Data Connect Emulator v3.0.2 Transaction Mutation Hang

When doing a Data Connect ***transaction mutation*** the request hangs. 

- This happens on `firebase-tools` version [15.3.0](https://github.com/firebase/firebase-tools/releases/tag/v15.3.0)
  - **15.2.0 is stable**. 
- Specifically, I believe it comes from the `Update Data Connect Emulator to 3.0.2` PR (https://github.com/firebase/firebase-tools/pull/9738).
- **Also tested on a NEW flutter and firebase project with the same results.**
- *This also happens on version 15.3.1 but that looks like it was just MCP updates.*





### [REQUIRED] Environment info





**firebase-tools:** 15.3.0, 15.3.1



**Platform:** Windows 11 Pro

**Application SDK**: Flutter

### [REQUIRED] Test case

Tested with a simple transaction mutation.

Schema:
``` graphql
type Test @table(name: "test_tests") {
  id: Int64!
  message: String
}
```

Mutation Transaction:
``` graphql
mutation TransactionTest(
  $id: Int64!
  $message: String!
  $updateMessage: String!
) @transaction @auth(level: PUBLIC) {
  query
    @redact
    @check(
      expr: "response.query.existingTest == null"
      message: "Test record already exists!"
    ) {
    existingTest: test(first: { where: { id: { eq: $id } } }) {
      id
      message
    }
  }

  insert: test_insert(data: { id: $id, message: $message })

  update: test_update(
    first: { where: { id: { eq_expr: "response.insert.id" } } }
    data: { message: $updateMessage }
  )
}
```



### [REQUIRED] Steps to reproduce

1. Install firebase-tools 15.3.0
2. Copy in the simple transaction mutation provided
3. Run `firebase emulators:start --debug`
4. Trigger a Data Connect transaction mutation that writes to the DB
5. Request hangs indefinitely
6. Restart application, emulator crashes

*NOTE: If you downgrade to firebase-tools 15.2.0 it works.*



### [REQUIRED] Expected behavior

Transaction mutation completes and doesn't infinitely hang.



### [REQUIRED] Actual behavior

#### I suspect this excerpt from the full log result below:

```terminal
Error: Unexpected initial message
    at _class5.handleClientMessage (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:212007)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async _class5.processData (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:211063)
    at async _class5.init (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:209869)
!!  dataconnect: Postgres threw an unexpected error, shutting down the Data Connect emulator: AbortError: The operation was aborted {"metadata":{"emulator":{"name":"dataconnect"},"message":"Postgres threw an unexpected error, shutting down the Data Connect emulator: AbortError: The operation was aborted"}}
```

---

#### Log after running the transaction.

``` terminal 
[2026-01-16T19:12:24.688Z] I0116 13:12:24.688136   47764 prepare.go:110] [operation "TransactionTest"] preparePlan succeeded
I0116 13:12:24.688136   47764 prepare.go:101] [operation "TransactionTest"] DBStats beforePrepare: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:0, Idle:1, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}, afterPrepare: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:0, Idle:1, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}
 {"metadata":{"emulator":{"name":"dataconnect"},"message":"I0116 13:12:24.688136   47764 prepare.go:110] [operation \"TransactionTest\"] preparePlan succeeded\nI0116 13:12:24.688136   47764 prepare.go:101] [operation \"TransactionTest\"] DBStats beforePrepare: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:0, Idle:1, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}, afterPrepare: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:0, Idle:1, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}\n"}}
```

#### Same log session, but *after* I reloaded the app because of the hang ~5 minutes later; emulator crashes

``` terminal
runQuery DEALLOCATE ALL [] undefined
[2026-01-16T19:18:08.302Z] Postgres client disconnected
[2026-01-16T19:18:08.302Z] E0116 13:18:08.299339   47764 execute.go:47] Database ping failed: input:
 after 5m43.610117s
stats before: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:1, Idle:0, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}
stats After: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:1, Idle:0, WaitCount:1, WaitDuration:343610117000, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}
E0116 13:18:08.300386   47764 transaction.go:29] failed to rollback transaction: sql: transaction has already been committed or rolled back
W0116 13:18:08.300916   47764 engine.go:182] [/emulator/firebase 3004] ExecuteMutation TransactionTest: failed. Connector: core
Auth: public
Variables Set:
[id message updateMessage]
Errors: [message:"Database is not available\nTest record already exists! (aborted)" path:{values:{string_value:"query"}} extensions:{debug_details:"cannot reach the database: context canceled\n@check(expr) rejected the request: denied due to error: input: \n (aborted)\nCheck Requirement Evaluated: Every(path: query, DenyUnlessTrue(CEL(\"response.query.existingTest == null\" -> Boolean)))"} message:"(aborted)" path:{values:{string_value:"insert"}} message:"(aborted)" path:{values:{string_value:"update"}}]
Data Fields:
[insert update]
sources: core\users\mutations.gql [5025B] core\posts\mutations.gql [2962B] core\interactions\mutations.gql [1283B] core\interactions\queries.gql [1435B] core\comments\fragments.gql [527B] core\users\fragments.gql [228B] core\users\queries.gql [1651B] core\posts\fragments.gql [473B] core\posts\queries.gql [2192B] core\interactions\fragments.gql [201B] core\comments\mutations.gql [2999B] core\comments\queries.gql [1441B] core\test\mutations.gql [865B]
 {"metadata":{"emulator":{"name":"dataconnect"},"message":"E0116 13:18:08.299339   47764 execute.go:47] Database ping failed: input: \n after 5m43.610117s\nstats before: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:1, Idle:0, WaitCount:0, WaitDuration:0, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}\nstats After: sql.DBStats{MaxOpenConnections:1, OpenConnections:1, InUse:1, Idle:0, WaitCount:1, WaitDuration:343610117000, MaxIdleClosed:0, MaxIdleTimeClosed:0, MaxLifetimeClosed:0}\nE0116 13:18:08.300386   47764 transaction.go:29] failed to rollback transaction: sql: transaction has already been committed or rolled back\nW0116 13:18:08.300916   47764 engine.go:182] [/emulator/firebase 3004] ExecuteMutation TransactionTest: failed. Connector: core\nAuth: public\nVariables Set:\n[id message updateMessage]\nErrors: [message:\"Database is not available\\nTest record already exists! (aborted)\" path:{values:{string_value:\"query\"}} extensions:{debug_details:\"cannot reach the database: context canceled\\n@check(expr) rejected the request: denied due to error: input: \\n (aborted)\\nCheck Requirement Evaluated: Every(path: query, DenyUnlessTrue(CEL(\\\"response.query.existingTest == null\\\" -> Boolean)))\"} message:\"(aborted)\" path:{values:{string_value:\"insert\"}} message:\"(aborted)\" path:{values:{string_value:\"update\"}}]\nData Fields:\n[insert update]\nsources: core\\users\\mutations.gql [5025B] core\\posts\\mutations.gql [2962B] core\\interactions\\mutations.gql [1283B] core\\interactions\\queries.gql [1435B] core\\comments\\fragments.gql [527B] core\\users\\fragments.gql [228B] core\\users\\queries.gql [1651B] core\\posts\\fragments.gql [473B] core\\posts\\queries.gql [2192B] core\\interactions\\fragments.gql [201B] core\\comments\\mutations.gql [2999B] core\\comments\\queries.gql [1441B] core\\test\\mutations.gql [865B] \n"}}
Error: Unexpected initial message
    at _class5.handleClientMessage (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:212007)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async _class5.processData (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:211063)
    at async _class5.init (C:\Users\user\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\pg-gateway\dist\chunk-FCOSUQFU.cjs:1:209869)
!!  dataconnect: Postgres threw an unexpected error, shutting down the Data Connect emulator: AbortError: The operation was aborted {"metadata":{"emulator":{"name":"dataconnect"},"message":"Postgres threw an unexpected error, shutting down the Data Connect emulator: AbortError: The operation was aborted"}}
i  emulators: Shutting down emulators. {"metadata":{"emulator":{"name":"hub"},"message":"Shutting down emulators."}}
i  ui: Stopping Emulator UI {"metadata":{"emulator":{"name":"ui"},"message":"Stopping Emulator UI"}}
i  extensions: Stopping Extensions Emulator {"metadata":{"emulator":{"name":"extensions"},"message":"Stopping Extensions Emulator"}}
[2026-01-16T19:18:08.307Z] [Extensions] Stopping Extensions emulator, this is a noop.
i  functions: Stopping Functions Emulator {"metadata":{"emulator":{"name":"functions"},"message":"Stopping Functions Emulator"}}
i  firestore: Stopping Firestore Emulator {"metadata":{"emulator":{"name":"firestore"},"message":"Stopping Firestore Emulator"}}
!  Firestore Emulator has exited upon receiving signal: SIGINT
i  pubsub: Stopping Pub/Sub Emulator {"metadata":{"emulator":{"name":"pubsub"},"message":"Stopping Pub/Sub Emulator"}}
!  Pub/Sub Emulator has exited upon receiving signal: SIGINT
i  auth: Stopping Authentication Emulator {"metadata":{"emulator":{"name":"auth"},"message":"Stopping Authentication Emulator"}}
i  storage: Stopping Storage Emulator {"metadata":{"emulator":{"name":"storage"},"message":"Stopping Storage Emulator"}}
[2026-01-16T19:18:08.330Z] Stopping rules runtime. {"metadata":{"emulator":{"name":"storage"},"message":"Stopping rules runtime."}}
i  eventarc: Stopping Eventarc Emulator {"metadata":{"emulator":{"name":"eventarc"},"message":"Stopping Eventarc Emulator"}}
i  dataconnect: Stopping Data Connect Emulator {"metadata":{"emulator":{"name":"dataconnect"},"message":"Stopping Data Connect Emulator"}}
# 108:fake shutdown
# skipped shmem_exit_index=5/6
# before_shmem_exit_index=4/6
2026-01-16 19:18:08.346 GMT [0] LOG:  shutting down
2026-01-16 19:18:08.347 GMT [0] DEBUG:  performing replication slot checkpoint
# skipped shmem_exit_index=3/6
# skipped shmem_exit_index=2/6
# skipped shmem_exit_index=1/6
# skipped shmem_exit_index=0/6
# dsm_backend_shutdown ?
!  Data Connect Emulator has exited upon receiving signal: SIGINT
i  tasks: Stopping Cloud Tasks Emulator {"metadata":{"emulator":{"name":"tasks"},"message":"Stopping Cloud Tasks Emulator"}}
i  hub: Stopping emulator hub {"metadata":{"emulator":{"name":"hub"},"message":"Stopping emulator hub"}}
i  logging: Stopping Logging Emulator {"metadata":{"emulator":{"name":"logging"},"message":"Stopping Logging Emulator"}}

```

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Data Connect Emulator v3.0.2 Transaction Mutation Hang #9756

[REQUIRED] Environment info

[REQUIRED] Test case

[REQUIRED] Steps to reproduce

[REQUIRED] Expected behavior

[REQUIRED] Actual behavior

I suspect this excerpt from the full log result below:

Log after running the transaction.

Same log session, but after I reloaded the app because of the hang ~5 minutes later; emulator crashes

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Data Connect Emulator v3.0.2 Transaction Mutation Hang #9756

Description

[REQUIRED] Environment info

[REQUIRED] Test case

[REQUIRED] Steps to reproduce

[REQUIRED] Expected behavior

[REQUIRED] Actual behavior

I suspect this excerpt from the full log result below:

Log after running the transaction.

Same log session, but after I reloaded the app because of the hang ~5 minutes later; emulator crashes

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

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