Serverside panic on `graph.get_relative_up(position).unwrap()`

If I launch Hypermine on the master branch with block_reach set to 2, I get the following panic:

2026-03-04T01:39:06.557360Z  INFO found config at $HOME/.config/hypermine/client.toml
2026-03-04T01:39:06.557490Z  INFO using save file $HOME/.local/share/hypermine/default.save
2026-03-04T01:39:06.569751Z  INFO spawning character id=f1644f405148e95c name=gyrola
2026-03-04T01:39:06.569772Z  INFO connected locally id=1v1

thread '<unnamed>' (17977) panicked at common/src/character_controller/mod.rs:37:45:
called `Option::unwrap()` on a `None` value
stack backtrace:
2026-03-04T01:39:06.584560Z  INFO Guessed window scale factor: 1
2026-03-04T01:39:06.813072Z  INFO Vulkan instance layers: ["VK_LAYER_VALVE_steam_fossilize_64", "VK_LAYER_VALVE_steam_overlay_64", "VK_LAYER_VALVE_steam_fossilize_32", "VK_LAYER_VALVE_steam_overlay_32", "VK_LAYER_MESA_device_select", "VK_LAYER_NV_optimus", "VK_LAYER_MESA_overlay", "VK_LAYER_INTEL_nullhw"]
2026-03-04T01:39:06.860890Z  INFO selected device name="NVIDIA GeForce RTX 3060"
   0: __rustc::rust_begin_unwind
             at /rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/std/src/panicking.rs:689:5
   1: core::panicking::panic_fmt
             at /rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/panicking.rs:80:14
   2: core::panicking::panic
             at /rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/panicking.rs:150:5
   3: core::option::unwrap_failed
             at /rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/option.rs:2175:5
   4: core::option::Option<T>::unwrap
             at /home/patrick/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1016:21
   5: common::character_controller::run_character_step
             at ./common/src/character_controller/mod.rs:37:45
   6: server::sim::Sim::step
             at ./server/src/sim.rs:546:13
   7: server::Server::on_step
             at ./server/src/lib.rs:185:40
   8: server::Server::run::{{closure}}
             at ./server/src/lib.rs:140:44
   9: <tracing::instrument::Instrumented<T> as core::future::future::Future>::poll
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-0.1.44/src/instrument.rs:321:15
  10: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /home/patrick/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/future/future.rs:133:9
  11: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /home/patrick/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/future/future.rs:133:9
  12: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:753:70
  13: tokio::task::coop::with_budget
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/task/coop/mod.rs:167:5
  14: tokio::task::coop::budget
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/task/coop/mod.rs:133:5
  15: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:753:25
  16: tokio::runtime::scheduler::current_thread::Context::enter
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:442:19
  17: tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:752:44
  18: tokio::runtime::scheduler::current_thread::CoreGuard::enter::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:840:68
  19: tokio::runtime::context::scoped::Scoped<T>::set
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/context/scoped.rs:40:9
  20: tokio::runtime::context::set_scheduler::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/context.rs:176:38
  21: std::thread::local::LocalKey<T>::try_with
             at /home/patrick/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:513:12
  22: std::thread::local::LocalKey<T>::with
             at /home/patrick/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:477:20
  23: tokio::runtime::context::set_scheduler
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/context.rs:176:17
  24: tokio::runtime::scheduler::current_thread::CoreGuard::enter
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:840:27
  25: tokio::runtime::scheduler::current_thread::CoreGuard::block_on
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:740:24
  26: tokio::runtime::scheduler::current_thread::CurrentThread::block_on::{{closure}}
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:200:33
  27: tokio::runtime::context::runtime::enter_runtime
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/context/runtime.rs:65:16
  28: tokio::runtime::scheduler::current_thread::CurrentThread::block_on
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/scheduler/current_thread/mod.rs:188:9
  29: tokio::runtime::runtime::Runtime::block_on_inner
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/runtime.rs:368:52
  30: tokio::runtime::runtime::Runtime::block_on
             at /home/patrick/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.49.0/src/runtime/runtime.rs:340:18
  31: client::main::{{closure}}
             at ./client/src/main.rs:59:25
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
2026-03-04T01:39:08.125104Z  INFO exiting due to closed window

The game is still playable, with just the client active, not the server, so I cannot, for instance, break or place any blocks.

Start in common/src/character_controller/mod.rs:37, then follow the reported call path through server/src/sim.rs:546 and server/src/lib.rs:185. Reproduce with block_reach set to 2 and inspect why graph.get_relative_up(position) returns None. Done means the server no longer panics in this scenario and block interaction remains functional.