plat 553

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PLAT-553 — The chat never showed when a coding CLI compacted its context

Field	Value
State	fixed on main
Priority	P2
Product	chat
Area	reliability
Summary	fixed on main, not deployed: Codex, Claude, Pi, Muse and Agy compaction records become a context_compaction event and one chat row ("Compacting context…" → "Compacted context (1m 39s) · 384k → 92k tokens"); Cursor rec…

Coordination	Value
State	fixed on main (2026-10-06); not deployed
Date	2026-10-06
Owner	chat-reliability

Source

Owner request: show context compaction for every coding CLI in the chat, from structured records only ("show, don't scrape", PLAT-354 list). Before this, nothing in llmtypes, mcpagent or agent_go carried compaction; a long turn just went quiet for minutes.

Done

• Provider (multi-llm-provider-go 6ea681c): new chunk context_compaction with a ContextCompaction payload (phase start/end, id, trigger, outcome, tokens before/after, started/ended, duration). Per CLI:
  • Codex: rollout item_completed ContextCompaction = end with started/completed ms. Tokens before = the last token_count input; tokens after = the zero-input token_count Codex writes right after compacting (seen on real 0.160 rollouts: 235118 → 20754). Tmux tailer and a new rollout side channel for the structured transport (codex exec --json has no compaction item).
  • Claude: stream-json system/status "compacting" (start), compact_boundary.compact_metadata and status null + compact_result (end); transcript compact_boundary.compactMetadata (end, tmux). Shapes from the 2.1.289 bundle and a real 2.1.226 transcript.
  • Pi: --mode json compaction_start / compaction_end; tmux marker extension hooks session_before_compact / session_compact / session_compact_failed (writes reason, tokensBefore, aborted only).
  • Muse: context_compaction_candidate running (start), context_compaction_installed (end, budget before/after = Muse's estimated prompt tokens, summarizer duration). tool_results_cleared is a light prune and is not shown.
  • Agy: finished CHECKPOINT steps (type 23) that are not intent_only (end, start/end from step metadata). Every real conversation has one intent-only checkpoint that only titles the chat; those are skipped.
• mcpagent (5a9ec3e): ContextCompactionEvent (context_compaction), emitted even when generation streaming events are suppressed.
• agent_go: event in schema-gen, the durable chat allowlist and STRUCTURAL_EVENTS (survives reload). Frontend: one quiet row per compaction at the start's position: "Compacting context…" (spinner), then "Compacted context (1m 39s) · 384k → 92k tokens"; unknown parts omitted; a start left open by a finished turn reads "no result recorded".
• Tests: one fixture test per CLI parser from real record shapes (Codex, Claude transcript, Muse, Agy from real files; Pi from Pi's docs/types, no real Pi event stream on this laptop), and a vitest for the row collapse.

Judgment calls

• Consumers pair start/end by compaction_id and keep the newest end, so Claude can emit an end on compact_result and again on the later boundary (order undocumented) without two rows.
• Codex and Agy have no start record, so they show only the finished row.
• The compact chat view (older turns as messages only) drops compaction rows of older turns; the latest turn and the full view keep them.

Left

• Cursor: no structured compaction in stream-json or transcripts, only a preCompact hook (start only, no end). Not shown.
• Retained live-input follow-up turns read progress as messages, not chunks, so a compaction there is not shown (Codex, Claude, Muse, Agy).
• Not seen live: no compaction was triggered during this work (needs a very large context). Parsers are verified on recorded records; the event plumbing is shared with live usage (PLAT-554), which was checked live.

Register notes

PLAT-553, P2, fixed on main, not deployed: Codex, Claude, Pi, Muse and Agy compaction records become a context_compaction event and one chat row ("Compacting context…" → "Compacted context (1m 39s) · 384k → 92k tokens"); Cursor records none.

Verified live

2026-10-06: in the owner's local app a long Plan Drift chat showed "Compacted context (2m 10s) · 236k → 24k tokens".