diff --git a/SPEC.md b/SPEC.md
index a31ea27..1748687 100644
--- a/SPEC.md
+++ b/SPEC.md
@@ -77,6 +77,8 @@ auto-created from the built-in template and a message is printed to stderr.
 | `YOLO_CLAUDE_ARGS`     | `string[]` | Arguments passed to claude         |
 
 User-wide and project arrays are concatenated (user-wide first).
+Cross-source deduplication of mounts (config vs default vs CLI) happens
+later, just before `podman run` — see §3 "Volume Mount Handling".
 
 #### Scalars (project overrides user-wide; CLI overrides both)
 
@@ -127,6 +129,37 @@ concurrent yolo containers to access the same paths without EACCES errors.
 
 The `~/.claude` directory is auto-created if missing.
 
+### Mount Deduplication
+
+Just before invoking `podman run`, yolo collects every `-v` mount it
+would pass — from config (`YOLO_PODMAN_VOLUMES`, after `expand_volume`),
+from default mounts (claude home, gitconfig, workspace, worktree-original
+when applicable), and from CLI `-v` / `--volume` flags — into a single
+ordered list and deduplicates by **host path** (the first colon-delimited
+segment of the spec). When two entries share a host path, the LATER one
+in this list wins (the earlier one is dropped).
+
+Priority order, lowest to highest (last wins):
+
+1. `YOLO_PODMAN_VOLUMES` (config)
+2. Default mounts in this order: claude home, gitconfig, workspace, worktree-original
+3. CLI `-v` / `--volume`
+
+This yields:
+
+- Running yolo from a directory that's also listed in `YOLO_PODMAN_VOLUMES`
+  keeps the workspace mount (`:z`, shared/rw) and drops the config duplicate
+  (`:Z`) — avoiding podman's "duplicate mount point" rejection.
+- A worktree's original-repo mount overrides a config entry for the same path.
+- A CLI `-v` overrides config and default mounts (explicit user intent wins).
+
+Comparison is exact-string on host paths after `expand_volume` — no
+canonicalisation, so `~/data` and `$HOME/data` collapse (both expand to
+the same string) but `/foo/bar` and `/foo//bar` do not.
+
+CLI mount extraction handles `-v X`, `-v=X`, `--volume X`, `--volume=X`.
+Non-mount items in `PODMAN_ARGS` pass through unchanged.
+
 ---
 
 ## 4. Path Modes
diff --git a/bin/yolo b/bin/yolo
index f4fe95a..61e4cbf 100755
--- a/bin/yolo
+++ b/bin/yolo
@@ -172,6 +172,35 @@ expand_volume() {
     fi
 }
 
+# Deduplicate a flat list of mount specs by host path (the segment before
+# the first colon). When two entries share a host path, the LATER one in
+# the input wins; relative order among kept entries is preserved.
+# Writes result to the global DEDUPED_MOUNT_SPECS array.
+dedup_mount_specs() {
+    DEDUPED_MOUNT_SPECS=()
+    local n=$#
+    local i=1
+    while [ "$i" -le "$n" ]; do
+        local spec="${!i}"
+        local host="${spec%%:*}"
+        local j=$((i+1))
+        local found_later=0
+        while [ "$j" -le "$n" ]; do
+            local later="${!j}"
+            local later_host="${later%%:*}"
+            if [ "$later_host" = "$host" ]; then
+                found_later=1
+                break
+            fi
+            j=$((j+1))
+        done
+        if [ "$found_later" -eq 0 ]; then
+            DEDUPED_MOUNT_SPECS+=("$spec")
+        fi
+        i=$((i+1))
+    done
+}
+
 main() {
 set -e
 
@@ -190,6 +219,7 @@ USE_CONFIG=1
 YOLO_PODMAN_VOLUMES=()
 YOLO_PODMAN_OPTIONS=()
 YOLO_CLAUDE_ARGS=()
+CONFIG_MOUNT_SPECS=()
 
 while [ $# -gt 0 ]; do
     case "$1" in
@@ -321,10 +351,12 @@ if [ "$USE_CONFIG" -eq 1 ]; then
     YOLO_PODMAN_OPTIONS=("${_USER_OPTIONS[@]}" "${YOLO_PODMAN_OPTIONS[@]}")
     YOLO_CLAUDE_ARGS=("${_USER_CLAUDE_ARGS[@]}" "${YOLO_CLAUDE_ARGS[@]}")
 
-    # Process volumes and expand shorthand syntax
+    # Expand config volumes into a flat list of specs.
+    # Cross-source deduplication (config vs default mounts vs CLI) happens
+    # later, just before composing the podman command.
+    CONFIG_MOUNT_SPECS=()
     for vol in "${YOLO_PODMAN_VOLUMES[@]}"; do
-        expanded=$(expand_volume "$vol")
-        PODMAN_ARGS=("-v" "$expanded" "${PODMAN_ARGS[@]}")
+        CONFIG_MOUNT_SPECS+=("$(expand_volume "$vol")")
     done
 
     # Add podman options
@@ -343,7 +375,7 @@ CLAUDE_HOME_DIR="$HOME/.claude"
 mkdir -p "$CLAUDE_HOME_DIR"
 
 # Detect if we're in a git worktree and find the original repo
-WORKTREE_MOUNTS=()
+WORKTREE_MOUNT_SPECS=()
 gitdir_path=""
 dot_git="$(pwd)/.git"
 is_worktree=0
@@ -387,7 +419,7 @@ if [ "$is_worktree" -eq 1 ]; then
             exit 1
             ;;
         bind)
-            WORKTREE_MOUNTS+=("-v" "$original_repo_dir:$original_repo_dir:z")
+            WORKTREE_MOUNT_SPECS+=("$original_repo_dir:$original_repo_dir:z")
             ;;
         skip)
             # Do nothing - skip bind mount
@@ -398,7 +430,7 @@ if [ "$is_worktree" -eq 1 ]; then
             read -p "Bind mount original repository? [y/N] " -n 1 -r >&2
             echo >&2
             if [[ $REPLY =~ ^[Yy]$ ]]; then
-                WORKTREE_MOUNTS+=("-v" "$original_repo_dir:$original_repo_dir:z")
+                WORKTREE_MOUNT_SPECS+=("$original_repo_dir:$original_repo_dir:z")
             fi
             ;;
     esac
@@ -452,13 +484,64 @@ if [ "$USE_NVIDIA" -eq 1 ]; then
     NVIDIA_ARGS+=(--security-opt "label=disable")
 fi
 
+# Extract -v / --volume entries from PODMAN_ARGS into CLI_MOUNT_SPECS so
+# they can participate in deduplication alongside config and default
+# mounts. Remaining (non-mount) options stay in PODMAN_ARGS.
+CLI_MOUNT_SPECS=()
+_NEW_PODMAN_ARGS=()
+_i=0
+while [ "$_i" -lt "${#PODMAN_ARGS[@]}" ]; do
+    case "${PODMAN_ARGS[$_i]}" in
+        -v|--volume)
+            if [ $((_i+1)) -lt "${#PODMAN_ARGS[@]}" ]; then
+                CLI_MOUNT_SPECS+=("${PODMAN_ARGS[$((_i+1))]}")
+                _i=$((_i+2))
+            else
+                # Trailing -v with no value — let podman complain about it
+                _NEW_PODMAN_ARGS+=("${PODMAN_ARGS[$_i]}")
+                _i=$((_i+1))
+            fi
+            ;;
+        -v=*|--volume=*)
+            CLI_MOUNT_SPECS+=("${PODMAN_ARGS[$_i]#*=}")
+            _i=$((_i+1))
+            ;;
+        *)
+            _NEW_PODMAN_ARGS+=("${PODMAN_ARGS[$_i]}")
+            _i=$((_i+1))
+            ;;
+    esac
+done
+PODMAN_ARGS=("${_NEW_PODMAN_ARGS[@]}")
+
+# Compose the unified mount list, ordered lowest-priority to highest.
+# dedup_mount_specs keeps the LAST occurrence per host path, so entries
+# later in this list override earlier ones with the same host path:
+#   1. Config volumes (lowest)         — from YOLO_PODMAN_VOLUMES
+#   2. yolo default mounts             — claude home, gitconfig, workspace
+#   3. Worktree-original-repo mount    — when applicable
+#   4. CLI -v / --volume (highest)     — explicit user intent on the command line
+# This means: workspace (CWD) overrides a config entry for the same path
+# (keeping the rw, shared :z label), worktree-original beats a config entry
+# for the same path, and any CLI -v overrides everything.
+ALL_MOUNT_SPECS=()
+ALL_MOUNT_SPECS+=("${CONFIG_MOUNT_SPECS[@]}")
+ALL_MOUNT_SPECS+=("$CLAUDE_MOUNT")
+ALL_MOUNT_SPECS+=("$HOME/.gitconfig:/tmp/.gitconfig:ro,z")
+ALL_MOUNT_SPECS+=("$WORKSPACE_MOUNT")
+ALL_MOUNT_SPECS+=("${WORKTREE_MOUNT_SPECS[@]}")
+ALL_MOUNT_SPECS+=("${CLI_MOUNT_SPECS[@]}")
+dedup_mount_specs "${ALL_MOUNT_SPECS[@]}"
+
+VOLUME_ARGS=()
+for spec in "${DEDUPED_MOUNT_SPECS[@]}"; do
+    VOLUME_ARGS+=("-v" "$spec")
+done
+
 podman run --log-driver=none -it --rm \
     --userns=keep-id:uid=1000,gid=1000 \
     --name="$name" \
-    -v "$CLAUDE_MOUNT" \
-    -v "$HOME/.gitconfig:/tmp/.gitconfig:ro,z" \
-    -v "$WORKSPACE_MOUNT" \
-    "${WORKTREE_MOUNTS[@]}" \
+    "${VOLUME_ARGS[@]}" \
     -w "$WORKSPACE_DIR" \
     -e CLAUDE_CONFIG_DIR="$CLAUDE_DIR" \
     -e GIT_CONFIG_GLOBAL=/tmp/.gitconfig \
diff --git a/tests/yolo.bats b/tests/yolo.bats
index b95964b..41da5e9 100644
--- a/tests/yolo.bats
+++ b/tests/yolo.bats
@@ -32,6 +32,30 @@ load 'test_helper/common'
     assert_output "/host:/container:Z"
 }
 
+# ── dedup_mount_specs (function-level) ────────────────────────────
+
+@test "dedup_mount_specs: keeps last occurrence per host path" {
+    load_yolo_functions
+    dedup_mount_specs "/a:/a:Z" "/b:/b:Z" "/a:/a:z"
+    [ "${#DEDUPED_MOUNT_SPECS[@]}" -eq 2 ]
+    [ "${DEDUPED_MOUNT_SPECS[0]}" = "/b:/b:Z" ]
+    [ "${DEDUPED_MOUNT_SPECS[1]}" = "/a:/a:z" ]
+}
+
+@test "dedup_mount_specs: no duplicates preserves order and count" {
+    load_yolo_functions
+    dedup_mount_specs "/a:/a:z" "/b:/b:z" "/c:/c:z"
+    [ "${#DEDUPED_MOUNT_SPECS[@]}" -eq 3 ]
+    [ "${DEDUPED_MOUNT_SPECS[0]}" = "/a:/a:z" ]
+    [ "${DEDUPED_MOUNT_SPECS[2]}" = "/c:/c:z" ]
+}
+
+@test "dedup_mount_specs: empty input gives empty output" {
+    load_yolo_functions
+    dedup_mount_specs
+    [ "${#DEDUPED_MOUNT_SPECS[@]}" -eq 0 ]
+}
+
 # ── CLI flags (end-to-end with mock podman) ───────────────────────
 
 @test "--help: prints usage and exits 0" {
@@ -135,6 +159,103 @@ EOF
     podman_args_contain "$TEST_HOME/data:$TEST_HOME/data:Z"
 }
 
+@test "config: duplicate volumes across user + project are deduplicated" {
+    write_user_config << 'EOF'
+YOLO_PODMAN_VOLUMES=("~/data")
+EOF
+    write_project_config << 'EOF'
+YOLO_PODMAN_VOLUMES=("~/data")
+EOF
+    run_yolo
+    assert_success
+    local expanded="$TEST_HOME/data:$TEST_HOME/data:Z"
+    local count
+    count=$(get_podman_args | grep -cFx -- "$expanded")
+    [ "$count" -eq 1 ]
+}
+
+@test "config: duplicate volumes within a single config are deduplicated" {
+    write_project_config << 'EOF'
+YOLO_PODMAN_VOLUMES=("~/data" "~/data")
+EOF
+    run_yolo
+    assert_success
+    local expanded="$TEST_HOME/data:$TEST_HOME/data:Z"
+    local count
+    count=$(get_podman_args | grep -cFx -- "$expanded")
+    [ "$count" -eq 1 ]
+}
+
+@test "config: volume matching CWD is dropped (workspace mount wins)" {
+    # Use unquoted heredoc so $TEST_REPO interpolates
+    write_user_config <<EOF
+YOLO_PODMAN_VOLUMES=("$TEST_REPO")
+EOF
+    run_yolo
+    assert_success
+    # Workspace mount (lowercase :z) must still be present
+    podman_args_contain "$TEST_REPO:$TEST_REPO:z"
+    # Config-derived duplicate (uppercase :Z) must NOT be added
+    refute_podman_arg "$TEST_REPO:$TEST_REPO:Z"
+    # Exactly one -v entry for this host path
+    local count
+    count=$(get_podman_args | grep -cE "^${TEST_REPO}:${TEST_REPO}:[zZ]\$")
+    [ "$count" -eq 1 ]
+}
+
+@test "config: volume matching ~/.claude is dropped" {
+    write_user_config << 'EOF'
+YOLO_PODMAN_VOLUMES=("~/.claude")
+EOF
+    run_yolo
+    assert_success
+    # Default claude mount (lowercase :z) is present
+    podman_args_contain "$TEST_HOME/.claude:$TEST_HOME/.claude:z"
+    # Config-derived duplicate (uppercase :Z) is not
+    refute_podman_arg "$TEST_HOME/.claude:$TEST_HOME/.claude:Z"
+}
+
+@test "dedup: CLI -v overrides config for the same host path" {
+    write_user_config << 'EOF'
+YOLO_PODMAN_VOLUMES=("~/data")
+EOF
+    run_yolo -v "$TEST_HOME/data:/elsewhere:ro" --
+    assert_success
+    podman_args_contain "$TEST_HOME/data:/elsewhere:ro"
+    refute_podman_arg "$TEST_HOME/data:$TEST_HOME/data:Z"
+}
+
+@test "dedup: CLI -v on workspace path overrides default workspace mount" {
+    run_yolo -v "$TEST_REPO:/elsewhere:ro" --
+    assert_success
+    podman_args_contain "$TEST_REPO:/elsewhere:ro"
+    refute_podman_arg "$TEST_REPO:$TEST_REPO:z"
+}
+
+@test "dedup: config volume matching worktree original repo is dropped" {
+    # Build a fake git worktree: $TEST_REPO/.git is a file whose gitdir
+    # points to an "original" repo elsewhere under BATS_TEST_TMPDIR.
+    local tmpbase fake_orig
+    tmpbase=$(realpath "$BATS_TEST_TMPDIR")
+    fake_orig="$tmpbase/orig-repo"
+    mkdir -p "$fake_orig/.git/worktrees/test-wt"
+    rm -rf "$TEST_REPO/.git"
+    echo "gitdir: $fake_orig/.git/worktrees/test-wt" > "$TEST_REPO/.git"
+
+    write_user_config <<EOF
+YOLO_PODMAN_VOLUMES=("$fake_orig")
+EOF
+    run_yolo --worktree=bind
+    assert_success
+    # Worktree mount (lowercase :z) is present, config :Z is dropped
+    podman_args_contain "$fake_orig:$fake_orig:z"
+    refute_podman_arg "$fake_orig:$fake_orig:Z"
+    # Exactly one -v entry for this host path
+    local count
+    count=$(get_podman_args | grep -cE "^${fake_orig}:${fake_orig}:[zZ]\$")
+    [ "$count" -eq 1 ]
+}
+
 @test "config: scalar override — project USE_NVIDIA=0 overrides user USE_NVIDIA=1" {
     write_user_config << 'EOF'
 USE_NVIDIA=1