From dfe378c8ae17f1858a3f0864b8c65c83c364e73e Mon Sep 17 00:00:00 2001
From: Bryan Helmkamp <bryan@brynary.com>
Date: Fri, 11 Sep 2026 12:36:29 -0600
Subject: [PATCH] Stop re-blanking BASH_ENV in fabro's exec policy

The driver's Bash helper now blanks BASH_ENV at launch on every provider
whatever the caller passed, so fabro's exec policy no longer inserts the
blank itself and the test double no longer filters it back out. The
Host-backed test that a caller's startup file never runs stays.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
---
 lib/components/fabro-sandbox/src/exec.rs         | 14 +++++++-------
 lib/components/fabro-sandbox/src/test_support.rs |  2 --
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/lib/components/fabro-sandbox/src/exec.rs b/lib/components/fabro-sandbox/src/exec.rs
index 49b5d9266..fd8e84210 100644
--- a/lib/components/fabro-sandbox/src/exec.rs
+++ b/lib/components/fabro-sandbox/src/exec.rs
@@ -29,8 +29,8 @@ use std::time::Duration;
 use fabro_static::EnvVars;
 use fabro_types::{CommandTermination, ExecOutputTail};
 use sandbox_driver::{
-    BASH_ENV_VAR, Exec, ExecControls, ExecFailure, ExecResult, ExecSpec, ExecStreamingResult,
-    SpawnSpec, StdioProcess, Termination,
+    Exec, ExecControls, ExecFailure, ExecResult, ExecSpec, ExecStreamingResult, SpawnSpec,
+    StdioProcess, Termination,
 };
 use tokio_util::sync::CancellationToken;
 
@@ -212,14 +212,13 @@ impl<'a> SandboxExec<'a> {
     }
 
     /// The explicit environment after policy: credential-shaped names pass
-    /// only under `TrustCaller`, and the Bash helper's `BASH_ENV` blank
-    /// wins over any caller value, so a worker's startup file never runs
-    /// inside a sandboxed `bash -c`.
+    /// only under `TrustCaller`. The driver's Bash helper blanks `BASH_ENV`
+    /// at launch whatever the caller passed, so a worker's startup file
+    /// never runs inside a sandboxed `bash -c`.
     fn apply_env_policy(&self, env: &mut BTreeMap<String, String>) {
         if self.env_policy == ExplicitEnvPolicy::FilterSensitive {
             env.retain(|key, _| !is_sensitive_env_var(key));
         }
-        env.insert(BASH_ENV_VAR.to_string(), String::new());
     }
 }
 
@@ -323,7 +322,8 @@ mod tests {
     use std::time::Instant;
 
     use sandbox_driver::{
-        OutputSink, OutputStream, SandboxProvider as _, SandboxSource, SandboxSpec, TransportError,
+        BASH_ENV_VAR, OutputSink, OutputStream, SandboxProvider as _, SandboxSource, SandboxSpec,
+        TransportError,
     };
     use sandbox_driver_host::HostProvider;
     use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
diff --git a/lib/components/fabro-sandbox/src/test_support.rs b/lib/components/fabro-sandbox/src/test_support.rs
index 2f3e3f670..67f2d9d09 100644
--- a/lib/components/fabro-sandbox/src/test_support.rs
+++ b/lib/components/fabro-sandbox/src/test_support.rs
@@ -280,12 +280,10 @@ impl MockSandbox {
     }
 
     /// The explicit variables of the last command as the caller passed them.
-    /// The exec policy's own `BASH_ENV` blank is not the caller's.
     pub fn captured_env_vars(&self) -> Option<HashMap<String, String>> {
         self.recorded().last().map(|spec| {
             spec.env
                 .iter()
-                .filter(|(key, _)| key.as_str() != sandbox_driver::BASH_ENV_VAR)
                 .map(|(k, v)| (k.clone(), v.clone()))
                 .collect()
         })