Notify MCP clients about shell location changes - #223
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Mike Krüger (mkrueger) wants to merge 2 commits into
Open
Mike Krüger (mkrueger) wants to merge 2 commits into
Mike Krüger (mkrueger) wants to merge 2 commits into
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Expose the shared shell navigation state as the MCP resource cosmos://shell/current-location and support resources/subscribe for it. Subscribed clients receive notifications/resources/updated whenever the location or connection changes, including interactive cd, connect, and disconnect, and can re-read the resource for the new value. - Raise ShellInterpreter.LocationChanged only when the location or the underlying CosmosClient actually changes. - Coalesce pending notifications through a single-slot channel. - Reject subscriptions to other URIs with an InvalidParams protocol error. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Mike Krüger (mkrueger)
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a balanced review from Copilot
September 29, 2026 08:37
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Copilot review overview
🟡 Changes recommended
The reconnect and ARM-reattachment change-detection branch lacks regression coverage.
Review effort: Balanced
Findings: 1
What changed in this PR
Adds a subscribable MCP resource that reports shared shell location changes.
Changes:
- Exposes
cosmos://shell/current-location. - Tracks subscriptions and publishes coalesced update notifications.
- Adds documentation and MCP integration tests.
| File | Description |
|---|---|
README.md |
Links to location subscription documentation. |
docs/mcp.md |
Documents resource and subscription behavior. |
ToolOperations.cs |
Handles subscribe and unsubscribe requests. |
ServerInstructions.md |
Informs clients about the resource. |
ResourceOperations.cs |
Implements the location resource. |
McpServer.cs |
Registers subscriptions and advertises capability. |
LocationResourceSubscriptions.cs |
Tracks clients and sends notifications. |
ShellInterpreter.cs |
Emits location and connection change events. |
ToolOperationsCallToolTests.cs |
Updates test construction and cleanup. |
ShellLocationChangedTests.cs |
Tests basic location-change detection. |
ResourceOperationsTests.cs |
Tests resource JSON content. |
McpLocationSubscriptionTests.cs |
Tests end-to-end subscriptions. |
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- Dispose the port-probe TcpListener in the subscription test. - Limit the per-subscriber catch to the running state via an exception filter so a failed notification only drops that subscriber. - Cover client-identity change detection: a new client at the same location notifies; a changed ARM context with the same client does not. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
MCP clients had no way to learn that the shared shell location changed between tool calls (for example when the user runs
cdinteractively). The location was only visible in thecurrentLocationfield of the next tool response.This PR exposes the navigation state as a subscribable MCP resource:
cosmos://shell/current-locationreturning{ "currentLocation": ... }(nullwhen disconnected,/,/db, or/db/container).resources.subscribeand handlesresources/subscribe/resources/unsubscribefor that URI.notifications/resources/updatedwhenever the location or connection changes, including interactivecd,connect, anddisconnect. Clients re-read the resource for the new value.Implementation notes
ShellInterpreter.LocationChangedfires from theStatesetter only when the location string or the underlyingCosmosClientchanges.cd's double assignment and ARM-context reattachment do not produce duplicate events. The handler only writes to a channel, so it never blocks under the execution lock.LocationResourceSubscriptions(hosted service) tracks subscribed sessions via weak references and drops sessions whose notification fails.DropWrite), since the notification carries only the URI. Scripts with manycdcalls do not flood clients.InvalidParamsMcpProtocolExceptionwith a readable message, not a generic internal error.resources/subscribe). The 2026-07-28subscriptions/listenflow is out of scope until the SDK supports it.Docs
docs/mcp.md: new "Shell Location Updates" section.README.mdandServerInstructions.md: short pointers.Testing
McpLocationSubscriptionTests): a real MCP HTTP client subscribes, receives the notification after a state change, and reads the updated value. It also checks that an invalid subscription URI yieldsInvalidParams.ResourceOperationsTests) and change detection (ShellLocationChangedTests).