make -j4 as a resumable Wan 3.0 batch runner with an Idempotency-Key

make already knows how to run jobs in parallel (-j4), skip finished work (the output file exists) and stop on failure. That is a resumable batch runner with no code. Each shot is a target out/shot-NN.json whose recipe posts one Wan 3.0 job and keeps the response.

Two details make it safe. The response is written to $@.part and moved into place only on success, so a failed curl never leaves a file that looks finished. And the Idempotency-Key is trailer-v5-shot-$*, so if a request was accepted but the response was lost, re-running replays the original job and does not submit a second. A key reused with a different body returns 409 idempotency_conflict; change the v5 part of the key when the prompts change.

The Makefile

Recipe lines must start with a tab. Run SUME_BASE=https://api.sume.com SUME_API_KEY=... make -j4. Each 5-second 480p clip is $0.3125 on Sume, so the 12 shots are $3.75. On a local stand-in server, make -j4 printed twelve acceptances; after deleting two output files, a re-run built only those two.

SHOTS := 01 02 03 04 05 06 07 08 09 10 11 12
OUT := $(SHOTS:%=out/shot-%.json)

all: $(OUT)

out/shot-%.json:
	@mkdir -p out
	@curl -sf -o $@.part -X POST "$(SUME_BASE)/v1/videos" \
	  -H "x-api-key: $(SUME_API_KEY)" -H "content-type: application/json" \
	  -H "Idempotency-Key: trailer-v5-shot-$*" \
	  -d "{\"model\":\"wan-3.0\",\"prompt\":\"shot $*\",\"duration\":5,\"resolution\":\"480p\"}" \
	  && mv $@.part $@ && echo "shot $* accepted"

Mind the plan limits

-j4 is four concurrent submits, not four concurrent renders. A Pro workspace processes 4 jobs, queues 20, and accepts 24 in total; a submit beyond that gets 429 queue_full. Pick -j to stay well under your plan's accepted capacity, and see the pacing post for the budget numbers. On a hard stop such as 402, curl -f fails the target and make halts, which is what you want.

The target here only records acceptance. Add a second rule that polls GET /v1/videos/{id} and downloads the file once the status is completed.