fix(copilot): default SIM_AGENT_API_URL to www.copilot.sim.ai

[waleedlatif1]

Summary

• Change SIM_AGENT_API_URL_DEFAULT from https://copilot.sim.ai to https://www.copilot.sim.ai to avoid the LB redirect that drops the request path (e.g. /api/copilot)
• Resolves the workaround in #3891 where users had to manually set SIM_AGENT_API_URL

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)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 21, 2026 5:44pm

[cursor]

PR Summary

Low Risk
Low risk: changes only the default Copilot backend base URL; behavior is unchanged when SIM_AGENT_API_URL is explicitly configured, but could affect environments relying on the old default host.

Overview
Updates the Copilot agent default base URL (SIM_AGENT_API_URL_DEFAULT) from https://copilot.sim.ai to https://www.copilot.sim.ai, so requests to agent endpoints (e.g., /api/...) avoid redirects that can drop the path when no env override is set.

^{Reviewed by Cursor Bugbot for commit 4391bfb. Configure here.}

[greptile-apps]

Greptile Summary

This PR changes the default copilot backend URL (SIM_AGENT_API_URL_DEFAULT) from https://copilot.sim.ai to https://www.copilot.sim.ai so that requests to /api/copilot are no longer silently dropped by a load-balancer redirect on the bare domain.

• Changes one constant in apps/sim/lib/copilot/constants.ts; all other copilot logic is unaffected.
• The existing env-override path (SIM_AGENT_API_URL) continues to work normally, so self-hosted deployments with a custom URL are not impacted.

Confidence Score: 5/5

This is a safe, one-line string change to a well-guarded constant; the env-override fallback is untouched and the www. prefix is the correct canonical hostname per the PR description.

The only changed line is the default URL value. All env-override and validation logic in the same file is unmodified, and the fix directly addresses a documented LB redirect issue by targeting the canonical www. subdomain.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/copilot/constants.ts	Single-line URL change updating SIM_AGENT_API_URL_DEFAULT from https://copilot.sim.ai to https://www.copilot.sim.ai to prevent LB redirect that drops the /api/copilot path.

Sequence Diagram

sequenceDiagram
    participant Client
    participant Next.js as Next.js (sim)
    participant LB as Load Balancer
    participant Backend as Copilot Backend

    Note over Client,Backend: Before fix (bare domain)
    Client->>Next.js: POST /api/copilot
    Next.js->>LB: POST https://copilot.sim.ai/api/copilot
    LB-->>Next.js: 301 Redirect → https://www.copilot.sim.ai (path dropped)
    Next.js-->>Client: Request fails / path lost

    Note over Client,Backend: After fix (www subdomain)
    Client->>Next.js: POST /api/copilot
    Next.js->>LB: POST https://www.copilot.sim.ai/api/copilot
    LB->>Backend: POST /api/copilot (path preserved)
    Backend-->>Client: 200 OK

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