diff --git a/.gitignore b/.gitignore
index bee8a64..1491be9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,4 @@
 __pycache__
+.cf_session*
+*.Chatfile
+Chatfile
diff --git a/SKILL.md b/AGENTS.md
similarity index 77%
rename from SKILL.md
rename to AGENTS.md
index 9a51307..b90eb1f 100644
--- a/SKILL.md
+++ b/AGENTS.md
@@ -9,7 +9,7 @@ Minimal agent collaboration via shared text files. No HTTP, no dependencies.
 
 ## The `cf` Tool
 
-Single command for all chatfile operations. State stored in `.cf_session` (no env vars needed).
+Single command for all chatfile operations. State is dynamically isolated per terminal or process (e.g., `.cf_session.pts_8` or `.cf_session.sid_1234`) to prevent agent overlap (no env vars needed).
 
 ### Room Management
 
@@ -17,12 +17,17 @@ Single command for all chatfile operations. State stored in `.cf_session` (no en
 # Create a new room (append-only)
 cf create-room myproject     # Creates myproject.Chatfile
 cf create-room               # Creates Chatfile
+cf create-room -g myproject  # Creates global room in ~/.chatfiles/
 
-# List available rooms
+# List available rooms (local and global)
 cf list-rooms
 
-# Register with a room (get unique name)
+# Delete a room (handles +a attr removal)
+cf delete-room myproject.Chatfile
+
+# Register with a room (get unique name, searches local & global)
 cf register myproject.Chatfile
+cf register myproject          # Auto-resolves to myproject.Chatfile
 # Output: swift-raven-1234
 
 # Join the room (announces entry)
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 120000
index 0000000..47dc3e3
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1 @@
+AGENTS.md
\ No newline at end of file
diff --git a/GEMINI.md b/GEMINI.md
new file mode 120000
index 0000000..47dc3e3
--- /dev/null
+++ b/GEMINI.md
@@ -0,0 +1 @@
+AGENTS.md
\ No newline at end of file
diff --git a/README.md b/README.md
index 7ff5cbd..9a40c4c 100644
--- a/README.md
+++ b/README.md
@@ -18,16 +18,22 @@ A bash tool for managing chatrooms via Chatfiles.
 ### Installation
 
 ```bash
+# Install to ~/.local/bin
+./install.sh
+
+# Or manually
 chmod +x cf
-# Optionally add to PATH or create alias
+# Add to PATH or create alias
 ```
 
 ### Commands
 
 **Room Management**
-- `cf create-room [name]` - Create a room (`name.Chatfile` or `Chatfile`), attempts to set append-only
-- `cf list-rooms` - List available rooms in current directory
-- `cf register <chatfile>` - Register with a chatfile (generates a unique name like `swift-fox-1234`)
+- `cf create-room [name]` - Create a local room (`name.Chatfile` or `Chatfile`), attempts to set append-only
+- `cf create-room -g name` - Create a global room in `~/.chatfiles/`
+- `cf list-rooms` - List local and global rooms
+- `cf delete-room <file>` - Delete a room (handles `+a` attr removal via sudo)
+- `cf register <chatfile>` - Register with a chatfile (searches local & `~/.chatfiles/`, auto-resolves `.Chatfile` extension)
 - `cf join` - Join the room (announces entry)
 - `cf leave` - Leave the room (announces exit)
 
@@ -58,4 +64,4 @@ cf await
 cf leave
 ```
 
-Session state is stored in `.cf_session` in the current directory.
+Session state is dynamically isolated per terminal or process (e.g., `.cf_session.pts_8` or `.cf_session.sid_1234`) in the current directory to prevent agent overlap. Global rooms are stored in `~/.chatfiles/`.
diff --git a/cf b/cf
index fbe87ec..77dd6fd 100755
--- a/cf
+++ b/cf
@@ -20,9 +20,38 @@ GLOBAL_DIR="$HOME/.chatfiles"
 CMD="${1:-help}"
 shift 2>/dev/null || true
 
+get_session_id() {
+    # 1. Use controlling TTY if available (stable across invocations)
+    local tty
+    tty=$(ps -o tty= -p $$ 2>/dev/null | tr -d ' \n')
+    if [ -n "$tty" ] && [ "$tty" != "?" ]; then
+        echo "${tty//\//_}"
+        return
+    fi
+    # 2. Use PPID (parent shell PID) — stable for all commands from the same shell
+    if [ -n "$PPID" ] && [ "$PPID" != "1" ]; then
+        echo "ppid_${PPID}"
+        return
+    fi
+    # 3. Last resort: own SID (may vary per invocation in detached contexts)
+    local sid
+    sid=$(ps -o sid= -p $$ 2>/dev/null | tr -d ' \n')
+    if [ -n "$sid" ]; then
+        echo "sid_${sid}"
+        return
+    fi
+    echo "$$"
+}
+
+SESSION_FILE="${CF_SESSION_FILE:-.cf_session.$(get_session_id)}"
+
 find_session() {
-    if [ -f ".cf_session" ]; then
+    if [ -f "$SESSION_FILE" ]; then
+        echo "$SESSION_FILE"
+    elif [ -f ".cf_session" ]; then
         echo ".cf_session"
+    elif [ -f "$HOME/$SESSION_FILE" ]; then
+        echo "$HOME/$SESSION_FILE"
     elif [ -f "$HOME/.cf_session" ]; then
         echo "$HOME/.cf_session"
     else
@@ -36,12 +65,14 @@ load_session() {
     read -r CHATFILE < "$sf"
     read -r MYNAME < <(sed -n '2p' "$sf")
     JOINED=$(sed -n '3p' "$sf")
+    LASTLINE=$(sed -n '4p' "$sf")
+    LASTLINE="${LASTLINE:-0}"
 }
 
 save_session() {
     local sf
-    sf=$(find_session) || sf=".cf_session"
-    printf '%s\n%s\n%s\n' "$CHATFILE" "$MYNAME" "$JOINED" > "$sf"
+    sf=$(find_session) || sf="$SESSION_FILE"
+    printf '%s\n%s\n%s\n%s\n' "$CHATFILE" "$MYNAME" "$JOINED" "$LASTLINE" > "$sf"
 }
 
 case "$CMD" in
@@ -183,12 +214,21 @@ case "$CMD" in
             noun="${NOUNS[RANDOM % ${#NOUNS[@]}]}"
             suffix=$((RANDOM % 9000 + 1000))
             MYNAME="${adj}-${noun}-${suffix}"
-            grep -q "^${MYNAME}:" "$CHATFILE" 2>/dev/null || break
-            ((attempts++))
+            # Check both message format (name:) and join/leave format ([name ...])
+            if ! grep -q -e "^${MYNAME}:" -e "\\[${MYNAME} " "$CHATFILE" 2>/dev/null; then
+                break
+            fi
+            ((attempts++)) || true
         done
 
+        if [ $attempts -ge 100 ]; then
+            echo "Failed to generate unique name after 100 attempts" >&2
+            exit 1
+        fi
+
         JOINED=""
-        printf '%s\n%s\n%s\n' "$CHATFILE" "$MYNAME" "$JOINED" > .cf_session
+        LASTLINE=0
+        printf '%s\n%s\n%s\n%s\n' "$CHATFILE" "$MYNAME" "$JOINED" "$LASTLINE" > "$SESSION_FILE"
         echo "$MYNAME"
         ;;
 
@@ -196,8 +236,9 @@ case "$CMD" in
         load_session
         [ -n "$JOINED" ] && { echo "Already joined as $MYNAME" >&2; exit 1; }
         JOINED="yes"
-        save_session
         printf '[%s joined]\n' "$MYNAME" >> "$CHATFILE"
+        LASTLINE=$(wc -l < "$CHATFILE")
+        save_session
         echo "Joined as $MYNAME"
         ;;
 
@@ -214,26 +255,54 @@ case "$CMD" in
         [ -z "$1" ] && { echo "Usage: cf send \"message\"" >&2; exit 1; }
         load_session
         [ -z "$JOINED" ] && { echo "Must join first: cf join" >&2; exit 1; }
-        printf '%s: %s\n' "$MYNAME" "$1" >> "$CHATFILE"
+        # Strip newlines to preserve one-message-one-line invariant
+        msg="${1//$'\n'/ }"
+        printf '%s: %s\n' "$MYNAME" "$msg" >> "$CHATFILE"
         ;;
 
     await|a|wait|w)
         load_session
         [ -z "$JOINED" ] && { echo "Must join first: cf join" >&2; exit 1; }
-        LAST=$(tail -n 1 "$CHATFILE" | cut -d: -f1)
-        if [ "$LAST" = "$MYNAME" ]; then
-            tail -f -n 0 "$CHATFILE" | head -n 1
-        else
-            tail -n 1 "$CHATFILE"
-        fi
+        exec 3< <(tail -n +$((LASTLINE + 1)) -f "$CHATFILE")
+        TAILPID=$!
+        trap 'kill $TAILPID 2>/dev/null' EXIT
+        while IFS= read -r line <&3; do
+            ((LASTLINE++))
+            case "$line" in
+                \[*) save_session; continue ;;
+                "${MYNAME}:"*) save_session; continue ;;
+            esac
+            save_session
+            echo "$line"
+            break
+        done
+        kill $TAILPID 2>/dev/null
+        exec 3<&-
+        trap - EXIT
         ;;
 
     send-await|sa)
         [ -z "$1" ] && { echo "Usage: cf send-await \"message\"" >&2; exit 1; }
         load_session
         [ -z "$JOINED" ] && { echo "Must join first: cf join" >&2; exit 1; }
-        printf '%s: %s\n' "$MYNAME" "$1" >> "$CHATFILE"
-        tail -f -n 0 "$CHATFILE" | head -n 1
+        msg="${1//$'\n'/ }"
+        printf '%s: %s\n' "$MYNAME" "$msg" >> "$CHATFILE"
+        exec 3< <(tail -n +$((LASTLINE + 1)) -f "$CHATFILE")
+        TAILPID=$!
+        trap 'kill $TAILPID 2>/dev/null' EXIT
+        while IFS= read -r line <&3; do
+            ((LASTLINE++))
+            case "$line" in
+                \[*) save_session; continue ;;
+                "${MYNAME}:"*) save_session; continue ;;
+            esac
+            save_session
+            echo "$line"
+            break
+        done
+        kill $TAILPID 2>/dev/null
+        exec 3<&-
+        trap - EXIT
         ;;
 
     read|cat)
@@ -277,7 +346,7 @@ Messaging:
 Info:
   cf status               Show current session
 
-State stored in .cf_session (current directory)
+State stored in .cf_session.<tty|ppid> or .cf_session (current directory)
 Global rooms stored in ~/.chatfiles/
 EOF
         ;;
diff --git a/test_bugs.sh b/test_bugs.sh
new file mode 100755
index 0000000..bc71fef
--- /dev/null
+++ b/test_bugs.sh
@@ -0,0 +1,345 @@
+#!/bin/bash
+# Bug reproduction tests for cf
+# Each test isolates in a temp dir with a fake HOME
+
+set -u
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+NC='\033[0m'
+
+TESTS_RUN=0
+TESTS_PASSED=0
+TESTS_FAILED=0
+ORIGINAL_DIR="$(pwd)"
+CF_PATH="$(realpath ./cf)"
+TEST_DIR=""
+
+setup() {
+    TEST_DIR=$(mktemp -d)
+    cd "$TEST_DIR"
+    export HOME="$TEST_DIR/home"
+    export CF_SESSION_FILE=".cf_session"
+    mkdir -p "$HOME"
+}
+
+teardown() {
+    cd "$ORIGINAL_DIR"
+    if [ -d "$TEST_DIR" ]; then
+        find "$TEST_DIR" -type f \( -name "*.Chatfile" -o -name "Chatfile" \) \
+            -exec sudo chattr -a {} \; 2>/dev/null || true
+        rm -rf "$TEST_DIR"
+    fi
+}
+
+run_test() {
+    TESTS_RUN=$((TESTS_RUN + 1))
+    local name="$1"
+    shift
+    local output
+    if output=$("$@" 2>&1); then
+        TESTS_PASSED=$((TESTS_PASSED + 1))
+        echo -e "${GREEN}BUG CONFIRMED${NC} $name"
+    else
+        TESTS_FAILED=$((TESTS_FAILED + 1))
+        echo -e "${RED}NOT REPRODUCED${NC} $name"
+        [ -n "$output" ] && echo "$output" | sed 's/^/  /'
+    fi
+}
+
+# ============================================================================
+# Bug 1: Register silently uses duplicate name when all 100 attempts exhaust
+# ============================================================================
+# The loop tries 100 times, but if all collide it exits without error and
+# uses the last (colliding) name. We simulate by pre-filling the chatfile
+# with every possible adj-noun-suffix combination that RANDOM could produce
+# during the test.
+#
+# Approach: patch the check — we can't control RANDOM, but we CAN show the
+# failure mode by making grep always match (every name "exists").
+
+bug1_collision_crash() {
+    setup
+
+    # Create chatfile manually (no chattr +a) so we can fill it
+    printf '[system]: Chatroom. Format: Name: msg. Append only.\n' > Chatfile
+
+    # The retry loop uses ((attempts++)) which with set -e crashes on first
+    # collision because ((0++)) evaluates to 0, which bash treats as exit
+    # code 1. Fill half the namespace to trigger a collision quickly.
+    ADJS=(swift bold calm keen sage wild bright dark quick slow)
+    NOUNS=(fox owl raven wolf bear hawk crane lynx deer hare)
+    for adj in "${ADJS[@]}"; do
+        for noun in "${NOUNS[@]}"; do
+            for suffix in $(seq 1000 5499); do
+                printf '%s-%s-%s: taken\n' "$adj" "$noun" "$suffix"
+            done
+        done
+    done >> Chatfile
+
+    # Try registering repeatedly until we hit a collision
+    local crashed=false
+    for i in $(seq 1 30); do
+        rm -f .cf_session
+        "$CF_PATH" register Chatfile >/dev/null 2>&1
+        if [ $? -ne 0 ]; then
+            crashed=true
+            break
+        fi
+    done
+
+    if $crashed; then
+        teardown
+        return 0  # Bug confirmed: register crashes on name collision
+    fi
+
+    teardown
+    echo "No collision in 30 attempts (unlikely but possible)"
+    return 1
+}
+
+# ============================================================================
+# Bug 2: await misparses join/leave/system lines
+# ============================================================================
+# When the last line is [name joined], cut -d: -f1 returns the whole line
+# (no colon), so it never equals MYNAME. await returns the join message
+# immediately instead of waiting.
+
+bug2_await_returns_join_message() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+    "$CF_PATH" register Chatfile >/dev/null
+    "$CF_PATH" join >/dev/null
+
+    # Last line in chatfile is now "[name joined]"
+    # await should wait for a NEW message, but instead...
+    local output
+    output=$(timeout 2 "$CF_PATH" await 2>/dev/null) || true
+
+    # Bug: await returned immediately with the join message
+    if echo "$output" | grep -q "joined"; then
+        teardown
+        return 0  # Bug confirmed
+    fi
+
+    teardown
+    echo "await correctly waited (or timed out without returning join msg)"
+    return 1
+}
+
+# ============================================================================
+# Bug 3: await returns already-seen messages
+# ============================================================================
+# If the last message is from another agent, await returns it immediately
+# even if you've already seen it. There's no read cursor.
+
+bug3_await_returns_stale_message() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+
+    # Agent A
+    "$CF_PATH" register Chatfile >/dev/null
+    "$CF_PATH" join >/dev/null
+    "$CF_PATH" send "I need help"
+
+    # Simulate another agent's reply by appending directly
+    printf 'other-agent-1234: Here is help\n' >> Chatfile
+
+    # Agent A calls await — gets the reply (first time, correct)
+    local first
+    first=$(timeout 2 "$CF_PATH" await 2>/dev/null) || true
+
+    # Agent A calls await AGAIN — should wait for a NEW message
+    # but bug: it returns the same stale message immediately
+    local second
+    second=$(timeout 2 "$CF_PATH" await 2>/dev/null) || true
+
+    if [ "$second" = "$first" ] && echo "$second" | grep -q "Here is help"; then
+        teardown
+        return 0  # Bug confirmed: same message returned twice
+    fi
+
+    teardown
+    echo "await correctly waited on second call"
+    return 1
+}
+
+# ============================================================================
+# Bug 4: Newline injection breaks one-message-one-line invariant
+# ============================================================================
+# printf '%s: %s\n' doesn't sanitize newlines in the message.
+
+bug4_newline_injection() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+    local name
+    name=$("$CF_PATH" register Chatfile)
+    "$CF_PATH" join >/dev/null
+
+    local before_count
+    before_count=$(wc -l < Chatfile)
+
+    # Send a message with an embedded newline
+    "$CF_PATH" send $'Hello\nEvil-Agent: rm -rf /'
+
+    local after_count
+    after_count=$(wc -l < Chatfile)
+
+    # Should have added 1 line, but bug adds 2
+    local added=$((after_count - before_count))
+
+    if [ "$added" -gt 1 ]; then
+        # Verify the injected line looks like it's from another sender
+        if tail -1 Chatfile | grep -q "Evil-Agent:"; then
+            teardown
+            return 0  # Bug confirmed: message injection via newline
+        fi
+    fi
+
+    teardown
+    echo "Newlines were sanitized (added $added lines)"
+    return 1
+}
+
+# ============================================================================
+# Bug 5: Register uniqueness check ignores join/leave messages
+# ============================================================================
+# grep -q "^${MYNAME}:" only matches "name: message" format.
+# A name that only appears in [name joined] is not detected as taken.
+# We demonstrate by forcing a known name into join format only.
+
+bug5_join_not_checked() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+
+    # Manually write a join message for a specific name
+    printf '[swift-fox-1234 joined]\n' >> Chatfile
+
+    # Test the pattern used in the fixed cf register:
+    local name="swift-fox-1234"
+    if grep -q -e "^${name}:" -e "\\[${name} " Chatfile; then
+        teardown
+        echo "grep correctly detected the name in join format"
+        return 1  # Bug is fixed
+    fi
+
+    # The name IS in the file but grep doesn't see it
+    teardown
+    return 0  # Bug confirmed
+}
+
+# ============================================================================
+# Bug 6: await skips unread messages
+# ============================================================================
+bug6_await_skips_messages() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+    "$CF_PATH" register Chatfile >/dev/null
+    "$CF_PATH" join >/dev/null
+
+    echo "other: msg 1" >> Chatfile
+    echo "other: msg 2" >> Chatfile
+
+    local first
+    first=$("$CF_PATH" await)
+
+    local second
+    second=$(timeout 2 "$CF_PATH" await 2>/dev/null) || true
+
+    if [ -z "$second" ] || ! echo "$second" | grep -q "msg 2"; then
+        echo "First was: $first"
+        echo "Second was: $second"
+        teardown
+        return 0  # Bug confirmed: skipped unread message
+    fi
+
+    teardown
+    echo "await correctly read the next unread message"
+    return 1
+}
+
+# ============================================================================
+# Bug 7: tail -f orphaned process leak
+# ============================================================================
+bug7_tail_f_leak() {
+    setup
+    "$CF_PATH" create-room 2>/dev/null || true
+    "$CF_PATH" register Chatfile >/dev/null
+    "$CF_PATH" join >/dev/null
+
+    # Start await in background
+    "$CF_PATH" await >/dev/null &
+    local await_pid=$!
+    
+    sleep 0.5
+    echo "other: msg 1" >> Chatfile
+    
+    # Wait for await to exit
+    wait "$await_pid" 2>/dev/null || true
+    sleep 0.5
+
+    # Check if tail -f is still running with our Chatfile
+    if pgrep -f "tail -f -n 0.*Chatfile" >/dev/null; then
+        pkill -f "tail -f -n 0.*Chatfile"
+        teardown
+        return 0  # Bug confirmed: tail -f leaked
+    fi
+
+    teardown
+    echo "No orphaned tail -f processes found"
+    return 1
+}
+
+# ============================================================================
+# Bug 8: State isolation (overlapping session files)
+# ============================================================================
+bug8_state_isolation() {
+    setup
+    unset CF_SESSION_FILE  # Test the actual isolation logic
+    "$CF_PATH" create-room 2>/dev/null || true
+    
+    local name1
+    name1=$("$CF_PATH" register Chatfile)
+    
+    # Run register in a new session (different SID/TTY)
+    if command -v setsid >/dev/null; then
+        local name2
+        name2=$(setsid "$CF_PATH" register Chatfile)
+        
+        local status_name
+        status_name=$("$CF_PATH" status | grep Session | cut -d' ' -f2)
+        
+        # If the original session's status shows the second name, they overlapped
+        if [ "$name1" != "$status_name" ] && [ "$name2" = "$status_name" ]; then
+            teardown
+            return 0  # Bug confirmed: overlapping session state
+        fi
+    fi
+
+    teardown
+    echo "Sessions properly isolated"
+    return 1
+}
+
+# ============================================================================
+# Run All Bug Reproduction Tests
+# ============================================================================
+
+echo "Bug Reproduction Tests for cf"
+echo "=============================="
+echo ""
+
+run_test "Bug 1: register crashes on first name collision (set -e + arithmetic)" bug1_collision_crash
+run_test "Bug 2: await returns join/leave messages instead of waiting" bug2_await_returns_join_message
+run_test "Bug 3: await returns already-seen messages (no read cursor)" bug3_await_returns_stale_message
+run_test "Bug 4: Newline injection breaks message format" bug4_newline_injection
+run_test "Bug 5: Uniqueness check ignores join/leave format" bug5_join_not_checked
+run_test "Bug 6: await skips unread messages" bug6_await_skips_messages
+run_test "Bug 7: tail -f orphaned process leak" bug7_tail_f_leak
+run_test "Bug 8: State isolation (overlapping session files)" bug8_state_isolation
+
+echo ""
+echo "=============================="
+echo "Total: $TESTS_RUN"
+echo -e "Confirmed: ${GREEN}$TESTS_PASSED${NC}"
+echo -e "Not reproduced: ${RED}$TESTS_FAILED${NC}"
diff --git a/test_cf.sh b/test_cf.sh
index a694525..e6cafa6 100755
--- a/test_cf.sh
+++ b/test_cf.sh
@@ -26,6 +26,7 @@ setup() {
     cd "$TEST_DIR"
     # Create mock global dir to avoid touching real ~/.chatfiles
     export HOME="$TEST_DIR/home"
+    export CF_SESSION_FILE=".cf_session"
     mkdir -p "$HOME"
 }