Epic: Self-host critical path — compiler compiles itself (M3→M5)

[PurHur]

Summary

Umbrella for implementation work between today's bootstrap (M0–M4 slice) and M5: the compiler fully compiles itself without Zend in the loop.

Target doc: docs/self-host-target.md
Gates: docs/bootstrap-selfhost.md

Living roadmap: #78

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Milestone status (May 2026 — backlog-architect probe 2026-05-29)

Verified on master via tar-copy Docker (php-compiler:22.04-dev). Latest probe comment.

Milestone	Gate	Status	Tracker
M0 minimal link	make bootstrap-selfhost-link	✅ GREEN	#2894
M2 spine / inventory	bootstrap-inventory.php --check	✅ GREEN	726/726, 0 blockers
M3 HelloWorld strict	make bootstrap-selfhost-helloworld	✅ GREEN (emit_path=native)	—
M3 JIT unit strict	inventory compile_driver	🚧 partial	#3038
M4 full-revision	make bootstrap-selfhost-full-revision-probe	✅ GREEN	#2880
M4 full ladder	make bootstrap-loop-probe	✅ GREEN	#1498
M5 vendor (committed)	bootstrap-vendor-objects.php --compile	✅ GREEN	3/3
M5 vendor rebuild	rm prelinked/*.o, BOOTSTRAP_M5_VENDOR_ALLOW_ZEND=0	🔴 RED	#3054 · PR #3050
M5 spine w/o vendor/	rename-away vendor/ test	🔴 RED	#3052
M5 gen-0 no Zend	empty build/ link	🔴 RED	#3053
M5 presenter	north-star5-verify.sh --strict	✅ GREEN	3/3

First red compile-path command:

./script/docker-exec.sh --sync-back build/selfhost-native-compile-driver -- bash -lc '
  make bootstrap-selfhost-link
  rm -f prelinked/bootstrap-vendor/*.o
  BOOTSTRAP_M5_VENDOR_ALLOW_ZEND=0 PHP_COMPILER_VENDOR_PRELINK=1 php script/bootstrap-vendor-objects.php --compile
'

Symptom: missing object file after compile (native exit 0, no .o).

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Next 3 priorities

1. #3054 / PR #3050 — native KEEP_OBJECT_FILE vendor .o rebuild
2. #3038 — JIT unit inventory compile_driver.php
3. #3052 — spine link without vendor/ tree

Parallel: #3027 · #3053 · #3032

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Verify

./script/docker-exec.sh -- bash -lc 'make bootstrap-loop-probe'
./script/docker-exec.sh -- bash -lc './script/north-star5-verify.sh --strict'
./script/docker-exec.sh --sync-back build/selfhost-native-compile-driver -- bash -lc '
  make bootstrap-selfhost-link
  rm -f prelinked/bootstrap-vendor/*.o
  BOOTSTRAP_M5_VENDOR_ALLOW_ZEND=0 PHP_COMPILER_VENDOR_PRELINK=1 php script/bootstrap-vendor-objects.php --compile
'

[PurHur]

Child issues created

#	Milestone	Title
#1493	M3	BOOTSTRAP_M3_HELLOWORLD_STRICT — native HelloWorld emit
#1494	M3	Real-lower Runtime::__construct on compile-driver spine
#1495	M3	Real-lower Runtime::loadJit / new JIT
#1496	M3	Real-lower Runtime::compile and Runtime::parse
#1497	M2	Grow compiler_lib_spine_smoke toward full inventory
#1498	M4	Bootstrap loop — native rebuilds next revision

Existing: #1416 (M5 vendor prelink), #1419 (M2 batch tracker), #1467 (src/cli.php shim)