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The JIT was ~1.077x SLOWER than the interpreter on the boot bench because it paid a DOUBLE lookup per block: block_cache.lookup_or_build (to get the DecodedBlock — the ~9.7% "block decode/cache" bucket) THEN JitCache's own lookup. On a JIT-cache HIT the DecodedBlock is not needed: the freshness key is (start_pc, mem.page_version(pc)), reconstructible from mem alone (build_block stops at the 4 KiB page boundary, so both caches key on the same single-page version). Phase A adds a JIT-specialized superblock runner that runs chained (2nd..Nth) blocks straight from the JIT cache, skipping block_cache on hits: - CompiledBlock now carries sync_sensitive (copied from DecodedBlock) — the chain STOP guard needs it and a JIT hit has no DecodedBlock. - JitCache::run_fresh(pc, ctx, mem): lookup-only fast path; computes pv itself via mem.page_version (SMC coherence); Some((result, sync)) on a fresh hit, None on a miss (never compiles — compilation stays on the DecodedBlock path). New unit test run_fresh_hit_miss. - run_superblock_jit (parallel to run_superblock, used when jit_cache is Some): first block + JIT misses use block_cache.lookup_or_build + run_or_compile (rebuild inline on miss so chain length — and the schedule — is unchanged); chained hits use run_fresh. Non-Continue break lazily rebuilds a block_ptr for worker_epilogue's SYSCALL/Trap diagnostics. Same raw-ctx-ptr discipline; shared next_pc_breaks_chain helper keeps both loops' chaining decisions in lockstep. Interp run_superblock untouched except the extracted helper call. Results (n=200M --gpu-inline): block_cache calls 11.4M -> 991k (-91% on the JIT run — run_fresh handles 91% of block acquisitions). Throughput: JIT 1.077x slower -> ~1.03x FASTER than interp (best-of-8 interleaved: JIT 3.73s vs interp 3.84s) — first time the JIT beats the interpreter. Golden n200m BYTE-IDENTICAL: interp==golden (path untouched), JIT==golden, JIT+REGCACHE==golden, and JIT budget=1 == interp budget=1. 19 jit tests green. Phase B (native inline chaining, targets the 23.6% loop body) deferred — see plan. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>