Jeff Charles (Nov 12 2025 at 20:27): Jeff Charles (Nov 12 2025 at 20:27):What's the current thinking around when support for WASI preview 1 will be discontinued in wasmtime-wasi? I'm having trouble locating anything explicitly documented online.
Alex Crichton (Nov 12 2025 at 21:13):We've got no plans for removal at this time
Jeff Charles (Nov 12 2025 at 21:22):Given it's a preview API, how long can we safely assume it will continue to be supported by wasmtime-wasi for? Or maybe phrased differently, if support were to be discontinued, how much advance notice would we have?
Alex Crichton (Nov 12 2025 at 21:30):We don't necessarily have a formal framework around this so I don't think I can give a definitive answer for that. My gut though is that you would have plenty of notice. Everyone's more-or-less in the same boat of needing to support it, and if someone ends up being the only one in the boat of needing to support it as everyone else has moved on there's probably a migration path out of the boat which everyone else took in a sense.
Which isn't really saying much I realize, but we basically haven't created a formal policy by which it can be removed and decided advance notice and such
Chris Fallin (Nov 12 2025 at 21:34):To add a bit from my perspective: the "preview" in "preview 1" is literally in the name, but de facto it wasn't exactly a short-lived preview; everyone recognizes the significant weight it's carrying; I don't think Wasmtime as a project would try to use the "preview" wording in a "well technically..." kind of move and deprecate things quickly
Chris Fallin (Nov 12 2025 at 21:35):That said it should be our sincere hope that no one deploys new use-cases today using p1. In the embedding I work on, which hasn't shipped yet, we'll be components-first/only
Jeff Charles (Nov 12 2025 at 21:38):In my case, it's not new use cases, just legacy ones. But with WASI 1.0 on the horizon, it seems prudent to check my expectations around ongoing support for preview 1 after 1.0 is released.
Alex Crichton (Nov 12 2025 at 21:41):I don't forsee us dropping wasip1 when 1.0 is released. Perhaps a year-or-so down the road, but we understand that shifting from wasip1 to 1.0 is going to take time for some embeddings
Jeff Charles (Nov 12 2025 at 21:42):I understand this isn't a formal guarantee, but you're thinking mid-2027 then?
Alex Crichton (Nov 12 2025 at 21:45):I would be surprised if we deleted wasip1 less than a year after wasi 1.0 is released
Alex Crichton (Nov 12 2025 at 21:45):and wasi 1.0 is still in-the-works
Till Schneidereit (Nov 13 2025 at 15:00):fwiw, when we created the wasipN naming scheme we deliberately didn't mean for the "p" to expand to "preview". Instead, it's really just "p", or, if you must, "point".
I say this because as others have said, we have no plans at all to abandon support for it in any foreseeable future. And even once WASI 1.0 is released, I would fully assume that we'll continue supporting p1-3 for years to come in Wasmtime
Last updated: Dec 06 2025 at 06:05 UTC