fix(cmd/gc): wire ConfigDir into the prompt render context

cmd/gc/cmd_lint.go

@@ -436,6 +436,7 @@ func lintPromptContext(packDir string, agentCfg config.Agent, providers map[stri
 		SlingQuery:              agentCfg.EffectiveSlingQuery(),
 		ProviderKey:             providerKey,
 		ProviderDisplayName:     providerDisplayNameFor(providerKey, providers),
+		ConfigDir:               promptConfigDir(packDir, agentCfg.SourceDir),
 		Env:                     env,
 	}
 }

cmd/gc/cmd_prime.go

@@ -765,6 +765,7 @@ func buildPrimeContextForBeads(cityPath, cityName string, a *config.Agent, rigs
 		TemplateName:  a.Name,
 		BindingName:   a.BindingName,
 		BindingPrefix: a.BindingPrefix(),
+		ConfigDir:     promptConfigDir(cityPath, a.SourceDir),
 		Env:           a.Env,
 	}
 

cmd/gc/prompt.go

@@ -57,7 +57,26 @@ type PromptContext struct {
 	// Templates use {{ .InstructionsFile }} as a provider-aware fallback when
 	// pack-specific guidance (e.g. quality-gate commands) is missing or empty.
 	InstructionsFile string
-	Env              map[string]string // from Agent.Env — custom vars
+	// ConfigDir is the directory this agent's config was defined in — the pack
+	// directory for a pack-supplied agent, the city root otherwise. Prompts use
+	// {{ .ConfigDir }} to reach assets the pack ships alongside the agent, most
+	// often helper scripts under {{ .ConfigDir }}/assets/scripts/. It carries the
+	// same value SessionSetupContext carries for command / pre_start /
+	// session_live expansion, so the variable means the same thing in a prompt as
+	// it does in a session-setup command.
+	ConfigDir string
+	Env       map[string]string // from Agent.Env — custom vars
+}
+
+// promptConfigDir resolves the ConfigDir for a prompt: the directory the agent's
+// config was defined in, falling back to the city root when the agent is defined
+// by the city itself rather than by an imported pack. Mirrors the fallback
+// resolveTemplate applies when building SessionSetupContext.
+func promptConfigDir(cityPath, sourceDir string) string {
+	if sourceDir != "" {
+		return sourceDir
+	}
+	return cityPath
 }
 
 // PromptRenderResult holds the rendered text plus the version and rendered
@@ -340,6 +359,7 @@ func buildTemplateData(ctx PromptContext) map[string]string {
 	m["ProviderKey"] = ctx.ProviderKey
 	m["ProviderDisplayName"] = ctx.ProviderDisplayName
 	m["InstructionsFile"] = ctx.InstructionsFile
+	m["ConfigDir"] = ctx.ConfigDir
 	return m
 }
 

cmd/gc/prompt_test.go

@@ -324,6 +324,53 @@ func TestRenderPromptEnvMerge(t *testing.T) {
 	}
 }
 
+// TestRenderPromptConfigDir covers the shape that regressed: a pack ships helper
+// scripts under assets/scripts/ and its prompts reach them via {{ .ConfigDir }}.
+// Before ConfigDir was wired into the prompt context, the key was absent from the
+// template data map and missingkey=zero rendered it as "", turning every such
+// invocation into a bare /assets/scripts/... path that exits 127.
+func TestRenderPromptConfigDir(t *testing.T) {
+	f := fsys.NewFake()
+	f.Files["/city/prompts/test.template.md"] = []byte("{{ .ConfigDir }}/assets/scripts/slack.py send hi")
+	ctx := PromptContext{
+		CityRoot:  "/home/user/my-city",
+		ConfigDir: "/home/user/packs/local-core",
+	}
+	got := renderPrompt(f, "/city", "", "prompts/test.template.md", ctx, "", io.Discard, nil, nil, nil)
+	want := "/home/user/packs/local-core/assets/scripts/slack.py send hi"
+	if got != want {
+		t.Errorf("renderPrompt(ConfigDir) = %q, want %q", got, want)
+	}
+}
+
+func TestPromptConfigDir(t *testing.T) {
+	tests := []struct {
+		name      string
+		cityPath  string
+		sourceDir string
+		want      string
+	}{
+		{
+			name:      "pack-supplied agent uses its pack dir",
+			cityPath:  "/home/user/my-city",
+			sourceDir: "/home/user/packs/local-core",
+			want:      "/home/user/packs/local-core",
+		},
+		{
+			name:     "city-defined agent falls back to the city root",
+			cityPath: "/home/user/my-city",
+			want:     "/home/user/my-city",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := promptConfigDir(tt.cityPath, tt.sourceDir); got != tt.want {
+				t.Errorf("promptConfigDir(%q, %q) = %q, want %q", tt.cityPath, tt.sourceDir, got, tt.want)
+			}
+		})
+	}
+}
+
 func TestRenderPromptDefaultBranch(t *testing.T) {
 	f := fsys.NewFake()
 	f.Files["/city/prompts/test.md.tmpl"] = []byte("Branch: {{ .DefaultBranch }}")

cmd/gc/template_resolve.go

@@ -369,6 +369,7 @@ func resolveTemplate(p *agentBuildParams, cfgAgent *config.Agent, qualifiedName
 		ProviderKey:             providerKey,
 		ProviderDisplayName:     providerDisplayName,
 		InstructionsFile:        instructionsFileForAgent(cfgAgent, p.workspace, p.providers),
+		ConfigDir:               promptConfigDir(p.cityPath, cfgAgent.SourceDir),
 		Env:                     cfgAgent.Env,
 	}, p.sessionTemplate, p.stderr, packDirs, fragments, p.beadStore)
 	hasHooks := config.AgentHasHooks(cfgAgent, p.workspace, resolved.Name, p.providers)
@@ -499,11 +500,10 @@ func resolveTemplate(p *agentBuildParams, cfgAgent *config.Agent, qualifiedName
 	// re-enable product metrics; Beads telemetry remains independent.
 	env[execenv.UsageMetricsDisableEnv] = execenv.UsageMetricsDisableValue
 
-	// Step 11: Expand session setup templates.
-	configDir := p.cityPath
-	if cfgAgent.SourceDir != "" {
-		configDir = cfgAgent.SourceDir
-	}
+	// Step 11: Expand session setup templates. ConfigDir comes from the same
+	// helper the prompt context uses, so {{.ConfigDir}} resolves identically in a
+	// prompt and in a session-setup command and the two scopes cannot drift.
+	configDir := promptConfigDir(p.cityPath, cfgAgent.SourceDir)
 	setupCtx := SessionSetupContext{
 		Session:   sessName,
 		Agent:     qualifiedName,