Problem

When a Signal envelope contains both sourceNumber and sourceUuid (which is the common case for registered Signal users), resolveSignalSender always returns a sender with kind: "phone" because it prioritizes sourceNumber. The sourceUuid is discarded entirely.

This means that any allowlist entry using the uuid: prefix format (e.g. "uuid:cb274c30-17ce-49ee-97c6-55dd9ce14595") will never match a phone-kind sender, because isSignalSenderAllowed performs strict kind-matching: a uuid entry only matches a uuid sender, and a phone entry only matches a phone sender.

Impact: All DM messages from users whose allowlist entries use uuid: format are silently dropped — no error, no log, no pairing prompt. The user simply never receives a response.

Root Cause

1. resolveSignalSender (line 35): returns { kind: "phone" } whenever sourceNumber is present, throwing away sourceUuid.

2. isSignalSenderAllowed (line 112): only compares entry.kind === "uuid" && sender.kind === "uuid", so a uuid: allowlist entry can never match a kind: "phone" sender.

Fix

Three targeted changes in src/signal/identity.ts:

1. SignalSender type: add optional uuid?: string field to the phone variant, so both identifiers can coexist.

2. resolveSignalSender: when sourceNumber is present, also preserve sourceUuid on the returned phone sender.

3. isSignalSenderAllowed: when a uuid allowlist entry is checked against a phone sender, also compare against sender.uuid (cross-kind matching).

Testing

• Added src/signal/identity.test.ts with 10 tests covering:
  • resolveSignalSender preserves UUID alongside phone number
  • resolveSignalSender falls back to UUID-only when no phone
  • isSignalSenderAllowed phone-to-phone matching (unchanged)
  • isSignalSenderAllowed uuid-to-uuid matching (unchanged)
  • isSignalSenderAllowed uuid entry vs phone sender with uuid (the fix)
  • isSignalSenderAllowed uuid entry vs phone sender without uuid (rejects correctly)
  • Wildcard and empty allowlist edge cases
• All 47 existing Signal tests pass with no regressions.

Made with Cursor

Greptile Overview

Greptile Summary

• Preserve sourceUuid alongside sourceNumber by extending the phone variant of SignalSender with an optional uuid field.
• Update resolveSignalSender to include uuid on phone senders when present, instead of discarding it.
• Update isSignalSenderAllowed to allow uuid: allowlist entries to match phone senders that carry a UUID (cross-kind match).
• Add a new identity.test.ts suite covering sender resolution and allowlist matching, including the cross-kind UUID case.

Confidence Score: 4/5

• Safe to merge after fixing a failing unit test expectation.
• The production change is small and directly addresses the reported mismatch by preserving UUIDs and allowing cross-kind UUID matching. The only concrete issue found is in the new test suite: it expects a uuid: undefined key that the implementation does not emit, which should cause that test to fail. After correcting the test, the change set looks consistent and low-risk.
• src/signal/identity.test.ts

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