fix: accept omitted condition in fallback transitions

Fallback transitions (last entry in graph node) omit the condition
field in YAML, resulting in undefined instead of null. The validator
and materializer now handle this:

- validate.ts: accept undefined as valid condition value
- workflow.ts: normalizeGraph() coerces undefined → null before CAS put

This was broken by the graph fallback pattern introduced in #370.

.workflows/solve-issue.yaml

@@ -23,7 +23,7 @@ roles:
       1. Store it via `uwf cas put "<markdown content>"` and capture the returned hash
       2. Put the hash in meta.plan (required when status=ready)
     output: "Output a brief summary of the test spec. Frontmatter must include: status (ready or insufficient_info) and plan (CAS hash of the test spec, required when status=ready)."
-    meta:
+    frontmatter:
       type: object
       properties:
         status:
@@ -45,7 +45,7 @@ roles:
       5. Ensure `bun run build` passes with no errors
       6. Run `bun test` to verify all tests pass
     output: "List all files changed and provide a summary. Frontmatter must include: status (done or failed)."
-    meta:
+    frontmatter:
       type: object
       properties:
         status:
@@ -75,7 +75,7 @@ roles:
       Only review standards compliance. Do NOT test functionality.
       If rejecting, you MUST explain the specific reason in your output.
     output: "Explain your decision with specific file/line references. Frontmatter must include: approved (true or false)."
-    meta:
+    frontmatter:
       type: object
       properties:
         approved:
@@ -95,7 +95,7 @@ roles:
          - fix_code: tests fail or implementation doesn't match spec → send back to developer
          - fix_spec: the spec itself is wrong or incomplete → send back to planner
     output: "Report test results per scenario. Frontmatter must include: status (passed, fix_code, or fix_spec)."
-    meta:
+    frontmatter:
       type: object
       properties:
         status:
@@ -115,7 +115,7 @@ roles:
       4. On push success: create a PR via `tea pr create --title "..." --description "..."`
          - PR description must follow the project template: What / Why / Changes / Ref sections, with `Fixes #N` in Ref
     output: "Include PR URL on success or error log on failure. Frontmatter must include: success (true or false)."
-    meta:
+    frontmatter:
       type: object
       properties:
         success:
@@ -124,22 +124,22 @@ roles:
 conditions:
   insufficientInfo:
     description: "Planner determined there's not enough info to proceed"
-    expression: "steps[-1].output.status = 'insufficient_info'"
+    expression: "$last('planner').status = 'insufficient_info'"
   devFailed:
     description: "Developer failed to implement"
-    expression: "steps[-1].output.status = 'failed'"
+    expression: "$last('developer').status = 'failed'"
   rejected:
     description: "Reviewer rejected the implementation"
-    expression: "steps[-1].output.approved = false"
+    expression: "$last('reviewer').approved = false"
   fixCode:
     description: "Tester found code issues"
-    expression: "steps[-1].output.status = 'fix_code'"
+    expression: "$last('tester').status = 'fix_code'"
   fixSpec:
     description: "Tester found spec issues"
-    expression: "steps[-1].output.status = 'fix_spec'"
+    expression: "$last('tester').status = 'fix_spec'"
   hookFailed:
     description: "Push hook failed"
-    expression: "steps[-1].output.success = false"
+    expression: "$last('committer').success = false"
 graph:
   $START:
     - role: "planner"

examples/analyze-topic.yaml

@@ -19,7 +19,7 @@ roles:
     output: |
       Provide your analysis as markdown under the frontmatter.
       The frontmatter must include your structured findings.
-    meta:
+    frontmatter:
       type: object
       properties:
         thesis:

examples/solve-issue.yaml

@@ -9,7 +9,7 @@ roles:
       - planning
     procedure: "Analyze the issue and create a detailed, actionable implementation plan."
     output: "Output the plan summary and list of concrete steps."
-    meta:
+    frontmatter:
       type: object
       properties:
         plan:
@@ -28,7 +28,7 @@ roles:
       - testing
     procedure: "Implement the plan. Write code, tests, and ensure existing tests pass."
     output: "List all files changed and provide a summary of the implementation."
-    meta:
+    frontmatter:
       type: object
       properties:
         filesChanged:
@@ -46,7 +46,7 @@ roles:
       - static-analysis
     procedure: "Review the implementation against the plan. Check for bugs, edge cases, and style."
     output: "Approve or reject with detailed comments explaining your decision."
-    meta:
+    frontmatter:
       type: object
       properties:
         approved:
@@ -57,7 +57,7 @@ roles:
 conditions:
   notApproved:
     description: "Reviewer rejected the implementation"
-    expression: "steps[-1].output.approved = false"
+    expression: "$last('reviewer').approved = false"
 graph:
   $START:
     - role: "planner"

packages/cli-workflow/src/commands/workflow.ts

@@ -2,7 +2,12 @@ import { readFile } from "node:fs/promises";
 
 import type { JSONSchema } from "@uncaged/json-cas";
 import { putSchema, validate } from "@uncaged/json-cas";
-import type { CasRef, RoleDefinition, WorkflowPayload } from "@uncaged/workflow-protocol";
+import type {
+  CasRef,
+  RoleDefinition,
+  Transition,
+  WorkflowPayload,
+} from "@uncaged/workflow-protocol";
 import { parse } from "yaml";
 
 import {
@@ -46,11 +51,28 @@ function isJsonSchema(value: unknown): value is JSONSchema {
   return typeof value === "object" && value !== null && !Array.isArray(value);
 }
 
-async function resolveMetaRef(uwf: UwfStore, roleName: string, meta: unknown): Promise<CasRef> {
-  if (!isJsonSchema(meta)) {
-    fail(`role "${roleName}": meta must be a JSON Schema object`);
+/** Normalize graph transitions: ensure condition is null (not undefined) for fallback entries. */
+function normalizeGraph(graph: Record<string, Transition[]>): Record<string, Transition[]> {
+  const result: Record<string, Transition[]> = {};
+  for (const [node, transitions] of Object.entries(graph)) {
+    result[node] = transitions.map((t) => ({
+      role: t.role,
+      condition: t.condition ?? null,
+    }));
   }
-  const schema: JSONSchema = meta.title === undefined ? { ...meta, title: roleName } : meta;
+  return result;
+}
+
+async function resolveFrontmatterRef(
+  uwf: UwfStore,
+  roleName: string,
+  frontmatter: unknown,
+): Promise<CasRef> {
+  if (!isJsonSchema(frontmatter)) {
+    fail(`role "${roleName}": frontmatter must be a JSON Schema object`);
+  }
+  const schema: JSONSchema =
+    frontmatter.title === undefined ? { ...frontmatter, title: roleName } : frontmatter;
   return putSchema(uwf.store, schema);
 }
 
@@ -60,14 +82,18 @@ export async function materializeWorkflowPayload(
 ): Promise<WorkflowPayload> {
   const roles: Record<string, RoleDefinition> = {};
   for (const [roleName, role] of Object.entries(raw.roles)) {
-    const meta = await resolveMetaRef(uwf, `${raw.name}.${roleName}`, role.meta);
+    const frontmatter = await resolveFrontmatterRef(
+      uwf,
+      `${raw.name}.${roleName}`,
+      role.frontmatter,
+    );
     roles[roleName] = {
       description: role.description,
       goal: role.goal,
       capabilities: role.capabilities,
       procedure: role.procedure,
       output: role.output,
-      meta,
+      frontmatter,
     };
   }
   return {
@@ -75,7 +101,7 @@ export async function materializeWorkflowPayload(
     description: raw.description,
     roles,
     conditions: raw.conditions,
-    graph: raw.graph,
+    graph: normalizeGraph(raw.graph),
   };
 }
 

packages/cli-workflow/src/validate.ts

@@ -15,8 +15,8 @@ function isRoleDefinition(value: unknown): boolean {
   if (!isRecord(value)) {
     return false;
   }
-  const meta = value.meta;
-  const metaOk = isRecord(meta) && typeof meta.type === "string";
+  const frontmatter = value.frontmatter;
+  const frontmatterOk = isRecord(frontmatter) && typeof frontmatter.type === "string";
   const capabilities = value.capabilities;
   const capabilitiesOk =
     Array.isArray(capabilities) && capabilities.every((c) => typeof c === "string");
@@ -26,7 +26,7 @@ function isRoleDefinition(value: unknown): boolean {
     capabilitiesOk &&
     typeof value.procedure === "string" &&
     typeof value.output === "string" &&
-    metaOk
+    frontmatterOk
   );
 }
 
@@ -42,7 +42,10 @@ function isTransition(value: unknown): boolean {
     return false;
   }
   const condition = value.condition;
-  return typeof value.role === "string" && (condition === null || typeof condition === "string");
+  return (
+    typeof value.role === "string" &&
+    (condition === null || condition === undefined || typeof condition === "string")
+  );
 }
 
 function isStringRecord(value: unknown, itemCheck: (item: unknown) => boolean): boolean {

packages/workflow-agent-kit/src/run.ts

@@ -130,13 +130,18 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
       fail(`unknown role: ${role}`);
     }
 
-    const metaSchema = getSchema(ctx.meta.store, roleDef.meta);
-    if (metaSchema !== null) {
-      ctx.outputFormatInstruction = buildOutputFormatInstruction(metaSchema);
+    const frontmatterSchema = getSchema(ctx.meta.store, roleDef.frontmatter);
+    if (frontmatterSchema !== null) {
+      ctx.outputFormatInstruction = buildOutputFormatInstruction(frontmatterSchema);
     }
 
     const agentResult = await runAgent(options, ctx);
-    const outputHash = await extractOutput(agentResult.output, roleDef.meta, storageRoot, ctx);
+    const outputHash = await extractOutput(
+      agentResult.output,
+      roleDef.frontmatter,
+      storageRoot,
+      ctx,
+    );
     const stepHash = await persistStep({
       ctx,
       outputHash,

packages/workflow-moderator/__tests__/evaluate.test.ts

@@ -35,11 +35,11 @@ const solveIssueWorkflow: WorkflowPayload = {
   conditions: {
     needsClarification: {
       description: "Planner requests clarification from user",
-      expression: "$exists(steps[-1].output.needsClarification)",
+      expression: "$exists($last('planner').needsClarification)",
     },
-    notApproved: {
+    rejected: {
       description: "Reviewer rejected the implementation",
-      expression: "steps[-1].output.approved = false",
+      expression: "$last('reviewer').approved = false",
     },
   },
   graph: {
@@ -50,7 +50,7 @@ const solveIssueWorkflow: WorkflowPayload = {
     ],
     developer: [{ role: "reviewer", condition: null }],
     reviewer: [
-      { role: "developer", condition: "notApproved" },
+      { role: "developer", condition: "rejected" },
       { role: "$END", condition: null },
     ],
   },
@@ -72,7 +72,7 @@ describe("evaluate", () => {
     expect(result).toEqual({ ok: true, value: "planner" });
   });
 
-  test("condition match (notApproved → developer)", async () => {
+  test("condition match (rejected → developer)", async () => {
     const context = makeContext([
       {
         role: "reviewer",
@@ -126,4 +126,116 @@ describe("evaluate", () => {
     const result = await evaluate(solveIssueWorkflow, context);
     expect(result).toEqual({ ok: true, value: "developer" });
   });
+
+  test("$last returns most recent matching role's frontmatter", async () => {
+    const workflow: WorkflowPayload = {
+      ...solveIssueWorkflow,
+      conditions: {
+        devFailed: {
+          description: "Developer failed",
+          expression: "$last('developer').status = 'failed'",
+        },
+      },
+      graph: {
+        $START: [{ role: "developer", condition: null }],
+        developer: [
+          { role: "$END", condition: "devFailed" },
+          { role: "reviewer", condition: null },
+        ],
+      },
+    };
+    const context = makeContext([
+      {
+        role: "developer",
+        output: { status: "done" },
+        detail: "1VPBG9SM5E7WK",
+        agent: "uwf-hermes",
+      },
+      {
+        role: "reviewer",
+        output: { approved: false },
+        detail: "2MXBG6PN4A8JR",
+        agent: "uwf-hermes",
+      },
+      {
+        role: "developer",
+        output: { status: "failed" },
+        detail: "3QNTH7WK8D2PA",
+        agent: "uwf-hermes",
+      },
+    ]);
+    const result = await evaluate(workflow, context);
+    expect(result).toEqual({ ok: true, value: "$END" });
+  });
+
+  test("$first returns earliest matching role's frontmatter", async () => {
+    const workflow: WorkflowPayload = {
+      ...solveIssueWorkflow,
+      conditions: {
+        firstPlanReady: {
+          description: "First planner run was ready",
+          expression: "$first('planner').status = 'ready'",
+        },
+      },
+      graph: {
+        $START: [{ role: "planner", condition: null }],
+        planner: [
+          { role: "$END", condition: "firstPlanReady" },
+          { role: "developer", condition: null },
+        ],
+      },
+    };
+    const context = makeContext([
+      {
+        role: "planner",
+        output: { status: "ready", plan: "ABC123" },
+        detail: "7BQST3VW9F2MA",
+        agent: "uwf-hermes",
+      },
+      {
+        role: "developer",
+        output: { status: "done" },
+        detail: "1VPBG9SM5E7WK",
+        agent: "uwf-hermes",
+      },
+      {
+        role: "planner",
+        output: { status: "revised", plan: "DEF456" },
+        detail: "4RNMK6PX8B3WQ",
+        agent: "uwf-hermes",
+      },
+    ]);
+    const result = await evaluate(workflow, context);
+    expect(result).toEqual({ ok: true, value: "$END" });
+  });
+
+  test("$last returns undefined for unmatched role", async () => {
+    const workflow: WorkflowPayload = {
+      ...solveIssueWorkflow,
+      conditions: {
+        hasReviewer: {
+          description: "Reviewer has run",
+          expression: "$exists($last('reviewer'))",
+        },
+      },
+      graph: {
+        $START: [{ role: "planner", condition: null }],
+        planner: [
+          { role: "$END", condition: "hasReviewer" },
+          { role: "developer", condition: null },
+        ],
+      },
+    };
+    const context = makeContext([
+      {
+        role: "planner",
+        output: { status: "ready" },
+        detail: "7BQST3VW9F2MA",
+        agent: "uwf-hermes",
+      },
+    ]);
+    const result = await evaluate(workflow, context);
+    // no reviewer step → $exists returns false → fallback to developer
+    expect(result).toEqual({ ok: true, value: "developer" });
+  });
 });

packages/workflow-moderator/src/evaluate.ts

@@ -21,12 +21,44 @@ function isTruthy(value: unknown): boolean {
   return true;
 }
 
+function findByRole(
+  steps: ModeratorContext["steps"],
+  role: string,
+  direction: "first" | "last",
+): unknown {
+  if (direction === "last") {
+    for (let i = steps.length - 1; i >= 0; i--) {
+      if (steps[i].role === role) {
+        return steps[i].output;
+      }
+    }
+  } else {
+    for (const step of steps) {
+      if (step.role === role) {
+        return step.output;
+      }
+    }
+  }
+  return undefined;
+}
+
 async function evaluateJsonata(
   expression: string,
   context: ModeratorContext,
 ): Promise<Result<unknown, Error>> {
   try {
-    const result = await jsonata(expression).evaluate(context);
+    const expr = jsonata(expression);
+    expr.registerFunction(
+      "first",
+      (role: string) => findByRole(context.steps, role, "first"),
+      "<s:x>",
+    );
+    expr.registerFunction(
+      "last",
+      (role: string) => findByRole(context.steps, role, "last"),
+      "<s:x>",
+    );
+    const result = await expr.evaluate(context);
     return { ok: true, value: result };
   } catch (error) {
     return {

packages/workflow-protocol/src/schemas.ts

@@ -2,14 +2,14 @@ import type { JSONSchema } from "@uncaged/json-cas";
 
 const ROLE_DEFINITION: JSONSchema = {
   type: "object",
-  required: ["description", "goal", "capabilities", "procedure", "output", "meta"],
+  required: ["description", "goal", "capabilities", "procedure", "output", "frontmatter"],
   properties: {
     description: { type: "string" },
     goal: { type: "string" },
     capabilities: { type: "array", items: { type: "string" } },
     procedure: { type: "string" },
     output: { type: "string" },
-    meta: { type: "string", format: "cas_ref" },
+    frontmatter: { type: "string", format: "cas_ref" },
   },
   additionalProperties: false,
 };

packages/workflow-protocol/src/types.ts

@@ -22,7 +22,7 @@ export type RoleDefinition = {
   capabilities: string[];
   procedure: string;
   output: string;
-  meta: CasRef;
+  frontmatter: CasRef;
 };
 
 export type Transition = {