diff --git a/packages/core/src/orchestrator/prompt-builder.test.ts b/packages/core/src/orchestrator/prompt-builder.test.ts
index 5927857dfb..33b89090f2 100644
--- a/packages/core/src/orchestrator/prompt-builder.test.ts
+++ b/packages/core/src/orchestrator/prompt-builder.test.ts
@@ -30,6 +30,42 @@ describe('buildRoutingRulesWithProject', () => {
 
     expect(rules).toContain('NO knowledge of the conversation history');
   });
+
+  test('includes workflow slash-command catalog so the orchestrator stops hallucinating answers', () => {
+    // Regression: the orchestrator used to answer "you can't abandon a failed
+    // run, it's already terminal" when a user typed `workflow abandon X`
+    // without the leading slash. The agent had no information about which
+    // workflow slash-commands exist or what they do, so it guessed from
+    // training-time defaults. We now ship an authoritative catalog in the
+    // system prompt and instruct the agent to redirect to slash-prefix
+    // rather than answer from speculation.
+    const rules = buildRoutingRulesWithProject();
+
+    expect(rules).toContain('## Workflow Slash Commands');
+    // Catalog-completeness: every documented subcommand must be present so the
+    // catalog stays the authoritative source the prompt claims it is. If any
+    // entry drifts out, the agent will silently fall back to training-time
+    // speculation for that command — exactly the failure mode this PR fixes.
+    // Pragmatic source-of-truth: this list mirrors the case statements in
+    // command-handler.ts:handleWorkflowCommand. When a new subcommand is added
+    // there, it should also be added to the prompt catalog (and to this list).
+    const expectedSubcommands = [
+      'run',
+      'resume',
+      'abandon',
+      'list',
+      'status',
+      'cancel',
+      'approve',
+      'reject',
+    ];
+    for (const cmd of expectedSubcommands) {
+      expect(rules).toContain(`/workflow ${cmd}`);
+    }
+    // The hard rule: don't speculate about workflow internals.
+    expect(rules).toContain('Do not invent rules about which statuses');
+    expect(rules).toContain('with the leading slash');
+  });
 });
 
 describe('formatWorkflowContextSection', () => {
diff --git a/packages/core/src/orchestrator/prompt-builder.ts b/packages/core/src/orchestrator/prompt-builder.ts
index 07a3a7a709..b813d6d740 100644
--- a/packages/core/src/orchestrator/prompt-builder.ts
+++ b/packages/core/src/orchestrator/prompt-builder.ts
@@ -132,7 +132,41 @@ To update a project's path:
 To remove a registered project:
    /remove-project {project-name}
 
-IMPORTANT: Always clone into ~/.archon/workspaces/{owner}/{repo}/source unless the user specifies a different location.`;
+IMPORTANT: Always clone into ~/.archon/workspaces/{owner}/{repo}/source unless the user specifies a different location.
+
+## Workflow Slash Commands
+
+Users have access to slash commands for direct workflow control. These bypass
+you (the orchestrator) and run through the command parser. They MUST start with
+a literal \`/\`. If a user types something that looks like one of these commands
+without the leading slash (e.g. "workflow abandon abc123", "workflow run X"),
+do NOT answer the question yourself based on guesses about workflow internals
+— suggest they re-type with a leading slash. The command parser is the
+authoritative source of truth, not your training data.
+
+Available slash commands:
+
+- \`/workflow run <name> "<args>"\` — run a workflow directly.
+- \`/workflow resume <id>\` — resume a failed or paused run from where it stopped.
+- \`/workflow abandon <id>\` — discard a workflow run (transitions it to
+  \`cancelled\`). Works on \`failed\`, \`paused\`, \`running\`, and \`pending\` runs.
+  Already-cancelled or already-completed runs cannot be abandoned.
+- \`/workflow list\` — show available workflows.
+- \`/workflow status\` — show all active workflow runs.
+- \`/workflow cancel\` — cancel a running workflow.
+- \`/workflow approve <id> [comment]\` — approve a paused (gate) run.
+- \`/workflow reject <id> [reason]\` — reject a paused (gate) run.
+
+Example of a slash-prefix-missing case:
+User: "workflow abandon 32c786ef8c68d3263a80ca9d9d463f3f"
+Correct response: "Try \`/workflow abandon 32c786ef8c68d3263a80ca9d9d463f3f\`
+(with the leading slash) — that runs the actual command. The chat agent can't
+execute workflow operations directly, only the slash-command parser can."
+
+Do not invent rules about which statuses can or can't transition. If the user
+is unsure whether an operation will work, the right answer is "try the slash
+command and see what it reports" — never speculate about terminal-status
+restrictions or other workflow internals.`;
 }
 
 /**