[Juliusolsson05]

Summary

• When Claude Code's /compact runs (manual or auto), the synthesis turn streams <analysis>...</analysis><summary>...</summary> XML to the model. Native TUI hides it; cc-shell rendered it raw in the feed for the entire ~10–90s the model spends summarising.
• This PR detects the turn at the proxy layer (sniffing the fixed compact prompt on the last user message — feat(proxy): tag compaction-synthesis turns from request body sniff claude-code-headless#8) and renders a "Compacting conversation…" placeholder in the streaming feed instead.
• The user-facing artefacts (compact_boundary + isCompactSummary: true user entry) already had working renderers (CompactBoundaryRow, CompactSummaryRow). This PR only covers the streaming window where the XML leaked.

Architecture

mitm addon (sniff body)
  └── ProxyTransportEvent.request_shape.compaction_synthesis
       └── ClaudeProxyAdapter.ParsedRequestShape.isCompactionSynthesis
            └── channel.startTurn({ isCompactionSynthesis: true })
                 └── SemanticTurnStartedEvent.isCompactionSynthesis
                      └── foldEvent → SemanticLiveTurn.isCompactionSynthesis
                           └── StreamingTurn.tsx → "Compacting…" placeholder

All hops carry the flag as an optional, truthy-only field — non-Claude sources and older proxy adapters keep their event payloads byte-identical, and the renderer fails closed (legacy XML-leak behaviour) on a missing flag rather than over-hiding turns.

Files touched

Layer	File	Purpose
Submodule	mitmAddon.py, ClaudeProxyAdapter.ts, SemanticChannel.ts, channels/types.ts	(in claude-code-headless#8)
Renderer	src/renderer/src/workspace/workspaceState.ts	Add isCompactionSynthesis?: boolean to SemanticLiveTurn
Renderer	src/renderer/src/workspace/semantic/foldEvent.ts	Set flag on turn at turn_started
Renderer	src/renderer/src/features/feed/ui/semantic/StreamingTurn.tsx	Render placeholder when flag set

Why detect at the proxy and not in the renderer

A renderer-side heuristic (e.g. "if textSoFar starts with <analysis>") would render a flash of raw XML before the heuristic engages. The request body is the earliest layer where the signal is unambiguous — Claude Code's compaction prompt is a fixed preamble in vendor/claude-code-src/full/services/compact/prompt.ts (BASE_COMPACT_PROMPT, PARTIAL_COMPACT_PROMPT, PARTIAL_COMPACT_UP_TO_PROMPT all open with "Your task is to create a detailed summary"). The mitm addon already parses these bodies for sidecar detection, so the cost is one new regex + one new bool field.

Test plan

• Submodule build (tsc) passes ✅ (verified locally).
• cc-shell build (npm run build) passes ✅ (verified locally).
• Manual: trigger /compact (or wait for auto-compaction in a 600k+ context session). Expect "Compacting conversation…" placeholder in feed during the synthesis, then the compact_boundary divider + Conversation Summary card from CompactSummaryRow once JSONL catches up.
• Manual: normal turn renders text exactly as before (placeholder MUST NOT appear).
• Verify a per-paste debug bundle captured during compaction shows turn_started events with isCompactionSynthesis: true (and only on compaction turns).

Risk

• False positive (placeholder hides a real turn): only fires when the LAST user message begins with the literal phrase "Your task is to create a detailed summary". User typing that phrase would trigger it, but the response is also XML-shaped so the placeholder would be the correct UI anyway. Practical risk: negligible.
• False negative (XML leaks as before): possible if Claude Code changes the compact prompt preamble upstream. Detection lives in two places (mitm addon for new bodies, ClaudeProxyAdapter.parseRequestBody for legacy body_b64) — both anchor on the same phrase, so they'd fail together and fall back to the pre-fix behaviour. Recoverable, not breaking.

Dependencies

• Needs feat(proxy): tag compaction-synthesis turns from request body sniff claude-code-headless#8 merged first (this PR already bumps the submodule pointer to the branch tip b237c88).

🤖 Generated with Claude Code