refactor(x): workspace context becomes an always-activated capability

The agent-notes and work-directory prompt blocks move out of the
composer into WORKSPACE_CONTEXT_CAPABILITY (activation: 'always'),
whose fragment is pure over the resolved inputs — the resolver still
loads notes/work-dir only for agents with the workspaceContext trait
and passes null otherwise, so trait gating is unchanged. The composer
now iterates one capability list (workspace + modes) in fixed order;
golden snapshots pass unchanged, byte-identical output. The composer's
own body is down to: base instructions + hidden-user-context + the
capability loop.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/x/packages/core/src/agents/compose-instructions.ts

@@ -1,4 +1,5 @@
 import { MODE_CAPABILITIES } from "../application/assistant/capabilities/modes.js";
+import { WORKSPACE_CONTEXT_CAPABILITY } from "../application/assistant/capabilities/workspace.js";
 import type { CapabilityContext } from "../application/assistant/capabilities/types.js";
 
 // System-prompt composition for agent assembly: the base instructions plus
@@ -52,33 +53,12 @@ export function composeSystemInstructions({
     coachMode,
 }: ComposeSystemInstructionsInput): string {
     let instructionsWithDateTime = `${instructions}\n\n${USER_CONTEXT_SYSTEM_INSTRUCTIONS}`;
-        if (agentNotesContext) {
-            instructionsWithDateTime += `\n\n${agentNotesContext}`;
-        }
-        if (userWorkDir) {
-                instructionsWithDateTime += `\n\n# User Work Directory
-The user has chosen the following directory as their current **work directory**:
-
-\`${userWorkDir}\`
-
-Treat this as the **default location** for file operations whenever the user refers to files generically:
-- "list the files", "show me what's in here", "what's the latest report" — list or look in the work directory.
-- "save this", "export it", "write that to a file" — write the output into the work directory unless the user names another location.
-- "open the file I was just working on", "the doc from earlier" — assume the work directory first.
-
-Use absolute paths rooted at this directory with the \`file-*\` tools. For example, list with \`file-list({ path: "${userWorkDir}" })\`, read text with \`file-readText\`, and write text with \`file-writeText\`. For PDFs, Office docs, images, scanned docs, and other non-text files, use \`parseFile\` or \`LLMParse\` with the absolute path; you do NOT need to copy the file into the workspace first.
-
-**Exceptions — these ALWAYS take precedence over the work directory default:**
-1. **Knowledge base questions.** If the user asks about anything in the knowledge graph (notes, people, organizations, projects, topics) or paths starting with \`knowledge/\`, use file tools against \`knowledge/\` as documented above. Do NOT redirect those into the work directory.
-2. **Explicit paths.** If the user names a different directory or gives an absolute/relative path (e.g. "in ~/Downloads", "from /tmp/foo", "the Desktop"), honor that path exactly and ignore the work-directory default for that request.
-3. **Workspace-specific operations.** Anything that obviously belongs in the Rowboat workspace (config files, MCP servers, agent schedules, etc.) stays in the workspace, not the work directory.
-
-Do not announce the work directory unless it's relevant. Just use it.`;
-        }
         // App-activated mode capabilities compose here, in MODE_CAPABILITIES
         // order — a fixed total order, so identical inputs yield identical
         // bytes. The fragment text lives with the capability records.
         const ctx: CapabilityContext = {
+            agentNotesContext,
+            userWorkDir,
             voiceInput,
             voiceOutput,
             searchEnabled,
@@ -87,7 +67,7 @@ Do not announce the work directory unless it's relevant. Just use it.`;
             videoMode: videoMode ?? false,
             coachMode: coachMode ?? false,
         };
-        for (const capability of MODE_CAPABILITIES) {
+        for (const capability of [WORKSPACE_CONTEXT_CAPABILITY, ...MODE_CAPABILITIES]) {
             const fragment = capability.promptFragment?.(ctx);
             if (fragment) {
                 instructionsWithDateTime += `\n\n${fragment}`;

apps/x/packages/core/src/application/assistant/capabilities/types.ts

@@ -26,6 +26,10 @@ export type CapabilityActivation = "model" | "app" | "always";
 // stay byte-identical for identical inputs (provider prefix caching and
 // agent-snapshot inheritance both depend on it).
 export interface CapabilityContext {
+    // Workspace context (workspaceContext trait agents only; the resolver
+    // loads these and leaves them null for everyone else).
+    agentNotesContext: string | null;
+    userWorkDir: string | null;
     voiceInput: boolean;
     voiceOutput: "summary" | "full" | null;
     searchEnabled: boolean;

apps/x/packages/core/src/application/assistant/capabilities/workspace.ts

@@ -0,0 +1,43 @@
+import type { CapabilityContext, CapabilityDefinition } from "./types.js";
+
+// The always-activated workspace-context capability: agent notes and the
+// user work directory, composed for agents with the workspaceContext trait
+// (the resolver loads both inputs and leaves them null for everyone else).
+// Fragment text extracted verbatim from the historical composer; the golden
+// snapshots in agents/compose-instructions.test.ts pin the bytes.
+
+export const WORKSPACE_CONTEXT_CAPABILITY: CapabilityDefinition = {
+    id: "workspace-context",
+    title: "Workspace Context",
+    summary: "Agent notes and the user's chosen work directory.",
+    activation: "always",
+    promptFragment: (ctx: CapabilityContext) => {
+        const parts: string[] = [];
+        if (ctx.agentNotesContext) {
+            parts.push(ctx.agentNotesContext);
+        }
+        if (ctx.userWorkDir) {
+            parts.push(WORK_DIR_TEMPLATE(ctx.userWorkDir));
+        }
+        return parts.length > 0 ? parts.join("\n\n") : null;
+    },
+};
+
+const WORK_DIR_TEMPLATE = (userWorkDir: string): string => `# User Work Directory
+The user has chosen the following directory as their current **work directory**:
+
+\`${userWorkDir}\`
+
+Treat this as the **default location** for file operations whenever the user refers to files generically:
+- "list the files", "show me what's in here", "what's the latest report" — list or look in the work directory.
+- "save this", "export it", "write that to a file" — write the output into the work directory unless the user names another location.
+- "open the file I was just working on", "the doc from earlier" — assume the work directory first.
+
+Use absolute paths rooted at this directory with the \`file-*\` tools. For example, list with \`file-list({ path: "${userWorkDir}" })\`, read text with \`file-readText\`, and write text with \`file-writeText\`. For PDFs, Office docs, images, scanned docs, and other non-text files, use \`parseFile\` or \`LLMParse\` with the absolute path; you do NOT need to copy the file into the workspace first.
+
+**Exceptions — these ALWAYS take precedence over the work directory default:**
+1. **Knowledge base questions.** If the user asks about anything in the knowledge graph (notes, people, organizations, projects, topics) or paths starting with \`knowledge/\`, use file tools against \`knowledge/\` as documented above. Do NOT redirect those into the work directory.
+2. **Explicit paths.** If the user names a different directory or gives an absolute/relative path (e.g. "in ~/Downloads", "from /tmp/foo", "the Desktop"), honor that path exactly and ignore the work-directory default for that request.
+3. **Workspace-specific operations.** Anything that obviously belongs in the Rowboat workspace (config files, MCP servers, agent schedules, etc.) stays in the workspace, not the work directory.
+
+Do not announce the work directory unless it's relevant. Just use it.`;