Port the fix-decode spec-v2 ownership and plan-stream fixes onto the current branch. Draft extend now keeps the scheduler-owned batch lengths committed until acceptance, binds the draft runner to the draft-extend attention backend, keeps speculative KV allocation monotonic, and lets non-graph target verify initialize metadata after DP padding. The worker also records rebound tensors on the forward stream and orders plan-stream metadata work after current-stream inputs are available.
Constraint: fix-decode commits cd8e47ed9c and 60e3956d9c address CUDA illegal-address failures in spec-v2 decode warmup paths.
Rejected: Cherry-pick the commits blindly | the current branch has intervening decode changes, so a minimal manual port kept the patch surface to the affected files.
Confidence: medium
Scope-risk: moderate
Directive: Do not move target-verify non-graph metadata initialization back into prepare_for_v2_verify without validating DP padding and NSA metadata ordering.
Tested: RED local pytest test/registered/spec/eagle/test_eagle_v2_draft_extend_contract.py -q failed 8/8 before production changes.
Tested: PYTHONPATH=python python3 -m pytest test/registered/spec/eagle/test_eagle_v2_draft_extend_contract.py -q passed 8/8 locally.
Tested: PYTHONPATH=python python3 -m py_compile python/sglang/srt/speculative/eagle_info_v2.py python/sglang/srt/speculative/eagle_worker_v2.py python/sglang/srt/speculative/spec_utils.py passed locally.
Tested: Remote g0034:cjy-glm5-new pytest for test/registered/spec/eagle/test_eagle_v2_draft_extend_contract.py passed 8/8, plus remote py_compile for the three speculative modules.
Tested: Local and remote sha256 sums matched for all four synced files.
Not-tested: Full spec-v2 decode server restart/warmup under production traffic.
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