- Track normalized ID state (`occupied`/`preserved`) during preprocessing to avoid remapping valid existing IDs.
- Resolve collisions by appending deterministic hash-based suffixes until a free ID is found.
- Share occupancy tracking across shortening and remapping so sanitized IDs remain stable and idempotent.
Closes: #4891
Reuse immutable request bytes during input inspection and avoid a redundant websocket clone while preserving the required outbound envelope.
Constraint: Preserve request immutability and one final WebSocket request-body allocation
Rejected: In-place JSON mutation | request buffers are shared across translation and execution stages
Confidence: high
Scope-risk: narrow
Directive: Do not retain no-copy gjson results or mutate their backing payload while results are in use
Tested: GOTOOLCHAIN=local go test ./...; targeted 8 MiB allocation benchmarks
Not-tested: Live Codex upstream network traffic
- Prefix non-compliant message input IDs with `msg_` while leaving valid/prefixed IDs unchanged.
- Apply normalization before length checks and shortening to keep ID handling deterministic and consistent across Codex request paths.
- Updated `SanitizeCodexInputItemIDs` to remove encrypted reasoning items with IDs exceeding the Codex length limit.
- Refactored logic to deterministically shorten other overlong input item IDs, ensuring compliance with the Codex format.
- Added new tests to verify dropping behavior for encrypted reasoning and shortening of lengthy IDs without encrypted content.
- Implemented deterministic shortening of overlong Codex input item IDs to meet 64-character limit.
- Added `SanitizeCodexInputItemIDs` helper for efficient ID shortening in request bodies.
- Updated Codex executor and websocket implementations to utilize the new helper.
- Introduced unit tests to validate ID length restrictions, avoidance of collisions, and deterministic behavior.
Closes: #4401
