improvement(ui): delegate streaming animation to Streamdown component

[emir-karabeg]

Summary

• Removed custom useStreamingText hook and useThrottledValue indirection from chat and Mothership message rendering
• Delegated streaming animation entirely to Streamdown's built-in mode, isStreaming, and animated props
• Eliminated 100 lines of manual character-by-character reveal logic (setInterval, easing, chase factor)

Type of Change

• Bug fix

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Apr 14, 2026 10:21pm

[cursor]

PR Summary

Medium Risk
Moderate UI behavior change: removes custom throttling/stream-reveal logic and relies on Streamdown’s streaming mode, which could subtly affect perceived streaming smoothness and special-tag rendering during SSE updates.

Overview
Delegates message streaming animation to Streamdown by removing the custom useStreamingText progressive-reveal hook and the chat-level useThrottledValue wrapper, rendering message content directly.

Simplifies markdown rendering by making the markdown components static (COMPONENTS) and dropping support for injecting a custom link component. Streaming-related CSS animations on some special-tag UI blocks were also removed.

^{Reviewed by Cursor Bugbot for commit be9e2d3. Configure here.}

[greptile-apps]

Greptile Summary

This PR removes the custom useStreamingText hook and throttle indirection, replacing character-by-character animation with Streamdown's built-in rendering (ultimately using mode='static' throughout). It also bundles several unrelated simplifications in use-chat.ts: removing the skipped/rejected tool-call statuses, stripping subagent scope tracking via subagentByParentToolCallId, and removing path normalization in extractResourceFromReadResult.

• skipped and rejected tool outcomes now silently map to error: the server-side generated contract (MothershipStreamV1ToolOutcome) still declares both values, so if the server emits them, affected tools will incorrectly render as errors instead of their true state.

Confidence Score: 4/5

Safe to merge for the animation/UI changes; the bundled use-chat.ts logic simplifications need a verification pass before shipping.

The streaming animation refactor is clean and well-executed. The concern is the unrelated logic changes bundled in use-chat.ts: the skipped/rejected → error mapping is a confirmed behavior change against a still-valid server contract, warranting a check that those outcomes are truly deprecated before this reaches production.

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts — specifically the tool-outcome status resolution (lines ~1800-1820) and the unconditional activeSubagent clear on span end.

Important Files Changed

Filename	Overview
apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts	Bundles several logic changes beyond animation: removes skipped/rejected status handling (maps both to error), removes subagentByParentToolCallId scope tracking, simplifies extractResourceFromReadResult (drops path trimming/filtering), and unconditionally clears activeSubagent on span end.
apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/chat-content/chat-content.tsx	Correctly removes the useStreamingText/smoothStreaming indirection; now passes raw content directly to Streamdown with mode='static'. Clean and consistent.
apps/sim/app/chat/components/message/components/markdown-renderer.tsx	COMPONENTS extracted to module-level constant (avoids recreation on each render), customLinkComponent prop removed (no external callers found), LinkWithPreview de-exported. Clean refactor.
apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx	Removes skipped/rejected cases from mapToolStatusToClientState; both now fall through to the 'executing' default since the status is resolved as 'error' upstream in use-chat.ts. Also removes smoothStreaming prop passthrough.
apps/sim/hooks/use-streaming-text.ts	File deleted. The setInterval-based character-by-character reveal logic is no longer needed after animation is delegated to Streamdown.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Tool result event received] --> B{isCancelled?}
    B -- yes --> C[tc.status = 'cancelled']
    B -- no --> D["success = payload.success ?? (status === 'success')"]
    D --> E{success?}
    E -- true --> F[tc.status = 'success']
    E -- false --> G[tc.status = 'error']

    subgraph REMOVED["Removed handling"]
        H["status='skipped' → ToolCallStatus.skipped"]
        I["status='rejected' → ToolCallStatus.rejected"]
    end

    style REMOVED fill:#fee2e2,stroke:#f87171
    style G fill:#fca5a5,stroke:#dc2626

    J["Server can still send 'skipped'/'rejected'\n(MothershipStreamV1ToolOutcome)"] -.->|maps to| G

Loading

Comments Outside Diff (1)

1. apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts, line 1800-1820 (link)

   skipped and rejected outcomes silently become error

   MothershipStreamV1ToolOutcome in the generated contract still declares both 'skipped' and 'rejected' as valid server values. With the new status resolution:

   const success = payload.success ?? payload.status === MothershipStreamV1ToolOutcome.success
   // for status='skipped': undefined ?? false  → false  → tc.status = 'error'
   // for status='rejected': undefined ?? false → false  → tc.status = 'error'

   Both outcomes map to 'error', so a tool the server marks as skipped or rejected will render in the UI as a failure. The removed resolveLiveToolStatus distinguished these cases, and generic-resource-content.tsx previously rendered "Skipped"/"Rejected" labels for them. If the server still emits these outcomes, users will see incorrect error states.

_{Reviews (3): Last reviewed commit: "improvement(ui): remove hardcoded fade-i..." | Re-trigger Greptile}

[emir-karabeg]

@greptile

[emir-karabeg]

@greptile

[emir-karabeg]

@cursor review

[emir-karabeg]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit be9e2d3. Configure here.}