diff --git a/docs/usage/config.md b/docs/usage/config.md
index 4289c48..9f08d29 100644
--- a/docs/usage/config.md
+++ b/docs/usage/config.md
@@ -34,6 +34,7 @@ All keys are optional.
 | `sign_with` | enum | `auto` | Where `debsign` runs (see below). |
 | `sign_key` | string | — | GPG key ID/email for `debsign -k`. Required for container signing. |
 | `clean` | bool | `false` | Run `debian/rules clean` before building. Disabled by default; incompatible with `incremental`. |
+| `shell_on_failure` | bool | `false` | On build or test failure, drop into an interactive shell in the environment when stdout is a TTY. |
 
 ### `source_sync_mode`
 
diff --git a/packages/debmagic/src/build_intent.rs b/packages/debmagic/src/build_intent.rs
index 533867b..088bab6 100644
--- a/packages/debmagic/src/build_intent.rs
+++ b/packages/debmagic/src/build_intent.rs
@@ -30,7 +30,7 @@ pub struct BuildIntentInput {
     pub clean: Option<bool>,
     pub no_clean: Option<bool>,
     pub source_sync: Option<SourceSyncMode>,
-    pub shell_on_failure: bool,
+    pub shell_on_failure: Option<bool>,
     pub driver_overrides: DriverOverrides,
 }
 
@@ -124,11 +124,13 @@ pub fn resolve_build_intent(input: BuildIntentInput) -> anyhow::Result<BuildInte
         config.driver.persistent = true;
     }
 
+    let shell_on_failure = input.shell_on_failure.unwrap_or(config.shell_on_failure);
+
     Ok(BuildIntent {
         source_dir,
         output_dir,
         driver: input.driver,
-        shell_on_failure: input.shell_on_failure,
+        shell_on_failure,
         config,
         driver_overrides: input.driver_overrides,
     })
@@ -167,7 +169,7 @@ mod tests {
             clean: None,
             no_clean: None,
             source_sync: None,
-            shell_on_failure: false,
+            shell_on_failure: None,
             driver_overrides: DriverOverrides {
                 apt_mirror: None,
                 proposed: None,
@@ -223,10 +225,30 @@ mod tests {
     fn resolve_passes_through_shell_on_failure() -> anyhow::Result<()> {
         let dir = std::env::temp_dir();
         let mut input = base_input(dir);
-        input.shell_on_failure = true;
+        input.shell_on_failure = Some(true);
+
+        let intent = resolve_build_intent(input)?;
+        assert!(intent.shell_on_failure);
+        Ok(())
+    }
+
+    #[test]
+    fn resolve_shell_on_failure_from_config() -> anyhow::Result<()> {
+        let dir = std::env::temp_dir();
+        let mut input = base_input(dir);
+        input.config_file = None;
+        input.shell_on_failure = None;
+
+        let config_path = std::env::temp_dir().join(format!(
+            "debmagic-shell-on-failure-{}.toml",
+            std::process::id()
+        ));
+        std::fs::write(&config_path, "shell_on_failure = true\n")?;
+        input.config_file = Some(config_path.clone());
 
         let intent = resolve_build_intent(input)?;
         assert!(intent.shell_on_failure);
+        std::fs::remove_file(config_path)?;
         Ok(())
     }
 
diff --git a/packages/debmagic/src/cli.rs b/packages/debmagic/src/cli.rs
index 5d20c5b..b083823 100644
--- a/packages/debmagic/src/cli.rs
+++ b/packages/debmagic/src/cli.rs
@@ -151,9 +151,9 @@ pub struct CommonBuildArgs {
     #[arg(
         long = "shell-on-failure",
         action = clap::ArgAction::SetTrue,
-        help = "On build failure, drop into an interactive shell in the build environment when stdout is a TTY"
+        help = "On build failure, drop into an interactive shell in the build environment when stdout is a TTY. Defaults to the 'shell_on_failure' setting in the config file (false if unset)."
     )]
-    pub shell_on_failure: bool,
+    pub shell_on_failure: Option<bool>,
 
     #[command(flatten)]
     pub common: CommonCli,
@@ -266,9 +266,9 @@ pub struct TestSubcommandArgs {
     #[arg(
         long = "shell-on-failure",
         action = clap::ArgAction::SetTrue,
-        help = "On test failure, drop into an interactive shell in the test environment when stdout is a TTY"
+        help = "On test failure, drop into an interactive shell in the test environment when stdout is a TTY. Defaults to the 'shell_on_failure' setting in the config file (false if unset)."
     )]
-    pub shell_on_failure: bool,
+    pub shell_on_failure: Option<bool>,
 
     #[command(flatten)]
     pub common: CommonCli,
diff --git a/packages/debmagic/src/config.rs b/packages/debmagic/src/config.rs
index 8db86e5..9b6fc4b 100644
--- a/packages/debmagic/src/config.rs
+++ b/packages/debmagic/src/config.rs
@@ -32,6 +32,9 @@ pub struct Config {
     /// builds already stage a clean source tree and incremental builds preserve
     /// outputs intentionally.
     pub clean: bool,
+    /// On build or test failure, drop into an interactive shell in the
+    /// environment when stdout is a TTY.
+    pub shell_on_failure: bool,
 }
 
 impl Default for Config {
@@ -46,6 +49,7 @@ impl Default for Config {
             sign_with: SignWith::default(),
             sign_key: None,
             clean: false,
+            shell_on_failure: false,
         }
     }
 }
diff --git a/packages/debmagic/src/test/intent.rs b/packages/debmagic/src/test/intent.rs
index 7cb486f..1cd7688 100644
--- a/packages/debmagic/src/test/intent.rs
+++ b/packages/debmagic/src/test/intent.rs
@@ -20,7 +20,7 @@ pub struct TestIntentInput {
     pub strict: bool,
     pub changes: Option<PathBuf>,
     pub allow_host_test: bool,
-    pub shell_on_failure: bool,
+    pub shell_on_failure: Option<bool>,
     pub distro: Option<String>,
     pub driver_overrides: DriverOverrides,
 }
@@ -57,13 +57,15 @@ pub fn resolve_test_intent(input: TestIntentInput) -> anyhow::Result<TestIntent>
         None
     };
 
+    let shell_on_failure = input.shell_on_failure.unwrap_or(config.shell_on_failure);
+
     Ok(TestIntent {
         source_dir,
         driver: input.driver,
         strict: input.strict,
         changes,
         allow_host_test: input.allow_host_test,
-        shell_on_failure: input.shell_on_failure,
+        shell_on_failure,
         distro: input.distro,
         config,
         driver_overrides: input.driver_overrides,
@@ -95,7 +97,7 @@ mod tests {
             strict: false,
             changes: None,
             allow_host_test: false,
-            shell_on_failure: false,
+            shell_on_failure: None,
             distro: None,
             driver_overrides: DriverOverrides {
                 apt_mirror: None,
@@ -136,7 +138,7 @@ mod tests {
     fn resolve_passes_through_shell_on_failure() -> anyhow::Result<()> {
         let dir = std::env::temp_dir();
         let mut input = base_input(dir);
-        input.shell_on_failure = true;
+        input.shell_on_failure = Some(true);
 
         let intent = resolve_test_intent(input)?;
         assert!(intent.shell_on_failure);