Omni/Agent/Subagent/Coder: improve token efficiency

- Rewrote system prompt with TOKEN EFFICIENCY section
- Reduced defaults: timeout 600s, maxCost 50¢, maxTokens 100k
- Added output truncation (8000 char cap) to all tools
- Tightened search limits (30 results, 5 context lines)

1 files changed, 27 insertions, 16 deletions

diff --git a/Omni/Agent/Subagent/Coder.hs b/Omni/Agent/Subagent/Coder.hs
index ad97ee7..63273f6 100644
--- a/Omni/Agent/Subagent/Coder.hs
+++ b/Omni/Agent/Subagent/Coder.hs
@@ -71,7 +71,7 @@ test =
     [ Test.unit "CoderConfig has sensible defaults" <| do
         let cfg = defaultCoderConfig "Omni/Task" "Implement feature X"
         coderNamespace cfg Test.@=? "Omni/Task"
-        coderTimeout cfg Test.@=? 1200,
+        coderTimeout cfg Test.@=? 600,
       Test.unit "coderSystemPrompt includes namespace" <| do
         let cfg = defaultCoderConfig "Biz/Cloud" "Fix the bug"
         let prompt = coderSystemPrompt cfg Nothing
@@ -131,11 +131,11 @@ defaultCoderConfig namespace task =
       coderTask = task,
       coderContext = Nothing,
       coderModel = "anthropic/claude-sonnet-4",
-      coderTimeout = 1200,
-      coderMaxCost = 200.0,
-      coderMaxTokens = 300000,
-      coderMaxIterations = 30,
-      coderMaxVerifyRetries = 3
+      coderTimeout = 600,
+      coderMaxCost = 50.0,
+      coderMaxTokens = 100000,
+      coderMaxIterations = 20,
+      coderMaxVerifyRetries = 2
     }
 
 -- | Run a bash command and capture output
@@ -265,7 +265,7 @@ loadCoderSystemPrompt cfg maybeInitState = do
 coderSystemPrompt :: CoderConfig -> Maybe Text -> Text
 coderSystemPrompt cfg maybeInitState =
   Text.unlines
-    [ "You are a specialized Coder subagent.",
+    [ "You are a specialized Coder subagent with a STRICT TOKEN BUDGET.",
       "",
       "## Your Task",
       coderTask cfg,
@@ -276,24 +276,35 @@ coderSystemPrompt cfg maybeInitState =
       "",
       maybe "" (\ctx -> "## Context\n" <> ctx <> "\n") (coderContext cfg),
       maybe "" (\st -> "## Current State\n" <> st <> "\n") maybeInitState,
+      "## TOKEN EFFICIENCY (CRITICAL)",
+      "",
+      "You have LIMITED tokens. Every tool output consumes budget. Violating these rules will cause task failure:",
+      "",
+      "1. NEVER read entire files. Use search_and_read or read_file with start_line/end_line",
+      "2. ALWAYS search first (search_codebase or search_and_read) to find exact locations",
+      "3. Use edit_file for changes - NEVER write_file unless creating new files",
+      "4. Limit bash output: pipe through `head -50` or `tail -50` when possible",
+      "5. One focused action per step - don't chain unnecessary operations",
+      "",
+      "## Tool Strategy",
+      "",
+      "To find code: search_and_read (returns matches + context in one call)",
+      "To understand a function: read_file with start_line/end_line (get just that function)",
+      "To edit: edit_file with old_str/new_str (surgical patch, not full file rewrite)",
+      "To explore structure: search_codebase with small max_results",
+      "",
       "## Guidelines",
       "1. Make incremental changes - edit one file at a time",
       "2. After each edit, consider running `lint " <> coderNamespace cfg <> ".hs` to catch issues early",
       "3. Use `bild " <> coderNamespace cfg <> "` to check your work compiles",
-      "4. If tests exist, run `bild --test " <> coderNamespace cfg <> "` to verify",
-      "5. Keep changes focused on the task - don't refactor unrelated code",
-      "6. If you find bugs unrelated to your task, note them but don't fix them",
+      "4. Keep changes focused on the task - don't refactor unrelated code",
       "",
       "## Completion",
-      "When you believe you're done:",
-      "1. Ensure all edits are complete",
-      "2. The harness will automatically run lint --fix, build, and tests",
-      "3. If verification fails, you'll be asked to fix the issues",
-      "4. Provide a brief summary of what you changed",
+      "When done: provide a brief summary. The harness runs lint --fix, build, and tests automatically.",
       "",
       "## Important",
       "- Do NOT commit - the harness handles git operations",
-      "- Focus on making the code changes correctly"
+      "- Do NOT read files you don't need to edit"
     ]
 
 -- | Format verify error for agent retry prompt