diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index ec98c967a..db1099c2a 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -35,6 +35,7 @@ updates:
     labels:
       - "dependencies"
       - "python"
+      - "pip"
     schedule:
       interval: "daily"
     cooldown:
diff --git a/AGENTS.md b/AGENTS.md
index c9bab0b47..92503f719 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -386,3 +386,12 @@ task warrants them:
 
 These practices exist to keep the repository accurate, testable, maintainable,
 and honest about its current state.
+
+## Fast development builds
+
+`make dev-build` and `make dev-test` compile with the opt-in Cranelift
+backend and the mold linker configured in `tools/dev-fast/config.toml`.
+They require a nightly toolchain and, on Linux, a `mold` binary on the
+`PATH`. The fragment is passed explicitly with `--config`, so release,
+coverage, and verification builds are unaffected; never copy its contents
+into `.cargo/config.toml`, which Cargo applies to every build.
diff --git a/Makefile b/Makefile
index 49ef3b055..e51104bb1 100644
--- a/Makefile
+++ b/Makefile
@@ -182,3 +182,14 @@ clean:
 	$(CARGO) clean
 	$(CARGO) clean --manifest-path $(GITHUB_TOOL_MANIFEST)
 	rm -rf $(WASM_SHARED_TARGET_DIR)
+
+# Opt-in accelerated debug builds (Cranelift + mold); requires a nightly
+# toolchain. See AGENTS.md and tools/dev-fast/config.toml.
+DEV_FAST_CONFIG ?= tools/dev-fast/config.toml
+
+.PHONY: dev-build dev-test
+dev-build: ## Build debug binaries with Cranelift and mold
+	cargo --config "$(DEV_FAST_CONFIG)" build
+
+dev-test: ## Run tests with Cranelift and mold
+	cargo --config "$(DEV_FAST_CONFIG)" test
diff --git a/tools/dev-fast/config.toml b/tools/dev-fast/config.toml
new file mode 100644
index 000000000..01e7f8990
--- /dev/null
+++ b/tools/dev-fast/config.toml
@@ -0,0 +1,31 @@
+# Canonical opt-in Cargo configuration fragment for accelerated local debug
+# builds.
+#
+# This configuration is deliberately kept out of `.cargo/config.toml`.
+# Cargo auto-discovers that path, so anything placed there applies to
+# release packaging, coverage, and verification builds, which must keep
+# the supported LLVM backend and platform linker. In a consuming
+# repository this fragment lives at `tools/dev-fast/config.toml` and is
+# passed explicitly with `cargo --config tools/dev-fast/config.toml ...`
+# from `make dev-build` and `make dev-test`.
+#
+# Repositories that set repository-wide `rustflags` in `.cargo/config.toml`
+# must restate them in the target table below. Cargo joins the rustflags of
+# every matching `[target.*]` entry (target-triple and `cfg` tables alike),
+# but the joined target rustflags take precedence over `[build].rustflags`
+# rather than merging with it.
+
+[unstable]
+codegen-backend = true
+
+# Cranelift trades runtime performance for compile speed, so it applies to
+# the dev profile only. The `make dev-*` targets never build release
+# artefacts.
+[profile.dev]
+codegen-backend = "cranelift"
+
+# mold ships for Linux only, so the flag is gated behind a target `cfg`. On
+# macOS and Windows the table simply does not apply and the platform default
+# linker is used.
+[target.'cfg(target_os = "linux")']
+rustflags = ["-Clink-arg=-fuse-ld=mold"]