[Error] unhandlederror-Cannot read properties of undefined (reading 'fsPath')

[vs-code-engineering]

Error Message

unhandlederror-Cannot read properties of undefined (reading 'fsPath')

Stack Trace

    at NNi (./src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorUtils.ts:56:27)
    at changeMatchesResource (./src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorUtils.ts:36:29)
    at p2 (./src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorUtils.ts:36:14)
    at getSessionForResource (./src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorOverlay.ts:192:0)

Raw Stack Trace (minified)

TypeError: Cannot read properties of undefined (reading 'fsPath')     at NNi (out/vs/sessions/sessions.desktop.main.js:3841:16935)     at out/vs/sessions/sessions.desktop.main.js:3841:16770     at Array.some (<anonymous>)     at p2 (out/vs/sessions/sessions.desktop.main.js:3841:16762)     at jF._runFn (out/vs/sessions/sessions.desktop.main.js:4573:10229)     at jF._run (out/vs/sessions/sessions.desktop.main.js:407:6694)     at jF.endUpdate (out/vs/sessions/sessions.desktop.main.js:407:7325)     at JM.finish (out/vs/sessions/sessions.desktop.main.js:406:109995)     at Ci (out/vs/sessions/sessions.desktop.main.js:406:109195)     at F3t.handleEvent (out/vs/sessions/sessions.desktop.main.js:407:24129)     at Ige.value (out/vs/sessions/sessions.desktop.main.js:403:11922)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3268)     at E._deliverQueue (out/vs/sessions/sessions.desktop.main.js:405:3357)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3692)     at out/vs/sessions/sessions.desktop.main.js:1890:31500

Details

Property	Value
Bucket ID	3e9b327e-f811-d15c-88a1-7186fb5a47b4
Version	1.118.0-insider
Commit	102df5b5
Last Seen	Wed Apr 22 2026 18:03:21 GMT+0000 (Coordinated Universal Time)
Platforms	Mac, Windows
Product	Agents

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This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

No fix proposed — the crash site (change.modifiedUri.fsPath on the non-v2 branch of changeMatchesResource, line 56 at commit 102df5b5) has already been refactored on main to the null-safe isEqual(...) form, so the offending .fsPath-of-undefined read no longer exists in current source.

Summary

TypeError: Cannot read properties of undefined (reading 'fsPath') is thrown from changeMatchesResource in src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorUtils.ts. At the shipped commit 102df5b5, the function was:

export function changeMatchesResource(change: ISessionFileChange, resourceUri: URI): boolean {
	if (isIChatSessionFileChange2(change)) {
		return change.uri.fsPath === resourceUri.fsPath
			|| change.modifiedUri?.fsPath === resourceUri.fsPath
			|| change.originalUri?.fsPath === resourceUri.fsPath;
	}

	return change.modifiedUri.fsPath === resourceUri.fsPath   // <-- line 56, no optional chaining
		|| change.originalUri?.fsPath === resourceUri.fsPath;
}

The non-IChatSessionFileChange2 branch dereferences change.modifiedUri.fsPath without optional chaining. When a ISessionFileChange has an undefined modifiedUri (e.g. a pure-addition/deletion change, or a provider-supplied change that only sets originalUri), change.modifiedUri is undefined and reading .fsPath throws. Note the sibling accesses on the same lines (change.modifiedUri?.fsPath in the v2 branch, change.originalUri?.fsPath in both branches) already used ?. — only this one dereference was left unguarded, which is the classic single-site null-safety miss.

This is a type-contract TypeError: ISessionFileChange.modifiedUri is effectively optional at runtime, but the crash-site code treated it as always-present.

Culprit Commit

8d0b49d0cf8f1b17e14da9011e86a456559a3007 — "Agents - fix resource comparison for agent feedback (#312737)" by @lszomoru (2026-04-27). This commit introduced the change.modifiedUri.fsPath === resourceUri.fsPath comparison style; the non-v2 branch was written without the optional chaining that the adjacent accesses received.

Code Flow

flowchart TD
    A[Editor active-editor / model change signal] --> B[AgentFeedbackOverlayController autorun]
    B --> C[getActiveResourceCandidates - resourceUri]
    C --> D[getSessionForResource]
    D --> E["session.changes.get().some(change => changeMatchesResource(change, resourceUri))"]
    E --> F["changeMatchesResource: non-v2 branch"]
    F --> G["change.modifiedUri.fsPath  ← modifiedUri is undefined"]
    G --> H["TypeError: Cannot read properties of undefined (reading 'fsPath')"]

Loading

Affected Files

• src/vs/sessions/contrib/agentFeedback/browser/agentFeedbackEditorUtils.ts — changeMatchesResource (crash site, line 56 at commit 102df5b5).
• Callers via .some(change => changeMatchesResource(...)) in agentFeedbackService.ts and getSessionForResource (overlay autorun) — these iterate all session changes, so any single change with an undefined modifiedUri triggers the throw.

Repro Steps

1. Open the Agents window with an active agent session whose changes include an entry that has no modifiedUri (a deletion, or a provider change that only carries originalUri).
2. Make that file's editor the active editor so the agent-feedback overlay autorun evaluates getSessionForResource over the session changes.
3. changeMatchesResource hits the non-v2 branch and dereferences change.modifiedUri.fsPath on the undefined modifiedUri, throwing the reported TypeError.

Open Questions

The bug is already fixed on main. The current source of changeMatchesResource no longer contains the unguarded .fsPath dereference — it was refactored to the fully null-safe isEqual helper, which short-circuits on undefined operands (resources.ts isEqual: if (!uri1 || !uri2) { return false; }):

export function changeMatchesResource(change: ISessionFileChange, resourceUri: URI): boolean {
	if (isIChatSessionFileChange2(change)) {
		return isEqual(change.uri, resourceUri)
			|| isEqual(change.modifiedUri, resourceUri)
			|| isEqual(change.originalUri, resourceUri);
	}

	return isEqual(change.modifiedUri, resourceUri)
		|| isEqual(change.originalUri, resourceUri);
}

Because isEqual(undefined, resourceUri) returns false instead of throwing, an undefined modifiedUri (or resourceUri) can no longer produce this TypeError. This is the correct upstream-safe form — it neither swallows an error in a try/catch nor guards at an unrelated site.

Remaining question for the owner: confirm the isEqual refactor is the intended permanent fix (it is a stricter, correct comparison) and that the telemetry bucket stops accruing hits on builds after that refactor landed. If the bucket continues on newer commits, re-open with a fresh commit hash, since that would indicate a second, distinct undefined-URI producer feeding these comparisons. No code change is proposed here because there is nothing left to change at the crash site on current main.

Recommended Owner

@lszomoru — authored the culprit commit 8d0b49d0 (#312737) that introduced the resource-comparison logic in agentFeedbackEditorUtils.ts. @benibenj is a strong secondary owner as the primary author of the agent-feedback feature area.

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