The IPC server normally deletes a command after writing its response. On successful receipt, the client tried deleting that command again and then deleting the response inside one try block. The expected missing-command exception skipped response cleanup, retaining the complete response file after an otherwise successful exchange.

Attempt command and response cleanup independently. Either file may already be absent without preventing cleanup of the other or changing the delivered payload.

Validation:

• Actual client/server round trip deterministically observes the server-deleted command: baseline leaves the response behind; fixed code removes it.
• A second control covers receipt while the command still exists. Both protocol directories end empty and the successful payload is retained.
• Baseline: 1 failure, 1 passing control. Fixed full backend suite: 131 passed.
• git diff --check passes.

AI assistance was used to investigate and prepare this patch. Tests use local threads, production IPC classes, and temporary files. No simulation or model calls are made.