hide-consumed: parseCallText fails on tag-prefixed compress call text, so live anchor args are never stubbed

[ranxianglei]

Found while investigating billion-context-pi #336 (PR #225, closed).

Bug: rewriteCompressText/parseCallText in src/hide-consumed.ts JSON.parse the compress tool-call text starting at index 0. When the adapter message carries a leading metadata tag (pi appends <acp ...>mNNNNN</acp> tags to message text), the parse fails, the call is treated as unparseable, and live compress anchors keep their full summary args forever — the summary text is duplicated in every request (measured 21.6K tokens of duplicated args in session 01a07b3c).

Fix: locate the JSON by scanning for the first { before parsing (as done in the closed PR #225). Independent of any reasoning feature — worth shipping on its own.

[ranxianglei]

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[bot] 🏷 Duplicate screening: related to open PR #226 — its item 3 ships the same fix (skip the tag prefix before JSON.parse + 200-char summary stub). Not a duplicate, though: #226 bundles it with the reasoningReplay feature, while #230 explicitly asks for the fix on its own ("Independent of any reasoning feature"), and the mechanics differ — #226 strips the exact ref-tag prefix via regex, #230 prescribes the generic first-{ scan (closed PR #225's approach). Kept open and proceeded. (No label tool available to me, so I couldn't add the 重复 tag.)

Triage (bug):

1. Reproduce/verify — confirmed on master. rewriteCompressText (src/hide-consumed.ts:22) does JSON.parse(text) at index 0; pi persists the rendered ref tag in front of the tool-call text, so the parse always threw on tagged calls. Reproduced both symptoms:
   • tag-prefixed mixed call (live m5–m6 + consumed m8–m9): rewrite fails → call treated as unparseable → consumed entry never dropped;
   • fully-live call with a 5000-char summary: master has no stubbing at all → full summary duplicated with the rendered acp_summary in every request (the 21.6K measured in session 01a07b3c).
2. Layer judgment — the issue describes the root cause, not just the symptom. "Args never stubbed" has two layers: (a) the index-0 parse failure blocks any rewrite of tagged calls; (b) even for untagged calls, master never stubbed fully-live calls (the rewrite early-returned when all entries were live). The fix has to address both to reach the stated end state.
3. Solution assessment — the prescribed fix (scan for first {) is correct and more general than fix: break the reasoning context floor and live-anchor summary duplication #226's regex (any leading metadata, not just the exact tag shape). I also ported the stubbing unit from closed PR feat: reasoningReplay policy + anchor arg stubs + extraTokens accounting #225, since the end state is "args are stubbed": summaries >200 chars become a 200-char stub in kept calls (active + newest orphans); the rendered block summary stays the authoritative copy.

Fix: #232 (branch 2026-09-09_hide-consumed-tag-prefix, based on latest master)

• parseCallText locates the JSON at the first {, preserves the tag prefix on output
• compactCompressText stubs long summaries in all kept compress calls
• 4 new tests in tests/hide-consumed-stub.test.ts, incl. tag-prefixed cases built from real renderVisibleRefs output
• Verified: typecheck clean, 628/628 tests pass, build succeeds; both repro cases now pass

Note for #226: if #232 merges first, #226 should drop its hide-consumed hunk (item 3). If you'd rather keep #226's regex variant, say so and I'll rework #232 to match.