (any version 0.38+)
2. Start a Copilot Chat conversation that triggers a long streaming response (e.g., complex code generation)
3. Cancel the request while the response is still streaming — either by clicking the stop button, starting a new message, or navigating away from the chat
4. The cancellation token fires, but the extension's async LLM token processing may still have pending microtasks or promises that attempt to call stream.progress() after the 1000ms grace period expires
5. The error is non-deterministic and depends on timing — it's more likely with slower network responses or during tool invocations that produce multiple async progress updates

Fix Proposal

Two complementary approaches, ideally both:

1. VS Code core — graceful close (primary fix)
Fix location: src/vs/workbench/api/common/extHostChatAgents2.ts → throwIfDone()
Approach: Instead of throwing an error when the stream is closed, silently ignore the write (or log a warning). The throwIfDone pattern at line 83-88 throws an Error that gets caught by the extension host error telemetry, generating noise. Since the stream closure is an expected lifecycle event (cancellation), writes after close should be a no-op, not a thrown error. This would eliminate all hits for this bucket without any behavior change — the data would simply be discarded since the response is already being abandoned.

2. Copilot Chat extension — check cancellation before writes
Fix location: github.copilot-chat extension's stream wrapper (the _push/push/progress methods seen in the stack trace)
Approach: Before calling VS Code's stream.progress() or stream.push(), check token.isCancellationRequested and return early. This is a defensive check that prevents the extension from hitting the VS Code error path entirely.

Recommended Owner

@roblourens — owns both the Chat Participant API in VS Code (extHostChatAgents2.ts) and the copilot-chat extension's agentic loop, making them the ideal owner to address both sides of this race condition.

Generated by errors-investigate · ● 8.2M · ◷