[Error] [UriError]: cannot call joinPath on URI without path — sessionsConfigurationService

[vs-code-engineering]

Error Message

[UriError]: cannot call joinPath on URI without path

Stack Trace

    at a.joinPath (./src/vs/base/common/uri.ts:362:9)
    at ele.joinPath (./src/vs/base/common/resources.ts:186:13)
    at joinPath (./src/vs/sessions/contrib/chat/browser/sessionsConfigurationService.ts:378:19)
    at h9.getSessionTasks (./src/vs/sessions/contrib/chat/browser/sessionsConfigurationService.ts:152:8)
    at gb._computeFn (./src/vs/sessions/contrib/chat/browser/runScriptAction.ts:148:0)
    at gb._recompute (./src/vs/base/common/observableInternal/observables/derivedImpl.ts:201:23)
    at gb.get (./src/vs/base/common/observableInternal/observables/derivedImpl.ts:159:10)
    at gb.reportChanges (./src/vs/base/common/observableInternal/observables/baseObservable.ts:45:7)
    at Rvt.endUpdate (./src/vs/base/common/observableInternal/utils/utils.ts:191:15)
    at gb.endUpdate (./src/vs/base/common/observableInternal/observables/derivedImpl.ts:281:6)
    at fO.finish (./src/vs/base/common/observableInternal/transaction.ts:102:12)
    at RP.set (./src/vs/base/common/observableInternal/observables/observableValue.ts:77:8)
    at c$.update (./src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts:391:0)
    at pGe._refreshSessionCache (./src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts:1800:0)
    at cye.value (./src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts:1083:0)
    at E._deliver (./src/vs/base/common/event.ts:1354:12)
    at E._deliverQueue (./src/vs/base/common/event.ts:1365:8)
    at E.fire (./src/vs/base/common/event.ts:1389:8)
    at UA.doResolveProvider (./src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts:637:0)
    at async (./src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsModel.ts:558:0)

Raw Stack Trace (minified)

Error: [UriError]: cannot call joinPath on URI without path     at a.joinPath (out/vs/sessions/sessions.desktop.main.js:406:59221)     at ele.joinPath (out/vs/sessions/sessions.desktop.main.js:406:68517)     at h9._ensureFileWatch (out/vs/sessions/sessions.desktop.main.js:4144:87835)     at h9.getSessionTasks (out/vs/sessions/sessions.desktop.main.js:4144:84430)     at gb._computeFn (out/vs/sessions/sessions.desktop.main.js:4144:95547)     at gb._recompute (out/vs/sessions/sessions.desktop.main.js:407:12496)     at gb.get (out/vs/sessions/sessions.desktop.main.js:407:11830)     at gb.reportChanges (out/vs/sessions/sessions.desktop.main.js:407:497)     at Rvt.endUpdate (out/vs/sessions/sessions.desktop.main.js:407:21647)     at gb.endUpdate (out/vs/sessions/sessions.desktop.main.js:407:13497)     at fO.finish (out/vs/sessions/sessions.desktop.main.js:406:109976)     at RP.set (out/vs/sessions/sessions.desktop.main.js:407:2882)     at c$.update (out/vs/sessions/sessions.desktop.main.js:4144:130869)     at pGe._refreshSessionCache (out/vs/sessions/sessions.desktop.main.js:4144:152750)     at cye.value (out/vs/sessions/sessions.desktop.main.js:4144:141152)     at E._deliver (out/vs/sessions/sessions.desktop.main.js:405:3066)     at E._deliverQueue (out/vs/sessions/sessions.desktop.main.js:405:3155)     at E.fire (out/vs/sessions/sessions.desktop.main.js:405:3490)     at UA.doResolveProvider (out/vs/sessions/sessions.desktop.main.js:1035:424)     at async out/vs/sessions/sessions.desktop.main.js:1034:2807

Details

Property	Value
Bucket ID	6f7febc2-6ca6-5e2d-fd77-572baad778ba
Version	1.115.0-insider
Commit	41dd792b
Last Seen	Fri Apr 10 2026 21:24:39 GMT+0000 (Coordinated Universal Time)
Platforms	Mac, Windows, Linux
Product	Agents

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This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

🔍 Error Investigation

Summary

getSessionTasks in sessionsConfigurationService.ts calls _ensureFileWatch(folder) with a URI that has no path component. This happens when a session's repository has no metadata, causing _buildWorkspace in copilotChatSessionsProvider.ts to fall back to URI.parse('unknown:') — a URI with scheme unknown and an empty path. The joinPath call inside _ensureFileWatch then throws because it cannot join paths on a URI without a path. The error affects 101+ users across all platforms.

Culprit Commit

No single regression commit was identified. This is a latent interaction bug between two code paths:

1. _buildWorkspace() in copilotChatSessionsProvider.ts (line 978) uses URI.parse('unknown:') as a fallback when a session has no repository metadata — creating a URI with no path.
2. getSessionTasks() in sessionsConfigurationService.ts (line 148–153) checks if (folder) but a pathless URI object is truthy, so it passes through to _ensureFileWatch which calls joinPath and crashes.

The _ensureFileWatch and getSessionTasks code was introduced by @benibenj in PRs #297027 / #297371 (Feb 2026). The URI.parse('unknown:') fallback was introduced later. The error first appeared in telemetry on April 7 with commit d09c516f (1 hit) and grew to 147 hits / 101 users by 41dd792b.

Code Flow

sequenceDiagram
    participant Provider as copilotChatSessionsProvider
    participant Model as agentSessionsModel
    participant RunScript as runScriptAction
    participant Config as sessionsConfigurationService
    participant URI as URI.joinPath

    Provider->>Model: _refreshSessionCache → fire onDidChangeSessions
    Model->>RunScript: observable recompute (_computeFn)
    RunScript->>Config: getSessionTasks(activeSession)
    Note over Config: _getSessionRepo(session)<br/>→ repo.uri = URI.parse('unknown:')
    Config->>Config: folder = repo.workingDirectory ?? repo.uri
    Note over Config: ⚠️ Root cause:<br/>folder is truthy but has no path<br/>(if (folder) passes)
    Config->>Config: _ensureFileWatch(folder)
    Config->>URI: joinPath(folder, '.vscode', 'tasks.json')
    Note over URI: 💥 Error thrown:<br/>[UriError]: cannot call joinPath<br/>on URI without path

Loading

Affected Files

File	Role
src/vs/sessions/contrib/chat/browser/sessionsConfigurationService.ts	Crash site — _ensureFileWatch (L378) calls joinPath on pathless URI
src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts	Root cause producer — _buildWorkspace (L978) creates URI.parse('unknown:') fallback
src/vs/sessions/contrib/chat/browser/runScriptAction.ts	Data flow — observable chain triggers getSessionTasks
src/vs/base/common/uri.ts	Guard — joinPath correctly validates URI has a path

Repro Steps

1. Open VS Code Insiders (Agents product)
2. Create or open a session that has no repository metadata (e.g., a session where _extractRepositoryFromMetadata returns all undefined values — this can happen with sessions that haven't fully resolved or have incomplete metadata)
3. The observable chain from runScriptAction.ts triggers getSessionTasks on the active session
4. _buildWorkspace returns a workspace with uri: URI.parse('unknown:') (no path)
5. getSessionTasks passes this URI to _ensureFileWatch, which crashes on joinPath

This is non-deterministic in the sense that it depends on session metadata availability. It triggers most often when sessions are being resolved or refreshed with incomplete data.

Fix Proposal

Two complementary fixes are recommended:

Fix 1 (primary) — src/vs/sessions/contrib/chat/browser/sessionsConfigurationService.ts → getSessionTasks()
Approach: Add a path check before calling _ensureFileWatch. Change the guard from if (folder) to if (folder?.path) to ensure the URI actually has a path before attempting to join paths on it. This mirrors the defensive pattern already used in _getTasksJsonUri (line 360) which also calls joinPath but only after confirming folder is defined.

Fix 2 (defensive) — src/vs/sessions/contrib/copilotChatSessions/browser/copilotChatSessionsProvider.ts → _buildWorkspace()
Approach: When repoUri is undefined, either return undefined from _buildWorkspace instead of creating a workspace with a fake unknown: URI, or give the fallback URI a path (e.g., URI.parse('unknown:/')) so downstream consumers don't crash. The current URI.parse('unknown:') creates a URI that is technically invalid for any file-system-like operations.

Recommended Owner

@benibenj — author of sessionsConfigurationService.ts (getSessionTasks, _ensureFileWatch) where the primary fix should go (PRs #297027, #297371, #302478)

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