# Adapt Model > Guide feasibility analysis, minimal implementation, review, and evidence validation for a new AFD model on GPU, NPU, or both. Use when Codex must adapt or review a new vLLM model, establish its native and AFD execution contract, add model-specific tests, or validate model support. Do not use for ordinary model explanations, existing-only E2E execution, generic bug fixes, or vLLM upgrades. - Skill: `vllm-project/adapt-model` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add vllm-project/adapt-model` - Raw SKILL.md: https://api.skillmd.com/api/skills/vllm-project/adapt-model/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: vllm-project (https://skillmd.com/u/vllm-project) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/vllm-project/adapt-model --- # Adapt a new AFD model Use this skill as an executable, staged workflow. Treat every target model as new: start from the repository baseline and exact native source. Do not assume that a target adapter, successful runtime, recipe, or E2E evidence exists. Use related AFD models only as implementation references; do not copy their model assumptions without checking the target contract. Keep the workflow model-specific but the public AFD runtime stable. Preserve native model lifecycle, ordinary forward, residual/norm behavior, quantization, parameter paths, weight mapping/loading, and supported parallelism unless the exact contract proves that a narrow adapter extension is necessary. ## Non-negotiable boundaries - Do not modify vLLM or vLLM-Ascend source trees. - Default to zero common Runner, Connector, or runtime changes for a model-only adaptation. If the exact target contract proves an existing public interface insufficient, stop and report that gap before expanding scope. - Do not modify native FusedMoE/MoERunner, routing, dispatch/combine, quantization, or kernel code for a model-only adaptation. - Construct only the active role's large execution modules. Never construct the full opposite role and delete it afterward. - Preserve non-AFD native registry resolution and behavior. - Filter checkpoint paths once, preserve original names and tensor objects, and delegate the filtered iterator to the native loader. - Do not reimplement native packed mapping, expert mapping, TP/EP sharding, quantization scales, or loader bookkeeping. - Keep GPU and NPU evidence independent. A GPU result never proves NPU support. - Do not commit, push, or publish unless the user explicitly requests it. - Read and obey the repository `AGENTS.md`, applicable design documents, and backend validation instructions before changing code or allocating hardware. ## Task modes Accept one of these modes. Do not silently combine them. - `feasibility`: source inspection and a minimal implementation/validation plan; do not change production code or allocate hardware. - `implementation`: implement only the explicitly requested adapter and its focused tests, then stop at the CPU gate unless hardware validation is also requested and authorized. - `review`: inspect an existing adapter or patch against the exact native contract and AFD boundaries; do not redesign unrelated code. - `validation`: validate an already selected implementation and exact model, checkpoint, backend, connector, topology, and mode; do not expand scope. ## Required inputs Discover these before asking the user; required unknowns remain `UNKNOWN` and must not be inferred from another architecture or backend: ```text task_mode: feasibility | implementation | review | validation model: family, exact architecture, checkpoint/config backend_scope: gpu | npu | both runtime: vllm: exact version/commit vllm_ascend: exact tuple when NPU is in scope target: connector, topology, eager/graph, TP/DP/EP/PP, quantization, DBO/uBatch oracle: native baseline and correctness/accuracy threshold when validating ``` ## Phase state machine Run these phases in order. At the end of every phase record: ```text phase: status: PASS | FAIL | BLOCKED | UNKNOWN | SKIPPED evidence: blocker: next_allowed_action: ``` Do not enter a later phase when a required earlier phase is `FAIL`, `BLOCKED`, or a required fact is `UNKNOWN`. ```text ESTABLISH_IDENTITY -> INSPECT_NATIVE_CONTRACT -> DESIGN_MINIMAL_ADAPTER -> IMPLEMENT_MINIMAL_ADAPTER -> CPU_CONTRACT_GATE -> NATIVE_EAGER_CONTROL -> AFD_EAGER_GATE -> OPTIONAL_GRAPH/DBO/PARALLELISM -> REPORT ``` The state machine is a superset. Task mode determines the stopping point; mark phases outside the requested scope `SKIPPED`. | Task mode | Required stopping point | | --- | --- | | `feasibility` | Phases 0–2, then report; do not implement or allocate hardware. | | `review` | Phases 0–2 plus read-only contract checks as needed, then report. | | `implementation` | Phases 0–4, then report; continue to hardware only when explicitly requested and authorized. | | `validation` | Confirm Phases 0–2 read-only, skip implementation when no code change is required, then run only the applicable validation gates. | ## Phase 0 — Establish identity Before reading or changing implementation code, record: - AFD checkout, branch, commit, and dirty status; - exact vLLM source path and commit; exact vLLM-Ascend source and software stack when NPU is in scope; - model family, architecture class, checkpoint path, config, weight index, and quantization; - requested role split, connector, topology, runner generation, and mode; - available hardware and authorization for GPU/NPU use; - relevant repository recipes, tests, and runbooks. Do not require or assume a prior successful target-model checkout. Establish a fresh native control in Phase 5. Preserve unrelated dirty changes. Prefer an isolated branch/worktree for an implementation. Never reset or delete user changes to make the identity clean. ## Validation cell identity Before native or AFD execution, freeze one validation cell: - repository/adapter SHA; - model/checkpoint; - vLLM/runtime and plugin state; - runner generation and connector; - Attention/FFN topology; - TP/DP/EP/PP; - quantization; - eager/graph mode; - multiprocessing/runtime launch mode; - memory and `max_model_len` knobs; - prompt and sampling parameters; - relevant environment variables. Keep model-semantic and non-AFD runtime settings identical to the native control where applicable: checkpoint, prompt, sampling parameters, quantization, runner generation, and native TP/DP/EP/PP dimensions. AFD-specific role topology, connector settings, process layout, and necessary role-local resource settings may differ; record those differences explicitly. Any other change creates a new validation cell; do not compare results across cells as one retry sequence. ## Evidence discipline - Read the repository's local instructions and runbooks for execution details; do not duplicate backend- or machine-specific commands in this skill. - Verify the effective runtime configuration and logs instead of treating an intended setting as proof that it was applied. - If a runtime workaround is needed, create a separate validation cell, change one variable at a time, and report it as runtime configuration rather than an adapter change. - Preserve the original failure artifacts, resource state, and cleanup evidence so that later results cannot silently replace the failed control. ## Phase 1 — Inspect the exact native contract Read the pinned native implementation for the target architecture and record the symbols and signatures that affect the requested scope: - architecture registry and class hierarchy; - CausalLM, Model, Decoder, and Layer constructors; - ordinary `forward`, residual and norm order; - layer factory or `decoder_layer_type` injection points; - Attention, dense MLP, MoE, gate, shared expert, and experts boundaries; - PP placeholders, embedding/final-output lifecycle, and sampling ownership; - native parameter paths, packed projections, expert paths, FP8/quant scales, and `load_weights` delegation; - TP/DP/EP/PP, graph/compile, DBO, and speculative/MTP behavior relevant to the requested first slice. Record sampling/final-output ownership on the Attention side and any connector-driven FFN daemon boundary; the FFN side does not acquire KV-cache, scheduler, or final-output ownership merely because it computes FFN output. Also record dummy-run, warmup, profiling, graph capture/replay, cleanup, and exception behavior when those paths are part of the requested scope. Inspect AFD's actual model API calls in the selected Attention/FFN runners, ForwardContext metadata installation, connector metadata, DBO helpers, and existing model-side proxy. Do not invent a model API because a related adapter has one. The adapter must expose only methods the selected runner actually calls, such as `compute_ffn_output` or `get_experts_layer_indices`. Inspect the repository's documented test and launch contract before designing new commands, and make the adapter's accepted scope match that contract. Do not access an optional or dynamically installed context field directly just because reflection is discouraged. Use the existing typed AFD metadata/helper and preserve any proven fallback behavior; add a focused test for the context variant. ## Phase 2 — Choose the smallest adapter Apply this decision tree: ```text Existing AFD wrapper already covers the native architecture? yes -> register/configure and add focused tests only no -> continue Native Model exposes a layer factory or decoder_layer_type hook? yes -> subclass/inject a role-aware Layer; do not copy the Model constructor no -> continue Native CausalLM exposes a model_cls hook? yes -> use it no -> copy only the required constructor, with exact patch markers Native Layer.forward calls mlp(hidden_states) at the desired boundary? yes -> reuse the existing parameter-free remote proxy no -> add a native-compatible experts facade only when the call contract proves that the experts boundary is required ``` Default implementation surface: - one model adapter file; - registration/config rewrite only where the repository requires it; - model-specific CPU contract tests; - a model-specific E2E scenario only when hardware validation is requested. Do not add a common proxy, runtime, protocol, coordinator, or capabilities file unless the existing implementation demonstrably cannot satisfy the exact target contract and at least one concrete consumer is identified. Separate ownership into three questions: | Ownership | Rule | | --- | --- | | Execution | Attention executes Attention; FFN executes dense MLP or native MoE. | | Large parameters | Do not construct/load non-owner Attention projections, gates, routed/shared experts, or dense/MoE weights. | | Lifecycle | Embedding, decoder norms, final norm, lm_head, PP placeholders, and tied weights follow native lifecycle needs; a documented dual-role exception is valid. | Do not turn lifecycle-only modules into `PPMissingLayer` or make them single-owner solely to satisfy an abstract ownership rule. Prove the native construction, PP, loader, and runner requirements first. For the model adapter: - keep native Attention, dense MLP, MoE runner/kernel, and quantization; - keep native ordinary forward whenever the role boundary permits it; - implement only role-aware construction, model-specific runner entry delegation, stage/proxy integration, and path-to-role classification; - keep gate-on-FFN as the default unless the target and requested scope prove an Attention-side gate contract; - fail closed for unsupported gate, MTP, topology, or backend combinations. When copying native code, add the required reason, source file, source commit, exact signature/return type, and paired `PATCH START/END` markers immediately around AFD-specific differences. Copy constructors only when a native hook is unavailable. Do not copy native forward or loader loops when composition or delegation is sufficient. ## Phase 3 — Implement the smallest change Before editing, write a short ledger: ```text files to add/modify: new public abstractions: copied native functions and source lines: common runner/connector/runtime changes: default zero; any exception requires a proven exact-contract gap and an identified consumer unsupported combinations: ``` Implement in this order: 1. registration/config isolation; 2. role-aware layer/model construction; 3. existing proxy or the narrowest proven facade; 4. top-level FFN runner API delegation; 5. one-pass role-aware checkpoint filtering; 6. focused tests. Do not change the common runtime to compensate for an incomplete adapter. If a native contract cannot be expressed without a broad copy or common change, stop and report the gap before expanding the patch. Reuse the repository's documented validation entry point when it can express the requested scope. Add model-specific test code only when the existing contract cannot express the required behavior; do not create a parallel execution harness to hide an adapter gap. For repository E2E execution, read and delegate to `.agents/skills/run-e2e/SKILL.md` whenever the existing E2E interface can express the requested validation cell. Do not duplicate its hardware detection, provisioning, pytest-marker execution, or cleanup workflow here. If the target model lacks a repository-owned E2E scenario, add only the model-specific scenario required by the requested scope, then hand execution back to `run-e2e`. ## Phase 4 — CPU contract gate Run compile/import/static checks and relevant CPU tests before hardware. Cover only features used by the target model, including as applicable: - registration isolation and native non-AFD behavior; - exact constructor/forward/loader signatures and patch markers; - native decorator/MRO/compile-support behavior; - real layer schedule and role parameter manifests; - absence of non-owner large parameters before checkpoint loading; - stable native parameter paths for Attention, dense, MoE, gate, shared expert, and quantization scales; - one-shot checkpoint filtering, unchanged names/tensors, native loader result; - top-level FFN API and layer-index contract; - proxy send → DBO yield → recv ordering, metadata, stage fallback, and error; - PP/tied-weight/lifecycle exceptions when used; - explicit negative tests for unsupported mode/backend/topology combinations. A mock with a tiny invented model is not evidence for a large target model. Use target config-derived layer counts and expert counts in static fixtures when feasible. Mark unavailable dependencies as skipped or blocked; never call them passed. ## Phase 5 — Native eager control gate Establish a native vLLM eager control before starting AFD. The control must use the exact target checkpoint and a runner/runtime comparable to the requested AFD path. Record startup, weight loading, readiness, one correctness request, and cleanup. If native construction, weight loading, readiness, or the first correctness request fails: - preserve the original logs and resource state; - identify the closest worker/root traceback, not only a serving-wrapper error; - mark native execution `FAIL` or `BLOCKED`; - mark AFD parity `SKIPPED`; - do not continue expanding the adapter or use an AFD-only result as an oracle. Diagnostics may create a separate validation cell only when necessary. Change one variable at a time, state the hypothesis, and never merge its result into the original control. For a backend or kernel failure, first keep AFD disabled and run the smallest single-variable diagnostic that can distinguish native runtime from adapter contract. If the fallback passes, classify the original cell as a native runtime failure and use the passing cell as the explicit AFD oracle; do not silently change the adapter or call the workaround a model fix. ## Phase 6 — AFD eager gate Only after the native control passes, run the narrowest requested AFD path: - exact model and checkpoint; - exact AFD checkout and runtime; - same runner generation, comparable precision, and the same native TP/DP/EP/PP dimensions unless the claimed AFD scope explicitly changes them; - one connector and one smallest supported role split; - eager before graph, DBO, performance, or wider parallelism. Reuse the repository's documented validation entry point and lifecycle helpers; for repository-owned E2E, delegate to `.agents/skills/run-e2e/SKILL.md` rather than duplicating hardware detection, provisioning, pytest-marker execution, or cleanup here. If a model-specific scenario is absent, add only the scenario needed for the requested scope; do not create a second execution harness. Keep model-semantic and non-AFD runtime settings identical to the native control where applicable: checkpoint, prompt, sampling parameters, quantization, runner generation, and native model-parallel dimensions. AFD-specific role topology, connector settings, process layout, and necessary role-local resource settings may differ; record those differences explicitly. Any other change creates a new validation cell. Confirm the expected native-to-AFD architecture mapping on both roles and that the FFN role reached native dense/MoE computation before claiming a request pass. Validate, as applicable: - Attention and FFN construction and load completion; - connector initialization and cleanup; - send/receive order and layer/stage association; - native FFN compute on the FFN role; - native/AFD output parity using an explicit oracle; - process, port, GPU/NPU, and reservation cleanup. Text equality alone is a narrow oracle. Report when token IDs, hidden states, logits, graph/DBO, or multi-rank behavior were not measured. ## Phase 7 — Optional extensions Run graph, DBO, TP/DP/EP/PP, gate variants, MTP, quantization variants, NPU, or performance only after the eager gate passes and only when the requested scope includes them. Treat GPU and NPU as separate lanes with separate native controls, contracts, commands, logs, and readiness results. ### GPU extension lane For GPU claims, inspect and validate the exact GPU worker/runner, P2P connector, CUDA eager/graph path, TP/EP/DBO settings when claimed, and model-specific GPU E2E evidence. ### NPU extension lane For NPU claims, independently inspect the exact vLLM-Ascend/software tuple, NPU worker/runner, selected CAMP2P/CAM connector, ACL graph/uBatch behavior, MoE/quantization/weight-loading overlays, and model-specific NPU E2E evidence. Never derive one backend's support from the other. ## Failure and rollback protocol On any failure: 1. stop the next phase; 2. save the exact source/runtime/command/environment/log/cleanup identity; 3. classify the failure as adapter contract, native runtime, connector, resource, or unknown; 4. preserve the diff and evidence. Revert only an isolated speculative change when the user authorizes it or the worktree is explicitly disposable; otherwise leave the change in place for review, preserving unrelated user changes; 5. report the next smallest diagnostic action. Never change runner, topology, plugin state, memory limits, and adapter code in one retry. Never claim model support from import success, construction alone, FFN weight loading alone, or an AFD-only smoke when native control failed. ## Evidence report Report these fields without omitting scope: ```text Model: family, architecture, checkpoint, config Source: AFD checkout/commit; vLLM and vLLM-Ascend source/runtime Adapter: changed files, ownership, copied functions, common-code changes Claimed scope: backend, connector, runner, topology, mode, quantization, gate CPU: commands and pass/fail/skipped/blocked results Native control: command, readiness, correctness oracle, cleanup AFD eager: roles, load, connector, output/parity, cleanup Extensions: graph/DBO/parallelism/NPU results or explicit exclusions Execution: GPU/NPU not-run | passed | failed | blocked Readiness: GPU/NPU validated | experimental | unverified | unsupported Unknowns and blockers Validator and date ``` Use `unsupported` only when the implementation explicitly rejects the combination. Use `failed` for an executed failure and `blocked` when an external dependency or environment prevents the test. ## Completion gate Before declaring a new model adapted, verify: - the target was treated as new and no prior success was assumed; - exact native and AFD identities are recorded; - the minimal adapter decision tree was followed; - no unnecessary common abstraction or native forward/loader copy was added; - role construction and lifecycle exceptions are evidenced; - CPU contract gate passed; - native eager control passed before AFD parity; - AFD eager, connector, cleanup, and oracle evidence match the claimed scope; - the adapter files deployed to the validation cell match the reviewed working tree by commit or content hash; - any runtime workaround is listed separately from the adapter diff; - all unrun, failed, blocked, and unsupported combinations are explicit.