Fulfillments in TS SDK are not Partial

[tomkis]

Pre-requisities

• I am using the newest version of the platform (agentstack version shows that CLI and platform are the same version, and there is no newer version available)

Describe the bug
The SDK crashes when oauthRedirectUri is not provided in fulfillments, even though fulfillments are designed to be partial. The Fulfillments interface requires oauthRedirectUri as a mandatory property, and it's called unconditionally in handle-agent-card.ts, causing a runtime error when the function is missing. The fullfilments should always be partial.

To Reproduce
Steps to reproduce the behavior:

1. Create fulfillments without providing oauthRedirectUri
2. Pass the partial fulfillments to resolveMetadata in handle-agent-card.ts
3. The code crashes when calling fulfillments.oauthRedirectUri() on line 99

Expected behavior
Since fulfillments are partial, oauthRedirectUri should be optional. The code should check if oauthRedirectUri exists before calling it, or the interface should make it optional.

Logs / Screenshots / Code snippets
Location: apps/agentstack-sdk-ts/src/client/a2a/extensions/handle-agent-card.ts

// Line 35: oauthRedirectUri is required in the interface
oauthRedirectUri: () => string | null;

// Line 99: Called unconditionally without checking if it exists
const oauthRedirectUri = fulfillments.oauthRedirectUri();

Set-up:

• Model provider: N/A (SDK issue)

Additional context
The crash occurs because the Fulfillments interface defines oauthRedirectUri as a required property, but when fulfillments are partial (as they should be), this property may not be present, leading to a runtime error.

[dosubot]

You're right—oauthRedirectUri is currently required in the Fulfillments interface and is called unconditionally in handle-agent-card.ts, which causes a runtime error if it's missing. The interface is defined in apps/agentstack-sdk-ts/src/client/core/extensions/types.ts and all properties, including oauthRedirectUri, are required methods. The latest code and recent PRs do not make this property optional or the interface partial, so the SDK does not currently support partial fulfillments as intended citation.

To avoid runtime errors, you can either:

• Update the interface to make oauthRedirectUri optional:

  oauthRedirectUri?: () => string | null;

• Or, if you can't change the interface, add a runtime check before calling it:

  const oauthRedirectUri = fulfillments.oauthRedirectUri?.();
  if (oauthRedirectUri) {
    // use oauthRedirectUri
  }

Either approach will prevent crashes when oauthRedirectUri is omitted. Making the interface partial (e.g., Partial<Fulfillments>) is another option if you want all fulfillments to be optional, but you’ll need to add existence checks wherever they're used.

This pattern will help avoid similar issues with other fulfillment properties that may not always be present.

To reply, just mention @dosu.

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