[saravanan619]

Summary

Fixes #5418.

prepareUserOperation chose between the per-operation
paymasterContext and the bundler client's default with a truthiness
test, but the option is typed unknown, so false, 0, and '' are
legitimate values. Any of them was treated as "not provided": with a
client default, the default was silently passed to
getPaymasterStubData/getPaymasterData instead of the explicit
override; without one, the explicit value was erased to undefined.
A caller therefore could not opt a single operation out of a
bundler-level default sponsorship context (e.g. with
paymasterContext: false), and a paymaster callback that distinguishes
"no context" from "explicitly false/empty" could never see the
distinction.

Changes

• src/account-abstraction/actions/bundler/prepareUserOperation.ts:
  select on presence (!== undefined) instead of truthiness, so the
  client default applies only when the per-operation option is absent.
  null is still forwarded verbatim, matching the declared unknown
  type; only undefined means "not supplied".
• src/account-abstraction/actions/bundler/prepareUserOperation.paymasterContext.test.ts:
  new offline regression tests that run prepareUserOperation with
  parameters: ['paymaster'] against a real local HTTP paymaster
  server whose returned paymasterData encodes the context it
  received, asserting on the prepared User Operation output: false,
  0, and '' overrides are forwarded instead of the client default,
  a truthy object override still wins, undefined still falls back to
  the client default, and a falsy override is preserved when no client
  default exists.
• .changeset/paymaster-context-presence.md: patch changeset.

Verification

• New suite: 6 passed on the fix. Red-then-green: reverting the
  one-line fix makes the 4 falsy-override cases fail (the 2
  fallback/truthy controls still pass), re-applying it makes all 6
  pass.
• tsc -b src passes; the new test file typechecks clean; Biome
  check passes on both changed source files.
• Not run: the existing anvil-based prepareUserOperation.test.ts
  suite (it needs an anvil + alto bundler harness, unavailable in this
  environment). The change is a single presence-vs-truthiness selection
  with no effect on truthy/undefined inputs, which the existing
  args: paymasterContext and behavior: bundlerClient.paymasterContext
  tests already cover.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9758ed1

The changes in this PR will be included in the next version bump.

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[jxom]

Thanks for the fix! I'm closing this in favour of #5431. It keeps your source change unchanged, credits you as co-author, and moves the regression test into the existing prepareUserOperation.test.ts to follow the repo's test conventions. It also extends the changeset to cover null.

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