Assertion failed: has_refs()

### How frequently does the bug occur? Always ### Description We're encountering a **crash in Realm Core** with the following message: `Assertion failed: has_refs()` and this `terminating due to uncaught exception of type realm::util::DecryptionFailed: Decryption failed: page 98 in file of size 3198976 failed the HMAC check. Either the encryption key is incorrect or data is corrupted` This occurs when **two processes simultaneously access the same encrypted Realm file** - one writing, the other reading. Based on our investigation, this seems to be a **race condition** that happens during concurrent encrypted access across processes. ### Reproduction We've created a minimal example with two apps that reproduce the issue: - **TestApp1** (the *listener*): opens the encrypted Realm and continuously reads from it. - **TestApp2** (the *writer*): opens the same Realm file and performs repeated writes. #### Steps to Reproduce: 0. Clone this: https://github.com/c128128/RealmBug 1. Start **TestApp1** (the listener). 2. Then launch **TestApp2** (the writer). 3. Within a few moments, **TestApp1 crashes** with: ``` Assertion failed: m_has_refs with (m_ref, ndx, m_size) = [5232, 0, 0] ``` or sometimes with: ``` terminating due to uncaught exception of type realm::util::DecryptionFailed: Decryption failed: page 98 in file of size 3198976 failed the HMAC check. Either the encryption key is incorrect or data is corrupted ``` ### Environment - **RealmSwift version**: 10.54.5 - **RealmCore version**: 14.14.0 - **Platform**: Mac Catalyst - **Encryption**: Enabled (64-byte key) - **Concurrency**: Two processes accessing the same Realm file simultaneously ### Key Observations - The crash **does not occur** with an **unencrypted Realm**. - The crash seems to occur during memory mapping or decryption, possibly due to **unsynchronized access to shared encrypted pages**. - Appears to be an issue within Realm Core's internal caching or reference tracking. - The bug was **introduced after `realm-swift` 10.51.0** - everything works fine on 10.51.0, but crashes consistently starting with **10.52.0** and later versions. ### Can you reproduce the bug? Always ### Version 10.54.5 ### What Atlas Services are you using? Local Database only ### Are you using encryption? Yes ### Platform OS and version(s) macOS 15.5 (Apple M1 Max) related https://github.com/realm/realm-core/issues/8081