Codex cannot resume paginated subagent thread: ordinal 7675 exists but final durable ordinal is 7674

Bug report: paginated subagent resume rejects existing trailing token_count ordinal

Observed failure

An existing local thread cannot resume. Logs from 2026-09-10 show:

2026-09-10T11:48:06.418Z error [electron-message-handler]
method=thread/resume
error code=-32603
error resuming thread: Fatal error: Failed to initialize session: thread-store internal error: failed to resume local thread recorder: paginated subagent rollout at <LOCAL_SESSION_PATH> is incomplete: expected inherited prefix through ordinal 7675, found final durable ordinal 7674

The same error is recorded at 2026-09-10T12:55:15.808Z. Local username and full filesystem path have been removed from this excerpt. No conversation content or CV data is included.

Read-only validation

• File size: 79,513,143 bytes.
• 7,676 JSONL lines; every line parses successfully.
• Top-level ordinals are exactly 0 through 7675, with no gaps or duplicates.
• The file ends with a newline; no truncated final record.
• Original and backup hashes match before and after inspection.
• SHA-256: fa7e30832a88be5f1a1e3859ba572ac480382a3eb35e21dfba6ea150522b3080
• Session metadata: cli_version=0.146.0-alpha.9.2 (recorded creator version, not verified current runtime version), thread_source=subagent, history_mode=paginated, subagent_history_start_ordinal=7676.

Tail structure

[
  {"ordinal":7673,"type":"response_item","payload_type":"custom_tool_call"},
  {"ordinal":7674,"type":"response_item","payload_type":"custom_tool_call_output"},
  {"ordinal":7675,"type":"event_msg","payload_type":"token_count"}
]

This is a structural summary, not fabricated replacement records. The actual ordinal 7675 has a complete token_count payload and no explicit durable:false or non-durable flag.

Expected versus actual

Expected: resuming should consistently validate the inherited boundary when the complete final inherited record is present on disk.
Actual: the loader requires prefix through 7675 but reports final durable ordinal 7674.

Hypothesis, not source-code-confirmed: token_count is excluded from the durable tail calculation while subagent_history_start_ordinal includes it, causing a boundary mismatch. Please investigate the paginated subagent rollout reader and provide a supported recovery path preserving conversation history.

No source files, backup files, ordinals or session metadata were modified. No attempt was made to invent a missing record or bypass the validator.

Locate the paginated subagent rollout reader and the durable-tail calculation, then inspect how the subagent_history_start_ordinal boundary handles the final token_count record. Reproduce the resume failure with the described local thread structure and verify a supported recovery path that preserves the conversation history and accepts a complete inherited boundary.