feat: relative working directory support and subagent tab cwd propagation

- Resolve relative cwd paths (e.g. ./subtask) against parent's working directory at runtime
- check-dir endpoint resolves relative paths and returns the resolved absolute path
- AgentBuilder shows resolved path below input for relative paths, updated helper text
- tab-created event now includes workingDirectory so subagent tabs display their cwd in sidebar
- Add workingDirectory to tab-created AgentEvent type definition
- spawnChildAgent stores resolved absolute path instead of raw relative path

5 files changed, 36 insertions, 6 deletions

diff --git a/packages/api/src/agent-manager.ts b/packages/api/src/agent-manager.ts
index 74995b2..d473950 100644
--- a/packages/api/src/agent-manager.ts
+++ b/packages/api/src/agent-manager.ts
@@ -329,6 +329,15 @@ export class AgentManager {
 				workingDirectory = join(homedir(), workingDirectory.slice(1));
 			}
 
+			// Resolve relative paths against the default working directory
+			// (e.g. subagent cwd "./subtask" resolves relative to the parent's effective dir)
+			{
+				const { isAbsolute, resolve } = await import("node:path");
+				if (!isAbsolute(workingDirectory)) {
+					workingDirectory = resolve(defaultWorkDir, workingDirectory);
+				}
+			}
+
 			// Auto-create the working directory if it doesn't exist
 			try {
 				const { mkdirSync, existsSync } = await import("node:fs");
@@ -668,6 +677,8 @@ export class AgentManager {
 			parentEffectiveDir = join(homedir(), parentEffectiveDir.slice(1));
 		}
 
+		// Resolve and validate child working directory against parent's effective dir
+		let resolvedWorkingDirectory = options.workingDirectory;
 		if (options.workingDirectory) {
 			const { isAbsolute, relative, resolve, join } = await import("node:path");
 			// Expand ~ in child working directory
@@ -685,6 +696,9 @@ export class AgentManager {
 					`Working directory "${options.workingDirectory}" is outside the parent's working directory "${parentDir}".`,
 				);
 			}
+			// Store the resolved absolute path so downstream code doesn't
+			// re-resolve against the wrong base directory
+			resolvedWorkingDirectory = resolved;
 		}
 
 		// Intersect requested tools with parent's allowed tools to prevent privilege escalation
@@ -696,7 +710,7 @@ export class AgentManager {
 		// Create the tab agent entry with overrides
 		const tabAgent = this._getOrCreateTabAgent(tabId);
 		tabAgent.toolsOverride = childTools;
-		tabAgent.workingDirectoryOverride = options.workingDirectory;
+		tabAgent.workingDirectoryOverride = resolvedWorkingDirectory;
 		tabAgent.keyId = options.parentKeyId ?? null;
 		tabAgent.modelId = options.parentModelId ?? null;
 		tabAgent.finalOutput = "";
@@ -727,6 +741,7 @@ export class AgentManager {
 				keyId: tabAgent.keyId,
 				modelId: tabAgent.modelId,
 				parentTabId: options.parentTabId ?? null,
+				workingDirectory: resolvedWorkingDirectory ?? null,
 			},
 			tabId,
 		);
diff --git a/packages/api/src/routes/agents.ts b/packages/api/src/routes/agents.ts
index d3ca23f..1627674 100644
--- a/packages/api/src/routes/agents.ts
+++ b/packages/api/src/routes/agents.ts
@@ -99,11 +99,16 @@ agentsRoutes.get("/check-dir", (c) => {
 	if (dirPath === "~" || dirPath.startsWith("~/")) {
 		dirPath = path.join(os.homedir(), dirPath.slice(1));
 	}
+	// Resolve relative paths against the project root
+	if (!path.isAbsolute(dirPath)) {
+		const projectDir = process.env.DISPATCH_WORKING_DIR || process.cwd();
+		dirPath = path.resolve(projectDir, dirPath);
+	}
 	try {
 		const stat = fs.statSync(dirPath);
-		return c.json({ exists: stat.isDirectory() });
+		return c.json({ exists: stat.isDirectory(), resolved: dirPath });
 	} catch {
-		return c.json({ exists: false });
+		return c.json({ exists: false, resolved: dirPath });
 	}
 });
 
diff --git a/packages/core/src/types/index.ts b/packages/core/src/types/index.ts
index ff47f49..c301822 100644
--- a/packages/core/src/types/index.ts
+++ b/packages/core/src/types/index.ts
@@ -47,6 +47,7 @@ export type AgentEvent =
 			keyId: string | null;
 			modelId: string | null;
 			parentTabId: string | null;
+			workingDirectory: string | null;
 	  }
 	| { type: "message-queued"; tabId: string; messageId: string; message: string }
 	| { type: "message-consumed"; tabId: string; messageIds: string[] }
diff --git a/packages/frontend/src/lib/components/AgentBuilder.svelte b/packages/frontend/src/lib/components/AgentBuilder.svelte
index 65fd764..d85a6a3 100644
--- a/packages/frontend/src/lib/components/AgentBuilder.svelte
+++ b/packages/frontend/src/lib/components/AgentBuilder.svelte
@@ -62,6 +62,7 @@ const modelCache = new Map();
 	let formScope = $state("global");
 	let formCwd = $state("");
 	let cwdExists = $state<boolean | null>(null);
+	let cwdResolved = $state<string | null>(null);
 	let cwdCheckTimer: ReturnType<typeof setTimeout> | null = null;
 	let formSkills = $state<Set<string>>(new Set());
 	let formTools = $state<Set<string>>(new Set());
@@ -301,6 +302,7 @@ const modelCache = new Map();
 		const cwd = formCwd;
 		if (!cwd.trim()) {
 			cwdExists = null;
+			cwdResolved = null;
 			return;
 		}
 		if (cwdCheckTimer) clearTimeout(cwdCheckTimer);
@@ -312,9 +314,11 @@ const modelCache = new Map();
 				if (res.ok) {
 					const data = await res.json();
 					cwdExists = data.exists ?? false;
+					cwdResolved = data.resolved ?? null;
 				}
 			} catch {
 				cwdExists = null;
+				cwdResolved = null;
 			}
 		}, 300);
 	});
@@ -479,8 +483,12 @@ const modelCache = new Map();
 						</div>
 						{#if cwdExists === false && formCwd.trim()}
 							<span class="text-xs text-warning">Directory will be created automatically on first message.</span>
-						{:else}
-							<span class="text-xs text-base-content/50">Absolute path. Leave empty to use the project root.</span>
+						{/if}
+						{#if cwdResolved && formCwd.trim() && cwdResolved !== formCwd.trim()}
+							<span class="text-xs text-base-content/50 font-mono">{cwdResolved}</span>
+						{/if}
+						{#if !formCwd.trim()}
+							<span class="text-xs text-base-content/50">Absolute or relative path. Relative paths resolve against the parent agent's working directory, or the project root.</span>
 						{/if}
 					</div>
 
diff --git a/packages/frontend/src/lib/tabs.svelte.ts b/packages/frontend/src/lib/tabs.svelte.ts
index 7f4d768..c488a92 100644
--- a/packages/frontend/src/lib/tabs.svelte.ts
+++ b/packages/frontend/src/lib/tabs.svelte.ts
@@ -462,6 +462,7 @@ function createTabStore() {
 					keyId: string | null;
 					modelId: string | null;
 					parentTabId: string | null;
+					workingDirectory: string | null;
 				};
 				// Only add if we don't already have this tab
 				if (!getTabById(newTabEvent.id)) {
@@ -480,7 +481,7 @@ function createTabStore() {
 						persistent: newTabEvent.parentTabId == null,
 						agentSlug: null,
 						agentScope: null,
-						workingDirectory: null,
+						workingDirectory: newTabEvent.workingDirectory ?? null,
 						queuedMessages: [],
 					};
 					tabs = [...tabs, tab];