jr: add 'prompt' command to inspect agent system prompt

jr prompt <task-id> constructs and prints the full system prompt
that would be sent to the agent, including:
- Agent configuration (model, cost budget)
- Base instructions
- AGENTS.md content
- Relevant facts from knowledge base
- Retry/progress context if applicable

Useful for debugging agent behavior and token usage.

1 files changed, 54 insertions, 1 deletions

diff --git a/Omni/Agent/Worker.hs b/Omni/Agent/Worker.hs
index 45caf9b..110c929 100644
--- a/Omni/Agent/Worker.hs
+++ b/Omni/Agent/Worker.hs
@@ -1,7 +1,13 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE NoImplicitPrelude #-}
 
-module Omni.Agent.Worker where
+module Omni.Agent.Worker
+  ( start,
+    buildFullPrompt,
+    selectModel,
+    selectCostByComplexity,
+  )
+where
 
 import Alpha
 import qualified Data.Aeson as Aeson
@@ -575,3 +581,50 @@ formatFact f =
            then ""
            else " [" <> Text.intercalate ", " (TaskCore.factRelatedFiles f) <> "]"
        )
+
+-- | Build the full system prompt for a task without starting the agent.
+-- This is useful for debugging/inspecting what the agent will be told.
+buildFullPrompt :: TaskCore.Task -> IO Text
+buildFullPrompt task = do
+  repo <- Directory.getCurrentDirectory
+  let ns = fromMaybe "." (TaskCore.taskNamespace task)
+  let basePrompt = buildBasePrompt task ns repo
+
+  maybeRetry <- TaskCore.getRetryContext (TaskCore.taskId task)
+  progressContent <- TaskCore.getProgressSummary (TaskCore.taskId task)
+
+  let progressPrompt = buildProgressPrompt progressContent
+  let retryPrompt = buildRetryPrompt maybeRetry
+  let prompt = basePrompt <> progressPrompt <> retryPrompt
+
+  agentsMd <-
+    fmap (fromMaybe "") <| do
+      exists <- Directory.doesFileExist (repo </> "AGENTS.md")
+      if exists
+        then Just </ readFile (repo </> "AGENTS.md")
+        else pure Nothing
+
+  relevantFacts <- getRelevantFacts task
+  let factsSection = formatFacts relevantFacts
+
+  let systemPrompt =
+        prompt
+          <> "\n\nREPOSITORY GUIDELINES (AGENTS.md):\n"
+          <> agentsMd
+          <> factsSection
+
+  let model = selectModel task
+  let costBudget = selectCostByComplexity (TaskCore.taskComplexity task)
+
+  pure
+    <| Text.unlines
+      [ "=== AGENT CONFIGURATION ===",
+        "Model: " <> model,
+        "Cost budget: " <> tshow costBudget <> " cents",
+        "",
+        "=== SYSTEM PROMPT ===",
+        systemPrompt,
+        "",
+        "=== USER PROMPT (task details) ===",
+        formatTask task
+      ]