feat: support MCP progress notification #11510

changkun · 2026-01-25T11:56:55Z

Summary

This PR adds real-time progress tracking for MCP tool calls, allowing users to see progress updates while long-running tools execute.

Data Flow:

  MCP Server -> MCPConnection -> MCPManager -> SSE Events -> useSSE -> ToolCall Component                                                                                                                                                                                                                            
       ↓              ↓              ↓            ↓           ↓           ↓                                                                                                                                                                                                                                     
    Progress    Token-based     Progress      progress   Progress    Progress                                                                                                                                                                                                                                   
  Notifications  Validation     Callback      event      Map/Atom    Bar UI

Change Type

Please delete any irrelevant options.

New feature (non-breaking change which adds functionality)

Testing

This test communicates with a MCP server and invokes tool progress which sends progress notification, below is a sample implementation:

	mcp.AddTool(s, &mcp.Tool{
		Name:        "progress",
		Description: "The tool to track the progress of the current task.",
	}, func(ctx context.Context, req *mcp.CallToolRequest, in any) (*mcp.CallToolResult, any, error) {

		for i := 0; i < 100; i++ {
			time.Sleep(100 * time.Millisecond)
			progress := float64(i) / 100

			_ = req.Session.NotifyProgress(ctx, &mcp.ProgressNotificationParams{
				ProgressToken: req.Params.GetProgressToken(),
				Progress:      progress,
				Total:         100,
				Message:       fmt.Sprintf("Progress: %d%%", i),
			}) // Ignore error for non-critical notifications
		}

		b, err := json.Marshal(struct {
			Progress float64 `json:"progress"`
			Total    float64 `json:"total"`
			Message  string  `json:"message"`
		}{
			Progress: 100,
			Total:    100,
			Message:  "Task completed",
		})
		if err != nil {
			return nil, nil, fmt.Errorf("unable to marshal JSON: %w", err)
		}
		return &mcp.CallToolResult{Content: []mcp.Content{&mcp.TextContent{Text: string(b)}},}, nil, nil
}

Screen.Recording.2026-01-25.at.10.39.01.mov

Test Configuration:

Checklist

My code adheres to this project's style guidelines
I have performed a self-review of my own code
I have commented in any complex areas of my code

Fixes danny-avila#8221

danny-avila · 2026-01-26T15:09:27Z

@changkun thanks for the PR!

Changed base branch to dev-staging since this is reserved for changes post-v0.8.2-release.

Looks like some tests are failing and there are merge conflicts. Also started a copilot review and would be great if you can address any comments if it returns any (I'll also check validity of those AI comments).

Copilot

Pull request overview

Adds end-to-end support for MCP progress notifications so the UI can show live progress updates during long-running MCP tool calls (Fixes #8221).

Changes:

Introduces progress-token generation/tracking in MCPConnection and passes the token via tools/call _meta.
Forwards MCP progress notifications from the API to the client over SSE as a new progress event.
Stores progress per toolCallId on the client and surfaces progress text in the ToolCall UI.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
packages/api/src/utils/events.ts	Adds safer SSE response writes and introduces `sendProgress` SSE event.
packages/api/src/mcp/types/index.ts	Adds shared progress-related types (`ProgressToken`, state interfaces).
packages/api/src/mcp/connection.ts	Subscribes to MCP progress notifications, throttles, tracks token state, emits `progress` events.
packages/api/src/mcp/MCPManager.ts	Generates/registers progress tokens, forwards progress events via `onProgress`, cleans up listeners/tokens.
client/src/store/progress.ts	Adds Jotai state for mapping `toolCallId -> progress`.
client/src/hooks/SSE/useSSE.ts	Listens for `progress` SSE events and updates the progress map.
client/src/components/Chat/Messages/Content/ToolCall.tsx	Displays MCP progress message/values in ToolCall “in-progress” text.
client/src/components/Chat/Messages/Content/Part.tsx	Passes `toolCallId` down to ToolCall for correct progress correlation.
api/server/services/MCP.js	Forwards MCP progress updates from `MCPManager` to the browser via SSE.

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Copilot · 2026-01-26T15:10:14Z

packages/api/src/mcp/connection.ts

+          try {
+            logger.info(`${this.getLogPrefix()} Received progress notification:`, notification.params);
+            const { progressToken, progress, total, message } = notification.params;


Progress notifications can arrive many times per second; logging every notification at info will spam logs and increase CPU/IO. Consider downgrading this to debug (or sampling), especially since you already throttle emission separately.

Copilot · 2026-01-26T15:10:15Z

packages/api/src/mcp/MCPManager.ts

+          logger.info(`${logPrefix}[${toolName}] Progress event received:`, {
+            progressToken: data.progressToken,
+            progress: data.progress,
+            total: data.total,
+            message: data.message,


Logging every progress update at info will flood logs for long-running tools (potentially multiple times per second). Consider switching this per-update log to debug (or removing it) and keeping info for coarse lifecycle events only.

Copilot · 2026-01-26T15:10:15Z

packages/api/src/mcp/connection.ts

+  private subscribeToProgress(): void {
+    try {
+      this.client.setNotificationHandler(
+        ProgressNotificationSchema,
+        async (notification) => {


Progress token tracking/throttling is new behavior but there are no tests covering it (token registration, unknown-token filtering, monotonic validation, throttling, cleanup). There is already an MCP test suite under src/mcp/__tests__; consider adding coverage for these cases to prevent regressions.

Copilot · 2026-01-26T15:10:15Z

client/src/hooks/SSE/useSSE.ts

+    sse.addEventListener('progress', (e: MessageEvent) => {
+      try {
+        const data = JSON.parse(e.data);
+        const { progress, total, message, toolCallId } = data;
+


Progress events are only processed in this non-resumable SSE hook. When resumable streams are enabled, this hook is inactive (submission is null), so MCP progress won’t be displayed. Progress needs to be propagated/handled in the resumable stream path as well.

Copilot · 2026-01-26T15:10:16Z

api/server/services/MCP.js

+          // Forward progress events to client via SSE, including tool call ID for matching
+          logger.debug(`[MCP][${serverName}][${toolName}] Sending progress to client:`, progressData);
+          sendProgress(res, {
+            ...progressData,
+            toolCallId: toolCall.id, // Include tool call ID so frontend can match progress to specific tool call
+          });


onProgress always forwards via sendProgress(res, ...), but in resumable mode (streamId set) the active SSE connection is /chat/stream/:streamId and this response may not be the streaming one. Progress updates will be dropped unless they’re routed through the resumable stream transport (e.g., GenerationJobManager.emitChunk(streamId, ...)).

Suggested change

// Forward progress events to client via SSE, including tool call ID for matching

logger.debug(`[MCP][${serverName}][${toolName}] Sending progress to client:`, progressData);

sendProgress(res, {

...progressData,

toolCallId: toolCall.id, // Include tool call ID so frontend can match progress to specific tool call

});

// Forward progress events to client, including tool call ID for matching

logger.debug(`[MCP][${serverName}][${toolName}] Sending progress to client:`, progressData);

const payload = {

...progressData,

toolCallId: toolCall.id, // Include tool call ID so frontend can match progress to specific tool call

};

if (streamId) {

// In resumable mode, route progress through the resumable stream transport

GenerationJobManager.emitChunk(streamId, payload);

return;

}

// In non-resumable mode, send progress directly via SSE on this response

sendProgress(res, payload);

Copilot · 2026-01-26T15:10:16Z

api/server/services/MCP.js

+          logger.debug(`[MCP][${serverName}][${toolName}] Sending progress to client:`, progressData);
+          sendProgress(res, {
+            ...progressData,


This forwards progressToken to the browser (...progressData). The token is generated using userId/serverName in MCPConnection.generateProgressToken(), so this can expose internal user identifiers unnecessarily. Since the UI matches progress using toolCallId, consider omitting progressToken from the SSE payload (and/or stop embedding userId in the token).

Suggested change

logger.debug(`[MCP][${serverName}][${toolName}] Sending progress to client:`, progressData);

sendProgress(res, {

...progressData,

// Strip progressToken to avoid exposing internal identifiers derived from userId/serverName.

const { progressToken, ...safeProgressData } = progressData || {};

logger.debug(

`[MCP][${serverName}][${toolName}] Sending progress to client:`,

safeProgressData,

);

sendProgress(res, {

...safeProgressData,

Copilot · 2026-01-26T15:10:16Z

packages/api/src/mcp/MCPManager.ts

+      progressToken = connection.generateProgressToken();
+      connection.registerProgressToken(progressToken);
+      logger.info(`${logPrefix}[${toolName}] Progress token generated and registered: ${progressToken}`);


Progress token generation is logged at info. Since progress is expected to be high-frequency, consider downgrading token/progress logs to debug (or sampling) to avoid log spam and excess IO.

Copilot · 2026-01-26T15:10:16Z

client/src/components/Chat/Messages/Content/ToolCall.tsx

+  const progress = useMemo(() => {
+    if (hasOutput) {
+      return 1; // Tool completed
+    }
+    return simulatedProgress;


The progress bar value is always driven by simulatedProgress until output exists, so it won’t reflect real MCP {progress,total} updates. Consider computing the bar value from mcpProgress when total is present (e.g., progress/total, clamped to [0,1]) and falling back to simulated progress otherwise.

Copilot · 2026-01-26T15:10:17Z

packages/api/src/utils/events.ts

+  } catch {
+    // Client may have disconnected - log but don't crash


The comment says “log but don't crash”, but the catch block doesn’t actually log anything. Either add logging here (at an appropriate level to avoid spamming) or adjust the comment to match the behavior.

Suggested change

} catch {

// Client may have disconnected - log but don't crash

} catch (error) {

// Client may have disconnected - log but don't crash

console.warn('safeWrite: failed to write to response; client may have disconnected.', error);

feat: support MCP progress notification

de923e3

Fixes danny-avila#8221

changkun marked this pull request as ready for review January 25, 2026 11:59

danny-avila changed the base branch from dev to dev-staging January 26, 2026 14:59

danny-avila requested a review from Copilot January 26, 2026 15:00

Copilot started reviewing on behalf of danny-avila January 26, 2026 15:00 View session

Copilot AI reviewed Jan 26, 2026

View reviewed changes

danny-avila force-pushed the dev-staging branch from 842ac95 to 6279ea8 Compare January 28, 2026 22:45

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feat: support MCP progress notification #11510

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changkun commented Jan 25, 2026 •

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		// Client may have disconnected - log but don't crash

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changkun commented Jan 25, 2026 •

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