[Error] unhandlederror-Session file is corrupted (line 1452: data.compactionTokensUsed.input: Required)

[vs-code-engineering]

Error Message

unhandlederror-Session file is corrupted (line 1452: data.compactionTokensUsed.input: Required)

Stack Trace

    at hkt.getSession (extensions/copilot/node_modules/@github/copilot/sdk/index.js:4936:13029) [not deminified]
    at process.processTicksAndRejections (node:<REDACTED: user-file-path>:103:5) [not deminified]
    at async DH.getChatHistoryImpl (../src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts:1019:20)
    at async DH.getChatHistory (../src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts:993:22)
    at async Lce.getSessionHistory (../src/extension/chatSessions/vscode-node/copilotCLIChatSessions.ts:625:19)
    at async Lce.provideChatSessionContent (../src/extension/chatSessions/vscode-node/copilotCLIChatSessions.ts:597:43)
    at async Cf.$provideChatSessionContent (./src/vs/workbench/api/common/extHostChatSessions.ts:662:18)

Raw Stack Trace (minified)

Error: Session file is corrupted (line 1452: data.compactionTokensUsed.input: Required) 	at hkt.getSession (extensions/copilot/node_modules/@github/copilot/sdk/index.js:4936:13029) 	at process.processTicksAndRejections (node:<REDACTED: user-file-path>:103:5) 	at async DH.getChatHistoryImpl (\extensions\copilot\dist\extension.js:2398:25672) 	at async DH.getChatHistory (\extensions\copilot\dist\extension.js:2398:25157) 	at async Lce.getSessionHistory (\extensions\copilot\dist\extension.js:2428:11122) 	at async Promise.all (index 0) 	at async Lce.provideChatSessionContent (\extensions\copilot\dist\extension.js:2428:10640) 	at async Cf.$provideChatSessionContent (out/vs/workbench/api/node/extensionHostProcess.js:531:38830)

Details

Property	Value
Bucket ID	4b9cff58-8a48-8b6b-9ca9-a0f5805f242d
Version	1.118.0-insider
Commit	f2b51f3f
Last Seen	Sun Apr 26 2026 23:10:52 GMT+0000 (Coordinated Universal Time)
Platforms	Mac, Windows, Linux
Product	VSCode

---

This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

Regression Details

• Product: VSCode
• Regression type: new
• Last release without this error: 1.117.0 (10c8e557)
• First release with this error: 1.118.0-insider (102df5b5)
• Commit range: 10c8e557...102df5b5

The error originates in the Copilot extension: copilot/sdk/index.js:4936 (getSession) → copilot/dist/extension.js:2398 (getChatHistoryImpl) → copilot/dist/extension.js:2428 (getSessionHistory → provideChatSessionContent). A corrupted session file causes parsing failure. 35 affected users.

Generated by errors-regression-scan · ● 9.6M · ◷

[vs-code-engineering]

🔍 Error Investigation

Summary

The error Session file is corrupted (line 1452: data.compactionTokensUsed.input: Required) occurs when the Copilot SDK 1.0.34 attempts to deserialize session files that were originally created with SDK 1.0.28. The newer SDK version added compactionTokensUsed.input as a required field in the session file schema (Zod validation), but existing session files lack this field, causing a schema validation failure whenever a user reopens a previous chat session. This affects 35 users across all platforms.

Culprit Commit

Field	Value
Commit	4e26289a
Author	@DonJayamanne
PR	#311650
Message	fix: update @github/copilot to version 1.0.34 and integrate AutoModeSessionManager in session services
Why	This commit bumped the @github/copilot SDK from ^1.0.28 to ^1.0.34 in the copilot extension. SDK 1.0.34 introduced a stricter session file schema that requires data.compactionTokensUsed.input, which does not exist in session files created by the older SDK.

Code Flow

sequenceDiagram
    participant VSCode as extHostChatSessions.ts
    participant Provider as copilotCLIChatSessions.ts
    participant Service as copilotcliSessionService.ts
    participant SDK as `@github/copilot` SDK 1.0.34

    VSCode->>Provider: $provideChatSessionContent()
    Provider->>Service: getChatHistory({sessionId})
    Service->>Service: getChatHistoryImpl()
    Service->>SDK: sessionManager.getSession({sessionId})
    Note over SDK: ⚠️ Root cause:<br/>Zod schema requires<br/>compactionTokensUsed.input<br/>but old session files lack it
    SDK-->>Service: 💥 Error: Session file is corrupted<br/>(data.compactionTokensUsed.input: Required)
    Service-->>Provider: error propagates (uncaught)
    Provider-->>VSCode: unhandled rejection

Loading

Affected Files

File	Role
extensions/copilot/node_modules/@github/copilot/sdk/index.js	Crash site — SDK getSession() throws on schema validation
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts	Data flow — getChatHistoryImpl() calls SDK without handling schema migration errors
extensions/copilot/src/extension/chatSessions/vscode-node/copilotCLIChatSessions.ts	Data flow — getSessionHistory() / provideChatSessionContent() propagate the error
src/vs/workbench/api/common/extHostChatSessions.ts	VS Code API layer — $provideChatSessionContent() calls the extension provider
extensions/copilot/package.json	Root cause — SDK version bump from ^1.0.28 to ^1.0.34

Repro Steps

1. Use VS Code Insiders 1.117.x and have one or more existing Copilot chat sessions saved to disk.
2. Update to VS Code Insiders 1.118.0 (which includes SDK 1.0.34).
3. Open a chat session that was created with the previous version.
4. The session fails to load with "Session file is corrupted" because the session file was written by SDK 1.0.28 and is missing the compactionTokensUsed.input field now required by SDK 1.0.34.

Fix Proposal

There are two complementary fixes:

1. SDK-side (primary fix): The @github/copilot SDK should make compactionTokensUsed.input optional in its session file schema (with a sensible default), or implement a migration step that backfills missing fields when loading older session files. This ensures backward compatibility across SDK versions.

Fix location: @github/copilot SDK → session file Zod schema definition
Approach: Change the compactionTokensUsed.input field from .required() to .optional().default(0) (or an appropriate default), or add a schema migration layer.

2. Extension-side (defensive fix): copilotcliSessionService.ts → getChatHistoryImpl() should catch "Session file is corrupted" errors from sessionManager.getSession() and handle them gracefully — either by returning an empty history, deleting/migrating the corrupted file, or showing a user-friendly notification — rather than letting the error propagate as an unhandled exception.

Fix location: extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts → getChatHistoryImpl()
Approach: Wrap the sessionManager.getSession() call in a try/catch that logs the corruption error and returns { history: [], events: [] } so the session list remains functional even when individual files can't be parsed.

Recommended Owner

@DonJayamanne — culprit commit author (PR #311650 updated the Copilot SDK to 1.0.34 and integrated AutoModeSessionManager)

Generated by errors-investigate · ● 5.2M · ◷