diff --git a/scripts/core-boundaries/rules/source/required-rules.mjs b/scripts/core-boundaries/rules/source/required-rules.mjs
index 434d377b4..a5a78d79d 100644
--- a/scripts/core-boundaries/rules/source/required-rules.mjs
+++ b/scripts/core-boundaries/rules/source/required-rules.mjs
@@ -2994,8 +2994,12 @@ export const requiredContentRules = [
         message: 'missing delegation policy parsing owner',
       },
       {
-        regex: /\bpub fn primary_model_supports_image_understanding\b/,
-        message: 'missing model image-support policy owner',
+        regex: /\bpub struct PrimaryModelFacts\b/,
+        message: 'missing typed primary model facts owner',
+      },
+      {
+        regex: /\bpub fn multimodal_tool_output_supported\b/,
+        message: 'missing primary model multimodal tool-output policy owner',
       },
       {
         regex: /\bmaterializes_provider_neutral_tool_custom_data\b/,
diff --git a/src/crates/assembly/core/src/agentic/execution/execution_engine.rs b/src/crates/assembly/core/src/agentic/execution/execution_engine.rs
index f14794b51..fdf6cd96a 100644
--- a/src/crates/assembly/core/src/agentic/execution/execution_engine.rs
+++ b/src/crates/assembly/core/src/agentic/execution/execution_engine.rs
@@ -51,6 +51,7 @@ use std::collections::{HashMap, HashSet};
 use std::path::Path;
 use std::sync::Arc;
 use tokio_util::sync::CancellationToken;
+use tool_runtime::context::PrimaryModelFacts;
 
 /// Execution engine configuration
 #[derive(Debug, Clone)]
@@ -658,9 +659,9 @@ impl ExecutionEngine {
     async fn resolve_primary_model_context(
         model_id: &str,
         ai_client_model: &str,
-        ai_client_provider: &str,
+        ai_client_api_format: &str,
         unavailable_log_message: &str,
-    ) -> (String, bool) {
+    ) -> PrimaryModelFacts {
         let config_service = get_global_config_service().await.ok();
         if let Some(service) = config_service {
             let ai_config: crate::service::config::types::AIConfig =
@@ -680,7 +681,7 @@ impl ExecutionEngine {
                 })
                 .or_else(|| {
                     ai_config.models.iter().find(|m| {
-                        m.model_name == ai_client_model && m.provider == ai_client_provider
+                        m.model_name == ai_client_model && m.provider == ai_client_api_format
                     })
                 });
 
@@ -691,10 +692,10 @@ impl ExecutionEngine {
                     || matches!(m.category, ModelCategory::Multimodal)
             });
 
-            (resolved_id, supports)
+            PrimaryModelFacts::new(resolved_id, ai_client_model, ai_client_api_format, supports)
         } else {
             warn!("{}", unavailable_log_message);
-            (model_id.to_string(), false)
+            PrimaryModelFacts::new(model_id, ai_client_model, ai_client_api_format, false)
         }
     }
 
@@ -1116,7 +1117,7 @@ impl ExecutionEngine {
         round_number: usize,
         round_group_id: Option<String>,
         execution_context_vars: &HashMap<String, String>,
-        primary_supports_image_understanding: bool,
+        primary_model_facts: &PrimaryModelFacts,
         prepended_reminders: &[&str],
         messages: &[Message],
         reminder_text: &str,
@@ -1139,7 +1140,7 @@ impl ExecutionEngine {
                 .as_ref()
                 .map(|workspace| workspace.root_path()),
             &context.dialog_turn_id,
-            primary_supports_image_understanding,
+            primary_model_facts.supports_image_inputs,
             prepended_reminders,
         )
         .await?;
@@ -1159,6 +1160,7 @@ impl ExecutionEngine {
             collapsed_tools: Vec::new(),
             unlocked_collapsed_tools: Vec::new(),
             model_name: ai_client.config.model.clone(),
+            primary_model_facts: primary_model_facts.clone(),
             agent_type,
             context_vars: execution_context_vars.clone(),
             delegation_policy: context.delegation_policy,
@@ -1570,14 +1572,15 @@ impl ExecutionEngine {
                 ))
             })?;
 
-        let (resolved_primary_model_id, primary_supports_image_understanding) =
-            Self::resolve_primary_model_context(
-                &model_id,
-                &ai_client.config.model,
-                &ai_client.config.format,
-                "Config service unavailable, assuming compression model is text-only for image input gating",
-            )
-            .await;
+        let primary_model_facts = Self::resolve_primary_model_context(
+            &model_id,
+            &ai_client.config.model,
+            &ai_client.config.format,
+            "Config service unavailable, assuming compression model is text-only for image input gating",
+        )
+        .await;
+        let resolved_primary_model_id = primary_model_facts.model_id.clone();
+        let primary_supports_image_understanding = primary_model_facts.supports_image_inputs;
 
         let model_capability_profile = ModelCapabilityProfile::from_resolved_model(
             &resolved_primary_model_id,
@@ -1613,10 +1616,7 @@ impl ExecutionEngine {
             &context.agent_type,
             context.workspace.as_ref(),
             context.workspace_services.as_ref(),
-            Some(&resolved_primary_model_id),
-            Some(&ai_client.config.model),
-            Some(&ai_client.config.format),
-            primary_supports_image_understanding,
+            Some(&primary_model_facts),
             &tool_manifest_context_vars,
         );
         let tool_manifest = if enable_tools {
@@ -2212,14 +2212,15 @@ impl ExecutionEngine {
             })?;
 
         // Primary model vision capability (tools + system prompt appendix; also used below for API message stripping).
-        let (resolved_primary_model_id, primary_supports_image_understanding) =
-            Self::resolve_primary_model_context(
-                &model_id,
-                &ai_client.config.model,
-                &ai_client.config.format,
-                "Config service unavailable, assuming primary model is text-only for image input gating",
-            )
-            .await;
+        let primary_model_facts = Self::resolve_primary_model_context(
+            &model_id,
+            &ai_client.config.model,
+            &ai_client.config.format,
+            "Config service unavailable, assuming primary model is text-only for image input gating",
+        )
+        .await;
+        let resolved_primary_model_id = primary_model_facts.model_id.clone();
+        let primary_supports_image_understanding = primary_model_facts.supports_image_inputs;
 
         let model_context_window = ai_client.config.context_window as usize;
         let session_max_tokens = session.config.max_context_tokens;
@@ -2277,10 +2278,7 @@ impl ExecutionEngine {
             &agent_type,
             context.workspace.as_ref(),
             context.workspace_services.as_ref(),
-            Some(&resolved_primary_model_id),
-            Some(&ai_client.config.model),
-            Some(&ai_client.config.format),
-            primary_supports_image_understanding,
+            Some(&primary_model_facts),
             &tool_manifest_context_vars,
         );
 
@@ -2334,6 +2332,18 @@ impl ExecutionEngine {
         } else {
             (vec![], None)
         };
+        let final_tool_names = Self::finalize_tool_names(tool_definitions.as_deref());
+        debug!(
+            "Primary model and tool manifest resolved: session_id={}, turn_id={}, resolved_primary_model_id={}, primary_model_api_format={}, primary_model_supports_image_inputs={}, final_tool_count={}, final_tool_names={:?}, collapsed_tool_names={:?}",
+            context.session_id,
+            context.dialog_turn_id,
+            primary_model_facts.model_id,
+            primary_model_facts.api_format,
+            primary_model_facts.supports_image_inputs,
+            final_tool_names.len(),
+            final_tool_names,
+            collapsed_tools,
+        );
 
         // 4. Resolve the prompt scaffold used by model requests in this turn.
         // It is refreshed after successful context compression so the first
@@ -2403,22 +2413,6 @@ impl ExecutionEngine {
         let compression_threshold = session.config.compression_threshold;
 
         let mut execution_context_vars = context.context.clone();
-        execution_context_vars.insert(
-            "primary_model_id".to_string(),
-            resolved_primary_model_id.clone(),
-        );
-        execution_context_vars.insert(
-            "primary_model_name".to_string(),
-            ai_client.config.model.clone(),
-        );
-        execution_context_vars.insert(
-            "primary_model_provider".to_string(),
-            ai_client.config.format.clone(),
-        );
-        execution_context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            primary_supports_image_understanding.to_string(),
-        );
         execution_context_vars.insert("turn_index".to_string(), context.turn_index.to_string());
 
         // If the primary model is text-only, do not send image payloads to the provider.
@@ -2632,6 +2626,7 @@ impl ExecutionEngine {
                 collapsed_tools: collapsed_tools.clone(),
                 unlocked_collapsed_tools,
                 model_name: ai_client.config.model.clone(),
+                primary_model_facts: primary_model_facts.clone(),
                 agent_type: agent_type.clone(),
                 context_vars: round_context_vars,
                 delegation_policy: context.delegation_policy,
@@ -3120,7 +3115,7 @@ impl ExecutionEngine {
                         completed_rounds,
                         finalize_round_group_id.clone(),
                         &execution_context_vars,
-                        primary_supports_image_understanding,
+                        &primary_model_facts,
                         &finalize_prepended_reminders,
                         &messages,
                         finalize_reminder,
@@ -3150,7 +3145,7 @@ impl ExecutionEngine {
                             completed_rounds,
                             finalize_round_group_id.clone(),
                             &execution_context_vars,
-                            primary_supports_image_understanding,
+                            &primary_model_facts,
                             &finalize_prepended_reminders,
                             &messages,
                             finalize_reminder,
diff --git a/src/crates/assembly/core/src/agentic/execution/round_executor.rs b/src/crates/assembly/core/src/agentic/execution/round_executor.rs
index 5bef81b3e..6f24fc2c8 100644
--- a/src/crates/assembly/core/src/agentic/execution/round_executor.rs
+++ b/src/crates/assembly/core/src/agentic/execution/round_executor.rs
@@ -721,6 +721,7 @@ impl RoundExecutor {
                 attempt_index: Some((attempt_index + 1) as u32),
                 agent_type: context.agent_type.clone(),
                 workspace: context.workspace.clone(),
+                primary_model_facts: context.primary_model_facts.clone(),
                 context_vars: context.context_vars.clone(),
                 subagent_parent_info,
                 delegation_policy: context.delegation_policy,
@@ -1345,6 +1346,9 @@ mod tests {
             collapsed_tools: Vec::new(),
             unlocked_collapsed_tools: Vec::new(),
             model_name: "model-1".to_string(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::new(
+                "model-1", "model-1", "openai", true,
+            ),
             agent_type: "agentic".to_string(),
             context_vars: HashMap::new(),
             delegation_policy: DelegationPolicy::top_level(),
diff --git a/src/crates/assembly/core/src/agentic/execution/types.rs b/src/crates/assembly/core/src/agentic/execution/types.rs
index aa051346e..627e48880 100644
--- a/src/crates/assembly/core/src/agentic/execution/types.rs
+++ b/src/crates/assembly/core/src/agentic/execution/types.rs
@@ -12,6 +12,7 @@ use serde_json::Value;
 use std::collections::HashMap;
 use std::sync::Arc;
 use tokio_util::sync::CancellationToken;
+use tool_runtime::context::PrimaryModelFacts;
 
 /// Execution context
 #[derive(Clone)]
@@ -51,6 +52,7 @@ pub struct RoundContext {
     pub collapsed_tools: Vec<String>,
     pub unlocked_collapsed_tools: Vec<String>,
     pub model_name: String,
+    pub primary_model_facts: PrimaryModelFacts,
     pub agent_type: String,
     pub context_vars: HashMap<String, String>,
     pub(crate) delegation_policy: DelegationPolicy,
diff --git a/src/crates/assembly/core/src/agentic/skill_agent_snapshot.rs b/src/crates/assembly/core/src/agentic/skill_agent_snapshot.rs
index 713b3bc84..0742723e5 100644
--- a/src/crates/assembly/core/src/agentic/skill_agent_snapshot.rs
+++ b/src/crates/assembly/core/src/agentic/skill_agent_snapshot.rs
@@ -52,9 +52,6 @@ pub async fn resolve_skill_agent_snapshot(
         workspace,
         workspace_services,
         None,
-        None,
-        None,
-        true,
         context_vars,
     );
     let manifest = resolve_tool_manifest(
diff --git a/src/crates/assembly/core/src/agentic/tools/file_read_state_runtime.rs b/src/crates/assembly/core/src/agentic/tools/file_read_state_runtime.rs
index 261900bd6..aa7394ada 100644
--- a/src/crates/assembly/core/src/agentic/tools/file_read_state_runtime.rs
+++ b/src/crates/assembly/core/src/agentic/tools/file_read_state_runtime.rs
@@ -268,6 +268,7 @@ mod tests {
             dialog_turn_id: Some("turn-1".to_string()),
             workspace: Some(WorkspaceBinding::new(None, root)),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/ask_user_question_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/ask_user_question_tool.rs
index 0874c87e8..a9ae9b65f 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/ask_user_question_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/ask_user_question_tool.rs
@@ -267,6 +267,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data,
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/code_review_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/code_review_tool.rs
index 0018db7ee..ddac133c0 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/code_review_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/code_review_tool.rs
@@ -713,6 +713,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/computer_use_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/computer_use_tool.rs
index 6eb25e378..e4601a785 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/computer_use_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/computer_use_tool.rs
@@ -448,14 +448,6 @@ The **primary model cannot consume images** in tool results — **do not** use *
         Ok(vec![ToolResult::ok(body, Some(hint.to_string()))])
     }
 
-    fn primary_api_format(ctx: &ToolUseContext) -> String {
-        ctx.custom_data
-            .get("primary_model_provider")
-            .and_then(|v| v.as_str())
-            .unwrap_or("")
-            .to_lowercase()
-    }
-
     /// Screenshot tool results attach JPEGs via `tool_image_attachments`; only providers whose
     /// request converters emit multimodal tool output are supported (Anthropic + OpenAI-compatible).
     fn require_multimodal_tool_output_for_screenshot(ctx: &ToolUseContext) -> BitFunResult<()> {
@@ -464,11 +456,7 @@ The **primary model cannot consume images** in tool results — **do not** use *
                 "The primary model does not accept images; do not use ComputerUse action `screenshot` or other image-producing steps. Use `click_element`, `locate`, `move_to_text` (with `move_to_text_match_index` when listed), `mouse_move` with globals from tool JSON, `key_chord`, etc.".to_string(),
             ));
         }
-        let f = Self::primary_api_format(ctx);
-        if matches!(
-            f.as_str(),
-            "anthropic" | "openai" | "response" | "responses"
-        ) {
+        if ctx.primary_model_facts().multimodal_tool_output_supported() {
             return Ok(());
         }
         Err(BitFunError::tool(
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/control_hub_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/control_hub_tool.rs
index cef1f09c5..8386344cf 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/control_hub_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/control_hub_tool.rs
@@ -2066,6 +2066,7 @@ mod control_hub_tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: std::collections::HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/cron_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/cron_tool.rs
index 7f2fc7682..1604d8916 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/cron_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/cron_tool.rs
@@ -1207,6 +1207,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/exec_command/command.rs b/src/crates/assembly/core/src/agentic/tools/implementations/exec_command/command.rs
index e15209172..3bb548f60 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/exec_command/command.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/exec_command/command.rs
@@ -1130,6 +1130,7 @@ mod tests {
                 session_identity,
             )),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/file_write_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/file_write_tool.rs
index e05d80b48..099b3d985 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/file_write_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/file_write_tool.rs
@@ -244,6 +244,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: Some(WorkspaceBinding::new(None, root)),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/get_time_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/get_time_tool.rs
index 2c371beaf..65c7f489c 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/get_time_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/get_time_tool.rs
@@ -124,6 +124,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/session_control_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/session_control_tool.rs
index ead63e15e..23b02ae3e 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/session_control_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/session_control_tool.rs
@@ -559,6 +559,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/session_message_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/session_message_tool.rs
index d28fde7a2..b5eef9e78 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/session_message_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/session_message_tool.rs
@@ -626,6 +626,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/skill_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/skill_tool.rs
index 7f29977a2..ecc28a8d6 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/skill_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/skill_tool.rs
@@ -408,6 +408,7 @@ Use the remote project skill.
             dialog_turn_id: None,
             workspace: Some(workspace),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: Default::default(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
@@ -449,6 +450,7 @@ Use the remote project skill.
             dialog_turn_id: None,
             workspace: Some(workspace),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: Default::default(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
@@ -496,6 +498,7 @@ Use the remote project skill.
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: Default::default(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/task_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/task_tool.rs
index b53e8ed8e..c6b9a70ac 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/task_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/task_tool.rs
@@ -1738,6 +1738,7 @@ mod tests {
             dialog_turn_id: Some("turn-1".to_string()),
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::from([
                 (
                     "delegation_allow_subagent_spawn".to_string(),
@@ -1877,6 +1878,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -1912,6 +1914,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/view_image_tool.rs b/src/crates/assembly/core/src/agentic/tools/implementations/view_image_tool.rs
index 8a0ec7963..ded1fe8f5 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/view_image_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/view_image_tool.rs
@@ -39,11 +39,7 @@ impl ViewImageTool {
     }
 
     fn primary_api_format(ctx: &ToolUseContext) -> String {
-        ctx.custom_data
-            .get("primary_model_provider")
-            .and_then(|v| v.as_str())
-            .unwrap_or("")
-            .to_lowercase()
+        ctx.primary_model_facts().api_format.to_lowercase()
     }
 
     fn require_multimodal_tool_output(ctx: &ToolUseContext) -> BitFunResult<()> {
@@ -70,10 +66,7 @@ impl ViewImageTool {
 
     fn supports_multimodal_tool_output(ctx: &ToolUseContext) -> bool {
         ctx.primary_model_supports_image_understanding()
-            && matches!(
-                Self::primary_api_format(ctx).as_str(),
-                "anthropic" | "openai" | "response" | "responses"
-            )
+            && ctx.primary_model_facts().multimodal_tool_output_supported()
     }
 
     fn mime_type_for_image(bytes: &[u8]) -> BitFunResult<&'static str> {
@@ -454,6 +447,7 @@ mod tests {
     use std::io::Cursor;
     use std::path::PathBuf;
     use std::sync::Arc;
+    use tool_runtime::context::PrimaryModelFacts;
 
     fn png_bytes(width: u32, height: u32) -> Vec<u8> {
         let image = ImageBuffer::from_pixel(width, height, Rgb([80u8, 120u8, 160u8]));
@@ -520,12 +514,8 @@ mod tests {
     }
 
     fn context(provider: &str, supports_images: bool) -> ToolUseContext {
-        let mut custom_data = HashMap::new();
-        custom_data.insert("primary_model_provider".to_string(), json!(provider));
-        custom_data.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            json!(supports_images),
-        );
+        let primary_model_facts =
+            PrimaryModelFacts::new("primary-model", "vision-model", provider, supports_images);
         ToolUseContext {
             tool_call_id: None,
             agent_type: None,
@@ -533,7 +523,8 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
-            custom_data,
+            primary_model_facts,
+            custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
             runtime_handles: bitfun_runtime_ports::ToolRuntimeHandles::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/implementations/web/mod.rs b/src/crates/assembly/core/src/agentic/tools/implementations/web/mod.rs
index 1f1b6f5db..d2bfb05c5 100644
--- a/src/crates/assembly/core/src/agentic/tools/implementations/web/mod.rs
+++ b/src/crates/assembly/core/src/agentic/tools/implementations/web/mod.rs
@@ -29,6 +29,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: std::collections::HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: Default::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/manifest_resolver.rs b/src/crates/assembly/core/src/agentic/tools/manifest_resolver.rs
index 218b59642..7d1a28f8e 100644
--- a/src/crates/assembly/core/src/agentic/tools/manifest_resolver.rs
+++ b/src/crates/assembly/core/src/agentic/tools/manifest_resolver.rs
@@ -44,6 +44,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/pipeline/state_manager.rs b/src/crates/assembly/core/src/agentic/tools/pipeline/state_manager.rs
index 03a892592..1041ffeb7 100644
--- a/src/crates/assembly/core/src/agentic/tools/pipeline/state_manager.rs
+++ b/src/crates/assembly/core/src/agentic/tools/pipeline/state_manager.rs
@@ -299,6 +299,7 @@ mod tests {
                 attempt_index: None,
                 agent_type: "agentic".to_string(),
                 workspace: None,
+                primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
                 context_vars: HashMap::new(),
                 subagent_parent_info: None,
                 delegation_policy: bitfun_runtime_ports::DelegationPolicy::top_level(),
diff --git a/src/crates/assembly/core/src/agentic/tools/pipeline/tool_pipeline.rs b/src/crates/assembly/core/src/agentic/tools/pipeline/tool_pipeline.rs
index eb2bd7b08..34e2fcefa 100644
--- a/src/crates/assembly/core/src/agentic/tools/pipeline/tool_pipeline.rs
+++ b/src/crates/assembly/core/src/agentic/tools/pipeline/tool_pipeline.rs
@@ -1439,6 +1439,7 @@ mod tests {
             attempt_index: None,
             agent_type: "agent".to_string(),
             workspace: None,
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             context_vars: HashMap::new(),
             subagent_parent_info: None,
             delegation_policy: bitfun_runtime_ports::DelegationPolicy::top_level(),
@@ -1807,13 +1808,6 @@ mod tests {
         task.context
             .context_vars
             .insert("turn_index".to_string(), "7".to_string());
-        task.context
-            .context_vars
-            .insert("primary_model_provider".to_string(), "openai".to_string());
-        task.context.context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "true".to_string(),
-        );
         task.context
             .context_vars
             .insert("acp_transport".to_string(), "true".to_string());
@@ -1839,14 +1833,10 @@ mod tests {
             .is_tool_allowed("WebFetch"));
         assert!(!context.runtime_tool_restrictions.is_tool_allowed("Bash"));
         assert_eq!(context.custom_data["turn_index"], json!(7));
-        assert_eq!(
-            context.custom_data["primary_model_provider"],
-            json!("openai")
-        );
-        assert_eq!(
-            context.custom_data["primary_model_supports_image_understanding"],
-            json!(true)
-        );
+        assert!(!context.custom_data.contains_key("primary_model_provider"));
+        assert!(!context
+            .custom_data
+            .contains_key("primary_model_supports_image_understanding"));
         assert_eq!(context.custom_data["acp_transport"], json!(true));
 
         let facts = context.to_tool_context_facts();
diff --git a/src/crates/assembly/core/src/agentic/tools/pipeline/types.rs b/src/crates/assembly/core/src/agentic/tools/pipeline/types.rs
index 1e9848e68..7c770f8ae 100644
--- a/src/crates/assembly/core/src/agentic/tools/pipeline/types.rs
+++ b/src/crates/assembly/core/src/agentic/tools/pipeline/types.rs
@@ -9,6 +9,7 @@ use crate::agentic::WorkspaceBinding;
 use bitfun_runtime_ports::DelegationPolicy;
 use std::collections::HashMap;
 use std::time::SystemTime;
+pub use tool_runtime::context::PrimaryModelFacts;
 pub use tool_runtime::pipeline::SubagentBatchExecutionPolicy;
 
 /// Tool execution options
@@ -64,6 +65,7 @@ pub struct ToolExecutionContext {
     pub attempt_index: Option<u32>,
     pub agent_type: String,
     pub workspace: Option<WorkspaceBinding>,
+    pub primary_model_facts: PrimaryModelFacts,
     pub context_vars: HashMap<String, String>,
     pub subagent_parent_info: Option<SubagentParentInfo>,
     pub(crate) delegation_policy: DelegationPolicy,
diff --git a/src/crates/assembly/core/src/agentic/tools/product_runtime/catalog.rs b/src/crates/assembly/core/src/agentic/tools/product_runtime/catalog.rs
index 6390279bd..74146738a 100644
--- a/src/crates/assembly/core/src/agentic/tools/product_runtime/catalog.rs
+++ b/src/crates/assembly/core/src/agentic/tools/product_runtime/catalog.rs
@@ -232,6 +232,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -241,13 +242,8 @@ mod tests {
 
     fn multimodal_anthropic_tool_context(agent_type: Option<&str>) -> ToolUseContext {
         let mut context = tool_context(agent_type);
-        context.custom_data.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            json!(true),
-        );
-        context
-            .custom_data
-            .insert("primary_model_provider".to_string(), json!("anthropic"));
+        context.primary_model_facts =
+            tool_runtime::context::PrimaryModelFacts::new("model-1", "claude", "anthropic", true);
         context
     }
 
diff --git a/src/crates/assembly/core/src/agentic/tools/product_runtime/get_tool_spec_tool.rs b/src/crates/assembly/core/src/agentic/tools/product_runtime/get_tool_spec_tool.rs
index ca019c642..e3cd64978 100644
--- a/src/crates/assembly/core/src/agentic/tools/product_runtime/get_tool_spec_tool.rs
+++ b/src/crates/assembly/core/src/agentic/tools/product_runtime/get_tool_spec_tool.rs
@@ -140,6 +140,7 @@ mod tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: vec!["WebFetch".to_string()],
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/assembly/core/src/agentic/tools/tool_context_runtime.rs b/src/crates/assembly/core/src/agentic/tools/tool_context_runtime.rs
index f2035c0eb..3014cb8ea 100644
--- a/src/crates/assembly/core/src/agentic/tools/tool_context_runtime.rs
+++ b/src/crates/assembly/core/src/agentic/tools/tool_context_runtime.rs
@@ -46,9 +46,8 @@ use std::future::Future;
 use std::path::{Path, PathBuf};
 use tokio_util::sync::CancellationToken;
 use tool_runtime::context::{
-    build_tool_runtime_custom_data, delegation_policy_from_custom_data,
-    primary_model_supports_image_understanding as runtime_primary_model_supports_image_understanding,
-    project_tool_context_facts, ToolRuntimeContextFactsInput, ToolRuntimeCustomDataInput,
+    build_tool_runtime_custom_data, delegation_policy_from_custom_data, project_tool_context_facts,
+    PrimaryModelFacts, ToolRuntimeContextFactsInput, ToolRuntimeCustomDataInput,
 };
 
 /// Core-owned tool use context.
@@ -60,6 +59,7 @@ pub struct ToolUseContext {
     pub dialog_turn_id: Option<String>,
     pub workspace: Option<WorkspaceBinding>,
     pub unlocked_collapsed_tools: Vec<String>,
+    pub primary_model_facts: PrimaryModelFacts,
     /// Extended context data passed from execution layer to tools.
     pub custom_data: HashMap<String, Value>,
     /// Desktop automation (Computer use); only set in BitFun desktop.
@@ -113,7 +113,11 @@ impl ToolUseContext {
     /// Whether the session primary model accepts image inputs (from tool-definition / pipeline context).
     /// Defaults to **true** when unset (e.g. API listings without model metadata).
     pub fn primary_model_supports_image_understanding(&self) -> bool {
-        runtime_primary_model_supports_image_understanding(&self.custom_data)
+        self.primary_model_facts.supports_image_inputs
+    }
+
+    pub fn primary_model_facts(&self) -> &PrimaryModelFacts {
+        &self.primary_model_facts
     }
 
     pub fn cancellation_token(&self) -> Option<&CancellationToken> {
@@ -135,6 +139,7 @@ impl ToolUseContext {
             dialog_turn_id: None,
             workspace,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -210,6 +215,7 @@ pub(crate) fn build_tool_use_context_for_execution_context(
         dialog_turn_id: Some(context.dialog_turn_id.clone()),
         workspace: context.workspace.clone(),
         unlocked_collapsed_tools: context.unlocked_collapsed_tools.clone(),
+        primary_model_facts: context.primary_model_facts.clone(),
         custom_data: build_tool_context_custom_data(context),
         computer_use_host,
         runtime_handles: ToolRuntimeHandles::new(
@@ -224,35 +230,11 @@ pub(crate) fn build_tool_description_context(
     agent_type: &str,
     workspace: Option<&WorkspaceBinding>,
     workspace_services: Option<&WorkspaceServices>,
-    primary_model_id: Option<&str>,
-    primary_model_name: Option<&str>,
-    primary_model_provider: Option<&str>,
-    primary_supports_image_understanding: bool,
+    primary_model_facts: Option<&PrimaryModelFacts>,
     context_vars: &HashMap<String, String>,
 ) -> ToolUseContext {
     let mut custom_data = HashMap::new();
-    if let Some(primary_model_id) = primary_model_id {
-        custom_data.insert(
-            "primary_model_id".to_string(),
-            Value::String(primary_model_id.to_string()),
-        );
-    }
-    if let Some(primary_model_name) = primary_model_name {
-        custom_data.insert(
-            "primary_model_name".to_string(),
-            Value::String(primary_model_name.to_string()),
-        );
-    }
-    if let Some(primary_model_provider) = primary_model_provider {
-        custom_data.insert(
-            "primary_model_provider".to_string(),
-            Value::String(primary_model_provider.to_string()),
-        );
-    }
-    custom_data.insert(
-        "primary_model_supports_image_understanding".to_string(),
-        Value::Bool(primary_supports_image_understanding),
-    );
+    let primary_model_facts = primary_model_facts.cloned().unwrap_or_default();
     for (key, value) in context_vars {
         custom_data.insert(key.clone(), Value::String(value.clone()));
     }
@@ -264,6 +246,7 @@ pub(crate) fn build_tool_description_context(
         dialog_turn_id: None,
         workspace: workspace.cloned(),
         unlocked_collapsed_tools: Vec::new(),
+        primary_model_facts,
         custom_data,
         computer_use_host: None,
         runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -667,6 +650,7 @@ mod context_facts_tests {
     use crate::service::remote_ssh::workspace_state::workspace_session_identity;
     use std::collections::{BTreeSet, HashMap};
     use std::path::PathBuf;
+    use tool_runtime::context::PrimaryModelFacts;
 
     fn local_context(root: &str) -> ToolUseContext {
         ToolUseContext {
@@ -676,6 +660,7 @@ mod context_facts_tests {
             dialog_turn_id: None,
             workspace: Some(WorkspaceBinding::new(None, PathBuf::from(root))),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -692,6 +677,7 @@ mod context_facts_tests {
             dialog_turn_id: Some("turn-1".to_string()),
             workspace: Some(WorkspaceBinding::new(None, PathBuf::from("/repo/project"))),
             unlocked_collapsed_tools: vec!["WebFetch".to_string()],
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions {
@@ -736,6 +722,7 @@ mod context_facts_tests {
             dialog_turn_id: Some("turn-runtime".to_string()),
             workspace: Some(WorkspaceBinding::new(None, PathBuf::from("/repo/runtime"))),
             unlocked_collapsed_tools: vec!["WebFetch".to_string(), "Git".to_string()],
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data,
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions {
@@ -797,6 +784,7 @@ mod context_facts_tests {
                 session_identity,
             )),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -839,6 +827,7 @@ mod path_resolution_tests {
     use crate::service::remote_ssh::workspace_state::workspace_session_identity;
     use std::collections::HashMap;
     use std::path::PathBuf;
+    use tool_runtime::context::PrimaryModelFacts;
 
     fn local_context(root: &str) -> ToolUseContext {
         ToolUseContext {
@@ -848,6 +837,7 @@ mod path_resolution_tests {
             dialog_turn_id: None,
             workspace: Some(WorkspaceBinding::new(None, PathBuf::from(root))),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -871,6 +861,7 @@ mod path_resolution_tests {
                 session_identity,
             )),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -896,6 +887,7 @@ mod path_resolution_tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -1055,6 +1047,7 @@ mod call_runtime_tests {
     use std::collections::HashMap;
     use tokio::time::{sleep, Duration};
     use tokio_util::sync::CancellationToken;
+    use tool_runtime::context::PrimaryModelFacts;
 
     struct MeasurementReadTool;
 
@@ -1101,6 +1094,7 @@ mod call_runtime_tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -1137,6 +1131,7 @@ mod call_runtime_tests {
             dialog_turn_id: None,
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -1177,6 +1172,7 @@ mod call_runtime_tests {
             dialog_turn_id: Some("subagent-turn".to_string()),
             workspace: None,
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: PrimaryModelFacts::default(),
             custom_data,
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
@@ -1207,25 +1203,23 @@ mod call_runtime_tests {
 #[cfg(test)]
 mod context_builder_tests {
     use super::build_tool_description_context;
-    use serde_json::json;
     use std::collections::HashMap;
+    use tool_runtime::context::PrimaryModelFacts;
 
     #[test]
     fn tool_description_context_preserves_manifest_custom_data_shape() {
-        let mut context_vars = HashMap::new();
-        context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "false".to_string(),
-        );
+        let context_vars = HashMap::new();
 
         let context = build_tool_description_context(
             "coding",
             None,
             None,
-            Some("model_1"),
-            Some("vision-model"),
-            Some("anthropic"),
-            true,
+            Some(&PrimaryModelFacts::new(
+                "model_1",
+                "vision-model",
+                "anthropic",
+                true,
+            )),
             &context_vars,
         );
 
@@ -1238,19 +1232,16 @@ mod context_builder_tests {
         assert!(context.cancellation_token().is_none());
         assert!(context.workspace_services().is_none());
         assert!(context.runtime_tool_restrictions.is_tool_allowed("Write"));
-        assert_eq!(
-            context.custom_data["primary_model_supports_image_understanding"],
-            json!("false")
-        );
-        assert_eq!(context.custom_data["primary_model_id"], json!("model_1"));
-        assert_eq!(
-            context.custom_data["primary_model_name"],
-            json!("vision-model")
-        );
-        assert_eq!(
-            context.custom_data["primary_model_provider"],
-            json!("anthropic")
-        );
+        assert!(context.primary_model_supports_image_understanding());
+        assert_eq!(context.primary_model_facts().model_id, "model_1");
+        assert_eq!(context.primary_model_facts().model_name, "vision-model");
+        assert_eq!(context.primary_model_facts().api_format, "anthropic");
+        assert!(!context.custom_data.contains_key("primary_model_id"));
+        assert!(!context.custom_data.contains_key("primary_model_name"));
+        assert!(!context.custom_data.contains_key("primary_model_provider"));
+        assert!(!context
+            .custom_data
+            .contains_key("primary_model_supports_image_understanding"));
     }
 }
 
@@ -1266,15 +1257,11 @@ mod task_context_tests {
     use serde_json::json;
     use std::collections::{BTreeSet, HashMap};
     use tokio_util::sync::CancellationToken;
+    use tool_runtime::context::PrimaryModelFacts;
 
     fn task_with_context_vars() -> ToolTask {
         let mut context_vars = HashMap::new();
         context_vars.insert("turn_index".to_string(), "7".to_string());
-        context_vars.insert("primary_model_provider".to_string(), "openai".to_string());
-        context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "true".to_string(),
-        );
         context_vars.insert("acp_transport".to_string(), "true".to_string());
         context_vars.insert(
             "deep_review_run_manifest".to_string(),
@@ -1306,6 +1293,12 @@ mod task_context_tests {
                 attempt_index: None,
                 agent_type: "agent".to_string(),
                 workspace: None,
+                primary_model_facts: PrimaryModelFacts::new(
+                    "primary-model",
+                    "vision-model",
+                    "openai",
+                    true,
+                ),
                 context_vars,
                 subagent_parent_info: Some(SubagentParentInfo {
                     tool_call_id: "parent_tool".to_string(),
@@ -1346,14 +1339,13 @@ mod task_context_tests {
             .is_tool_allowed("WebFetch"));
         assert!(!context.runtime_tool_restrictions.is_tool_allowed("Bash"));
         assert_eq!(context.custom_data["turn_index"], json!(7));
-        assert_eq!(
-            context.custom_data["primary_model_provider"],
-            json!("openai")
-        );
-        assert_eq!(
-            context.custom_data["primary_model_supports_image_understanding"],
-            json!(true)
-        );
+        assert_eq!(context.primary_model_facts().model_id, "primary-model");
+        assert_eq!(context.primary_model_facts().api_format, "openai");
+        assert!(context.primary_model_facts().supports_image_inputs);
+        assert!(!context.custom_data.contains_key("primary_model_provider"));
+        assert!(!context
+            .custom_data
+            .contains_key("primary_model_supports_image_understanding"));
         assert_eq!(context.custom_data["acp_transport"], json!(true));
         assert_eq!(
             context.custom_data["deep_review_run_manifest"],
diff --git a/src/crates/assembly/core/src/agentic/tools/tool_result_storage.rs b/src/crates/assembly/core/src/agentic/tools/tool_result_storage.rs
index dc51850a3..32846922d 100644
--- a/src/crates/assembly/core/src/agentic/tools/tool_result_storage.rs
+++ b/src/crates/assembly/core/src/agentic/tools/tool_result_storage.rs
@@ -357,6 +357,7 @@ mod tests {
             dialog_turn_id: Some("turn_1".to_string()),
             workspace: Some(WorkspaceBinding::new(None, root)),
             unlocked_collapsed_tools: Vec::new(),
+            primary_model_facts: tool_runtime::context::PrimaryModelFacts::default(),
             custom_data: HashMap::new(),
             computer_use_host: None,
             runtime_tool_restrictions: ToolRuntimeRestrictions::default(),
diff --git a/src/crates/execution/tool-execution/src/context.rs b/src/crates/execution/tool-execution/src/context.rs
index 4b24d7be6..dd6a4fba7 100644
--- a/src/crates/execution/tool-execution/src/context.rs
+++ b/src/crates/execution/tool-execution/src/context.rs
@@ -3,6 +3,50 @@ use bitfun_runtime_ports::DelegationPolicy;
 use serde_json::Value;
 use std::collections::HashMap;
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct PrimaryModelFacts {
+    pub model_id: String,
+    pub model_name: String,
+    pub api_format: String,
+    pub supports_image_inputs: bool,
+}
+
+impl PrimaryModelFacts {
+    pub fn new(
+        model_id: impl Into<String>,
+        model_name: impl Into<String>,
+        api_format: impl Into<String>,
+        supports_image_inputs: bool,
+    ) -> Self {
+        Self {
+            model_id: model_id.into(),
+            model_name: model_name.into(),
+            api_format: api_format.into(),
+            supports_image_inputs,
+        }
+    }
+
+    pub fn multimodal_tool_output_supported(&self) -> bool {
+        matches!(
+            self.api_format.to_lowercase().as_str(),
+            "anthropic" | "openai" | "response" | "responses"
+        )
+    }
+}
+
+impl Default for PrimaryModelFacts {
+    fn default() -> Self {
+        Self {
+            model_id: String::new(),
+            model_name: String::new(),
+            api_format: String::new(),
+            // Preserve the historical behavior for listing/API contexts that do
+            // not carry model metadata.
+            supports_image_inputs: true,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy)]
 pub struct ToolRuntimeCustomDataInput<'a> {
     pub context_vars: &'a HashMap<String, String>,
@@ -37,12 +81,6 @@ pub fn build_tool_runtime_custom_data(
     );
 
     insert_u64_context_var(input.context_vars, &mut map, "turn_index");
-    insert_non_empty_string_context_var(input.context_vars, &mut map, "primary_model_provider");
-    insert_bool_context_var(
-        input.context_vars,
-        &mut map,
-        "primary_model_supports_image_understanding",
-    );
     insert_bool_context_var(input.context_vars, &mut map, "acp_transport");
     insert_bool_context_var(input.context_vars, &mut map, input.remote_file_delivery_key);
     if let Some(extension_custom_data) = input.extension_custom_data {
@@ -85,17 +123,6 @@ pub fn delegation_policy_from_custom_data(
     }
 }
 
-/// Whether the session primary model accepts image inputs.
-///
-/// Defaults to true when unset so API listings without model metadata keep the
-/// historical behavior.
-pub fn primary_model_supports_image_understanding(custom_data: &HashMap<String, Value>) -> bool {
-    custom_data
-        .get("primary_model_supports_image_understanding")
-        .and_then(Value::as_bool)
-        .unwrap_or(true)
-}
-
 fn insert_u64_context_var(
     context_vars: &HashMap<String, String>,
     map: &mut HashMap<String, Value>,
@@ -120,26 +147,12 @@ fn insert_bool_context_var(
     }
 }
 
-fn insert_non_empty_string_context_var(
-    context_vars: &HashMap<String, String>,
-    map: &mut HashMap<String, Value>,
-    key: &str,
-) {
-    if let Some(value) = context_vars
-        .get(key)
-        .map(String::as_str)
-        .filter(|value| !value.is_empty())
-    {
-        map.insert(key.to_string(), serde_json::json!(value));
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::{
         build_tool_runtime_custom_data, delegation_policy_from_custom_data,
-        primary_model_supports_image_understanding, project_tool_context_facts,
-        ToolRuntimeContextFactsInput, ToolRuntimeCustomDataInput,
+        project_tool_context_facts, PrimaryModelFacts, ToolRuntimeContextFactsInput,
+        ToolRuntimeCustomDataInput,
     };
     use bitfun_agent_tools::{ToolRuntimeRestrictions, ToolWorkspaceKind};
     use bitfun_runtime_ports::DelegationPolicy;
@@ -150,11 +163,6 @@ mod tests {
     fn materializes_provider_neutral_tool_custom_data() {
         let mut context_vars = HashMap::new();
         context_vars.insert("turn_index".to_string(), "7".to_string());
-        context_vars.insert("primary_model_provider".to_string(), "openai".to_string());
-        context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "false".to_string(),
-        );
         context_vars.insert("acp_transport".to_string(), "true".to_string());
         context_vars.insert("remote_file_delivery".to_string(), "true".to_string());
         let extension_custom_data = HashMap::from([("extension_key".to_string(), json!("kept"))]);
@@ -169,11 +177,6 @@ mod tests {
         assert_eq!(custom_data["delegation_allow_subagent_spawn"], json!(false));
         assert_eq!(custom_data["delegation_nesting_depth"], json!(1));
         assert_eq!(custom_data["turn_index"], json!(7));
-        assert_eq!(custom_data["primary_model_provider"], json!("openai"));
-        assert_eq!(
-            custom_data["primary_model_supports_image_understanding"],
-            json!(false)
-        );
         assert_eq!(custom_data["acp_transport"], json!(true));
         assert_eq!(custom_data["remote_file_delivery"], json!(true));
         assert_eq!(custom_data["extension_key"], json!("kept"));
@@ -183,11 +186,6 @@ mod tests {
     fn custom_data_ignores_invalid_or_empty_context_values() {
         let mut context_vars = HashMap::new();
         context_vars.insert("turn_index".to_string(), "not-a-number".to_string());
-        context_vars.insert("primary_model_provider".to_string(), "".to_string());
-        context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "not-bool".to_string(),
-        );
         context_vars.insert("acp_transport".to_string(), "not-bool".to_string());
         context_vars.insert("remote_file_delivery".to_string(), "not-bool".to_string());
 
@@ -201,8 +199,6 @@ mod tests {
         assert_eq!(custom_data["delegation_allow_subagent_spawn"], json!(true));
         assert_eq!(custom_data["delegation_nesting_depth"], json!(0));
         assert!(!custom_data.contains_key("turn_index"));
-        assert!(!custom_data.contains_key("primary_model_provider"));
-        assert!(!custom_data.contains_key("primary_model_supports_image_understanding"));
         assert!(!custom_data.contains_key("acp_transport"));
         assert!(!custom_data.contains_key("remote_file_delivery"));
     }
@@ -211,17 +207,9 @@ mod tests {
     fn extension_custom_data_cannot_override_runtime_owned_values() {
         let mut context_vars = HashMap::new();
         context_vars.insert("turn_index".to_string(), "7".to_string());
-        context_vars.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            "true".to_string(),
-        );
         let extension_custom_data = HashMap::from([
             ("turn_index".to_string(), json!(99)),
             ("delegation_allow_subagent_spawn".to_string(), json!(false)),
-            (
-                "primary_model_supports_image_understanding".to_string(),
-                json!(false),
-            ),
             ("extension_key".to_string(), json!("kept")),
         ]);
 
@@ -234,10 +222,6 @@ mod tests {
 
         assert_eq!(custom_data["delegation_allow_subagent_spawn"], json!(true));
         assert_eq!(custom_data["turn_index"], json!(7));
-        assert_eq!(
-            custom_data["primary_model_supports_image_understanding"],
-            json!(true)
-        );
         assert_eq!(custom_data["extension_key"], json!("kept"));
     }
 
@@ -246,11 +230,6 @@ mod tests {
         let mut custom_data = HashMap::new();
         custom_data.insert("delegation_allow_subagent_spawn".to_string(), json!(false));
         custom_data.insert("delegation_nesting_depth".to_string(), json!(3));
-        custom_data.insert(
-            "primary_model_supports_image_understanding".to_string(),
-            json!(false),
-        );
-
         assert_eq!(
             delegation_policy_from_custom_data(&custom_data),
             DelegationPolicy {
@@ -258,8 +237,7 @@ mod tests {
                 nesting_depth: 3
             }
         );
-        assert!(!primary_model_supports_image_understanding(&custom_data));
-        assert!(primary_model_supports_image_understanding(&HashMap::new()));
+        assert!(PrimaryModelFacts::default().supports_image_inputs);
     }
 
     #[test]