diff --git a/.gitmodules b/.gitmodules
index 0c50500..8ad405e 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -19,3 +19,6 @@
 [submodule "zsh-plugins/zsh-autosuggestions"]
 	path = zsh-plugins/zsh-autosuggestions
 	url = git@github.com:zsh-users/zsh-autosuggestions.git
+[submodule "zsh-plugins/zsh-defer"]
+	path = zsh-plugins/zsh-defer
+	url = https://github.com/romkatv/zsh-defer.git
diff --git a/CLAUDE.md b/CLAUDE.md
index e89472b..78b8f7d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -11,10 +11,13 @@ Personal Zsh configuration repository: shell environment, dotfiles, aliases, fun
 ### Loading Chain
 1. `~/.zshrc` sources `load.zsh` (added by `install.sh`)
 2. `load.zsh` orchestrates everything:
-   - Locale, zsh options, plugins (git submodules), theme
+   - Locale, zsh options, `path-ethic` plugin, theme (synchronous — needed at startup)
    - Sources all `include/` files: exports, aliases, functions, keybindings, completions, history, prompt
-   - **`zsh-syntax-highlighting` MUST be loaded LAST** (after all other plugins and keybindings)
+   - **Deferred plugins** (via `zsh-defer`, interactive sessions only): `zsh-history-substring-search`, `zsh-autosuggestions`, `zsh-syntax-highlighting` — these load after the prompt appears
+   - **Non-interactive fallback**: deferred plugins load synchronously when `[[ ! -o interactive ]]` (e.g., tests)
+   - **`zsh-syntax-highlighting` MUST be loaded LAST** (after all other plugins and keybindings, even when deferred)
    - **`fpath` must include `zsh-completions/src` BEFORE `autoload`**
+   - **History-substring-search keybindings** are deferred in `load.zsh` (not in `include/keybindings`) because they depend on the deferred plugin
 
 ### Key Directories
 - **`include/`** — Modular shell config files sourced by `load.zsh`
@@ -27,10 +30,14 @@ Personal Zsh configuration repository: shell environment, dotfiles, aliases, fun
 ## Commands
 
 ```bash
-./install.sh              # Full setup: submodules, symlinks, dirs, .zshrc, neovim
+./install.sh              # Full setup: submodules, symlinks, dirs, .zshrc, neovim, zwc compilation
 make test                 # Run tests (also: ./tests/run_tests.sh)
 make update_submodules    # Update all git submodules
-reload!                   # Alias to re-source ~/.zshrc (use after editing include/ files)
+make compile              # Compile zsh files to .zwc bytecode
+make clean_zwc            # Remove all .zwc bytecode files
+reload!                   # Alias: recompiles .zwc files, then re-sources ~/.zshrc
+zsh_bench                 # Benchmark shell startup time (see scripts/zsh_bench)
+zsh_bench -n 20 -o        # 20 iterations, save results to .benchmarks/
 ```
 
 To run a single test file directly: `zsh tests/my_test.test.sh` (but prefer `make test` — the runner sets up the sandbox environment via `zsh-scriptest`).
@@ -73,7 +80,13 @@ When modifying `include/aliases`:
 - Other env vars: `include/exports`
 
 ### Scripts as CLI Commands
-Files in `scripts/` are on `$PATH` and act as standalone commands. Notable: `y` and `n` (yarn/npm wrappers), `docker_cleanup`, `git_config_hook`. New scripts placed here are automatically available as commands.
+Files in `scripts/` are on `$PATH` and act as standalone commands. Notable: `y` and `n` (yarn/npm wrappers), `docker_cleanup`, `git_config_hook`, `zsh_bench` (startup benchmarking). New scripts placed here are automatically available as commands.
+
+### Performance
+- **Startup time**: Optimized via `compinit` caching, `.zwc` bytecode compilation, and `zsh-defer` plugin deferral. Use `zsh_bench` to measure impact of changes.
+- **compinit caching** (`include/completions`): The `.zcompdump` file is only regenerated when stale (>24h) or missing. `compinit -C` is used otherwise.
+- **`.zwc` bytecode**: Zsh auto-prefers `file.zwc` over `file` when sourcing (if `.zwc` is newer). Stale `.zwc` files are harmless — zsh falls back to the source. `reload!` and `install.sh` recompile automatically. Some files (aliases, exports, functions) fail `zcompile` silently — this is expected.
+- **`zsh-defer`**: Only used in interactive sessions. Keybindings that depend on deferred plugins must also be deferred — see `load.zsh` for the pattern.
 
 ### Cross-Platform
 Changes must work on both macOS and Linux. Use platform checks (`$OSTYPE`) when behavior differs (see `__profile_git_file_timestamp` for an example).
diff --git a/Makefile b/Makefile
index 6bbfd34..dc4e85a 100644
--- a/Makefile
+++ b/Makefile
@@ -5,3 +5,13 @@ test:
 
 update_submodules:
 	git submodule update --recursive --remote
+
+compile:
+	@echo "Compiling zsh files to zwc bytecode..."
+	@zsh -c 'for f in $(BASEDIR)/load.zsh $(BASEDIR)/include/*(.) $(BASEDIR)/scripts/lib.zsh; do [[ $$f == *.zwc ]] && continue; zcompile $$f 2>/dev/null; done'
+	@echo "Done."
+
+clean_zwc:
+	@echo "Removing zwc bytecode files..."
+	@find $(BASEDIR) -name "*.zwc" -delete
+	@echo "Done."
diff --git a/dotfiles/.gitignore_global b/dotfiles/.gitignore_global
index 67fafae..90b1090 100644
--- a/dotfiles/.gitignore_global
+++ b/dotfiles/.gitignore_global
@@ -64,3 +64,7 @@ vendor/
 *.log
 *.jfr
 
+.benchmarks/
+
+# Zsh bytecode compiled files
+*.zwc
diff --git a/include/aliases b/include/aliases
index ddb5a20..f1e9741 100644
--- a/include/aliases
+++ b/include/aliases
@@ -2,7 +2,7 @@
 
 # profile self update
 alias update_profile="git -C $SHA1N_PROFILE_HOME pull --recurse-submodules origin $(git -C $SHA1N_PROFILE_HOME branch --show-current)"
-alias reload!='source $HOME/.zshrc'
+alias reload!='for f in $SHA1N_PROFILE_HOME/load.zsh $SHA1N_PROFILE_HOME/include/*(.) $SHA1N_PROFILE_HOME/scripts/lib.zsh; do [[ $f == *.zwc ]] && continue; zcompile $f 2>/dev/null; done; source $HOME/.zshrc'
 #
 # directory shortcuts
 #
diff --git a/include/completions b/include/completions
index 5793d6d..ff3d059 100644
--- a/include/completions
+++ b/include/completions
@@ -6,5 +6,10 @@ zstyle ':completion:*:default' list-colors \
   "di=1;36" "ln=1;35" "so=32" "pi=33" "ex=31" "bd=34;46" "cd=34;43" \
   "su=30;41" "sg=30;46" "tw=30;42" "ow=30;43"
 
-autoload -U compinit && compinit
+autoload -U compinit
+if [[ -n ~/.zcompdump(#qN.mh+24) ]] || [[ ! -f ~/.zcompdump ]]; then
+  compinit
+else
+  compinit -C
+fi
 autoload -U +X bashcompinit && bashcompinit
diff --git a/include/keybindings b/include/keybindings
index bc21df9..b0a02e0 100644
--- a/include/keybindings
+++ b/include/keybindings
@@ -1,8 +1,8 @@
 #!/usr/bin/env zsh
 
-# history-substring-search key bindings
-bindkey "^[[A" history-substring-search-up
-bindkey "^[[B" history-substring-search-down
+# history-substring-search key bindings are deferred in load.zsh
+# (they depend on the zsh-history-substring-search plugin which is also deferred)
+
 # line navigation
 bindkey  "^[[H"   beginning-of-line
 bindkey  "^[[F"   end-of-line
diff --git a/install.sh b/install.sh
index 5d1f096..a86d157 100755
--- a/install.sh
+++ b/install.sh
@@ -103,4 +103,11 @@ validate_shell_rc_file && install_source_command
 
 setup_neovim
 
+__profile_log_info "compiling zsh files to bytecode..."
+for f in "$SHA1N_PROFILE_HOME"/load.zsh "$SHA1N_PROFILE_HOME"/include/*(.) "$SHA1N_PROFILE_HOME"/scripts/lib.zsh; do
+  [[ "$f" == *.zwc ]] && continue
+  zcompile "$f" 2>/dev/null
+done
+__profile_log_success "bytecode compilation complete"
+
 __profile_log_info "done!"
diff --git a/load.zsh b/load.zsh
index 87c52c8..03b1d5d 100644
--- a/load.zsh
+++ b/load.zsh
@@ -12,8 +12,17 @@ export LC_CTYPE="en_US.UTF-8"
 # plugins
 fpath=($SHA1N_PROFILE_HOME/zsh-plugins/zsh-completions/src $fpath)
 source $SHA1N_PROFILE_HOME/zsh-plugins/path-ethic/path-ethic.plugin.zsh
-source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-history-substring-search/zsh-history-substring-search.zsh
-source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-autosuggestions/zsh-autosuggestions.zsh
+
+# zsh-defer for deferring non-critical interactive plugins
+if [[ -o interactive ]]; then
+  source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-defer/zsh-defer.plugin.zsh
+  zsh-defer source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-history-substring-search/zsh-history-substring-search.zsh
+  zsh-defer source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-autosuggestions/zsh-autosuggestions.zsh
+else
+  source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-history-substring-search/zsh-history-substring-search.zsh
+  source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-autosuggestions/zsh-autosuggestions.zsh
+fi
+
 # theme
 source $SHA1N_PROFILE_HOME/zsh-theme/agnoster-zsh-theme/agnoster.zsh-theme
 
@@ -25,4 +34,15 @@ source $SHA1N_PROFILE_HOME/include/completions
 source $SHA1N_PROFILE_HOME/include/history
 source $SHA1N_PROFILE_HOME/include/prompt
 
-source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
+# deferred keybindings that depend on history-substring-search
+if [[ -o interactive ]]; then
+  zsh-defer bindkey "^[[A" history-substring-search-up
+  zsh-defer bindkey "^[[B" history-substring-search-down
+fi
+
+# zsh-syntax-highlighting MUST be loaded LAST
+if [[ -o interactive ]]; then
+  zsh-defer source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
+else
+  source $SHA1N_PROFILE_HOME/zsh-plugins/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
+fi
diff --git a/scripts/zsh_bench b/scripts/zsh_bench
new file mode 100755
index 0000000..cd6eb3b
--- /dev/null
+++ b/scripts/zsh_bench
@@ -0,0 +1,81 @@
+#!/usr/bin/env zsh
+
+# zsh_bench - Measure zsh interactive shell startup time
+#
+# Usage: zsh_bench [-n iterations] [-o]
+#   -n  Number of iterations (default: 10)
+#   -o  Save results to .benchmarks/
+
+zmodload zsh/datetime
+
+local iterations=10
+local save=false
+local script_dir="${${(%):-%x}:a:h}"
+local repo_dir="${script_dir:h}"
+local benchmarks_dir="$repo_dir/.benchmarks"
+
+while getopts "n:o" opt; do
+  case $opt in
+    n) iterations=$OPTARG ;;
+    o) save=true ;;
+    \?) echo "Usage: zsh_bench [-n iterations] [-o]" >&2; return 1 ;;
+  esac
+done
+
+echo "Running $iterations iterations...\n"
+
+local -a times
+for i in $(seq 1 $iterations); do
+  local start=$EPOCHREALTIME
+  zsh -i -c exit 2>/dev/null
+  local end=$EPOCHREALTIME
+  local elapsed=$(( (end - start) * 1000 ))
+  times+=($elapsed)
+  printf "  #%2d  %6.1f ms\n" "$i" "$elapsed"
+done
+
+# Sort times
+local -a sorted
+sorted=(${(on)times})
+
+local min=${sorted[1]}
+local max=${sorted[-1]}
+local median
+local mid=$(( iterations / 2 ))
+if (( iterations % 2 == 0 )); then
+  median=$(( (sorted[mid] + sorted[mid + 1]) / 2.0 ))
+else
+  median=${sorted[mid + 1]}
+fi
+
+local sum=0
+for t in "${times[@]}"; do
+  sum=$(( sum + t ))
+done
+local avg=$(( sum / iterations ))
+
+echo ""
+echo "Results:"
+echo "  min:    $(printf '%6.1f' $min) ms"
+echo "  max:    $(printf '%6.1f' $max) ms"
+echo "  avg:    $(printf '%6.1f' $avg) ms"
+echo "  median: $(printf '%6.1f' $median) ms"
+
+if $save; then
+  mkdir -p "$benchmarks_dir"
+  local timestamp=$(date +%Y%m%d_%H%M%S)
+  local outfile="$benchmarks_dir/${timestamp}.txt"
+  {
+    echo "zsh_bench — $iterations iterations — $(date)"
+    echo ""
+    for i in $(seq 1 $iterations); do
+      printf "  #%2d  %6.1f ms\n" "$i" "${times[$i]}"
+    done
+    echo ""
+    echo "min:    $(printf '%6.1f' $min) ms"
+    echo "max:    $(printf '%6.1f' $max) ms"
+    echo "avg:    $(printf '%6.1f' $avg) ms"
+    echo "median: $(printf '%6.1f' $median) ms"
+  } > "$outfile"
+  echo "\nResults saved to $outfile"
+fi
diff --git a/zsh-plugins/zsh-defer b/zsh-plugins/zsh-defer
new file mode 160000
index 0000000..53a26e2
--- /dev/null
+++ b/zsh-plugins/zsh-defer
@@ -0,0 +1 @@
+Subproject commit 53a26e287fbbe2dcebb3aa1801546c6de32416fa