diff --git a/.pythonstartup.py b/.pythonstartup.py
new file mode 100644
index 0000000..b01ab7d
--- /dev/null
+++ b/.pythonstartup.py
@@ -0,0 +1,101 @@
+"""Auto-imports for interactive REPL sessions.
+
+Usage: activate         — core imports (Proxmark3, Cmd, etc.)
+       activate sim     — + SimSession, all transponder models
+       activate sniff   — + SniffSession, trace decoders
+       activate all     — everything
+"""
+import os
+import sys
+
+_MODE = os.environ.get("PM3PY_MODE", "core")
+
+# --- Import groups ---
+
+CORE = [
+    ("pm3py", "Proxmark3"),
+    ("pm3py", "Cmd"),
+    ("pm3py", "PM3Status"),
+    ("pm3py", "PM3Error"),
+    ("pm3py", "PM3Response"),
+]
+
+SIM = [
+    ("pm3py.sim", "SimSession"),
+    ("pm3py.sim", "DualInterfaceSession"),
+    ("pm3py.sim", "SoftwareMedium"),
+    ("pm3py.sim", "TableCompiler"),
+    ("pm3py.sim", "RFFrame"),
+    # Transponder models
+    ("pm3py.transponders.hf.iso14443a.base", "Tag14443A_3"),
+    ("pm3py.transponders.hf.iso14443a.base", "Tag14443A_4"),
+    ("pm3py.transponders.hf.iso14443a.nxp.mifare_classic", "MifareClassicTag"),
+    ("pm3py.transponders.hf.iso14443a.nxp.desfire", "DesfireTag"),
+    ("pm3py.transponders.hf.iso14443a.ndef", "NfcType2Tag"),
+    ("pm3py.transponders.hf.iso14443a.ndef", "NfcType4Tag"),
+    ("pm3py.transponders.hf.iso15693.base", "Tag15693"),
+    ("pm3py.transponders.hf.iso15693.type5", "NfcType5Tag"),
+    ("pm3py.transponders.hf.iso15693.nxp.nxp_icode", "NxpIcodeTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.icode_slix", "IcodeSlixTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.icode_slix2", "IcodeSlix2Tag"),
+    ("pm3py.transponders.hf.iso15693.nxp.icode3", "Icode3Tag"),
+    ("pm3py.transponders.hf.iso15693.nxp.icode_dna", "IcodeDnaTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.ntag5_platform", "Ntag5PlatformTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.ntag5_switch", "Ntag5SwitchTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.ntag5_link", "Ntag5LinkTag"),
+    ("pm3py.transponders.hf.iso15693.nxp.ntag5_boost", "Ntag5BoostTag"),
+    ("pm3py.transponders.lf.em.em4100", "EM4100Tag"),
+    ("pm3py.transponders.lf.hid.hid", "HIDProxTag"),
+    ("pm3py.transponders.lf.atmel.t5577", "T5577Tag"),
+    ("pm3py.transponders.implants", "xEM"),
+    ("pm3py.transponders.implants", "xNT"),
+    ("pm3py.transponders.implants", "xM1"),
+    ("pm3py.transponders.implants", "FlexDF"),
+    ("pm3py.transponders.implants", "NExT"),
+]
+
+SNIFF = [
+    ("pm3py.sniff", "SniffSession"),
+    ("pm3py.trace", "parse_tracelog"),
+    ("pm3py.trace", "decode_15693"),
+    ("pm3py.trace", "decode_ndef_annotation"),
+    ("pm3py.trace", "format_sniff_line"),
+]
+
+# --- Mode selection ---
+
+MODES = {
+    "core": [CORE],
+    "sim": [CORE, SIM],
+    "sniff": [CORE, SNIFF],
+    "all": [CORE, SIM, SNIFF],
+}
+
+groups = MODES.get(_MODE, [CORE])
+imports = []
+for group in groups:
+    imports.extend(group)
+
+# --- Load ---
+
+loaded = {}
+failed = {}
+
+for module_name, attr_name in imports:
+    try:
+        module = __import__(module_name, fromlist=[attr_name])
+        obj = getattr(module, attr_name)
+        globals()[attr_name] = obj
+        loaded[attr_name] = module_name
+    except Exception as e:
+        failed[attr_name] = (module_name, str(e))
+
+# --- Report ---
+
+if loaded:
+    print(f"[pm3py:{_MODE}] Loaded: {', '.join(loaded.keys())}")
+
+if failed:
+    print(f"\n[pm3py:{_MODE}] Failed:")
+    for name, (mod, err) in failed.items():
+        print(f"  {name} from {mod} -> {err}")
diff --git a/activate b/activate
new file mode 100644
index 0000000..782271a
--- /dev/null
+++ b/activate
@@ -0,0 +1,21 @@
+# pm3py venv activation with mode-based auto-imports.
+# Usage: source activate           — core (Proxmark3, Cmd, etc.)
+#        source activate sim       — + SimSession, transponder models
+#        source activate sniff     — + SniffSession, trace decoders
+#        source activate all       — everything
+#
+# Then:  python    — REPL with auto-imports
+#        ipython   — IPython with auto-imports (if installed)
+
+# Activate the venv
+source "$(dirname "${BASH_SOURCE[0]}")/.venv/bin/activate"
+
+# Set mode and PYTHONSTARTUP
+export PM3PY_MODE="${1:-core}"
+export PYTHONSTARTUP="$(dirname "${BASH_SOURCE[0]}")/.pythonstartup.py"
+
+# Update prompt to show mode
+PS1="(pm3py:${PM3PY_MODE}) ${_OLD_VIRTUAL_PS1:-\$ }"
+export PS1
+
+echo "pm3py env ready (mode: ${PM3PY_MODE}). Run 'python' for REPL with auto-imports."