fix: send player loaded before spawn on 1.21.4+ - #3960
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Java Edition 1.21.4 added the serverbound player_loaded packet. Send it before Mineflayer's spawn event on initial load and respawn so callers cannot interact while vanilla still ignores player actions. Reproduce on unmodified upstream: npm run mocha_test -- test/externalTest.js --grep '^mineflayer_external 1\.21\.4v crafting$' --retries 0 The full-title grep limits Mocha to that one version and test even though externalTest.js declares every supported version. Upstream fails after 20 seconds waiting for windowOpen; this change passes the same single test.
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u9g
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Aug 23, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 27, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 27, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 27, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 27, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 27, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 29, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Aug 31, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
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Sep 4, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
u9g
added a commit
that referenced
this pull request
Sep 4, 2026
The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change).
rom1504
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Sep 5, 2026
* Speed up furnace external test by fast-forwarding CookTime The furnace test spent ~10s per version waiting out a real 200-tick smelt. Instead, after asserting the smelt has genuinely started (0 < progress < 1), merge CookTime:195s into the furnace block entity and wait for the output slot to populate — the output is still produced by the vanilla tick path, so all assertions are unchanged. Cuts the test from ~12s to ~3s per version, ~4.5 minutes across the matrix. The await runs 250-320ms on every tested version, so it uses a tight 500ms timeout: if the merge silently does nothing (wrong field name or command for a future version), the test fails fast instead of sitting out the real smelt. Verified against real servers on all 28 tested versions (1.21.4+ placement verified on top of PR #3960, which master needs for those versions regardless of this change). * test(furnace): gate the NBT fast-forward on minecraft-data features Replaces the hardcoded version comparisons with hasDataCommand and furnaceNbtUsesSnakeCase (PrismarineJS/minecraft-data#1260).
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Summary
Since Java 1.21.4, vanilla defers initial block and item interactions until it receives
player_loadedor its fallback expires. Mojang documents the packet after the initial loading-terrain screen and again after respawn in the 1.21.4 release notes.Mineflayer emits
spawnwithout sending the packet, so actions started immediately from aspawnlistener can be silently ignored. This sendsplayer_loadedimmediately beforespawn, including after respawn.The behavior is gated with
bot.supportFeature('sendsPlayerLoadedPacket'), defined by the corresponding minecraft-data PR #1224. This PR therefore depends on that feature being merged and released throughnode-minecraft-data.Reproduction
Run the existing 1.21.4 crafting test by itself on current Mineflayer master:
npm run mocha_test -- test/externalTest.js \ --grep '^mineflayer_external 1\.21\.4v crafting$' \ --retries 0Before:
After:
Related work
This overlaps with the 26.2 work in #3926. PR #3958 independently identified the same missing packet among broader 26.x changes; this PR isolates the lifecycle fix and applies it to every version described by the minecraft-data feature flag.
Sending
player_loadedbeforespawnpreserves Mineflayer's contract thatspawnlisteners may begin interacting with the server.Verification
npm run lint