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

[vs-code-engineering]

Error Message

Cannot read properties of undefined (reading 'toString')

Stack Trace

    at (anonymous) (./src/vs/sessions/contrib/codeReview/browser/codeReviewService.ts:66:34)
    at oae (./src/vs/sessions/contrib/codeReview/browser/codeReviewService.ts:66:3)
    at getCodeReviewVersion (./src/vs/sessions/contrib/codeReview/browser/codeReview.contributions.ts:150:0)
    at OV._run (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:110:10)
    at OV.endUpdate (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:167:11)
    at _O.finish (./src/vs/base/common/observableInternal/transaction.ts:102:12)
    at VP.set (./src/vs/base/common/observableInternal/observables/observableValue.ts:77:8)
    at dht.setActiveSession (./src/vs/sessions/services/sessions/browser/sessionsManagementService.ts:354:23)
    at dht.openSession (./src/vs/sessions/services/sessions/browser/sessionsManagementService.ts:237:7)
    at Object.onSessionOpen (./src/vs/sessions/contrib/sessions/browser/views/sessionsView.ts:229:0)
    at yye.value (./src/vs/sessions/contrib/sessions/browser/views/sessionsList.ts:796:0)
    at E._deliver (./src/vs/base/common/event.ts:1354:12)
    at E.fire (./src/vs/base/common/event.ts:1385:8)
    at dui._open (./src/vs/platform/list/browser/listService.ts:763:0)
    at dui.onPointer (./src/vs/platform/list/browser/listService.ts:734:0)
    at yye.value (./src/vs/platform/list/browser/listService.ts:690:0)
    at E._deliver (./src/vs/base/common/event.ts:1354:12)
    at E.fire (./src/vs/base/common/event.ts:1385:8)
    at yye.value (./src/vs/base/common/event.ts:143:83)
    at E._deliver (./src/vs/base/common/event.ts:1354:12)

Raw Stack Trace (minified)

TypeError: Cannot read properties of undefined (reading 'toString')     at out/vs/sessions/sessions.desktop.main.js:4135:50063     at Array.map (<anonymous>)     at oae (out/vs/sessions/sessions.desktop.main.js:4135:50040)     at OV._runFn (out/vs/sessions/sessions.desktop.main.js:4147:44671)     at OV._run (out/vs/sessions/sessions.desktop.main.js:407:6694)     at OV.endUpdate (out/vs/sessions/sessions.desktop.main.js:407:7325)     at _O.finish (out/vs/sessions/sessions.desktop.main.js:406:109976)     at VP.set (out/vs/sessions/sessions.desktop.main.js:407:2882)     at dht.setActiveSession (out/vs/sessions/sessions.desktop.main.js:4147:73731)     at dht.openSession (out/vs/sessions/sessions.desktop.main.js:4147:71261)     at Object.onSessionOpen (out/vs/sessions/sessions.desktop.main.js:4129:22755)     at yye.value (out/vs/sessions/sessions.desktop.main.js:4129:4975)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3385)     at dui._open (out/vs/sessions/sessions.desktop.main.js:861:61260)     at dui.onPointer (out/vs/sessions/sessions.desktop.main.js:861:60943)     at yye.value (out/vs/sessions/sessions.desktop.main.js:861:60075)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3385)     at yye.value (out/vs/sessions/sessions.desktop.main.js:403:11566)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3385)     at Udi.onViewPointer (out/vs/sessions/sessions.desktop.main.js:685:48200)     at Udi.onViewPointer (out/vs/sessions/sessions.desktop.main.js:860:47487)     at yye.value (out/vs/sessions/sessions.desktop.main.js:403:11923)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3385)     at yye.value (out/vs/sessions/sessions.desktop.main.js:403:11566)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3385)     at HTMLDivElement.o (out/vs/sessions/sessions.desktop.main.js:483:63361)

Details

Property	Value
Bucket ID	75c4c8b5-9361-7286-930e-ddf8a1fc29a9
Version	1.116.0-insider
Commit	47add6df
Last Seen	Fri Apr 10 2026 23:25:22 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
• Last release without this error: 1.116.0-insider (0271b4d2)
• First release with this error: 1.116.0-insider (1ec46de1)
• Commit range: 0271b4d2...1ec46de1

Related Error Buckets

These additional error buckets are tracked by this issue (v1.116.0-insider):

Bucket ID	Error Message	Users
75c4c8b5	Cannot read properties of undefined (reading 'toString')	6
f6615ef4	Cannot read properties of undefined (reading 'toString')	6

Analysis

The error occurs in the Agents code review service when getCodeReviewVersion tries to call toString on an undefined value. The deminified stack shows:

at (anonymous) (codeReviewService.ts:66:34)
at (anonymous) (codeReviewService.ts:66:3)
at getCodeReviewVersion (codeReview.contributions.ts:150:0)
at (anonymous) (autorunImpl.ts:110:10)
at (anonymous) (lazyObservableValue.ts:21:9)
at (anonymous) (autorunImpl.ts:103:11)

This is an Agents-specific regression in the code review feature, likely caused by a nullable value in the code review service not being guarded before calling toString().

Generated by errors-agents-regression-scan · ◷

[vs-code-engineering]

🔍 Error Investigation

Summary

The error Cannot read properties of undefined (reading 'toString') occurs when opening a session in the Agents app that contains file changes where modifiedUri is undefined (e.g., deleted files represented as IChatSessionFileChange2). The getCodeReviewVersion() function calls file.currentUri.toString() but currentUri can be undefined when the v2 type guard (isIChatSessionFileChange2) fails — most notably after session cache deserialization strips the uri field.

Culprit Commit

No single commit in the regression range (0271b4d2...1ec46de1) directly modifies the crash-site files. This is a latent bug in the v1/v2 file-change handling code that was exposed by a data-flow change in the range — likely a commit in extensions/copilot/ that changed how session file changes are produced, causing IChatSessionFileChange2 objects (with optional modifiedUri) to appear where only v1 objects were seen before.

Most likely triggers from the range:

• c7fd9716 (@DonJayamanne) — refactored clearWorkspaceChanges handling
• f6d4cad1 (@lszomoru) — changed git add -A → git add for GVFS compatibility

Code Flow

sequenceDiagram
    participant User as User clicks session
    participant SessMgmt as sessionsManagementService
    participant Autorun as codeReview.contributions autorun
    participant Extract as getCodeReviewFilesFromSessionChanges
    participant Version as getCodeReviewVersion

    User->>SessMgmt: openSession() → setActiveSession()
    SessMgmt->>Autorun: activeSession observable triggers
    Autorun->>Autorun: reads activeSession.changes
    Autorun->>Extract: getCodeReviewFilesFromSessionChanges(changes)
    Note over Extract: isIChatSessionFileChange2 returns false<br/>(uri field missing after deserialization)<br/>⚠️ Falls to v1 path: currentUri = change.modifiedUri
    Note over Extract: modifiedUri is undefined (deleted file)<br/>→ currentUri = undefined
    Extract->>Version: getCodeReviewVersion(files)
    Note over Version: 💥 file.currentUri.toString()<br/>Cannot read properties of undefined

Loading

Affected Files

File	Role
src/vs/sessions/contrib/codeReview/browser/codeReviewService.ts:66	Crash site — getCodeReviewVersion() calls file.currentUri.toString() without null guard
src/vs/sessions/contrib/codeReview/browser/codeReviewService.ts:48-61	Root cause — getCodeReviewFilesFromSessionChanges() v1 path uses change.modifiedUri directly without fallback
src/vs/sessions/contrib/codeReview/browser/codeReview.contributions.ts:149-150	Trigger — autorun reads changes and calls both functions
src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts:882-887	Contributing — cache deserialization only handles v1, strips uri field from v2 changes
src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts:958-959	Contributing — _extractChanges() unsafely casts any changes array to IChatSessionFileChange[]
src/vs/workbench/contrib/chat/common/chatSessionsService.ts:471-474	Type guard — isIChatSessionFileChange2 requires uri instanceof URI, fails on deserialized data

Repro Steps

1. Open the VS Code Agents app (Insiders 1.116.0+)
2. Create a session that produces file changes including a deleted file (so modifiedUri is undefined in the v2 change object)
3. Close and reopen the app (session gets cached and deserialized)
4. Click on the session in the sessions list to open it
5. The code review autorun triggers → getCodeReviewVersion() crashes

The error may also occur without cache if the session provider produces v2 changes where uri is not a proper URI instance.

Fix Proposal

Fix location: src/vs/sessions/contrib/codeReview/browser/codeReviewService.ts → getCodeReviewFilesFromSessionChanges()

Approach: Add a guard in the v1 fallback path to handle modifiedUri being undefined. The simplest fix mirrors the v2 path's fallback pattern:

// In getCodeReviewFilesFromSessionChanges, the else branch (v1 path) should guard:
// Before: currentUri: change.modifiedUri,
// After:  currentUri: change.modifiedUri ?? (change as any).uri,
// Or filter out entries with undefined currentUri

Secondary fix (recommended): Update AgentSessionsCache.loadCachedSessions() in agentSessionsModel.ts:882-887 to properly handle IChatSessionFileChange2 during deserialization — preserve the uri field and use isIChatSessionFileChange2 to apply the correct revive logic.

Tertiary fix: Update _extractChanges() in copilotChatSessionsProvider.ts:958-959 to avoid the unsafe cast — use isIChatSessionFileChange2 to properly distinguish v1 and v2 changes.

Recommended Owner

@bryanchen-d — already assigned to this issue. @benvillalobos is the chat-review area owner and may want to review the fix given it touches the code review service.

Generated by errors-investigate · ● 25.9M · ◷