diff --git a/packages/workflows/src/executor-shared.test.ts b/packages/workflows/src/executor-shared.test.ts
index 84346f13..80915621 100644
--- a/packages/workflows/src/executor-shared.test.ts
+++ b/packages/workflows/src/executor-shared.test.ts
@@ -167,6 +167,50 @@ describe('substituteWorkflowVariables', () => {
     expect(prompt).toBe('Issue: context-data. External: context-data');
   });
 
+  it('does not treat context variables as prefixes of longer identifiers', () => {
+    const { prompt, contextSubstituted } = substituteWorkflowVariables(
+      'Context: $CONTEXT. File: $CONTEXT_FILE. External path: $EXTERNAL_CONTEXT_PATH. IssueId: $ISSUE_CONTEXT_ID',
+      'run-1',
+      'msg',
+      '/tmp',
+      'main',
+      'docs/',
+      'context-data'
+    );
+    expect(prompt).toBe(
+      'Context: context-data. File: $CONTEXT_FILE. External path: $EXTERNAL_CONTEXT_PATH. IssueId: $ISSUE_CONTEXT_ID'
+    );
+    expect(contextSubstituted).toBe(true);
+  });
+
+  it('does not substitute $ISSUE_CONTEXT when followed by identifier characters', () => {
+    const { prompt } = substituteWorkflowVariables(
+      'Issue: $ISSUE_CONTEXT. ID: $ISSUE_CONTEXT_ID. Type: $ISSUE_CONTEXT_TYPE',
+      'run-1',
+      'msg',
+      '/tmp',
+      'main',
+      'docs/',
+      'context-data'
+    );
+    expect(prompt).toBe('Issue: context-data. ID: $ISSUE_CONTEXT_ID. Type: $ISSUE_CONTEXT_TYPE');
+  });
+
+  it('does not set contextSubstituted when only suffix-extended context vars are present', () => {
+    const { prompt, contextSubstituted } = substituteWorkflowVariables(
+      'Path: $CONTEXT_FILE',
+      'run-1',
+      'msg',
+      '/tmp',
+      'main',
+      'docs/',
+      'context-data'
+    );
+    // $CONTEXT_FILE is not a context variable — should be left untouched
+    expect(prompt).toBe('Path: $CONTEXT_FILE');
+    expect(contextSubstituted).toBe(false);
+  });
+
   it('clears context variables when issueContext is undefined', () => {
     const { prompt, contextSubstituted } = substituteWorkflowVariables(
       'Context: $CONTEXT here',
diff --git a/packages/workflows/src/executor-shared.ts b/packages/workflows/src/executor-shared.ts
index e1978ae1..255895a5 100644
--- a/packages/workflows/src/executor-shared.ts
+++ b/packages/workflows/src/executor-shared.ts
@@ -242,7 +242,8 @@ export async function loadCommandPrompt(
 // ─── Variable Substitution ───────────────────────────────────────────────────
 
 /** Pattern string for context variables - used to create fresh regex instances */
-export const CONTEXT_VAR_PATTERN_STR = '\\$(?:CONTEXT|EXTERNAL_CONTEXT|ISSUE_CONTEXT)';
+export const CONTEXT_VAR_PATTERN_STR =
+  '\\$(?:CONTEXT|EXTERNAL_CONTEXT|ISSUE_CONTEXT)(?![A-Za-z0-9_])';
 
 /**
  * Substitute workflow variables in a prompt.