Best possible solution:

Land only after maintainer approval and redacted real channel proof, preferably Telegram, showing one Codex preamble line updating in place and not becoming the final answer.

Do we have a high-confidence way to reproduce the issue?

Do we have a high-confidence way to reproduce the issue? No live high-confidence reproduction is present; source inspection shows current main lacks the projector and keyed draft behavior, and the PR adds focused tests for that path.

Is this the best way to solve the issue?

Is this the best way to solve the issue? Yes in direction: carrying Codex item phases and stable item IDs through the shared progress draft contract is the narrow maintainable shape, but visible channel proof and maintainer approval are still required.

Acceptance criteria:

• Review redacted Telegram proof showing the preamble update sequence and final answer exclusion.
• If promoted for landing, run focused Codex projector, Plugin SDK channel-streaming, and touched channel dispatch tests through the repo-approved test path.

What I checked:

• Current main lacks commentary progress streaming: On current main, handleAssistantDelta stores agent-message deltas internally and does not emit commentary-phase item progress, while final assistant selection has no phase filter in this projector path. (extensions/codex/src/app-server/event-projector.ts:385, 697103604367)
• PR adds Codex commentary progress projection: The PR head records assistant item phases, emits commentary items as preamble progress events, and skips commentary items when resolving final assistant text. (extensions/codex/src/app-server/event-projector.ts:400, 7598d0dc835f)
• PR adds stable progress-line identity in the SDK: The shared progress draft contract gains itemId/id plus normalizeChannelProgressDraftLineIdentity and mergeChannelProgressDraftLine, allowing keyed progress updates to replace an existing line instead of stacking partial prefixes. (src/plugin-sdk/channel-streaming.ts:811, 7598d0dc835f)
• Telegram visible path is wired through item IDs: The PR head passes payload.itemId into Telegram item progress draft lines and merges those keyed lines before updating the preview stream. (extensions/telegram/src/bot-message-dispatch.ts:1498, 7598d0dc835f)
• Focused tests cover the intended projector and merge behavior: The PR adds tests that commentary agent messages emit keyed preamble events, do not call partial reply streaming, do not become final answers, and keyed progress lines update in place. (extensions/codex/src/app-server/event-projector.test.ts:679, 7598d0dc835f)
• Maintainer note requires real Telegram proof: The Telegram maintainer note says Telegram behavior PRs touching streaming need real Telegram proof, preferably the bot-to-bot QA lane or equivalent live probe. (.agents/maintainer-notes/telegram.md:35, 697103604367)

Likely related people:

• @steipete: Recent commit history for src/plugin-sdk/channel-streaming.ts shows multiple progress draft fixes and API surface maintenance in the shared SDK path. (role: progress-draft feature owner and recent SDK contributor; confidence: high; commits: f3f1509ee9cc, 0a92d7a8ff4d, accf774591cf; files: src/plugin-sdk/channel-streaming.ts)
• @vincentkoc: Recent GitHub history for extensions/telegram/src/bot-message-dispatch.ts shows Telegram progress-draft work in the affected dispatch path. (role: recent Telegram streaming contributor; confidence: high; commits: b5c337909713; files: extensions/telegram/src/bot-message-dispatch.ts)
• @pashpashpash: Although also the PR author, this person appears in prior merged history for the Codex app-server event-projector path touched by this PR. (role: recent Codex app-server contributor; confidence: medium; commits: 78eb92e62277; files: extensions/codex/src/app-server/event-projector.ts)
• @obviyus: Recent commit history for the Codex app-server projector includes native tool and diagnostics refactors in the same area. (role: adjacent Codex projector contributor; confidence: medium; commits: 529bfdbaca40, 13b364912a5a; files: extensions/codex/src/app-server/event-projector.ts)

Remaining risk / open question:

• No redacted live channel sequence has been supplied or run in this read-only review, so Telegram update-in-place behavior and final-answer exclusion remain unverified in a real setup.

Codex review notes: model gpt-5.5, reasoning high; reviewed against 697103604367.