fix(review): inject the diff into the prompt instead of having the agent fetch it

scripts/pr-review/prompt.md

@@ -71,8 +71,10 @@ When you see code that smells like one of these, call it out as
 
 ## Method — do exactly this, in this order
 
-1. **Get the diff**: `gh pr diff ${PR_NUMBER} --patch`. Skim once
-   for shape (size, languages touched).
+1. **Read the diff** — it is pre-fetched and included at the END of
+   this prompt; no tool call is needed to get it. Skim once for shape
+   (size, languages touched). (If it was truncated for size, fetch the
+   rest yourself with `gh pr diff ${PR_NUMBER} --patch`.)
 
 2. **For each changed file** (cap at 25 if there are more — list the
    skipped in your output):
@@ -149,5 +151,6 @@ explicit recommendation: APPROVE / COMMENT / REQUEST_CHANGES.
 - **Cap your investigation**: ≤ 60 turns. If you hit the cap, dump
   what you have — partial reviews are still useful.
 
-Now start. Your first tool call should be `Bash: gh pr diff
-${PR_NUMBER} --patch`.
+Now start. The full diff is included at the end of this prompt — review
+it directly; use Read / Grep on the changed files for the deeper checks
+above. Your output must begin with `### Summary`.

scripts/pr-review/run_review.sh

@@ -35,6 +35,25 @@ BASE_REF="$(gh pr view "$PR_NUMBER" --json baseRefName --jq .baseRefName)"
 export PR_NUMBER HEAD_SHA BASE_REF
 envsubst < "$WORKDIR/prompt.md" > "$PROMPT"
 
+# Pre-fetch the diff and inject it into the prompt. The review must NOT depend
+# on the agent issuing its own `gh pr diff` tool call: some model backends emit
+# tool calls as plain text (`<tool_call>…`) instead of invoking them natively,
+# so the agent never actually receives the diff and produces an empty,
+# heading-less review that falls back to COMMENTED on every PR. Injecting the
+# diff up front makes the review backend-agnostic — the agent can review
+# directly, and Read/Grep stay available for deeper investigation when native
+# tool-calling does work. Appended (not via envsubst) because a diff can contain
+# `${…}` byte sequences envsubst would mangle; capped so a huge PR can't blow
+# the context window (the agent can fetch more itself when tool-calling works).
+{
+  echo
+  echo '## The diff under review (pre-fetched — review this directly)'
+  echo
+  echo '```diff'
+  gh pr diff "$PR_NUMBER" --patch 2>/dev/null | head -c 800000
+  echo '```'
+} >> "$PROMPT"
+
 # Source the harness adapter — it sources litellm-wait.sh and owns the gateway
 # pre-flight wait + the retry-on-gateway-down loop. The CLI is the consumer's
 # .agent-ops.json harness.kind (default: claude).