OndrejDrapalik · Sep 8, 2026 · Sep 8, 2026 · Sep 8, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,16 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Changed
+
+- The shipped default template is `muse` (Meta's Muse Code), not `base`: a new box
+  with nothing configured boots an agent ready to work instead of an empty image.
+  `base` stays in the picker, stays the create-time fallback for a template that is
+  not on your cluster, and is still excluded from fleet rosters. A fleet roster now
+  drops templates that are agentless (`base`, or `[fleet.agents] <name> = ""`)
+  rather than whatever `[sandbox] template` names, so the default is a member.
+  `[sandbox] template = "base"` restores the old behaviour.
+
 ### Added
 
 - `[templates.<name>] model = "…"` and `reasoning = "…"`: pin which model a

diff --git a/README.md b/README.md
@@ -245,22 +245,22 @@ either, you get the chooser:
 ```
   E2B template for my-worktree
 
-   ▸ [1] base                     default
+   ▸ [1] muse                     default
      [2] claude
      [3] codex
      [4] opencode
      [5] amp
      [6] grok
      [7] droid
      [8] prime
-     [9] muse
+     [9] base
 
   ↑/↓ · j/k move   enter confirm   number jumps   t type a name   q default
 ```
 
-`t` takes any name, so the menu is a shortcut and not a whitelist. `base` is
-E2B's minimal image — fine for trying the flow, tight on disk for real work. For
-that, [build a custom template](https://e2b.dev/docs/sandbox-template) with your
+`t` takes any name, so the menu is a shortcut and not a whitelist. `muse` (Meta's
+Muse Code) is the shipped default; `base` is E2B's minimal image, fine for trying
+the flow or a plain shell, tight on disk for real work. For that, [build a custom template](https://e2b.dev/docs/sandbox-template) with your
 toolchain and roomier resources, and point `[sandbox].template` at it.
 
 > **Regions are named, not spelled as hosts.** `[sandbox] region = "us" | "eu"`

diff --git a/config/config.example.toml b/config/config.example.toml
@@ -61,14 +61,18 @@
 # the plugin owns. An old `domain =` is an error, not an ignored line — silently
 # dropping it would move an EU user's boxes to US without a word.
 
-# E2B template. "base" (default) is minimal and always available — fine to try
-# the flow, but tight on disk/tools for real work.
-# RECOMMENDED: build a bigger CUSTOM template (more disk + CPU, your toolchain
-# baked in) and set it here — see the README and install.sh. Public agent
-# templates (claude, codex, opencode, … https://e2b.dev/docs/agents) also
-# work but can run out of space. (Claude Code's template is named `claude`;
+# E2B template a NEW box boots from when nothing else decided (no --template, no
+# branch rule, no picker answer). "muse" (default) is Meta's Muse Code agent, ready
+# to work once [templates.muse.env] holds a META_API_KEY. "base" is E2B's minimal
+# image, always available and always in the picker: fine to try the flow or for a
+# plain shell, tight on disk/tools for real work, and the image a create falls back
+# to when the chosen template is not built on your cluster.
+# RECOMMENDED for real work: build a bigger CUSTOM template (more disk + CPU, your
+# toolchain baked in) and set it here, see the README and install.sh. The other
+# public agent templates (claude, codex, opencode, … https://e2b.dev/docs/agents)
+# also work but can run out of space. (Claude Code's template is named `claude`;
 # Devin has no prebuilt template — install it into a base sandbox yourself.)
-template     = "base"
+template     = "muse"
 
 # The menu `e2b-box open` offers when it has to BUILD a sandbox and nothing else
 # decided which template (no --template, no matching rule below). The plugin

diff --git a/docs/headless-run.md b/docs/headless-run.md
@@ -58,8 +58,7 @@ The template decides which agent works the task, and `run` needs that agent's
 | `muse` | `muse exec --yolo --user-input-auto-resolve --prompt-file $HOME/.herdr-e2b-task.md` |
 | `prime` | `prime-agent -p --no-session "$(cat $HOME/.herdr-e2b-task.md)"` |
 
-`base` (the default) and your own templates are refused by name before anything
-boots. An invented flag fails to launch and reads exactly like an agent
+`base` and your own templates are refused by name before anything boots. An invented flag fails to launch and reads exactly like an agent
 that did nothing. Teach one in `[run.agents]`:
 
 ```toml

diff --git a/src/config.js b/src/config.js
@@ -16,10 +16,13 @@ export { AUTH_PATH, CONFIG_PATH } from "./config-paths.js"
 const CLI_CONFIG_PATH = path.join(os.homedir(), ".e2b", "config.json")
 
 const DEFAULTS = {
-  // Safe minimal default that always exists. For real work build a bigger
-  // custom template (more disk/CPU + your toolchain) and set it here — see the
-  // README "Recommended: a bigger custom template" and install.sh.
-  template: "base",
+  // What a box boots from when nothing else decided: Meta's Muse Code template,
+  // an agent ready to work rather than an empty image to install one into. `base`
+  // (E2B's minimal image, always present) stays in the picker and stays the
+  // fallback a create lands on when the chosen template is not on the cluster.
+  // For real work build a bigger custom template (more disk/CPU + your toolchain)
+  // and set it here, see the README "Recommended: a bigger custom template".
+  template: "muse",
   templateRules: [], // [{pattern, template}] per-branch overrides
   // The `open` picker's menu, in the order shown. Ships with the plugin so the
   // picker is useful out of the box; `[sandbox] templates` in config REPLACES it.
@@ -1013,7 +1016,7 @@ export function templateRuleMatches(branch, cfg) {
  * always offered so "just boot the usual one" is one keypress.
  */
 /**
- * The templates a FLEET may be built from: the same list, minus the plain default.
+ * The templates a FLEET may be built from: the same list, minus the agentless ones.
  *
  * A fleet is several coding agents working one checkout in parallel, so a box with
  * no agent in it is not a member — it is a shell nobody asked for. `base` is also
@@ -1026,7 +1029,15 @@ export function templateRuleMatches(branch, cfg) {
  * keeps offering it: one plain box is a perfectly good thing to want.
  */
 export function fleetTemplateChoices(cfg) {
-  return templateChoices(cfg).filter((t) => t !== cfg.template)
+  // Agentless means: `base` (E2B's plain image, the one public template whose name
+  // is not a CLI), or a template the user mapped to "" in `[fleet.agents]`, the
+  // documented "plain shell, start nothing" for a control arm or their own plain
+  // image. NOT the configured default: since the default became an agent template
+  // (`muse`), filtering it out would drop the one member most people want.
+  const agents = cfg?.fleetAgents || {}
+  return templateChoices(cfg).filter(
+    (t) => t !== "base" && !(Object.prototype.hasOwnProperty.call(agents, t) && agents[t] === ""),
+  )
 }
 
 export function templateChoices(cfg) {

diff --git a/test/cli.test.sh b/test/cli.test.sh
@@ -484,15 +484,21 @@ out=$(cd "$RUNREPO" && "$E2B" run --task x --dashboard 2>&1); rc=$?
 { [ "$rc" -eq 2 ] && printf '%s' "$out" | grep -q "doesn't take"; } \
   && ok "run with an unknown flag → exit 2" || bad "run unknown flag (rc=$rc, out=$out)"
 
-# The default template is `base`, which ships no agent, and a template nobody has
-# verified a headless mode for has no default either. Both are refused BY NAME with
-# the fix on the line, and nothing boots.
-# An empty config dir, so the developer's own [sandbox] template cannot answer here.
-NOCFG="$TMP/nocfg"; mkdir -p "$NOCFG"
-out=$(cd "$RUNREPO" && HERDR_PLUGIN_CONFIG_DIR="$NOCFG" "$E2B" run --task x 2>&1); rc=$?
+# `base` ships no agent, and a template nobody has verified a headless mode for has
+# no default either. Both are refused BY NAME with the fix on the line, and nothing
+# boots.
+out=$(cd "$RUNREPO" && "$E2B" run -t base --task x 2>&1); rc=$?
 { [ "$rc" -eq 2 ] && printf '%s' "$out" | grep -q "no headless agent command for template 'base'" \
   && printf '%s' "$out" | grep -q "\[run.agents\]"; } \
-  && ok "run on the default template → refused by name, exit 2" || bad "run on base (rc=$rc, out=$out)"
+  && ok "run -t base → refused by name, exit 2" || bad "run on base (rc=$rc, out=$out)"
+# With nothing configured the shipped default template is `muse`, an agent, so a bare
+# `run` has something to run. An empty config dir, so the developer's own [sandbox]
+# template cannot answer here.
+NOCFG="$TMP/nocfg"; mkdir -p "$NOCFG"
+out=$(cd "$RUNREPO" && HERDR_PLUGIN_CONFIG_DIR="$NOCFG" "$E2B" run --task x --dry-run 2>/dev/null); rc=$?
+{ [ "$rc" -eq 0 ] && [ "$(printf '%s' "$out" | jq -r '.template')" = "muse" ] \
+  && printf '%s' "$out" | jq -e '.agentCommand | startswith("muse exec ")' >/dev/null; } \
+  && ok "run with no -t and no config → the shipped default, muse" || bad "default template (rc=$rc, out=$out)"
 out=$(cd "$RUNREPO" && "$E2B" run -t my-project/my-template --template-any --task x 2>&1); rc=$?
 { [ "$rc" -eq 2 ] && printf '%s' "$out" | grep -q "for template 'my-project/my-template'" \
   && printf '%s' "$out" | grep -q "pass -t one of: claude, codex, opencode, amp, grok, droid, muse, prime"; } \

diff --git a/test/config.test.js b/test/config.test.js
@@ -662,17 +662,20 @@ test("resolveEnv: amp gets the welcome-splash skip, and a user can still overrid
   )
 })
 
-test("fleetTemplateChoices: a fleet is agents only — the plain default is not a member", () => {
+test("fleetTemplateChoices: a fleet is agents only: agentless templates are not members", () => {
   // A fleet is several coding agents on one checkout, so a box with no agent in it
   // is a shell nobody asked for. `base` is also the one template whose name is not
   // a CLI, so a member built from it typed `base` into a sandbox shell and waited
   // for a TUI that never came.
   const cfg = { template: "base", templates: ["claude", "codex", "base"], templateRules: [] }
   assert.deepEqual(fleetTemplateChoices(cfg), ["claude", "codex"])
-  // Filtered by the CONFIGURED default, not the literal "base", so someone whose
-  // plain image is called something else gets the same treatment.
-  const mine = { template: "plain", templates: ["plain", "claude"], templateRules: [] }
-  assert.deepEqual(fleetTemplateChoices(mine), ["claude"])
+  // The configured default is NOT what is filtered: the shipped default is `muse`, an
+  // agent, and the member most people want. A plain image of your own leaves the
+  // roster the documented way, `[fleet.agents] plain = ""`.
+  const mine = { template: "muse", templates: ["muse", "plain", "claude"], templateRules: [], fleetAgents: { plain: "" } }
+  assert.deepEqual(fleetTemplateChoices(mine), ["muse", "claude"])
+  const unmapped = { template: "muse", templates: ["muse", "plain", "claude"], templateRules: [] }
+  assert.deepEqual(fleetTemplateChoices(unmapped), ["muse", "plain", "claude"])
   // And the box picker is untouched — one plain box is a fine thing to want.
   assert.deepEqual(templateChoices(cfg), ["claude", "codex", "base"])
 })