feat(tui): remove Zellij TUI workarounds

[fcoury-oai]

Why

We added Zellij-specific TUI workarounds because older Zellij behavior did not work with Codex's normal terminal model:

• fix: add tui.alternate_screen config and --no-alt-screen CLI flag for Zellij scrollback #8555 made tui.alternate_screen = "auto" disable alternate screen in Zellij so transcript history stayed available.
• fix(tui): handle zellij redraw and composer rendering #16578 avoided scroll-region operations in Zellij by emitting raw newlines and using a separate composer styling path.

This PR removes both workarounds because the latest Zellij release tested locally (zellij 0.44.1) works correctly with Codex's standard TUI behavior: normal alternate-screen handling, redraw, and history insertion.

What Changed

• Removed the InsertHistoryMode::Zellij path and the Zellij-only newline scrollback insertion behavior.
• Removed cached is_zellij state from the TUI and composer.
• Removed Zellij-specific composer styling, the helper snapshot, and the TerminalInfo::is_zellij() convenience method that only served this workaround.
• Changed tui.alternate_screen = "auto" to use alternate screen for Zellij too; --no-alt-screen and tui.alternate_screen = "never" still preserve the inline mode escape hatch.
• Updated the generated config schema description for tui.alternate_screen.

How to Test

Manual smoke path used with zellij 0.44.1:

1. Build and run this branch inside a Zellij 0.44.1 session with default config.
2. Start Codex normally and produce enough assistant/tool output to create scrollback.
3. Confirm the transcript remains readable, the composer renders normally, and scrolling through terminal history works.
4. Resize the Zellij pane while output exists and confirm the TUI redraws without duplicated, missing, or stale rows.
5. Compare with --no-alt-screen or -c tui.alternate_screen=never if you want to verify the inline fallback still works.

Targeted tests:

• just write-config-schema
• just fmt
• just fix -p codex-tui
• cargo test -p codex-terminal-detection
• cargo test -p codex-tui alternate_screen_auto_uses_alt_screen

Attempted but did not complete locally:

• cargo test -p codex-tui built and ran the new test successfully, then failed later on unrelated local failures in status_permissions_full_disk_managed_* and a stack overflow in tests::fork_last_filters_latest_session_by_cwd_unless_show_all.

Documentation

No developers.openai.com Codex documentation update is needed for this revert.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

💡 Codex Review

codex/codex-rs/terminal-detection/src/lib.rs

Line 170 in ce30099

)

Preserve the public Zellij detection helper

Removing this public method is a breaking API change for users of codex-terminal-detection: existing callers that rely on TerminalInfo::is_zellij() now fail to compile even though the underlying multiplexer data still exists. If the workaround is gone, keeping this helper as a stable convenience avoids breaking downstream code.

---

codex/codex-rs/terminal-detection/src/lib.rs

Line 173 in ce30099

/// Formats the terminal info as a User-Agent token.

Preserve the public Zellij detection helper

Removing this public method is a breaking API change for users of codex-terminal-detection: existing callers that rely on TerminalInfo::is_zellij() now fail to compile even though the underlying multiplexer data still exists. If the workaround is gone, keeping this helper as a stable convenience avoids breaking downstream code.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[etraut-openai]

Looks good from a config standpoint. Doesn't change any config logic; just updates some description strings.